Power storage module

Abstract

To provide a power storage module which can suppress damage to an outer packaging pack caused by expansion due to temperature changes in a cover member.SOLUTION: A power storage module comprises: an electrode laminate in which electrodes are laminated in a first direction; a sealing body which is provided on the electrode laminate such that it surrounds the electrode laminate when viewed from the first direction; an outer packaging pack which houses the electrode laminate and the sealing body; and a cover member which is interposed between the outer packaging pack and a lateral surface of the sealing body extending in the first direction. The linear expansion coefficient of the cover member is lower than that of the sealing body.SELECTED DRAWING: Figure 6

Description

[Technical field]

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

[0002] Patent Document 1 discloses an electricity storage device. The electricity 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-87397 A Summary of the Invention [Problem to be solved by the invention]

[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. Since the resin sealing member expands significantly, there is a risk that the sealing member may come into contact with the exterior pack, causing damage to 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. [Means for solving the problem]

[0006] An electricity 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 that houses 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. The linear expansion coefficient of the cover member is smaller than the linear expansion coefficient of the sealing body.

[0007] In the above-mentioned energy storage module, since the cover member having a linear expansion coefficient smaller than that of the sealing body is disposed between the sealing body and the exterior pack, the influence of the sealing body on the exterior pack is reduced. That is, since 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, it is possible to suppress damage to the exterior pack caused by the expansion of the sealing body due to a temperature change.

[0008] An example of the cover member may contain a resin material and a filler, and the linear expansion coefficient of the filler may be 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] The linear expansion coefficient of the exterior pack may be lower than the linear expansion coefficient of the cover member. The linear expansion coefficient of the cover member may have a value closer to the linear expansion coefficient of the exterior pack than to the linear expansion coefficient 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 / ℃] or less. Effect of the Invention

[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 a change in temperature. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic exploded perspective view of an example of an electricity storage module. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an example of an electricity storage module. [Diagram 3] FIG. 3 is a schematic diagram showing one side of a module main body constituting an example of the electricity storage module. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 5 is a perspective view showing an example of a cover member. [Figure 6] FIG. 6 is a plan view illustrating an example of a cover member. [Figure 7] FIG. 7 is a partially enlarged view of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment will be described with reference to the drawings. In the description of the drawings, the same or equivalent elements are given the same reference numerals, and duplicated descriptions may be omitted. In addition, in the description, an orthogonal 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 the power storage module according to the present embodiment. FIG. 2 is a schematic cross-sectional view of the power storage module along the YZ plane. In FIG. 2, a module main body 1A included in the power storage module 1 is depicted in a simplified manner. The power storage module 1 is a power storage module used in batteries of various vehicles such as forklifts, hybrid cars, and electric cars. The power storage module 1 is a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. The power storage module 1 may be an electric double layer capacitor or an all-solid-state battery. Here, a case where the power storage module 1 is a lithium-ion secondary battery is shown.

[0016] The energy storage module 1 includes a module body 1A, a cover member 60A, a connector unit 30, and an exterior pack 90. ​​In FIG. 1, the module body 1A and the exterior pack 90 constituting the energy storage module 1 are shown disassembled from each other. In FIG. 2, the module body 1A is shown housed in the space inside the exterior pack 90. ​​The module body 1A has a rectangular shape when viewed from the Z-axis direction (first direction), and has four outer sides 20s extending in the Z-axis direction. The outer sides 20s are composed of outer sides 20sA and 20sB facing each other in the Y-axis direction (third direction), and outer sides 20sC and 20sD facing each other in the X-axis direction (second direction). Note that both end faces in the Z-axis direction of the module body 1A are composed of a positive terminal electrode 12 and a negative terminal electrode 13 as described later, 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 side 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 side 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 side surface 20sA of the module body 1A. FIG. 4 is a schematic cross-sectional view of an example of the module body 1A. FIG. 4 shows a cross-section taken along line IV-IV in FIG. 3. The outer side surface 20sA of the module body 1A includes a region R1 in which an additional member 50 (described later) is provided, and regions R2 and R3 adjacent to the region R1. In the example shown in FIG. 3, the region R2 is located on the negative side of the X-axis direction from the region R1, and the region R3 is located on the positive side of the X-axis direction from the region R1. The additional member includes a liquid injection port portion 53A used when injecting an electrolyte into the module body 1A. Therefore, in this specification, the outer side 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 a plurality of electrodes stacked along the Z-axis direction. The Z-axis direction is the stacking direction of the electrodes, which is the height direction of the energy storage module 1. The multiple electrodes include a plurality of 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 has a current collector 15, a positive electrode active material layer 16, and a negative electrode active material layer 17. The current collector 15 has a rectangular shape when viewed from the Z-axis direction, and is in the form of a sheet. 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 in the peripheral 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 is a surface facing the other side in the Z-axis direction (the side where the negative electrode terminal electrode 13 is arranged in FIG. 4), and the second surface 15b of the current collector 15 is a surface facing one side in the Z-axis direction (the side where the positive electrode terminal electrode 12 is arranged in FIG. 4). The multiple 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 to each other in the stacking direction face each other.

[0021] The positive terminal electrode 12 has a current collector 15 and a positive 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 active material layer 16 faces the negative 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 on the other side opposite to the side on which the positive electrode terminal electrode 12 is provided in the Z-axis direction. The negative electrode terminal electrode 13 is laminated on the bipolar electrode 11 so that the negative electrode active material layer 17 faces the positive electrode active material layer 16 of the bipolar electrode 11. 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 denoted by the same reference numeral as the current collector 15, but 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 each other.

[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 caused by contact between adjacent electrodes.

[0024] The current collector 15 is a chemically inactive electrical conductor for continuously passing a current through the positive electrode active material layer 16 and the negative electrode active material layer 17 during discharging or charging 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 the conductive resin material include resins in which a conductive filler is added to a conductive polymer material or a non-conductive polymer material as necessary. The current collector 15 may have a plurality of 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, a foil (e.g., a metal foil), a film, or a mesh. Examples of the 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 an aluminum foil and a 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, polyanion-based compounds, and the like. 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 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 any of 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 capable of being alloyed with lithium or a compound thereof. Examples of carbon include natural graphite, artificial graphite, hard carbon (hardly graphitizable carbon), and soft carbon (easily graphitizable carbon). Examples of artificial graphite include highly oriented graphite and mesocarbon microbeads. Examples of elements capable of being 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 assistant for enhancing electrical conductivity, a binder, an electrolyte (polymer matrix, ion-conductive polymer, electrolyte solution, etc.), an electrolyte supporting salt (lithium salt) for enhancing ion conductivity, etc. The conductive assistant is added to enhance the conductivity of each electrode (bipolar electrode 11, positive electrode terminal electrode 12, negative electrode terminal electrode 13). The conductive assistant is, for example, acetylene black, carbon black, graphite, etc.

[0029] Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluorine rubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, acrylic resins such as acrylic acid or 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 can be used alone or in combination. Examples of the solvent 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 have, 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 held in a polymer matrix.

[0031] When the separator 14 is impregnated with an electrolyte, the electrolyte salt is LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiCF 3 SO 3 , LiN(FSO 2 ) 2 , LiN(CF 3 SO 2 ) 2 As the non-aqueous solvent, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, ethers, etc. may be used. Two or more of these known solvent materials may be used in combination.

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

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

[0034] The seal body 20 of the example 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. In addition, the seal body 20 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 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 through the end face to the second surface 15b, and covers the peripheral portion 15c. That is, 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 on the first surface 15a and the second surface 15b of the current collector 15 when viewed from the Z direction, and the outer portions of the pair of seal materials 21 adjacent to each other across the current collector 15 are connected to each other. The sealant 21 can be welded to at least one of the first surface 15a and the second surface 15b of the current collector 15. The sealant 21 of the present embodiment is welded to both the first surface 15a and the second surface 15b of the current collector 15.

[0035] The end seal material 24 has a frame shape when viewed from the Z-axis direction, and is provided along the peripheral portion 15c of the current collector 15 constituting the positive terminal electrode 12 and the negative terminal electrode 13, respectively. Therefore, the end seal material 24 is arranged so as to sandwich the plurality of seal materials 21 from 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. The end seal material 24 of this embodiment 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 disposed along the peripheral portion 15c of the current collector 15. The spacer 22 is disposed so as to be interposed between the seal materials 21 adjacent to each other in the Z-axis direction. The spacer 22 is also disposed 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. That is, 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 23 is formed by welding 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 23 has a frame shape surrounding the electrode stack 10. The side of the welded end 23 on the opposite side to the internal space S extends along the Z-axis direction and constitutes the outer side 20s of the sealing main body 20. In other words, the sealing main body 20 includes the outer side 20s on the opposite side to the internal space S. The outer side 20s may be formed as a flat surface.

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

[0039] The additional member 50 is formed so as to overlap with a 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 respectively communicating 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 of the additional member 50 includes a main body portion 51, a first overhang portion 55, and a second overhang portion 57.

[0040] The main body 51 partially covers the outer surface 20sA. For example, the main body 51 covers the outer surface 20sA so as to include the region R1 in which the plurality of communication holes 27 are formed on the outer surface 20sA. As described above, the plurality of communication holes 27 are connected to the plurality of internal spaces S. In the example shown in FIG. 3, 30 communication holes 27 corresponding to the 30 layers of internal spaces formed between the current collectors 15 are arranged in a discrete manner 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 side as the base end are arranged at equal intervals along the X-axis direction, and the communication holes 27 corresponding to the internal spaces of the 11th to 20th layers and the communication holes 27 corresponding to the internal spaces of the 21st to 30th layers are arranged in order 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 a rectangular plate shape having a predetermined thickness in the Y-axis direction. The main body 51 has an opening 52 at a position corresponding to the communication hole 27. The main body 51 also has a protruding frame portion 53 that protrudes from the outer surface 20sA in the Y-axis direction intersecting (orthogonal to) the outer surface 20sA. The protruding frame portion 53 surrounds each of the openings 52 as viewed from the Y-axis direction, and functions as a partition wall that separates each of 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 arranged vertically, are arranged in the X-axis direction.

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

[0043] In one example, the main body 51 includes a terminal portion 58 for voltage detection. The terminal portion 58 is formed in the main body 51 at a position shifted toward the positive side in the X-axis direction from the liquid injection port portion 53A formed by the multiple protruding frame portions 53. For example, the terminal portion 58 is provided adjacent to the protruding frame portion 53 formed at the end portion on the positive side in the X-axis direction via the flat surface 51a. In one example, the terminal portion 58 is provided at the end portion on the positive side in the X-axis direction of the main body 51. The terminal portion 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 terminal 58a may be, for example, a metal pin as long as it is electrically connected to the current collector 15. The connector unit 30 is fixed to the terminal portion 58 (see FIG. 6 and FIG. 7). The connector unit 30 as an example includes a housing 31 having a plurality of contacts connected to a plurality of terminals 58a, 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 by connecting both ends of the main body portion 51 in the Z-axis direction. The first overhang portion 55 partially covers one end edge (positive side in the Z-axis direction) of the welded end portion 23 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 end edge 55a of the first overhang portion 55 extends from the end 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 from 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 (negative side in the Z-axis direction) of the welded end portion 23 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 from 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 as the main body portion 51 in the X-axis direction.

[0046] 1 and 2 again. The exterior pack 90 accommodates the module 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 having 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, and may be, for example, an 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 by 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 constituting a rectangle to each other. The first exterior film 93A in the illustrated example 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 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 to each other by a resin material 95. The resin material 95 may be a rectangular frame-shaped sealing resin formed in a sheet shape. 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 edge of the first exterior film 93A and the outer edge of the second exterior film 93B are joined to each other. As an example, the outer edge of the first exterior film 93A and the outer edge of 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 edge of the first exterior film 93A and the outer edge of 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 accommodated 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, so that the pair of conductive members 91 are in close contact with the positive electrode terminal electrode 12 and the negative electrode terminal electrode 13, respectively. In addition, when the first exterior film 93A and the second exterior film 93B are joined to each other, 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 accommodated in the exterior pack 90 together with the module body 1A and the connector unit 30 in a state in which it is disposed between the outer surface 20s of the module body 1A and the exterior film 93. That is, the cover member 60A is interposed between the outer surface 20s and the exterior film 93. In the example of the 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 body 1A and the exterior film 93, and a third cover member 80 disposed between the outer surface 20sB of the module body 1A and the exterior film 93. The first cover member 60 is disposed on the outer surface 20sA on the negative side in the X-axis direction relative to the terminal portion 58. The second cover member 70 is disposed so as to cover the outer surface 20sA on the positive side in the X-axis direction relative to the terminal portion 58.

[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 in a state in which they are 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 opposed to each other in the Z-axis direction, and a third wall portion 63 extending in the XZ plane so as 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 opposed to each other in the X-axis direction, which extend in the YZ plane so as 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 fourth wall portion 64, and the connection portion 60e between the third wall portion 63 and the fourth wall portion 64 are formed in a chamfered shape such that the corners are chamfered. The chamfered shape may be, for example, a shape such as an R chamfer. In other words, the corners formed by the connection between the walls 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 in the hollow interior of the first cover member 60. The ribs 67 are plate-shaped extending along the YZ plane and connect the first wall portion 61, the second wall portion 62, and the third wall portion 63 to each other. The multiple ribs 67 may be arranged at equal intervals in the X-axis direction. As an example, the interval between adjacent ribs 67 is larger than the interval between the first wall portion 61 and the second wall portion 62 and is smaller than twice the interval between the first wall portion 61 and the second wall portion 62. The first wall portion 61, the second wall portion 62, the fourth wall portion 64, the fifth wall portion 65, and the end faces of the ribs 67 facing the opposite side to the third wall portion 63 constitute a wall surface 69 facing the third wall portion 63.

[0056] The first wall portion 61 and the second wall portion 62 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 length shorter than the first region 60R1 and the second region 60R2 in the Y-axis direction. 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 portion 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 separated from the liquid inlet portion 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, 69b when viewed from the Z-axis direction (i.e., in the opposite direction to 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 extend in the YZ plane to connect the first wall portion 71, the second wall portion 72, and the third wall portion 73 and face each other in the X-axis direction.

[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 in a chamfered shape such that the corners are chamfered. The chamfered shape may be, for example, a shape such as an R chamfer. In other words, the corners formed by the connection between the walls 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 in the hollow interior of the second cover member 70. The rib 77 is in the form of a plate extending along the YZ plane, and connects the first wall portion 71, the second wall portion 72, and the third wall portion 73 to each other. The multiple ribs 77 may be disposed at equal intervals in the X-axis direction. As an example, the interval between adjacent ribs 77 is larger than the interval between the first wall portion 71 and the second wall portion 72, and is smaller than twice the interval between the first wall portion 71 and the second wall portion 72. The first wall portion 71, the second wall portion 72, the fourth wall portion 74, the fifth wall portion 75, and the end faces of the rib 77 facing the opposite side to the third wall portion 73 constitute 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, the corners 70k connecting the third wall portion 73 and the fourth wall portion 74 of the first wall portion 71 and the second wall portion 72 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. Also, 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] The wall surface 79 of the second cover member 70 faces the region R3 of the outer surface 20sA and is in contact with the outer surface 20sA. In the illustrated example, in the vicinity of the fourth wall portion 74, the first wall portion 71 and the second wall portion 72 are formed with a notch-shaped portion 78 that avoids interference with the end portion 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 in the vicinity of the fourth wall portion 74 is separated 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 portion 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 XZ plane so as 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 YZ plane so as 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). The third cover member 80 in one example has a substantially rectangular shape when viewed from the Z-axis direction, and an end surface 89 facing the outer side surface 20sB is formed flat. This end surface 89 may be in contact with the outer side surface 20sB over the entire area in the X-axis direction. The corners that connect the walls may be formed into a chamfered shape when viewed from any of the X-axis direction, the Y-axis direction, and the Z-axis direction. Moreover, the third cover member 80 may be divided into a plurality of parts.

[0064] The first cover member 60, the second cover member 70, and the third cover member 80 may restrict the module body 1A from moving 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 body 1A. For example, a protrusion or a recess may be formed on the sealing body 29 of the module 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. Also, the first cover member 60, the second cover member 70, and the third cover member 80 may be fixed to the module body 1A by adhesion 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 larger 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 -5It should be noted that since the proportion 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 body 1A along the X-axis direction may be about 700 mm to 1800 mm, the length L2 of the module body 1A along the Y-axis direction may be about 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 about 5 mm to 100 mm, and the length L4 of the third cover member 80 along the Y-axis direction may be about 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 body 1A along the X-axis direction. In addition, 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 body 1A along the X-axis direction. That is, the positions of both ends of the cover member 60A and the positions of both ends of the module body 1A in the X-axis direction at room temperature may be approximately the same. In addition, when the first cover member 60 and the second cover member 70 expand due to an increase in temperature, the expansion toward each other is suppressed by the connector unit 30, and therefore they can expand in directions 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 linear expansion coefficient of the exterior film 93 having a metal layer 93a such as aluminum as an intermediate layer is close to the linear expansion coefficient of the metal layer 93a. In one example, the linear expansion coefficient of the exterior film 93 is 2 to 3×10 -5 [1 / ° C.] 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 does not damage the exterior film 93 when a temperature change of about 100° C. occurs. For example, when the cover member 60A expands due to a temperature change, the expanded cover member 60A may press the exterior film 93, causing stress 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 causes the stress generated in the exterior film 93 not to exceed 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 formula (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 linear expansion coefficient α of the third cover member 80. C and the linear expansion coefficient α of the exterior film 93 F Difference from (α C -α F ) and the change temperature T. That is, the following equation (2) holds: ε = T(α C -α F )...Equation (2)

[0071] In this case, the stress (σ) generated in the exterior film 93 is calculated by the following equation (1) and equation (2): σ=ET(α C -αF ), so that the stress (σ) generated in the exterior film 93 does not exceed the breaking strength of the exterior film 93, the linear expansion coefficient α of the third cover member 80 is C The condition required is expressed by the following formula (3), where F is the breaking strength of the exterior film 93. α C ≦(F / (ET))+α F ··· Equation (3)

[0072] For example, the linear expansion coefficient, 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 about 5.0×10 -5 [1 / °C] or less. In other words, the difference in linear expansion coefficient between the third cover member 80 and the exterior film 93 may be 2.5×10 -5 [1 / ℃] or less.

[0073] The cover member 60A, as an example, may be formed of a mixed material of a resin as a main material and a filler (filling 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 the main material of the cover member may be a 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 a plurality of polymers such as modified polyphenylene ether are mixed. 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 the main material of the cover member 60A is 2.5×10 -5 It may be on the order of [1 / ℃].

[0074] The filler may be a 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 orientation 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 at a ratio of about 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 on the order of [1 / ℃].

[0075] As described above, the example energy storage module 1 includes an electrode stack 10 in which multiple 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 multiple 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 extending 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 power storage module, the cover member 60A having a linear expansion coefficient smaller than that of the sealing body 29 is disposed between the sealing body 29 and the exterior pack 90, so that the influence of the sealing body 29 and the cover member 60A as the contained objects on the exterior pack 90 is reduced. That is, since the linear expansion coefficient of the cover member 60A is smaller than that of the sealing body 29, the difference in the thermal expansion coefficient between the cover member 60A and the exterior pack 90 is smaller than the difference in the thermal expansion coefficient between the sealing body 29 and the exterior pack 90. ​​Therefore, when a temperature change occurs in the power 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. Therefore, it is possible to suppress damage to the exterior pack caused by the expansion of the sealing body 29 accompanying a temperature change. That is, the thermal shock resistance of the power storage module 1 is improved.

[0077] 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. With this configuration, the cover member 60A, which is mainly made of a resin material, can have a lower thermal expansion coefficient.

[0078] The cover member 60A, as an example, may extend along the X-axis direction. The filler is 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, so that the linear expansion coefficient in the X-axis direction can be efficiently reduced. In this case, the mixture 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. In this configuration, it is possible to 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 changing 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 power storage module main body is also small, so that the amount of variation in the amount of dimensional change of the power storage module main body and the cover member, which are the main members arranged inside the exterior film, is 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 larger than the expansion coefficient of the exterior film 93 is shown as an example in which the expansion coefficient of the cover member 60A is smaller than the expansion coefficient of the sealing body 29, but the expansion coefficient of the cover member 60A may be smaller than the expansion coefficient of the exterior film 93.

[0082] The linear expansion coefficient of the exterior pack 90 as an example 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 have a value closer to the linear expansion coefficient of the exterior pack 90 than 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, so that it is possible to suppress the occurrence of stress in the exterior film 93 due to the expansion and contraction of the cover member 60A. Note that the linear expansion coefficient of the cover member 60A and the linear expansion coefficient of the exterior film 93 being substantially the same means that the difference in the amount of expansion between them is low enough not to 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 into a rectangular frame shape.

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

[0085] 1...energy storage module, 1A...module main 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 pack, S...internal space.

Claims

1. 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 the electrodes adjacent to each other in the first direction; an exterior pack that houses the electrode stack and the sealing body; a cover member interposed between a side surface of the sealing body extending in the first direction and the exterior pack, the cover member has a linear expansion coefficient smaller than that of the sealing body; The exterior pack is sealed with the interior thereof depressurized.

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

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

4. a linear expansion coefficient of the outer packaging pack is equal to or less than a linear expansion coefficient of the cover member; 4. The energy storage module according to claim 1, wherein the cover member has a linear expansion coefficient closer to the linear expansion coefficient of the exterior pack than to the linear expansion coefficient of the sealing body.

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

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