Battery module and manufacturing method of the same

Abstract

To provide a battery module capable of applying a uniform pressure to a battery cell even when a change in thickness due to charge and discharge of the battery cell is large and capable of being miniaturized, and a manufacturing method of the same.SOLUTION: A battery module includes: a cell stacked body in which a plurality of battery cells are stacked; a pair of end plates disposed at both ends in a stacking direction of the cell stacked body; and a cushion disposed at least one of between the battery cell and the battery cell and between the battery cell and the end plates. The cushion is a first cushioning material having an inner elastic container and an outer elastic container housing the inner elastic container. The inner elastic container is filled with gas, and liquid is filled between the inner elastic container and the outer elastic container. The outer elastic container is connected to a liquid pipe, and the liquid pipe is a circulation pipe having an accumulator.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery module and a manufacturing method thereof. [Background technology]

[0002] In recent years, research and development has been conducted on battery modules that contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. A battery module is a modular assembly of multiple battery cells, and generally includes a cell stack in which multiple battery cells are stacked, and a pair of end plates arranged on both ends of the cell stack in the stacking direction. Battery modules are used in applications requiring high current and high voltage, such as motor drive for electric vehicles and hybrid electric vehicles.

[0003] In battery modules, it has been considered to place cushioning materials between battery cells or between the cell stack and the end plates to apply pressure in the stacking direction of the battery cells.Known cushioning materials include a cushioning material having a deformable chamber and a system that supplies a fluid to deform the chamber (Patent Document 1), and elastic spring bodies such as leaf springs and liquid springs (Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-64848 [Patent Document 2] Patent Publication No. 2021-96974 [Patent Document 3] European Patent Application Publication No. 3886202 Summary of the Invention [Problem to be solved by the invention]

[0005] Increasing electrical capacity and miniaturization are key challenges in battery module technology. To improve the electrical capacity of a battery module, it is effective to apply uniform pressure to each battery cell incorporated in the battery module via a cushioning material. Fluid cushions, which are filled with fluid, have high internal pressure uniformity, allowing for highly uniform pressure application to the entire battery cell. Furthermore, second buffer materials using liquids as the fluid have high heat absorption properties, which are effective in regulating the temperature of the battery cells. Meanwhile, lithium metal batteries, which use lithium ions as a charge transfer medium for battery cells, are being considered. During charging, lithium metal is deposited in the negative electrode layer, and during discharging, the lithium metal migrates as lithium ions to the positive electrode layer. These lithium metal batteries experience significant thickness changes during charging and discharging. Therefore, to apply uniform pressure to a lithium metal battery using a fluid cushion, it is necessary to reduce the amount of fluid inside during charging and increase the amount of fluid inside during discharging. However, using a fluid tank to adjust the amount of fluid in the fluid cushion makes it difficult to miniaturize the battery module.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a battery module and a manufacturing method thereof that can apply uniform pressure to battery cells and can be miniaturized even when the thickness of the battery cells changes significantly due to charging and discharging, thereby contributing to energy efficiency. [Means for solving the problem]

[0007] The inventors discovered that the above-mentioned problems could be solved by using a double structure having an inner elastic container and an outer elastic container between battery cells or between a battery cell and an end plate, with the inner elastic container filled with gas and a first cushioning material filled with liquid disposed between the outer surface of the inner elastic container and the inner surface of the outer elastic container, and connecting the outer elastic container to a circulation pipe having an accumulator, and thus completed the present invention. Accordingly, the present invention provides the following.

[0008] (1) A battery module including: a cell stack formed by stacking a plurality of battery cells; a pair of end plates arranged at both ends of the cell stack in the stacking direction; and a first cushioning material arranged at least one between the battery cells and between the battery cells and the end plates, wherein the first cushioning material has an inner elastic container and an outer elastic container that houses the inner elastic container, the interior of the inner elastic container is filled with gas, and a liquid is filled between the outer surface of the inner elastic container and the inner surface of the outer elastic container, the outer elastic container is connected to a liquid piping, and the liquid piping is a circulation piping having an accumulator.

[0009] According to the battery module (1), when the thickness of the battery cell increases due to charging and the first buffer material is pressed, the increase in the pressure of the liquid filled between the inner elastic container and the outer elastic container can be suppressed by the contraction of the inner elastic container and the accumulation of pressure in the accumulator. Therefore, even if the thickness of the battery cell changes significantly due to charging and discharging, uniform pressure can be applied to the battery cell. Furthermore, since the accumulator is used as a tank for storing the liquid, miniaturization is easy. Furthermore, the liquid filled inside the first buffer material circulates through the circulation pipe, keeping the liquid temperature uniform, thereby suppressing the temperature increase of the battery cell.

[0010] (2) The battery module described in (1), wherein the volume of the inner elastic container of the first cushioning material is in the range of 30 or more and 70 or less when the total volume of the inner elastic container and the outer elastic container is 100.

[0011] According to the battery module (2), since the volume of the inner elastic container of the first cushioning material is within the above range, it is possible to achieve a better balance between suppressing the increase in the hydraulic pressure of the liquid filled inside the first cushioning material and suppressing the temperature increase of the battery cell due to the liquid.

[0012] (3) The battery module described in (1) further comprises a second buffer material connected to the liquid piping and filled with liquid, which is arranged at least either between the battery cells or between the battery cells and the end plate.

[0013] According to the battery module of (3), the inside is filled with only liquid and has the second buffer material with high heat absorption efficiency, so that the temperature rise of the battery cells can be more reliably suppressed.

[0014] (4) The battery module described in (3), wherein the volume of the inner elastic container of the first cushioning material is in the range of 50 or more and 90 or less when the total volume of the inner elastic container and the outer elastic container is 100.

[0015] According to the battery module (4), the volume of the inner elastic container of the first cushioning material is within the above range, and the volume of the inner elastic container is large, so that the increase in the liquid pressure of the liquid filled inside the first cushioning material and the second cushioning material can be more reliably suppressed.

[0016] (5) A battery module described in (3) or (4), wherein the first cushioning material is arranged between one of the pair of end plates and the battery cell, and the second cushioning material is arranged between the battery cell and the battery cell.

[0017] According to the battery module of (5), the second buffer material is disposed between the battery cells, so that the temperature rise of the battery cells can be more reliably suppressed.

[0018] (6) A method for manufacturing a battery module, including the steps of: preparing a plurality of battery cells, a pair of end plates, and a dual structure having an inner elastic container and an outer elastic container that houses the inner elastic container; stacking the plurality of battery cells, arranging a pair of end plates at both ends of the stacking direction of the obtained cell stack, and arranging the dual structure at least one between the battery cells and between the battery cells and the end plates; filling the inner elastic container with gas; and connecting a circulation pipe having an accumulator to the outer elastic container and filling a liquid between the inner elastic container and the outer elastic container.

[0019] According to the battery module (6), the battery module having the first cushioning material can be manufactured industrially advantageously. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a battery module and a manufacturing method thereof that can apply uniform pressure to battery cells even when the thickness of the battery cells changes significantly due to charging and discharging, and that can be made smaller. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic diagram illustrating a battery module according to a first embodiment of the present invention. [Figure 2] 1 is a cross-sectional view of a battery cell that can be used in a battery module according to a first embodiment of the present invention. [Figure 3] 2 is a schematic diagram illustrating a charging state of the battery module shown in FIG. 1. FIG. [Figure 4] FIG. 4 is a schematic diagram illustrating a battery module according to a second embodiment of the present invention. [Figure 5] 5 is a schematic diagram illustrating a charging state of the battery module shown in FIG. 4. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below are merely examples of the present invention, and the present invention is not limited to the following.

[0023] [First embodiment] FIG. 1 is a schematic diagram illustrating a battery module according to a first embodiment of the present invention. As shown in Fig. 1, the battery module 100 of this embodiment includes a cell stack 1, a pair of end plates 2a, 2b, and a first cushioning material 3. The cell stack 1 is a stack of a plurality of battery cells 10 (two in Fig. 1). The end plates 2a, 2b are arranged at both ends of the cell stack 1 in the stacking direction (X direction in Fig. 1). The first cushioning material 3 is arranged between the battery cells 10 and between the battery cell 10 and the end plates 2a, 2b. The end plates 2a, 2b are fixed by restraining devices such as bind bars.

[0024] The battery cell 10 is a lithium metal battery that uses lithium ions as a charge transfer medium. As shown in FIG. 2, the battery cell 10 includes an electrode stack 18 in which a positive electrode layer 11 and a negative electrode layer 14 are stacked with a solid electrolyte layer 17 interposed therebetween, and an exterior body 19 that houses the electrode stack 18. The positive electrode layer 11 includes a positive electrode current collector 12 and a positive electrode active material layer 13. The negative electrode layer 14 includes a negative electrode current collector 15 and a metal layer 16. When the battery cell 10 is charged, lithium ions released from the positive electrode active material layer 13 pass through the solid electrolyte layer 17 and are deposited on the surface of the metal layer 16 of the negative electrode layer 14, forming a lithium deposit layer, and the thickness of the negative electrode layer 14 increases. The lithium deposit layer acts as a negative electrode active material layer and is lost by releasing lithium ions during discharge. Therefore, the volume of the battery cell 10 changes during charging and discharging. Therefore, the pressure applied from the battery cells 10 to the first buffer material 3 changes with charging and discharging. The stacking direction of the electrode stack 18 is the same as the stacking direction of the cell stack 1. That is, the multiple battery cells 10 of the cell stack 1 are stacked along the stacking direction of the electrode stacks 18. Note that, in the battery cell 10 shown in FIG. 2 , one electrode stack 18 is housed in the exterior body 19, but multiple electrode stacks 18 may be housed in the exterior body 19.

[0025] The positive electrode current collector 12 is not particularly limited in material or shape as long as it has the function of collecting current from the positive electrode layer 11. Examples of materials for the positive electrode current collector 12 include aluminum, aluminum alloys, stainless steel, nickel, iron, and titanium, and among these, aluminum, aluminum alloys, and stainless steel are preferred. Examples of the shape of the positive electrode current collector 12 include foil and plate shapes.

[0026] The positive electrode active material layer 13 contains at least one type of positive electrode active material. There are no particular limitations on the positive electrode active material, and any material used in the positive electrode layers of general solid-state secondary batteries can be used. As the positive electrode active material, for example, a layered active material containing lithium, a spinel-type active material, an olivine-type active material, etc. can be used. Specific examples of the positive electrode active material include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), LiNi p Mnq Co r O2(p+q+r=1), LiNi p Al q Co r O2 (p+q+r=1), lithium manganese oxide (LiMn2O4), Li 1+x Mn 2-x-y Examples include heteroelement-substituted Li-Mn spinel represented by MO4 (x+y=2, M=at least one selected from Al, Mg, Co, Fe, Ni, and Zn), lithium titanate (oxide containing Li and Ti), and lithium metal phosphate (LiMPO4, M=at least one selected from Fe, Mn, Co, and Ni).

[0027] The positive electrode active material layer 13 may optionally contain a solid electrolyte in order to improve lithium ion conductivity. It may also optionally contain a conductive additive in order to improve conductivity. Furthermore, it may also optionally contain a binder in order to achieve flexibility. There are no particular restrictions on the solid electrolyte, conductive additive, and binder, and those used in the positive electrode layers of general solid secondary batteries may be used.

[0028] The material of the positive electrode lead wire 11a may be the same as or different from the material of the positive electrode current collector 12. The positive electrode lead wire 11a may be integrally connected to the positive electrode current collector 12.

[0029] The material and shape of the negative electrode current collector 15 are not particularly limited as long as it has the function of collecting current from the negative electrode layer 14. Examples of materials for the negative electrode current collector 15 include nickel, copper, and stainless steel. Examples of the shape of the negative electrode current collector 15 include a foil shape, a plate shape, and the like.

[0030] The metal layer 16 is not particularly limited in material or shape as long as it has the function of densely depositing lithium ions. A metallic lithium layer or a layer of a metal that forms an alloy with lithium can be used as the metal layer 16. Examples of metals that form an alloy with lithium include Mg, Si, Au, Ag, In, Ge, Sn, Pb, Al, and Zn. The metal that forms the metal layer 16 may be in the form of a powder or a thin film. By using the negative electrode layer 14 having this metal layer 16, a uniform lithium deposit layer can be formed on the surface of the metal layer 16.

[0031] The material of the negative electrode lead wire 14a may be the same as or different from the material of the negative electrode current collector 15. The negative electrode lead wire 14a may be integrally connected to the negative electrode current collector 15.

[0032] The solid electrolyte layer 17 contains at least one type of solid electrolyte. The solid electrolyte is not particularly limited as long as it has lithium ion conductivity, and examples thereof include sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes. Examples of sulfide solid electrolytes include Li2S-P2S5 and Li2S-P2S5-LiI. The sulfide solid electrolyte may have an argyrodite-type crystal structure. Examples of oxide solid electrolytes include NASICON-type oxides, garnet-type oxides, and perovskite-type oxides. Examples of NASICON-type oxides include oxides containing Li, Al, Ti, P, and O (e.g., Li 1.5 Al 0.5 Ti 1.5 Examples of garnet-type oxides include oxides containing Li, La, Zr, and O (e.g., LiLaZrO 12 Examples of perovskite oxides include oxides containing Li, La, Ti, and O (for example, LiLaTiO3).

[0033] The exterior body 19 is expandable and contractible in accordance with changes in the volume of the battery cells 10 due to charging and discharging. A laminate film can be used as the material for the exterior body 19. The laminate film can be a three-layer film having an inner resin layer, a metal layer, and an outer resin layer stacked in this order from the inside. The outer resin layer can be, for example, a polyamide (nylon) layer or a polyethylene terephthalate (PET) layer, the metal layer can be, for example, an aluminum layer, and the inner resin layer can be, for example, a polyethylene layer or a polypropylene layer.

[0034] The end plates 2a and 2b act to restrain the cell stack 1 in the stacking direction. The restraining force of the end plates 2a and 2b makes it possible to adjust the surface pressure applied to the cell stack via the first cushioning material 3. There are no particular restrictions on the material of the end plates 2a and 2b, and various materials used for end plates for battery modules can be used.

[0035] The first cushioning material 3 has the effect of uniforming the surface pressure applied to the battery cells 10. The surface pressure applied to the battery cells 10 may be, for example, in the range of 1.0 MPa to 2.5 MPa.

[0036] The first cushioning material 3 has a dual structure having an inner elastic container 31 and an outer elastic container 33 that houses the inner elastic container 31. The interior of the inner elastic container 31 is filled with a gas 32. The gas 32 is filled in a sealed state. A liquid 34 is filled between the outer surface of the inner elastic container 31 and the inner surface of the outer elastic container 33.

[0037] In the first buffer material, the volume of the inner elastic container 31 may be, for example, in the range of 30 to 70, where the total volume of the inner elastic container 31 and the outer elastic container 33 is 100. The volume of the inner elastic container 31 is the volume filled with the gas 32. The volume of the outer elastic container 33 is the volume between the outer surface of the inner elastic container 31 and the inner surface of the outer elastic container 33, i.e., the volume filled with the liquid 34. When the volume of the inner elastic container 31 is 30 or more, the inner elastic container 31 can absorb the pressure when the outer elastic container 33 is pressurized by contracting, thereby suppressing an increase in the liquid pressure of the liquid 34. Furthermore, when the volume of the inner elastic container 31 is 70 or less, an increase in the temperature of the battery cell 10 due to the liquid 34 can be suppressed.

[0038] The inner elastic container 31 and the outer elastic container 33 are each formed from a contractible elastic body. Materials that can be used for the inner elastic container 31 and the outer elastic container 33 include, for example, rubber, elastomer, and laminate film. The gas 32 can be, for example, air or a non-flammable gas (nitrogen, carbon dioxide, etc.). The liquid 34 can be, for example, mineral-based hydraulic oil, phosphate ester-based hydraulic oil, water, or a glycol-based solvent.

[0039] A liquid pipe 4 is connected to the opposing side of the outer elastic container 33. The liquid pipe 4 is a circulation pipe having an accumulator 41 and a pump 42. The accumulator 41 suppresses an increase in the liquid pressure of the liquid 34 in the first cushioning material 3 by compressing and accumulating the gas inside. The accumulator 41 may have a gas volume, for example, between 30 and 70, when the total volume is 100. The pump 42 circulates the liquid 34 in the liquid pipe 4 and the first cushioning material 3. Circulating the liquid 34 makes it possible to uniformize the liquid pressure and liquid temperature of the liquid 34 in the liquid pipe 4 and the first cushioning material 3. Uniform liquid pressure uniformly distributes the pressure applied to the battery cells 10 from the first cushioning material 3. Uniform water temperature uniformly distributes the temperature of the battery cells 10.

[0040] FIG. 3 is a schematic diagram illustrating the charging state of the battery module 100. As shown in FIG. In the charged battery module 100a, the thickness of the battery cells 10a increases. The increased thickness of the battery cells 10a presses the first cushioning material 3a, causing it to decrease in thickness. The decrease in the thickness of the first cushioning material 3a increases the hydraulic pressure of the liquid 34 in the first cushioning material 3a. When the hydraulic pressure of the liquid 34 in the first cushioning material 3a increases, the inner elastic container 31 is pressurized and contracts, and some of the liquid 34 in the first cushioning material 3a flows out to the accumulator 41 via the liquid piping 4. The accumulator 41 accumulates the increased hydraulic pressure by contracting the gas. Therefore, even if the thickness of the battery cells 10a increases, the internal pressure of the first cushioning material 3a does not increase excessively, and a uniform pressure can be applied to the battery cells 10a.

[0041] The inner elastic container 31, together with the accumulator 41, has the effect of suppressing an increase in the hydraulic pressure of the liquid 34 in the first cushioning material 3. From the viewpoint of miniaturizing the accumulator 41, it is effective to increase the size of the inner elastic container 31 and the amount of gas in the first cushioning material 3. On the other hand, the liquid 34 absorbs heat from the battery cells 10 and suppresses an increase in the temperature of the battery cells 10. From the viewpoint of suppressing an increase in the temperature of the battery cells 10, it is effective to increase the amount of liquid in the first cushioning material 3 by widening the gap between the inner elastic container 31 and the outer elastic container 33. For this reason, the size of the inner elastic container 31 may be changed depending on the location of the first cushioning material 3. For example, the first cushioning material 3 disposed between the battery cells 10, which are prone to temperature rise, may have a relatively small inner elastic container 31 and a wide gap between the inner elastic container 31 and the outer elastic container 33. Furthermore, the first cushioning material 3 disposed between the battery cells 10 and the end plates 2a, 2b may have a relatively large inner elastic container 31. In this embodiment, the first cushioning material 3 is disposed both between the battery cells 10 and between the battery cells 10 and the end plates 2a, 2b, but the position of the first cushioning material 3 is not limited to this. The first cushioning material 3 may be disposed in at least one location between the battery cells 10 and between the battery cells 10 and the end plates 2a, 2b.

[0042] The battery module 100 of this embodiment can be manufactured, for example, as follows.

[0043] First, a plurality of battery cells 10, a pair of end plates 2a, 2b, and a dual structure having an inner elastic container 31 and an outer elastic container 33 that houses the inner elastic container 31 are prepared.

[0044] Next, a plurality of battery cells 10 are stacked, and a pair of end plates 2a, 2b are arranged at both ends in the stacking direction of the obtained cell stack 1, and a dual structure is arranged between the battery cells 10 and between the battery cells 10 and the end plates 2a, 2b. After the arrangement is complete, the end plates 2a, 2b may be fixed with restraining devices such as bind bars.

[0045] Next, the gas 32 is filled into the inner elastic container 31. The pressure of the gas 32 when filling the inner elastic container 31 may be in the range of 0.1 MPa to 0.9 MPa. The gas 32 can be filled into the inner elastic container 31 by, for example, the following methods (1) to (3). (1) A pipe for supplying gas is provided in advance to the inner elastic container 31, and after the inner elastic container 31 is filled with gas 32 through the pipe, a valve / joint with a check valve structure is provided at the tip of the pipe. (2) A pipe for supplying gas is provided in advance to the inner elastic container 31, and after the inner elastic container 31 is filled with the gas 32 through the pipe, the pipe is sealed by heat or pressure. (3) A pipe for supplying gas is provided in advance in the thermoplastic inner elastic container 31, and the inner elastic container 31 is filled with gas 32 through the pipe. After that, the area around the pipe of the inner elastic container 31 is heated, and the inner elastic container 31 is sealed while the pipe is removed.

[0046] Next, a circulation pipe having an accumulator 41 is connected to the outer elastic container 33, and liquid 34 is filled between the inner elastic container 31 and the outer elastic container 33. After filling with liquid 34, the internal pressure of the accumulator 41 may be adjusted to be within a range of 1.0 MPa or more and 2.5 MPa or less.

[0047] According to the battery module 100 of this embodiment configured as described above, when the thickness of the battery cells 10 increases due to charging and the first buffer material 3 is pressed, the increase in the internal pressure of the liquid filled in the first buffer material 3 can be suppressed by the contraction of the inner elastic container 31 and the accumulation of pressure in the accumulator 41. Therefore, even if the thickness of the battery cells 10 changes significantly due to charging and discharging, a uniform pressure can be applied to the battery cells 10. Furthermore, since the accumulator 41 is used as a tank for storing the liquid 34, miniaturization is facilitated. Furthermore, the liquid filled inside the first buffer material circulates in the circulation pipe, making the liquid temperature uniform, thereby suppressing the temperature increase of the battery cells.

[0048] In the battery module 100 of this embodiment, when the total volume of the inner elastic container 31 and the outer elastic container 33 is 100, if the volume of the inner elastic container 31 is within the above range, it is possible to achieve a better balance between suppressing the increase in the liquid pressure of the liquid 34 filled inside the first cushioning material 31 and suppressing the temperature increase of the battery cell 10 due to the liquid 34.

[0049] According to the manufacturing method of the battery module 100 of this embodiment, the above-described battery module 100 can be manufactured industrially advantageously.

[0050] [Second embodiment] Fig. 4 is a schematic diagram illustrating a battery module according to a second embodiment of the present invention, and Fig. 5 is a schematic diagram illustrating the charging state of the battery module shown in Fig. 4.

[0051] 4, the battery module 101 of this embodiment is the same as the battery module 100 of the first embodiment except that second buffer materials 5 are arranged between the battery cells 10 and between the cell stack 1 and the end plate 2b. Therefore, the same reference numerals are used to designate components common to the battery module 100 of the first embodiment, and descriptions thereof will be omitted.

[0052] The second cushioning material 5 is a cushion filled only with liquid 34. Liquid piping 4 is arranged on opposing side surfaces of the second cushioning material 5. The liquid piping 4 is connected to opposing side surfaces of the second cushioning material 5 so that the liquid 34 inside the second cushioning material 5 is also circulated. The accumulator 41 arranged in the liquid piping 4 may have a gas volume in the range of 50 to 90 when the total volume is 100.

[0053] In the charged battery module 101a, the thickness of the battery cells 10a increases. This presses the first buffer material 3a and the second buffer material 5. The pressed first buffer material 3a decreases in thickness, and the liquid pressure of the liquid 34 in the first buffer material 3a increases. When the liquid pressure of the liquid 34 increases, the inner elastic container 31 is pressurized and contracts, and the liquid 34 flows out to the accumulator 41 through the liquid piping 4. The pressed second buffer material 5 decreases in thickness, and the liquid pressure of the liquid 34 in the second buffer material 5 increases, and the liquid 34 flows out to the accumulator 41 through the liquid piping 4. Therefore, even if the thickness of the battery cell 10a increases, the internal pressure of the first buffer material 3a and the second buffer material 5 does not increase excessively, and a uniform pressure can be applied to the battery cell 10a.

[0054] According to the battery module 101 of this embodiment configured as described above, when the thickness of the battery cells 10 increases due to charging and the first and second cushioning materials 3 and 5 are pressed, the increase in internal pressure of the first and second cushioning materials 3 and 5 can be suppressed by the contraction of the inner elastic container 31 of the first cushioning material 3 and the accumulation of pressure in the accumulator 41. Therefore, even if the thickness of the battery cells 10 changes significantly due to charging and discharging, uniform pressure can be applied to the battery cells 10. In addition, since the accumulator 41 is used as a tank for storing the liquid 34, the battery module 101 can be made smaller. Furthermore, according to the battery module 101 of this embodiment, the interior is filled with only the liquid 34, and the second cushioning materials 5, which have high heat absorption efficiency, are arranged between the battery cells 10, so the temperature increase of the battery cells 10 can be efficiently suppressed.

[0055] In the battery module 101 of this embodiment, when the total volume of the inner elastic container 31 and the outer elastic container 33 is 100, if the volume of the inner elastic container 31 is within the above range, the volume of the inner elastic container 31 is large, so that the increase in the liquid pressure of the liquid 34 filled inside the first cushioning material 3 and the second cushioning material 5 can be more reliably suppressed.

[0056] In the above embodiment, the battery cell 10 has been described as a solid-state battery having the solid electrolyte layer 17, but the battery cell 10 is not limited to this. The battery cell 10 may be, for example, a non-aqueous battery that uses an organic electrolytic solution as the electrolyte, or a polymer battery that uses a polymer gel (polymer). [Explanation of symbols]

[0057] 1 Cell stack 2a, 2b End plates 3, 3a 1st buffer material 4 Liquid piping 5 Second buffer material 10, 10a battery cells 11 Positive electrode layer 11a Positive lead wire 12 Positive electrode current collector 13 Cathode active material layer 14 negative electrode layer 14a Negative lead wire 15 Negative electrode current collector 16 metal layer 17 Solid electrolyte layer 18 Electrode laminate 19 Exterior body 31 Inner elastic container 32 Gas 33 Outer elastic container 34 liquid 41 Accumulator 42 Pump 100, 100a, 101, 101a Battery Module

Claims

1. a cell stack formed by stacking a plurality of battery cells; A pair of end plates arranged at both ends of the cell stack in the stacking direction; a first buffer material disposed at least one of between the battery cells and between the battery cells and the end plate; the first cushioning material has an inner elastic container and an outer elastic container that houses the inner elastic container, The inside of the inner elastic container is filled with gas, A liquid is filled between the outer surface of the inner elastic container and the inner surface of the outer elastic container, The outer elastic container is connected to a liquid pipe, The battery module, wherein the liquid piping is a circulation piping having an accumulator.

2. 2. The battery module of claim 1, wherein the first cushioning material has a volume of the inner elastic container in the range of 30 to 70 when the total volume of the inner elastic container and the outer elastic container is 100.

3. 2. The battery module according to claim 1, further comprising a second buffer material connected to the liquid piping and filled with liquid, the second buffer material being disposed at least one of between the battery cells and between the battery cells and the end plates.

4. 4. The battery module of claim 3, wherein the first cushioning material has a volume of the inner elastic container in the range of 50 to 90 when the total volume of the inner elastic container and the outer elastic container is 100.

5. 5. The battery module according to claim 3, wherein the first cushioning material is disposed between one of the pair of end plates and the battery cell, and the second cushioning material is disposed between the battery cell and the battery cell.

6. A step of preparing a plurality of battery cells, a pair of end plates, and a dual structure having an inner elastic container and an outer elastic container that houses the inner elastic container; a step of stacking a plurality of the battery cells, arranging a pair of end plates on both ends of the obtained cell stack in the stacking direction, and arranging the dual structure at least one between the battery cells and between the battery cells and the end plates; filling the inner elastic container with a gas; a step of connecting a circulation pipe having an accumulator to the outer elastic container and filling a liquid between the inner elastic container and the outer elastic container.

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