Patent Application
20240195025
The present application claims priority to Korean Patent Application No. 10-2021-0142189, filed on Oct. 22, 2021, in the Republic of Korea, the disclosures of which is incorporated herein by reference.
The present disclosure relates to a cylindrical battery, and a battery pack and a vehicle including the cylindrical battery.
In the case of manufacturing a battery pack using a cylindrical battery, typically, a plurality of cylindrical batteries are placed upright in a housing, and the upper and lower ends of the cylindrical batteries are used as positive electrode terminals and negative electrode terminals, respectively, so that the plurality of cylindrical batteries are electrically connected to each other.
In the electrical connection of the cylindrical batteries, a negative electrode uncoated portion of the electrode assembly accommodated inside the battery housing extends downward and is electrically connected to the bottom surface of the battery housing, and a positive electrode uncoated portion extends upward and is electrically connected to the top cap. That is, in the cylindrical battery, it is common that the bottom surface of the battery housing is used as a negative electrode terminal, and the top cap covering the top opening of the battery housing is used as a positive electrode terminal.
When the positive electrode terminal and the negative electrode terminal of the cylindrical battery are located on opposite sides, electrical connecting parts such as a bus bar for electrically connecting the plurality of cylindrical batteries must be applied to both the upper and lower portions of the cylindrical battery. This complicates the electrical connection structure of the battery pack.
Moreover, in such a structure, parts for insulation and parts for securing waterproofness or sealing must be separately applied to the upper and lower portions of the battery pack, so the number of applied parts increases and the structure becomes complicated.
Therefore, it is required to develop a cylindrical battery having a structure in which a positive electrode terminal and a negative electrode terminal are applied in the same direction to simplify the electrical connection structure of a plurality of cylindrical batteries.
Meanwhile, secondary batteries that are easily applicable to various product groups, allow repeated charging and discharging, and have electrical characteristics such as high energy density are universally applied not only to portable devices but also to electric vehicles (EVs) or hybrid electric vehicles (HEVs) driven by an electric drive source. Hereinafter, the battery will refer to a secondary battery.
These batteries are attracting attention as a new energy source to improve eco-friendliness and energy efficiency because they have the primary advantage that they can dramatically reduce the use of fossil fuels as well as the secondary advantage that no by-products are generated from the use of energy.
Batteries currently widely used in the art include lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, and the like, and a unit secondary battery has an operating voltage of about 2.5V to 4.5V. Therefore, when a higher output voltage is required, a battery pack may be configured by connecting a plurality of batteries in series. In addition, a plurality of batteries may be connected in parallel to form a battery pack according to the charge/discharge capacity required for the battery pack. Accordingly, the number of batteries included in the battery pack and the form of electrical connection may be variously set according to the required output voltage and/or charge/discharge capacity.
Meanwhile, as a kind of unit battery, there are known cylindrical, rectangular, and pouch-type batteries. In the case of a cylindrical battery, a separator serving as an insulator is interposed between a positive electrode and a negative electrode, and they are wound to form an electrode assembly in the form of a jelly roll, which is inserted into a battery housing to configure a battery. In addition, a strip-shaped electrode tab may be connected to an uncoated portion of each of the positive electrode and the negative electrode, and the electrode tab electrically connects the electrode assembly and an electrode terminal exposed to the outside. For reference, the positive electrode terminal is a cap plate of a sealing body that seals the opening of the battery housing, and the negative electrode terminal is the battery housing.
However, according to the conventional cylindrical battery having such a structure, since current is concentrated in the strip-shaped electrode tab coupled to the uncoated portion of the positive electrode and/or the uncoated portion of the negative electrode, the current collection efficiency is not good due to large resistance and large heat generation.
For small cylindrical batteries with a form factor of 1865 or 2170, resistance and heat are not a major issue. However, when the form factor is increased to apply the cylindrical battery to an electric vehicle, the cylindrical battery may ignite while a lot of heat is generated around the electrode tab during the rapid charging process.
In order to solve this problem, there is provided a cylindrical battery (so-called tab-less cylindrical battery) in which the uncoated portion of the positive electrode and the uncoated portion of the negative electrode are designed to be positioned at the top and bottom of the jelly-roll type electrode assembly, respectively, and the current collecting plate is welded to the uncoated portion to improve the current collecting efficiency.
Referring to
An electrode assembly A is manufactured by sequentially stacking the positive electrode 10 and the negative electrode 11 together with two sheets of separators 12 as shown in
After the winding process, the uncoated portion 10a of the positive electrode 10 and the uncoated portion 11a of the negative electrode 11 are bent toward the core. After that, current collecting plates 30, 31 are welded and coupled to the uncoated portions 10a, 11a, respectively.
An electrode tab is not separately coupled to the positive electrode uncoated portion 10a and the negative electrode uncoated portion 11a, the current collecting plates 30, 31 are connected to external electrode terminals, and a current path is formed with a large cross-sectional area along the winding axis direction of electrode assembly A (see arrow), which has an advantage of lowering the resistance of the battery. This is because resistance is inversely proportional to the cross-sectional area of the path through which the current flows.
In the tab-less cylindrical battery, in order to improve the welding characteristics of the uncoated portions 10a and 11a and the current collecting plates 30 and 31, it is necessary to bend the uncoated portions 10a and 11a as flat as possible by applying a strong pressure to the welding points of the uncoated portions 10a and 11a.
However, when the welding points of the uncoated portions 10a and 11a are bent, the shapes of the uncoated portions 10a and 11a may be irregularly distorted and deformed. In this case, the deformed portion may contact an electrode of opposite polarity to cause an internal short circuit or cause fine cracks in the uncoated portions 10a and 11a. In addition, as the uncoated portion 32 adjacent to the core of the electrode assembly A is bent, all or a significant portion of the cavity 33 in the core of the electrode assembly A is blocked. In this case, a problem arises in the electrolyte injection process. That is, the cavity 33 in the core of the electrode assembly A is used as a passage through which electrolyte is injected. However, when the corresponding passage is blocked, it is difficult to inject the electrolyte. In addition, while an electrolyte injector is being inserted into the cavity 33, interference with the uncoated portion 32 near the core may occur to cause the uncoated portion 32 to be torn.
In addition, the bent portions of the uncoated portions 10a and 11a to which the current collecting plates 30 and 31 are welded must be overlapped in several layers and no empty space (gap) must exist. In this way, a sufficient welding strength can be obtained, and even if the latest technology such as laser welding is used, the problem that laser penetrates into the electrode assembly A and melts the separator or the active material can be prevented.
Meanwhile, in the conventional tab-less cylindrical battery, the positive electrode uncoated portion 10a is formed on the electrode assembly A as a whole. Therefore, when the beading portion is formed by pressing the outer circumference of the top of the battery housing inward, the top edge region 34 of the electrode assembly A is pressed by the battery housing. Such pressure may cause partial deformation of the electrode assembly A, and at this time, an internal short circuit may occur as the separator 12 is torn. If a short circuit occurs inside the battery, the battery may be heated or explode.
On the other hand, by applying a conventional positive electrode active material containing secondary particles, particle breakage may occur during electrode manufacturing, and the amount of gas generated due to internal cracking during charging and discharging may increase, which may cause problems with battery stability.
To solve this problem, a positive electrode active material in the form of a single particle or pseudo-single particle having a relatively large primary particle size has been developed. However, if the positive electrode active material in the form of a single particle or pseudo-single particle is applied to a high loading electrode and then rolling is performed, there is a problem in that the electrode is broken in a state where the electrode porosity is not achieved to a target level, and there is a problem in that the resistance characteristics and charge/discharge efficiency of the lithium secondary battery are not good.
The present disclosure is designed in consideration of the above problems, and therefore the present disclosure is directed to providing a cylindrical battery having a structure in which a positive electrode terminal and a negative electrode terminal are applied in the same direction.
The present disclosure is also directed to securing a sufficient area for welding an electric connection component such as a bus bar with an electrode terminal of a cylindrical battery while manufacturing a battery pack, in a case where a plurality of cylindrical batteries are to be electrically connected in one direction.
The present disclosure is also directed to providing an electrode assembly having an improved uncoated portion structure to relieve a stress applied to the uncoated portion when bending the uncoated portion exposed at both ends of the electrode assembly.
The present disclosure is also directed to providing an electrode assembly in which an electrolyte injection passage is not blocked even when the uncoated portion is bent.
The present disclosure is also directed to providing an electrode assembly having a structure capable of preventing contact between the top edge of the electrode assembly and the inner surface of the battery housing when the top of the battery housing is beaded.
The present disclosure is also directed to providing an electrode assembly with improved energy density and reduced resistance.
The present disclosure is also directed to providing a cylindrical battery including the electrode assembly of an improved structure, a battery pack including the cylindrical battery, and a vehicle including the battery pack.
The present disclosure is also directed to providing an electrode and an electrode assembly including the same, which may implement excellent thermal stability ad have high electrical conductivity and high rolling characteristics by applying a single particle or pseudo-single particle as a positive electrode active material.
The present disclosure is also directed to providing an electrode assembly with improved energy density by including a silicon-containing negative electrode active material in the negative electrode.
The present disclosure is also directed to providing an electrode assembly in which the range of the positive electrode active material portion is increased without worrying about lithium precipitation.
The present disclosure is also directed to providing a cylindrical battery capable of exhibiting excellent thermal stability even when the volume of the battery increases due to an increase in form factor.
However, the technical object to be solved by the present disclosure is not limited to the above, and other objects not mentioned herein will be clearly understood by those skilled in the art from the following disclosure.
In one aspect of the present disclosure, there is provided a cylindrical battery, comprising an electrode assembly in which a first electrode, a second electrode, and a separator interposed therebetween are wound around a winding axis in a winding direction to define a core and an outer circumference of the electrode assembly.
The first electrode and the second electrode may respectively include a first coated portion and a second coated portion coated with an active material layer along the winding direction.
The first electrode and the second electrode may respectively include a first uncoated portion and a second uncoated portion not coated with an active material layer along the winding direction.
At least one of the first uncoated portion and the second uncoated portion is defined as an electrode tab by itself, and includes a core-side uncoated portion, an outer circumference uncoated portion, and an intermediate uncoated portion interposed therebetween.
At least one of the core-side uncoated portion and the outer circumference uncoated portion has a relatively smaller height than the intermediate uncoated portion in a winding axis direction.
The cylindrical battery includes a battery housing configured to accommodate the electrode assembly through an opening and electrically connected to the second uncoated portion; an external terminal electrically connected to the first uncoated portion and exposed to the outside of the battery housing through a closed portion of the battery housing located opposite to the opening; and a cap plate configured to cover the opening of the battery housing.
The cap plate may be insulated from the battery housing and not electrically connected to the electrode assembly to have no polarity.
The external terminal may be electrically connected to the first uncoated portion having a first polarity.
The battery housing may be electrically connected to the second uncoated portion having a second polarity different from the first polarity.
The external terminal may located at a center of the closed portion of the battery housing.
The external terminal may include a terminal exposing portion extending to an outer side of the battery housing; and a terminal insert portion configured to extend through the closed portion of the battery housing.
A cross section of the terminal exposing portion may be larger than a cross section of the terminal insert portion, and an edge of a bottom of the terminal insert portion facing the electrode assembly may be riveted toward an inner surface of the closed portion.
The cylindrical battery may further comprise an insulating gasket interposed between the battery housing and the external terminal to insulate the external terminal and the battery housing.
The insulating gasket may include a gasket exposing portion extending to an outer side of the battery housing; and a gasket insert portion configured to pass through the closed portion of the battery housing.
A part of the insulating gasket interposed between the edge of the bottom of the terminal insert portion and the battery housing may be in close contact with the inner surface of the closed portion by the riveting.
The cylindrical battery may further comprise a beading portion located adjacent to the opening of the battery housing; a crimping portion extending inward at the opening to surround an edge of the cap plate; and a sealing gasket compressed by the crimping portion in a state of being interposed between the opening of the battery housing and the cap plate to isolate the cap plate and the opening of the battery housing from each other.
At least a partial region of the intermediate uncoated portion may include a plurality of segments that are independently bendable.
At least one of height in the winding axis direction and width in the winding direction of the plurality of segments may increase stepwise from the core toward the outer circumference individually or by group.
The plurality of segments may form a plurality of segment groups from the core toward the outer circumference, and the segments belonging to the same segment group may be identical in terms of at least one of width in the winding direction, height in the winding axis direction, and separation pitch in the winding direction.
The segments belonging to the same segment group may gradually increase in terms of at least one of the width in the winding direction, the height in the winding axis direction, and the separation pitch in the winding direction from the core toward the outer circumference.
The plurality of segments may be bent toward the core and overlapped in several layers along the winding axis direction.
A radial length (R) of the core-side uncoated portion and a bending length (H) of an innermost segment of the intermediate uncoated portion may satisfy the relation H≤R.
A gap may be provided between a bottom of a cutting line of the segment and the active material layer.
The first uncoated portion may be defined as the electrode tab by itself, the first uncoated portion may include the core-side uncoated portion adjacent to the core of the electrode assembly, the outer circumference uncoated portion adjacent to the outer circumference of the electrode assembly, and the intermediate uncoated portion interposed between the core-side uncoated portion and the outer circumference uncoated portion, the intermediate uncoated portion of the first uncoated portion may include a plurality of segments that are independently bendable, and the plurality of segments of the first uncoated portion may be bent toward the core to define a bent surface of the segments at one end of the electrode assembly.
The cylindrical battery may further comprise a first current collecting plate coupled to the bent surface of the segments of the first uncoated portion; and an insulator interposed between the first current collecting plate and an inner surface of the closed portion. In this case, an end of the external terminal facing the electrode assembly may be coupled to the first current collecting plate through the insulator.
The second uncoated portion may be defined as the electrode tab by itself, the second uncoated portion may include the core-side uncoated portion adjacent to the core of the electrode assembly, the outer circumference uncoated portion adjacent to the outer circumference of the electrode assembly, and the intermediate uncoated portion interposed between the core-side uncoated portion and the outer circumference uncoated portion, the intermediate uncoated portion of the second uncoated portion may include a plurality of segments that are independently bendable, and the plurality of segments of the second uncoated portion may be bent toward the core to define a bent surface of the segments at one end of the electrode assembly.
The cylindrical battery may further comprise a second current collecting plate coupled to the bent surface of the segments of the second uncoated portion. In this case, at least a part of an edge of the second current collecting plate may extend toward an inner surface of the beading portion and be interposed and fixed between the inner surface of the beading portion and the sealing gasket.
The cap plate may include a venting portion formed to have a smaller thickness than an adjacent area of the cap plate. The venting portion may be a notching pattern. The venting portion may be formed in a continuous or discontinuous straight line pattern or curved pattern.
When the cylindrical battery is erected so that the cap plate faces the ground, a bottom of the cap plate may be located higher than a bottom of the battery housing.
A first sliding portion in which a thickness of the active material layer is reduced may be included in a boundary region between the first coated portion and the first uncoated portion of the first electrode, a second sliding portion in which a thickness of the active material layer is reduced may be included in a boundary region between the second coated portion and the second uncoated portion of the second electrode, the first sliding portion and the second sliding portion may be located in opposite directions along the winding axis.
The coated portion of the first electrode may include a loading reduction portion in which a loading amount of the active material is reduced, and the position of the loading reduction portion may correspond to the position of the second sliding portion.
The active material layer of the first electrode may include a positive electrode active material including a single particle, a pseudo-single particle, or a combination thereof.
Dmin, which is a minimum particle size in a cumulative volume distribution of the positive electrode active material, may be 1.0 μm or more.
In the cumulative volume distribution of the positive electrode active material, D50, which is a particle size when a cumulative volume amount is 50%, may be 5.0 μm or less.
Dmax, which is a maximum particle size in the cumulative volume distribution of the positive electrode active material, may be 12 μm to 17 μm.
The positive electrode active material may have a unimodal particle size distribution showing a single peak in a cumulative volume particle size distribution graph, and a particle size distribution (PSD) represented by the following formula is 3 or less:
PSD=(Dmax−Dmin)/D50. Formula:
The single particle, the pseudo-single particle, or the combination thereof may be present in an amount of 95 wt % to 100 wt % based on a total weight of the positive electrode active material present in the active material layer of the first electrode.
The positive electrode active material may include a lithium nickel-containing oxide comprising 80 mol % or more of Ni based on the total number of moles of a transition metal.
The active material layer of the first electrode may have a porosity of 15% to 23%. The active material layer of the first electrode may comprise flake graphite in a weight ratio of 0.05 wt % to 5 wt %.
The active material layer of the first electrode may further comprise carbon nanotubes.
The active material layer of the second electrode may include a silicon-containing negative electrode active material and a carbon-containing negative electrode active material.
The silicon-containing negative electrode active material and the carbon-containing negative electrode active material may be present in the active material layer of the second electrode in a weight ratio of 1:99 to 20:80.
In another aspect of the present disclosure, there is also provided a battery pack, comprising a plurality of cylindrical batteries having at least one of the above features, and a pack housing configured to accommodate the plurality of cylindrical batteries.
In another aspect of the present disclosure, there is also provided a vehicle, comprising the battery pack.
According to one aspect of the present disclosure, a cylindrical battery having a structure in which a positive electrode terminal and a negative electrode terminal are applied in the same direction is provided, and thus an electrical connection structure of a plurality of cylindrical batteries can be simplified.
According to another aspect of the present disclosure, since the electrode terminal of the cylindrical battery has a sufficient area to be welded with electrical connecting parts such as bus bars, sufficient bonding strength may be secured between the electrode terminal and the electrical connecting parts, and the resistance at the bonding portion between the electrical connection parts and the electrode terminal can be lowered to a desirable level.
According to still another aspect of the present disclosure, the internal resistance of the battery may be reduced and the energy density may be increased by using the uncoated portions themselves protruding from the upper and lower portions of the electrode assembly as electrode tabs.
According to still another aspect of the present disclosure, by improving the structure of the uncoated portion of the electrode assembly to prevent interference between the electrode assembly and the inner circumference of the battery housing in the process of forming a beading portion of the battery housing, it is possible to prevent an internal short circuit from occurring in the cylindrical battery due to partial deformation of the electrode assembly.
According to still another aspect of the present disclosure, by improving the structure of the uncoated portion of the electrode assembly, it is possible to prevent the uncoated portion from being torn when the uncoated portion is bent, and it is possible to improve the welding strength by sufficiently increasing the number of overlapping layers of the uncoated portion.
According to still another aspect of the present disclosure, by improving the structure of the uncoated portion adjacent to the core of the electrode assembly, it is possible to prevent the cavity in the core of the electrode assembly from being blocked when the uncoated portion is bent, thereby allowing the electrolyte injection process and the process of welding the battery housing and the current collecting plate to be easily performed.
According to still another aspect of the present disclosure, it is possible to provide a cylindrical battery having a structure with low internal resistance, prevention of internal short circuit, and improved welding strength between the current collecting plate and the uncoated portion, and a battery pack and a vehicle including the same.
According to still another aspect of the present disclosure, since the positive electrode includes positive electrode active material powder having Dmin of 1.0 μm or more, thermal safety of the battery may be further improved. According to the study by inventors of the present discloser, even if a single particle and/or pseudo-single particle is applied as the positive electrode active material, the effect of suppressing particle breakage and improving thermal safety after rolling is different depending on the particle size of the positive electrode active material powder. In particular, when particles with a particle diameter of less than 1.0 μm are included in the positive electrode active material powder, the line pressure increases during the rolling process, resulting in increased particle breakage and reduced thermal stability, so it is impossible to sufficiently secure thermal stability when applying a large-sized cylindrical battery. Therefore, in the present disclosure, the effect of improving thermal safety can be maximized by using a positive electrode active material powder having a minimum particle size (Dmin) controlled to 1.0 μm or more.
According to still another aspect of the present disclosure, since the positive electrode contains a positive electrode active material powder whose D50, Dmax, and particle size distribution (PSD) are appropriately adjusted so as to minimize the increase in resistance due to single particle application, it is possible to implement excellent capacity characteristics and power characteristics.
According to still another aspect of the present disclosure, the conductivity of the electrode can be improved by including a single particle-based positive electrode active material coated with a conductive coating layer or by containing novel CNT as a conductive material.
According to still another aspect of the present disclosure, since the positive electrode active material layer contains flake graphite, when the positive electrode active material layer is rolled, the flake graphite provides a sliding effect to the positive electrode active material, so that the rolling properties of the electrode are improved, and the electrode porosity can be lowered to the target level. Accordingly, stability, initial resistance characteristics, and charge/discharge efficiency of the cylindrical battery are improved.
According to still another aspect of the present disclosure, a higher energy density can be implemented by including a silicon-containing negative electrode active material with a large capacity in the negative electrode.
According to still another aspect of the present disclosure, since a loading reduction portion with a small loading amount of the positive electrode active material is included in the positive electrode, the range of the positive electrode active material portion can be increased without worrying about lithium precipitation.
According to still another aspect of the present disclosure, compared to a conventional battery having a strip-shaped electrode tab, internal heat generation of the battery can be effectively reduced, so the thermal safety of the battery can be improved.
In addition, the present disclosure may have various other effects, which will be described in each embodiment, or effects that can be easily inferred by those skilled in the art will not be described.
The accompanying drawings illustrate a preferred embodiment of the present disclosure and together with the foregoing disclosure, serve to provide further understanding of the technical features of the present disclosure, and thus, the present disclosure is not construed as being limited to the drawing.
Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Prior to the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the disclosure, so it should be understood that other equivalents and modifications could be made thereto without departing from the scope of the disclosure.
In addition, in order to help the understanding of the present disclosure, the accompanying drawings are not drawn to scale, but dimensions of some components may be exaggerated. Also, the same reference signs may be assigned to the same components in different embodiments.
Since the size and thickness of each component shown in the drawings are arbitrarily illustrated for convenience of description, the present disclosure is not necessarily limited to the drawings. In the drawings, the thickness is shown enlarged to clearly express the various layers and regions. In addition, in the drawings, for convenience of explanation, the thicknesses of some layers and regions are exaggerated.
In addition, when a part such as a layer, film, region, plate, etc. is described to be “above” or “on” another part, this includes not only the case where it is “directly on” another part, but also the case where still another part exists therebetween. Conversely, when a part is described to be “directly on” another part, it means that there is no other part therebetween.
In addition, to be “above” or “on” a reference part means to be located above or below the reference part, and does not mean to be located “above” or “on” in a direction opposite to gravity.
In addition, throughout the specification, when a certain part is described to “include” a certain component, it means that it may further include other components without excluding other components, unless otherwise stated.
In addition, throughout the specification, when it is referred to as “in a planar form”, it means when the target part is viewed from above, and when it is referred to as “in a cross-sectional form”, it means when the target part is vertically cut and viewed from the side.
Referring to
The cylindrical battery 1 may further include an insulating gasket 35 and/or a first current collecting plate 36 and/or an insulator 37 and/or a second current collecting plate 38 and/or a sealing gasket 39 in addition to the above-described components.
The electrode assembly A includes a first electrode having a first polarity, a second electrode having a second polarity, and a separator interposed between the first electrode and the second electrode. The first electrode is a positive electrode or a negative electrode, and the second electrode corresponds to an electrode having polarity opposite to that of the first electrode.
The electrode assembly A may have, for example, a jelly-roll shape. That is, the electrode assembly A may be manufactured by winding a stack, which is formed by sequentially stacking the first electrode, the separator and the second electrode at least once, based on a winding center C. In this case, an additional separator may be provided on the outer circumference of the electrode assembly A to insulate the electrode assembly from the battery housing BH.
The first electrode includes a first electrode current collector and a first electrode active material coated on one surface or both surfaces of the first electrode current collector. At one end in the width direction (direction parallel to the Z-axis) of the first electrode current collector, there is an uncoated portion of the first electrode (first uncoated portion) on which the first electrode active material is not coated. The first uncoated portion serves as a first electrode tab 13. The first electrode tab 13 is provided to an upper portion in the height direction (direction parallel to the Z-axis) of the electrode assembly A accommodated in the battery housing BH.
The second electrode includes a second electrode current collector and a second electrode active material coated on one surface or both surfaces of the second electrode current collector. At the other end in the width direction (direction parallel to the Z-axis) of the second electrode current collector, there is an uncoated portion of the second electrode (second uncoated portion) on which the second electrode active material is not coated. The second uncoated portion serves as a second electrode tab 14. The second electrode tab 14 is provided to a lower portion in the height direction (direction parallel to the Z-axis) of the electrode assembly A accommodated in the battery housing BH.
The first electrode tab 13 and the second electrode tab 14 extend and protrude in opposite directions along the width direction of the electrode assembly A, that is, along the height direction (direction parallel to the Z-axis) of the cylindrical battery 1.
Referring to
The battery housing BH is electrically connected to the electrode assembly A. The battery housing BH is electrically connected to the second electrode tab 14 of the electrode assembly A, for example. In this case, the battery housing BH has the same polarity as the second electrode tab 14.
Referring to
The crimping portion 24 is formed below the beading portion 23. The crimping portion 24 has an extended and bent shape to surround the outer circumference of the cap plate 40 disposed below the beading portion 23 and a part of the lower surface of the cap plate 40.
However, the present disclosure does not exclude the case where the battery housing BH does not include the beading portion 23 and/or the crimping portion 24. In the present disclosure, when the battery housing BH does not include the beading portion 23 and/or the crimping portion 24, the electrode assembly A may be fixed and/or the cap plate 40 may be fixed and/or the battery housing BH may be sealed by, for example, additionally applying a part that can function as a stopper for the electrode assembly A and/or additionally applying a structure on which the cap plate 40 can be seated and/or welding the battery housing BH and the cap plate 40 to each other.
Referring to
When the battery housing BH of the present disclosure includes the beading portion 23, the cap plate 40 may be seated on the beading portion 23 formed in the battery housing BH. In addition, when the battery housing BH of the present disclosure includes the crimping portion 24, the cap plate 40 is fixed by the crimping portion 24. A sealing gasket 39 may be interposed between the cap plate 40 and the crimping portion 24 of the battery housing BH to ensure airtightness of the battery housing BH. Meanwhile, as described above, the battery housing BH of the present disclosure may not have the beading portion 23 and/or the crimping portion 24, and in this case, the sealing gasket 39 may be interposed between a fixing structure provided at the opening side of the battery housing BH to secure airtightness and the cap plate 40.
Referring to
The cylindrical battery 1 according to an embodiment of the present disclosure has a structure in which both the positive electrode terminal and the negative electrode terminal exist on the upper portion, as will be described later, and as a result, the structure of the upper portion is more complicated than the structure of the lower portion. Accordingly, the venting portion 41 may be formed on the cap plate 40 forming the lower surface of the cylindrical battery 1 to smoothly discharge gas generated inside the battery housing BH.
As shown in
Meanwhile, when the venting portion 41 has a closed loop shape as shown in
Referring to
The external terminal 50 includes a terminal exposing portion 50a and a terminal insert portion 50b. The terminal exposing portion 50a is exposed to the outside of the battery housing BH. The terminal exposing portion 50a may be positioned approximately at the center of the upper surface of the battery housing BH. The maximum width of the terminal exposing portion 50a may be greater than the maximum width of the hole of the battery housing BH through which the external terminal 50 passes. The terminal insert portion 50b may be electrically connected to the first electrode tab 13 by passing through a substantially central portion of the upper surface of the battery housing BH. A peripheral edge area of the bottom of the terminal insert portion 50b may be riveted to the inner surface of the battery housing BH. That is, the peripheral edge area of the bottom of the terminal insert portion 50b may have a shape curved toward the inner surface of the battery housing BH, and thus the maximum width of the bottom of the terminal insert portion 50b may be larger than the maximum width of the hole of the battery housing BH through which the terminal insert portion 50b passes.
Meanwhile, when the cylindrical battery 1 of the present disclosure includes the first current collecting plate 36, the central area of the bottom of the terminal insert portion 50b may be coupled with the first current collecting plate 36. The central area of the bottom of the terminal insert portion 50b may have, for example, a substantially cylindrical shape. The diameter of the bottom surface of the central region of the bottom of the terminal insert portion 50b may be set to approximately 6.2 mm.
The coupling between the bottom surface of the central area of the bottom of the terminal insert portion 50b and the first current collecting plate 36 may be performed by, for example, laser welding or ultrasonic welding.
The laser welding may be performed by irradiating a laser through a hole formed in the winding center C of the electrode assembly A to form a laser welding line on one surface of the first current collecting plate 36. The laser welding line may be formed in a substantially concentric circle shape on the opposite side of the upper and lower surfaces of the first current collecting plate 36 that does not contact the bottom surface of the central area of the bottom of the terminal insert portion 50b. The welding line may be formed continuously or partially discontinuously.
The concentric welding line may have a diameter of approximately 60% to 80% of the diameter of the bottom surface of the central area of the bottom of the terminal insert portion 50b. For example, when the diameter of the bottom surface of the central area of the bottom of the terminal insert portion 50b is approximately 6.2 mm, the diameter of the circle drawn by the welding line may preferably be approximately 4.0 mm or more. If the diameter of the circle drawn by the welding line is too small, the coupling force by welding may be insufficient. Conversely, if the diameter of the circle drawn by the welding line is too large, the risk of damage to the electrode assembly A due to heat and/or welding spatter may increase.
The ultrasonic welding may be performed by inserting a welding rod for ultrasonic welding through the hole formed in the winding center C of the electrode assembly A. The welding portion formed by the ultrasonic welding is formed at the contact interface between the bottom surface of the central area of the bottom of the terminal insert portion 50b and the first current collecting plate 36. The welding portion formed by the ultrasonic welding may be entirely formed within a concentric circle having a diameter of approximately 30% to 80% of the diameter of the bottom surface of the central area of the bottom of the terminal insert portion 50b. For example, in the case where the bottom surface of the central area of the bottom of the terminal insert portion 50b has a diameter of about 6.2 mm, the diameter of the circle drawn by the ultrasonic welding portion may be about 2.0 mm or more. If the diameter of the circle drawn by the ultrasonic welding is too small, the coupling force by welding may be insufficient. Conversely, if the diameter of the circle drawn by the ultrasonic welding portion is too large, the risk of damage to the electrode assembly A due to heat and/or vibration may increase.
In an embodiment of the present disclosure, the upper surface of the battery housing BH and the external terminal 50 exposed to the outside of the battery housing BH have polarities opposite to each other and face in the same direction. In addition, a step may be formed between the external terminal 50 and the upper surface of the battery housing BH. Specifically, when the entire upper surface of the battery housing BH has a flat shape or a shape protruding upward from the center thereof, the terminal exposing portion 50a of the external terminal 50 may protrude upward more than the upper surface of the battery housing BH. Conversely, when the upper surface of the battery housing BH has a shape concavely recessed downward, that is, in a direction toward the electrode assembly A from the center, the upper surface of the battery housing BH may protrude upward higher than the terminal exposing portion 50a of the external terminal 50.
Meanwhile, in the case where the upper surface of the battery housing BH has a shape concavely recessed downward, that is, in a direction toward the electrode assembly A from the center, the upper surface of the battery housing BH and the upper surface of the terminal exposing portion 50a may form the same plane according to the recessed depth and the thickness of the terminal exposing portion 50a of the external terminal 50. In this case, a step may not be formed between the upper surface of the battery housing BH and the terminal exposing portion 50a.
The insulating gasket 35 is interposed between the battery housing BH and the external terminal 50 to prevent contact between the battery housing BH and the external terminal 50 having opposite polarities. As a result, the upper surface of the battery housing BH having a substantially flat shape may function as the second electrode terminal E2 of the cylindrical battery 1.
The insulating gasket 35 includes a gasket exposing portion 35a and a gasket insert portion 35b. The gasket exposing portion 35a is interposed between the terminal exposing portion 50a of the external terminal 50 and the battery housing BH. The gasket insert portion 35b is interposed between the terminal insert portion 50b of the external terminal 50 and the battery housing BH. When the terminal insert portion 50b is riveted, the gasket insert portion 35b may be deformed together to come into close contact with the inner surface of the battery housing BH. The insulating gasket 35 may be made of, for example, an insulating resin material.
Referring to
When the insulating gasket 35 is made of a resin material, the insulating gasket 35 may be coupled to the battery housing BH and the external terminal 50 by thermal fusion. In this case, airtightness may be enhanced at a coupling interface between the insulating gasket 35 and the external terminal 50 and at a coupling interface between the insulating gasket 35 and the battery housing BH. Meanwhile, when the gasket exposing portion 35a of the insulating gasket 35 has a shape extending to the upper surface of the terminal exposing portion 50a, the external terminal 50 may be coupled with the insulating gasket 35 by insert injection molding.
According to an embodiment of the present disclosure, the insulating gasket 35, the insulator 37 and the sealing gasket 39 may be formed of the same material. However, this is not essential. The insulating gasket 35 and the insulator 37 may have the same thickness. However, this is not essential. If they have different thicknesses, the insulator 37 may be thinner than the insulating gasket 35, or vice versa.
The entire area of the upper surface of the battery housing BH other than the area occupied by the external terminal 50 and the insulating gasket 35 corresponds to the second electrode terminal E2 having a polarity opposite to that of the external terminal 50. In contrast, in the present disclosure, when the insulating gasket 35 is omitted and the external terminal 50 is partially provided with an insulating coating layer, the entire area of the upper surface of the battery housing BH other than the area occupied by the external terminal 50 having an insulating coating layer may function as the second electrode terminal E2.
The cylindrical sidewall of the battery housing BH may be formed as one piece with the second electrode terminal E2 so that there is no discontinuous portion between the cylindrical sidewall and the second electrode terminal E2. The connection from the sidewall of the battery housing BH to the second electrode terminal E2 may be a smooth curve. However, the present disclosure is not limited thereto, and the connection portion may include at least one corner having a predetermined angle.
Referring to
Referring to
Referring to
Referring to
When the cylindrical battery 1 according to an embodiment of the present disclosure includes an insulator 37, the terminal insert portion 50b of the external terminal 50 passes through the insulator 37 and is coupled to the first current collecting plate 36 or the first electrode tab 13.
The insulator 37 may have an opening adjacent to the winding center C. The opening allows the terminal insert portion 50b of the external terminal 50 to directly contact the first current collecting plate 36.
In an embodiment of the present disclosure, the terminal insert portion 50b may have a circular planar shape, but is not limited thereto. The terminal insert portion 50b may optionally have a polygonal shape, a star shape, a shape having a leg extending from the center, or the like.
Referring to
Although not shown in the drawings, the second current collecting plate 38 may include a plurality of irregularities radially formed on one surface thereof. When the irregularities are formed, the second current collecting plate 38 may be pressed so that the irregularities are press-fitted into the second electrode tab 14.
Referring to
Referring to
Referring to
The outer end 38b of each sub plate 38a may be bent toward the inner surface of the beading portion 23, and an end portion thereof may be fixed while interposed between the sealing gasket 39 and the inner surface of the beading portion 23. Also, the end portion of the outer end 38b may be welded to an inner surface of the beading portion 23, for example, a lower surface. Through welding, the battery housing BH and the second electrode tab 14 may be electrically connected to each other. Since the sealing gasket 39 is interposed in the welding area between the cap plate 40 and the outer end 38b, the cap plate 40 may not have electrical polarity.
When the second current collecting plate 38 includes a plurality of sub plates 38a spaced apart from each other, the second current collecting plate 38 partially covers the lower surface of the electrode assembly A. Accordingly, a sufficient space is secured for the gas generated in the electrode assembly A to move toward the cap plate 40, and downward gas venting may be smoothly performed in the cylindrical battery 1. Meanwhile, as described above, the structure of the second current collecting plate 38 including the plurality of sub plates 38a may be equally applied to the first current collecting plate 36 described above.
Referring to
In addition, the cylindrical battery 1 has a structure in which one surface of the battery housing BH having a substantially flat shape may be used as the second electrode terminal E2, so that it is possible to secure a sufficient bonding area for bonding electrical connecting parts such as bus bars to the second electrode terminal E2. Accordingly, in the cylindrical battery 1, sufficient bonding strength between the electrical connection parts and the second electrode terminal E2 may be secured, and resistance at the bonding portion may be reduced to a desirable level.
Referring to
Preferably, the cylindrical battery may be, for example, a battery whose form factor ratio (defined as a value obtained by dividing the diameter of the battery by height, namely a ratio of height (H) to diameter (Φ)) is greater than about 0.4.
Here, the form factor means a value indicating the diameter and height of a cylindrical battery. The form factor of the cylindrical battery according to an embodiment of the present disclosure may be, for example, 46110 battery, 4875 battery, 48110 battery, 4880 battery, or 4680 battery. In the numerical value representing the form factor, first two numbers indicate the diameter of the battery and the remaining numbers indicate the height of the battery.
A battery according to an embodiment of the present disclosure may be a battery having an approximately cylindrical shape, whose diameter is approximately 46 mm, height is approximately 110 mm, and form factor ratio is 0.418.
A battery according to another embodiment may be a battery having a substantially cylindrical shape, whose diameter is about 48 mm, height is about 75 mm, and form factor ratio is 0.640.
A battery according to still another embodiment may be a battery having an approximately cylindrical shape, whose diameter is approximately 48 mm, height is approximately 110 mm, and form factor ratio is 0.436.
A battery according to still another embodiment may be a battery having an approximately cylindrical shape, whose diameter is approximately 48 mm, height is approximately 80 mm, and form factor ratio is 0.600.
A battery according to still another embodiment may be a battery having an approximately cylindrical shape, whose diameter is approximately 46 mm, height is approximately 80 mm, and form factor ratio is 0.575.
Conventionally, batteries having a form factor ratio of about 0.4 or less have been used. That is, conventionally, for example, 1865 battery, 2170 battery, etc. were used. The 1865 battery has a diameter of approximately 18 mm, height of approximately 65 mm, and a form factor ratio of 0.277. The 2170 battery has a diameter of approximately 21 mm, a height of approximately 70 mm, and a form factor ratio of 0.300.
Referring to
Referring to
Hereinafter, various embodiments of an electrode plate, an electrode assembly, and a cylindrical battery will be described with reference to
First, the electrode assembly according to an embodiment of the present disclosure will be described. The electrode assembly is a jelly-roll type electrode assembly with a structure in which the first electrode and the second electrode in the form of a sheet and the separator interposed therebetween are wound in one direction.
Preferably, at least one of the first electrode and the second electrode includes an uncoated portion not coated with an active material at the long side end in the winding direction. At least a part of the uncoated portion is used as an electrode tab by itself. The uncoated portion includes a core-side uncoated portion adjacent to the core of the electrode assembly, an outer circumference uncoated portion adjacent to the outer circumference of the electrode assembly, and an intermediate uncoated portion interposed between the core-side uncoated portion and the outer circumference uncoated portion.
Preferably, at least one of the core-side uncoated portion and the outer circumference uncoated portion has a relatively lower height than the intermediate uncoated portion.
Referring to
The uncoated portion 63 includes a core-side uncoated portion B1 adjacent to the core of the electrode assembly, an outer circumference uncoated portion B3 adjacent to the outer circumference of the electrode assembly, and an intermediate uncoated portion B2 interposed between the core-side uncoated portion B1 and the outer circumference uncoated portion B3.
The core-side uncoated portion B1, the outer circumference uncoated portion B3, and the intermediate uncoated portion B2 may be defined as an uncoated portion of a region adjacent to the core, an uncoated portion of a region adjacent to the outer circumference, and an uncoated portion of the other region excluding them, respectively, when the electrode 60a is wound into a jelly-roll type electrode assembly. The boundary of B1/B2 may be appropriately defined as a point at which the height (or change pattern) of the uncoated portion substantially changes as it goes from the core of the electrode assembly to the outer circumference, or a point of a predetermined % based on the radius of the electrode assembly (e.g., 5%, 10%, or 15% point of the radius). The boundary of B2/B3 may be appropriately defined as a point at which the height (or change pattern) of the uncoated portion substantially changes as it goes from the outer circumference of the electrode assembly to the core, or a point of a predetermined % based on the radius of the electrode assembly (e.g., 85%, 90%, or 95% point of the radius). When the boundary of B1/B2 and the boundary of B2/B3 are specified, the intermediate uncoated portion B2 may be specified automatically. If only the boundary of B1/B2 is specified, the boundary of B2/B3 may be appropriately selected at a point near the outer circumference of the electrode assembly. Conversely, when only the boundary of B2/B3 is specified, the boundary of B1/B2 may be appropriately selected at a point near the core of the electrode assembly. In the first embodiment, the height of the uncoated portion 63 is not constant and has a relative difference in the winding direction X. That is, the height (length in the Y-axis direction) of the outer circumference uncoated portion B3 is relatively smaller than the height of the core-side uncoated portion B1 and the intermediate uncoated portion B2.
Referring to
In one modification, the outer circumference uncoated portion B3 may be modified into a step shape (see dotted line) in which the height decreases stepwise.
Referring to
Preferably, the height of the intermediate uncoated portion B2 may have a step shape gradually increasing from the core toward the outer circumference.
Patterns 1 to 7 classify the intermediate uncoated portion B2 based on the position where the height of the uncoated portion 63 changes. Preferably, the number of patterns and the height (length in the Y-axis direction) and width (length in the X-axis direction) of each pattern may be adjusted to distribute stress to the maximum during bending of the uncoated portion 63. The stress distribution is to prevent tearing of the uncoated portion 63.
The width (dB1) of the core-side uncoated portion B1 is designed under the condition that the cavity of the core of the electrode assembly is not covered when the patterns of the intermediate uncoated portion B2 are bent to the core.
In one example, the width (dB1) of the core-side uncoated portion B1 may increase in proportion to the bending length of Pattern 1. The bending length corresponds to the height of the pattern based on the bending point of the pattern.
In a specific example, when the electrode 60c is used to manufacture an electrode assembly of a cylindrical battery having a form factor of 4680, the width (dB1) of the core-side uncoated portion B1 may be set to 180 mm to 350 mm depending on the diameter of the core of the electrode assembly.
In one embodiment, the width of each pattern may be designed to configure the same winding turn of the electrode assembly.
In one modification, the height of the intermediate uncoated portion B2 may have a step shape in which the height increases and then decreases while going from the core to the outer circumference.
In another modification, the outer circumference uncoated portion B3 may be modified to have the same structure as the second embodiment.
In still another modification, the pattern structure applied to the intermediate uncoated portion B2 may be extended to the outer circumference uncoated portion B3 (see dotted line).
Referring to
Preferably, at least a partial region of the intermediate uncoated portion B2 may include a plurality of segments P. The heights of the plurality of segments P may increase stepwise from the core to the outer circumference.
The segment P may be notched by laser. The segment P may be formed by a known metal foil cutting process such as ultrasonic cutting or punching.
In the fourth embodiment, in order to prevent damage to the active material layer 62 and/or the insulating coating layer 64 during bending of the uncoated portion 63, it is preferable to leave a predetermined gap between the bottom of the cutting line between the segments P and the active material layer 62. This is because stress is concentrated near the bottom of the cutting line when the uncoated portion 63 is bent. The gap is preferably 0.2 mm to 4 mm. When the gap is adjusted to the corresponding numerical range, it is possible to prevent the active material layer 62 and/or the insulating coating layer 64 near the bottom of the cutting line from being damaged by stress generated during bending of the uncoated portion 63. In addition, the gap may prevent damage to the active material layer 62 and/or the insulating coating layer 64 due to tolerance during notching or cutting of the segment P. Preferably, when the electrode 60d is wound into an electrode assembly, at least a part of the insulating coating layer 64 may be exposed to the outside of the separator. In this case, when the segment P is bent, the insulating coating layer 64 may support the bending point.
The plurality of segments P may form a plurality of segment groups while going from the core to the outer circumference. The width, height and separation pitch of segments belonging to the same segment group may be substantially the same.
Referring to
Preferably, the width C1 of the segment P may be adjusted in the range of 1 mm to 6 mm. If C1 is less than 1 mm, a non-overlapping region or empty space (gap) occurs, thereby not to secure sufficient welding strength when the segments P are bent toward the core. Meanwhile, if C1 exceeds 6 mm, there is a possibility that uncoated portion 63 near the bending point C4 is torn by stress when the segments P are bent. In addition, the height of the segment may can be adjusted in the range of 2 mm to 10 mm. If C2 is less than 2 mm, a non-overlapping region or empty space (gap) occurs, thereby not to secure sufficient welding strength when the segments P are bent toward the core. Meanwhile, if C2 exceeds 10 mm, it is difficult to manufacture an electrode while maintaining uniform flatness of the uncoated portion in the winding direction X. That is, the height of the uncoated portion increases, resulting in a swell. In addition, the separation pitch C3 of the segments P may be adjusted in the range of 0.05 mm to 1 mm. If C3 is less than 0.05 mm, the uncoated portion 63 near the bending point C4 may be torn due to stress when the segments P are bent. Meanwhile, if C3 exceeds 1 mm, a non-overlapping region or empty space (gap) may occur in which the segments P does not overlap with each other, thereby not to secure sufficient welding strength when the segments P are bent.
Referring to
In one example, the width (dB1) of the core-side uncoated portion B1 may increase in proportion to the bending length of the segment P of Group 1. The bending length corresponds to the height of the segment P based on the bending point (C4 in
In a specific example, when the electrode 60d is used to manufacture an electrode assembly of a cylindrical battery having a form factor of 4680, the width (dB1) of the core-side uncoated portion B1 may be set to 180 mm to 350 mm depending on the diameter of the core of the electrode assembly.
In one embodiment, the width of each segment group may be designed to configure the same winding turn of the electrode assembly.
In one modification, the width and/or height and/or separation pitch of the segments P belonging to the same segment group may increase or decrease gradually and/or stepwise and/or irregularly within the group.
Groups 1 to 7 are only examples of the segment groups. The number of groups and the number of segments P included in each group may be adjusted so that the segments P are overlapped in several layers to maximize the distribution of stress during the bending process of the uncoated portion 63 and to secure sufficient welding strength.
In another modification, the height of the outer circumference uncoated portion B3 may decrease gradually or stepwise as in the first and second embodiments. In addition, the segment structure of the intermediate uncoated portion B2 may be extended to the outer circumference uncoated portion B3 (see dotted line). In this case, the outer circumference uncoated portion B3 may also include a plurality of segments, like the intermediate uncoated portion B2. In this case, the segments of the outer circumference uncoated portion B3 may have a larger width and/or height and/or separation pitch than those of the intermediate uncoated portion B2.
In a specific example, when the electrode 60d is used to manufacture an electrode assembly of a cylindrical battery having a form factor of 4680, segments may be formed in eight groups. At this time, the segments of Groups 1 to 7 may be formed on the intermediate uncoated portion B2, and the segments of Group 8 may be formed on the outer circumference uncoated portion B3 as in the modification described above.
In a specific example, the width (dB1) of the core-side uncoated portion B1 may be 180 mm to 350 mm. The width of Group 1 may be 35% to 40% of the width of the core-side uncoated portion B1. The width of Group 2 may be 130% to 150% of the width of Group 1. The width of Group 3 may be 120% to 135% of the width of Group 2. The width of Group 4 may be 85% to 90% of the width of Group 3. The width of Group 5 may be 120% to 130% of the width of Group 4. The width of Group 6 may be 100% to 120% of the width of Group 5. The width of Group 7 may be 90% to 120% of the width of Group 6. The width of Group 8 may be 115% to 130% of the width of Group 7.
The widths of Groups 1 to 8 do not show a constant increase or decrease pattern because the widths of the segments gradually increase from Group 1 to Group 8, but the number of segments included in the group is limited to an integer number. Therefore, the number of segments may be reduced in a specific segment group. Therefore, the width of the group may show an irregular change pattern as shown in the above example while going from the core to the outer circumference.
That is, when the widths in the winding direction of three segment groups consecutively adjacent to each other in the radial direction of the electrode assembly are W1, W2, and W3, respectively, a combination of segment groups in which W3/W2 is smaller than W2/W1 may be included.
In the specific example, Groups 4 to 6 correspond to this. The width ratio of Group 5 to Group 4 is 120% to 130%, and the width ratio of Group 6 to Group 5 is 100% to 120%, which is less than 120% to 130%.
Referring to
Referring to
Preferably, the width D1 of the segment P′ may be adjusted in the range of 1 mm to 6 mm. If D1 is less than 1 mm, when the segments P′ are bent toward the core, a region or empty space (gap) may occur where the segments P′ do not overlap each other, thereby not to secure sufficient welding strength. Meanwhile, if D1 exceeds 6 mm, there is a possibility that the uncoated portion 63 near the bending point D4 is torn by stress when the segments P′ are bent. In addition, the height of the segment P′ may be adjusted in the range of 2 mm to 10 mm. If D2 is less than 2 mm, when the segments P′ are bent toward the core, a region or empty space (gap) may occur where the segments P′ do not overlap each other, thereby not to secure sufficient welding strength. Meanwhile, when D2 exceeds 10 mm, it is difficult to manufacture an electrode while uniformly maintaining the flatness of the uncoated portion 63 in the winding direction. In addition, the separation pitch D3 of the segment P′ may be adjusted in the range of 0.05 mm to 1 mm. If D3 is less than 0.05 mm, the uncoated portion 63 near bending point D4 may be tom due to stress when the segments P′ are bent. Meanwhile, if D3 exceeds 1 mm, a region or empty space (gap) may occur in which the segments P′ do not overlap each other, thereby not to secure sufficient welding strength when the segments P′ are bent.
In the fifth embodiment, the lower interior angle (θ) of a trapezoidal shape may increase from the core to the outer circumference of the plurality of segments P′. As the radius of the electrode assembly A increases, the curvature decreases. If the lower interior angle (θ) of the segment P′ increases as the radius of the electrode assembly increases, the stress generated in the radial direction and the circumferential direction when the segments P′ are bent may be relieved. In addition, if the lower interior angle (θ) increases, the area overlapping with a segment P′ at an inner side and the number of overlapping layers also increase when the segments P′ are bent, so it is possible to secure uniform welding strength in the radial direction and the circumferential direction and form a flat bent surface.
In one example, when the electrode 60e is used to manufacture an electrode assembly of a cylindrical battery having a form factor of 4680, when the radius of the electrode assembly A increases from 4 mm to 22 mm, the inner angle of the segment P′ may be increased stepwise in the range of 60 degrees to 85 degrees.
In one modification, the height of the outer circumference uncoated portion B3 may decrease gradually or stepwise as in the first and second embodiments. In addition, the segment structure of the intermediate uncoated portion B2 may extend to the outer circumference uncoated portion B3 (see dotted line). In this case, the outer circumference uncoated portion B3 may also include a plurality of segments, like the intermediate uncoated portion B2. In this case, the segments of the outer circumference uncoated portion B3 may have a larger width and/or height and/or separation pitch than the intermediate uncoated portion B2.
Like the fourth and fifth embodiments, when the intermediate uncoated portion B2 includes a plurality of segments P, P′, the shape of each segment P, P′ may be modified to a triangle, semicircle, semi-ellipse, or parallelogram.
In addition, it is possible to change the shape of the segment P, P′ differently according to the region of the intermediate uncoated portion B2. In one example, the region where stress is concentrated may have a round shape (e.g., semicircular shape, semi-elliptical shape, etc.) that is advantageous for stress distribution, and the region where the stress is relatively low may have in a polygonal shape (e.g., rectangular shape, trapezoidal shape, parallelogram shape, etc.) with the greatest area as possible.
In the fourth and fifth embodiments, the segment structure of the intermediate uncoated portion B2 is also applicable to the core-side uncoated portion B1. However, if the segment structure is applied to the core-side uncoated portion B1, reverse forming in which the end of the core-side uncoated portion B1 is bent toward the outer circumference when the segments P, P′ of the intermediate uncoated portion B2 are bent according to the radius of curvature of the core may occur. Therefore, there is no segment structure in the core-side uncoated portion B1, or even if the segment structure is applied, the width and/or height and/or separation pitch of the segments P, P′ are preferably adjusted to a level where reverse forming does not occur in consideration of the radius of curvature of the core.
The electrode structure of the embodiments (modifications) described above may be applied to at least one of the first electrode and the second electrode having different polarities included in the jelly-roll type electrode assembly A. In addition, when the electrode structure of the embodiments (modifications) is applied to any one of the first electrode and the second electrode, a conventional electrode structure may be applied to the other one. In addition, the electrode structures applied to the first electrode and the second electrode may not be the same and may be different.
For example, when the first electrode and the second electrode are a positive electrode and a negative electrode, respectively, any one of the embodiments (modifications) may be applied to the first electrode, and a conventional electrode structure (see
As another example, when the first electrode and the second electrode are a positive electrode and a negative electrode, respectively, any one of the embodiments (modifications) may be selectively applied to the first electrode, and any one of the embodiments (modifications) may be selectively applied to the second electrode.
Hereinafter, the structure of an electrode assembly according to an embodiment of the present disclosure will be described in detail.
The electrode assembly A1 may be manufactured by the winding method described through
The pattern in which the heights of the uncoated portions 43a, 43b change is schematically shown. That is, the heights of the uncoated portions 43a, 43b may vary irregularly according to the position where the section is cut. For example, when a side portion of the trapezoidal segment P, P′ is cut, the height of the uncoated portion in the cross section becomes lower than that of the segment P, P′. Accordingly, it should be understood that the heights of the uncoated portions 43a, 43b shown in the cross-sectional views of the electrode assembly correspond to the average of the height (C2 in
Referring to
The height (length in the Y-axis direction) of the outer circumference uncoated portion B3 is relatively smaller than the height of the intermediate uncoated portion B2. Therefore, it is possible to prevent an internal short circuit from occurring while the outer circumference uncoated portion B3 is pressed against the beading portion of the battery housing.
The lower uncoated portion 43b has the same structure as the upper uncoated portion 43a. In one modification, the lower uncoated portion 43b may have a conventional electrode structure or an electrode structure of other embodiments (modifications).
The ends 81 of the upper uncoated portion 43a and the lower uncoated portion 43b may be bent from the outer circumference of the electrode assembly A1 toward the core. In this case, the outer circumference uncoated portion B3 may not be substantially bent.
Referring to
The height of the outer circumference uncoated portion B3 is relatively smaller than the height of the intermediate uncoated portion B2 and decreases gradually or stepwise from the core to the outer circumference. Therefore, it is possible to prevent an internal short circuit from occurring while the outer circumference uncoated portion B3 is pressed against the beading portion of the battery housing.
The lower uncoated portion 43b has the same structure as the upper uncoated portion 43a. In one modification, the lower uncoated portion 43b may have a conventional electrode structure or an electrode structure of other embodiments (modifications).
The ends 91 of the upper uncoated portion 43a and the lower uncoated portion 43b may be bent from the outer circumference of the electrode assembly A2 to the core. In this case, the outermost side 92 of the outer circumference uncoated portion B3 may not be substantially bent.
Referring to
The height of the core-side uncoated portion B1 is relatively smaller than the height of the intermediate uncoated portion B2. Also, in the intermediate uncoated portion B2, the bending length of the innermost uncoated portion 43a is equal to or smaller than the radial length R of the core-side uncoated portion B1. The bending length H corresponds to a height of the uncoated portion 43a based on a point at which the uncoated portion 43a is bent (C4 in
Therefore, even if the intermediate uncoated portion B2 is bent, the bent portion does not block the cavity 102 of the core of the electrode assembly A3. If the cavity 102 is not blocked, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, by inserting a welding jig through the cavity 102, a welding process between the current collecting plate of the negative electrode and the battery housing may be easily performed.
The height of the outer circumference uncoated portion B3 is relatively smaller than the height of the intermediate uncoated portion B2. Therefore, it is possible to prevent an internal short circuit from occurring while the outer circumference uncoated portion B3 is pressed against the beading portion of the battery housing.
In one modification, the height of the outer circumference uncoated portion B3 may decrease gradually or stepwise, unlike that shown in
The lower uncoated portion 43b has the same structure as the upper uncoated portion 43a. In one modification, the lower uncoated portion 43b may have a conventional electrode structure or an electrode structure of other embodiments (modifications).
The ends 101 of the upper uncoated portion 43a and the lower uncoated portion 43b may be bent from the outer circumference of the electrode assembly A3 toward the core. At this time, the core-side uncoated portion B1 and the outer circumference uncoated portion B3 are not substantially bent.
When the intermediate uncoated portion B2 includes a plurality of segments, bending stress is alleviated, so it is possible to prevent tearing or abnormal deformation of the uncoated portion 43a near the bending point. In addition, when the width and/or height and/or separation pitch of the segments is adjusted according to the numerical range of the above embodiment, the segments do not form an empty hole (gap) in the bent surface (surface viewed in the Y-axis) while being bent toward the core and overlapped in several layers enough to secure sufficient welding strength.
Referring to
The outer circumference uncoated portion B3 may include a plurality of segments. The fourth and fifth embodiments (modifications) may be substantially identically applied to the configuration of the plurality of segments.
In the electrode assembly A4, the height of the core-side uncoated portion B1 is relatively smaller than the height of the intermediate uncoated portion B2. In addition, in the intermediate uncoated portion B2, the bending length H of the innermost uncoated portion is equal to or smaller than the radial length R of the core-side uncoated portion B1.
Therefore, even if the intermediate uncoated portion B2 is bent, the bent portion does not block the cavity 112 of the core of the electrode assembly A4. If the cavity 112 is not blocked, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, by inserting a welding jig through the cavity 112, a welding process between the current collecting plate of the negative electrode and the battery housing may be easily performed.
In one modification, a structure in which the height of the intermediate uncoated portion B2 increases gradually or stepwise from the core toward the outer circumference may extend to the outer circumference uncoated portion B3. In this case, the height of the uncoated portion 43a may gradually or stepwise increase from the boundary between the core-side uncoated portion B1 and the intermediate uncoated portion B2 to the outermost side surface of the electrode assembly A4.
The lower uncoated portion 43b has the same structure as the upper uncoated portion 43a. In one modification, the lower uncoated portion 43b may have a conventional electrode structure or an electrode structure of other embodiments (modifications).
The ends 111 of the upper uncoated portion 43a and the lower uncoated portion 43b may be bent toward the core from the outer circumference of the electrode assembly A4. At this time, the core-side uncoated portion B1 is not substantially bent.
When the intermediate uncoated portion B2 and the outer circumference uncoated portion B3 include a plurality of segments, the bending stress is relieved, so it is possible to prevent tearing or abnormal deformation of the uncoated portion 43a, 43b near the bending point. In addition, when the width and/or height and/or separation pitch of the segments is adjusted according to the numerical range of the above embodiment, the segments do not form an empty hole (gap) in the bent surface (surface viewed in the Y-axis) while being bent toward the core and overlapped in several layers enough to secure sufficient welding strength.
Referring to
Such a change in height of the intermediate uncoated portion B2 may be implemented by adjusting the height of a step pattern (see
In the electrode assembly A5, the height of the core-side uncoated portion B1 is relatively smaller than the height of the intermediate uncoated portion B2. In addition, in the intermediate uncoated portion B2, the bending length H of the innermost uncoated portion is equal to or smaller than the radial length R of the core-side uncoated portion B1.
Therefore, even if the intermediate uncoated portion B2 is bent toward the core, the bent portion does not block the cavity 122 of the core of the electrode assembly A5. If the cavity 122 is not blocked, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, by inserting a welding jig through the cavity 122, a welding process between the current collecting plate of the negative electrode and the battery housing may be easily performed.
Also, the height of the outer circumference uncoated portion B3 is relatively smaller than the height of the intermediate uncoated portion B2. Therefore, it is possible to prevent an internal short circuit from occurring while the outer circumference uncoated portion B3 is pressed against the beading portion of the battery housing. In one modification, the height of the outer circumference uncoated portion B3 may decrease gradually or stepwise toward the outer circumference.
The lower uncoated portion 43b has the same structure as the upper uncoated portion 43a. In a modification, the lower uncoated portion 43b may have a conventional electrode structure or an electrode structure of other embodiments (modifications).
The ends 121 of the upper uncoated portion 43a and the lower uncoated portion 43b may be bent toward the core from the outer circumference of the electrode assembly A5. At this time, the core-side uncoated portion B1 and the outer circumference uncoated portion B3 are not substantially bent.
When the intermediate uncoated portion B2 includes a plurality of segments, bending stress is alleviated, so it is possible to prevent tearing or abnormal deformation of the uncoated portion 43a, 43b. In addition, when the width and/or height and/or separation pitch of the segments is adjusted according to the numerical range of the above embodiment, the segments do not form an empty hole (gap) in the bent surface (surface viewed in the Y-axis) while being bent toward the core and overlapped in several layers enough to secure sufficient welding strength.
Referring to
The change in height of the outer circumference uncoated portion B3 may be implemented by extending the step pattern (see
In the electrode assembly A6, the height of the core-side uncoated portion B1 is relatively smaller than the height of the intermediate uncoated portion B2. In addition, in the intermediate uncoated portion B2, the bending length H of the innermost uncoated portion is equal to or smaller than the radial length R of the core-side uncoated portion B1.
Therefore, even if the intermediate uncoated portion B2 is bent toward the core, the bent portion does not block the cavity 132 of the core of the electrode assembly A5. If the cavity 132 is not blocked, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, by inserting a welding jig through the cavity 132, a welding process between the current collecting plate of the negative electrode and the battery housing may be easily performed.
The lower uncoated portion 43b has the same structure as the upper uncoated portion 43a. In one modification, the lower uncoated portion 43b may have a conventional electrode structure or an electrode structure of other embodiments (modifications).
The ends 131 of the upper uncoated portion 43a and the lower uncoated portion 43b may be bent toward the core from the outer circumference of the electrode assembly A6. At this time, the core-side uncoated portion B1 is not substantially bent.
When the intermediate uncoated portion B2 and the outer circumference uncoated portion B3 include a plurality of segments, the bending stress is relieved, so it is possible to prevent tearing or abnormal deformation of the uncoated portion 43a, 43b near the bending point. In addition, when the width and/or height and/or separation pitch of the segments is adjusted according to the numerical range of the above embodiment, the segments do not form an empty hole (gap) in the bent surface (surface viewed in the Y-axis) while being bent toward the core and overlapped in several layers enough to secure sufficient welding strength.
Various electrode assembly structures according to embodiments of the present disclosure may be applied to a jelly-roll type cylindrical battery.
Preferably, the cylindrical battery may be, for example, a cylindrical battery having a form factor ratio (defined as a value obtained by dividing the diameter of the cylindrical battery by the height, namely the ratio of the diameter (Φ) to the height (H)) of greater than about 0.4.
The cylindrical battery according to an embodiment of the present disclosure may be, for example, 46110 battery, 4875 battery, 48110 battery, 4880 battery, or 4680 battery.
When an electrode assembly with a tab-less structure is applied to a cylindrical battery whose form factor ratio exceeds 0.4, the stress applied in the radial direction is large when bending the uncoated portion, so the uncoated portion is easily tom. In addition, when welding the current collecting plate to the bent surface of the uncoated portion, the number of overlapping layers of the uncoated portion must be sufficiently increased in order to sufficiently secure welding strength and lower resistance. These requirements can be achieved by the electrodes and the electrode assemblies according to the embodiments (modifications) of the present disclosure.
Hereinafter, a cylindrical battery according to an embodiment of the present disclosure will be described in detail.
Referring to
The battery housing 142 is a cylindrical container with an opening formed at an upper side. The battery housing 142 is made of a metal material having conductivity such as aluminum or steel. The battery housing 142 accommodates the electrode assembly 141 in the inner space through the top opening and also accommodates the electrolyte.
The electrode assembly 141 may have a jelly-roll shape. As shown in
The first and second electrodes have different polarities. That is, when one has positive polarity, the other has negative polarity. At least one of the first electrode and the second electrode may have an electrode structure according to the above embodiments (modifications). In addition, the other one of the first electrode and the second electrode may have a conventional electrode structure or an electrode structure according to embodiments (modifications).
The uncoated portion 146a of the first electrode and the uncoated portion 146b of the second electrode protrude from the upper and lower portions of the electrode assembly 141, respectively. The first electrode has the electrode structure of the first embodiment (modification). Therefore, in the uncoated portion 146a of the first electrode, the height of the outer circumference uncoated portion B3 is smaller than the height of the uncoated portion of the other region. The outer circumference uncoated portion B3 is spaced apart from the inner circumference of the battery housing 142, particularly the beading portion 147, by a predetermined distance. Therefore, the outer circumference uncoated portion B3 of the first electrode does not come into contact with the battery housing 142 electrically connected to the second electrode, thereby preventing an internal short circuit of the battery 140.
The uncoated portion 146b of the second electrode has the same height. In a modification, the uncoated portion 146b of the second electrode may have the same structure as the uncoated portion 146a of the first electrode. In another modification, the uncoated portion 146b of the second electrode may selectively have an uncoated portion structure of the electrodes according to the embodiments (modifications).
The sealing body 143 may include a cap plate 143a, a first gasket 143b for providing airtightness between the cap plate 143a and the battery housing 142 and having insulation property, and a connection plate 143c electrically and mechanically coupled to the cap plate 143a.
The cap plate 143a is a component made of a conductive metal material and covers the top opening of the battery housing 142. The cap plate 143a is electrically connected to the uncoated portion 146a of the first electrode and electrically insulated from the battery housing 142 through the first gasket 143b. Accordingly, the cap plate 143a may function as a first electrode terminal of the cylindrical battery 140.
The cap plate 143a is seated on the beading portion 147 formed on the battery housing 142 and is fixed by the crimping portion 148. A first gasket 143b may be interposed between the cap plate 143a and the crimping portion 148 to secure airtightness of the battery housing 142 and to electrically insulate the battery housing 142 and the cap plate 143a. The cap plate 143a may have a protrusion 143d protruding upward from the center thereof.
The battery housing 142 is electrically connected to the uncoated portion 146b of the second electrode. Therefore, the battery housing 142 has the same polarity as the second electrode. If the second electrode has a negative polarity, the battery housing 142 also has a negative polarity.
The battery housing 142 has a beading portion 147 and a crimping portion 148 on the top. The beading portion 147 is formed by press-fitting the periphery of the outer circumference of the battery housing 142. The beading portion 147 prevents the electrode assembly 141 accommodated inside the battery housing 142 from escaping through the top opening of the battery housing 142, and may function as a support portion on which the sealing body 143 seats.
The inner circumference of the beading portion 147 is spaced apart from the outer circumference uncoated portion B3 of the first electrode by a predetermined distance. More specifically, the bottom of the inner circumference of the beading portion 147 is spaced apart from the outer circumference uncoated portion B3 of the first electrode by a predetermined distance. In addition, since the outer circumference uncoated portion B3 has a low height, the outer circumference uncoated portion B3 is not substantially affected even when the battery housing 142 is press-fitted from the outside to form the beading portion 147. Therefore, the outer circumference uncoated portion B3 is not pressed by other components such as the beading portion 147, and thus partial shape deformation of the electrode assembly 141 is prevented, thereby preventing a short circuit inside the cylindrical battery 140.
Preferably, when the press-in depth of the beading portion 147 is defined as D1 and the radial length from the inner circumference of the battery housing 142 to the boundary point between the outer circumference uncoated portion B3 and the intermediate uncoated portion B2 is defined as D2, the relation D1≤D2 can be satisfied. In this case, when the battery housing 142 is press-fitted to form the beading portion 147, damage to the outer circumference uncoated portion B3 is substantially prevented.
The crimping portion 148 is formed on the upper portion of the beading portion 147. The crimping portion 148 has an extended and bent shape to surround the outer circumference of the cap plate 143a disposed on the beading portion 147 and a part of the upper surface of the cap plate 143a.
The cylindrical battery 140 may further include a first current collecting plate 144 and/or a second current collecting plate 145 and/or an insulator 146.
The first current collecting plate 144 is coupled to the upper portion of the electrode assembly 141. The first current collecting plate 144 is made of a conductive metal material such as aluminum, copper, or nickel and is electrically connected to the uncoated portion 146a of the first electrode. A lead 149 may be connected to the first current collecting plate 144. The lead 149 may extend upward from the electrode assembly 141 and be coupled to the connection plate 143c or directly coupled to the lower surface of the cap plate 143a. The lead 149 may be coupled with other components by welding.
Preferably, the first current collecting plate 144 may be integrally formed with the lead 149. In this case, the lead 149 may have a long plate shape extending outward from the center of the first current collecting plate 144.
The first current collecting plate 144 may have a plurality of irregularities (not shown) radially formed on the lower surface thereof. When the radial irregularities are provided, the irregularities may be press-fitted into the uncoated portion 146a of the first electrode by pressing the first current collecting plate 144.
The first current collecting plate 144 is coupled to the end of the uncoated portion 146a of the first electrode. The coupling between the uncoated portion 146a and the first current collecting plate 144 may be performed by, for example, laser welding. Laser welding may be performed by partially melting the base material of the current collecting plate. In a modification, welding between the first current collecting plate 144 and the uncoated portion 146a may be performed with a solder interposed therebetween. In this case, the solder may have a lower melting point compared to the first current collecting plate 144 and the uncoated portion 146a. The laser welding may be replaced with resistance welding or ultrasonic welding.
The second current collecting plate 145 may be coupled to the lower surface of the electrode assembly 141. One surface of the second current collecting plate 145 may be coupled to the uncoated portion 146b of the second electrode by welding, and the opposite surface may be coupled to the inner bottom surface of the battery housing 142 by welding. The coupling structure between the second current collecting plate 145 and the uncoated portion 146b of the second electrode may be substantially the same as the coupling structure between the first current collecting plate 144 and the uncoated portion 146a of the first electrode.
The uncoated portions 146a, 146b are not limited to the illustrated structure. Accordingly, the uncoated portions 146a, 146b may selectively have an uncoated portion structure of an electrode according to embodiments (modifications) as well as a conventional uncoated portion structure.
The insulator 146 may cover the first current collecting plate 144. The insulator 146 may prevent direct contact between the first current collecting plate 144 and the inner circumference of the battery housing 142 by covering the first current collecting plate 144 on the upper surface of the first current collecting plate 144.
The insulator 146 has a lead hole 151 so that the lead 149 extending upward from the first current collecting plate 144 may be drawn out. The lead 149 is drawn upward through the lead hole 151 and coupled to the lower surface of the connection plate 143c or the lower surface of the cap plate 143a.
A peripheral region of the edge of the insulator 146 may be interposed between the first current collecting plate 144 and the beading portion 147 to fix the combination of the electrode assembly 141 and the first current collecting plate 144. Accordingly, in the combination of the electrode assembly 141 and the first current collecting plate 144, the movement of the battery 140 in the height direction is restricted, so the assembly stability of the battery 140 may be improved.
The insulator 146 may be made of an insulating polymer resin. In one example, insulator 146 may be made of polyethylene, polypropylene, polyimide or polybutylene terephthalate.
The battery housing 142 may further include a venting portion 152 formed at the lower surface thereof. The venting portion 152 corresponds to a region having a smaller thickness compared to the surrounding region, in the lower surface of the battery housing 142. The venting portion 152 is structurally weak compared to the surrounding region. Therefore, when an abnormality occurs in the cylindrical battery 140 and the internal pressure increases to a predetermined level or more, the venting portion 152 may be ruptured, so that the gas generated inside the battery housing 142 may be discharged to the outside.
The venting portion 152 may be continuously or discontinuously formed while drawing a circle on the lower surface of the battery housing 142. In a modification, the venting portion 152 may be formed in a straight line pattern or other patterns.
Referring to
Referring to
The outer circumference uncoated portion B3 forms an inclined surface. Therefore, when the battery housing 142 is press-fitted to form the beading portion 147, it is possible to prevent the outer circumference uncoated portion B3 from being compressed and damaged by the beading portion 147. In addition, it is possible to suppress a phenomenon in which the outer circumference uncoated portion B3 contacts the battery housing 142 having a different polarity and causes an internal short circuit.
The other configuration of the cylindrical battery 150 is substantially the same as the embodiment (modification) described above.
The uncoated portions 146a, 146b are not limited to the illustrated structure. Accordingly, the uncoated portions 146a, 146b may selectively have an uncoated portion structure of the electrodes according to embodiments (modifications) as well as a conventional uncoated portion structure.
Referring to
In the cylindrical battery 160, the diameter of the first current collecting plate 144 and the diameter of the outermost side of the intermediate uncoated portion B2 are smaller than the minimum inner diameter of the battery housing 142. Also, the diameter of the first current collecting plate 144 may be equal to or greater than the diameter of the outermost side of the intermediate uncoated portion B2.
Specifically, the minimum inner diameter of the battery housing 142 may correspond to the inner diameter of the battery housing 142 at a position where the beading portion 147 is formed. At this time, the diameters of the first current collecting plate 144 and the outermost side of the intermediate uncoated portion B2 are smaller than the inner diameter of the battery housing 142 at the position where the beading portion 147 is formed. Also, the diameter of the first current collecting plate 144 may be equal to or greater than the diameter of the outermost side of the intermediate uncoated portion B2. The peripheral region of the edge of the insulator 146 may be interposed between the outer circumference uncoated portion B3 and the beading portion 147 in a downwardly bent state to fix the combination of the electrode assembly 141 and the first current collecting plate 144.
Preferably, the insulator 146 includes a part covering the outer circumference uncoated portion B3 and a part covering the first current collecting plate 144, and a part connecting the two parts may have a bent shape corresponding to the curved shape of the beading portion 147. The insulator 146 may insulate the outer circumference uncoated portion B3 and the inner circumference of the beading portion 147 and at the same time insulate the first current collecting plate 144 and the inner circumference of the beading portion 147.
The first current collecting plate 144 may be positioned higher than the bottom of the beading portion 147 and may be coupled to the core-side uncoated portion B1 and the intermediate uncoated portion B2. At this time, the press-in depth D1 of the beading portion 147 is equal to or smaller than the distance D2 from the inner circumference of the battery housing 142 to the boundary between the outer circumference uncoated portion B3 and the intermediate uncoated portion B2. Accordingly, the core-side uncoated portion B1, the intermediate uncoated portion B2, and the first current collecting plate 144 coupled thereto may be positioned higher than the bottom of the beading portion 147. The bottom of the beading portion 147 means a bending point B between the portion of the battery housing 142 where the electrode assembly 141 is accommodated and the beading portion 147.
Since the core-side uncoated portion B1 and the intermediate uncoated portion B2 occupy the inner space in the radial direction of the beading portion 147, an empty space between the electrode assembly 141 and the cap plate 143a may be minimized. In addition, the connection plate 143c located in the empty space between the electrode assembly 141 and the cap plate 143a is omitted. Accordingly, the lead 149 of the first current collecting plate 144 may be directly coupled to the lower surface of the cap plate 143a. According to the above structure, the empty space in the battery is reduced, and the energy density can be maximized as much as the reduced empty space.
In the cylindrical battery 160, the first current collecting plate 144 and the second current collecting plate 145 may be welded to the ends of the uncoated portions 146a, 146b, respectively, in the same manner as in the above embodiment.
The uncoated portions 146a, 146b are not limited to the illustrated structure. Accordingly, the uncoated portions 146a, 146b may selectively have an uncoated portion structure of an electrode according to embodiments (modifications) as well as a conventional uncoated portion structure.
Referring to
Specifically, the cylindrical battery 170 includes a battery housing 171 through which an external terminal 172 is installed. The external terminal 172 is installed on the closed surface (upper surface in the drawing) of the battery housing 171. The external terminal 172 is riveted to the perforated hole of the battery housing 171 with the insulating second gasket 173 interposed therebetween. The external terminal 172 is exposed to the outside in a direction opposite to the direction of gravity.
The external terminal 172 includes a terminal exposing portion 172a and a terminal insert portion 172b. The terminal exposing portion 172a is exposed to the outside of the closed surface of the battery housing 171. The terminal exposing portion 172a may be positioned approximately at the center of the closed surface of the battery housing 171. The maximum diameter of the terminal exposing portion 172a may be greater than the maximum diameter of the perforated hole formed in the battery housing 171. The terminal insert portion 172b may be electrically connected to the uncoated portion 146a of the first electrode through a substantially central portion of the closed surface of the battery housing 171. The terminal insert portion 172b may be riveted to the inner surface of the battery housing 171. That is, the lower edge of the terminal insert portion 172b may have a curved shape toward the inner surface of the battery housing 171. The maximum diameter of the lower part of the terminal insert portion 172b may be greater than the maximum diameter of the perforated hole of the battery housing 171.
The bottom surface of the terminal insert portion 172b may be welded to the first current collecting plate 144 connected to the uncoated portion 146a of the first electrode. An insulator 174 made of an insulating material may be interposed between the first current collecting plate 144 and the inner surface of the battery housing 171. The insulator 174 covers the upper portion of the first current collecting plate 144 and the top edge of the electrode assembly 141. As a result, it is possible to prevent the outer circumference uncoated portion B3 of the electrode assembly 141 from contacting the inner surface of the battery housing 171 having a different polarity to cause a short circuit. The terminal insert portion 172b of the external terminal 172 may be welded to the first current collecting plate 144 through the insulator 174.
The second gasket 173 is interposed between the battery housing 171 and the external terminal 172 to prevent electrical contact between the battery housing 171 and the external terminal 172 having opposite polarities. As a result, the upper surface of the battery housing 171 having a substantially flat shape may function as a second electrode terminal of the cylindrical battery 170.
The second gasket 173 includes a gasket exposing portion 173a and a gasket insert portion 173b. The gasket exposing portion 173a is interposed between the terminal exposing portion 172a of the external terminal 172 and the battery housing 171. The gasket insert portion 173b is interposed between the terminal insert portion 172b of the external terminal 172 and the battery housing 171. The gasket insert portion 173b may be deformed together during riveting of the terminal insert portion 172b to come into close contact with the inner surface of the battery housing 171. The second gasket 173 may be made of, for example, a polymer resin having insulating properties.
The gasket exposing portion 173a of the second gasket 173 may have an extended shape to cover the outer circumference of the terminal exposing portion 172a of the external terminal 172. When the second gasket 173 covers the outer circumference of the external terminal 172, it is possible to prevent a short circuit from occurring during a process of coupling an electrical connection component such as a bus bar to the upper surface of the battery housing 171 and/or the external terminal 172. Although not shown in the drawing, the gasket exposing portion 173a may have an extended shape to cover not only the outer circumference of the terminal exposing portion 172a but also a part of the upper surface.
When the second gasket 173 is made of a polymer resin, the second gasket 173 may be coupled to the battery housing 171 and the external terminal 172 by thermal fusion. In this case, airtightness at the coupling interface between the second gasket 173 and the external terminal 172 and at the coupling interface between the second gasket 173 and the battery housing 171 may be enhanced. Meanwhile, when the gasket exposing portion 173a of the second gasket 173 is shaped to extend to the upper surface of the terminal exposing portion 172a, the external terminal 172 may be integrally coupled with the second gasket 173 by insert injection.
In the upper surface of the battery housing 171, a region 175 other than a region occupied by the external terminal 172 and the second gasket 173 corresponds to a second electrode terminal having a polarity opposite to that of the external terminal 172.
The second current collecting plate 176 is coupled to the lower portion of the electrode assembly 141. The second current collecting plate 176 is made of a conductive metal material such as aluminum, steel, copper, or nickel, and is electrically connected to the uncoated portion 146b of the second electrode.
Preferably, the second current collecting plate 176 is electrically connected to the battery housing 171. To this end, at least a part of the edge of the second current collecting plate 176 may be interposed and fixed between the inner surface of the battery housing 171 and the first gasket 178b. In one example, at least a part of the edge of the second current collecting plate 176 may be fixed to the beading portion 180 by welding while being supported on the bottom surface of the beading portion 180 formed on the bottom of the battery housing 171. In a modification, at least a part of the edge of the second current collecting plate 176 may be directly welded to the inner wall surface of the battery housing 171.
The second current collecting plate 176 may include a plurality of irregularities (not shown) radially formed on a surface facing the uncoated portion 146b. When the irregularities are formed, the irregularities may be press-fitted into the uncoated portion 146b by pressing the second current collecting plate 176.
Preferably, the second current collecting plate 176 and the end of the uncoated portion 146b may be coupled by welding, for example laser welding.
The sealing body 178 sealing the lower opening of the battery housing 171 includes a cap plate 178a and a first gasket 178b. The first gasket 178b electrically separates the cap plate 178a and the battery housing 171. The crimping portion 181 fixes the edge of the cap plate 178a and the first gasket 178b together. A venting portion 179 is provided to the cap plate 178a. The configuration of the venting portion 179 is substantially the same as the embodiment (modification) described above.
Preferably, the cap plate 178a is made of a conductive metal material. However, since the first gasket 178b is interposed between the cap plate 178a and the battery housing 171, the cap plate 178a does not have an electrical polarity. The sealing body 178 seals the opening of the lower portion of the battery housing 171 and functions to discharge gas when the internal pressure of the battery 170 increases to a critical value or above.
Preferably, an external terminal 172 electrically connected to the uncoated portion 146a of the first electrode is used as the first electrode terminal. In addition, in the upper surface of the battery housing 171 electrically connected to the uncoated portion 146b of the second electrode through the second current collecting plate 176, a portion 175 excluding the external terminal 172 is used as a second electrode terminal having a different polarity from the first electrode terminal. When two electrode terminals are located on the upper portion of the cylindrical battery 170 as above, it is possible to dispose electrical connection components such as bus bars on only one side of the cylindrical battery 170. This may lead to simplification of the battery pack structure and improvement of energy density. In addition, since the portion 175 used as the second electrode terminal has a substantially flat shape, sufficient bonding area may be secured for coupling electrical connection components such as bus bars. Accordingly, the cylindrical battery 170 may lower the resistance at the bonding portion of the electrical connecting components to a desirable level.
The structure of the electrode assembly 141 and the structure of the uncoated portion are not limited to those shown, and may be replaced with structures of the above embodiments (modifications).
Referring to
Accordingly, the configuration of the embodiments (modification) of the cylindrical batteries 150, 170 may be equally applied to the cylindrical battery 180.
In addition, the structure of the electrode assembly 141 and the structure of the uncoated portion are not limited to those shown, and may be replaced with structures of the above embodiments (modifications).
Referring to
Referring to
In the electrode assembly A4, the core-side uncoated portion B1 has a relatively smaller height than the other portions. In addition, as shown in
Therefore, even if the uncoated portion 146a is bent toward the core, the cavity 112 of the core of the electrode assembly A4 may be opened upward without being blocked (see the dotted circle).
If the cavity 112 is not blocked, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, a welding process between the second current collecting plate 145 and the battery housing 142 may be easily performed by inserting a welding jig through the cavity 112.
When the uncoated portions 146a, 146b have a segment structure, if the width and/or height and/or separation pitch of the segments is adjusted to satisfy the numerical range of the above embodiment, when the segments are bent, the segments are overlapped in several layers to sufficiently secure the welding strength, and an empty space (gap) is not form on the bent surface.
The structures of the uncoated portions 146a, 146b may be changed as desired to structures according to the above embodiments (modifications), different from those shown in the drawings. In addition, a conventional uncoated portion structure may be applied to either one of the uncoated portions 146a, 146b without limitation.
Referring to
Referring to
In the electrode assembly A4, the core-side uncoated portion B1 has a relatively lower height than the other portions. In addition, as shown in
Therefore, even when the uncoated portions 146a, 146b are bent toward the core, the cavity 112 of the core of the electrode assembly A4 may be opened upward without being blocked (see the dotted circle).
If the cavity 112 is not blocked, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, a welding process between the second current collecting plate 176 and the battery housing 171 may be easily performed by inserting a welding jig through the cavity 112.
When the uncoated portions 146a, 146b have a segment structure, if the width and/or height and/or separation pitch of the segments are adjusted to satisfy the numerical range of the above embodiment, when the segments are bent, the segments are overlapped in several layers to sufficiently secure the welding strength, and an empty space (gap) is not formed on the bent surface.
The structures of the uncoated portions 146a, 146b may be changed as desired to structures according to the above embodiments (modifications), different from those shown in the drawings. In addition, a conventional uncoated portion structure may be applied to either one of the uncoated portions 146a, 146b without limitation.
Referring to
Preferably, the uncoated portions 146a, 146b of the electrode assembly A3 are bent from the outer circumference toward the core. At this time, since the core-side uncoated portion B1 and the outer circumference uncoated portion B3 of the uncoated portion 146a have a lower height than other portions, they are not substantially bent. This is the same for the uncoated portion 146b. The first current collecting plate 144 may be welded to the bent surface of the uncoated portion 146a, and the second current collecting plate 145 may be welded to the bent surface of the uncoated portion 146b.
The height of the core-side uncoated portion B1 is relatively lower than that of the intermediate uncoated portion B2. In addition, as shown in
Therefore, even if the uncoated portions 146a, 146b are bent toward the core, the cavity 102 of the core of the electrode assembly A3 may be opened upward without being blocked (see the dotted circle).
If the cavity 112 is not blocked, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, a welding process between the second current collecting plate 145 and the battery housing 142 may be easily performed by inserting a welding jig through the cavity.
Also, the height of the outer circumference uncoated portion B3 is relatively lower than that of the intermediate uncoated portion B2. Therefore, when the uncoated portion 146a is bent, the outer circumference uncoated portion B3 is substantially not bent. In addition, since the outer circumference uncoated portion B3 is sufficiently spaced from the beading portion 147, it is possible to solve the problem that the outer circumference uncoated portion B3 is damaged during the press-fitting of the beading portion 147.
When the uncoated portions 146a, 146b have a segment structure, if the width and/or height and/or separation pitch of the segments is adjusted to satisfy the numerical range of the above embodiment, when the segments are bent, the segments are overlapped in several layers to sufficiently secure the welding strength, and an empty space (gap) is not form on the bent surface.
The structures of the uncoated portions 146a, 146b may be changed as desired to structures according to the above embodiments (modifications), different from those shown in the drawings. In addition, a conventional uncoated portion structure may be applied to either one of the uncoated portions 146a, 146b without limitation.
Referring to
Preferably, the uncoated portions 146a, 146b of the electrode assembly A3 are bent from the outer circumference toward the core. At this time, since the core-side uncoated portion B1 of the uncoated portion 146a has a lower height than other portions, it is not substantially bent. This is the same for the uncoated portion 146b. The first current collecting plate 144 may be welded to the bent surface of the uncoated portion 146a, and the second current collecting plate 176 may be welded to the bent surface of the uncoated portion 146b.
In the electrode assembly A3, the height of the core-side uncoated portion B1 is relatively lower than that of the intermediate uncoated portion B2. In addition, as shown in
Therefore, even if the uncoated portions 146a, 146b are bent toward the core, the cavity 102 of the core of the electrode assembly A3 may be opened upward without being blocked (see the dotted circle).
If the cavity 112 is not blocked, there is no difficulty in the electrolyte injection process, and the electrolyte injection efficiency is improved. In addition, a welding process between the second current collecting plate 176 and the battery housing 171 may be easily performed by inserting a welding jig through the cavity 102.
Also, the height of the outer circumference uncoated portion B3 of the uncoated portion 146a is relatively lower than that of the intermediate uncoated portion B2. Therefore, when the uncoated portion 146a is bent, the outer circumference uncoated portion B3 is substantially not bent. Those features may also be applied to the uncoated portion 146b.
When the uncoated portions 146a, 146b have a segment structure, if the width and/or height and/or separation pitch of the segments is adjusted to satisfy the numerical range of the above embodiment, when the segments are bent, the segments are overlapped in several layers to sufficiently secure the welding strength, and an empty space (gap) is not form on the bent surface.
The structures of the uncoated portions 146a, 146b may be changed as desired to structures according to the above embodiments (modifications), different from those shown in the drawings. In addition, a conventional uncoated portion structure may be applied to either one of the uncoated portions 146a, 146b without limitation.
The cylindrical battery according to the above embodiments (modifications) may be used to manufacture a battery pack (see
According to the present disclosure, the internal resistance of a cylindrical battery may be reduced and energy density may be increased by using the uncoated portion itself protruding on the upper and lower portions of the electrode assembly as an electrode tab.
According to another aspect of the present disclosure, by improving the uncoated portion structure of the electrode assembly to prevent interference between the electrode assembly and the inner circumference of the battery housing in the process of forming the beading portion of the battery housing, it is possible to prevent a short circuit from occurring inside the cylindrical battery due to partial deformation of the electrode assembly.
According to still another aspect of the present disclosure, by improving the structure of the uncoated portion of the electrode assembly, it is possible to prevent the uncoated portion near the bending point from being torn when the uncoated portion is bent, and it is possible to improve the welding strength by sufficiently increasing the number of overlapping layers of the uncoated portion.
According to still another aspect of the present disclosure, by improving the structure of the uncoated portion adjacent to the core of the electrode assembly, it is possible to prevent the cavity in the core of the electrode assembly from being blocked when the uncoated portion is bent, so that the electrolyte injection process and the process of welding the battery housing and the current collecting plate may be easily performed.
According to still another aspect of the present disclosure, it is possible to provide a cylindrical battery having a structure with low internal resistance, prevention of internal short circuit, and improved welding strength between the current collecting plate and the uncoated portion, and a battery pack and a vehicle including the cylindrical battery.
Hereinafter, an embodiment of a positive electrode active material used in the cylindrical battery according to the present disclosure will be described.
In an embodiment, the “primary particle” is a particle in which no grain boundary appears when observed in a field of view of 5000 to 20000 magnification using a scanning electron microscope (SEM) or an electron back scatter diffraction (EBSD). “Average particle diameter of primary particles” means an arithmetic average value calculated after measuring particle diameters of primary particles observed in a SEM or EBSD image.
“Secondary particle” is a particle formed by aggregating a plurality of primary particles. In the present disclosure, a secondary particle in which 10 or less primary particles are aggregated will be referred to as pseudo-single particles in order to distinguish it from a conventional secondary particle formed by aggregating tens to hundreds of primary particles.
In the present disclosure, “specific surface area” is measured by the BET method, and may be specifically calculated from the nitrogen gas adsorption amount under liquid nitrogen temperature (77K) using BELSORP-mini II of BEL Japan.
In the present disclosure, “Dmin”, “D50” and “Dmax” are particle size values of the cumulative volume distribution of the positive electrode active material measured using a laser diffraction method. Specifically, Dmin is a minimum particle size appearing in the cumulative volume distribution, D50 is a particle size when the cumulative volume amount is 50%, and Dmax is a maximum particle size appearing in the cumulative volume distribution. If the positive electrode active material is a single particle, D50 means an average particle diameter of the primary particles. In addition, when the positive electrode active material is a pseudo-single particle, D50 means an average particle diameter of particles formed by aggregating primary particles.
The particle size value of the cumulative volume distribution may be measured by, for example, dispersing the positive electrode active material in a dispersion medium, then introducing the same into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), irradiating ultrasonic waves of about 28 kHz with output of 60 W thereto, and obtaining a cumulative volume particle size distribution graph.
In the present disclosure, “consist essentially of A” indicates that the A component and any unmentioned components that do not substantially affect the basic and novel characteristics of the present disclosure are included. The basic and novel characteristics of the present disclosure include at least one of minimizing particle breakage during battery manufacturing, minimizing gas generated by such particle breakage, and minimizing the occurrence of internal cracks. A person skilled in the art may recognize the material influence of these characteristics.
As a result of repeated research to develop a positive electrode for an electrochemical device with high safety while realizing high capacity and an electrochemical device including the same, inventors of the present discloser have confirmed that the safety of a large cylindrical battery can be dramatically improved when the positive electrode active material in the form of a single particle composed of one primary particle or a pseudo-single particle, which is an aggregate of 10 or less primary particles, is used alone as a positive electrode active material.
According to one aspect, the positive electrode includes a positive electrode current collector; and a positive electrode active material layer formed on at least one side surface of the positive electrode current collector, wherein the positive electrode active material layer may include a positive electrode active material, and optionally, a conductive material and/or a binder.
The positive electrode may have a structure in which a positive electrode active material layer is formed on at least one surface or both surfaces of a long sheet-shaped positive electrode current collector, and the positive electrode active material layer may include a positive electrode active material and a binder.
Specifically, the positive electrode may be manufactured by applying a positive electrode slurry, which is prepared by dispersing a positive electrode active material, a conductive material and a binder in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methyl pyrrolidone (NMP), acetone, water or the like, on one surface or both surfaces of a long sheet-shaped positive electrode current collector, removing the solvent of the positive electrode slurry through a drying process, and then roll-pressing the same. Meanwhile, when the positive electrode slurry is applied, a positive electrode including an uncoated portion (non-coated portion) may be manufactured by not applying the positive electrode slurry to a partial area of the positive electrode current collector, for example, one end of the positive electrode current collector.
In another aspect, the positive electrode active material includes single particle-based active material particles. In one embodiment, the single particle-based active material particles may be 90 wt % or more, 95 wt % or more, 98 wt % or more, or 99 wt % or more, based on 100 wt % of the positive electrode active material. In one specific embodiment, the positive electrode active material may be composed of only the single particle-based active material particles.
In this specification, the single particle-based active material particle refers to a single particle, a pseudo-single particle, or both of them. The single particle is a particle composed of one primary particle, and the pseudo-single particle is an aggregate of 10 or less primary particles.
Conventionally, it has been common to use a spherical secondary particle in which tens to hundreds of primary particles are aggregated as a positive electrode active material of a lithium battery. However, in the case of a positive electrode active material in the form of secondary particles in which many primary particles are aggregated, particle breakage in which primary particles fall off is easy to occur in the rolling process when manufacturing a positive electrode, and cracks occur inside the particles during the charging and discharging process. When particles of the positive electrode active material are broken or cracks occur inside the particles, the contact area with the electrolyte increases, so there is a problem in that gas generation due to a side reaction with the electrolyte increases. If the gas generation inside the cylindrical battery increases, the pressure inside the battery increases and there is a risk of battery explosion. In particular, when the volume of the cylindrical battery is increased, the amount of active material inside the battery increases as the volume increases, and as a result, the amount of gas generated increases significantly, so the risk of ignition and/or explosion of the battery increases further.
In contrast, the single particle-based active material particles in the form of a single particle composed of one primary particle or a pseudo-single particle in which 10 or less primary particles are aggregated have a higher particle strength than the positive electrode active material in the existing secondary particle form in which tens to hundreds of primary particles are aggregated, so particle breakage rarely occurs during the rolling process. In addition, since the number of primary particles constituting the single-particle-based active material particle is small, the volume expansion and contraction of the primary particles during charging and discharging is small, and thus the occurrence of cracks inside the particle is significantly reduced.
Therefore, when using the single particle-based active material particles as in the present disclosure, the amount of gas generated due to particle breakage and internal cracks may be significantly reduced. Accordingly, when the single particle-based active material particles are applied to a large cylindrical battery, excellent safety may be realized.
Meanwhile, the single particle and/or pseudo-single particle is included in an amount of 95 wt % to 100 wt %, preferably 98 wt % to 100 wt %, more preferably 99 wt % to 100 wt %, further preferably 100 wt %, based on the entire weight of the positive electrode active material included in the positive electrode.
When the content of single particle and/or pseudo-single particle satisfies the above range, sufficient safety may be obtained when applied to a large-sized battery. When the positive electrode active material in the form of a secondary particle is included in an amount exceeding 5 wt % in the entire positive electrode active material, the side reaction with the electrolyte increases due to fine powder generated from the secondary particle during electrode manufacturing and charging/discharging, which may deteriorate suppression of gas generation and lower the stability improvement effect when applied to a large-sized battery.
Meanwhile, positive electrode active materials including single particles and/or pseudo-single particles according to the present disclosure may have Dmin of 1.0 μm or more, 1.1 μm or more, 1.15 μm or more, 1.2 μm or more, or 1.25 μm or more, 1.3 μm or more, or 1.5 μm or more. When the Dmin of the positive electrode active material is less than 1.0 μm, the linear pressure increases during the positive electrode rolling process, which may easily cause particle breakage and deteriorate thermal stability, making it impossible to secure sufficient thermal stability when applied to a large-sized cylindrical battery.
Meanwhile, considering resistance and power characteristics, Dmin of the positive electrode active material may be 3 μm or less, 2.5 μm or less, or 2 μm or less. If Dmin is too large, the lithium ion diffusion distance within the particles may increase, and thus the resistance and power characteristics may deteriorate.
For example, Dmin of the positive electrode active material may be 1.0 μm to 3 μm, 1.0 μm to 2.5 μm, or 1.3 μm to 2.0 μm.
Meanwhile, the positive electrode active material may have a D50 of 5 μm or less, 4 μm or less, or 3 μm or less, and may be, for example, 0.5 μm to 5 μm, preferably 1 μm to 5 μm, more preferably 2 μm to 5 μm.
The positive electrode active material in the form of single particles and/or pseudo-single particles has less lithium mobility than the positive electrode active material in the form of secondary particles because there are fewer interfaces between primary particles that serve as a diffusion path for lithium ions inside the particles, and accordingly there is a problem that the resistance increases. The increase in resistance intensifies as the size of the particles increases, and when the resistance increases, capacity and power characteristics are adversely affected. Therefore, by adjusting D50 of the positive electrode active material to 5 μm or less, it is possible to suppress an increase in resistance by minimizing the lithium ion diffusion distance inside the positive electrode active material particle.
In addition, the positive electrode active material may have Dmax of 12 μm to 17 μm, preferably 12 μm to 16 μm, and more preferably 12 μm to 15 μm. When Dmax of the positive electrode active material satisfies the above range, resistance characteristics and capacity characteristics are more excellent. If Dmax of the positive electrode active material is too large, aggregation has occurred between single particles, and the lithium movement path inside the agglomerated particles is lengthened, resulting in poor lithium mobility, which may increase resistance. Meanwhile, if Dmax of the positive electrode active material is too small by excessive crushing process, Dmin may decrease to less than 1 μm, which causes particle breakage during rolling and deteriorates thermal stability.
Meanwhile, the positive electrode active material may have a particle size distribution (PSD) represented by Formula 1 below of 3 or less, preferably 2 to 3, more preferably 2.3 to 3.
particle size distribution (PSD)=(Dmax−Dmin)/D50 Formula 1:
When the positive electrode active material has the above particle size distribution, the electrode density of the positive electrode may be properly maintained, and particle breakage and resistance increase may be effectively suppressed.
Meanwhile, the positive electrode active material may have an average particle diameter of the primary particles of 5 μm or less, 4 μm or less, 3 μm or less, or 2 μm or less, and may be, for example, 0.5 μm to 5 μm, preferably 1 μm to 5 μm, more preferably 2 μm to 5 μm. When the average particle diameter of the primary particles satisfies the above range, the positive electrode active material in the form of a single particle and/or pseudo-single particle having excellent electrochemical properties may be formed. If the average particle diameter of the primary particles is too small, the number of aggregations of the primary particles forming the positive electrode active material increases, reducing the effect of suppressing particle breakage during rolling. If the average particle diameter of the primary particles is too large, the lithium diffusion path may be elongated, increasing resistance and deteriorating power characteristics.
In the present disclosure, the positive electrode active material preferably has a unimodal particle size distribution. Conventionally, in order to improve the electrode density of the positive electrode active material layer, bimodal positive electrode active materials in which a large particle diameter positive electrode active material with a large average particle diameter and a small particle diameter positive electrode active material with a small average particle diameter are mixed has been used frequently. However, in the positive electrode active material in the form of single particles or pseudo-single particles, when the particle size increases, the lithium movement path lengthens and the resistance increases remarkably. Thus, when large-diameter particles are mixed and used, a problem of deterioration in capacity and power characteristics may occur. Therefore, in the present disclosure, the increase in resistance may be minimized by using a positive electrode active material having a unimodal distribution.
Meanwhile, the positive electrode active material may include lithium nickel-containing oxide, and specifically, may include lithium nickel-containing oxide containing 80 mol % or more of Ni based on the total number of moles of transition metal. Preferably, the lithium nickel-containing oxide may include 80 mol % or more and less than 100 mol % of Ni, 82 mol % or more and less than 100 mol % of Ni, or 83 mol % or more and less than 100 mol % of Ni. When the lithium nickel-containing oxide having a high Ni content is used as above, high capacity may be realized.
More specifically, the positive electrode active material may include a lithium nickel-containing oxide represented by the following [Chemical Formula 1].
LiaNibCocM1dM2eO2 [Chemical Formula 1]
In Chemical Formula 1, M1 may be Mn, Al or a combination thereof, and may be preferably Mn or Mn and Al.
M2 is at least one selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta and Nb, preferably at least one selected from the group consisting of Zr, Y, Mg, and Ti, more preferably Zr, Y or a combination thereof. The M2 element is not necessarily included, but when included in an appropriate amount, it may play a role of promoting grain growth or improving crystal structure stability during sintering.
The a represents the molar ratio of lithium in the lithium nickel-containing oxide, and may be 0.8≤a≤1.2, 0.85≤a≤1.15, or 0.9≤a≤1.2. When the molar ratio of lithium satisfies the above range, a crystal structure of lithium nickel-containing oxide may be stably formed.
The b represents the molar ratio of nickel among all metals except lithium in the lithium nickel-containing oxide, and may be 0.8≤b<1, 0.82≤b<1, 0.83≤b<1, 0.85≤b<1, 0.88≤b<1 or 0.90≤b<1. When the molar ratio of nickel satisfies the above range, it is possible to realize high capacity by exhibiting high energy density.
The c represents the molar ratio of cobalt among all metals except lithium in the lithium nickel-containing oxide, and may be 0<c<0.2, 0<c<0.18, 0.01≤c≤0.17, 0.01≤c≤0.15, 0.01≤c≤0.12 or 0.01≤c≤0.10. When the molar ratio of cobalt satisfies the above range, good resistance characteristics and power characteristics may be implemented.
The d represents the molar ratio of M1 element among all metals except lithium in the lithium nickel-containing oxide, and may be 0<d<0.2, 0<d<0.18, 0.01≤d≤0.17, 0.01≤d≤0.15, 0.01≤d≤0.12, or 0.01≤d≤0.10. When the molar ratio of M1 element satisfies the above range, the structural stability of the positive electrode active material is excellent. The e represents the molar ratio of M2 element among all metals except for lithium in the lithium nickel-containing oxide, and may be 0≤e≤0.1 or 0≤e≤0.05.
Meanwhile, the positive electrode active material according to the present disclosure may further include, if necessary, a coating layer including at least one coating element selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb. Mo, Sr, Sb, Bi, Si and S on the surface of the lithium nickel-containing oxide particle. Preferably, the coating element may be Al, B, Co, or a combination thereof.
When the coating layer is present on the surface of lithium nickel-containing oxide particles, contact between the electrolyte and the lithium nickel-containing oxide is suppressed by the coating layer, thereby reducing transition metal elution or gas generation due to side reactions with the electrolyte.
The positive electrode active material may be included in an amount of 80 wt % to 99 wt %, preferably 85 wt % to 99 wt %, more preferably 90 wt % to 99 wt %, based on the total weight of the positive electrode active material layer.
Meanwhile, as the positive electrode current collector, various positive electrode current collectors used in the art may be used. For example, stainless steel, aluminum, nickel, titanium, calcined carbon or aluminum, or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like may be used as the positive electrode current collector. The positive electrode current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the positive electrode current collector to increase adhesion of the positive electrode active material. The positive electrode current collector may be used in various forms of, for example, film, sheet, foil, net, porous material, foam, or nonwoven fabric.
Meanwhile, in one embodiment of the present disclosure, all or some of the single particle-based active material particles may have a core-shell structure in which the particle surface is coated with a conductive coating layer. The conductive coating layer may cover at least some or all of the particles. The conductive coating layer includes conductive nanomaterials.
The single particle-based active material particle has a problem in that the electrical conductivity is lowered because the resistance is higher than that of the conventional secondary particle type positive electrode active material and the contact area with the conductive material is small. When an excessive amount of conductive material is added to improve electrical conductivity, aggregation occurs in the positive electrode slurry, resulting in increased viscosity, which causes poor coating properties. Therefore, in order to implement smooth coating properties, the viscosity of the positive electrode slurry must be lowered by reducing the solid content. However, if the solid content in the positive electrode slurry decreases, the active material content decreases, which may deteriorate the capacity characteristics. In the present disclosure, in order to solve this problem, the surface of the single particle-based active material is coated with a conductive nanomaterial, so that excellent electrical conductivity may be realized without adding a separate conductive material to the positive electrode slurry.
In one embodiment of the present disclosure, when the single particle-based active material coated with a conductive nanomaterial is applied as the positive electrode active material, the positive electrode active material layer may not include a conductive material on a portion other than the conductive coating layer. Since there is no need to additionally use a conductive material that causes aggregation of the positive electrode slurry as described above, the viscosity of the positive electrode slurry may be reduced, the solid content may be decreased, and the electrode coating process efficiency and electrode adhesion may be improved.
In the present disclosure, the conductive nanomaterial may be a conductive material having a nano size so as to be smoothly coated on particles, and the type is not particularly limited. For example, the conductive nanomaterial may be a carbon nanotube, carbon nanoparticle, or the like.
The conductive nanomaterial may have various shapes, and may be, for example, spherical, flaky, or fibrous.
Meanwhile, the conductive coating layer may be formed by mixing single particle-based active material particles, which are a core part, and a conductive nanomaterial, and then thermally treating the mixture. At this time, the mixing may be performed as solid mixing or liquid mixing.
In one embodiment of the present disclosure, the positive electrode active material layer contains flake graphite. When using the single particle-based active material as the positive electrode active material, if the positive electrode active material layer contains flake graphite, in the case of rolling the positive electrode active material layer, the sliding effect of the flake graphite on the positive electrode active material is provided to improve the rolling characteristics of the electrode, and the porosity of the electrode may be lowered to a desired level. Accordingly, stability, initial resistance characteristics, and charge/discharge efficiency of a battery to which the positive electrode according to the present disclosure is applied may be improved.
In one embodiment of the present disclosure, the flake graphite may be included in an amount of 0.1 wt % to 5 wt %, preferably 0.1 wt % to 3 wt %, based on 100 wt % of the positive electrode active material layer.
When the content of flake graphite satisfies the above range, the positive electrode rolling characteristics are improved and excellent electrode density may be realized. If the content of flake graphite is too small, the effect of improving the rolling properties is insignificant, and if it is too large, it may cause an increase in slurry viscosity and decrease in phase stability, and resistance may increase due to a decrease in electrode uniformity through coupling with a conductive material.
Meanwhile, the flake graphite used in the present disclosure may have an average particle diameter of 1 μm to 20 μm, preferably 2 μm to 10 μm, more preferably 3 μm to 5 μm, but is not limited thereto. If the size of the flake graphite is too small, it is difficult to realize the desired porosity, and the current density may be lowered, resulting in lower capacity. At this time, the average particle diameter of the flake graphite may be measured using a laser diffraction method (ISO 13320).
In addition, the flake graphite may have an aspect ratio of 0.1 to 500, preferably 1 to 100, more preferably 1 to 30. When the aspect ratio of flake graphite satisfies the above range, the effect of lowering electrode resistance by improving conductivity occurs.
In addition, the flake graphite may have a density of 2.0 g/cm3 to 2.5 g/cm3, preferably 2.1 g/cm3 to 2.4 g/cm3, more preferably 2.2 g/cm3 to 2.3 g/cm3.
Meanwhile, in the present disclosure, the porosity of the positive electrode active material layer may be 15% to 23%, preferably 17% to 23%, more preferably 18% to 23%. When the porosity of the positive electrode active material layer satisfies the above range, the electrode density increases to realize excellent capacity and the resistance decreases. If the porosity is too low, the electrolyte impregnability is low, and lithium precipitation may occur due to non-impregnation of the electrolyte. If the porosity is too high, the contact between the electrodes is not good, which increases the resistance and decreases the energy density, so the capacity improvement effect is insignificant.
The porosity value of the positive electrode active material layer may be achieved i) by the positive electrode active material containing single particle-based active material particles and ii) by adding flake graphite to the positive electrode active material.
In implementing a high loading electrode with a relatively high loading amount of the positive electrode active material, when using a positive electrode active material in the form of a single particle or pseudo-single particle as in the present disclosure, particle breakage of the active material during rolling is significantly reduced compared to the conventional positive electrode active material in the form of a secondary particle, and damage to the positive electrode current collector (Al foil) is reduced, so rolling is possible with a relatively high linear pressure. Therefore, the porosity of the positive electrode active material layer may be decreased to the numerical range as described above, so the energy density may be increased.
In addition, if the positive electrode active material layer contains flake graphite as in the present disclosure, the flake graphite may provide a sliding effect during rolling and fill the pores of the positive electrode active material layer, so the porosity of the positive electrode active material layer may be reduced to the above numerical range.
In addition, the positive electrode may have a loading amount of 570 mg/25 cm2 or more, preferably 600 mg/25 cm2 to 800 mg/25 cm2, more preferably 600 mg/25 cm2 to 750 mg/25 cm2. Specifically, in the lithium secondary battery according to the present disclosure, the loading amount of the positive electrode may be secured in a relatively high level because the rolling characteristics of the electrode are improved by applying a single particle and/or pseudo-single particle positive electrode active material and flake graphite, and through this, high-capacity characteristics may be implemented.
In one embodiment of the present disclosure, the positive electrode active material layer may further include a conductive material. The conductive material is used to impart conductivity to the electrode, and any material that does not cause chemical change inside the battery and has electronic conductivity may be used without particular limitations. Specific examples may include graphite such as natural graphite or artificial graphite; carbon-containing materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, or carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers of polyphenylene derivatives and the like, which may be used alone or as a mixture. The conductive material may be typically included in an amount of 1 wt % to 30 wt %, preferably 1 wt % to 20 wt %, more preferably 1 wt % to 10 wt %, based on the total weight of the positive electrode active material layer.
In one specific embodiment of the present disclosure, the conductive material may include carbon nanotube.
In one embodiment of the present disclosure, the positive electrode active material may include a multi-wall carbon nanotube having a large specific surface area and a small wall number as a conductive material. The multi-wall carbon nanotube may be included in an amount of 50 wt % or more, 70 wt % or more, 90 wt % or more, or 99 wt % or more, based on 100 wt % of the conductive material. In a specific embodiment of the present disclosure, the conductive material may include only the multi-walled carbon nanotube.
In the present disclosure, the multi-wall carbon nanotube has a BET specific surface area of 300 m2/g to 500 m2/g. The multi-wall carbon nanotube is referred to as ‘new CNT’ in order to be distinguished from the conventional one.
The carbon nanotube (conventional CNT) commonly used in the art had a BET specific surface area of less than 300 m2/g. The SEM images and physical properties (
As can be seen from the SEM images, the new CNT applied to the present disclosure is a bundled type and has a multi-wall structure, but has a higher BET and a smaller wall number and diameter than the conventional CNT.
In the case of using the positive electrode active material in the form of a secondary particle, sufficient electrical conductivity could be achieved even if the existing CNT was used at a level of 0.4 wt % to 0.6 wt %. However, the single particle or pseudo-single particle positive electrode active material has higher resistance, compared to the conventional secondary particle type positive electrode active material, and the contact area with the conductive material is small, so the electrical conductivity is low. Thus, in order to realize sufficient electrical conductivity using the existing CNT with a BET specific surface area of less than 300 m2/g, the content of the conductive material must be 0.9 wt % or more.
Through the graphs, it may be understood that when a single particle or pseudo-single particle is applied as the positive electrode active material, the usage amount of conductive material should increase compared to the case of applying an existing positive electrode active material in the form of a secondary particle.
However, when the content of carbon nanotube is increased to 0.9 wt % or more, aggregation occurs in the positive electrode slurry, resulting in an increase in viscosity, and thus coating properties deteriorate. Therefore, in order to implement smooth coating properties, the viscosity of the positive electrode slurry must be lowered by reducing the solid content in the positive electrode slurry. However, when the solid content in the positive electrode slurry decreases, the content of active material decreases and the capacity characteristics deteriorate.
As a result of repeated research to solve this problem, the inventors of the present disclosure have found that when a carbon nanotube with a BET specific surface area of 300 m2/g to 500 m2/g is applied as a conductive material together with a positive electrode active material, which is a single particle-based active material particle, sufficient electrical conductivity can be secured with only a relatively small amount of carbon nanotube, and accordingly, the slurry viscosity can be maintained low even when the solid content of the positive electrode slurry is formed as high as 70 wt % to 80 wt %.
Specifically, the carbon nanotube used in the present disclosure may be a multi-wall carbon nanotube having a BET specific surface area of 300 m2/g to 500 m2/g, preferably 300 m2/g to 450 m2/g. When the BET specific surface area satisfies the above range, sufficient electrical conductivity may be secured even with a small amount of carbon nanotube.
In addition, the carbon nanotube may be a multi-wall carbon nanotube having a wall number of 2 to 8, preferably 2 to 6, more preferably 3 to 6.
In addition, the carbon nanotube may have a diameter of 1 nm to 8 nm, preferably 3 nm to 8 nm, more preferably 3 nm to 6 nm.
The carbon nanotube may be included in an amount of 0.7 wt % or less, preferably 0.3 wt % to 0.7 wt %, more preferably 0.4 wt % to 0.6 wt %, based on the total weight of the positive electrode active material layer. When the content of the carbon nanotube satisfies the above range, sufficient electrical conductivity may be achieved, and the solid content in the positive electrode slurry may be maintained high, so that the content of the positive electrode active material may be high in the positive electrode active material layer and, as a result, excellent capacity characteristics may be implemented.
The table shown in
The binder serves to improve the attachment among the particles of the positive electrode active material and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples of the binder include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoro rubber, or various copolymers thereof, which may be used alone or as a mixture. The binder may be included in an amount of 1 wt % to 30 wt %, preferably 1 wt % to 20 wt %, more preferably 1 wt % to 10 wt %, based on the total weight of the positive electrode active material layer.
Another aspect of the present disclosure relates to an electrode assembly including the positive electrode, and a battery including the electrode assembly. The electrode assembly includes a negative electrode and a positive electrode, and the positive electrode has the above-described characteristics.
In the electrode assembly, for example, a separator may be stacked to be interposed between the negative electrode and the positive electrode to form a stacked or stacked/folded structure, or may be wound to form a jelly-roll structure. In addition, when the jelly-roll structure is formed, a separator may be additionally placed on the outer side in order to prevent the negative electrode and the positive electrode from contacting each other.
The negative electrode includes a negative electrode current collector; and a negative electrode active material layer formed on at least one side surface of the negative electrode current collector. The negative electrode may have a structure in which a negative electrode active material layer is formed on one surface or both surfaces of a long sheet-shaped negative electrode current collector, and the negative electrode active material layer may include a negative electrode active material, a conductive material, and a binder.
Specifically, the negative electrode may be manufactured by coating a negative electrode slurry, which is prepared by dispersing a negative electrode active material, a conductive material and a binder in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, on one surface or both surfaces of a long sheet-shaped negative electrode current collector, removing the solvent of the negative electrode slurry through a drying process, and then roll-pressing. When the negative electrode slurry is coated, a negative electrode having an uncoated portion may be manufactured by not applying the negative electrode slurry to a partial area of the negative electrode current collector, for example, one end of the negative electrode current collector.
As the negative electrode active material, a compound capable of reversible intercalation and de-intercalation of lithium may be used. Specific examples of the negative electrode active material include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, or amorphous carbon; silicon-containing materials such as Si, Si-Me alloy (where Me is at least one selected from the group consisting of Al, Sn, Mg, Cu, Fe, Pb, Zn, Mn, Cr, Ti, and Ni), SiOy (where 0<y<2), or Si—C composites; lithium metal thin film; metal materials capable of being alloyed with lithium, such as Sn or Al; and the like, which may be used alone or as a mixture.
In the present disclosure, the negative electrode may include a silicon-containing negative electrode active material. The silicon-containing negative electrode active material may be a Si, Si-Me alloy (where Me is one selected from the group consisting of Al, Sn, Mg, Cu, Fe, Pb, Zn, Mn, Cr, Ti, and Ni), SiOy (here, 0<y<2), Si—C composites, or a combination thereof, and may be preferably SiOy (here, 0<y<2). Since the silicon-containing negative electrode active material has a high theoretical capacity, capacity characteristics may be improved when the silicon-containing negative electrode active material is included.
The silicon-containing negative electrode active material may be doped with Mb metal, and in this case, the Mb metal may be a Group 1 metal element or a Group 2 metal element, and specifically, may be Li, Mg, or the like. Specifically, the silicon-containing negative electrode active material may be Si, SiOy (here, 0<y<2), Si—C composites, or the like, doped with Mb metal. In the case of the metal-doped silicon-containing negative electrode active material, the active material capacity is somewhat lowered due to the doping element, but high energy density may be realized due to its high efficiency.
In
The silicon-containing negative electrode active material may further include a carbon coating layer on the particle surface. At this time, the carbon coating amount may be 20 wt % or less, preferably 1 wt % to 20 wt %, based on the total weight of the silicon-containing negative electrode active material. The carbon coating layer may be formed through a method such as dry coating, wet coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD).
In one embodiment of the present disclosure, the silicon-containing negative electrode active material may have a capacity of 1000 mAh/g to 4000 mAh/g, and an initial efficiency of about 60% to 95%.
In another embodiment of the present disclosure, D50 of the silicon-containing negative electrode active material may be 3 μm to 8 μm, and Dmin to Dmax may be included in the range of 0.5 μm to 30 μm.
The negative electrode, if necessary, may further include a carbon-containing negative electrode active material as a negative electrode active material. The carbon-containing negative electrode active material may be, for example, artificial graphite, natural graphite, graphitized carbon fiber, amorphous carbon, soft carbon, hard carbon, or the like, but is not limited thereto.
When using a mixture of the silicon-containing negative electrode active material and the carbon-containing negative electrode active material as the negative electrode active material, the mixing ratio of the silicon-containing negative electrode active material and the carbon-containing negative electrode active material may be 1:99 to 20:80, preferably 1:99 to 15:85, more preferably 1:99 to 10:90, in weight ratio.
The negative electrode active material may be included in an amount of 80 wt % to 99 wt %, preferably 85 wt % to 99 wt %, more preferably 90 wt % to 99 wt %, based on the total weight of the negative electrode active material layer.
If necessary, the negative electrode active material may further include at least one selected from lithium metal and metal materials capable of alloying with lithium, such as Sn or Al.
As the negative electrode current collector, negative electrode current collectors generally used in the art may be used, and, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon; copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.; aluminum-cadmium alloy; and the like may be used. The negative electrode current collector may typically have a thickness of 3 μm to 500 μm, and, like the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to enhance the bonding force of the negative electrode active material. For example, the negative electrode current collector may be used in various forms such as films, sheets, foils, nets, porous materials, foams, or nonwoven fabrics.
The conductive material is used to impart conductivity to the negative electrode, and any material that has electronic conductivity without causing chemical change inside the battery may be used without particular limitations. Specific examples of the conductive material include graphite such as natural graphite or artificial graphite; carbon-containing materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, or carbon nanotube; metal powders or metal fibers such as copper, nickel, aluminum, or silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives, which may be used alone or as a mixture. The conductive material may be typically included in an amount of 1 wt % to 30 wt %, preferably 1 wt % to 20 wt %, more preferably 1 wt % to 10 wt %, based on the total weight of the negative electrode active material layer.
The binder serves to improve the attachment among the particles of the negative electrode active material and the adhesion between the negative electrode active material and the negative electrode current collector. Specific examples of the binder include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, and carboxymethyl cellulose. (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoro rubber, or various copolymers thereof, and the like, which may be used alone or as a mixture. The binder may be included in an amount of 1 wt % to 30 wt %, preferably 1 wt % to 20 wt %, more preferably 1 wt % to 10 wt %, based on the total weight of the negative electrode active material layer.
The electrode assembly further includes a separator, and the separator is disposed in the electrode assembly in a manner interposed between the negative electrode and the positive electrode. The separator separates the negative electrode from the positive electrode and provides a path for lithium ion movement. Any material used as a separator in a lithium battery may be used without particular limitations.
The separator may use a porous polymer film, for example, a porous polymer film made of polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer, or a laminated structure of two or more layers thereof used. In addition, conventional porous non-woven fabrics, for example, non-woven fabrics made of high melting point glass fibers, polyethylene terephthalate fibers, or the like may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength.
Another aspect of the present disclosure relates to a battery including the electrode assembly. The battery includes a battery case in which the electrode assembly and an electrolyte are accommodated together. As for the battery case, any case commonly used in the art such as a pouch type or a metal can type may be selected without particular limitation.
As the electrolyte used in the present disclosure, various electrolytes usable in lithium batteries, such as organic liquid electrolyte, inorganic liquid electrolyte, solid polymer electrolyte, gel polymer electrolyte, inorganic solid electrolyte, or molten inorganic electrolyte, may be used, and the type is not particularly limited.
Specifically, the electrolyte may include an organic solvent and a lithium salt.
The organic solvent may use any material that may serve as a medium through which ions involved in the electrochemical reaction of the battery may move without particular limitation. Specifically, as the organic solvent, ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; aromatic hydrocarbon-containing solvents such as benzene or fluorobenzene; carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methylethyl carbonate (MEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC) or propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol or isopropyl alcohol; nitriles such as R-CN (R is a C2 to C20 straight-chain, branched or cyclic hydrocarbon group, and may contain a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among them, carbonate-based solvents are preferred, and a mixture of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high permittivity capable of increasing the charge and discharge performance of the battery and low-viscosity linear carbonate-based compound (e.g., ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferred.
As the lithium salt, any compound capable of providing lithium ions used in a lithium battery may be used without particular limitation. Specifically, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiCAF9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, LiB(C2O4)2 or the like may be used as the lithium salt. The concentration of the lithium salt is preferably within the range of 0.1M to 5.0M, preferably 0.1M to 3.0M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so it may exhibit excellent electrolyte performance, and lithium ions may move effectively.
In addition to the components of the electrolyte, the electrolyte may additionally include additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery. For example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexamethyl phosphate triamid, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxy ethanol, aluminum trichloride or the like may be used alone or as a mixture as the additives, without being limited thereto. The additive may be included in an amount of 0.1 wt % to 10 wt %, preferably 0.1 wt % to 5 wt %, based on the total weight of the electrolyte.
In another embodiment of the present disclosure, the positive electrode may include a loading reduction portion with a smaller loading amount of the positive electrode active material, compared to an adjacent region. If the positive electrode has such a structure, the region of the positive electrode active material portion may be increased without worrying about precipitation of lithium. Accordingly, the energy density of the electrode assembly may be improved.
Recently, in order to realize high energy density and reduce cost, development is progressing in the direction of increasing the size of the battery. Depending on the size of the battery, as the energy increases, the resistance of battery should decrease. To reduce the resistance, a method of using the current collector of the electrode as an electrode tab rather than a method of attaching an electrode tab to the electrode may be used. At this time, due to the nature of the electrode manufacturing process of applying the electrode slurry on the electrode current collector, a portion in which the loading amount is reduced occurs at the boundary between the negative electrode active material portion coated with the negative electrode slurry and the negative electrode current collector. Considering the N/P ratio, there is a possibility that metallic lithium is precipitated on the positive electrode active material portion facing the portion where the loading amount is reduced. Here, the N/P ratio is a value obtained by dividing the capacity of the negative electrode, which is calculated considering the area and capacity per mass of the negative electrode, by the capacity of the positive electrode, which is obtained considering the area and capacity per mass of the positive electrode, and generally has a value of 1 or more. That is, the capacity of the negative electrode is adjusted large. For reference, if the N/P ratio is less than 1, metallic lithium is likely to be precipitated during charging and discharging, which causes rapid deterioration in safety of the battery during high rate charging and discharging. In other words, the N/P ratio has a significant effect on the safety and capacity of the battery. Due to the risk of metal lithium precipitation as described above, the positive electrode active material portion cannot be located on the portion of the positive electrode facing the portion where the loading amount of the negative electrode is reduced. This causes the energy density of the battery not to increase. Accordingly, in the present disclosure, the energy density is improved by increasing the region of the positive electrode active material portion.
Referring to
The negative electrode 400 includes a negative electrode current collector 410 and a negative electrode active material portion 420 formed by coating a negative electrode active material on the negative electrode current collector 410. In particular, as shown in the drawings, the negative electrode active material may be coated on both surfaces of the negative electrode current collector 410 to form the negative electrode active material portion 420. In addition, in the negative electrode current collector 410, a negative electrode uncoated portion 430 to which the negative electrode active material is not applied extends in the first direction d1. The negative electrode uncoated portion 430 extends along one end of the wound negative electrode 400. In addition, the negative electrode uncoated portion 430 extends beyond the separator 600 in the first direction d1. Accordingly, the negative electrode uncoated portion 430 may be exposed at one end in the first direction of the jelly-roll structure 300S.
The positive electrode 500 includes a positive electrode current collector 510 and a positive electrode active material portion 520 formed by coating a positive electrode active material on the positive electrode current collector 510. In particular, as shown in the drawings, the positive electrode active material may be coated on both surfaces of the positive electrode current collector 510 to form the positive electrode active material portion 520. Also, in the positive electrode current collector 510, a positive electrode uncoated portion 530 to which the positive electrode active material is not applied extends in the second direction d2. The positive electrode uncoated portion 530 extends along one end of the wound positive electrode 500. In addition, the positive electrode uncoated portion 530 extends beyond the separator 600 in the second direction d2. Accordingly, the positive electrode uncoated portion 530 may be exposed at one end in the second direction of the jelly-roll structure 300S.
Here, first direction d1 and second direction d2 are directions opposite to each other. Also, the first direction d1 and the second direction d2 may be directions parallel to the height direction of the jelly-roll structure 300S.
The electrode assembly 300 according to this embodiment has a structure in which a separate electrode tab is not attached, but the negative electrode uncoated portion 430 of the negative electrode current collector 410 and the positive electrode uncoated portion 530 of the positive electrode current collector 510 themselves are used as electrode tabs in order to reduce resistance.
Although not shown in the drawings, the negative electrode uncoated portion 430 and/or the positive electrode uncoated portion 530 may have substantially the same structure of the uncoated portion of the electrode described above.
In one embodiment, the positive electrode active material portion 520 includes a loading reduction portion 500D having a smaller loading amount of positive electrode active material than an adjacent area, and the loading reduction portion 500D is located at one end in the first direction d1 of the positive electrode 500. Also, more specifically, in the loading reduction portion 500D, the loading amount of the positive electrode active material may gradually decrease in the first direction d1.
Here, the loading amount means the amount of active material applied per unit area. In a portion having a large loading amount, a lot of negative electrode active material or positive electrode active material is applied to the unit area, so the negative electrode active material portion or the positive electrode active material portion may have a relatively greater thickness. In a portion having a small loading amount, a small amount of negative electrode active material or positive electrode active material is applied to the unit area, so the negative electrode active material portion or the positive electrode active material portion may have a relatively smaller thickness.
The active material portion may be formed by applying a slurry containing an active material. In this process, a boundary portion having a gradually decreasing loading amount may be formed between the uncoated portion and the active material portion.
Specifically, the negative electrode active material portion 420 may include a negative electrode boundary portion 420B forming a boundary between the negative electrode active material portion 420 and the negative electrode uncoated portion 430. The loading amount of the negative electrode boundary portion 420B may decrease in a direction toward the negative electrode uncoated portion 430.
Similarly, the positive electrode active material portion 520 may include a positive electrode boundary portion 520B forming a boundary between the positive electrode active material portion 520 and the positive electrode uncoated portion 530. The loading amount of the positive electrode boundary portion 520B may decrease in a direction toward the positive electrode uncoated portion 530.
The negative electrode boundary portion 420B or the positive electrode boundary portion 520B in which the loading amount gradually decreases as above is naturally generated in the process of applying the slurry containing the active material to the negative electrode current collector 410 or the positive electrode current collector 510.
In this case, in a region corresponding to the positive electrode boundary portion 520B, based on a direction perpendicular to the second direction d2, the amount of the positive electrode active material may be smaller than the amount of the negative electrode active material. Since the N/P ratio has a value greater than 1, the problem of precipitation of metallic lithium does not occur.
However, there is a problem in a region corresponding to the negative electrode boundary portion 420B. In the region corresponding to the negative electrode boundary portion 420B, based on a direction perpendicular to the first direction d1, the amount of the negative electrode active material may be smaller than the amount of the positive electrode active material. This may cause a problem of precipitation of metallic lithium because the N/P ratio has a value smaller than 1.
Accordingly, in this embodiment, the loading reduction portion 500D is provided on the positive electrode 500, and the negative electrode active material portion 420 may be located in a portion corresponding to the loading reduction portion 500D based on a direction perpendicular to the first direction d1. More specifically, the negative electrode boundary portion 420B may be located at a portion corresponding to the loading reduction portion 500D based on a direction perpendicular to the first direction d1.
The loading reduction portion 500D having a smaller loading amount of positive electrode active material than adjacent areas is provided at a position corresponding to the negative electrode boundary portion 420B having a gradually decreasing loading amount, so that the region where the positive electrode active material is applied may be increased without worrying about lithium precipitation. In particular, the loading amount of the positive electrode active material may gradually decrease in the loading reduction portion 500D along the first direction d1, corresponding to the shape of the negative electrode boundary portion 420B in which the loading amount gradually decreases in a direction toward the negative electrode uncoated portion 430. Therefore, it is possible to maintain a high N/P ratio of the negative electrode 400 and the positive electrode 500 in the region where the negative electrode boundary portion 420B is formed, thereby preventing lithium precipitation.
Hereinafter, a method for manufacturing an electrode assembly according to an embodiment of the present disclosure will be described in detail with reference to
Referring to
Specifically, the negative electrode active material portion 420 may be formed by applying the negative electrode active material to extend along the third direction d3. In addition, a plurality of negative electrode active material portions 420 may be located to be spaced apart along the fourth direction d4 by spacing the coated portions along the fourth direction d4 perpendicular to the third direction d3. That is, the coating process may be performed so that the negative electrode uncoated portion 430 is positioned between the plurality of negative electrode active material portions 420.
Here, the third direction d3 and the fourth direction d4 are directions for explanation based on the negative electrode sheet 400S, and are directions unrelated to the first direction d1 and the second direction d2 in the jelly-roll structure 300S described above.
After that, a step of manufacturing a negative electrode 400 by slitting the negative electrode uncoated portion 430 and the negative electrode active material portion 420 may be followed.
Referring to
When forming the negative electrode active material portion 420, a slurry containing the negative electrode active material may be applied on the negative electrode current collector 410. In the process of applying the slurry, a negative electrode boundary portion 420B having a loading amount decreasing in a direction toward the negative electrode uncoated portion 430 may be formed at the boundary between the negative electrode active material portion 420 and the negative electrode uncoated portion 430.
Referring to
Specifically, the positive electrode active material portion 520 may be formed by applying the positive electrode active material to extend along the third direction d3. In addition, a plurality of positive electrode active material portions 520 may be located to be spaced apart by adjusting the coating interval along the fourth direction d4 perpendicular to the third direction d3. That is, the coating process may be performed so that the positive electrode uncoated portion 530 is located between the plurality of positive electrode active material portions 520.
Here, third direction d3 and fourth direction d4 are directions for description based on the positive electrode sheet 500S, and are directions unrelated to the first direction d1 and the second direction d2 in the jelly-roll structure 300S described above.
After that, a step of manufacturing a positive electrode 500 by slitting the positive electrode uncoated portion 530 and the positive electrode active material portion 520 may be followed.
Referring to
When forming the positive electrode active material portion 520, a slurry containing the positive electrode active material may be applied on the positive electrode current collector 510. In the process of applying the slurry, a positive electrode boundary portion 520B having a loading amount decreasing in a direction toward the positive electrode uncoated portion 530 may be formed at the boundary between the positive electrode active material portion 520 and the positive electrode uncoated portion 530.
Referring to
Referring to
In the step of manufacturing the positive electrode 500, the loading reduction area 500DA of the positive electrode active material portion 520 is slit. The slitted loading reduction area 500DA forms a loading reduction portion 500D having a smaller loading amount of the positive electrode active material than the adjacent area in the jelly-roll structure 300S shown in
Specifically, a loading reduction area 500DA having a smaller loading amount of the positive electrode active material than the adjacent area is formed in the positive electrode active material portion 520 formed on the positive electrode sheet 500S. As shown in
That is, in applying the slurry containing a positive electrode active material, by forming the loading reduction area 500DA and slitting the center portion 500C of the loading reduction area 500DA, several positive electrodes 500 having the loading reduction portion 500D may be manufactured.
Referring to
Referring to
In addition, as the center portion 500C of the loading reduction area 500DA is slitted, the loading amount of the positive electrode active material in the loading reduction portion 500D may gradually decrease along the first direction d1.
In addition, in the jelly-roll structure 300S, the negative electrode active material portion 420 may be located at a portion corresponding to the loading reduction portion 500D based on a direction perpendicular to the first direction d1. More specifically, in the jelly-roll structure 300S, the negative electrode boundary portion 420B may be located at a portion corresponding to the loading reduction portion 500D based on a direction perpendicular to the first direction d1.
The corresponding positional relationship between the loading reduction portion 500D and the negative electrode boundary portion 420B has already been described above and thus will not be described again.
Hereinafter, with reference to
Referring to
The negative electrode 700 may include a negative electrode current collector 710, a negative electrode active material portion 720, and a negative electrode uncoated portion 730. In addition, the negative electrode uncoated portion 730 may extend in the first direction d1, and the negative electrode active material portion 720 may include a negative electrode boundary portion 720B that forms a boundary between the negative electrode active material portion 720 and the negative electrode uncoated portion 730 and has a gradually decreasing loading amount.
Referring to
Meanwhile, referring to
Referring to
After that, the negative electrode 700 and the positive electrode 800 manufactured as above may be wound together with the separator 900 to manufacture an electrode assembly 600 according to the comparative example.
That is, the electrode assembly 600 according to the comparative example may have a structure similar to that of the electrode assembly 300 according to this embodiment, except for the loading reduction portion 500D (see
Referring to
Meanwhile, referring to
Accordingly, the positive electrode active material portion 520 may be formed as much as the region A1, and the region A2 in which the positive electrode active material portion 520 cannot be formed may be reduced. For example, the width of the positive electrode 500 in the height direction compared to the width of the negative electrode 400 in the height direction may be increased to 98% or more.
If the region A1 of
Another aspect of the present disclosure relates to a cylindrical battery, which includes a jelly-roll type electrode assembly having a structure in which a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are wound in one direction; a cylindrical battery housing in which the electrode assembly is accommodated; and a battery cap serving as a sealing body disposed at the upper portion of the battery housing to seal the battery housing. Here, the positive electrode is prepared according to the present disclosure and includes single particle-based active material particles having an average particle diameter D50 of 5 μm or less as the positive electrode active material. The cylindrical battery may further include an electrolyte, and the above description may be referred to for the electrolyte.
The electrode assembly may have a stack type, stack/folding type, or jelly-roll type structure as described above. In one specific embodiment of the present disclosure, in the electrode assembly, the positive electrode may have a loading reduction portion as described above.
In the case of a conventional cylindrical battery, current is concentrated on a strip-shaped electrode tab, resulting in great resistance, high heat generation, and poor current collection efficiency.
As the demand for high-capacity batteries increases with the recent development of electric vehicle technology, the development of bulky large-sized cylindrical batteries is required. In the case of a conventional small cylindrical battery generally used in the art, that is, a cylindrical battery having a form factor of 1865 or 2170, resistance or heat generation does not seriously affect battery performance because the capacity is small. However, when the specifications of the conventional small cylindrical battery are applied as they are to a large cylindrical battery, a serious problem may occur in battery safety.
As the size of the battery increases, the amount of heat and gas generated inside the battery also increases, and the temperature and pressure inside the battery rise due to such heat and gas, which may cause the battery to ignite or explode. In order to prevent this, heat and gas inside the battery must be properly discharged to the outside, and for this, the cross-sectional area of the battery, which serves as a passage for discharging heat to the outside of the battery, must increase to match the increase in volume. However, in general, since the increase in cross-sectional area does not reach the increase in volume, as the size of the battery increases, the amount of heat generated inside the battery increases, resulting in problems such as increased risk of explosion and reduced output. In addition, when rapid charging is performed at a high voltage, a large amount of heat is generated around the electrode tab for a short period of time, and the battery may ignite. Accordingly, the present disclosure proposes a cylindrical battery having a high safety while having a large volume to implement a high capacity.
In addition, since a high loading electrode to which the positive electrode active material in the form of single particle or pseudo-single particle is applied may be applied to the cylindrical battery, the initial resistance characteristics and charge/discharge efficiency of the cylindrical battery may be improved.
The cylindrical battery according to the present disclosure significantly reduces gas generation compared to the prior art by applying a positive electrode active material in the form of single particle or pseudo-single particle. Accordingly, even a large cylindrical battery having a form factor ratio of 0.4 or more may exhibit excellent safety.
The cylindrical battery according to the present disclosure may preferably be a battery having a tab-less structure that does not include an electrode tab, but is not limited thereto.
In the battery of the tab-less structure, for example, each of the positive electrode and the negative electrode includes an uncoated portion on which an active material layer is not formed, and may have a structure in which the positive electrode uncoated portion and the negative electrode uncoated portion are respectively located at the upper and lower ends of the electrode assembly, a collector plate is coupled to the positive electrode uncoated portion and the negative electrode uncoated portion, and the collector plate is connected to an electrode terminal.
When the cylindrical battery is formed in a tab-less structure as described above, since the concentration of current is less than that of the conventional battery equipped with an electrode tab, heat generation inside the battery may be effectively reduced, thereby improving the thermal safety of the battery.
Hereinafter, the present disclosure will be described in more detail through specific examples.
A single particle type positive electrode active material Li[Ni0.9Co0.06Mn0.03Al0.01]O2 having a unimodal particle size distribution with an average particle diameter D50 of 3 μm:carbon nanotube:PVDF binder were mixed in N-methyl pyrrolidone at a weight ratio of 97.8:0.6:1.6 to prepare a positive electrode slurry. The positive electrode slurry was coated on one surface of an aluminum current collector sheet, dried at 120° C., and then rolled to prepare a positive electrode.
A negative electrode active material (graphite:SiO=95:5 mixture by weight):conductive material (super C):styrene-butadiene rubber (SBR):carboxymethyl cellulose (CMC) were mixed in water at a weight ratio of 96:2:1.5:0.5 to prepare a negative electrode slurry. The negative electrode slurry was coated on one surface of a copper current collector sheet, dried at 150° C., and then rolled to prepare a negative electrode.
A separator was interposed between the positive electrode and the negative electrode prepared as above, stacked in the order of separator/positive electrode/separator/negative electrode, and then wound to prepare a jelly-roll type electrode assembly. The electrode assembly prepared as described above was inserted into a cylindrical battery can, and an electrolyte was injected thereto to prepare a 4680 cell.
A 4680 cell was manufactured in the same manner as in Example 1, except that secondary particle type Li[Ni0.9Co0.05Mn0.04Al0.01]O2 having a bimodal particle size distribution with a large particle average diameter D50 of 9 μm and a small particle average diameter D50 of 4 μm was used as the positive electrode active material.
A hot box test was performed on the 4680 cells manufactured by Example 1 and Comparative Example 1.
Specifically, each of the 4680 cells manufactured by Example 1 and Comparative Example 1 was placed in a hot box chamber at room temperature, heated to 130° C. at a heating rate of 5° C./min, and maintained for 30 minutes to perform a hot box evaluation, and the temperature change of the battery over time was measured. For accurate evaluation, the hot box evaluation was performed twice on the cell of Example 1. The measurement results are shown in
Through
A positive electrode active material (composition: Li[Ni0.9Co0.06Mn0.03Al0.01]O2), which has a unimodal particle size distribution where Dmin=1.78 μm, D50=4.23 μm, and Dmax=13.1 μm and in which single particles and pseudo-single particles were mixed was prepared.
The positive electrode active material:carbon nanotube:PVDF binder were mixed in N-methyl pyrrolidone at a weight ratio of 97.8:0.6:1.6 to prepare a positive electrode slurry. The positive electrode slurry was coated on one surface of an aluminum current collector sheet, dried at 120° C., and then rolled to prepare a positive electrode.
A negative electrode active material (graphite:SiO=95:5 mixture by weight):conductive material (super C):styrene-butadiene rubber (SBR):carboxymethyl cellulose (CMC) were mixed in water at a weight ratio of 96:2:1.5:0.5 to prepare a negative electrode slurry. The negative electrode slurry was coated on one surface of a copper current collector sheet, dried at 150° C., and then rolled to prepare a negative electrode.
A separator was interposed between the positive electrode and the negative electrode prepared as above, stacked in the order of separator/positive electrode/separator/negative electrode, and then wound to prepare a jelly-roll type electrode assembly. The electrode assembly prepared as described above was inserted into a battery can, and an electrolyte was injected thereto to prepare a 4680 cell.
A 4680 cell was manufactured in the same manner as in Example 2-1, except that a positive electrode active material (composition: Li[Ni0.9Co0.06Mn0.03Al0.01]O2), which has a unimodal particle size distribution where Dmin=1.38 μm, D50=4.69 μm, and Dmax=18.5 μm and in which single particles and pseudo-single particles were mixed was used as the positive electrode active material.
A 4680 cell was manufactured in the same manner as in Example 2-1, except that a secondary particle type positive electrode active material (composition: Li[Ni0.9Co0.05Mn0.04Al0.01]O2) having a bimodal particle size distribution with a large particle average diameter D50 of 9 μm and a small particle average diameter D50 of 4 μm was used as the positive electrode active material.
A 4680 cell was manufactured in the same manner as in Example 2-1, except that a positive electrode active material (composition: Li[Ni0.9Co0.06Mn0.03Al0.01]O2), which has a unimodal particle size distribution where Dmin=0.892 μm, D50=3.02 μm, and Dmax=11 μm and in which single particles and pseudo-single particles were mixed was used as the positive electrode active material.
A hot box test was performed on the 4680 cells manufactured by Examples 2-1 and 2-2 and Comparative Examples 2-1 and 2-2.
Specifically, each of the 4680 cells manufactured by Example 2-1 and Comparative Example 2-1 was placed in a hot box chamber at room temperature, heated up to 130° C. at a heating rate of 5° C./min, and maintained for 30 minutes, and then the temperature change of the cell was measured. A case in which thermal runaway and ignition did not occur during the test was marked as Pass, and a case in which thermal runaway and/or ignition occurred was marked as Fail. Also, for the accuracy of the test, the test was performed more than twice for the cells of Examples 2-1 and 2-2.
Measurement results are shown in Table 1 below and
Referring to Table 1 and
After rolling the positive electrodes manufactured in Example 2-1 and Comparative Example 2-1, in order to check the degree of breakage of the positive electrode active material particles, the positive electrode was cut with an ion milling device and the cross section was photographed with a SEM.
Through
A positive electrode active material powder (composition: Li[Ni0.9Co0.06Mn0.03Al0.01]O2), which has a unimodal particle size distribution where Dmin=1.78 μm, D50=4.23 μm, Dmax=13.1 μm and in which single particles and pseudo-single particles were mixed, flake graphite (SFG6L), conductive material (multi-wall carbon nanotube), and PVDF binder were mixed in N-methyl pyrrolidone at a weight ratio of 96.3:1.5:0.4:1.8 to prepare a positive electrode slurry. The positive electrode slurry was coated on one surface of an aluminum current collector sheet, dried, and rolled at a linear pressure of 3.0 ton/cm to prepare a positive electrode. The porosity of the positive electrode active material layer of the positive electrode prepared as described above was measured, and the porosity was measured to be 17.5%.
A positive electrode was manufactured in the same manner as in Example 3-1, except that the positive electrode active material, flake graphite, conductive material, and binder were mixed in a weight ratio of 97.2:0.6:0.4:1.8, and the porosity of the positive electrode active material layer was measured. The porosity of the positive electrode active material layer was measured to be 19%.
A positive electrode was manufactured in the same manner as in Example 3-1, except that the positive electrode active material, flake graphite, conductive material, and binder were mixed in a weight ratio of 97.4:0.4:0.4:1.8, and the porosity of the positive electrode active material layer was measured. The porosity of the positive electrode active material layer was measured to be 20%.
A positive electrode was manufactured in the same manner as in Example 3-1, except that the positive electrode active material, flake graphite, conductive material, and binder were mixed in a weight ratio of 97.6:0.2:0.4:1.8, and the porosity of the positive electrode active material layer was measured. The porosity of the positive electrode active material layer was measured to be 21%.
A positive electrode was prepared in the same manner as in Example 3-1, except that the positive electrode slurry was prepared by mixing the positive electrode active material, conductive material, and binder in N-methyl pyrrolidone at a weight ratio of 97.8:0.4:1.8 without adding flake graphite, and the porosity of the positive electrode active material layer was measured. The porosity of the positive electrode active material layer was measured to be 24%.
A positive electrode was manufactured in the same manner as in Example 3-1 except that the positive electrode active material, conductive material, and binder were mixed in N-methyl pyrrolidone at a weight ratio of 97.8:0.4:1.8 to prepare a positive electrode slurry, and rolled at a line pressure of 2.0 ton/cm without adding flake graphite, and the porosity of the positive electrode active material layer was measured. The porosity of the positive electrode active material layer was measured to be 30%.
Experimental Example 3-1—Measurement of charge/discharge capacity and charge/discharge efficiency
Coin half-cells including the positive electrodes according to Examples 3-1 to 3-4 and Comparative Examples 3-1 and 3-2 were manufactured, charged up to 4.25V under a 0.2 C current condition, and then discharged to 2.5V under a 0.2 C current condition, and the charge capacity (mAh/g) and discharge capacity (mAh/g) of each coin half-cell were measured. The measurement results are shown in Table 2 below.
Through Table 2, it may be found that Examples 3-1 to 3-4 using an positive electrode to which flake graphite is added shows lower porosity and excellent capacity characteristics compared to Comparative Examples 3-1 to 3-2.
While charging the coin half-cells including the positive electrodes according to Example 3-3, Comparative Example 3-1, and Comparative Example 3-2 to 4.2V, resistance characteristics according to SOC were measured. The experimental results are shown in
Referring to
A separator was interposed between the positive electrode and the negative electrode according to Example 3-1, Example 3-3, and Comparative Example 3-1, and stacked in the order of separator/positive electrode/separator/negative electrode, and then wound to prepare a jelly-roll type electrode assembly. The electrode assembly prepared as described above was inserted into a cylindrical battery can, and then an electrolyte was injected thereto to manufacture a 4680 cell.
At this time, a negative electrode active material (graphite:SiO=95:5 mixture by weight):conductive material (super C):styrene-butadiene rubber (SBR):carboxymethyl cellulose (CMC) were mixed in water at a weight ratio of 96:2:1.5:0.5 to prepare a negative electrode slurry, and then the negative electrode slurry was coated on to one surface of a copper current collector sheet, dried at 150° C., and then rolled to prepare a negative electrode.
Based on one cycle in which the 4680 cell prepared as described above was charged to 4.2V at 40° C. at 0.5 C and then discharged to 2.5V at 0.5 C, 50 cycles of charge and discharge were performed, and then capacity retention and resistance increase rate (DCIR increase) were measured. The measurement results are shown in
Referring to
The present disclosure has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the scope of the disclosure will become apparent to those skilled in the art from this detailed description.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2021-0142189 | Oct 2021 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2022/016199 | 10/21/2022 | WO |
