Power storage device

Abstract

A power storage device (1) includes a power storage module (2) that is formed by stacking a plurality of electrodes (12, 13) along a first direction (Z) and that has a first side surface (2a), a cover portion (4) disposed facing at least the first side surface (2a), and an exterior body (5) in which accommodation recesses (51a, 52a) are formed and the power storage module (2) and the cover portion (4) are disposed and accommodated in the accommodation recesses (51a, 52a). The cover portion (4) is disposed between the first side surface (2a) and first inner surfaces (51b, 52b) of the accommodation recesses (51a, 52a) facing the first side surface (2a), and has a first cover member (41) and a second cover member (42) adjacent to each other. The first cover member (41) has a second side surface (41a) in contact with the first inner surfaces (51b, 52b), and a first inclined surface (41b) on the opposite side of the second side surface (41a) and inclined with respect to the second side surface (41a). The second cover member (42) has a third side surface (42a) in surface contact with the power storage module (2), and a second inclined surface (42b) in surface contact with the first inclined surface (41b).

Description

Power storage device

[0001] The present disclosure relates to an electricity storage device.

[0002] Patent Document 1 discloses a bipolar battery having multiple current collector plates stacked with separators interposed between them. In this bipolar battery, the current collector plates are surrounded by frame members, and adjacent frame members in the stacking direction are airtightly joined. Separators arranged between the current collector plates are impregnated with an electrolyte.

[0003] Japanese Unexamined Patent Publication No. 2-177268

[0004] When a bipolar battery such as the one described above is sealed in an exterior body under reduced pressure and subjected to a thermal shock test, the exterior body may break.

[0005] The present disclosure provides an electricity storage device that can suppress breakage of an exterior body.

[0006] The inventors conducted extensive research to solve the above-mentioned problems and discovered that the outer casing breaks at the wrinkled areas after vacuum sealing, and that the wrinkles are caused by gaps between the energy storage module and the outer casing.

[0007] The energy storage device of the present disclosure comprises an energy storage module formed by stacking a plurality of electrodes along a first direction and having a first side surface, a cover portion arranged opposite at least the first side surface, and an exterior body having an accommodating recess in which the energy storage module and the cover portion are accommodated, the cover portion being arranged between the first side surface and a first inner side surface of the accommodating recess facing the first side surface and having a first cover member and a second cover member adjacent to each other, the first cover member having a second side surface in contact with the first inner side surface and a first inclined surface opposite the second side surface and inclined relative to the second side surface, and the second cover member having a third side surface in face-to-face contact with the energy storage module and a second inclined surface in face-to-face contact with the first inclined surface.

[0008] In the above energy storage device, a cover is disposed on at least the first side surface of the energy storage module. Therefore, the cover can fill a gap between the first side surface and the exterior body that occurs when attaching the exterior body to the energy storage module. The cover includes a first cover member and a second cover member. The second cover member has a third side surface that is in surface contact with the first side surface of the energy storage module and a second inclined surface that is in surface contact with the first inclined surface of the first cover member. Because the first side surface extends in the first direction, the third side surface also extends in the first direction. Because the first inclined surface is inclined with respect to the first direction, the second inclined surface is also inclined with respect to the first direction. In other words, the second cover member has a tapered shape when viewed from the second direction. Therefore, by changing the relative position of the second cover member with respect to the first cover member in the first direction, the overall length of the first cover member and the second cover member can be easily changed. Therefore, by combining two types of cover members, the tolerances of the energy storage module and the exterior body can be accommodated and the gap between the energy storage module and the exterior body can be reliably filled. As a result, wrinkling of the exterior body after vacuum sealing is suppressed, and breakage of the exterior body due to wrinkling can be suppressed.

[0009] The length of the second cover member in the first direction may be shorter than the length of the first cover member in the first direction.

[0010] The first side surface is a surface extending in a first direction of the energy storage module and a second direction intersecting the first direction, the first cover member and the second cover member are adjacent to each other in a third direction intersecting the first direction and the second direction, the energy storage module has a fourth side surface opposite the first side surface, the cover portion further has a third cover member arranged between the fourth side surface and a second inner side surface of the accommodating recess facing the fourth side surface, and the third cover member may have a fifth side surface in face-to-face contact with the fourth side surface and a sixth side surface in face-to-face contact with the second inner side surface.

[0011] The exterior body may have a first exterior part and a second exterior part, the first exterior part having a first conductive plate electrically connected to the storage module and a first exterior frame having an inner edge joined to the peripheral edge of the first conductive plate so as to expose a first surface of the first conductive plate opposite the storage module, the second exterior part having a second conductive plate electrically connected to the storage module and a second exterior frame having an inner edge joined to the peripheral edge of the second conductive plate so as to expose a second surface of the second conductive plate opposite the storage module, the outer edge of the first exterior frame and the outer edge of the second exterior frame being insulated from each other and joined, and the second cover member may have a first opposing surface facing the surface opposite the first surface of the first conductive plate in the first direction, and a second opposing surface facing the surface opposite the second surface of the second conductive plate in the first direction.

[0012] The joint area between the first exterior frame and the first conductive plate may overlap with the cover portion when viewed from the first direction.

[0013] When viewed from the first direction, the width of the second cover member extending in a second direction intersecting the first direction may be shorter than the width of the first cover member extending in the second direction.

[0014] The second side may extend in the first direction and a second direction intersecting the first direction, and the first cover member may have a pair of corners connected to both ends of the second side in the second direction and curved when viewed from the first direction.

[0015] According to the present disclosure, it is possible to provide an electricity storage device that can suppress breakage of the exterior body.

[0016] Fig. 1 is an exploded perspective view of an energy storage device according to one embodiment. Fig. 2 is a cross-sectional view of the energy storage device. Fig. 3 is a cross-sectional view of an energy storage module. Fig. 4 is a plan view of the energy storage module, a first cover member, and a second cover member. Figs. 5(a), 5(b), and 5(c) are cross-sectional views for explaining the relationship between the size of the gap and the position of the second cover member relative to the first cover member.

[0017] 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.

[0018] FIG. 1 is an exploded perspective view of a power storage device according to one embodiment. FIG. 2 is a cross-sectional view of the power storage device along the YZ plane. FIG. 2 shows a simplified view of a power storage module 2 included in the power storage device 1. The power storage device 1 is a power storage device used in batteries for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The power storage device 1 is a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. The power storage device 1 may be an electric double layer capacitor or an all-solid-state battery. Here, the case where the power storage device 1 is a lithium-ion secondary battery is shown.

[0019] The energy storage device 1 includes a power storage module 2, a connector unit 3, a cover 4, and an exterior body 5. In FIG. 1 , a first exterior body 51 and a second exterior body 52 that constitute the exterior body 5 are shown disassembled from each other. In FIG. 2 , the power storage module 2 is shown housed in the space inside the exterior body 5. The power storage module 2 has a rectangular shape when viewed from the Z-axis direction (first direction). When viewed from the Z-axis direction, the X-axis direction is the direction of the short sides of the power storage module 2, and the Y-axis direction is the direction of the long sides of the power storage module 2. The length of the power storage module 2 in the Y-axis direction is longer than the length of the power storage module 2 in the X-axis direction.

[0020] The energy storage module 2 has four side surfaces 2a, 2b, 2c, and 2d extending in the Z-axis direction. The side surfaces 2a and 2b also extend in the X-axis direction (second direction) and face opposite each other in the Y-axis direction (third direction). The side surfaces 2c and 2d also extend in the Y-axis direction and face opposite each other in the X-axis direction. As will be described later, both end surfaces of the energy storage module 2 in the Z-axis direction are formed by a negative terminal electrode 12 and a positive terminal electrode 13, and are used for extracting power.

[0021] 3 is a cross-sectional view of the energy storage module taken along the YZ plane. The energy storage module 2 includes an electrode stack 10 formed by stacking a plurality of electrodes along the Z-axis direction, and a sealing body 20 provided on the outer periphery of the electrode stack 10.

[0022] The electrode stack 10 includes a plurality of electrodes stacked along the Z-axis direction. The plurality of electrodes includes a plurality of bipolar electrodes 11, a negative terminal electrode 12 (second terminal electrode), and a positive terminal electrode 13 (first terminal electrode). Separators 14 are interposed between adjacent electrodes.

[0023] The bipolar electrode 11 includes a current collector 15, a positive electrode active material layer 16 (first active material layer), and a negative electrode active material layer 17 (second active material layer). The current collector 15 has, for example, a rectangular sheet shape. The current collector 15 includes a first surface 15a and a second surface 15b. As an example, the first surface 15a is a surface that intersects with the Z-axis direction, and the second surface 15b is a surface that intersects with the Z-axis direction and is opposite to the first surface 15a. In this example, the first surface 15a of the current collector 15 faces one side of the Z-axis direction (the direction from the positive electrode terminal electrode 13 toward the negative electrode terminal electrode 12 in FIG. 3). The second surface 15b of the current collector 15 faces the other side of the first direction (the direction from the negative electrode terminal electrode 12 toward the positive electrode terminal electrode 13 in FIG. 3).

[0024] The positive electrode active material layer 16 is provided on the first surface 15a of the current collector 15. The negative electrode active material layer 17 is provided on the second surface 15b of the current collector 15. The peripheral portion surrounding the positive electrode active material layer 16 on the first surface 15a of the current collector 15 and the peripheral portion surrounding the negative electrode active material layer 17 on the second surface 15b of the current collector 15 are each an unformed region (uncoated region) where no active material layer is provided. 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 another bipolar electrode 11 face each other via the separator 14. The positive electrode active material layer 16 and the negative electrode active material layer 17 of each bipolar electrode 11 may have grooves formed therein to improve liquid injection and gas escape properties.

[0025] The positive electrode active material layer 16 and the negative electrode active material layer 17 are rectangular when viewed from the Z-axis direction. The negative electrode active material layer 17 is slightly larger than the positive electrode active material layer 16 when viewed from the Z-axis direction. In a plan view when viewed from the Z-axis direction, the entire formation region of the positive electrode active material layer 16 is located within the formation region of the negative electrode active material layer 17. In other words, when viewed from the Z-axis direction, the outer edge 17e of the negative electrode active material layer 17 is located outside the outer edge 16e of the positive electrode active material layer 16.

[0026] The negative electrode terminal electrode 12 has a current collector 15 and a negative electrode active material layer 17 provided on a second surface 15b of the current collector 15. The negative electrode terminal electrode 12 does not have a positive electrode active material layer 16 or a negative electrode active material layer 17 on a first surface 15a of the current collector 15. In other words, no active material layer is provided on the first surface 15a of the current collector 15 of the negative electrode terminal electrode 12, and this forms the negative electrode terminal surface of the energy storage module 2. The negative electrode terminal electrode 12 is stacked on the bipolar electrode 11 at one end of the electrode stack 10 in the Z-axis direction. The negative electrode terminal electrode 12 is stacked on the bipolar electrode 11 via a separator 14 so that the negative electrode active material layer 17 faces the positive electrode active material layer 16 of the bipolar electrode 11.

[0027] The positive terminal electrode 13 has a current collector 15 and a positive electrode active material layer 16 provided on a first surface 15a of the current collector 15. The positive terminal electrode 13 does not have a positive electrode active material layer 16 or a negative electrode active material layer 17 on a second surface 15b, which is the surface opposite the first surface 15a of the current collector 15. In other words, no active material layer is provided on the second surface 15b of the current collector 15 of the positive terminal electrode 13, and this second surface 15b constitutes the positive electrode terminal surface of the energy storage module 2. The positive terminal electrode 13 is stacked on the bipolar electrode 11 at the other end of the electrode stack 10 in the Z-axis direction. The positive terminal electrode 13 is stacked on the bipolar electrode 11 such that the positive electrode active material layer 16 faces the negative electrode active material layer 17 of the bipolar electrode 11 with the separator 14 interposed therebetween.

[0028] In this embodiment, the current collectors of the bipolar electrode 11, the negative terminal electrode 12, and the positive terminal electrode 13 are designated by the same reference numeral as the current collector 15, but the materials constituting the current collectors of the bipolar electrode 11, the negative terminal electrode 12, and the positive terminal electrode 13 may be the same as or different from one another.

[0029] The separators 14 are respectively disposed between the bipolar electrodes 11 adjacent to each other in the Z-axis direction, between the negative terminal electrode 12 and the bipolar electrode 11, and between the positive terminal electrode 13 and the bipolar electrode 11. That is, the separators 14 are interposed between the positive electrode surface of the current collector 15 on which the positive electrode active material layer 16 is provided and the negative electrode surface on which the negative electrode active material layer 17 is provided. The separator 14 is a member that allows charge carriers such as lithium ions to pass through, and by isolating the positive electrode surface from the negative electrode surface, it prevents short circuits due to contact between adjacent electrodes.

[0030] 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 and / or conductive resin material.

[0031] 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, film, or mesh. Examples of metal foils include aluminum foil, copper foil, nickel foil, titanium foil, and stainless steel foil. The current collector 15 may be an alloy foil of the above metals or a foil formed by integrating multiple metal foils. 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 200 μm. The current collector 15 may be a foil formed by integrating aluminum foil and copper foil by bonding them together with a conductive adhesive, or a foil formed by vapor-depositing a copper layer on one side of aluminum foil.

[0032] 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 )

[0033] 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.

[0034] 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 a conductive additive, a binder, an electrolyte, an electrolyte supporting salt, etc., as necessary. The conductive additive is added to enhance electrical conductivity. Examples of the conductive additive include acetylene black, carbon black, and graphite. The electrolyte supporting salt is added to enhance ionic conductivity.

[0035] 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; 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 solvents for binders include water and N-methyl-2-pyrrolidone.

[0036] 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 multi-layer structure. The multi-layer 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 electrolyte impregnated in the separator 14 is a liquid electrolyte (electrolytic solution) containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.

[0037] The electrolyte salt of the electrolyte solution is LiClO ４ , 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.

[0038] The sealing body 20 is provided on the electrode stack 10 so as to surround the electrode stack 10 when viewed from the Z direction. For example, the sealing body 20 is formed on the peripheral portion of the electrode stack 10 as a rectangular tubular member so as to surround four side surfaces of the electrode stack 10, which is a substantially rectangular parallelepiped. The sealing body 20 can be joined (welded) 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 insulates adjacent current collectors 15 in the Z axis direction and forms an internal space S in cooperation with the adjacent current collectors 15. The sealing body 20 seals each of the internal spaces S. An electrolyte is accommodated in each internal space S. The sealing body 20 can prevent the electrolyte accommodated in the internal space S from leaking out to the outside. The sealing body 20 can also prevent air, moisture, and the like from entering the internal space S from outside the electrode stack 10.

[0039] The sealing body 20 includes an insulating material, and examples of the material 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.

[0040] The sealing body 20 includes a plurality of resin sealants 21 and a plurality of resin spacers 22. The sealants 21 are provided on each of the plurality of electrodes. More specifically, the sealants 21 are provided on the peripheral edge portions 15c of the current collectors 15. Therefore, the plurality of sealants 21 are stacked along the Z-axis direction. The sealants 21 provided on the peripheral edge portions 15c of the current collectors 15 are formed in a frame shape that follows the outline of the current collectors 15 when viewed from the Z-axis direction. Here, since the current collectors 15 are rectangular in plan view, the sealants 21 also have a rectangular frame shape when viewed from the Z-axis direction. The sealants 21 include an inner portion that overlaps the peripheral edge portions 15c of the current collectors 15 when viewed from the Z-axis direction, and an outer portion that extends beyond the edge of the current collectors 15. The sealing material 21 is formed by joining together and integrating an outer portion of one resin member joined to the first surface 15 a of the current collector 15 and another resin member joined to the second surface 15 b of the current collector 15. In other words, the sealing material 21 covers the peripheral portion 15 c of the current collector 15.

[0041] In this embodiment, the sealing materials provided on the current collector 15 of the bipolar electrode 11, the current collector 15 of the negative terminal electrode 12, and the current collector 15 of the positive terminal electrode 13 are each given the same reference numeral as a sealing material 21. However, the sealing material provided on the current collector 15 of the bipolar electrode 11, the sealing material provided on the current collector 15 of the negative terminal electrode 12, and the sealing material provided on the current collector 15 of the positive terminal electrode 13 may be the same as or different from one another.

[0042] The spacer 22 is formed in a generally frame-like shape so as to surround the positive electrode active material layer 16 when viewed from the Z-axis direction. When viewed from the Z-axis direction, the spacer 22 has an inner portion that overlaps the current collector 15 and an outer portion that extends beyond the edge of the current collector 15. The spacer 22 is disposed so as to be interposed between the seal materials 21 provided on electrodes adjacent in the Z-axis direction. As a result, the spacer 22, together with a pair of seal materials 21 adjacent in the Z-axis direction, maintains the spacing between the current collectors 15 adjacent in the Z-axis direction. An internal space S is defined by the pair of current collectors 15 adjacent in the Z-axis direction, the spacer 22, and the pair of seal materials 21 adjacent to the spacer 22.

[0043] When viewed from the Z-axis direction, the spacer 22 is formed in a frame shape that follows the outer shape of the current collector 15. Therefore, the sealing body 20 is configured by stacking multiple resin frames (sealing material 21 and spacers 22) provided on the peripheral portion 15c of the current collector 15 along the Z-axis direction, and seals the internal space S between electrodes adjacent in the Z-axis direction.

[0044] When viewed from the Z-axis direction, the inner edge 22e of the spacer 22 is located between the outer edge 17e of the negative electrode active material layer 17 and the outer edge 16e of the positive electrode active material layer 16. That is, the inner edge 22e of the spacer 22 is located more inward than the outer edge 17e of the negative electrode active material layer 17. As a result, the spacer 22 includes a portion that overlaps with the negative electrode active material layer 17 when viewed from the Z-axis direction. As a result, the internal space S is maintained. The multiple spacers 22 may be configured not to contact the current collectors 15 of adjacent bipolar electrodes 11. In other words, a small gap may be provided between the spacer 22 and the first surface 15a of the current collector 15 of the adjacent bipolar electrode.

[0045] The outer edges of the multiple sealants 21 and the multiple spacers 22 are welded together and integrated to form welded portions 23. That is, the sealing body 20 includes welded portions 23 formed by welding the multiple sealants 21 and the multiple spacers 22 together. When viewed from the Z-axis direction, the welded portions 23 have a frame shape (here, a rectangular frame shape) that surrounds the electrode stack 10 and forms the outer periphery of the sealing body 20. Therefore, the outer surfaces 23s of the welded portions 23 form the four side surfaces 2a, 2b, 2c, and 2d (see FIG. 1 ) of the energy storage module 2. The spacers 22 do not need to be welded to the sealing materials 21, at least in the inner portions of the sealing materials 21 adjacent to them in the Z-axis direction.

[0046] The end of the separator 14 may be held by being sandwiched between the sealant 21 and the spacer 22. The end of the separator 14 may be fixed by being welded to at least one of the sealant 21 and the spacer 22.

[0047] 1, the connector unit 3 is disposed on the side surface 2b. Wiring L is drawn out from the connector unit 3. The wiring L includes a voltage detection line extending from the electrode stack 10 and the like.

[0048] 1 and 2 , the cover 4 is disposed on the energy storage module 2. The cover 4 is disposed facing the side surface 2a and the side surface 2b of the energy storage module 2, respectively. The side surface 2b is the surface opposite to the side surface 2a. The cover 4 has a first cover member 41, a second cover member 42, a third cover member 43, and a fourth cover member 44. The cover 4 can fill gaps that occur between the energy storage module 2 and the exterior body 5 due to tolerances and manufacturing errors.

[0049] The first cover member 41, the second cover member 42, the third cover member 43, and the fourth cover member 44 may be formed, for example, from a mixed material of a resin as a main material and a filler. The main resin 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 main resin is 2.5 x 10 －５ It may be about [1 / °C].

[0050] The filler may be any material that reduces the linear expansion coefficient of the cover portion 4. 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-like or fibrous shape, it may have an anisotropic shape extending in a direction intersecting the longitudinal direction. In the cover portion 4, 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 2.3×10 －５ ~5.0 x 10 －５ It may be about [1 / °C].

[0051] The first cover member 41 and the second cover member 42 are arranged on the side surface 2a so as to cover the side surface 2a (first side surface) when viewed from the Y-axis direction. The length (maximum length) of the first cover member 41 in the X-axis direction is equal to the length of the side surface 2a in the X-axis direction. The first cover member 41 is arranged on the side surface 2a so as to cover the entire side surface 2a in the X-axis direction when viewed from the Y-axis direction. The first cover member 41 and the second cover member 42 are adjacent to each other in the Y-axis direction. The first cover member 41 and the second cover member 42 are arranged between the side surface 2a and the exterior body 5 in the Y-axis direction. The second cover member 42 is arranged between the side surface 2a and the first cover member 41 in the Y-axis direction.

[0052] 4 is a plan view of the energy storage module, the first cover member, and the second cover member. As shown in FIGS. 1, 2, and 4, the first cover member 41 has a side surface 41a (second side surface), an inclined surface 41b (first inclined surface), a pair of corners 41c, an end surface 41d, and an end surface 41e. The side surface 41a is a flat surface extending in the Z-axis direction and the X-axis direction. The side surface 41a faces the exterior body 5 in the Y-axis direction. The side surface 41a is covered by the exterior body 5. The side surface 41a contacts first inner side surfaces 51b and 52b of the exterior body 5, which will be described later.

[0053] The inclined surface 41b is located opposite the side surface 41a and is inclined with respect to the side surface 41a. The inclined surface 41b extends in the X-axis direction and is inclined with respect to the Z-axis direction. The angle between the inclined surface 41b and the Z-axis direction is greater than 0 degrees and less than 90 degrees. In other words, the inclined surface 41b is also inclined with respect to the Y-axis direction. The inclined surface 41b connects the end surface 41d and the end surface 41e to each other. The inclined surface 41b is inclined so as to move away from the side surface 41a as it moves from the end surface 41d to the end surface 41e.

[0054] The pair of corners 41c extend in the Z-axis direction. The pair of corners 41c are connected to both ends of the flat side surface 41a in the X-axis direction. The pair of corners 41c sandwich the side surface 41a in the X-axis direction. The pair of corners 41c are curved surfaces when viewed from the Z-axis direction. The corners 41c are chamfered, for example, into a rounded shape. The radius of curvature of the corners 41c is larger than the radius of curvature of the corner between the side surface 41a and the end surface 41d, and larger than the radius of curvature of the corner between the side surface 41a and the end surface 41e. The radius of curvature of the corner 41c is, for example, 25 mm. The radius of curvature of the corner between the side surface 41a and the end surface 41d and the radius of curvature of the corner between the side surface 41a and the end surface 41e are, for example, 1.5 mm.

[0055] The end face 41d faces the first exterior part 51 (described later) in the Z-axis direction. The end face 41e faces the second exterior part 52 in the Z-axis direction. The end faces 41d and 41e extend in the X-axis direction and the Y-axis direction. The end faces 41d and 41e face in opposite directions in the Z-axis direction.

[0056] The second cover member 42 is disposed so as not to overlap the pair of corners 41c when viewed from the Y-axis direction. When viewed from the Z-axis direction, the width of the second cover member 42 extending in the X-axis direction is shorter than the width (maximum width) of the first cover member 41 extending in the X-axis direction. Both ends of the second cover member 42 in the X-axis direction are located inward from both ends of the first cover member 41 in the X-axis direction by at least the length of the corners 41c in the X-axis direction.

[0057] The second cover member 42 has a side surface 42a (third side surface), an inclined surface 42b (second inclined surface), an end surface 42d (first opposing surface), and an end surface 42e (second opposing surface). The side surface 42a is parallel to the side surface 2a and is in surface contact with the side surface 2a of the energy storage module 2. The side surface 42a is a flat surface extending in the Z-axis direction and the X-axis direction. The side surface 42a faces the side surface 2a in the Y-axis direction.

[0058] The inclined surface 42b is parallel to the inclined surface 41b and is in surface contact with the inclined surface 41b. The inclined surface 42b extends in the X-axis direction and is inclined with respect to the Z-axis direction. The angle between the inclined surface 42b and the Z-axis direction is greater than 0 degrees and less than 90 degrees. In other words, the inclined surface 42b is also inclined with respect to the Y-axis direction. The inclined surface 42b connects the end surface 42d and the end surface 42e to each other. The inclined surface 42b is inclined so as to approach the side surface 42a from the end surface 42d toward the end surface 42e.

[0059] The end face 42d faces the first exterior part 51 (described later) in the Z-axis direction. The end face 42e faces the second exterior part 52 in the Z-axis direction. The end faces 42d and 42e extend in the X-axis direction and the Y-axis direction. The end faces 42d and 42e face in opposite directions in the Z-axis direction.

[0060] The length in the Z-axis direction of the first cover member 41 is equal to the length in the Z-axis direction of the energy storage module 2. The length in the Z-axis direction of the second cover member 42 is shorter than the length in the Z-axis direction of the first cover member 41. For this reason, in the example of FIG. 2 , a gap is formed between the end surface 42 e and the second exterior part 52.

[0061] 1 and 2, the third cover member 43 and the fourth cover member 44 are disposed on the side surface 2b (fourth side surface) and sandwich the connector unit 3 in the X-axis direction. The third cover member 43 and the fourth cover member 44 are disposed on the side surface 2b so as to cover the side surface 2b together with the connector unit 3 when viewed from the Y-axis direction. The third cover member 43 has a side surface 43a (fifth side surface) that contacts the side surface 2b and a side surface 43b (sixth side surface) that contacts the second inner surfaces 51c, 52c.

[0062] The exterior body 5 contains the energy storage module 2, the connector unit 3, and the cover 4. Here, the energy storage module 2, the connector unit 3, and the cover 4 are contained items housed in the internal space of the exterior body 5. The exterior body 5 has a first exterior part 51 that covers the positive terminal electrode 13, and a second exterior part 52 that covers the negative terminal electrode 12. The first exterior part 51 and the second exterior part 52 are insulated from each other. The first exterior part 51 and the second exterior part 52 are arranged to sandwich the contained items in the Z-axis direction.

[0063] The first exterior part 51 and the second exterior part 52 each have a conductive plate 53 and an exterior frame 54. The conductive plate 53 has a rectangular sheet shape. The conductive plate 53 may be, for example, a metal foil, for example, aluminum foil. The conductive plates 53 of the first exterior part 51 and the second exterior part 52 have, for example, the same shape and are made of, for example, the same material. The thickness of the conductive plate 53 is, for example, 100 μm.

[0064] The conductive plate 53 (first conductive plate 53A) of the first exterior part 51 is stacked on the positive terminal electrode 13. The first conductive plate 53A is electrically connected to the energy storage module 2. The first conductive plate 53A covers the second surface 15b of the positive terminal electrode 13 and is electrically connected to the positive terminal electrode 13. The first conductive plate 53A is in contact with an exposed portion of the second surface 15b of the positive terminal electrode 13 that is not covered by the sealing body 20 (i.e., a portion where the sealing material 21 is not provided when viewed from the Z-axis direction). The first conductive plate 53A includes a first surface 53a opposite the positive terminal electrode 13. A surface 53d of the first conductive plate 53A opposite the first surface 53a faces the end surface 41d of the first cover member 41 and the end surface 42d of the second cover member 42 in the Z-axis direction. The surface 53d of the first conductive plate 53A is arranged to face the second surface 15b of the positive terminal electrode 13.

[0065] The conductive plate 53 (second conductive plate 53B) of the second exterior part 52 is stacked on the negative electrode terminal electrode 12. The second conductive plate 53B is electrically connected to the energy storage module 2. The second conductive plate 53B covers the first surface 15a of the negative electrode terminal electrode 12 and is electrically connected to the negative electrode terminal electrode 12. The second conductive plate 53B is in contact with an exposed portion of the first surface 15a of the negative electrode terminal electrode 12 that is not covered by the sealing body 20 (i.e., a portion where the sealing material 21 is not provided when viewed from the Z-axis direction). The second conductive plate 53B includes a second surface 53b opposite the negative electrode terminal electrode 12. A surface 53e opposite the second surface 53b of the second conductive plate 53B faces the end surface 41e of the first cover member 41 and the end surface 42e of the second cover member 42 in the Z-axis direction. The surface 53e of the second conductive plate 53B is arranged facing the first surface 15a of the negative electrode terminal electrode 12.

[0066] The first surface 53a of the first conductive plate 53A and the second surface 53b of the second conductive plate 53B can each be used to extract current from the energy storage module 2. Furthermore, when a battery pack is formed using a plurality of energy storage devices 1 by stacking a plurality of energy storage devices 1 in the Z-axis direction and connecting them in series, a conductive plate, conductive adhesive, or the like is disposed between two energy storage devices 1 adjacent to each other in the Z-axis direction to electrically connect the plurality of energy storage devices 1. In other words, the first conductive plate 53A and the second conductive plate 53B can be used to electrically connect the plurality of energy storage devices 1.

[0067] The exterior frame 54 is configured to surround the outer periphery of the contents when viewed from the Z-axis direction. The exterior frame 54 has a rectangular frame shape when viewed from the Z-axis direction. The pair of exterior frames 54 are formed, for example, by embossing, so that the outer edges of the exterior frames 54 are closer to each other than the inner edges. As a result, the first exterior part 51 and the second exterior part 52 have rectangular parallelepiped recesses 51a, 52a (accommodation recesses) with the conductive plate 53 as the bottom. The exterior body 5 has the recesses 51a, 52a, and it can be said that the energy storage module 2 and the cover part 4 are accommodated in the recesses 51a, 52a. The recesses 51a, 52a have first inner surfaces 51b, 52b facing the side surface 2a and second inner surfaces 51c, 52c facing the side surface 2b. The first cover member 41 and the second cover member 42 are disposed between the side surface 2a and the first inner surfaces 51b, 52b. The third cover member 43 is disposed between the side surface 2 b and the second inner side surfaces 51 c, 52 c. The exterior frame 54 may be formed, for example, by welding together four strip-shaped sheets 55 along the four sides of a rectangle.

[0068] As an example, the exterior frame 54 includes a resin layer 56, a metal layer 57, and a resin layer 58. The exterior frame 54 is formed of a laminate film in which the resin layer 56, the metal layer 57, and the resin layer 58 are laminated in this order. The metal layer 57 is, for example, aluminum foil. The thickness of the metal layer 57 is, for example, 80 μm. The rigidity of the metal layer 57 is lower than the rigidity of the conductive plate 53. For example, an aluminum alloy in the JIS 1000 series is used for the conductive plate 53, and an aluminum alloy in the JIS 8000 series is used for the metal layer 57.

[0069] The resin layer 56 is an adhesive layer and is laminated on one side of the metal layer 57. The resin layer 58 is a protective layer and is laminated on the other side of the metal layer 57. The resin layers 56, 58 contain, for example, an acid-modified polyolefin resin. The exterior frame 54 may also contain a layer made of other resins such as polyolefin or nylon. The exterior frame 54 is provided on the energy storage module 2 with the resin layer 56 facing inward.

[0070] The inner edge of the exterior frame 54 is located inside the peripheral edge of the conductive plate 53 when viewed from the Z-axis direction. The inner edge 54a of the exterior frame 54 and the peripheral edge 53c of the conductive plate 53 are joined in an overlapping state. The exterior frame 54 has the inner edge 54a joined to the peripheral edge 53c on the end faces 41d and 41e. The inner edge 54a of the exterior frame 54 (first exterior frame 54A) of the first exterior part 51 is joined (welded) to the peripheral edge 53c of the first conductive plate 53A on the first surface 53a so as to expose the center of the first surface 53a. A joint area 61 between the first exterior frame 54A and the first conductive plate 53A overlaps with the cover part 4 when viewed from the Z-axis direction. An inner edge 54a of the exterior frame 54 (second exterior frame 54B) of the second exterior part 52 is joined (welded) to a peripheral edge 53c of the second conductive plate 53B on the second surface 53b so as to expose a central portion of the second surface 53b. A joining area 62 between the second exterior frame 54B and the second conductive plate 53B overlaps with the cover part 4 when viewed from the Z-axis direction.

[0071] In one example, the inner edge 54a of the exterior frame 54 and the peripheral edge 53c of the conductive plate 53 may be joined to each other by a resin material 59. The resin material 59 may be a rectangular frame-shaped sealing resin formed in a sheet. For example, the inner edge of the rectangular frame-shaped resin material 59 may be located inside the inner edge of the exterior frame 54, and the outer edge of the resin material 59 may coincide with the peripheral edge of the conductive plate 53.

[0072] The outer edge portions 54b of the pair of exterior frames 54 are insulated from each other and joined (welded) around the entire periphery, thereby forming a sealed space inside the exterior body 5. The end face 54c of the outer edge portion 54b of the first exterior frame 54A and the end face 54c of the outer edge portion 54b of the second exterior frame 54B are offset from each other around the entire periphery.

[0073] The wiring L is drawn out from the joint surface of the pair of exterior frames 54 to the outside of the exterior body 5. After the contents are housed in the exterior body 5, the interior of the exterior body 5 may be sealed in a depressurized state. In this case, the exterior body 5 is pressed by atmospheric pressure, causing the first conductive plate 53A to come into close contact with the positive terminal electrode 13 and the second conductive plate 53B to come into close contact with the negative terminal electrode 12.

[0074] An example of a manufacturing method for the energy storage device 1 will be described. First, the inner edge 54a of the exterior frame 54 is joined to the peripheral edge 53c of the conductive plate 53 using a resin material 59 to form the first exterior part 51 and the second exterior part 52. Next, the second exterior part 52 is placed on a workbench, and the energy storage module 2, connector unit 3, first cover member 41, third cover member 43, and fourth cover member 44 are placed in the recess 52a of the second exterior part 52. The connector unit 3 is attached to the energy storage module 2. The third cover member 43 and fourth cover member 44 may also be fixed to the energy storage module 2 in advance by adhesive or the like.

[0075] Next, the second cover member 42 is positioned so as to fill the gap between the side surface 2 a of the power storage module 2 and the inclined surface 41 b of the first cover member 41. At this time, the end surface 42 d of the second cover member 42 is pressed toward the second conductive plate 53B while the inclined surface 42 b of the second cover member 42 is slid relative to the inclined surface 41 b. As a result, the second cover member 42 is positioned so as to fill the gap, i.e., so that the inclined surface 42 b is in surface contact with the inclined surface 41 b of the first cover member 41 and the side surface 42 a is in surface contact with the side surface 2 a of the power storage module 2.

[0076] 5( a), 5(b), and 5(c) are cross-sectional views illustrating the relationship between the size of the gap and the position of the second cover member relative to the first cover member. Fig. 5 shows three examples in which the sizes (minimum lengths in the Y-axis direction) d1, d2, and d3 of the gap between the exterior body 5 and the energy storage module 2 are different from one another, such that d1<d2<d3. In all of the examples, the side surface 41a of the first cover member 41 is disposed in surface contact with the first inner surface 52b of the second exterior portion 52 (see Fig. 2).

[0077] 5A, when the gap size is d1, the second cover member 42 is in surface contact with the side surface 2a and the inclined surface 41b at position P1, filling the gap. At position P1, the end surface 42d is located at the same height as the end surface 41d. The end surface 42e is spaced apart from the second conductive plate 53B (see FIG. 2).

[0078] 5B, when the gap size is d2, the second cover member 42 is in surface contact with the side surface 2a and the inclined surface 41b at position P2, filling the gap. At position P2, the end surface 42d is located lower than the end surface 41d. Compared to position P1, at position P2, the end surface 42e is closer to the second conductive plate 53B (see FIG. 2).

[0079] 5C, when the size of the gap is d3, the second cover member 42 comes into surface contact with the side surface 2a and the inclined surface 41b at position P3, filling the gap. At position P3, the end surface 42d is located lower than the end surface 41d. At position P3, the end surface 42e abuts against the second conductive plate 53B (see FIG. 2). The upper limit of the size of the gap that can be filled by the first cover member 41 and the second cover member 42 is d3.

[0080] In this way, by changing the relative position of the second cover member 42 with respect to the first cover member 41 in the Z-axis direction, the relative position of the second cover member 42 with respect to the first cover member 41 in the Y-axis direction also changes, and the width of the gap that can be filled by the first cover member 41 and the second cover member 42 changes. The size of the gap changes because there is variation in the sizes of the energy storage module 2 and the exterior body 5 due to tolerances and manufacturing errors. By using the first cover member 41 and the second cover member 42 and adjusting the above-mentioned relative positions, the gap can be reliably filled.

[0081] Next, the first exterior part 51 is placed on the second exterior part 52 and the contents, and in a depressurized state, the outer edge parts 54b of the first exterior part 51 and the second exterior part 52 are welded to each other to form the exterior body 5. The welding of the outer edge parts 54b is performed with the end faces 54c misaligned with each other so as to maintain insulation between the outer edge parts 54b. As a result, the energy storage device 1 is obtained in which the energy storage module 2, connector unit 3, and cover part 4 are depressurized and sealed in the space within the exterior body 5.

[0082] As described above, in the energy storage device 1, the cover 4 is disposed on the side surface 2a of the energy storage module 2 (the outer surface 23s of the sealing body 20). Therefore, the cover 4 can fill a gap between the side surface 2a and the exterior body 5 that occurs when the exterior body 5 is attached to the energy storage module 2. The cover 4 disposed on the side surface 2a has a first cover member 41 and a second cover member 42 that are adjacent in the Y-axis direction. The second cover member 42 has a side surface 42a that is in surface contact with the side surface 2a and an inclined surface 42b that is in surface contact with the inclined surface 41b of the first cover member 41. Because the side surface 2a extends in the Z-axis direction, the side surface 42a also extends in the Z-axis direction. Because the inclined surface 41b is inclined with respect to the Z-axis direction, the inclined surface 42b is also inclined with respect to the Z-axis direction. In other words, the second cover member 42 has a tapered shape when viewed in the X-axis direction. Therefore, by changing the relative position in the Z-axis direction of the second cover member 42 with respect to the first cover member 41, the overall length in the Y-axis direction of the first cover member 41 and the second cover member 42 can be easily changed. Therefore, by combining two types of cover members, the first cover member 41 and the second cover member 42, it is possible to absorb the tolerances and manufacturing errors of the energy storage module 2 and the exterior body 5 and reliably fill the gap between the energy storage module 2 and the exterior body 5. As a result, the formation of wrinkles in the exterior body 5 after reduced pressure sealing is suppressed, and therefore breakage of the exterior body 5 due to wrinkles can be suppressed.

[0083] Because the length of the energy storage module 2 in the Y-axis direction is longer than the length of the energy storage module 2 in the X-axis direction, the gap between the energy storage module 2 and the exterior body 5 caused by tolerances and manufacturing errors is likely to be larger in the Y-axis direction than in the X-axis direction. The cover 4 can reliably fill the gap between the energy storage module 2 and the exterior body 5 in the Y-axis direction.

[0084] The length of the second cover member 42 in the Z-axis direction is shorter than the length of the first cover member 41 in the Z-axis direction. This prevents the second cover member 42 from protruding from the end faces 41d, 41e of the first cover member 41. This allows the energy storage device 1 to be made smaller in size in the Z-axis direction.

[0085] The side surface 2a is a surface extending in the Z-axis direction and the X-axis direction of the energy storage module 2. The first cover member 41 and the second cover member 42 are adjacent to each other in the Y-axis direction. The energy storage module 2 has a side surface 2b opposite to the side surface 2a. The cover unit 4 further has a third cover member 43 arranged between the side surface 2b and second inner surfaces 51c, 52c of the recesses 51a, 52a facing the side surface 2b. The third cover member 43 has a side surface 43a in surface contact with the side surface 2b and a side surface 43b in surface contact with the second inner surfaces 51c, 52c. The third cover member 43 can fill the other gap in the Y-axis direction between the energy storage module 2 and the exterior body 5.

[0086] The exterior body 5 has a first exterior part 51 and a second exterior part 52. The first exterior part 51 has a first conductive plate 53A and a first exterior frame 54A. The second exterior part 52 has a second conductive plate 53B and a second exterior frame 54B. An outer edge part 54b of the first exterior frame 54A and an outer edge part 54b of the second exterior frame 54B are insulated from each other and joined together. The second cover member 42 has an end face 42d facing a surface 53d opposite the first surface 53a of the first conductive plate 53A in the Z-axis direction, and an end face 42e facing a surface 53e opposite the second surface 53b of the second conductive plate 53B in the Z-axis direction. The first conductive plate 53A covers the end faces 41d and 41e of the first cover member 41, thereby improving sealing performance.

[0087] A joint region 61 between the first exterior frame 54A and the first conductive plate 53A overlaps with the cover portion 4 when viewed from the Z-axis direction. The first conductive plate 53A covers the end faces 41d and 41e of the first cover member 41, thereby improving sealing performance.

[0088] When viewed from the Z-axis direction, the width of the second cover member 42 extending in the X-axis direction is shorter than the width of the first cover member 41 extending in the X-axis direction.

[0089] The side surface 41a extends in the X-axis direction. The first cover member 41 has a pair of corners 41c that are connected to both ends of the side surface 41a in the X-axis direction and are curved when viewed in the Z-axis direction. Because the corners 41c are curved, wrinkles in the exterior body 5 near the corners 41c after vacuum sealing can be suppressed. As a result, breakage of the exterior body 5 due to wrinkles can be suppressed.

[0090] The first exterior frame 54A and the second exterior frame 54B each include a metal layer 57. The end faces 54c of the joined outer edge portions 54b are offset from each other, thereby preventing the metal layers 57 exposed at the end faces 54c from coming into contact with each other and causing a short circuit.

[0091] The first cover member 41 has a side surface 41a facing the exterior body 5 and a pair of corners 41c connected to both ends of the side surface 41a. The corners 41c are curved surfaces when viewed from the Z-axis direction. Therefore, compared to when the corners 41c are not curved surfaces, wrinkles in the exterior body 5 near the corners 41c after vacuum sealing can be suppressed. As a result, breakage of the exterior body 5 due to wrinkles can be suppressed. The second cover member 42 is positioned so as not to overlap the pair of corners 41c when viewed from the Y-axis direction. Therefore, the wrinkle suppression effect provided by the pair of corners 41c can be maintained.

[0092] 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.

[0093] In the energy storage device 1, the exterior frame 54 is joined to the conductive plate 53 on the end faces 41d, 41e of the first cover member 41, but the exterior frame 54 may be joined to the conductive plate 53 on the energy storage module 2. In this case, the energy storage module 2, the conductive plate 53, and the exterior frame 54 overlap in the Z-axis direction, thereby improving the rigidity of the energy storage device 1.

[0094] The exterior body 5 is not limited to a laminate film made of a metal layer and a resin layer. For example, the exterior body 5 may be a laminate film made of a resin film that does not include a metal layer. Such a resin film may be composed of a resin layer with low moisture permeability.

[0095] The first cover member 41 may be divided into multiple pieces in the X-axis direction. That is, the first cover member 41 may include multiple separate cover members adjacent to each other in the X-axis direction. In this case, the inclined surface 41b is formed by combining the inclined surfaces of the divided cover members.

[0096] The second cover member 42 may be divided into multiple pieces in the X-axis direction. That is, the second cover member 42 may include multiple separate cover members adjacent to each other in the X-axis direction. In this case, the inclined surface 42b is formed by combining the inclined surfaces of the divided cover members.

[0097] The third cover member 43 and the fourth cover member 44 may be integrally formed. In this case, the cover members may be provided with holes or notches for exposing the wiring L to the outside of the cover members.

[0098] The cover unit 4 may further include cover members that cover the side surfaces 2c and 2d. In this case, the four side surfaces 2a, 2b, 2c, and 2d are covered by the four cover members that are combined to form a rectangular frame.

[0099] An aspect of the present disclosure can be expressed as follows. [Clause 1] An energy storage device including: an energy storage module formed by stacking a plurality of electrodes along a first direction and having a first side surface; a cover portion disposed facing at least the first side surface; and an exterior body formed with an accommodating recess, the accommodating recess housing and accommodating the energy storage module and the cover portion, wherein the cover portion is disposed between the first side surface and a first inner side surface of the accommodating recess facing the first side surface and includes a first cover member and a second cover member adjacent to each other, the first cover member having a second side surface in contact with the first inner side surface and a first inclined surface opposite the second side surface and inclined with respect to the second side surface, and the second cover member having a third side surface in surface contact with the energy storage module and a second inclined surface in surface contact with the first inclined surface. [Clause 2] The energy storage device according to Clause 1, wherein a length in the first direction of the second cover member is shorter than a length in the first direction of the first cover member. [Clause 3] The energy storage device according to Clause 1 or 2, wherein the first side surface is a surface of the energy storage module extending in the first direction and a second direction intersecting the first direction, the first cover member and the second cover member are adjacent to each other in a third direction intersecting the first direction and the second direction, the energy storage module has a fourth side surface opposite the first side surface, the cover portion further has a third cover member arranged between the fourth side surface and a second inner side surface of the accommodating recess facing the fourth side surface, and the third cover member has a fifth side surface in surface contact with the fourth side surface and a sixth side surface in surface contact with the second inner side surface.Clause 4. The energy storage device according to any one of clauses 1 to 3, wherein the exterior body has a first exterior part and a second exterior part, the first exterior part has: a first conductive plate electrically connected to the energy storage module; and a first exterior frame having an inner edge joined to a peripheral edge of the first conductive plate so as to expose a first surface of the first conductive plate opposite to the energy storage module, the second exterior part has: a second conductive plate electrically connected to the energy storage module; and a second exterior frame having an inner edge joined to a peripheral edge of the second conductive plate so as to expose a second surface of the second conductive plate opposite to the energy storage module, an outer edge of the first exterior frame and an outer edge of the second exterior frame are joined to each other insulated from each other, and the second cover member has: a first opposing surface facing a surface of the first conductive plate opposite to the first surface in the first direction, and a second opposing surface facing a surface of the second conductive plate opposite to the second surface in the first direction. [Clause 5] The energy storage device according to Clause 4, wherein a joint region between the first exterior frame and the first conductive plate overlaps with the cover portion when viewed from the first direction. [Clause 6] The energy storage device according to any one of Clauses 1 to 5, wherein, when viewed from the first direction, a width of the second cover member extending in a second direction intersecting the first direction is shorter than a width of the first cover member extending in the second direction. [Clause 7] The energy storage device according to any one of Clauses 1 to 6, wherein the second side surface extends in the first direction and a second direction intersecting the first direction, and the first cover member has a pair of corners connected to both ends of the second side surface in the second direction and curved when viewed from the first direction.

[0100] REFERENCE SIGNS LIST 1 Energy storage device 2 Energy storage module 2a Side surface (first side surface) 4 Cover portion 5 Exterior body 10 Electrode stack 11 Bipolar electrode 12 Negative electrode terminal electrode 13 Positive electrode terminal electrode 41 First cover member 41a Side surface (second side surface) 41b Inclined surface (first inclined surface) 41c Corner portion 42 Second cover member 42a Side surface (third side surface) 42b Inclined surface (second inclined surface) 42d End surface (first opposing surface) 42e End surface (second opposing surface) 43 Third cover member 43a Side surface (fifth side surface) 43b Side surface (sixth side surface) 51 First exterior portion 51a Recess (accommodating recess) 51b First inner surface 51c Second inner surface 52 Second exterior portion 52a Recess (accommodating recess) 52b First inner surface 52c Second inner surface 53A First conductive plate 53B Second conductive plate 53a First surface 53b Second surface 53c Peripheral edge portion 53d Surface (surface opposite to the first surface) 53e Surface (surface opposite to the second surface) 54A First exterior frame 54B Second exterior frame 54a Inner edge portion 54b Outer edge portion 61 Bonding region

Claims

1. An energy storage device comprising: an energy storage module formed by stacking a plurality of electrodes along a first direction and having a first side surface; a cover portion arranged opposite at least the first side surface; and an exterior body formed with a storage recess that accommodates and positions the energy storage module and the cover portion in the storage recess; wherein the cover portion is arranged between the first side surface and a first inner side surface of the storage recess that faces the first side surface and has a first cover member and a second cover member that are adjacent to each other; the first cover member has a second side surface in contact with the first inner side surface and a first inclined surface opposite the second side surface and inclined relative to the second side surface; and the second cover member has a third side surface in surface contact with the energy storage module and a second inclined surface in surface contact with the first inclined surface.

2. The energy storage device according to claim 1, wherein the length of the second cover member in the first direction is shorter than the length of the first cover member in the first direction.

3. The energy storage device according to claim 1 or 2, wherein the first side surface is a surface of the energy storage module extending in the first direction and a second direction intersecting the first direction, the first cover member and the second cover member are adjacent to each other in a third direction intersecting the first direction and the second direction, the energy storage module has a fourth side surface opposite the first side surface, the cover portion further has a third cover member arranged between the fourth side surface and a second inner side surface of the accommodating recess facing the fourth side surface, and the third cover member has a fifth side surface in surface contact with the fourth side surface and a sixth side surface in surface contact with the second inner side surface.

4. The energy storage device according to claim 1 or 2, wherein the exterior body has a first exterior part and a second exterior part, the first exterior part has: a first conductive plate electrically connected to the energy storage module; and a first exterior frame having an inner edge joined to the peripheral edge of the first conductive plate so as to expose a first surface of the first conductive plate opposite the energy storage module, the second exterior part has: a second conductive plate electrically connected to the energy storage module; and a second exterior frame having an inner edge joined to the peripheral edge of the second conductive plate so as to expose a second surface of the second conductive plate opposite the energy storage module, the outer edge of the first exterior frame and the outer edge of the second exterior frame being joined to each other while being insulated from each other, and the second cover member has: a first opposing surface facing the surface opposite the first surface of the first conductive plate in the first direction, and a second opposing surface facing the surface opposite the second surface of the second conductive plate in the first direction.

5. The energy storage device according to claim 4, wherein a joint area between the first exterior frame and the first conductive plate overlaps with the cover portion when viewed from the first direction.

6. The energy storage device according to claim 1 or 2, wherein, when viewed from the first direction, the width of the second cover member extending in a second direction intersecting the first direction is shorter than the width of the first cover member extending in the second direction.

7. The energy storage device according to claim 1 or 2, wherein the second side surface extends in the first direction and a second direction intersecting the first direction, and the first cover member is connected to both ends of the second side surface in the second direction and has a pair of corners that are curved when viewed from the first direction.

Images