Battery module

Abstract

To provide a battery module using a cushioning material that is capable of exerting uniform pressure on battery cells, achieves high thermal insulation, and can be easily reduced in size.SOLUTION: A battery module includes: a battery cell stack formed by stacking a plurality of battery cells; a pair of end plates provided at both ends of the battery cell stack in the stacking direction; and a cushioning material arranged either between the battery cells, or between the battery cell stack and the end plates, or both. The cushioning material includes: a double-pack structure which includes a first pack and a second pack with an inner diameter larger than that of the first pack, and in which both ends of the first pack and the second pack are sealed and the first pack and the second pack are at least partially bonded to each other; gas filling an internal space of the first pack; and liquid filling a space between the first pack and the second pack.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery module. [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 combination of multiple battery cells, and generally includes a battery cell stack in which multiple battery cells are stacked, and a pair of end plates arranged on both ends of the battery cell stack in the stacking direction. Battery modules are used in applications requiring high current and high voltage, such as for driving the motors of electric vehicles and hybrid electric vehicles.

[0003] In battery modules, it has been considered to place cushioning material between battery cells or between the battery cell stack and the end plate 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 that deforms the chamber (Patent Document 1), and elastic springs 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 the electrical capacity of a battery module is an issue. 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. Furthermore, using a cushioning material that has heat dissipation properties to dissipate heat within the battery cell stack to the outside and heat insulation properties to suppress heat transfer between the battery cells can provide insulation in the cell stacking direction of the battery cell stack and thermal conductivity in a direction perpendicular to the cell stacking direction, making it easier to control the temperature of the battery cells. However, if the thickness of the battery cells changes locally during charging and discharging, causing the pressure applied from the battery cells to the cushioning material to increase or decrease locally, it may be difficult for the cushioning material to apply uniform pressure to the battery cells. Furthermore, to improve the electrical capacity per volume of a battery module, a small cushioning material is desirable. However, if the cushioning material is made small, it becomes difficult to achieve both heat dissipation and insulation properties, which may make it difficult to achieve the above-mentioned effect.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a battery module that uses a cushioning material that can apply uniform pressure to battery cells, has high thermal insulation properties, and is easily miniaturized, thereby contributing to energy efficiency. [Means for solving the problem]

[0007] The inventors discovered that the above problems could be solved by using a double-pack structure as a cushioning material, which includes a first pack and a second pack having an inner diameter larger than that of the first pack, with the first pack and the second pack at least partially joined and sealed at both ends, a gas filled in the first pack, and a liquid filled between the first pack and the second pack, and thus completed the present invention.

[0008] (1) A battery module comprising: a battery cell stack in which a plurality of battery cells are stacked; a pair of end plates provided at both ends of the battery cell stack in the stacking direction; and cushioning material arranged between the battery cells and / or between the battery cell stack and the end plates, wherein the cushioning material has a first pack and a second pack having an inner diameter larger than that of the first pack, a double pack structure in which at least a portion of the first pack and the second pack are joined to each other; a gas filled in the internal space of the first pack; and a liquid filled in the space between the first pack and the second pack.

[0009] In the battery module (1), even if the pressure applied to the cushioning material from the battery cells increases or decreases partially, the liquid filling the space between the first and second packs makes the internal pressure of the cushioning material uniform, so the pressure applied to the battery cells from the cushioning material is uniform. Furthermore, since the first pack is filled with gas, the insulation properties of the cushioning material are enhanced. Furthermore, since the first pack and the second pack are joined together, the position of the first pack is stabilized, so the insulation properties of the cushioning material are stable. Furthermore, the cushioning material has a double-pack structure with the first pack and the second pack, which has a relatively simple configuration and is easy to miniaturize.

[0010] (2) The battery module described in (1), wherein the first pack and the second pack of the double pack structure are formed from a single sheet that is wound twice.

[0011] The battery module (2) has a simpler structure and can be easily miniaturized because the first and second packs of cushioning material are formed from a single sheet.

[0012] (3) The battery module according to (1) or (2), wherein the cushioning material includes a ventilation pipe connected to the internal space of the first pack.

[0013] The battery module (3) can adjust the internal pressure of the cushioning material by introducing gas into the internal space of the first pack through the ventilation pipe and then exhausting the gas to the outside, which allows the pressure applied from the cushioning material to the battery cells to be more constant.

[0014] (4) The battery module according to any one of (1) to (3), wherein the cushioning material includes a liquid supply pipe and a liquid drain pipe connected to the space between the first pack and the second pack.

[0015] The battery module (4) can adjust the internal pressure of the cushioning material by introducing liquid into the space between the first and second packs through the liquid supply pipe and discharging the liquid through the liquid drain pipe. This allows for more constant pressure to be applied from the cushioning material to the battery cells. In addition, the temperature of the cushioning material can be adjusted by continuously flowing temperature-controlled liquid into the space between the first and second packs through the liquid supply pipe and the liquid drain pipe. This further improves the insulating properties of the cushioning material. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a battery module that uses a cushioning material that can apply uniform pressure to battery cells, has high thermal insulation properties, and is easily miniaturized. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of a battery module according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] 1 is a cross-sectional view of a battery cell that can be used in a battery module according to an embodiment of the present invention. [Figure 4] FIG. 3 is an enlarged cross-sectional view of the cushioning material shown in FIG. 2. [Figure 5]FIG. 4 is a cross-sectional view showing a first modified example of a battery module according to an embodiment of the present invention. [Figure 6] FIG. 6 is a plan view of a cushioning material used in the battery module of FIG. 5. [Figure 7] FIG. 10 is an enlarged cross-sectional view showing a cushion material used in a second modified example of a battery module according to an embodiment of the present invention. [Figure 8] FIG. 8 is a plan view of the cushioning material of FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0018] 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.

[0019] Fig. 1 is a cross-sectional view of a battery module according to one embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. Fig. 3 is a cross-sectional view of a battery cell that can be used in a battery module according to one embodiment of the present invention. Fig. 4 is an enlarged cross-sectional view of the cushioning material shown in Fig. 2.

[0020] As shown in FIGS. 1 and 2, the battery module 1 includes a battery cell stack 100 in which a plurality of battery cells 10 are stacked, a pair of end plates 20 provided at both ends of the battery cell stack in the stacking direction (Z direction in FIG. 1), and cushioning materials 30 arranged between the battery cells 10 and between the battery cell stack 100 and the end plates 20. The battery cell stack 100, the end plates 20, and the cushioning materials 30 are housed in a module case 40. The module case 40 has a positive terminal 51 and a negative terminal 52. The positive terminal 51 and the negative terminal 52 are arranged in opposing positions in one direction (X direction in FIG. 1). The positive terminal 51 is connected to a positive lead wire 11a of the battery cell 10. The negative terminal 52 is connected to a negative lead wire 14a of the battery cell 10.

[0021] The battery cell 10 is a battery that uses lithium ions as a charge transfer medium. As shown in FIG. 3 , 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 with charge and discharge. Therefore, the pressure applied by the battery cell 10 to the cushioning material 30 changes with charge and discharge. The stacking direction of the electrode stack 18 is the same as the stacking direction of the battery cell stack 100. That is, the multiple battery cells 10 of the battery module 1 are stacked along the stacking direction of the electrode stack 18. Note that, in the battery cell 10 shown in FIG. 4, one electrode stack 18 is housed in the exterior body 19, but multiple electrode stacks 18 may be housed in the exterior body 19.

[0022] 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.

[0023] 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 Mn q 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).

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] The solid electrolyte layer 17 contains at least one 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.

[0030] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiI, etc. The sulfide solid electrolyte may have an argyrodite-type crystal structure.

[0031] 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 Ti1.5 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).

[0032] 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.

[0033] The end plates 20 have the effect of restraining the battery cell stack 100 in the stacking direction. The restraining force of the end plates 20 can adjust the surface pressure applied to the battery cell stack by the cushion material 30. There are no particular restrictions on the material of the end plates 20, and various materials used for end plates for battery modules can be used.

[0034] The cushion material 30 has the effect of uniforming the surface pressure applied to the battery cells 10. The surface pressure applied to the battery cells 10 is, for example, 0.8 MPa or more.

[0035] As shown in FIG. 4 , the cushioning material 30 includes a double-pack structure 33 having a first pack 31 and a second pack 32 having an inner diameter larger than that of the first pack 31. The first pack 31 and the second pack 32 are joined to each other by a seal 34. The seal 34 may be formed by, for example, heat sealing or adhesive. A first space 35 inside the first pack 31 is filled with a gas. A second space 36 between the first pack 31 and the second pack 32 is filled with a liquid. The seal 34 is provided on the surface that contacts the battery cell 10. Therefore, the first space 35 is located below the cushioning material 30.

[0036] The double pack structure 33 is formed from a single sheet wound twice. The double pack structure 33 can be formed by winding a portion of the single sheet once to form a first tubular portion, then winding the remaining portion of the sheet around the outer periphery of the first tubular portion with a gap to form a second tubular portion, joining the first and second tubular portions, and then sealing the open ends of both the first and second tubular portions to form the first pack 31 and the second pack 32. A laminate film, for example, can be used as the sheet for forming the double pack structure 33. By forming the double pack structure 33 from a single laminate film, the first and second tubular portions can be joined by a single heat seal. This facilitates manufacturing.

[0037] The area ratio between the first space 35 and the second space 36 in a cross section perpendicular to the axial direction of the cushion material 30 may be set in consideration of the heat insulation and thermal conductivity of the cushion material 30. From the viewpoint of heat insulation, the ratio of the cross-sectional area of ​​the first space 35 to the total cross-sectional area of ​​the cushion material 30 is preferably within a range of, for example, 20 to 50%, and from the viewpoint of thermal conductivity, it is preferably within a range of, for example, 50 to 80%. The gas filled in the first space may be, for example, nitrogen. The liquid filled in the second space 36 may be, for example, mineral-based hydraulic oil, phosphate ester-based hydraulic oil, water, or a glycol-based solvent.

[0038] The module case 40 houses the battery cell stack 100 and the end plates 20. There are no particular limitations on the material of the module case 40, and various materials used for cases for battery modules can be used. The material of the positive electrode terminal 51 may be the same as the material of the positive electrode lead wire 11a, or may be different from the material of the positive electrode lead wire 11a. The material of the negative electrode terminal 52 may be the same as the material of the negative electrode lead wire 14a, or may be different from the material of the negative electrode lead wire 14a.

[0039] In the battery module 1 of this embodiment configured as described above, even if the volume of the battery cells 10 increases due to charging, causing a partial increase in the pressure applied from the battery cells 10 to the cushion material 30, or if the volume of the battery cells 10 decreases due to discharging, causing a partial decrease in the pressure applied from the battery cells 10 to the cushion material 30, the liquid filling the second space 36 between the first pack 31 and the second pack 32 makes the internal pressure of the cushion material 30 uniform. This allows the pressure applied from the cushion material 30 to be uniform. Furthermore, because the first space 35 inside the first pack 31 is filled with gas, the insulation properties of the cushion material 30 are enhanced. Furthermore, because the first pack 31 and the second pack 32 are joined by the seal portion 34, the position of the first pack 31 is stabilized, thereby stabilizing the insulation properties of the cushion material 30. Furthermore, the cushion material 30 is composed of a double-pack structure 33 including the first pack 31 and the second pack 32, which has a relatively simple configuration and is easy to miniaturize. In particular, since the first pack 31 and the second pack 32 of the cushioning material 30 are formed from a single sheet that is wound twice, the structure is simpler and it is easy to make the pack smaller.

[0040] Fig. 5 is a cross-sectional view showing a first modified example of a battery module according to one embodiment of the present invention Fig. 6 is a plan view of a cushioning material used in the battery module of Fig. 5.

[0041] 5 and 6, the battery module 2 of the first modified example has a ventilation pipe 37 connected to the first space 35 of the cushion material 30, and a liquid supply pipe 38 and a liquid drain pipe 39 connected to the second space 36, and other than that, the configuration is the same as that of the above-described battery module 1. Therefore, the same components as those of the above-described battery module 1 are denoted by the same reference numerals, and their description will be omitted.

[0042] The vent pipe 37 functions as an inlet and outlet for gas in the first space 35. For example, when the volume of the battery cell 10 increases due to charging, and the pressure applied from the battery cell 10 to the cushion material 30 increases partially, causing the internal pressure of the cushion material 30 to rise, the internal pressure of the cushion material 30 can be reduced by venting the gas in the first space 35 to the outside via the vent pipe 37. Furthermore, when the volume of the battery cell 10 decreases due to discharging, and the pressure applied from the battery cell 10 to the cushion material 30 decreases partially, the internal pressure of the cushion material 30 can be increased by introducing gas from the outside into the first space 35 via the vent pipe 37. Furthermore, regardless of whether charging or discharging, the pressure applied from the cushion material 30 to the battery cell 10 can be adjusted by introducing gas into the first space 35 or venting gas from the first space 35 via the vent pipe 37.

[0043] The liquid supply pipe 38 functions as an inlet for liquid in the second space 36, and the liquid drain pipe 39 functions as an outlet for liquid in the second space 36. For example, when the volume of the battery cell 10 decreases due to discharging and the pressure applied from the battery cell 10 to the cushion material 30 decreases partially, the internal pressure of the cushion material 30 can be increased by introducing liquid from the outside into the second space 36 via the liquid supply pipe 38. Furthermore, when the volume of the battery cell 10 increases due to charging and the pressure applied from the battery cell 10 to the cushion material 30 increases partially, causing the internal pressure of the cushion material 30 to increase, the internal pressure of the cushion material 30 can be reduced by discharging the liquid in the second space 36 to the outside via the liquid drain pipe 39. Furthermore, regardless of whether charging or discharging, the pressure applied to the battery cell 10 can also be adjusted by adjusting the internal pressure in the first space 35 via the cushion material 30. Furthermore, regardless of whether charging or discharging, the pressure applied from the cushion material 30 to the battery cells 10 can be adjusted by introducing liquid into the second space 36 through the liquid supply pipe 38 and discharging the liquid through the liquid drain pipe 39. Also, by supplying temperature-adjusted liquid to the second space 36 through the liquid supply pipe 38 and discharging the liquid to the outside through the liquid drain pipe 39, the internal temperature of the cushion material 30 can be adjusted.

[0044] The battery module 2 of the first modification has the same effect as the battery module 1, because the cushion material 30 includes a double-pack structure 33 having a first pack 31 and a second pack 32, a gas filled in the first space 35, and a liquid filled in the second space 36, similar to the battery module 1. Furthermore, the battery module 2 of the first modification can adjust the internal pressure of the cushion material 30 by introducing or discharging gas into the first space 35 through the ventilation pipe 37, thereby making it possible to keep constant the pressure applied from the cushion material 30 to the battery cells 10. Furthermore, the battery module 2 of the first modification can adjust the internal pressure of the cushion material 30 by introducing liquid into the second space 36 through the liquid supply pipe 38 or discharging the liquid through the liquid drain pipe 39, thereby making it possible to make more constant the pressure applied from the cushion material 30 to the battery cells 10. Furthermore, by continuously flowing temperature-adjusted liquid into the second space 36 via the liquid supply pipe 38 and the liquid drain pipe 39, the temperature of the cushion material 30 can be adjusted, thereby further improving the insulating properties of the cushion material 30.

[0045] Fig. 7 is an enlarged cross-sectional view showing a cushion material used in a second modified example of a battery module according to one embodiment of the present invention, and Fig. 8 is a plan view of the cushion material of Fig. 7.

[0046] 7 and 8, the cushion material 130 used in the second modified example has a seal portion 34 provided at the center of the surface on the side that does not contact the battery cell 10, and has a ventilation pipe 37 connected to the first space 35, and a liquid supply pipe 38 and a liquid drain pipe 39 connected to the second space 36. Other than these, the cushion material 130 has the same configuration as the above-described battery module 1. For this reason, the same reference numerals are used for the configurations common to the above-described battery module 1, and their description will be omitted.

[0047] In the cushion material 130, the seal portion 34 is provided in the center of the surface that does not contact the battery cell 10, so the first space 35 is located in the center of the cushion material 130, and the second spaces 36 are located above and below the first space 35 so as to sandwich the first space 35. As a result, in the cushion material 130, the second spaces 36 are located on both sides of the cushion material 130 that contact the battery cell 10.

[0048] The battery module of Modification 2 using the cushion material 130 has the same effect as the battery module 1 because, like the battery module 1, the cushion material 130 includes a double-pack structure 33 having a first pack 31 and a second pack 32, a gas filled in a first space 35, and a liquid filled in a second space 36. Furthermore, because the cushion material 130 includes a vent pipe 37, a liquid supply pipe 38, and a liquid drain pipe 39, the battery module has the same effect as the battery module 2 of Modification 1. Furthermore, because the second space 36 of the cushion material 130 is located on both sides of the side that contacts the battery cells 10, the internal pressure of the cushion material 130 tends to be uniform even if the pressure applied from the battery cells 10 to the cushion material 130 increases or decreases partially. Therefore, the pressure applied from the cushion material 130 to the battery cells 10 is uniform.

[0049] Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be modified as appropriate.

[0050] 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).

[0051] In the above embodiment, the cushion materials 30, 130 are disposed both between the battery cells 10 and between the battery cells 10 and the end plate 20, but the positions of the cushion materials 30, 130 are not limited to this. The cushion materials 30, 130 may be disposed at least either between the battery cells 10 and between the battery cell 10 and the end plate 20. [Explanation of symbols]

[0052] 1, 2 Battery Module 10 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 20 End Plate 30 Cushioning material 31 1st Pack 32 2nd Pack 33 Double Pack Structure 34 Seal part 35 1st space 36 Second space 37 Ventilation pipe 38 Liquid supply pipe 39 Drainage tube 40 Module Case 51 Positive terminal 52 Negative terminal

Claims

1. a battery cell stack in which a plurality of battery cells are stacked; a pair of end plates provided at both ends of the battery cell stack in a stacking direction; a cushioning material disposed between at least one of the battery cells and the battery cell stack and the end plate, The cushioning material has a first pack and a second pack having an inner diameter larger than that of the first pack, and a double pack structure in which at least a portion of the first pack and the second pack are joined to each other; a gas filled in the internal space of the first pack; and a liquid filled in the space between the first pack and the second pack.

2. 2. The battery module of claim 1, wherein the first pack and the second pack of the dual-pack structure are formed from a single sheet that is wound twice.

3. The battery module according to claim 1 or 2, wherein the cushioning material includes a ventilation pipe connected to an internal space of the first pack.

4. 3. The battery module according to claim 1, wherein the cushioning material includes a liquid supply pipe and a liquid drain pipe connected to a space between the first pack and the second pack.

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