Electric power storage module

Abstract

This electric power storage module is provided with: an electrode laminate in which electrodes are laminated in a first direction; a sealing body that is provided to the electrode laminate in a manner so as to surround the electrode laminate when viewed in the first direction; an exterior pack that accommodates the electrode laminate and the sealing body; and a cover member that is interposed between the exterior pack and a side surface of the sealing body extending in the first direction. The linear expansion coefficient of the cover member is smaller than the linear expansion coefficient of the sealing body.

Description

Energy storage module

[0001] The present disclosure relates to an energy storage module.

[0002] Patent Document 1 discloses an electric storage device. The electric storage device includes an electrode stack formed by stacking a plurality of bipolar electrodes, and an exterior body that seals the electrode stack under reduced pressure. The electrode stack includes a resin sealing member.

[0003] Japanese Patent Application Laid-Open No. 2019-87397

[0004] When a bipolar battery having a resin sealing member (sealing body) is covered with an exterior pack, the sealing member and the exterior pack may expand and contract in response to temperature changes. Because the resin sealing member expands significantly, the sealing member may come into contact with the exterior pack, potentially damaging the exterior pack.

[0005] The present disclosure provides an electricity storage module that suppresses damage to an exterior pack caused by expansion of a sealing body due to temperature changes.

[0006] An energy storage module according to one aspect of the present disclosure includes an electrode stack in which a plurality of electrodes, each including a current collector, are stacked in a first direction, a sealing body provided on the electrode stack so as to surround the electrode stack when viewed from the first direction and configured to seal a plurality of internal spaces formed between each of the electrodes adjacent in the first direction, an exterior pack accommodating the electrode stack and the sealing body, and a cover member interposed between a side surface of the sealing body extending in the first direction and the exterior pack, wherein the linear expansion coefficient of the cover member is smaller than the linear expansion coefficient of the sealing body.

[0007] In the above-described energy storage module, a cover member having a linear expansion coefficient smaller than that of the sealing body is disposed between the sealing body and the exterior pack, thereby reducing the influence of the sealing body on the exterior pack. That is, because the linear expansion coefficient of the cover member is smaller than that of the sealing body, the difference in thermal expansion coefficient between the cover member and the exterior pack is smaller than the difference in thermal expansion coefficient between the sealing body and the exterior pack. Therefore, when a temperature change occurs in the energy storage module, the influence of the expansion of the cover member on the generation of stress in the exterior pack is relatively small. Therefore, damage to the exterior pack caused by the expansion of the sealing body due to a temperature change can be suppressed.

[0008] An example cover member may contain a resin material and a filler, and the filler may have a linear expansion coefficient lower than the linear expansion coefficient of the resin material.

[0009] In one example, the cover member may extend along a second direction intersecting the first direction, and the filler may be an inorganic material having a needle or fiber shape and may be oriented along the second direction within the cover member.

[0010] In one example, the coefficient of linear expansion of the outer pack may be lower than the coefficient of linear expansion of the cover member, and the coefficient of linear expansion of the cover member may have a value closer to the coefficient of linear expansion of the outer pack than to the coefficient of linear expansion of the sealing body.

[0011] The difference between the expansion coefficients of the cover member and the outer pack in one example is 2.5×10 －５ [1 / °C] or less.

[0012] According to the present disclosure, it is possible to provide an electricity storage module that suppresses damage to an exterior pack caused by expansion of a sealing body due to temperature changes.

[0013] FIG. 1 is a schematic exploded perspective view of an example energy storage module. FIG. 2 is a schematic cross-sectional view of an example energy storage module. FIG. 3 is a schematic view showing one side of a module main body constituting an example energy storage module. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. FIG. 5 is a perspective view showing an example cover member. FIG. 6 is a plan view for explaining an example cover member. FIG. 7 is a partially enlarged view of FIG. 6.

[0014] An embodiment will be described below with reference to the drawings. In the description of the drawings, identical or equivalent elements are denoted by the same reference numerals, and redundant description may be omitted. In the description, a Cartesian coordinate system defined by the X-axis, Y-axis, and Z-axis shown in the drawings may be referenced.

[0015] FIG. 1 is a schematic exploded perspective view showing an energy storage module according to this embodiment. FIG. 2 is a schematic cross-sectional view of the energy storage module along the YZ plane. Note that FIG. 2 shows a simplified depiction of a module main body 1A included in the energy storage module 1. The energy storage module 1 is an energy storage module used in batteries for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The energy storage module 1 is a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. The energy storage module 1 may be an electric double layer capacitor or an all-solid-state battery. Here, a case is shown in which the energy storage module 1 is a lithium-ion secondary battery.

[0016] The energy storage module 1 includes a module main body 1A, a cover member 60A, a connector unit 30, and an exterior pack 90. ​​In FIG. 1 , the module main body 1A and the exterior pack 90 constituting the energy storage module 1 are shown disassembled from each other. In FIG. 2 , the module main body 1A is shown housed in the space inside the exterior pack 90. ​​The module main body 1A has a rectangular shape when viewed from the Z-axis direction (first direction) and has four outer surfaces 20s extending in the Z-axis direction. The outer surfaces 20s are composed of outer surfaces 20sA and 20sB facing each other in the Y-axis direction (third direction) and outer surfaces 20sC and 20sD facing each other in the X-axis direction (second direction). Note that both end surfaces in the Z-axis direction of the module main body 1A are composed of a positive terminal electrode 12 and a negative terminal electrode 13, as described below, and are used for extracting power.

[0017] The cover member 60A in one example is configured to include a first cover member 60, a second cover member 70, and a third cover member 80. The first cover member 60 and the second cover member 70 are arranged to cover the outer surface 20sA (first side surface) when viewed from the Y-axis direction (third direction). The third cover member 80 is arranged to cover the outer surface 20sB (second side surface) when viewed from the Y-axis direction. The connector unit 30 is arranged between the first cover member 60 and the second cover member 70 in the X-axis direction (second direction).

[0018] FIG. 3 is a schematic diagram showing one outer surface 20sA of the module main body 1A. FIG. 4 is a schematic cross-sectional view of an example module main body 1A. FIG. 4 shows a cross-section taken along line IV-IV in FIG. 3. The outer surface 20sA of the module main body 1A includes a region R1 in which an additional member 50 (described later) is provided, and regions R2 and R3 adjacent to this region R1. In the example shown in FIG. 3, region R2 is located on the negative side of region R1 in the X-axis direction, and region R3 is located on the positive side of region R1 in the X-axis direction. The additional member includes a liquid injection port 53A used when injecting an electrolyte solution into the module main body 1A. Therefore, in this specification, the outer surface 20sA may be referred to as a liquid injection port surface.

[0019] As shown in Fig. 4, the module main body 1A includes an electrode stack 10 and a sealing body 29 that surrounds the electrode stack 10 when viewed from the Z-axis direction. The electrode stack 10 includes multiple electrodes stacked along the Z-axis direction, which is the stacking direction of the electrodes and corresponds to the height direction of the energy storage module 1. The multiple electrodes include multiple bipolar electrodes 11, a positive terminal electrode 12, and a negative terminal electrode 13. Separators 14 are interposed between adjacent electrodes.

[0020] The bipolar electrode 11 includes a current collector 15, a positive electrode active material layer 16, and a negative electrode active material layer 17. The current collector 15 is rectangular and sheet-shaped when viewed from the Z-axis direction. The active material layers (positive electrode active material layer 16, negative electrode active material layer 17) are provided in the center of the current collector 15 when viewed from the Z-axis direction, and are not provided on the peripheral edge portion 15c of the current collector 15. The positive electrode active material layer 16 is provided on a first surface 15a of the current collector 15. The negative electrode active material layer 17 is provided on a second surface 15b of the current collector 15. The first surface 15a of the current collector 15 faces the other side in the Z-axis direction (the side where the negative electrode terminal electrode 13 is located in FIG. 4), and the second surface 15b of the current collector 15 faces the other side in the Z-axis direction (the side where the positive electrode terminal electrode 12 is located in FIG. 4). The plurality of bipolar electrodes 11 are stacked such that the positive electrode active material layer 16 of one bipolar electrode 11 and the negative electrode active material layer 17 of the other bipolar electrode 11 adjacent in the stacking direction face each other.

[0021] The positive terminal electrode 12 has a current collector 15 and a positive electrode active material layer 16 provided on a first surface 15a of the current collector 15. No active material layer is provided on a second surface 15b of the current collector 15 of the positive terminal electrode 12. The positive terminal electrode 12 is laminated on the bipolar electrode 11 at one end of the electrode laminate 10 in the Z-axis direction. The positive terminal electrode 12 is laminated on the bipolar electrode 11 so that the positive electrode active material layer 16 faces the negative electrode active material layer 17 of the bipolar electrode 11.

[0022] The negative electrode terminal electrode 13 has a current collector 15 and a negative electrode active material layer 17 provided on a second surface 15b of the current collector 15. No active material layer is provided on a first surface 15a of the current collector 15 of the negative electrode terminal electrode 13. The negative electrode terminal electrode 13 is laminated on the bipolar electrode 11 at the end of the electrode laminate 10 in the Z-axis direction, opposite the end on which the positive electrode terminal electrode 12 is provided. The negative electrode terminal electrode 13 is laminated on the bipolar electrode 11 so that its negative electrode active material layer 17 faces the positive electrode active material layer 16 of the bipolar electrode 11. Note that in this embodiment, the current collectors of the bipolar electrode 11, the positive electrode terminal electrode 12, and the negative electrode terminal electrode 13 are each referred to as a current collector 15 and are denoted by the same reference numeral; however, the current collectors of the bipolar electrode 11, the positive electrode terminal electrode 12, and the negative electrode terminal electrode 13 may be the same or different from one another.

[0023] The separators 14 are disposed between adjacent bipolar electrodes 11, between the positive terminal electrode 12 and the bipolar electrode 11, and between the negative terminal electrode 13 and the bipolar electrode 11. The separators 14 are interposed between the positive electrode active material layer 16 and the negative electrode active material layer 17, and separate the positive electrode active material layer 16 from the negative electrode active material layer 17. The separators 14 allow charge carriers such as lithium ions to pass through while preventing short circuits due to contact between adjacent electrodes.

[0024] The current collector 15 is a chemically inactive electrical conductor that allows current to continue to flow through the positive electrode active material layer 16 and the negative electrode active material layer 17 during discharge or charge of the lithium ion secondary battery. The material of the current collector 15 is, for example, a metal material, a conductive resin material, or a conductive inorganic material. Examples of conductive resin materials include resins obtained by adding a conductive filler to a conductive polymer material or a non-conductive polymer material as needed. The current collector 15 may have multiple layers. In this case, each layer of the current collector 15 may contain the above-mentioned metal material or conductive resin material.

[0025] A coating layer may be formed on the surface of the current collector 15. The coating layer may be formed by a known method such as plating or spray coating. The current collector 15 may be, for example, in the form of a plate, foil (e.g., metal foil), film, or mesh. Examples of metal foil include aluminum foil, copper foil, nickel foil, titanium foil, and stainless steel foil. The current collector 15 may be an alloy foil or clad foil of the above metals. When the current collector 15 is in the form of a foil, the thickness of the current collector 15 may be, for example, 1 μm to 100 μm. In this embodiment, the current collector 15 is a foil in which aluminum foil and copper foil are integrated together, or an aluminum foil.

[0026] The positive electrode active material layer 16 contains a positive electrode active material capable of absorbing and releasing charge carriers such as lithium ions. Examples of the positive electrode active material include lithium composite metal oxides having a layered rock salt structure, metal oxides having a spinel structure, and polyanion compounds. The positive electrode active material may be any material that can be used in lithium ion secondary batteries. The positive electrode active material layer 16 may contain a plurality of positive electrode active materials. In this embodiment, the positive electrode active material layer 16 contains an olivine-type lithium iron phosphate (LiFePO ) as a composite oxide. ４ )

[0027] The negative electrode active material layer 17 includes a negative electrode active material capable of absorbing and releasing charge carriers such as lithium ions. The negative electrode active material may be a simple substance, an alloy, or a compound. Examples of the negative electrode active material include Li, carbon, and metal compounds. The negative electrode active material may be an element or a compound thereof that can be alloyed with lithium. Examples of carbon include natural graphite, artificial graphite, hard carbon (non-graphitizable carbon), and soft carbon (easily graphitizable carbon). Examples of artificial graphite include highly oriented graphite and mesocarbon microbeads. Examples of elements that can be alloyed with lithium include silicon and tin. In this embodiment, the negative electrode active material layer 17 includes graphite as a carbon-based material.

[0028] Each of the positive electrode active material layer 16 and the negative electrode active material layer 17 (hereinafter sometimes simply referred to as "active material layer") may further contain, as necessary, a conductive additive to enhance electrical conductivity, a binder, an electrolyte (polymer matrix, ion-conductive polymer, electrolyte solution, etc.), an electrolyte supporting salt (lithium salt) to enhance ionic conductivity, etc. The conductive additive is added to enhance the conductivity of each electrode (bipolar electrode 11, positive terminal electrode 12, negative terminal electrode 13). Examples of the conductive additive include acetylene black, carbon black, and graphite.

[0029] Examples of binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber; thermoplastic resins such as polypropylene and polyethylene; imide resins such as polyimide and polyamideimide; alkoxysilyl group-containing resins; acrylic resins such as acrylic acid and methacrylic acid; styrene-butadiene rubber (SBR); carboxymethyl cellulose; alginates such as sodium alginate and ammonium alginate; water-soluble cellulose ester crosslinked bodies; and starch-acrylic acid graft polymers. These binders may be used alone or in combination. Examples of solvents that may be used include water and N-methyl-2-pyrrolidone (NMP).

[0030] The separator 14 may be, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains an electrolyte. Examples of materials for the separator 14 include polypropylene, polyethylene, polyolefin, and polyester. The separator 14 may have a single-layer structure or a multilayer structure. The multilayer structure may include, for example, a ceramic layer as an adhesive layer or a heat-resistant layer. The separator 14 may be impregnated with an electrolyte. The separator 14 may be composed of an electrolyte such as a polymer electrolyte or an inorganic electrolyte. Examples of the electrolyte impregnated in the separator 14 include a liquid electrolyte (electrolytic solution) containing a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent, and a polymer gel electrolyte containing an electrolyte retained in a polymer matrix.

[0031] When the separator 14 is impregnated with an electrolyte solution, the electrolyte salt is LiClO４ , LiAsF ６ , LiPF ６ , LiBF ４ , LiCF ３ SO ３ , LiN(FSO ２ ) ２ , LiN(CF ３ SO ２ ) ２ Known lithium salts such as those listed above may be used. Furthermore, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers may be used as the nonaqueous solvent. Two or more of these known solvent materials may be used in combination.

[0032] The seal 29 includes a seal main body 20 and an additional member 50. The seal main body 20 is formed in a frame shape around the periphery of the electrode stack 10 so as to surround the periphery of the electrode stack 10 when viewed in the Z-axis direction. The seal main body 20 can be joined to the first surface 15a and the second surface 15b of each current collector 15 at the peripheral portion 15c of each current collector 15. The seal main body 20 can form an internal space S between adjacent current collectors 15 in the Z-axis direction and seal each of the internal spaces S. In this embodiment, each internal space S contains an electrolyte (not shown). That is, the seal main body 20 cooperates with adjacent current collectors 15 in the Z-axis direction to define an internal space S in which the electrolyte is contained. The seal main body 20 can prevent the electrolyte contained in the internal space S from leaking out to the outside.

[0033] The seal body 20 can prevent air, moisture, and the like from entering and leaving between the outside of the electrode stack 10 and the internal space S. The seal body 20 can prevent, for example, gas generated in each electrode due to a charge / discharge reaction or the like from leaking to the outside of the module body 1A. The edge of the separator 14 is joined to the seal body 20. The seal body 20 includes an insulating material. Examples of materials for the seal body 20 include various resin materials such as polypropylene, polyethylene, polystyrene, ABS resin, acid-modified polypropylene, acid-modified polyethylene, and acrylonitrile-styrene resin.

[0034] An example of the seal main body 20 includes a plurality of seal materials 21, a pair of end seal materials 24, and a plurality of spacers 22. The seal materials 21, the end seal materials 24, and the spacers 22 may be frame-shaped members formed in a sheet shape. The seal main body 20 also has a welded end portion 23. The seal material 21 is frame-shaped when viewed from the Z-axis direction and is provided along the peripheral edge portion 15c of the current collector 15. The seal material 21 is provided so as to extend from the first surface 15a of the current collector 15, passing through the end face, to the second surface 15b, and covers the peripheral edge portion 15c. That is, on the first surface 15a and the second surface 15b of the current collector 15, the seal material 21 has an inner portion overlapping the current collector 15 and an outer portion located outside the edge of the current collector 15, as viewed from the Z direction. The outer portions of a pair of adjacent seal materials 21 sandwiching the current collector 15 are connected to each other. The seal material 21 can be welded to at least one of the first surface 15 a and the second surface 15 b of the current collector 15. In this embodiment, the seal material 21 is welded to both the first surface 15 a and the second surface 15 b of the current collector 15.

[0035] The end seal material 24 has a frame shape when viewed in the Z-axis direction and is provided along the peripheral edge 15c of the current collector 15 that constitutes the positive terminal electrode 12 and the negative terminal electrode 13. Therefore, the end seal material 24 is arranged to sandwich the plurality of seal materials 21 in the Z-axis direction. The end seal material 24 can be welded to at least one of the first surface 15a and the second surface 15b of the current collector 15. In this embodiment, the end seal material 24 is welded to both the first surface 15a and the second surface 15b of the current collector 15.

[0036] The spacer 22 has a frame shape when viewed from the Z-axis direction, and is arranged along the peripheral edge 15c of the current collector 15. The spacer 22 is arranged so as to be interposed between the seal materials 21 adjacent to each other in the Z-axis direction. The spacer 22 is also arranged so as to be interposed between the seal materials 21 and the end seal materials 24 adjacent to each other in the Z-axis direction. The spacer 22 can maintain the distance between the current collectors 15 adjacent to each other in the Z-axis direction. In other words, the spacer 22, the seal materials 21, and the end seal materials 24 define an internal space S between the adjacent current collectors 15.

[0037] The welded end portion 23 is formed by welding together and integrating the ends of the multiple seal materials 21, the pair of end seal materials 24, and the multiple spacers 22 on the opposite side to the internal space S. When viewed from the Z-axis direction, the welded end portion 23 has a frame shape that surrounds the electrode stack 10. The side of the welded end portion 23 on the opposite side to the internal space S extends along the Z-axis direction and forms the outer surface 20s of the seal main body 20. In other words, the seal main body 20 includes the outer surface 20s on the opposite side to the internal space S. The outer surface 20s may be formed as a flat surface.

[0038] The seal main body 20 has a plurality of communication holes 27 that communicate with each of the plurality of internal spaces S. As an example, the communication holes 27 are notched portions formed in the spacer 22, and are formed to penetrate the welded end portion 23. Each communication hole 27 has one opening in the internal space S and the other opening on the outer surface 20s of the seal main body 20. In the illustrated example, an opening is formed on the outer surface 20sA.

[0039] The additional member 50 is formed so as to overlap the region R1 of the outer surface 20sA in which the communication holes 27 are formed. The additional member 50 is molded into a predetermined shape to provide a liquid inlet portion 53A having a plurality of liquid inlets that respectively communicate with the plurality of communication holes 27. The additional member 50 is joined to the welded end portion 23. For example, the additional member 50 is integrally joined to the welded end portion 23 by injection molding. An example additional member 50 includes a main body portion 51, a first overhang portion 55, and a second overhang portion 57.

[0040] The main body portion 51 partially covers the outer surface 20sA. For example, the main body portion 51 covers the outer surface 20sA so as to include a region R1 in which a plurality of communication holes 27 are formed on the outer surface 20sA. As described above, the plurality of communication holes 27 are respectively connected to a plurality of internal spaces S. In the example shown in FIG. 3 , 30 communication holes 27 corresponding to the 30 internal spaces formed between the current collectors 15 are discretely arranged in the X-axis direction and the Z-axis direction. More specifically, the communication holes 27 corresponding to the internal spaces of the first to tenth layers, with the positive terminal electrode 12 as the base end, are arranged evenly spaced apart along the X-axis direction, and the communication holes 27 corresponding to the internal spaces of the eleventh to twentieth layers and the communication holes 27 corresponding to the internal spaces of the twenty-first to thirtieth layers are arranged sequentially below the internal spaces of the first to tenth layers in the Z-axis direction. The main body 51 extends in a rectangular shape along the X-axis direction and the Z-axis direction to cover the region R1 in which the 30 communication holes 27 are formed.

[0041] The main body 51 is formed in the shape of a rectangular plate having a predetermined thickness in the Y-axis direction. The main body 51 has openings 52 at positions corresponding to the communication holes 27. The main body 51 also has protruding frame portions 53 that protrude from the outer surface 20sA in the Y-axis direction intersecting (orthogonal to) the outer surface 20sA. The protruding frame portions 53 surround each opening 52 as viewed from the Y-axis direction and function as partition walls that separate the openings 52. In the example of FIG. 3 , ten protruding frame portions 53, each having three spaces formed therein to separate three openings 52 lined up vertically, are arranged in the X-axis direction.

[0042] As an example, the protruding frame portions 53 are used when injecting an electrolyte solution into each of the internal spaces S. For example, when injecting the electrolyte solution, a nozzle of a liquid injection device is brought into close contact with the top surface of the protruding frame portions 53, and the electrolyte solution is introduced from the nozzle into the spaces of each of the protruding frame portions 53. This makes it possible to inject the electrolyte solution into the internal spaces S through the openings 52 and the communication holes 27. After the electrolyte solution is injected, a laminate sheet 54 for sealing the protruding frame portions 53 may be provided on the protruding frame portions 53. The laminate sheet 54 may be, for example, a sheet in which a metal layer such as aluminum is coated with a resin layer. The laminate sheet 54 may be fused to the top surface of the protruding frame portions 53, for example.

[0043] In one example, the main body 51 includes a terminal 58 for voltage detection. The terminal 58 is formed in the main body 51 at a position offset toward the positive side of the X-axis direction from the liquid inlet 53A formed by the multiple protruding frame portions 53. For example, the terminal 58 is provided adjacent to the protruding frame portion 53 formed at the end on the positive side of the X-axis direction, with the flat surface 51a interposed therebetween. In one example, the terminal 58 is provided at the end on the positive side of the X-axis direction of the main body 51. The terminal 58 provides multiple terminals 58a electrically connected to the multiple current collectors 15, respectively. One end of the terminal 58a is connected to the corresponding current collector 15, and the other end of the terminal 58a is exposed from the main body 51. The terminals 58a may be, for example, metal pins, as long as they are electrically connected to the current collectors 15. A connector unit 30 is fixed to the terminal 58 (see FIGS. 6 and 7 ). The connector unit 30 as an example includes a housing 31 having a plurality of contacts connected to a plurality of terminals 58 a, and an FPC connector 33 for connecting the plurality of contacts to a flexible printed circuit (FPC) 32 .

[0044] The first overhang portion 55 and the second overhang portion 57 are formed to connect to both end edges of the main body portion 51 in the Z-axis direction. The first overhang portion 55 partially covers one edge of the welded end portion 23 in the Z-axis direction (the positive side in the Z-axis direction). For example, the first overhang portion 55 partially covers the end seal material 24 joined to the positive terminal electrode 12. In the illustrated example, the edge 55a of the first overhang portion 55 extends from the edge of the welded end portion 23 to a position outside the inner edge 22a of the spacer 22 and the inner edge 21a of the seal material 21 as viewed in the Z-axis direction, but this is not limited thereto. The first overhang portion 55 may be formed in a rectangular plate shape having the same length as the main body portion 51 in the X-axis direction.

[0045] The second overhang portion 57 partially covers the other edge of the welded end portion 23 in the Z-axis direction (negative side in the Z-axis direction). For example, the second overhang portion 57 partially covers the end seal material 24 joined to the negative terminal electrode 13. In the illustrated example, the edge 57a of the second overhang portion 57 extends from the edge of the welded end portion 23 to a position outside the inner edge 22a of the spacer 22 and the inner edge 21a of the seal material 21 when viewed in the Z-axis direction, but this is not limited to this. The second overhang portion 57 may be formed in a rectangular plate shape having the same length in the X-axis direction as the main body portion 51.

[0046] Referring again to FIGS. 1 and 2 , the exterior pack 90 houses the module main body 1A, the cover member 60A, and the connector unit 30. An example of the exterior pack 90 includes a conductive member 91 and an exterior film 93. The conductive member 91 is composed of a first conductive member 91A and a second conductive member 91B, each of which has a rectangular sheet shape. The first conductive member 91A abuts against the second surface 15b of the current collector 15 of the positive terminal electrode 12 and is electrically connected to the positive terminal electrode 12. The second conductive member 91B abuts against the first surface 15a of the current collector 15 of the negative terminal electrode 13 and is electrically connected to the negative terminal electrode 13. The conductive member 91 may be, for example, a metal foil, such as aluminum foil. The planar size of the conductive member 91 may be equal to or smaller than that of the current collector 15.

[0047] The exterior film 93 is configured to surround the outer periphery of the contents (here, the module main body 1A, the cover member 60A, and the connector unit 30) when viewed from the Z-axis direction. For example, the exterior film 93 may cover at least the sealing body 29 of the module main body 1A. In the illustrated example, the exterior film 93 is configured with a first exterior film 93A connected to the first conductive member 91A and a second exterior film 93B connected to the second conductive member 91B. The exterior film 93 has a rectangular frame shape. For example, the exterior film 93 may be formed by welding four strip-shaped sheets 94 along each of the four sides of the rectangle. In the illustrated example, the first exterior film 93A is deformed so that its outer edge is located closer to the second exterior film 93B than its inner edge. The second exterior film 93B is deformed so that its outer edge is located closer to the first exterior film 93A than its inner edge.

[0048] The inner edge of the rectangular frame-shaped exterior film 93 is located inside the periphery of the conductive member 91 when viewed from the Z-axis direction. The inner edge of the exterior film 93 and the periphery of the conductive member 91 are joined together in an overlapping state. In one example, the inner edge of the exterior film 93 and the periphery of the conductive member 91 may be joined together by a resin material 95. The resin material 95 may be a rectangular frame-shaped sealing resin formed in a sheet. For example, the inner edge of the rectangular frame-shaped resin material 95 may be located inside the inner edge of the exterior film 93, and the outer edge of the resin material 95 may coincide with the periphery of the conductive member 91.

[0049] The outer edge of the exterior film 93 is located outside the periphery of the contents when viewed from the Z-axis direction. The outer edges of the first exterior film 93A and the second exterior film 93B are joined to each other. As an example, the outer edges of the first exterior film 93A and the second exterior film 93B may be welded to each other. The periphery of the conductive member 91 and the inner edge of the exterior film 93 are sealed to each other, and the outer edges of the first exterior film 93A and the second exterior film 93B are sealed to each other, thereby forming a sealed space inside the exterior pack 90. ​​After the module main body 1A and the like are housed in the exterior pack 90, the interior of the exterior pack 90 may be sealed in a depressurized state. In this case, the exterior pack 90 is pressed by atmospheric pressure, causing the pair of conductive members 91 to adhere closely to the positive terminal electrode 12 and the negative terminal electrode 13, respectively. When the first exterior film 93A and the second exterior film 93B are joined together, the flexible substrate 32 is exposed to the outside of the exterior pack 90 from the joining surface between the first exterior film 93A and the second exterior film 93B.

[0050] The exterior film 93 may be, for example, a laminate film including a metal layer, that is, the exterior film 93 may be a sheet-like member in which both sides of a metal layer 93a such as aluminum are covered with resin layers 93b and 93c.

[0051] The cover member 60A is disposed between the outer surface 20s of the module main body 1A and the exterior film 93, and is housed in the exterior pack 90 together with the module main body 1A and the connector unit 30. That is, the cover member 60A is interposed between the outer surface 20s and the exterior film 93. In the exemplary energy storage module 1, the cover member 60A is composed of a first cover member 60 and a second cover member 70 disposed between the outer surface 20sA of the module main body 1A and the exterior film 93, and a third cover member 80 disposed between the outer surface 20sB of the module main body 1A and the exterior film 93. The first cover member 60 is disposed on the outer surface 20sA on the negative side of the terminal portion 58 in the X-axis direction. The second cover member 70 is disposed on the outer surface 20sA so as to cover the positive side of the terminal portion 58 in the X-axis direction.

[0052] Fig. 5 is a perspective view showing the first cover member 60 and the second cover member 70. The first cover member 60 and the second cover member 70 in Fig. 5 are shown in a positional relationship when housed in an exterior pack 90. ​​Fig. 6 is a plan view for explaining the relationship between the first cover member 60, the second cover member 70, and the third cover member 80 and the module main body 1A, showing a state in which the exterior pack 90 has been removed. Fig. 7 is a partial enlarged view of Fig. 6.

[0053] The first cover member 60 includes a first wall portion 61 and a second wall portion 62 that face each other in the Z-axis direction, and a third wall portion 63 that extends in the XZ plane to connect the first wall portion 61 and the second wall portion 62. The first cover member 60 also includes a fourth wall portion 64 and a fifth wall portion 65 that face each other in the X-axis direction and extend in the YZ plane to connect the first wall portion 61, the second wall portion 62, and the third wall portion 63.

[0054] The connection portion 60a between the first wall portion 61 and the third wall portion 63, the connection portion 60b between the second wall portion 62 and the third wall portion 63, the connection portion 60c between the first wall portion 61 and the fourth wall portion 64, the connection portion 60d between the second wall portion 62 and the fifth wall portion 65, and the connection portion 60e between the third wall portion 63 and the fourth wall portion 64 are formed with chamfered corners. The chamfered shape may be, for example, a rounded chamfer. In other words, the corners formed by the connections between the wall portions may be curved in an arc shape when viewed from any of the X-axis direction, the Y-axis direction, and the Z-axis direction.

[0055] One or more reinforcing ribs 67 are provided within the hollow interior of the first cover member 60. The ribs 67 are plate-shaped and extend along the YZ plane, connecting the first wall portion 61, the second wall portion 62, and the third wall portion 63 to one another. The multiple ribs 67 may be arranged at equal intervals in the X-axis direction. For example, the interval between adjacent ribs 67 is greater than the interval between the first wall portion 61 and the second wall portion 62 and less than twice the interval between the first wall portion 61 and the second wall portion 62. The end faces of the first wall portion 61, the second wall portion 62, the fourth wall portion 64, the fifth wall portion 65, and the ribs 67 facing away from the third wall portion 63 form a wall surface 69 facing the third wall portion 63.

[0056] The first wall portion 61 and the second wall portion 62 each have a first region 60R1 connected to the fourth wall portion 64, a second region 60R2 connected to the fifth wall portion 65, and a third region 60R3 sandwiched between the first region 60R1 and the second region 60R2. The first region 60R1 and the second region 60R2 have the same length in the Y-axis direction. The third region 60R3 has a shorter length in the Y-axis direction than the first region 60R1 and the second region 60R2. In the illustrated example, the connection positions of the first wall portion 61 and the second wall portion 62 with the third wall portion 63 are constant in the Y-axis direction. Therefore, the position of the wall surface 69 in the third region 60R3 is closer to the third wall portion 63 in the Y-axis direction than the positions of the wall surfaces 69 in the first region 60R1 and the second region 60R2.

[0057] The first region 60R1 faces the region R2 of the outer side surface 20sA. The second region 60R2 faces the flat surface 51a of the additional member 50 provided on the outer side surface 20sA. The third region 60R3 faces the liquid inlet port 53A of the additional member 50 provided on the outer side surface 20sA. In the first region 60R1, the wall surface 69 of the first cover member 60 forms a contact surface 69a that contacts the region R2 of the outer side surface 20sA. In the second region 60R2, the wall surface 69 of the first cover member 60 forms a contact surface 69b that contacts the flat surface 51a of the additional member 50. In the third region 60R3, the wall surface 69 of the first cover member 60 forms a non-contact surface 69c that is spaced apart from the liquid inlet port 53A of the additional member 50. The non-contact surface 69c is recessed in a direction away from the outer surface 20sA relative to the contact surfaces 69a and 69b when viewed in the Z-axis direction (i.e., in the opposite direction from the outer surface 20sA in the Y-axis direction). In the third region 60R3, a gap is formed between the wall surface 69 of the first cover member 60 and the additional member 50.

[0058] The second cover member 70 includes a first wall portion 71 and a second wall portion 72 that face each other in the Z-axis direction, and a third wall portion 73 that extends in the XZ plane to connect the first wall portion 71 and the second wall portion 72. The second cover member 70 also includes a fourth wall portion 74 and a fifth wall portion 75 that face each other in the X-axis direction and extend in the YZ plane to connect the first wall portion 71, the second wall portion 72, and the third wall portion 73.

[0059] The connection portion 70a between the first wall portion 71 and the third wall portion 73, the connection portion 70b between the second wall portion 72 and the third wall portion 73, the connection portion 70c between the third wall portion 73 and the fifth wall portion 75, the connection portion 70d between the second wall portion 72 and the fifth wall portion 75, and the connection portion 70e between the first wall portion 71 and the fifth wall portion 75 are formed with chamfered corners. The chamfered shape may be, for example, a rounded chamfer. In other words, the corners formed by the connections between the wall portions may be curved in an arc shape when viewed from any of the X-axis direction, the Y-axis direction, and the Z-axis direction.

[0060] One or more reinforcing ribs 77 are provided within the hollow interior of the second cover member 70. The ribs 77 are plate-shaped and extend along the YZ plane, connecting the first wall portion 71, the second wall portion 72, and the third wall portion 73 to one another. The multiple ribs 77 may be arranged at equal intervals in the X-axis direction. For example, the interval between adjacent ribs 77 is greater than the interval between the first wall portion 71 and the second wall portion 72 and less than twice the interval between the first wall portion 71 and the second wall portion 72. The end faces of the first wall portion 71, the second wall portion 72, the fourth wall portion 74, the fifth wall portion 75, and the ribs 77 facing away from the third wall portion 73 form a wall surface 79 facing the third wall portion 73.

[0061] The illustrated second cover member 70 has a notched space 70S for accommodating an FPC connector. That is, in the second cover member 70, corners 70k of the first wall portion 71 and the second wall portion 72 that connect to the third wall portion 73 and the fourth wall portion 74 are formed in a recessed corner shape. As a result, the fourth wall portion 74 is divided into two at the center in the Y-axis direction. Furthermore, the third wall portion 73 is divided into two in the X-axis direction at a position close to the fourth wall portion 74.

[0062] A wall surface 79 of the second cover member 70 faces region R3 of the outer surface 20sA and is in contact with the outer surface 20sA. In the illustrated example, a notch-shaped portion 78 is formed in the first wall portion 71 and the second wall portion 72 near the fourth wall portion 74 to avoid interference with the end of the additional member 50. For example, the notch-shaped portion 78 connects the wall surface 79 and the fourth wall portion 74 at an angle when viewed from the Z-axis direction, and is formed so that the wall surface 79 near the fourth wall portion 74 is spaced apart from the outer surface 20sA. In one example, when the additional member 50 is formed by injection molding, resin may protrude from the main body of the additional member 50 along the outer surface 20sA. In that case, the protruding resin portion can be accommodated in the space formed by the notch-shaped portion 78.

[0063] The third cover member 80 has the same basic structure as the first cover member 60 and the second cover member 70. That is, the third cover member 80 includes a first wall portion 81 and a second wall portion 82 that face each other in the Z-axis direction, a third wall portion 83 that extends in the X-Z plane to connect the first wall portion 81 and the second wall portion 82, and a fourth wall portion 84 and a fifth wall portion 85 that extend in the Y-Z plane to connect the first wall portion 81, the second wall portion 82, and the third wall portion 83 and face each other in the X-axis direction (see FIG. 1 ). In one example, the third cover member 80 has a substantially rectangular shape when viewed from the Z-axis direction, and an end face 89 facing the outer surface 20sB is flat. This end face 89 may be in contact with the outer surface 20sB over the entire area in the X-axis direction. Corners connecting the walls may be chamfered when viewed from any of the X-axis direction, the Y-axis direction, and the Z-axis direction. The third cover member 80 may be divided into multiple parts.

[0064] The first cover member 60, the second cover member 70, and the third cover member 80 may restrict movement of the module main body 1A in at least one of the X-axis direction and the Y-axis direction. The first cover member 60, the second cover member 70, and the third cover member 80 may be fixed to the module main body 1A. For example, a protrusion or a recess may be formed on the sealing body 29 of the module main body 1A, and the first cover member 60, the second cover member 70, and the third cover member 80 may be engaged with the protrusion or the recess. Furthermore, the first cover member 60, the second cover member 70, and the third cover member 80 may be fixed to the module main body 1A by adhesive or the like.

[0065] Next, the linear expansion coefficient of each component will be described. The linear expansion coefficient of the sealing body 29 made of resin is greater than the linear expansion coefficient of the electrode stack 10 including the current collector 15 made of metal foil or the like. In one example, the linear expansion coefficient of the sealing body 29 is 6 to 25×10 －５ [1 / °C], and the linear expansion coefficient of the electrode laminate 10 is 2.0 to 2.5 × 10 －５ [1 / °C]. Since the constituent ratio of the sealing body 29 in the module body 1A is small, the linear expansion coefficient of the module body 1A may be considered to be equivalent to the linear expansion coefficient of the electrode stack 10.

[0066] In one example, the length L1 of the module main body 1A along the X-axis direction may be approximately 700 mm to 1800 mm, the length L2 of the module main body 1A along the Y-axis direction may be approximately 900 mm to 2000 mm, the length L3 of the first cover member 60 and the second cover member 70 along the Y-axis direction may be approximately 5 mm to 100 mm, and the length L4 of the third cover member 80 along the Y-axis direction may be approximately 5 mm to 60 mm. The length of the third cover member 80 along the X-axis direction may be equal to the length L1 of the module main body 1A along the X-axis direction. Furthermore, the length from the fourth wall portion 64 of the first cover member 60 to the fifth wall portion 75 of the second cover member 70 may be equal to the length L1 of the module main body 1A along the X-axis direction. In other words, the positions of both end portions of the cover member 60A and both end portions of the module main body 1A in the X-axis direction at room temperature may be approximately the same. Furthermore, when the first cover member 60 and the second cover member 70 expand due to an increase in temperature, the connector unit 30 prevents them from expanding toward each other, and so they can expand away from each other (outward along the X-axis direction).

[0067] As described above, an example of the exterior film 93 is a laminate film. For example, the resin layers 93b and 93c constituting the exterior film 93 may be formed of the same resin as the sealing body 29. The exterior film 93 having a metal layer 93a such as aluminum as an intermediate layer has a linear expansion coefficient close to that of the metal layer 93a. In one example, the linear expansion coefficient of the exterior film 93 is 2 to 3×10 －５ In this embodiment, the linear expansion coefficient of the exterior film 93 and the linear expansion coefficient of the module main body 1A may be approximately the same.

[0068] The linear expansion coefficient of the cover member 60A is designed to be smaller than the linear expansion coefficient of the sealing body 29. In one example, the cover member 60A may have a linear expansion coefficient that causes a volume change that is small enough to prevent the exterior film 93 from being damaged when a temperature change of about 100°C occurs. For example, if the cover member 60A expands due to a temperature change, the expanded cover member 60A may press against the exterior film 93, causing stress to be generated in the exterior film 93. If the stress generated in the exterior film 93 exceeds the breaking strength of the exterior film 93, the exterior film 93 may be damaged. Therefore, the cover member 60A may have a linear expansion coefficient that prevents the stress generated in the exterior film 93 from exceeding the breaking strength of the exterior film 93.

[0069] The stress (σ) generated in the exterior film 93 is expressed as the product of the strain (ε) generated in the exterior film 93 and the Young's modulus (E) of the exterior film 93. That is, the following equation (1) holds: σ=Eε Equation (1)

[0070] Here, consider a model in which the third cover member 80 expanding in the longitudinal direction (X-axis direction) generates stress in the exterior film 93. When the exterior film 93 is sealed, the length of the third cover member 80 in the X-axis direction is substantially equal to the length of the exterior film 93 in the X-axis direction. Therefore, the strain (ε) generated in the exterior film 93 is expressed as the difference between the amount of expansion of the exterior film 93 and the amount of expansion of the third cover member 80. In other words, the strain (ε) is expressed as the product of the difference (αC - αF) between the linear expansion coefficient αC of the third cover member 80 and the linear expansion coefficient αF of the exterior film 93 and the temperature change T. In other words, the following equation (2) holds: ε = T (αC - αF) ... Equation (2)

[0071] In this case, the stress (σ) generated in the exterior film 93 is expressed as σ=ET(αC-αF) by referring to the above formulas (1) and (2). Therefore, the condition required for the linear expansion coefficient αC of the third cover member 80 so that the stress (σ) generated in the exterior film 93 does not exceed the breaking strength of the exterior film 93 is expressed by the following formula (3), where F is the breaking strength of the exterior film 93: αC≦(F / (ET))+αF Formula (3)

[0072] For example, the coefficient of linear expansion, Young's modulus, and breaking strength of the exterior film 93 are 2.5×10 －５ [1 / °C], 33000 [MPa], and 75 [MPa], the linear expansion coefficient of the third cover member 80 is approximately 5.0 × 10 －５ [1 / °C] or less. That is, the difference in the linear expansion coefficient between the third cover member 80 and the exterior film 93 may be 2.5×10 －５ [1 / °C] or less.

[0073] As an example, the cover member 60A may be formed from a mixed material of a resin as a main material and a filler (packing agent) that reduces the linear expansion coefficient. In other words, it is sufficient that the linear expansion coefficient of the cover member is lower than that of the sealing body. The resin as a main material of the cover member may be any resin material, and may be a thermoplastic resin such as a general-purpose plastic, a general-purpose engineering plastic, or a super engineering plastic, or a thermosetting resin. The resin may be polyphenylene sulfide. The resin may be polyamide, polypropylene, or the like. The resin may be a polymer alloy in which multiple polymers are mixed, such as modified polyphenylene ether. The resin may be a resin whose copolymer properties change depending on the ratio of monomers, such as acrylonitrile styrene resin. In one example, the linear expansion coefficient of the resin as a main material of the cover member 60A is 2.5 x 10 －５ It may be about [1 / °C].

[0074] The filler may be any material that reduces the linear expansion coefficient of the cover member 60A. The filler material may be a metal compound, an inorganic compound, or an organic compound. The shape of the filler is not particularly limited. For example, the filler may be spherical, needle-like, fibrous, or plate-like. When the filler has an oriented shape such as a needle or fiber shape, it may have an anisotropic shape extending in a direction intersecting the longitudinal direction. In the cover member 60A, the longitudinal direction of the filler may be oriented in the X-axis direction. The filler may be an inorganic material such as glass fiber, glass beads, carbon fiber, alumina powder, or silica. In one example, the filler may be mixed in a ratio of approximately 20 wt % to 60 wt % with respect to the main material. In one example, the linear expansion coefficient of the filler is 0.3×10 －５ [1 / °C]. In one example, the linear expansion coefficient of the cover member 60A is 2.3 to 5.0 × 10 －５ It may be about [1 / °C].

[0075] As described above, the example energy storage module 1 includes an electrode stack 10 in which a plurality of electrodes, each including a current collector 15, are stacked in the Z-axis direction, a sealing body 29 that is provided on the electrode stack 10 so as to surround the electrode stack 10 when viewed from the Z-axis direction and is configured to seal a plurality of internal spaces formed between each of the electrodes adjacent in the Z-axis direction, an exterior film 93 that houses the electrode stack 10 and the sealing body 29, and a cover member 60A that is interposed between the exterior film 93 and a side surface of the sealing body 29 that extends in the Z-axis direction. The linear expansion coefficient of the cover member 60A is smaller than the linear expansion coefficient of the sealing body 29.

[0076] In the above-described energy storage module, the cover member 60A, which has a linear expansion coefficient smaller than that of the sealing body 29, is disposed between the sealing body 29 and the exterior pack 90. ​​This reduces the influence of the sealing body 29 and the cover member 60A, which act as the contents contained therein, on the exterior pack 90. ​​That is, because the linear expansion coefficient of the cover member 60A is smaller than that of the sealing body 29, the difference in thermal expansion coefficient between the cover member 60A and the exterior pack 90 is smaller than the difference in thermal expansion coefficient between the sealing body 29 and the exterior pack 90. ​​Therefore, when a temperature change occurs in the energy storage module 1, the influence of the expansion of the cover member 60A on the generation of stress in the exterior pack 90 is relatively small. This makes it possible to suppress damage to the exterior pack caused by the expansion of the sealing body 29 due to a temperature change. That is, the thermal shock resistance of the energy storage module 1 is improved.

[0077] In one example, the cover member 60A may contain a resin material and a filler, and the filler may have a lower linear expansion coefficient than the resin material. This configuration allows the cover member 60A, which is primarily made of a resin material, to have a lower thermal expansion coefficient.

[0078] In one example, the cover member 60A may extend along the X-axis direction. The filler may be an inorganic material having a needle-like or fibrous shape, and may be oriented along the X-axis direction within the cover member 60A. In this configuration, the filler is oriented in the X-axis direction, which efficiently reduces the linear expansion coefficient in the X-axis direction. In this case, the mixing ratio of the filler to the main material can be reduced.

[0079] The difference between the expansion coefficients of the cover member and the outer pack in one example is 2.5×10 －５[1 / °C] or less. This configuration can reduce the difference between the amount of dimensional change of the cover member 60A and the amount of dimensional change of the exterior film 93 when a temperature change occurs. For example, even when a temperature change of about 100°C is expected (for example, when the temperature changes from -40°C to 60°C), damage to the exterior film 93 by the expanding cover member 60A is suppressed. Note that in this embodiment, the difference between the linear expansion coefficient of the cover member and the linear expansion coefficient of the energy storage module main body is also small, so that variations in the amount of dimensional change of the energy storage module main body and the cover member, which are major components arranged inside the exterior film, are suppressed.

[0080] Although examples of the embodiments of the present disclosure have been described above with reference to the drawings, the present disclosure is not limited to the above embodiments.

[0081] In the above embodiment, an example in which the expansion coefficient of the cover member 60A is smaller than the expansion coefficient of the sealing body 29 is shown, where the expansion coefficient of the cover member 60A is larger than the expansion coefficient of the outer casing film 93, but the expansion coefficient of the cover member 60A may also be smaller than the expansion coefficient of the outer casing film 93.

[0082] In one example, the linear expansion coefficient of the exterior pack 90 may be equal to or less than the linear expansion coefficient of the cover member 60A. The linear expansion coefficient of the cover member 60A may be closer to the linear expansion coefficient of the exterior pack 90 than to the linear expansion coefficient of the sealing body 29. For example, the linear expansion coefficient of the cover member 60A may be substantially the same as the linear expansion coefficient of the exterior film 93. In this configuration, the expansion and contraction of the cover member 60A and the expansion and contraction of the exterior film 93 are approximately the same, thereby preventing stress from being generated in the exterior film 93 due to the expansion and contraction of the cover member 60A. Note that "the linear expansion coefficients of the cover member 60A and the exterior film 93 are substantially the same" means that the difference in the amount of expansion between them is small enough that it does not affect the durability of the exterior film.

[0083] The outer surfaces 20sC and 20sD may be covered by cover members having a configuration similar to that of the cover member 60A. In this case, the outer surface 20s is covered by four cover members combined to form a rectangular frame.

[0084] Although the example in which the outer surface 20sA is covered by the first cover member 60 and the second cover member 70 formed separately has been shown, for example, the first cover member 60 and the second cover member 70 may be formed integrally. In this case, a hole, a notch, or the like may be provided to expose the FPC to the outside of the cover member.

[0085] REFERENCE SIGNS LIST 1 Energy storage module 1A Module body 10 Electrode laminate 11 Bipolar electrode (electrode) 12 Positive terminal electrode (electrode) 13 Negative terminal electrode (electrode) 15 Current collector 29 Sealing body 60A Cover member 60 First cover member 70 Second cover member 80 Third cover member 90 Outer packaging pack S Internal space

Claims

1. An energy storage module comprising: an electrode stack in which a plurality of electrodes, each of which includes a current collector, are stacked in a first direction; a sealing body provided on the electrode stack so as to surround the electrode stack when viewed from the first direction, and configured to seal a plurality of internal spaces formed between each of the electrodes adjacent in the first direction; an exterior pack that houses the electrode stack and the sealing body; and a cover member interposed between the exterior pack and a side of the sealing body extending in the first direction, wherein the linear expansion coefficient of the cover member is smaller than the linear expansion coefficient of the sealing body.

2. The energy storage module according to claim 1, wherein the cover member contains a resin material and a filler, and the filler has a linear expansion coefficient lower than the linear expansion coefficient of the resin material.

3. The energy storage module described in claim 2, wherein the cover member extends along a second direction intersecting the first direction, and the filler is an inorganic material having a needle-like or fibrous shape and is oriented along the second direction within the cover member.

4. The energy storage module according to any one of claims 1 to 3, wherein the linear expansion coefficient of the exterior pack is equal to or lower than the linear expansion coefficient of the cover member, and the linear expansion coefficient of the cover member has a value closer to the linear expansion coefficient of the exterior pack than the linear expansion coefficient of the sealing body.

5. The difference between the expansion coefficients of the cover member and the exterior pack is 2.5×10 －５ The storage module according to claim 4 , wherein the thermal expansion coefficient is 0.01 to 0.1 [1 / ° C.] or less.

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