Patent Application
20250226492
The present disclosure relates to a secondary battery, and to a battery pack that includes the secondary battery.
Various kinds of electronic equipment, including mobile phones, have been widely used. Such widespread use has promoted development of a secondary battery as a power source that is smaller in size and lighter in weight and allows for a higher energy density. The secondary battery includes a battery device contained inside an outer package member. A configuration of the secondary battery has been considered in various ways.
A secondary battery is proposed in which what is called a tabless structure is employed to thereby reduce an internal resistance and to allow for charging and discharging with a relatively large current.
The present disclosure relates to a secondary battery, and to a battery pack that includes the secondary battery.
Consideration has been given in various ways to improve performance of a secondary battery. However, there is still room for improvement in reliability of the secondary battery.
It is therefore desirable to provide a secondary battery that is superior in vibration resistance and not degraded in manufacturability.
A secondary battery according to an embodiment of the present disclosure includes an electrode wound body and a battery can. The electrode wound body includes a positive electrode and a negative electrode that are stacked on each other with a separator interposed between the positive electrode and the negative electrode and are wound around a central axis. The battery can has a substantially circular columnar outer shape in which a height direction corresponds to a direction along the central axis. The battery can contains the electrode wound body. The battery can includes a container and a cover part. The container includes a lower end part and an upper end part. The lower end part is closed by a bottom part. The upper end part is positioned on a side opposite to the lower end part in the height direction and has an opening through which the electrode wound body is passable. The cover part closes the opening of the container. Where a flattening of the electrode wound body is a ratio of a maximum diameter of the electrode wound body to a minimum diameter of the electrode wound body, the flattening of an upper part of the electrode wound body is greater than the flattening of a lower part of the electrode wound body.
According to the secondary battery of an embodiment of the present disclosure, the flattening of the upper part of the electrode wound body is greater than the flattening of the lower part of the electrode wound body. The flattening of the lower part of the electrode wound body being relatively small makes it easy for the electrode wound body to be placed into the battery can upon assembly of the secondary battery. In addition, the flattening of the upper part of the electrode wound body being great helps to prevent the electrode wound body from easily moving inside the battery can even when the secondary battery undergoes vibration. This makes it possible to prevent, for example, damage to the electrode wound body itself, and damage to a coupling part between a positive electrode current collector plate, which is joined to the electrode wound body, and an external terminal or a cover part.
The secondary battery according to an embodiment of the present disclosure thus makes it possible to achieve superior vibration resistance without degrading manufacturability.
Note that effects of the present disclosure are not necessarily limited to those described above and may include any of a series of effects described below in relation to the present disclosure.
The present disclosure is described below in further detail including with reference to the drawings according to an embodiment.
A description is given first of a secondary battery according to an embodiment of the present disclosure.
In the present embodiment, a cylindrical lithium-ion secondary battery having an outer appearance of a cylindrical shape will be described as an example. However, the secondary battery of the present disclosure is not limited to the cylindrical lithium-ion secondary battery, and may be a lithium-ion secondary battery having an outer appearance of a shape other than the cylindrical shape, or may be a battery in which an electrode reactant other than lithium is used.
Although a charge and discharge principle of the secondary battery is not particularly limited, the following description deals with a case where a battery capacity is obtained through insertion and extraction of the electrode reactant. The secondary battery includes a positive electrode, a negative electrode, and an electrolyte. In the secondary battery, to prevent precipitation of the electrode reactant on a surface of the negative electrode during charging, a charge capacity of the negative electrode is greater than a discharge capacity of the positive electrode. In other words, an electrochemical capacity per unit area of the negative electrode is set to be greater than an electrochemical capacity per unit area of the positive electrode.
Although not particularly limited in kind as described above, the electrode reactant is specifically a light metal such as an alkali metal or an alkaline earth metal. Examples of the alkali metal include lithium, sodium, and potassium. Examples of the alkaline earth metal include beryllium, magnesium, and calcium.
In the following, described as an example is a case where the electrode reactant is lithium. A secondary battery in which the battery capacity is obtained through insertion and extraction of lithium is what is called a lithium-ion secondary battery. In the lithium-ion secondary battery, lithium is inserted and extracted in an ionic state.
Specifically, the secondary battery 1 includes, inside the outer package can 11, a pair of insulating plates 12 and 13, the electrode wound body 20, a positive electrode current collector plate 24, and a negative electrode current collector plate 25, for example. The electrode wound body 20 is a structure in which a positive electrode 21 and a negative electrode 22 are stacked with a separator 23 interposed therebetween and are wound, for example. The electrode wound body 20 is impregnated with an electrolytic solution. The electrolytic solution is a liquid electrolyte. Note that the secondary battery 1 may further include a thermosensitive resistive (PTC) device, a reinforcing member, or both inside the outer package can 11.
The outer package can 11 has, for example, a hollow cylindrical structure with a lower end part and an upper end part in a Z-axis direction. The Z-axis direction is the height direction. The lower end part is closed, and the upper end part is open. Accordingly, the upper end part of the outer package can 11 is an open end part 11N, and the lower end part of the outer package can 11 is closed by a bottom part 11B having a substantially circular plate shape. Provided between the open end part 11N and the bottom part 11B is a sidewall part 11W surrounding the electrode wound body 20. The outer package can 11 includes, for example, a metal material such as iron as a constituent material. Note that a surface of the outer package can 11 may be plated with, for example, a metal material such as nickel. The insulating plate 12 and the insulating plate 13 are so opposed to each other as to allow the electrode wound body 20 to be interposed therebetween in the Z-axis direction, for example. Note that in the present specification, the open end part 11N and the vicinity thereof may be referred to as an upper part of the secondary battery 1 in the Z-axis direction, and a region where the outer package can 11 is closed and the vicinity thereof may be referred to as a lower part of the secondary battery 1 in the Z-axis direction. The open end part 11N of the outer package can 11 is closed by a battery cover 14. The battery cover 14 will be described later.
The outer package tube 50 surrounds a side surface 11WS1 that is an outer surface of the sidewall part 11W of the outer package can 11. However, the outer package tube 50 may cover a bent part 11P provided at the upper end part of the outer package can 11, as illustrated in
A washer 55 is provided in a gap between the outer package tube 50 and the bent part 11P of the outer package can 11. The washer 55 is an insulating ring member that has an opening 55K in a middle region in a plane orthogonal to the height direction. Disposed in the opening 55K is a projecting part provided in a middle region of the battery cover 14. The washer 55 may include, for example, black modified polyphenylene ether as a constituent material.
Each of the insulating plates 12 and 13 is, for example, a dish-shaped plate having a surface perpendicular to a central axis CL of the electrode wound body 20, that is, a surface perpendicular to a Z-axis in
For example, a structure in which the battery cover 14 and a safety valve mechanism 30 are crimped with a gasket 15 interposed therebetween, that is, a crimped structure 11R, is provided at the open end part 11N of the outer package can 11. The outer package can 11 is sealed by the battery cover 14, with the electrode wound body 20 and other components being contained inside the outer package can 11. The crimped structure 11R is what is called a crimp structure, and includes the bent part 11P serving as what is called a crimp part.
The battery cover 14 is a closing member that mainly closes the open end part 11N of the outer package can 11 in a state where the electrode wound body 20 and other components are contained inside the outer package can 11. The battery cover 14 includes a material similar to the material included in the outer package can 11, for example. In the middle region of the battery cover 14, provided is the projecting part that protrudes upward, i.e., in a +Z direction, for example. As a result, a peripheral region, i.e., a region other than the middle region, of the battery cover 14 is in a state of being in contact with the safety valve mechanism 30, for example.
The gasket 15 is a sealing member interposed mainly between the bent part 11P of the outer package can 11 and the battery cover 14. The gasket 15 seals a gap between the bent part 11P and the battery cover 14. Note that a surface of the gasket 15 may be coated with, for example, asphalt. The gasket 15 includes any one or more of insulating materials, for example. The insulating material is not particularly limited in kind, and examples thereof include a polymer material such as polybutylene terephthalate (PBT) or polypropylene (PP). In particular, the insulating material is preferably polybutylene terephthalate. One reason for this is that this allows the gap between the bent part 11P and the battery cover 14 to be sufficiently sealed, with the outer package can 11 and the battery cover 14 being electrically separated from each other.
The safety valve mechanism 30 is adapted to cancel the sealed state of the outer package can 11 to thereby release a pressure inside the outer package can 11, i.e., an internal pressure of the outer package can 11, on an as-needed basis, mainly upon an increase in the internal pressure. Examples of a cause of the increase in the internal pressure of the outer package can 11 include a gas generated due to a decomposition reaction of the electrolytic solution upon charging and discharging. The internal pressure of the outer package can 11 can also increase due to heating from outside.
The electrode wound body 20 is a power generation device that causes charging and discharging reactions to proceed, and is contained inside the outer package can 11. The electrode wound body 20 includes the positive electrode 21, the negative electrode 22, the separator 23, and the electrolytic solution as a liquid electrolyte.
As illustrated in
The positive electrode 21, the negative electrode 22, and the separator 23 are so wound that the separator 23 is positioned in each of an outermost wind of the electrode wound body 20 and an innermost wind of the electrode wound body 20. Further, in the outermost wind of the electrode wound body 20, the negative electrode 22 is positioned on an outer side relative to the positive electrode 21. In other words, as illustrated in
The positive electrode 21 includes a positive electrode covered region 211 in which the positive electrode current collector 21A is covered with the positive electrode active material layer 21B, and a positive electrode exposed region 212 in which the positive electrode current collector 21A is exposed without being covered with the positive electrode active material layer 21B. As illustrated in
An insulating layer 101 is preferably provided in a region including a border between the positive electrode covered region 211 and the positive electrode exposed region 212 and the vicinity of the border. As with the positive electrode covered region 211 and the positive electrode exposed region 212, the insulating layer 101 also preferably extends from the central axis side edge 21E1 to the outer winding side edge 21E2 in the electrode wound body 20. Further, the insulating layer 101 is preferably adhered to the first separator member 23A, the second separator member 23B, or both. One reason for this is that this makes it possible to prevent the positive electrode 21 and the separator 23 from becoming misaligned with each other. Further, the insulating layer 101 preferably includes a resin including polyvinylidene difluoride (PVDF). One reason for this is that when the insulating layer 101 includes PVDF, the insulating layer 101 is swollen by, for example, a solvent included in the electrolytic solution, which allows the insulating layer 101 to be favorably adhered to the separator 23. Note that a detailed configuration of the positive electrode 21 will be described later.
The negative electrode 22 includes a negative electrode covered region 221in which the negative electrode current collector 22A is covered with the negative electrode active material layer 22B, and a negative electrode exposed region 222in which the negative electrode current collector 22A is exposed without being covered with the negative electrode active material layer 22B. As illustrated in
In the stacked body S20 in the electrode wound body 20, the positive electrode 21 and the negative electrode 22 are so stacked with the separator 23 interposed therebetween that the positive electrode exposed region 212 and the first part 222A of the negative electrode exposed region 222 face toward mutually opposite directions along the W-axis direction, i.e., a width direction. In the electrode wound body 20, an end part of the separator 23 is fixed by attaching a fixing tape 46 to a side surface part 45 of the electrode wound body 20, which prevents loosening of winding.
In the secondary battery 1, as illustrated in
As illustrated in
The positive electrode current collector 21A includes, for example, an aluminum foil, as will be described later. In contrast, the negative electrode current collector 22A includes, for example, a copper foil, as will be described later. In this case, the positive electrode current collector 21A is softer than the negative electrode current collector 22A. In other words, the positive electrode exposed region 212 has a Young's modulus lower than a Young's modulus of the negative electrode exposed region 222. Accordingly, in an embodiment, it is more preferable that the widths A to D satisfy a relationship of A>B and C>D. In such a case, when the positive electrode exposed region 212 and the negative electrode exposed region 222 are simultaneously bent with equal pressures from respective electrode sides, the bent portion in the positive electrode 21 and the bent portion in the negative electrode 22 may sometimes have substantially equal heights measured from respective ends of the separator 23. In this case, the multiple positive electrode edge parts 212E (
As illustrated in
The secondary battery 1 may further include insulating tapes 53 and 54 in a gap between the outer package can 11 and the electrode wound body 20. The positive electrode exposed region 212 having the parts gathering at the upper end face 41 and the negative electrode exposed region 222 having the parts gathering at the lower end face 42 are electrical conductors, such as metal foils, that are exposed. Accordingly, if the positive electrode exposed region 212 and the negative electrode exposed region 222 are in proximity to the outer package can 11, a short circuit between the positive electrode 21 and the negative electrode 22 can occur via the outer package can 11. A short circuit can also occur when the positive electrode current collector plate 24 on the upper end face 41 and the outer package can 11 come into proximity to each other. Therefore, the insulating tapes 53 and 54 are preferably provided as insulating members. Each of the insulating tapes 53 and 54 is, for example, an adhesive tape including a base layer, and an adhesive layer provided on one surface of the base layer. The base layer includes, for example, any of polypropylene, polyethylene terephthalate, or polyimide. To prevent the provision of the insulating tapes 53 and 54 from resulting in a decreased capacity of the electrode wound body 20, the insulating tapes 53 and 54 are disposed not to overlap the fixing tape 46 attached to the side surface part 45, and a thickness of each of the insulating tapes 53 and 54 is set to be less than or equal to a thickness of the fixing tape 46.
In a typical lithium-ion secondary battery, for example, a lead for current extraction is welded to one location on each of the positive electrode and the negative electrode. However, such a structure increases the internal resistance of the lithium-ion secondary battery and causes the lithium-ion secondary battery to generate heat and become hot upon discharging; therefore, the structure is unsuitable for high-rate discharging. To address this, in the secondary battery 1 according to the present embodiment, the positive electrode current collector plate 24 is disposed to face the upper end face 41, and the negative electrode current collector plate 25 is disposed to face the lower end face 42. In addition, the positive electrode exposed region 212 present at the upper end face 41 and the positive electrode current collector plate 24 are welded to each other at multiple points, and the negative electrode exposed region 222 present at the lower end face 42 and the negative electrode current collector plate 25 are welded to each other at multiple points. A reduced internal resistance of the secondary battery 1 is thereby achieved. Each of the upper end face 41 and the lower end face 42 is a flat surface, as described above, which also contributes to the reduced resistance. The positive electrode current collector plate 24 is electrically coupled to the battery cover 14 via the safety valve mechanism 30, for example. The negative electrode current collector plate 25 is electrically coupled to the outer package can 11, for example.
As illustrated in
The negative electrode current collector plate 25 illustrated in
The fan-shaped part 31 of the positive electrode current collector plate 24 covers only a portion of the upper end face 41, owing to a plan shape of the fan-shaped part 31. Similarly, the fan-shaped part 33 of the negative electrode current collector plate 25 covers only a portion of the lower end face 42, owing to a plan shape of the fan-shaped part 33. Reasons why the fan-shaped part 31 does not entirely cover the upper end face 41 and why the fan-shaped part 33 does not entirely cover the lower end face 42 include the following two reasons, for example. A first reason is to allow the electrolytic solution to smoothly permeate the electrode wound body 20 in assembling the secondary battery 1, for example. A second reason is to allow a gas generated when the lithium-ion secondary battery comes into an abnormally hot state or an overcharged state to be easily released to the outside.
The positive electrode current collector 21A includes an electrically conductive material such as aluminum, for example. The positive electrode current collector 21A is a metal foil including aluminum or an aluminum alloy, for example.
The positive electrode active material layer 21B includes, as a positive electrode active material, any one or more of positive electrode materials into which lithium is insertable and from which lithium is extractable. Note that the positive electrode active material layer 21B may further include any one or more of other materials. Examples of the other materials include a positive electrode binder and a positive electrode conductor. It is preferable that the positive electrode material be a lithium-containing compound, and more specifically, a lithium-containing composite oxide or a lithium-containing phosphoric acid compound, for example. The lithium-containing composite oxide is an oxide including lithium and one or more of other elements, that is, one or more of elements other than lithium, as constituent elements. The lithium-containing composite oxide has any of crystal structures including, without limitation, a layered rock-salt crystal structure and a spinel crystal structure, for example. The lithium-containing phosphoric acid compound is a phosphoric acid compound including lithium and one or more of other elements as constituent elements, and has a crystal structure such as an olivine crystal structure, for example. The positive electrode active material layer 21B preferably includes, as the positive electrode active material, at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide, in particular. The positive electrode binder includes, for example, any one or more of materials including, without limitation, a synthetic rubber and a polymer compound. Examples of the synthetic rubber include a styrene-butadiene-based rubber, a fluorine-based rubber, and ethylene propylene diene. Examples of the polymer compound include polyvinylidene difluoride and polyimide. The positive electrode conductor includes, for example, any one or more of materials including, without limitation, a carbon material. Examples of the carbon material include graphite, carbon black, acetylene black, and Ketjen black. Note that the positive electrode conductor may be any of electrically conductive materials, and may be, for example, a metal material or an electrically conductive polymer.
The negative electrode current collector 22A includes an electrically conductive material such as copper, for example. The negative electrode current collector 22A is a metal foil including, for example, nickel, a nickel alloy, copper, or a copper alloy. A surface of the negative electrode current collector 22A is preferably roughened. One reason for this is that this improves adherence of the negative electrode active material layer 22B to the negative electrode current collector 22A owing to what is called an anchor effect. In this case, the surface of the negative electrode current collector 22A is to be roughened at least in a region facing the negative electrode active material layer 22B. Examples of a roughening method include a method in which microparticles are formed through an electrolytic treatment. In the electrolytic treatment, the microparticles are formed on the surface of the negative electrode current collector 22A by an electrolytic method in an electrolyzer. This provides the surface of the negative electrode current collector 22A with asperities. A copper foil produced by the electrolytic method is generally called an electrolytic copper foil.
The negative electrode active material layer 22B includes, as a negative electrode active material, any one or more of negative electrode materials into which lithium is insertable and from which lithium is extractable. Note that the negative electrode active material layer 22B may further include any one or more of other materials. Examples of the other materials include a negative electrode binder and a negative electrode conductor. For example, the negative electrode material is a carbon material. One reason for this is that the carbon material exhibits very little change in crystal structure at the time of insertion and extraction of lithium, and a high energy density is thus obtainable stably. Another reason is that the carbon material also serves as a negative electrode conductor, which allows the negative electrode active material layer 22B to be improved in electrically conductive property. Examples of the carbon material include graphitizable carbon, non-graphitizable carbon, and graphite. Note that spacing of a (002) plane of the non-graphitizable carbon is preferably 0.37 nm or greater. Spacing of a (002) plane of the graphite is preferably 0.34 nm or less. More specific examples of the carbon material include pyrolytic carbons, cokes, glassy carbon fibers, an organic polymer compound fired body, activated carbon, and carbon blacks. Examples of the cokes include pitch coke, needle coke, and petroleum coke. The organic polymer compound fired body is a resultant of firing or carbonizing a polymer compound such as a phenol resin or a furan resin at a suitable temperature. Other than the above, the carbon material may be low-crystalline carbon heat-treated at a temperature of about 1000° C. or lower, or may be amorphous carbon. Note that the carbon material may have any of a fibrous shape, a spherical shape, a granular shape, and a flaky shape. In the secondary battery 1, when an open circuit voltage in a fully charged state, that is, a battery voltage is 4.25 V or higher, the amount of extracted lithium per unit mass increases as compared with when the open circuit voltage in the fully charged state is 4.20 V, even with the same positive electrode active material. The amount of the positive electrode active material and the amount of the negative electrode active material are therefore adjusted accordingly. This makes it possible to obtain a high energy density.
The negative electrode active material layer 22B may include, as the negative electrode active material, a silicon-containing material including at least one of silicon, silicon oxide, a carbon-silicon compound, or a silicon alloy. The term “silicon-containing material” is a generic term for a material that includes silicon as a constituent element. Note that the silicon-containing material may include only silicon as the constituent element. One silicon-containing material may be used, or two or more silicon-containing materials may be used. The silicon-containing material is able to form an alloy with lithium, and may be a simple substance of silicon, a silicon alloy, a silicon compound, a mixture of two or more thereof, or a material including one or more phases thereof. Further, the silicon-containing material may be crystalline or amorphous, or may include both a crystalline part and an amorphous part. Note that the simple substance described here refers to a simple substance merely in a general sense. The simple substance may thus include a small amount of impurity. In other words, purity of the simple substance is not limited to 100%. The silicon alloy includes, as one or more constituent elements other than silicon, any one or more of elements including, without limitation, tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium, for example. The silicon compound includes, as one or more constituent elements other than silicon, any one or more of elements including, without limitation, carbon and oxygen, for example. Note that the silicon compound may include, as one or more constituent elements other than silicon, any one or more of the series of constituent elements described above in relation to the silicon alloy, for example. Specific examples of the silicon alloy and the silicon compound include SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, CusSi, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, and SiO, (where 0<v≤2). Note that v may be set within any desired range, and may, for example, fall within the following range: 0.2<v<1.4.
The separator 23 is interposed between the positive electrode 21 and the negative electrode 22. The separator 23 allows lithium ions to pass through and prevents a short circuit of a current caused by contact between the positive electrode 21 and the negative electrode 22. The separator 23 includes, for example, any one or more kinds of porous films each including, for example, a synthetic resin or a ceramic, and may include a stacked film of two or more kinds of porous films. Examples of the synthetic resin include polytetrafluoroethylene, polypropylene, and polyethylene. Note that the separator 23 preferably includes the bases that each include a single-layer polyolefin porous film including polyethylene. One reason for this is that a favorable high output characteristic is obtainable as compared with a stacked film. When the first separator member 23A and the second separator member 23B included in the separator 23 each include a single-layer porous film including polyolefin, the porous film preferably has a thickness of greater than or equal to 10 μm and less than or equal to 15 μm, for example. An internal short circuit is sufficiently avoidable if the single-layer porous film including polyolefin has a thickness of greater than or equal to 10 μm. A more favorable discharge capacity characteristic is achievable if the thickness of the single-layer porous film including polyolefin is less than or equal to 15 μm. Further, the porous film preferably has a surface density of greater than or equal to 6.3 g/m2 and less than or equal to 8.3 g/m2, for example. An internal short circuit is sufficiently avoidable if the surface density of the single-layer porous film including polyolefin is greater than or equal to 6.3 g/m2. A more favorable discharge capacity characteristic is achievable if the surface density of the single-layer porous film including polyolefin is less than or equal to 8.3 g/m2.
In particular, the separator 23 may include, for example, the porous film as each of the above-described bases, and a polymer compound layer provided on one of or each of two opposite surfaces of each of the bases. One reason for this is that adherence of the separator 23 to each of the positive electrode 21 and the negative electrode 22 improves, which suppresses distortion of the electrode wound body 20. As a result, a decomposition reaction of the electrolytic solution is suppressed, and leakage of the electrolytic solution with which the bases are impregnated is also suppressed. This prevents an easy increase in resistance even upon repeated charging and discharging, and also suppresses swelling of the battery. The polymer compound layer includes a polymer compound such as polyvinylidene difluoride, for example. One reason for this is that the polymer compound such as polyvinylidene difluoride has superior physical strength and is electrochemically stable. Note that the polymer compound may be other than polyvinylidene difluoride. To form the polymer compound layer, for example, a solution in which the polymer compound is dissolved in a solvent such as an organic solvent is applied on the base, following which the base is dried. Alternatively, the base may be immersed in the solution and thereafter dried. The polymer compound layer may include any one or more kinds of insulating particles such as inorganic particles, for example. Examples of the kind of the inorganic particles include aluminum oxide and aluminum nitride.
The electrolytic solution includes a solvent and an electrolyte salt. Note that the electrolytic solution may further include any one or more of other materials. Examples of the other materials include an additive. The solvent includes any one or more of nonaqueous solvents including, without limitation, an organic solvent. An electrolytic solution including a nonaqueous solvent is what is called a nonaqueous electrolytic solution. The nonaqueous solvent includes a fluorine compound and a dinitrile compound, for example. The fluorine compound includes, for example, at least one of fluorinated ethylene carbonate, trifluorocarbonate, trifluoroethyl methyl carbonate, a fluorinated carboxylic acid ester, or a fluorine ether. The nonaqueous solvent may further include at least one of nitrile compounds other than the dinitrile compound. Examples of the nitrile compounds other than the dinitrile compound include a mononitrile compound and a trinitrile compound. For example, succinonitrile (SN) is preferable as the dinitrile compound. Note that the dinitrile compound is not limited to succinonitrile, and may be another dinitrile compound such as adiponitrile.
The electrolyte salt includes, for example, any one or more of salts including, without limitation, a lithium salt. Note that the electrolyte salt may include a salt other than the lithium salt, for example. Examples of the salt other than the lithium salt include a salt of a light metal other than lithium. Examples of the lithium salt include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), dilithium hexafluorosilicate (Li2SiF6), lithium chloride (LiCl), and lithium bromide (LiBr). In particular, the lithium salt is preferably any one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, or lithium hexafluoroarsenate, and more preferably, lithium hexafluorophosphate. Although not particularly limited, a content of the electrolyte salt is preferably within a range from 0.3 mol/kg to 3 mol/kg both inclusive with respect to the solvent, in particular. When the electrolytic solution includes LiPF6 as the electrolyte salt, a concentration of LiPF6 in the electrolytic solution is preferably higher than or equal to 1.25 mol/kg and lower than or equal to 1.45 mol/kg. One reason for this is that this makes it possible to prevent cycle deterioration caused by consumption, or decomposition, of the salt at the time of high load rate charging, and thus allows for improvement in high-load cyclability characteristic. When the electrolytic solution further includes LiBF4 in addition to LiPF6 as the electrolyte salt, a concentration of LiBF4 in the electrolytic solution is preferably higher than or equal to 0.001 (wt %) and lower than or equal to 0.1 (wt %). One reason for this is that this makes it possible to more effectively prevent the cycle deterioration caused by consumption, or decomposition, of the salt at the time of high load rate charging, and thus allows for further improvement in high-load cyclability characteristic.
In the secondary battery 1, the outer package can 11 has a horizontal sectional shape that is substantially circular, as illustrated in
As illustrated in
At the height position Lv1, a portion of an outer peripheral surface 20S of the electrode wound body 20 is preferably in contact with an inner surface 11WS2 of the sidewall part 11W of the outer package can 11, as illustrated in
In the secondary battery 1 according to the present embodiment, for example, upon charging, lithium ions are extracted from the positive electrode 21, and the extracted lithium ions are inserted into the negative electrode 22 via the electrolytic solution. In the secondary battery 1, for example, upon discharging, lithium ions are extracted from the negative electrode 22, and the extracted lithium ions are inserted into the positive electrode 21 via the electrolytic solution.
A method of manufacturing the secondary battery 1 will be described with reference to
First, the positive electrode current collector 21A is prepared, and the positive electrode active material layer 21B is selectively formed on the surface of the positive electrode current collector 21A to thereby form the positive electrode 21 including the positive electrode covered region 211 and the positive electrode exposed region 212. Thereafter, the negative electrode current collector 22A is prepared, and the negative electrode active material layer 22B is selectively formed on the surface of the negative electrode current collector 22A to thereby form the negative electrode 22 including the negative electrode covered region 221 and the negative electrode exposed region 222. The positive electrode 21 and the negative electrode 22 may be subjected to a drying process. Thereafter, the positive electrode 21 and the negative electrode 22 are stacked, with the first separator member 23A and the second separator member 23B on the positive electrode 21 and the negative electrode 22, respectively, to cause the positive electrode exposed region 212 and the first part 222A of the negative electrode exposed region 222 to be on opposite sides to each other in the W-axis direction. The stacked body S20 is thereby fabricated. Thereafter, the stacked body S20 is so wound in a spiral shape as to form the through hole 26. Upon thus winding the stacked body S20, for example, a columnar winding core having a sectional shape that gradually changes from elliptical to circular along the height direction is used as a jig, and the stacked body S20 is wound around the columnar winding core. In addition, the fixing tape 46 is attached to an outermost wind of the stacked body S20 wound in the spiral shape, following which the winding core is removed. The electrode wound body 20 is thus obtained as illustrated in part (A) of
Thereafter, as illustrated in part (B) of
Thereafter, as illustrated in part (C) of
Thereafter, the insulating tapes 53 and 54 are attached to respective predetermined locations on the electrode wound body 20. Thereafter, as illustrated in part (D) of
Thereafter, the electrode wound body 20 having been assembled in the above-described manner is placed into the outer package can 11 illustrated in part (E) of
Thereafter, as illustrated in part (F) of
The secondary battery 1 according to the present embodiment is completed in the above-described manner.
As described above, in the secondary battery 1 of the present embodiment, the flattening FT1 of the horizontal sectional shape of the upper part of the electrode wound body 20 is greater than the flattening FT2 of the horizontal sectional shape of the lower part of the electrode wound body 20 (FT1>FT2). The flattening FT2 of the lower part of the electrode wound body 20 thus being smaller than the flattening FT1 of the upper part of the electrode wound body 20 makes it easier for the electrode wound body 20 to be placed into the outer package can 11 upon assembly of the secondary battery 1. That is, decreasing the flattening FT2 of the lower part of the electrode wound body 20 and thereby causing the sectional shape of the lower part of the electrode wound body 20 to be closer to a perfect circle makes it possible to allow the electrode wound body 20 to be easily placed inside the outer package can 11, without causing the outer peripheral surface 20S of the electrode wound body 20 to interfere with the upper end part of the outer package can 11. Meanwhile, because the flattening FT1 of the upper part of the electrode wound body 20 is greater than the flattening FT2 of the lower part of the electrode wound body 20, the outer peripheral surface 20S of the upper part of the electrode wound body 20 contained inside the outer package can 11 is allowed to be in contact with the inner surface 11WS2 of the outer package can 11. This helps to prevent the electrode wound body 20 from easily moving inside the outer package can 11 even when the secondary battery 1 undergoes, for example, vibration or impact. This makes it possible to prevent, for example, damage to the electrode wound body 20 itself, and damage to a coupling part between the positive electrode current collector plate 24, which is joined to the electrode wound body 20, and the battery cover 14. The secondary battery 1 thus makes it possible to achieve superior vibration resistance without degrading manufacturability.
In particular, the secondary battery 1 employs what is called a tabless structure in which the electrode wound body 20 has no electrode tab extending in the height direction Z. This allows the electrode wound body 20 to be soft and easily changeable in shape, and thus allows the flattening of the electrode wound body 20 to be easily adjustable. This is preferable for achieving the electrode wound body 20 in which the horizontal sectional shape of the upper part in the height direction Z and the horizontal sectional shape of the lower part in the height direction Z are different from each other. Further, the electrode wound body 20 has the through hole 26, instead of the winding core at the center part thereof. This is also preferable for achieving the electrode wound body 20 in which the horizontal sectional shape of the upper part in the height direction Z and the horizontal sectional shape of the lower part in the height direction Z are different from each other.
Examples of applications of the secondary battery 1 according to an embodiment of the present disclosure are as described below.
The battery pack 300 includes a positive electrode terminal 321 and a negative electrode terminal 322. Upon charging, the positive electrode terminal 321 and the negative electrode terminal 322 are respectively coupled to a positive electrode terminal and a negative electrode terminal of a charger to thereby perform charging. Upon use of electronic equipment, the positive electrode terminal 321 and the negative electrode terminal 322 are respectively coupled to a positive electrode terminal and a negative electrode terminal of the electronic equipment to thereby perform discharging.
The assembled battery 301 includes multiple secondary batteries 301a coupled in series or in parallel. The secondary battery 1 described above is applicable to each of the secondary batteries 301a. Note that
The switcher 304 includes the charge control switch 302a, a diode 302b, the discharge control switch 303a, and a diode 303b, and is controlled by the controller 310. The diode 302b has a polarity that is in a reverse direction with respect to a charge current flowing in a direction from the positive electrode terminal 321 to the assembled battery 301 and that is in a forward direction with respect to a discharge current flowing in a direction from the negative electrode terminal 322 to the assembled battery 301. The diode 303b has a polarity that is in the forward direction with respect to the charge current and in the reverse direction with respect to the discharge current. In
The charge control switch 302a is so controlled by a charge and discharge controller that when the battery voltage reaches an overcharge detection voltage, the charge control switch 302a is turned off to thereby prevent the charge current from flowing through a current path of the assembled battery 301. After the charge control switch 302a is turned off, only discharging is enabled through the diode 302b. Further, the charge control switch 302a is so controlled by the controller 310 that when a large current flows upon charging, the charge control switch 302a is turned off to thereby block the charge current flowing through the current path of the assembled battery 301. The discharge control switch 303a is so controlled by the controller 310 that when the battery voltage reaches an overdischarge detection voltage, the discharge control switch 303a is turned off to thereby prevent the discharge current from flowing through the current path of the assembled battery 301. After the discharge control switch 303a is turned off, only charging is enabled through the diode 303b. Further, the discharge control switch 303a is so controlled by the controller 310 that when a large current flows upon discharging, the discharge control switch 303a is turned off to thereby block the discharge current flowing through the current path of the assembled battery 301.
The temperature detection device 308 is, for example, a thermistor. The temperature detection device 308 is provided in the vicinity of the assembled battery 301, measures a temperature of the assembled battery 301, and supplies the measured temperature to the controller 310. A voltage detector 311 measures a voltage of the assembled battery 301 and a voltage of each of the secondary batteries 301a included in the assembled battery 301, performs A/D conversion on the measured voltages, and supplies the converted voltages to the controller 310. A current measurer 313 measures a current by means of the current detection resistor 307, and supplies the measured current to the controller 310. A switch controller 314 controls the charge control switch 302a and the discharge control switch 303a of the switcher 304, based on the voltages inputted from the voltage detector 311 and the current inputted from the current measurer 313.
When a voltage of any of the multiple secondary batteries 301a reaches the overcharge detection voltage or below, or reaches the overdischarge detection voltage or below, or when a large current flows suddenly, the switch controller 314 transmits a control signal to the switcher 304 to thereby prevent overcharging and overdischarging, and overcurrent charging and discharging. For example, when the secondary battery is a lithium-ion secondary battery, the overcharge detection voltage is determined to be, for example, 4.20 V±0.05 V, and the overdischarge detection voltage is determined to be, for example, 2.4 V±0.1 V.
As the charge and discharge control switches, for example, semiconductor switches such as MOSFETs are usable. In this case, parasitic diodes of the MOSFETs serve as the diodes 302b and 303b. When P-channel FETs are used as the charge and discharge switches, the switch controller 314 supplies control signals CO and DO to a gate of the charge control switch 302a and a gate of the discharge control switch 303a, respectively. When the charge control switch 302a and the discharge control switch 303a are of P-channel type, the charge control switch 302a and the discharge control switch 303a are turned on by a gate potential that is lower than a source potential by a predetermined value or more. That is, in normal charging and discharging operations, the control signals CO and DO are set to a low level to turn on the charge control switch 302a and the discharge control switch 303a.
For example, upon overcharging or overdischarging, the control signals CO and DO are set to a high level to turn off the charge control switch 302a and the discharge control switch 303a.
A memory 317 includes a RAM and a ROM. For example, the memory 317 includes an erasable programmable read only memory (EPROM) as a nonvolatile memory. In the memory 317, values including, without limitation, numerical values calculated by the controller 310 and a battery's internal resistance value of each of the secondary batteries 301a in an initial state measured in the manufacturing process stage, are stored in advance and are rewritable on an as-needed basis. Further, by storing a full charge capacity of the secondary battery 301a, it is possible to calculate, for example, a remaining capacity with the controller 310.
A temperature detector 318 measures a temperature with use of the temperature detection device 308, performs charge and discharge control upon abnormal heat generation, and performs correction in calculating the remaining capacity.
The secondary battery according to an embodiment of the present disclosure is mountable on, or usable to supply electric power to, for example, any of equipment including, without limitation, electronic equipment, an electric vehicle, an electric aircraft, and an electric power storage apparatus.
Examples of the electronic equipment include laptop personal computers, smartphones, tablet terminals, PDAs (i.e., mobile information terminals), mobile phones, wearable terminals, cordless phone handsets, hand-held video recording and playback devices, digital still cameras, electronic books, electronic dictionaries, music players, radios, headphones, game machines, navigation systems, memory cards, pacemakers, hearing aids, electric tools, electric shavers, refrigerators, air conditioners, televisions, stereos, water heaters, microwave ovens, dishwashers, washing machines, dryers, lighting equipment, toys, medical equipment, robots, road conditioners, and traffic lights.
Examples of the electric vehicle include railway vehicles, golf carts, electric carts, and electric automobiles including hybrid electric automobiles. The secondary battery is usable as a driving power source or an auxiliary power source for any of these electric vehicles. Examples of the electric power storage apparatuses include an electric power storage power source for architectural structures including residential houses, or for power generation facilities.
Examples of the present disclosure will be described according to an embodiment.
As described below, cylindrical secondary batteries illustrated in
First, an aluminum foil having a thickness of 12 μm was prepared as the positive electrode current collector 21A. Thereafter, a positive electrode mixture was obtained by mixing a layered lithium oxide as the positive electrode active material with a positive electrode binder and a conductive additive. The layered lithium oxide included lithium nickel cobalt aluminum oxide (NCA) having a Ni ratio of 85% or greater. The positive electrode binder included polyvinylidene difluoride. The conductive additive included a mixture of carbon black, acetylene black, and Ketjen black. A mixture ratio between the positive electrode active material, the positive electrode binder, and the conductive additive was set to 96.4:2:1.6. Thereafter, the positive electrode mixture was put into an organic solvent (N-methyl-2-pyrrolidone), following which the organic solvent was stirred to thereby prepare a positive electrode mixture slurry in paste form. Thereafter, the positive electrode mixture slurry was applied on respective predetermined regions of the two opposite surfaces of the positive electrode current collector 21A by means of a coating apparatus, following which the applied positive electrode mixture slurry was dried to thereby form the positive electrode active material layers 21B. Further, a coating material including polyvinylidene difluoride (PVDF) was applied on surfaces of the positive electrode exposed region 212, at respective locations adjacent to the positive electrode covered region 211. The applied coating material was dried to thereby form the insulating layers 101 each having a width of 3 mm and a thickness of 8 μm. Thereafter, the positive electrode active material layers 21B were compression-molded by means of a roll pressing machine. The positive electrode 21 including the positive electrode covered region 211 and the positive electrode exposed region 212 was thus obtained. Thereafter, the positive electrode 21 was sheared to make the positive electrode covered region 211 have a width of 60 mm in the W-axis direction, and to make the positive electrode exposed region 212 have a width of 7 mm in the W-axis direction. A length of the positive electrode 21in the L-axis direction was set to 1700 mm.
Further, a copper foil having a thickness of 8 μm was prepared as the negative electrode current collector 22A. Thereafter, a negative electrode mixture was obtained by mixing the negative electrode active material with a negative electrode binder and a conductive additive. The negative electrode active material included a mixture of a carbon material and SiO. The carbon material included graphite. The negative electrode binder included polyvinylidene difluoride. The conductive additive included a mixture of carbon black, acetylene black, and Ketjen black. A mixture ratio between the negative electrode active material, the negative electrode binder, and the conductive additive was set to 96.1:2.9:1.0. Further, a mixture ratio between graphite and SiO in the negative electrode active material was set to 95:5. Thereafter, the negative electrode mixture was put into an organic solvent (N-methyl-2-pyrrolidone), following which the organic solvent was stirred to thereby prepare a negative electrode mixture slurry in paste form. Thereafter, the negative electrode mixture slurry was applied on respective predetermined regions of the two opposite surfaces of the negative electrode current collector 22A by means of a coating apparatus, following which the applied negative electrode mixture slurry was dried to thereby form the negative electrode active material layers 22B. Thereafter, the negative electrode active material layers 22B were compression-molded by means of a roll pressing machine. The negative electrode 22 including the negative electrode covered region 221 and the negative electrode exposed region 222 was thus obtained. Thereafter, the negative electrode 22 was sheared to make the negative electrode covered region 221 have a width of 62 mm in the W-axis direction, and to make the first part 222A of the negative electrode exposed region 222 have a width of 4 mm in the W-axis direction. A length of the negative electrode 22 in the L-axis direction was set to 1760 mm.
Thereafter, the positive electrode 21 and the negative electrode 22 were stacked, with the first separator member 23A and the second separator member 23B on the positive electrode 21 and the negative electrode 22, respectively, to cause the positive electrode exposed region 212 and the first part 222A of the negative electrode exposed region 222 to be on opposite sides to each other in the W-axis direction. The stacked body S20 was thereby fabricated. At this time, the stacked body S20 was fabricated not to allow the positive electrode active material layers 21B to protrude from the negative electrode active material layers 22B in the W-axis direction. As each of the first separator member 23A and the second separator member 23B, used was a polyethylene sheet having a width of 65 mm and a thickness of 14 μm. Thereafter, the stacked body S20 was so wound in a spiral shape as to form the through hole 26, and the fixing tape 46 was attached to the outermost wind of the stacked body S20 thus wound. The electrode wound body 20 was thereby obtained. A pressure was applied to end parts, of the obtained electrode wound body 20, in a width direction, from an outer peripheral surface of the electrode wound body 20 toward a winding center of the electrode wound body 20, to thereby adjust the flattenings FT1 and FT2 to be predetermined degrees.
Thereafter, the upper end face 41 and the lower end face 42 of the electrode wound body 20 were each locally bent by pressing an end of a 0.5-millimeter-thick flat plate against each of the upper end face 41 and the lower end face 42 in the Z-axis direction. The grooves 43 extending radiately in the radial directions (the R directions) from the through hole 26 were thereby formed.
Thereafter, substantially equal pressures were applied to the upper end face 41 and the lower end face 42 in substantially perpendicular directions from above and below the electrode wound body 20 at substantially the same time. The positive electrode exposed region 212 and the first part 222A of the negative electrode exposed region 222 were thereby bent to make each of the upper end face 41 and the lower end face 42 into a flat surface. At this time, the positive electrode edge parts 212E of the positive electrode exposed region 212 positioned at the upper end face 41 were caused to bend toward the through hole 26 while overlapping each other, and the negative electrode edge parts 222E of the negative electrode exposed region 222 positioned at the lower end face 42 were caused to bend toward the through hole 26 while overlapping each other. Thereafter, the fan-shaped part 31 of the positive electrode current collector plate 24 was joined to the upper end face 41 by laser welding, and the fan-shaped part 33 of the negative electrode current collector plate 25 was joined to the lower end face 42 by laser welding.
Thereafter, the insulating tapes 53 and 54 were attached to the respective predetermined locations on the electrode wound body 20, following which the band-shaped part 32 of the positive electrode current collector plate 24 was bent and inserted through the hole 12H of the insulating plate 12, and the band-shaped part 34 of the negative electrode current collector plate 25 was bent and inserted through the hole 13H of the insulating plate 13.
Thereafter, the electrode wound body 20 having been assembled in the above-described manner was placed into the outer package can 11, following which the bottom part of the outer package can 11 and the negative electrode current collector plate 25 were welded to each other. Note that the outer package can 11 had the inner diameter D11 of 20.80 mm+0.05 mm. Thereafter, the narrow part was formed in the vicinity of the open end part 11N of the outer package can 11. Further, the electrolytic solution was injected into the outer package can 11, following which the band-shaped part 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 were welded to each other.
As the electrolytic solution, used was a solution including a solvent prepared by adding fluoroethylene carbonate (FEC) and succinonitrile (SN) to a major solvent, i.e., ethylene carbonate (EC) and dimethyl carbonate (DMC), and including LiBF4 and LiPF6 as the electrolyte salt. In the lithium-ion secondary battery of the present example, a content ratio (wt %) between EC, DMC, FEC, SN, LiBF4, and LiPF6 in the electrolytic solution was set to 12.7:56.2:12.0:1.0:1.0:17.1.
Thereafter, sealing was performed with the gasket 15, the safety valve mechanism 30, and the battery cover 14, through the use of the narrow part. Lastly, the outer package can 11 with the washer 55 attached on the battery cover 14 was covered with the outer package tube 50, following which the outer package tube 50 was heated by applying hot air to the outer package tube 50. The outer package tube 50 was thus contracted and closely attached to the outer surface of the outer package can 11.
The secondary batteries of Examples 1-1 to 1-4 and Comparative examples 1-1 to 1-4 were thus obtained.
The secondary batteries obtained as described above in Examples 1-1 to 1-4 and Comparative examples 1-1 to 1-4 were each subjected to each of measurement of respective outer diameters of the upper part and the lower part of the electrode wound body 20, evaluation of easiness of placement of the electrode wound body 20 into the outer package can 11, and evaluation of vibration resistance. The results are presented in Table 1 together.
Measured were the maximum diameter D20max1 of the upper part of the electrode wound body 20, the minimum diameter D20min1 of the upper part of the electrode wound body 20, the maximum diameter D20max2 of the lower part of the electrode wound body 20, and the minimum diameter D20min2 of the lower part of the electrode wound body 20. Specifically, while the electrode wound body 20 was rotated around its central axis as a rotational axis, an outer diameter of a two-dimensional projection image of the electrode wound body 20 was measured by a two-dimensional projection outer diameter measurement apparatus. Here, the maximum diameter and the minimum diameter in the horizontal section of the electrode wound body 20 at the height position Lv1 illustrated in
In evaluating the easiness of the placement of the outer package can 11 into the electrode wound body 20, if, when the electrode wound body 20 was to be placed into the outer package can 11, it was not possible to place the electrode wound body 20 into the outer package can 11 because of, for example, contact between the outer peripheral surface 20S of the electrode wound body 20 and the open end part 11N, this case was determined as “fail”, which is indicated by “F” in Table 1. In contrast, a case where it was possible to place the electrode wound body 20 into the outer package can 11 was determined as “pass”, which is indicated by “P” in Table 1. Note that in each of Comparative examples 1-1 and 1-3 in which it was not possible to place the electrode wound body 20 into the outer package can 11, the maximum diameter D20max1 of the upper part of the electrode wound body 20, the minimum diameter D20min1 of the upper part of the electrode wound body 20, the maximum diameter D20max2 of the lower part of the electrode wound body 20, and the minimum diameter D20min2 of the lower part of the electrode wound body 20 were measured before placing the electrode wound body 20 into the outer package can 11.
In each of Examples and Comparative examples, six secondary batteries (n=6) were fabricated, and the fabricated secondary batteries were subjected to the evaluation of the vibration resistance described below. Here, a drum test was conducted to measure a change in impedance. Specifically, the following experiment was conducted. That is, the secondary batteries were each adjusted to have an output voltage of 4.2 [V], and were placed in an iron-plate hexagonal barrel of a rotating hexagonal drum tester. The iron-plate hexagonal barrel had an inscribed circle diameter q of 190 [mm] and a length of 200 [mm]. The hexagonal barrel was rotated at an angular velocity of 60 rpm (2π [rad/s]) to apply mechanical vibration to the secondary batteries. Thereafter, each of the secondary batteries was taken out, and was subjected to measurements of an open-circuit voltage (OCV) and impedance thereof. The vibration test was repeatedly conducted until each of the secondary batteries was determined as “fail” based on the value of impedance after the vibration application greatly exceeding the initial value of impedance. Generally, application of vibration causes gradual separation of the cover part and the positive electrode current collector plate that have been joined to each other, and thus causes the impedance to increase. Based on this, the secondary battery that had a longer time length of vibration application up to the increase in impedance was evaluated as the secondary battery that had higher vibration resistance.
As indicated in table 1, in each of Examples 1-1 to 1-4: the evaluation of the easiness of placement resulted in “pass” because the flattening FT1 was greater than the flattening FT2, in other words, (FT1/FT2)>1 was satisfied; and the drum test revealed that resistance for at least 100-minute vibration was achieved. In contrast, in each of Comparative examples 1-1 and 1-3 in which the flattening FT1 was smaller than the flattening FT2, in other words, (FT1/FT2)≤1 was established, the evaluation of the easiness of placement resulted in “fail”, which made it difficult to conduct further measurement. In each of Comparative examples 1-2 and 1-4, the easiness of placement was “pass”, but sufficient vibration resistance was not achieved. The results described above demonstrated that the secondary battery of the present disclosure made it possible to achieve superior vibration resistance without degrading manufacturability.
Although the present disclosure has been described hereinabove with reference to one or more embodiments including Examples, the configuration of the present disclosure is not limited thereto, and is therefore modifiable in a variety of ways. For example, in the foregoing embodiments including Examples, the description has been given of the secondary battery having what is called a tabless structure; however, the secondary battery of the present disclosure is not limited thereto, and is also applicable to a secondary battery having what is called a tab structure.
For example, in the embodiments including Examples above, the description has been given of the case where the electrode reactant is lithium; however, the electrode reactant is not particularly limited. Accordingly, the electrode reactant may be another alkali metal such as sodium or potassium, or may be an alkaline earth metal such as beryllium, magnesium, or calcium, as described above. In addition, the electrode reactant may be another light metal such as aluminum.
The effects described herein are merely examples, and the effects of the present disclosure are not limited to those described herein. Accordingly, the present disclosure may achieve other effects.
The present disclosure may encompass the following embodiments.
(1)
A secondary battery including:
The secondary battery according to (1), in which the flattening at an upper edge of the electrode wound body in the height direction is greater than the flattening at a lower edge of the electrode wound body in the height direction.
(3)
The secondary battery according to (1) or (2), in which the maximum diameter of the electrode wound body is substantially equal to an inner diameter of the battery can.
(4)
The secondary battery according to any one of (1) to (3), in which a maximum diameter at a center point of the electrode wound body in the height direction is smaller than a maximum diameter at an upper edge of the electrode wound body in the height direction, and is larger than a maximum diameter at a lower edge of the electrode wound body in the height direction.
(5)
The secondary battery according to any one of (1) to (4), in which the electrode wound body has a through hole in a center part of the electrode wound body.
(6)
The secondary battery according to any one of (1) to (5), in which a portion of the upper part of the electrode wound body is in contact with an inner surface of the container.
(7)
The secondary battery according to any one of (1) to (6), in which a maximum diameter of the upper part of the electrode wound body is larger than a maximum diameter of the lower part of the electrode wound body.
(8)
The secondary battery according to any one of (1) to (7), further including:
A battery pack including:
It should be understood that various changes and modifications to the embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-028514 | Feb 2023 | JP | national |
The present application is a continuation of International Application No. PCT/JP2024/003382, filed on Feb. 2, 2024, which claims priority to Japanese Patent Application No. 2023-028514, filed on Feb. 27, 2023, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2024/003382 | Feb 2024 | WO |
| Child | 19091030 | US |
