Patent Application
20240387922
This application claims the benefit of Korean Patent Application No. 10-2022-0009058 filed on Jan. 21, 2022, and Korean Patent Application No. 10-2023-0008310 filed on Jan. 19, 2023, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference.
The present disclosure relates to a battery module and a manufacturing method of the same, and more particularly, to a battery module capable of controlling the swelling of battery cells and a manufacturing method of the same.
In modern society, as portable devices such as a mobile phone, a notebook computer, a camcorder and a digital camera has been daily used, the development of technologies in the fields related to mobile devices as described above has been activated. In addition, chargeable/dischargeable secondary batteries are used as a power source for an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (P-HEV) and the like, in an attempt to solve air pollution and the like caused by existing gasoline vehicles using fossil fuel. Therefore, the demand for development of the secondary battery is growing.
Currently commercialized secondary batteries include a nickel cadmium battery, a nickel hydrogen battery, a nickel zinc battery, and a lithium secondary battery. Among them, the lithium secondary battery has come into the spotlight because it has advantages, for example, hardly exhibiting memory effects compared to nickel-based secondary batteries and thus being freely charged and discharged, and having very low self-discharge rate and high energy density.
Such a lithium secondary battery mainly uses a lithium-based oxide and a carbonaceous material as a positive electrode active material and a negative electrode active material, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate, each being coated with the positive electrode active material and the negative electrode active material, are arranged with a separator being interposed between them, and a battery case which seals and accommodates the electrode assembly together with an electrolyte solution.
Generally, the lithium secondary battery may be classified into a can-type secondary battery in which the electrode assembly is mounted in a metal can, and a pouch type secondary battery in which the electrode assembly is mounted in a pouch of an aluminum laminate sheet, depending on the shape of the exterior material.
Recently, secondary batteries are widely used not only for small-sized devices such as cellular phones but also middle-sized or large-sized devices such as vehicles and energy storage systems. For the purpose of applying to such middle-sized or large-sized devices, a great number of secondary batteries may be electrically connected to enhance capacity and output. At this time, pouch-type secondary batteries tends to be more widely used due to advantages such as being easily stacked and having a light weight.
A pouch-type secondary battery may be generally manufactured through a process of injecting an electrolyte solution in a state in which an electrode assembly is accommodated in a pouch exterior part, and sealing the pouch exterior part.
A secondary battery may generate gas inside due to deterioration or the like as charge/discharge is repeated. And, when gas is generated from the inside in this way, the internal pressure increases, which may cause a swelling phenomenon in which pressure resistance increases and at least a part of the exterior part swells. In particular, in the case of the pouch-type secondary batteries, the structural stiffness of the exterior part is weaker than that of the can-type secondary battery, so that the swelling phenomenon may occur more severely.
Conventionally, battery cells are accommodated in a module case, and foam-shaped pads are disposed, so that the module case does not restrict the battery cells excessively, and the pad absorbs swelling of the battery cells.
When the swelling phenomenon of the battery cell occurs to a large extent, the pressure inside the battery increases and the volume increases, which may adversely affect the structural stability of the battery module. Moreover, a battery module often includes a plurality of secondary batteries. In particular, in the case of middle-sized or large-sized battery modules used in automobiles, energy storage systems (ESS), etc., a large number of secondary batteries can be included and interconnected for high output or high capacity. At this time, even if the volume of each secondary battery increases little by little due to swelling, the volume change of each secondary battery is accumulated to the battery module as a whole, and the degree of deformation may reach a serious level. In particular, the module frame accommodating a plurality of secondary batteries may be deformed, or the welded portion of the module frame may be broken. That is, the volume expansion phenomenon due to the swelling of each secondary battery may reduce the overall structural stability of the battery module. In addition, when the swelling force greatly increases while charge/discharge is repeated, the separator in the battery cell may be compressed, thereby partially degrading battery performance.
Therefore, there is a need to develop a method capable of absorbing the expansion displacement during swelling of the battery cell and applying an appropriate pressing force to the battery cell.
It is an object of the present disclosure to provide a battery module capable of absorbing expansion displacement due to swelling of the battery cell and applying an appropriate pressing force to the battery cell so that the battery cells can exhibit optimal performance, and a manufacturing method of the same.
However, the problem to be solved by embodiments of the present disclosure is not limited to the above-described problems, and can be variously expanded within the scope of the technical idea included in the present disclosure.
According to one embodiment of the present disclosure, there is provided a battery module comprising: a battery cell stack in which a plurality of battery cells are stacked in a stacking direction; a module frame that accommodates the battery cell stack therein; and a tube stacked on a first side of at least one of the plurality of battery cells within the battery cell stack, wherein a through hole is formed in the module frame, wherein the tube includes an injection part connected to an external fluid supply device via the through hole, and fluid flows into the tube from the fluid supply device through the injection part.
The battery module may further comprise a heat transfer member located between the battery cell stack and a first surface of the module frame.
The heat transfer member may include a thermal resin layer, and the plurality of battery cells may be adhered to the thermal resin layer.
An injection hole may be formed in the first surface of the module frame.
The thermal resin layer may be formed by injecting a thermal resin through the injection hole.
The heat transfer member may include a thermal pad, and a second side of the plurality of battery cells may be in contact with the thermal pad, with the plurality of battery cells being slidable on the thermal pad in the stacking direction of the plurality of battery cells.
The battery module may further comprise at least one of a cooling plate or a compression pad disposed adjacent to at least one of the plurality of battery cells.
The injection part may have a closed micro-hole shape. When the fluid receives pressure, the injection part is opened so that fluid flow into the tube, or the fluid is discharged from the tube.
The tube may be a soft or elastic material, and the fluid flowing into the tube may be in a liquid or gel state.
The battery module may further comprise a check valve connected to the tube.
A compression pad may be interposed at least at one place between adjacent battery cells of the plurality of battery cells or between an outermost battery cell of the plurality of battery cells and the side surface part of the module frame. In an EOL (End of Life) state, a deformation ratio in the stacking direction is 12% or less, and a surface pressure applied to the plurality of battery cells may be 0.9 MPa or less.
A module stiffness curve of the battery module may be calculated in a slope (MPa/%) range of 0.00417 or more and 0.225 or less, and the module stiffness curve of the battery module may correspond to a relationship between the deformation ratio of the module frame and the surface pressure applied to the module frame.
The module stiffness curve of the battery module may be derived by reflecting a degree of compression of compression pads in the battery cells stack relative to the surface pressure applied to the compression pads and a number of the compression pads, on a frame stiffness curve of the module frame.
According to another embodiment of the present disclosure, there is provided a method for manufacturing a battery module, the method comprising: an assembly step of accommodating a battery cell stack in which a plurality of battery cells are stacked in a stacking direction, and a tube that is stacked on a first side of at least one of the plurality of battery cells within the battery cell stack, and is empty or hollow inside, in the module frame; and an initial pressing step of injecting a fluid into the tube to press the plurality of battery cells. A through hole is formed in the module frame, and the tube includes an injection part connected to an external fluid supply device via the through hole. In the initial pressing step, the fluid supply device injects fluid into the tube through the injection part.
The initial pressing step may be performed after the assembly step.
The manufacturing method may further comprise a resin injection step of injecting a thermal resin between the battery cell stack and a first surface of the module frame to form a thermal resin layer.
An injection hole may be formed in the first surface of the module frame, and in the resin injection step, the thermal resin may be injected through the injection hole.
The resin injection step may be performed after the initial pressing step.
In the assembly step, a thermal pad may be accommodated inside the module frame, and the thermal pad may be located between the battery cell stack and one surface of the module frame.
A first side of the plurality of battery cells contacts the thermal pad, with the plurality of battery cells being slidable on the thermal pad in the stacking direction.
According to the embodiments of the present disclosure, a tube into which the fluid flows is disposed inside the battery module, so that expansion displacement due to swelling of the battery cell can be effectively absorbed.
In addition, after the battery cells and tubes are disposed inside the battery module, fluid is injected into the tubes, so that appropriate initial pressing that enables battery cells to exhibit optimal performance can be applied, and damage to battery cells due to swelling can be minimized.
The effects of the present disclosure are not limited to the effects mentioned above and additional other effects not mentioned above will be clearly understood from the description of the appended claims by those skilled in the art.
Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out them. The present disclosure may be modified in various different ways, and is not limited to the embodiments set forth herein.
Portions that are irrelevant to the description will be omitted to clearly describe the present disclosure, and like reference numerals designate like elements throughout the description.
Further, in the drawings, the size and thickness of each element are arbitrarily illustrated for convenience of description, and the present disclosure is not necessarily limited to those illustrated in the drawings. In the drawings, the thickness of layers, regions, etc. are exaggerated for clarity. In the drawings, for convenience of description, the thicknesses of a part and an area are exaggerated.
In addition, it will be understood that when an element such as a layer, film, region, or plate is referred to as being “on” or “above” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, it means that other intervening elements are not present. Further, the word “on” or “above” means arranged on or below a reference portion, and does not necessarily mean being arranged on the upper end of the reference portion toward the opposite direction of gravity.
Further, throughout the description, when a portion is referred to as “including” or “comprising” a certain component, it means that the portion can further include other components, without excluding the other components, unless otherwise stated.
Further, throughout the description, when it is referred to as “planar”, it means when a target portion is viewed from the upper side, and when it is referred to as “cross-sectional”, it means when a target portion is viewed from the side of a cross section cut vertically.
Referring to
This battery cell 110 is a pouch-type battery cell, and can be formed by accommodating an electrode assembly in a pouch case of a laminate sheet including a resin layer and a metal layer, and then adhering the outer periphery of the pouch case. Specifically, the battery cell 110 has a structure in which two electrode leads 111 and 112 face each other and protrude from one end 114a and the other end 114b of the cell main body 113, respectively. The battery cell 110 can be produced by joining both ends 114a and 114b of a cell case 114 and one side portion 114c connecting them in a state in which an electrode assembly (not shown) is accommodated in a cell case 114. In other words, the battery cell 110 according to the present embodiment has a total of three sealing parts, the sealing parts have a structure that is sealed by a method such as fusion, and the remaining other side part may be composed of a folding part 115. The battery cell 110 according to this embodiment may be a pouch-type battery cell configured to accommodate an electrode assembly inside the pouch case 114 and seal the outer periphery of the pouch case 114. The battery cell 110 described above is an illustrative structure, and it goes without saying that a unidirectional battery cell in which the two electrode leads protrude in the same direction can be used.
Such battery cells 110 are stacked along one direction to form a battery cell stack 120. As an example, the battery cells 110 may be stacked along a direction parallel to the y-axis, while facing one surface of the battery body 113.
The module frame 200 according to the present embodiment is a member that accommodates the battery cell stack 120 therein, and may include a first side surface part 210, a second side surface part 220, an upper surface part 230 and a lower surface part 240. Further, one side (x-axis direction) and the other side (−x-axis direction) of the module frame 200 may be opened, and the battery cell stack 120 may be accommodated through the opened one side or the other side. The module frame 200 may include a metal material having a predetermined strength to protect internal electrical components.
The module frame 200 shown in
Meanwhile, the battery module 100a according to the present embodiment may further include end plates 900 located on one open side and the other open side of the module frame 200, respectively. The end plates 900 may be located on the one open side and the other side of the module frame 200 so as to cover the battery cell stack 120. Edges of each end plate 900 may be joined with the corresponding edges of the module frame 200 by means of welding. The end plates 900 may include a metal material having a predetermined strength, and can protect the battery cell stack 120 and other electrical components from external impacts.
Although not specifically shown, a busbar frame and an insulating cover may be located between the end plate 900 and the battery cell stack 120. The busbar frame is configured to mount a busbar for connecting the electrode leads 111 and 112 of each battery cell 110 to each other, and the insulating cover is configured to include a material that exhibits electrical insulation and thus cut off electrical connection between the battery cells 110 and the end plate 900. Within the battery cell stack 120, the battery cells 110 may be electrically connected in series or parallel via a busbar.
Next, the tube 300 according to the present embodiment will be described in detail with reference to
Referring to
The tube 300 may have a flat shape so that it can support the battery body 113 of the battery cell 110, and may be stacked on one side of the battery cell 110 so as to cover the battery body 113 of the battery cell 110. That is, the tube 300 may be located between the battery cells 110 or located outside the battery cell 110 disposed on the outermost side. The number of the tubes 300 is not particularly limited, and a single tube or a plurality of tubes can be disposed in the battery module 100a.
A fluid F may flow into the inside of the tube 300. The tube 300 may be made of a soft or elastic material. The tube 300 may have a structure formed of a rubber material. The tube 300 is formed of an elastic rubber material, which can enhance the effect of dispersing the pressure between the battery cells 110. Further, the tube 300 may be a flat-shaped tube so that it can be stacked on one side of the battery cell 110.
Meanwhile, the fluid F flowing into the tube 300 may be in a liquid or gel state. For example, the fluid F may be cooling water or water. Cooling water or water is filled in the tube, thereby capable of achieving a cooling effect for the battery cell. In addition, when the fluid (F) is a hydrogel, this is advantageous for distributing stress concentrated in a specific region and maintaining thermal equilibrium, and can minimize the weight increase of the battery module. On the contrary, it is possible to assume that gas is used as a fluid, but when gas is used as the fluid, there may be a problem that the heated gas raises the temperature of the battery cell 110 as a whole.
The battery module 100a according to the present embodiment is configured such that a tube 300 into which a fluid F flows is provided inside, which can thus apply a constant force to the plurality of battery cells 110, and absorb the expansion displacement due to swelling of the battery cell. Since this is a control method using the fluid F, the surface pressure of the battery cell 110 can be maintained constant even if swelling of the battery cell 110 occurs.
Meanwhile, a through hole 200TH is formed in the module frame 200. As an example, a through hole 200TH may be formed in the upper surface part 230 of the module frame 200. The tube 300 includes an injection part 310 connected to an external fluid supply device 800 through a through hole 200TH, and a fluid F flows into the tube 300 from the fluid supply device 800 through the injection unit 310.
The method of providing the injection part 310 is not particularly limited. As an example, after the battery cell stack 120 including the tube 300 is accommodated in the module frame 200, the injection part 310 integrated with the main body of the tube 300 can be exposed to the outside via the through hole 200TH to connect to the fluid supply device 800. As another example, the injection part 310 is inserted via the through hole 200TH, so that the injection part 310 can be connected so as to communicates with the inside of the tube 300 whose outer periphery is sealed.
By adjusting the pressure and amount of the fluid F flowing in from the fluid supply device 800, an appropriate initial pressing may be applied to the battery cell 110 in which the battery cell 110 can exhibit optimal performance.
As an example, the fluid supply device 800 is a device for supplying the fluid F into the tube 300 and may be a conventional fluid pump or a device using a pressure head.
In another embodiment, the fluid supply device 800 using the pressure head includes a fluid supply tube fluidly connected to the tube 300. At this time, the fluid supply tube is located at a higher position than the injection part 310 of the tube 300 and has a structure perpendicular to the ground.
In addition, the height of the fluid in the fluid supply tube can be adjusted to determine the amount of fluid F flowing into the tube, thereby controlling the pressure of the tube. In such a case, the fluid supply device may apply fluid pressure to the tube without the need for a separate power source.
The battery module 100a may further include a heat transfer member located between the battery cell stack 120 and one surface of the module frame 200. The heat transfer member according to the present embodiment may include a thermal resin layer 400. One surface of the module frame 200 may mean one of the walls constituting the module frame 200, that is, one of the first side surface part 210, the second side surface part 220, the upper surface part 230 and the lower surface part 240.
As an example, a thermal resin layer 400 as a heat transfer member may be located between the battery cell stack 120 and the lower surface part 240 of the module frame 200.
One side of the battery cells 110 may be adhered to the thermal resin layer 400. Specifically, the thermal resin layer 400 may be formed by injecting or applying a thermal resin and then curing the same. The thermal resin may include a thermally conductive adhesive material, and specifically, may include at least one of a silicone material, a urethane material, or an acrylic material. The thermal resin may be in a liquid state during application, but may be cured after application to be adhered to one side of the battery cell 110. Thereby, the thermal resin layer 400 may serve to fix the battery cells 110. In addition, the thermal resin layer 400 has excellent heat conduction properties, and can quickly transfer heat generated in the battery cell 110 to the lower side of the battery module.
An injection hole 200H may be formed on the one surface of the module frame 200. As an example, an injection hole 200H may be formed in the lower surface part 240 of the module frame 200. The thermal resin layer 400 may be formed by injecting the thermal resin through the injection hole 200H.
In particular, in the case of the battery module 100a according to the present embodiment, the battery cell laminate 120 is accommodated in the module frame 200 in a state in which the tube 300 is empty, and the fluid F can be supplied to the tube 300 after completion of the accommodation.
In the case of a conventional battery module, foam-shaped pads are disposed between battery cells, and such battery cells are accommodated in a module frame in a pressed state. In order to apply a predetermined pressing force to the battery cells, the battery cells are accommodated in the module frame while being strongly pressed. When the thickness of the battery cell is large, a large pressing force is required during accommodation, which may cause problems such as damage to the pouch case of the battery cell.
Unlike the conventional battery module, the battery module 100a according to the present embodiment can minimize the possibility of battery cells 100 being damaged during the accommodation process because the battery cell stack 120 having the tube 300 of which inside is empty, is accommodated in the module frame 200. Since it is sufficient to press the battery cells 110 by injecting the fluid F into the tubes 300 after accommodation, there is no need to strongly press the battery cells 110 during the accommodation process. Therefore, the possibility of damage to the battery cell 110 can be reduced.
Further, according to the present embodiment, after the initial pressing of the battery cell 110 is completed by injecting a fluid into the tube 300, a thermal resin can be injected through the injection hole 200H to form a thermal resin layer 400. As mentioned above, since thermal resin has adhesive properties, the cured thermal resin layer 400 is in a state of being adhered to one side of the battery cell 110. Therefore, in the present embodiment, the thermal resin layer 400 is formed after completion of the initial pressing, and thus, even if swelling of the battery cells 110 occurs, damage to the adhesive portion between the battery cells 110 and the thermal resin layer 400 can be reduced.
Taken together, the battery module 100a according to this embodiment adjusts the process of injecting the fluid F into the tube 300 and the process of injecting the thermal resin into the module frame 200, thereby attempting to minimize the occurrence of damage during the process of accommodating the battery cell 110 and the subsequent process of swelling of the battery cell 110. Further, by adjusting the pressure and amount of the fluid (F) flowing into the tube 300, the pressing force applied to the battery cell 110 can be maintained in an optimum state. Further, in the case of an all-solid-state battery or a pure Si battery, the performance of the battery cell is well exhibited when the initial pressing force is high. In order to increase the initial pressing force, a pressing means using a fluid can be used as in the present embodiment. In addition, as will be described later, even if the battery cell expands, the pressure can be relieved without continuously increasing the pressing force while the fluid coming out of the tube. Therefore, deformation of the battery module can be alleviated, and thus, the risk of structural damage can be reduced.
Referring to
First, referring to
Meanwhile, referring to
Meanwhile, referring to
A method of manufacturing the battery module 100a according to an embodiment of the present disclosure will be described below with reference to
Referring to
In the assembly step, end plates 900 are located on the opened one side and the other side of the module frame 200 so as to cover the battery cell stack 120, and the corresponding edges of the end plates 900 and the module frame can be welded.
Meanwhile, as described above, the tube 300 may be located between the battery cells 110 or located outside the battery cell 110 disposed on the outermost side. In the assembly step, the tube 300 is in a state where the inside is empty, without being filled with fluid.
A through hole 200TH is formed in the module frame 200, and the tube 300 includes an injection part 310 connected to an external fluid supply device 800 via the through hole 200TH. The specific configuration of the fluid supply device 800 or the connection shape between the tube 300 and the fluid supply device 800 overlaps with the contents described above, and thus, a detailed description thereof will be omitted.
As shown in
Next, referring to
More specifically, an injection hole 200H is formed on the one surface of the module frame 200, and in the resin injection step, the thermal resin may be injected through the injection hole 200H.
As an example, an injection hole 200H is formed in the lower surface part 240 of the module frame 200, and the thermal resin may be injected between the battery cell stack 120 and the lower surface part 240 of the module frame 200. The injection device 810 may inject a thermal resin between the battery cell stack 120 and the lower surface portion 240 of the module frame 200 through the injection hole 200H.
The injected thermal resin can be cured to form a thermal resin layer 400. The thermal resin may include a thermally conductive adhesive material, and may adhere to one side of the battery cells 110 while being cured.
At this time, the resin injection step may be performed after the initial pressing step. In the present embodiment, the resin injection step is performed after completion of the initial pressing step, and thus, even if swelling of the battery cells 110 occurs, damage to the adhesion between the battery cells 110 and the thermal resin layer 400 can be reduced.
Next, a battery module 100b according to another embodiment of the present disclosure and a manufacturing method thereof will be described in detail with reference to
Referring to
At this time, the battery module 100b may further include a heat transfer member located between the battery cell stack 120 and one surface of the module frame 200. The heat transfer member according to the present embodiment may include a thermal pad 500. One surface of the module frame 200 may mean one of the walls constituting the module frame 200, that is, one of the first side surface part 210, the second side surface part 220, the upper surface part 230 and the lower surface part 240.
As an example, a thermal pad 500 as a heat transfer member may be located between the battery cell stack 120 and the lower surface part 240 of the module frame 200.
One side of the battery cells 110 is in contact with the thermal pad 500, with the battery cells 110 are slidable on the thermal pad 500 in the stacking direction of the battery cells 110. The thermal pad 500 has no adhesive properties, unlike the thermal resin layer 400 described above. Therefore, even if one side of the battery cells 110 is in contact with the thermal pad 500, the battery cells 110 are not in a state of being adhered and fixed to the thermal pad 500.
The thermal pad 500 may include a material having high thermal conductivity, and may have a flat pad shape. One surface of the thermal pad 500 is disposed parallel to the stacking direction of the battery cells 110, so that one side of each battery cell 110 can contact the thermal pad 500. Such a thermal pad 500 may include a silicon material or an acrylic material having good thermal conductivity. Heat generated in the battery cells 110 may be dissipated to the outside through the thermal pad 500 on one side of the battery cell 110.
Even if swelling of the battery cells 110 occurs, the battery cells 110 are in a state of being not adhered to the thermal pad 500, and thus, the battery cells 110 can slide in the stacking direction of the battery cells 110. That is, in
Thereby, damage to the battery cells 110 can be prevented even if swelling occurs, and not only the pressure deviation between the battery cells 110 but also the pressure deviation within the battery cells 110 can be reduced.
In particular, even if the fluid F flows into the tube 300 after the battery cell stack 120 is disposed inside the module frame 200, the battery cells 110 are not restricted by the thermal pad 500 and thus, the variation in pressing force generated in the battery cells 110 can be minimized.
Meanwhile, the battery module 100b according to the present embodiment may further include at least one of a compression pad 600 and a cooling plate 700 disposed adjacent to the battery cell 110.
Specifically, a compression pad 600 or a cooling plate 700 may be disposed between the battery cells 110 or outside the battery cell 110 located on the outermost side. The compression pad 600 is a foam-shaped member, and can partially absorb expansion displacement during swelling of the battery cell 110. Since this embodiment includes the tube 300 into which the fluid F flows, the number of compression pads 600 can be reduced compared to a conventional case.
The cooling plate 700 may be disposed so as to cover the battery body 113 of the battery cell 110 (see
Since the cooling plate 700 covers the battery body 113 (see
A method of manufacturing the battery module 100b according to an embodiment of the present disclosure will be described below. However, the parts that overlap with the contents described above will be omitted.
Referring to
A through hole 200TH is formed in the module frame 200, and the tube 300 includes an injection part 310 connected to an external fluid supply device 800 via the through hole 200TH. In the initial pressurization step, the fluid supply device 800 injects a fluid F into the tube 300 via the injection part 310.
At this time, in the assembly step, the thermal pad 500 may be accommodated inside the module frame 200. The thermal pad 500 may be located between one surface of the battery cell stack 120 and the module frame 200. As an example, the thermal pad 500 may be located between the battery cell stack 120 and the lower surface part 240 of the module frame 200.
When the battery cell stack 120 including the tube 300 is accommodated inside the module frame 200, the thermal pad 500 may also be accommodated inside the module frame 200. Unlike the battery module 100a in which thermal resin is injected, the thermal pad 500 is accommodated, and thus, an injection hole does not need to be formed on one surface of the module frame 200.
As described above, one side of the battery cells 110 is in contact with the thermal pad 500, wherein the battery cells 110 are slidable on the thermal pad 500 in the stacking direction of the battery cells 110. The details concerning overlap with the contents previously described, and thus, are omitted.
Since a thermal pad 500 that contacts the battery cell but does not adhere to it is disposed, it is possible to prevent the battery cell 110 from being damaged even if even if the initial pressing step is performed or swelling of the battery cell 110 occurs subsequently. Moreover, both the pressure deviation between the battery cells 110 and the pressure deviation within the battery cell 110 can be reduced.
A battery module including a check valve according to another embodiment of the present disclosure will be described below.
Referring to
The battery module according to the present embodiment may further include a check valve 320 connected to the tube 300. As an example, the tube 300 may be connected to an external device (not shown) through a through hole 200TH formed in the upper surface part 230 of the module frame 200. A check valve 320 may be provided in a path where the tube 300 is connected to an external device (not shown). Although the check valve 320 is shown as being located outside the module frame 200, it can also be located inside the module frame 200.
The check valve 320 is a valve that allows fluid to flow in only one direction and not to flow in the opposite direction. As an example, the check valve 320 may include a body tube 321, a spring 322 and a valve disc 323. When the pressure of the fluid inside the tube 300 increases, the valve disc 323 opens while the spring 322 is compressed. Thereby, the fluid may be discharged from the tube 300. However, this shows one example of the check valve 320, and any configuration that allows fluid to flow in only one direction according to an increase in internal fluid pressure can be applied without limitation.
When swelling occurs and the battery cell 110 expands, pressure is applied to the tube 300. When the pressure applied to the tube 300 and the fluid therein exceeds a predetermined value, the check valve 320 is opened and fluid can be discharged from tube 300. That is, the fluid in tube 300 can be gradually discharged during swelling of the battery cell. Even when the battery cell expands, the pressure on the battery cell 110 does not continue to increase while the fluid coming out of the tube 300, and the pressure can be relieved. Therefore, deformation of the battery module can be alleviated, thereby reducing the risk of structural damage.
Meanwhile, the battery cell according to this embodiment may be a battery cell containing pure Si. In order for such a battery cell to exhibit its performance smoothly, the initial pressing force should be 10 times or more that of the existing battery cell. Similarly to the battery module according to the present embodiment, the pressing method through the tube 300 into which the fluid F is injected can constantly apply a high pressurizing force so that the battery cell containing pure Si can exhibit optimal performance. That is, the battery module according to this embodiment has a structure suitable for use in a battery cell containing pure Si.
A design method of the battery module according to the present embodiment will be described below with reference to
Referring to
At this time, the module stiffness curve C1 caused by the module frame 200 and the P-D (pressure-displacement) curve C3 of the battery cell stack 120 showing the swelling characteristics of the battery cells 110 are calculated, respectively, and they are fitted into one graph. Then, the swelling behavior of the battery module can be predicted by a method of finding an equilibrium point (intersection point) between the two curves.
In each of the module stiffness curves C1, C1′ and C″ and the P-D curve C3 of the battery cell stack, the X-axis corresponds to deformation ratio and the unit may be %. The Y-axis corresponds to the applied surface pressure and the unit may be MPa.
The intersection points P. P′ and P″ between the module stiffness curves C1, C1′ and C″ and the P-D curve C3 of the battery cell stack corresponds to the point where the behavior due to swelling of the battery cell stack 120 and the behavior due to deformation of the module frame 200 are balanced. In other words, in the case of a battery module in which a battery cell stack exhibiting a specific P-D curve C3 in an EOL (End of Life) state is accommodated in a module frame exhibiting a specific module stiffness curve C1, the corresponding battery module can be predicted to have deformation ratio and surface pressure corresponding to the intersection points P, P′ and P″ in the EOL state. That is, the battery module is deformed by the amount corresponding to the X-axis value of the intersection points P, P′ and P″ in the width direction in the EOL state, and the battery cells 110 and the module frame 200 receive surface pressure as much as the Y-axis value of the intersection points P, P′ and P″.
At this time, as shown in
As shown in
As shown in
Meanwhile, referring to
The module stiffness curve C1 will be specifically described below. As described above, the module stiffness curve C1 is a graph showing the relationship between the extent to which the width of the module frame 200 changes according to the direction in which the battery cells 110 are stacked and the load applied to the module frame 200. From the viewpoint of the module stiffness curve C1, the X axis corresponds to the deformation ratio % of the module frame 200 along the width direction. The deformation ratio may be calculated based on the width of the module frame 200 deformed along the width direction, relative to the width of the module frame 200 before deformation. For example, the deformation ratio may be calculated as the ratio of the extent to which the width of the module frame 200 is deformed relative to the width of the module frame 200 before deformation. From the viewpoint of the module stiffness curve C1, the Y-axis may correspond to the surface pressure (MPa) applied to the side surfaces 210 and 220 of the module frame 200 according to the deformation rate of the module frame 200.
In order to calculate the module stiffness curve C1, first, the frame stiffness curve may be calculated. The frame stiffness curve is a graph of the relationship between the deformation ratio of the module frame 200 and the surface pressure applied to the module frame 200. Such frame stiffness curves can be obtained through several actual tests or simulations. For example, an actual force is applied to the module frame 200 to measure the degree of deformation of the module frame 200 in the width direction. A frame stiffness curve can be derived by repeating the process while changing the applied force. A module stiffness curve C1 can be derived by considering the influence of the compression pad 600 on the frame stiffness curve. Specifically, the degree of compression of the compression pad 600 relative to the surface pressure applied to the compression pad 600 and the number of compression pads 600 can be reflected in the frame stiffness curve to finally derive the module stiffness curve C1.
Below, the P-D curve C3 of the battery cell stack will be described in detail. As described above, the P-D curve C3 of the battery cell stack is a graph showing the relationship of the surface pressure received by the battery cell 110 according to the degree of change when the thickness of the battery cell 110 changes due to swelling. From the viewpoint of the P-D curve C3 of the battery cell stack, the X axis may correspond to the deformation ratio (%) along the width direction of the battery cell stack 120, and the Y-axis may correspond to surface pressure (MPa) applied to the battery cells 110 included in the battery cell stack 120.
Below, the process of calculating the P-D curve C3 of the battery cell stack will be described in detail with reference to
Referring to
Referring to
Referring to
Looking at the swelling behavior of the battery module that is predicted according to the above method, it is predicted that in the EOL state, the battery module of Example 1 is deformed in the width direction by 5.4%, and the internal battery cells and module frame receive a surface pressure of 0.8 MPa. Moreover, it is predicted that in the EOL state, the battery module of Example 2 is deformed in the width direction by 6.7%, and the internal battery cells and module frame receive a surface pressure of 0.71 MPa. Further, it is predicted that in the EOL state, the battery module of Example 3 is deformed in the width direction by 6.1%, and the internal battery cells and module frame receive a surface pressure of 0.29 MPa. Finally, it is predicted that in the EOL state, the battery module of Example 4 is deformed in the width direction by 9.3%, and the internal battery cells and the module frame receive a surface pressure of 0.44 MPa.
All of the battery modules of Examples 1 to 4 exhibit the feature that in the EOL (End of Life) state, the deformation rate in the direction in which the battery cells are stacked is 12% or less, and the surface pressure applied to the battery cells is 0.9 MPa or less. Further, the module stiffness curves of the battery modules of Examples 1 to 4 are calculated in the range of slope (MPa/%) of 0.00417 or more and 0.225 or less. That is, the module stiffness curves of the battery modules of Examples 1 to 4 may be formed in a range between the lower limit module stiffness curve C1b having a slope (Sb) value of 0.00417 MPa/% and the upper limit module stiffness curve C1a having a slope (Sa) value of 0.225 MPa/%.
The terms representing directions such as the front side, the rear side, the left side, the right side, the upper side, and the lower side have been used in the present embodiment, but the terms used are provided simply for convenience of description and may become different according to the position of an object, the position of an observer, or the like.
The one or more battery modules according to embodiments of the present disclosure described above can be mounted together with various control and protection systems such as a BMS (battery management system), a BDU (battery disconnect unit), and a cooling system to form a battery pack.
The battery module or the battery pack can be applied to various devices. For example, it can be applied to vehicle means such as an electric bike, an electric vehicle, and a hybrid electric vehicle, or an ESS (Energy Storage System) and may be applied to various devices capable of using a secondary battery, without being limited thereto.
Although the invention has been described in detail above with reference to preferred embodiments of the present disclosure, the scope of the present disclosure is not limited thereto, and various modifications and improvements can be made by those skilled in the art using the basic concepts of the present disclosure, which are defined in the appended claims, which also falls within the scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0009058 | Jan 2022 | KR | national |
| 10-2023-0008310 | Jan 2023 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2023/001069 | 1/20/2023 | WO |
