Power storage module

Abstract

A power storage module 11 is provided with an electrode laminate 12 and a resin sealing part 13. The sealing part 13 includes: a plurality of seal layers 30 which each have a first region R1 that is welded to a peripheral edge part 21c of a collector 21 and a second region R2 that protrudes beyond an outer edge 21d of the collector 21; and a spacer layer 33 which is provided between the seal layers 30 adjacent to each other in the lamination direction. The plurality of seal layers 30 include first seal layers 31 that are provided on a second surface 21b of a positive terminal electrode 16 and a first surface 21a of a negative terminal electrode 17. The first seal layers 31 each include a first resin layer 41, a gas barrier resin layer 42, and a second resin layer 43. Outer edge parts of the plurality of seal layers 30 including a pair of the first seal layers 31 and an outer edge part of the spacer layer 33 form an end face welding part 34 by being integrated with each other by means of welding. The gas barrier resin layer 42 is provided so as to overlap at least the second region R2.

Description

Energy storage module

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

[0002] Patent Document 1 discloses a bipolar battery. This bipolar battery is constructed by stacking bipolar plates, each of which has a positive electrode active material coating layer on one side of a conductive plate and a negative electrode active material coating layer on the other side. An electrically insulating frame is adhered to the periphery of the conductive plate.

[0003] Patent No. 2623311

[0004] In the battery (energy storage module) disclosed in Patent Document 1, an electrically insulating surrounding frame (sealing layer) is provided so as to extend beyond the outer edges of the conductive plates. This extending sealing layer from the outer edges of the conductive plates may form a resin sealing portion that seals the internal space between the electrodes. It is known that gases with small molecular diameters can pass through the gaps between the molecular bonds of resins with wide molecular chains. Therefore, in the case of large batteries, there is a risk that air may enter the cell or the electrolyte inside the cell may leak out through the thin sealing layer located at the stack edge exposed to the atmosphere.

[0005] An object of the present disclosure is to provide an electricity storage module that can suppress gas permeation through a sealing portion.

[0006] An energy storage module according to one aspect of the present disclosure includes a stack of multiple electrodes, each having a current collector, and a resin sealing portion provided on the peripheral edge of the current collector so as to surround the stack when viewed in the stacking direction of the multiple electrodes. The multiple electrodes include a pair of terminal electrodes and a bipolar electrode disposed between the pair of terminal electrodes in the stacking direction. In each of the pair of terminal electrodes, the current collector has an inner surface facing the bipolar electrode and an outer surface facing away from the inner surface. The sealing portion includes multiple sealing layers, each having a first region welded to the peripheral edge of the current collector and a second region extending beyond the outer edge of the current collector, and a spacer layer provided between adjacent sealing layers in the stacking direction. The multiple sealing layers include a first sealing layer provided on the outer surface. The first seal layer includes a first resin layer welded to the outer surface, a gas barrier resin layer provided on the first resin layer and having a lower gas permeability than the first resin layer, and a second resin layer provided on the gas barrier resin layer and sandwiching the gas barrier resin layer between the first resin layer and the second resin layer. At least on an end face of the second region as viewed from the stacking direction, outer edges of the plurality of seal layers including the pair of first seal layers and outer edges of the spacer layer are welded together to form an end face welded portion. The gas barrier resin layer is provided so as to overlap at least the second region as viewed from the stacking direction.

[0007] In the above-described energy storage module, the first sealing layer, which is the outermost sealing layer, includes a gas barrier resin layer having low gas permeability, thereby making it possible to suppress gas permeation through the sealing portion.

[0008] The first sealing layer may be formed by connecting a plurality of sheet materials and may include a connecting portion formed by welding the first resin layer and the second resin layer of two sheets of overlapping sheet materials together. In the connecting portion, the first resin layer and the second resin layer may be made of a polyolefin resin.

[0009] The first resin layer may be a polyolefin resin, and the plurality of sealing layers may further include a second sealing layer provided on the inner surface. The second sealing layer may include a third resin layer made of a polyolefin resin and welded to the inner surface. The sealing portion may further include an outer edge weld portion in which the first resin layer and the third resin layer are integrated with each other by welding so as to cover the outer edge of the current collector.

[0010] When viewed from the stacking direction, the outer edge welded portion may be spaced apart from the end face welded portion. When viewed from the stacking direction, the gas barrier resin layer may be provided at least between the outer edge welded portion and the end face welded portion.

[0011] The second sealing layer may further include a core resin layer provided on the third resin layer and having higher crystallinity than the third resin layer.

[0012] According to the present disclosure, it is possible to provide an electricity storage module that can suppress gas permeation through a sealing portion.

[0013] FIG. 1 is a schematic plan view showing an energy storage module according to a first embodiment. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a cross-sectional view showing an enlarged portion of FIG. 2. FIG. 4 is a cross-sectional view for explaining a method of forming an outer edge welded portion. FIG. 5 is a cross-sectional view showing an enlarged portion of an energy storage module according to a second embodiment. FIG. 6 is a cross-sectional view showing an enlarged portion of an energy storage module according to a third embodiment. FIG. 7 is a plan view showing a first sealing layer according to a modified example.

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted. In the description, a Cartesian coordinate system defined by X-axis, Y-axis, and Z-axis may be referenced.

[0015] First Embodiment FIG. 1 is a schematic plan view of an energy storage module according to a first embodiment. The energy storage module 11 according to the first embodiment shown in FIG. 1 can be used as a battery for various vehicles, such as a forklift, a hybrid vehicle, or an electric vehicle. The energy storage module 11 is, for example, a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. The energy storage module 11 may be an electric double layer capacitor or an all-solid-state battery. In this embodiment, a bipolar lithium-ion secondary battery is exemplified as the energy storage module 11.

[0016] FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, and schematically shows the layer structure of the energy storage module 11. FIG. 3 is a cross-sectional view showing an enlarged portion of FIG. 2. The energy storage module 11 shown in FIGS. 1 to 3 is a single cell having a rectangular parallelepiped shape that is flattened in the Z-axis direction. The energy storage module 11 has a length (length in the X-axis direction) and width (length in the Y-axis direction) of, for example, 100 cm or more. As an example, the length is 150 cm and the width is 120 cm.

[0017] The energy storage module 11 includes an electrode stack (stack) 12 and a resin sealing portion 13. The electrode stack 12 is configured by stacking a plurality of electrodes, each having a current collector 21. The stacking direction of the plurality of electrodes is along the Z-axis direction and coincides with the stacking direction of the energy storage modules 11 in the module stack formed by stacking the energy storage modules 11. The plurality of electrodes includes a plurality of bipolar electrodes 14 and a pair of terminal electrodes, a positive terminal electrode 16 and a negative terminal electrode 17.

[0018] The plurality of bipolar electrodes 14 are disposed between the positive terminal electrode 16 and the negative terminal electrode 17 in the stacking direction. The bipolar electrodes 14 include a current collector 21, a positive electrode active material layer 22, and a negative electrode active material layer 23. The current collector 21 is a chemically inactive electrical conductor that allows current to continue to flow through the positive electrode active material layer 22 and the negative electrode active material layer 23 during discharging or charging of the lithium-ion secondary battery.

[0019] The current collector 21 is a sheet-like conductive member having a rectangular shape in a plan view. The current collector 21 has a first surface 21a and a second surface 21b located on the opposite side of the first surface 21a. The current collector 21 is made of metal and is composed of, for example, a metal foil or an alloy foil. Examples of metal foils include copper foil, aluminum foil, titanium foil, and nickel foil. Examples of alloy foils include stainless steel foil (e.g., SUS304, SUS316, SUS301, etc., as specified in JIS G 4305:2015), plated steel foil, and stainless steel foil. The alloy foil may be an alloy foil of the metals listed above as examples of the metal foil material. The current collector 21 may be formed by integrating or laminating multiple metal foils, or by plating another metal layer on the surface of one metal foil.

[0020] In the illustrated example, the current collector 21 is formed by bonding an aluminum foil 21A and a copper foil 21B together so that the first surface 21a is an aluminum layer and the second surface 21b is a copper layer. The current collector 21 may be, for example, a clad foil formed by overlapping and roll-bonding an aluminum foil 21A and a copper foil 21B. The current collector 21 may also be a laminated foil. That is, the current collector 21 may be formed by bonding and integrating the aluminum foil 21A and the copper foil 21B with a conductive adhesive resin (adhesive layer) so that the first surface 21a is an aluminum layer and the second surface 21b is a copper layer. The current collector 21 may be formed by copper vapor deposition or copper plating on one side of an aluminum foil so that the first surface 21a is an aluminum layer and the second surface 21b is a copper layer. The aluminum layer on the first surface 21a of the current collector 21 may be chromate-treated. Furthermore, the copper layer on the second surface 21b of the current collector 21 may be nickel-plated. In this case, the nickel-plated layer may be a roughened surface, i.e., a protruding plated surface having fine protrusions on its surface. The roughened surface may be rougher than the unprocessed metal foil, and may be formed by roughening processes such as etching and electroplating. For example, the thickness of the current collector 21 may be approximately 30 μm to 150 μm, but is not limited to this.

[0021] The positive electrode active material layer 22 is provided on the first surface 21a of the current collector 21. The current collector 21 and the positive electrode active material layer 22 provided on the first surface 21a of the current collector 21 constitute the positive electrode of the bipolar electrode 14. The positive electrode active material layer 22 is formed in a rectangular shape in the center of the first surface 21a so that the peripheral edge portion 21c of the current collector 21 is exposed.

[0022] The positive electrode active material layer 22, for example, is provided on the first surface 21 a of the current collector 21 via an adhesive layer. For example, the adhesive layer may be formed of an adhesive such as acetylene black. The adhesive layer, for example, may be provided on the entire first surface 21 a of the current collector 21. Furthermore, the edge of the adhesive layer may be formed along the edge of the negative electrode active material layer 23 that surrounds the positive electrode active material layer 22, as viewed from the stacking direction.

[0023] The positive electrode active material layer 22 is a layered member containing a positive electrode active material, a conductive additive, and a binder. Examples of the positive electrode active material include a composite oxide, metallic lithium, and sulfur. The composition of the composite oxide includes, for example, at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. Examples of the composite oxide include olivine-type lithium iron phosphate (LiFePO ４ ), LiCoO ２ , LiNiMnCoO ２ etc.

[0024] The binder serves to anchor the active material or conductive additive to the surface of the current collector 21 and maintain the conductive network within the electrode. 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 containing monomer units such as acrylic acid and methacrylic acid; styrene-butadiene rubber (SBR); carboxymethyl cellulose; alginates such as sodium alginate and ammonium alginate; water-soluble cellulose ester crosslinks; and starch-acrylic acid graft polymers. These binders can be used alone or in combination. Examples of conductive additives include acetylene black, carbon black, and graphite. The positive electrode active material layer 22 may contain a viscosity-adjusting solvent such as N-methyl-2-pyrrolidone (NMP).

[0025] The negative electrode active material layer 23 is provided on the second surface 21b of the current collector 21. The current collector 21 and the negative electrode active material layer 23 provided on the second surface 21b of the current collector 21 constitute the negative electrode of the bipolar electrode 14. The negative electrode active material layer 23 is formed in a rectangular shape at the center of the second surface 21b so that the peripheral edge portion 21c of the current collector 21 is exposed. In one example, the positive electrode active material layer 22 is contained within the region of the negative electrode active material layer 23 when viewed from the stacking direction. In other words, the outer edge of the positive electrode active material layer 22 is slightly smaller than the outer edge of the negative electrode active material layer 23.

[0026] The negative electrode active material layer 23 is a layered member containing a negative electrode active material, a conductive additive, and a binder. Examples of the negative electrode active material include graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, soft carbon, and other carbon, metal compounds, elements or compounds of such elements that can be alloyed with lithium, and boron-doped carbon. Examples of elements that can be alloyed with lithium include silicon and tin. The conductive additive and binder may be the same as those used in the positive electrode active material layer 22.

[0027] To form the positive electrode active material layer 22 and the negative electrode active material layer 23 on the current collector 21, a conventionally known method such as roll coating, die coating, dip coating, doctor blade coating, spray coating, or curtain coating is used. Specifically, an active material, a solvent, and, if necessary, a binder and a conductive additive are mixed to produce a slurry-like active material layer-forming composition, which is then applied to the first surface 21a and the second surface 21b and dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. The dried electrode may be compressed to increase electrode density.

[0028] In the electrode stack 12, adjacent bipolar electrodes 14, 14 in the stacking direction are arranged so that the positive electrode active material layer 22 of one bipolar electrode 14 faces the negative electrode active material layer 23 of the other bipolar electrode 14. A separator 15 is arranged between adjacent bipolar electrodes 14, 14 in the stacking direction. In this embodiment, the separator 15 is a sheet-like member having a rectangular shape in a plan view, and prevents short circuits between adjacent bipolar electrodes 14, 14 in the stacking direction.

[0029] The separator 15 has a rectangular shape that is larger than the positive electrode active material layer 22 and the negative electrode active material layer 23 when viewed from the stacking direction, and smaller than the current collector 21. When viewed from the stacking direction, the end 15 a of the separator 15 is located outside the positive electrode active material layer 22 and the negative electrode active material layer 23. In other words, when viewed from the stacking direction, the end 15 a of the separator 15 does not overlap with either the positive electrode active material layer 22 or the negative electrode active material layer 23.

[0030] The separator 15 is formed, for example, in a sheet shape. The separator 15 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains an electrolyte. Examples of materials constituting the separator 15 include polyolefins such as polypropylene and polyethylene, and polyesters. The separator 15 may have a single-layer structure or a multi-layer structure. In the case of a multi-layer structure, the separator 15 may include, for example, a substrate layer and a pair of adhesive layers, and may be bonded and fixed to the positive electrode active material layer 22 and the negative electrode active material layer 23 by the pair of adhesive layers. The separator 15 may also include a ceramic layer that serves as a heat-resistant layer. The separator 15 may be reinforced with a vinylidene fluoride resin compound.

[0031] The separator 15 is formed by stretching a molten resin using a dry process or a wet process. In this case, the separator 15 has a direction in which it shrinks more and a direction in which it shrinks less, depending on the stretching process. The separator 15 may have a rectangular shape with the direction in which it shrinks more along its short sides and the direction in which it shrinks less along its long sides. In one example, the separator 15 is formed by a wet process, and the TD (Transverse Direction) direction in which it shrinks more is along its short sides, and the MD (Machine Direction) direction in which it shrinks less is along its long sides.

[0032] Examples of the electrolyte impregnated into the separator 15 include a liquid electrolyte (electrolytic solution) containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent, and a polymer gel electrolyte containing an electrolyte held in a polymer matrix. When the separator 15 is impregnated with an electrolyte, the electrolyte salt may be LiClO. ４ , LiAsF ６ , LiPF ６ , LiBF ４ , LiCF ３ SO ３ , LiN(FSO ２ ) ２ , LiFSi, LiN(CF ３ SO ２ ) ２Known lithium salts such as those listed above can be used. Furthermore, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers can be used as the non-aqueous solvent. These known solvent materials may be used in combination of two or more.

[0033] The positive terminal electrode 16 is composed of a current collector 21 and a positive electrode active material layer 22 provided on a first surface 21a of the current collector 21. The positive terminal electrode 16 is arranged at one end of the electrode laminate 12 in the stacking direction so that the positive electrode active material layer 22 on the first surface 21a faces the negative electrode active material layer 23 of the terminal bipolar electrode 14. In the positive terminal electrode 16, the second surface 21b of the current collector 21 is not provided with the positive electrode active material layer 22 or the negative electrode active material layer 23, and the second surface 21b is electrically connected to an adjacent conductive plate (not shown). The current collector 21 used in the positive terminal electrode 16 may be made of aluminum foil.

[0034] The negative terminal electrode 17 is composed of a current collector 21 and a negative electrode active material layer 23 provided on a second surface 21b of the current collector 21. The negative terminal electrode 17 is arranged on the other end side of the electrode laminate 12 in the stacking direction, so that the negative electrode active material layer 23 on the second surface 21b faces the positive electrode active material layer 22 of the terminal bipolar electrode 14. In the negative terminal electrode 17, the first surface 21a of the current collector 21 is not provided with the positive electrode active material layer 22 or the negative electrode active material layer 23, and the first surface 21a is electrically connected to an adjacent conductive plate (not shown). The current collector 21 used in the negative terminal electrode 17 may be made of copper foil or may be a composite material including a copper layer.

[0035] In each of the pair of terminal electrodes, the current collector 21 has an inner surface facing the bipolar electrode 14 and an outer surface facing the opposite side to the inner surface. That is, in the positive terminal electrode 16, the inner surface of the current collector 21 is the first surface 21a, and the outer surface of the current collector 21 is the second surface 21b. On the other hand, in the negative terminal electrode 17, the inner surface of the current collector 21 is the second surface 21b, and the outer surface of the current collector 21 is the first surface 21a.

[0036] The separators 15 are disposed between the bipolar electrodes 14, 14 adjacent to each other in the stacking direction, as well as between the bipolar electrode 14 and the positive terminal electrode 16, and between the bipolar electrode 14 and the negative terminal electrode 17. The separators 15 are disposed to prevent short circuits between the bipolar electrode 14 and the positive terminal electrode 16, and between the bipolar electrode 14 and the negative terminal electrode 17.

[0037] The sealing portion 13 is a member that seals an electrolyte solution (not shown) containing an electrolyte in an internal space S between adjacent current collectors 21, 21 in the stacking direction. The sealing portion 13 has electrical insulation properties. The sealing portion 13 is provided on a peripheral portion 21 c of the current collector 21 so as to surround the electrode stack 12 when viewed from the stacking direction. The sealing portion 13 is bonded (joined) to the peripheral portion of the current collector 21. When viewed from the stacking direction, the sealing portion 13 is spaced apart from the positive electrode active material layer 22 and the negative electrode active material layer 23. When viewed from the stacking direction, the sealing portion 13 has a frame shape and is disposed between adjacent current collectors 21, 21 in the stacking direction so as to surround the peripheries of the positive electrode active material layer 22 and the negative electrode active material layer 23. In the electricity storage module 11, an internal space S is defined by the sealing portion 13 and the adjacent current collectors 21, 21 in the stacking direction. An electrolyte solution (not shown) containing an electrolyte is accommodated in the internal space S. The sealing portion 13 is disposed between the current collectors 21, 21 adjacent to each other in the stacking direction, and therefore also functions as a spacer that maintains the distance between the adjacent current collectors 21, 21.

[0038] An example sealing portion 13 includes multiple sealing layers 30, multiple spacer layers 33, end surface welds 34, and multiple outer edge welds 36. The multiple sealing layers 30 and the multiple spacer layers 33 each have a rectangular frame shape when viewed in the stacking direction. The sealing layers 30 and the spacer layers 33 may be formed into a rectangular frame shape by punching or cutting a long sheet material unwound from a raw roll. The sealing layers 30 and the spacer layers 33 may also be formed into a rectangular frame shape by connecting multiple sheet materials formed into a rectangular, L-shaped, U-shaped, or other shape.

[0039] The thickness of the sealing layer 30 (the length in the stacking direction) may be, for example, 100 μm or more and 200 μm or less. The thicknesses of the multiple sealing layers 30 may be the same. The thickness of the sealing layer 30 bonded to the first surface 21 a of the current collector 21 may be different from the thickness of the sealing layer 30 bonded to the second surface 21 b.

[0040] Each of the multiple sealing layers 30 is provided on the peripheral portion 21c of the current collector 21 so as to protrude beyond the outer edge 21d of the current collector 21. Each of the multiple sealing layers 30 has a first region R1 welded to the peripheral portion 21c of the current collector 21 and a second region R2 protruding beyond the outer edge 21d of the current collector 21. In this embodiment, the outer edge 21d of the current collector 21 is formed by an end face of the current collector 21. The multiple sealing layers 30 are bonded to each of the first surface 21a and the second surface 21b of the peripheral portion 21c of the current collector 21. In one example, when viewed in the stacking direction, the outer edge 30b of the sealing layer 30 is larger than the outer edge 21d of the current collector 21 and surrounds the current collector 21. Furthermore, when viewed from the stacking direction, the outer edge 21d of the current collector 21 is larger than the inner edge 30a of the seal layer 30 and surrounds the inner edge 30a of the seal layer 30. The seal layer 30 and the current collector 21 are joined to each other in an overlapping region when viewed from the stacking direction. That is, the seal layer 30 and the current collector 21 are joined to each other in a region from the inner edge 30a of the seal layer 30 to the outer edge 21d of the current collector 21. When viewed from the stacking direction, the inner edge 30a of the seal layer 30 is spaced from the positive electrode active material layer 22 and the negative electrode active material layer 23.

[0041] The multiple sealing layers 30 include a pair of first sealing layers 31 and second sealing layers 32. The pair of first sealing layers 31 are sealing layers 30 provided on the outer surfaces of the current collectors 21 of the pair of terminal electrodes. That is, one first sealing layer 31 is adhered to the second surface 21b of the positive terminal electrode 16, and the other first sealing layer 31 is adhered to the first surface 21a of the negative terminal electrode 17. The pair of first sealing layers 31 are outermost sealing layers of the multiple sealing layers 30 that are arranged at the stacking ends. The second sealing layer 32 is a sealing layer 30 other than the pair of first sealing layers 31, and is arranged between the pair of first sealing layers 31. The second sealing layer 32 is provided on the inner surfaces of the current collectors 21 of the pair of terminal electrodes (i.e., the first surface 21a of the current collector 21 of the positive terminal electrode 16 and the second surface 21b of the current collector 21 of the negative terminal electrode 17), and on the first surface 21a and the second surface 21b of the current collector 21 of the bipolar electrode 14.

[0042] The first sealing layer 31 has a multilayer structure. The first sealing layer 31 includes a first resin layer 41, a gas barrier resin layer 42, and a second resin layer 43. The first resin layer 41 is welded to the outer surfaces of the current collectors 21 of a pair of terminal electrodes (i.e., the second surface 21b of the positive terminal electrode 16 and the first surface 21a of the negative terminal electrode 17). The gas barrier resin layer 42 is provided on the first resin layer 41. The second resin layer 43 is provided on the gas barrier resin layer 42 so as to sandwich the gas barrier resin layer 42 between the first resin layer 41 and the second resin layer 43. The second resin layer 43 is provided on the gas barrier resin layer 42 so as to sandwich the gas barrier resin layer 42 between the first resin layer 41 and the second resin layer 43. The first resin layer 41 ensures adhesion between the first sealing layer 31 and the current collector 21 and prevents the first sealing layer 31 from peeling off from the current collector 21. The second resin layer 43 covers the gas barrier resin layer 42 and protects the gas barrier resin layer 42 from damage due to contact with external members.

[0043] The first resin layer 41 and the second resin layer 43 are made of, for example, the same resin material. The first resin layer 41 and the second resin layer 43 are made of a polyolefin or modified polyolefin, such as an electrolyte-resistant resin material such as acid-modified polyethylene (acid-modified PE), acid-modified polypropylene (acid-modified PP), polyethylene, or polypropylene. The resin materials making up the first resin layer 41 and the second resin layer 43 may be different from each other.

[0044] The gas barrier resin layer 42 is welded to the first resin layer 41 and the second resin layer 43 so as to overlap the second region R2 as viewed from the stacking direction. The gas barrier resin layer 42 is provided at least from the outer edge welded portion 36 to the end surface welded portion 34 as viewed from the stacking direction. The gas barrier resin layer 42 covers at least the region between the outer edge welded portion 36 and the end surface welded portion 34 as viewed from the stacking direction. The gas barrier resin layer 42 is provided at least between the outer edge welded portion 36 and the end surface welded portion 34 as viewed from the stacking direction. The gas barrier resin layer 42 has a lower gas permeability than the first resin layer 41 and the second resin layer 43. The gas barrier resin layer 42 is made of a resin material containing vinyl alcohol as a monomer. The gas barrier resin layer 42 is made of, for example, ethylene-vinyl alcohol copolymer (EVOH) resin or polyvinyl alcohol (PVA) resin. The first resin layer 41, the gas barrier resin layer 42, and the second resin layer 43 may have the same thickness or different thicknesses.

[0045] In this embodiment, the second sealing layer 32 (third resin layer) has a single-layer structure and is composed of a single resin layer. The second sealing layer 32 is welded to the inner surfaces of the current collectors 21 of the pair of terminal electrodes (i.e., the first surface 21a of the current collector 21 of the positive terminal electrode 16 and the second surface 21b of the current collector 21 of the negative terminal electrode 17) and the first surface 21a and the second surface 21b of the current collector 21 of the bipolar electrode 14. The second sealing layer 32 is composed of a polyolefin resin or a modified polyolefin resin, such as an electrolyte-resistant resin material such as acid-modified PE, acid-modified PP, polyethylene, or polypropylene. The second sealing layer 32 is composed of, for example, the same resin material as the first resin layer 41.

[0046] The spacer layer 33 is provided between two sealing layers 30, 30 adjacent to each other in the stacking direction. An inner edge 33a of the spacer layer 33 is located in an internal space S formed between current collectors 21, 21 adjacent to each other in the stacking direction. An outer edge 33b of the spacer layer 33 may be located at the same position as the outer edge 30b of the sealing layer 30 when viewed from the stacking direction. The thickness (length in the stacking direction) of the spacer layer 33 may be thicker than the thickness (length in the stacking direction) of the sealing layer 30, and may be, for example, 200 μm or more and 500 μm or less.

[0047] The spacer layer 33 is made of a polyolefin resin or a modified polyolefin resin, such as an electrolyte-resistant resin material such as acid-modified PE, acid-modified PP, polyethylene, or polypropylene. The spacer layer 33 has higher crystallinity than the first resin layer 41, the second resin layer 43, and the second seal layer 32. This can suppress moisture permeation through the sealing portion 13.

[0048] In this embodiment, the first resin layer 41, the second resin layer 43, and the second seal layer 32 are made of acid-modified PE or acid-modified PP, the gas barrier resin layer 42 is made of EVOH resin, and the spacer layer 33 is made of polyethylene or polypropylene.

[0049] The end surface welds 34 are formed by welding and integrating the outer edges of the plurality of seal layers 30 and the outer edges of the plurality of spacer layers 33 to each other outside the outer edge 21d of the current collector 21 as viewed from the stacking direction. The end surface welds 34 are formed by welding and integrating the outer edges of the plurality of seal layers 30 and the outer edges of the plurality of spacer layers 33 to each other at least on the end surface R2a of the second region R2 as viewed from the stacking direction. The plurality of seal layers 30 and the plurality of spacer layers 33 are welded to each other by the end surface welds 34 outside the outer edge 21d of the current collector 21. The end surface welds 34 are formed by welding and integrating the ends (outer edges) of the plurality of seal layers 30 and the plurality of spacer layers 33 on the opposite side to the internal space S. In other words, the seal layer 30 and the spacer layer 33 are not welded to each other except at the end surface welds 34 and are only in contact with each other.

[0050] The end surface welded portion 34 has a rectangular frame shape when viewed from the stacking direction and surrounds the electrode stack 12. When viewed from the stacking direction, the end surface welded portion 34 is formed outside the outer edge 21d of the current collector 21. That is, the seal layer 30 and the spacer layer 33 have an overlapping portion that overlaps with the current collector 21 when viewed from the stacking direction, and an extending portion that extends outside the outer edge 21d of the current collector 21. The end surface welded portion 34 is provided in the extending portion.

[0051] The side of the end weld 34 opposite the internal space S extends along the stacking direction and constitutes the outer surface of the sealing portion 13. In other words, the sealing portion 13 includes an inner surface facing the internal space S and an outer surface opposite the inner surface. The sealing portion 13 has four outer surfaces. The thickness of the end weld 34, i.e., the distance (shortest distance) between the inner surface and the outer surface of the end weld 34, is, for example, 1 mm or more and 5 mm or less. The thickness of the end weld 34 may be 1 mm or more and 3 mm or less. The thickness of the end weld 34 is, for example, 10 times or more the thickness of the seal layer 30. The end weld 34 is formed, for example, by melting the outer edge of the seal layer 30 and the outer edge of the spacer layer 33 using a heating device such as an infrared heater. The thickness of the end face welded portion 34 is thicker than the first seal layer 31, which is the outermost seal layer, so the end face welded portion 34 is unlikely to become a permeation path for gas or moisture.

[0052] The outer edge welded portion 36 is provided so as to cover the outer edge 21 d of the current collector 21. The outer edge welded portion 36 provided on the terminal electrode is formed by welding adjacent first resin layers 41 and second seal layers 32 together to cover the outer edge 21 d of the current collector 21 of the terminal electrode. The outer edge welded portion 36 provided on the bipolar electrode 14 is formed by welding adjacent first resin layers 41, 41 together to cover the outer edge 21 d of the current collector 21 of the bipolar electrode 14. When viewed in the stacking direction, the outer edge welded portion 36 is located inside the end surface welded portion 34, spaced apart from the end surface welded portion 34.

[0053] When viewed from the stacking direction, the outer edge welded portion 36 is located outside the outer edge 21 d. The outer edge welded portion 36 may or may not be in contact with the outer edge 21 d. When viewed from the stacking direction, the outer edge welded portion 36 has a rectangular frame shape that surrounds the electrode stack 12.

[0054] FIG. 4 is a cross-sectional view illustrating a method for forming an outer edge weld portion. As shown in FIG. 4 , a pair of sealing layers 30 and the current collector 21 are arranged so that the peripheral edge portion 21c of the current collector 21 is sandwiched between the pair of sealing layers 30. Here, an example is shown in which the current collector 21 is arranged between the first resin layer 41 and the second seal layer 32 of the first seal layer 31. The pair of sealing layers 30 are then heated using a heating device such as an impulse sealer or ultrasonic sealer to adhere to the peripheral edge portion 21c of the current collector 21. At this time, the first resin layer 41 and the second seal layer 32 are fused and integrated with each other outside the outer edge 21d of the current collector 21, forming an outer edge weld portion 36. The outer edge 21d of the current collector 21 can be covered by the outer edge weld portion 36.

[0055] Although not shown in the drawings, the outer edge welded portion 36 is formed in a similar manner when the current collector 21 is disposed between two second seal layers 32. As an example, the heating region R by the heating device is limited to the region of the seal layer 30 that overlaps with the current collector 21 and the vicinity thereof. This limits the thickness of the outer edge welded portion 36, thereby making it possible to suppress warping of the current collector 21.

[0056] The sealing portion 13 shown in FIGS. 1 to 3 has communication holes 35 that communicate with each of the multiple internal spaces S. As an example, the communication holes 35 are formed by partially cutting out the spacer layer 33 and penetrate the spacer layer 33 and the end surface welded portion 34. The communication holes 35 have one opening in the internal space S and the other opening on the outer surface of the sealing portion 13. In the energy storage module 11, cells including one internal space S are formed between adjacent current collectors 21. Here, one communication hole 35 is formed for one cell. The communication holes 35 can be used as liquid filling ports for filling the internal spaces S with electrolyte. That is, a liquid filling port (opening of the communication hole 35) is provided on the outer surface of the sealing portion 13. In the energy storage module 11 that is rectangular when viewed in the stacking direction, the side on which the communication holes 35 are provided is referred to as the liquid filling port side.

[0057] When viewed from the stacking direction, the inner edge 33a of the spacer layer 33 around the liquid inlet is located inside (toward the internal space S) than the inner edge 30a of the seal layer 30. In this embodiment, the inner edge 33a of the spacer layer 33 around the liquid inlet is located, for example, 1 mm or more inside the inner edge 30a and is exposed from the seal layer 30 so as to face the internal space S. When viewed from the stacking direction, the inner edge 33a of the spacer layer 33 around the liquid inlet other than the liquid inlet may be located outside the inner edge 30a of the seal layer 30 or inside the inner edge 30a of the seal layer 30.

[0058] The end 15a of the separator 15 is fixed to the seal layer 30 between the seal layer 30 adhered to the second surface 21b of the current collector 21 and the spacer layer 33. It is sufficient that the end 15a of the separator 15 is fixed near the inner edge 30a of the seal layer 30 when viewed from the stacking direction. The end 15a may be partially adhered (welded) to the seal layer 30 by, for example, spot welding.

[0059] When viewed from the stacking direction, the sealing layer 30 is spaced apart from the positive electrode active material layer 22 and the negative electrode active material layer 23. When viewed from the stacking direction, the inner edge 30a is located outside the positive electrode active material layer 22 and the negative electrode active material layer 23. When viewed from the stacking direction, the sealing layer 30 adhered to the first surface 21a may overlap with the negative electrode active material layer 23, as long as it is spaced apart from the positive electrode active material layer 22.

[0060] As described above, the energy storage module 11 includes the electrode stack 12 and the resin sealing portion 13. The sealing portion 13 has multiple seal layers 30 provided on the peripheral portion 21 c of the current collector 21, a spacer layer 33 provided between adjacent seal layers 30 in the stacking direction, and an end surface welded portion 34 where the outer edges of the multiple seal layers 30 and the outer edges of the spacer layer 33 are integrated with each other by welding. The sealing portion 13 seals the internal space S of the energy storage module 11.

[0061] Gases with small molecular diameters pass through gaps between molecular bonds in the resin and travel back and forth through the sealing portion 13. In the sealing portion 13, for example, the thickness of the end face welded portion 34 as viewed from the stacking direction is 1 mm to 5 mm, whereas the thickness in the stacking direction of the outermost sealing layer (first sealing layer 31) disposed at the end of the stack is thin, at 100 μm to 200 μm. Therefore, there is a risk that air may enter the internal space S or the electrolyte in the internal space S may escape through the first sealing layer 31.

[0062] When manufacturing the energy storage module 11, an electrolyte solution is injected into the internal space S through the communication holes 35 at room temperature (20 to 25°C), and after temporary sealing, an activation process is performed. Next, the energy storage module 11 is subjected to an aging process, and then it is vacuum-sealed. Finally, the entire energy storage module 11 is laminate-packed with aluminum, which suppresses gas permeation. However, as the energy storage module 11 becomes larger, the first sealing layer 31, which serves as a gas permeation path, also becomes larger, and there is a risk that the amount of gas permeation that occurs before the laminate packing is applied will become significant. In particular, the aging process is performed at a high temperature of 60°C for a long period of time, such as 80 hours, and therefore the amount of gas permeation is likely to increase.

[0063] In the energy storage module 11, the first sealing layer 31 includes a first resin layer 41 bonded to the current collector 21, a gas barrier resin layer 42 provided on the first resin layer 41, and a second resin layer 43 provided on the gas barrier resin layer 42. The gas barrier resin layer 42 is welded to the first resin layer 41 and the second resin layer 43, and has a lower gas permeability than the first resin layer 41 and the second resin layer 43. The gas barrier resin layer 42 can suppress gas permeation through the sealing portion 13, thereby suppressing a decrease in battery performance.

[0064] It is also possible to suppress gas permeation by using a metal foil such as aluminum in the first sealing layer 31 instead of the gas barrier resin layer 42. However, because metals have high thermal conductivity, if the first sealing layer 31 contains a metal foil, heat may not be sufficiently transferred to the resin portion when forming the edge weld portion 34, and the resin portions may not be integrated. In this case, the sealing performance of the sealing portion 13 may be reduced. In contrast, the gas barrier resin layer 42 is made of a resin material and has a lower specific heat than metal foil such as aluminum, making it less likely to cause poor formation of the edge weld portion 34. This prevents a reduction in the sealing performance of the sealing portion 13. Furthermore, compared to metal foil such as aluminum, the gas barrier resin layer 42 has a larger number of surface functional groups that contribute to welding between the first resin layer 41 and the second resin layer 43, making it less likely to undergo delamination than when using metal foil.

[0065] The gas barrier resin layer 42 is made of a resin material containing vinyl alcohol as a monomer. Resin materials containing vinyl alcohol as a monomer are capable of compact aggregation between molecules, and are materials with high barrier properties due to the formation of hydrogen bonds between hydrogen groups. Resin materials containing vinyl alcohol as a monomer have low gas permeability, so they can reliably suppress gas permeation.

[0066] The first resin layer 41 and the second resin layer 43 are made of the same resin material. Using a common resin material can facilitate the manufacture of the first sealing layer 31. The first sealing layer 31 has the same configuration even when inverted in the thickness direction, so the first sealing layer 31 can be used without distinguishing between the front and back. This further facilitates the manufacture of the energy storage module 11.

[0067] The second sealing layer 32 (third resin layer) bonded to the inner surface of the current collector 21 of the terminal electrode (i.e., the first surface 21a of the current collector 21 of the positive terminal electrode 16 and the second surface 21b of the current collector 21 of the negative terminal electrode 17) is made of the same resin material as the first resin layer 41. Using a common resin material can facilitate the manufacture of the first sealing layer 31 and the second sealing layer 32.

[0068] The sealing portion 13 has an outer edge weld portion 36 in which the first resin layer 41 and the second seal layer 32 are integrated by welding to cover the outer edge 21d of the current collector 21. The outer edge weld portion 36 prevents the first resin layer 41 and the second seal layer 32 from peeling off from the current collector 21. Because the first resin layer 41 and the second seal layer 32 are made of the same resin material, they are easily compatible with each other. This makes it easy to form the outer edge weld portion 36.

[0069] When viewed from the stacking direction, the outer edge welded portion 36 is disposed at a distance from the end surface welded portion 34. The first seal layer 31 and the second seal layer 32 are not welded to each other between the outer edge welded portion 36 and the end surface welded portion 34. As such, the first seal layer 31 and the second seal layer 32 have portions that are not welded to each other, so warping of the current collector 21 can be suppressed.

[0070] Second Embodiment FIG. 5 is an enlarged cross-sectional view of a portion of an energy storage module according to a second embodiment. The energy storage module 11A according to the second embodiment shown in FIG. 5 differs from the energy storage module 11 in that the second sealing layer 32 has a multilayer structure. The second sealing layer 32 includes a third resin layer 44, a core resin layer 45, and a fourth resin layer 46. The third resin layer 44 is bonded to the inner surfaces of the current collectors 21 of a pair of termination electrodes (i.e., the first surface 21a of the current collector 21 of the positive termination electrode 16 and the second surface 21b of the current collector 21 of the negative termination electrode 17) and the first surface 21a and the second surface 21b of the current collector 21 of the bipolar electrode 14. The core resin layer 45 is provided on the third resin layer 44. The fourth resin layer 46 is provided on the core resin layer 45 so as to sandwich the core resin layer 45 between the third resin layer 44 and the fourth resin layer 46. The fourth resin layer 46 is in contact with the spacer layer 33. The third resin layer 44 and the fourth resin layer 46 ensure adhesion between the second seal layer 32 and the current collector 21, and prevent the second seal layer 32 from peeling off from the current collector 21.

[0071] The third resin layer 44 and the fourth resin layer 46 may be made of, for example, the same resin material. The third resin layer 44 and the fourth resin layer 46 may be made of the same resin material as the second seal layer 32 of the energy storage module 11. The third resin layer 44 and the fourth resin layer 46 are made of a polyolefin resin or a modified polyolefin resin, such as an electrolyte-resistant resin material such as acid-modified PE, acid-modified PP, polyethylene, or polypropylene. The resin materials making up the third resin layer 44 and the fourth resin layer 46 may be different from each other. The first resin layer 41, the second resin layer 43, the third resin layer 44, and the fourth resin layer 46 may be made of, for example, the same resin material.

[0072] The core resin layer 45 is welded to the third resin layer 44 and the fourth resin layer 46. The core resin layer 45 is made of a polyolefin resin or a modified polyolefin resin, such as an electrolyte-resistant resin material such as acid-modified PE, acid-modified PP, polyethylene, or polypropylene. The core resin layer 45 has higher crystallinity than the third resin layer 44 and the fourth resin layer 46. The core resin layer 45 is made of, for example, the same material as the spacer layer 33.

[0073] In this embodiment, the first resin layer 41, the second resin layer 43, the third resin layer 44, and the fourth resin layer 46 are made of acid-modified PE or acid-modified PP. The gas barrier resin layer 42 is made of EVOH resin. The spacer layer 33 and the core resin layer 45 are made of polyethylene or polypropylene.

[0074] In the energy storage module 11A, the first sealing layer 31 includes a gas barrier resin layer 42, thereby suppressing gas permeation through the sealing portion 13, similar to the energy storage module 11. In the energy storage module 11A, the second sealing layer 32 includes a third resin layer 44 made of the same resin material as the first resin layer 41 and bonded to the inner surfaces of the termination electrodes (i.e., the first surface 21a of the current collector 21 of the positive termination electrode 16 and the second surface 21b of the current collector 21 of the negative termination electrode 17). The outer edge weld portion 36 is formed by integrating the first resin layer 41 of the first sealing layer 31 and the third resin layer 44 of the second sealing layer 32 through welding. Because the first resin layer 41 and the third resin layer 44 are made of the same resin material, they are easily compatible with each other. This facilitates the formation of the outer edge weld portion 36. The second sealing layer 32 includes a core resin layer 45 having higher crystallinity than the first resin layer 41. The core resin layer 45, together with the spacer layer 33, suppresses moisture permeation through the sealing portion 13 and improves the gas barrier properties.

[0075] Third Embodiment Fig. 6 is an enlarged cross-sectional view showing a portion of an energy storage module according to a third embodiment. In an energy storage module 11B according to the third embodiment shown in Fig. 6, the gas barrier resin layer 42 is thicker than the first resin layer 41 and the second resin layer 43. The thickness of the gas barrier resin layer 42 may be 50% or more, 60% or more, or 70% or more of the total thickness of the seal layer 30.

[0076] In the energy storage module 11B, the gas barrier resin layer 42 is thick, so that in an airtightness test between the cells and the outside that is performed during manufacturing, the test gas injected into the internal space S through the communication holes 35 is prevented from permeating the first seal layer 31 and leaking to the outside. In addition to helium, the test gas may be, for example, a rare gas such as argon, an inert gas such as nitrogen, or hydrogen, ammonia, or a halogen gas. In the airtightness test, a detection sensor disposed outside the energy storage module 11B detects whether or not the test gas is leaking. If the detection sensor does not detect the test gas, it is determined that there is no problem with the airtightness between the cells and the outside.

[0077] As described above, in the sealing portion 13, the thickness of the first sealing layer 31, which is the outermost sealing layer, is thinner than the thickness of the end face welded portion 34, and therefore there is a risk that the test gas may leak from the internal space S through the first sealing layer 31. In the energy storage module 11B, the gas barrier resin layer 42 suppresses the permeation of the test gas, and therefore it is possible to reliably detect any problem with the airtightness between the cell and the outside, i.e., any leakage of the test gas through the end face welded portion 34.

[0078] EVOH resin, which is an example of a resin used in the gas barrier resin layer 42, has higher resin strength than acid-modified PE, which is an example of a resin used in the first resin layer 41 and the second resin layer 43. This can improve the pressure resistance strength of the energy storage module 11B.

[0079] The gas barrier resin layer 42 is, for example, an EVOH resin with an ethylene ratio of 30% or less. An example of the gas barrier resin layer 42 is an EVOH resin with an ethylene ratio of 27%. By reducing the ethylene ratio in this way, it is possible to more reliably reduce the permeability of the test gas used in the airtightness test.

[0080] The first resin layer 41 and the second resin layer 43 have, for example, the same thickness. The thickness of the first resin layer 41 and the second resin layer 43 is, for example, 20 μm or more. This ensures adhesion. An example thickness of the first resin layer 41 and the second resin layer 43 is 30 μm.

[0081] FIG. 7 is a plan view showing a first sealing layer according to a modified example. As shown in FIG. 7, the first sealing layer 31A according to the modified example is formed by connecting multiple sheet materials 60. In the illustrated example, four rectangular sheet materials 60 are connected to form the first sealing layer 31A. The first sealing layer 31A includes a connecting portion 61 where two sheet materials 60 are overlapped and connected. In the connecting portion 61, at least a portion of the end portions of the two sheet materials 60 are arranged overlapping each other. At least in the connecting portion 61, the first resin layer 41 and the second resin layer 43 (see FIG. 3) are made of a polyolefin resin or a modified polyolefin resin. This makes it easier for the sheet materials 60 to be welded together at the connecting portion 61.

[0082] Although an example embodiment of the present disclosure has been described in detail above, the present disclosure is not limited to the above embodiment and modifications.

[0083] For example, it is sufficient that at least one first sealing layer 31 includes the gas barrier resin layer 42, and the other first sealing layer 31 may have the same configuration as the second sealing layer 32. The above embodiments and modifications may be combined as appropriate.

[0084] The form of the present disclosure can be shown as follows. [1] A laminate including a plurality of electrodes stacked together, each having a current collector; and a resin sealing portion provided on a peripheral edge of the current collector so as to surround the laminate when viewed from a stacking direction of the plurality of electrodes, wherein the plurality of electrodes include a pair of terminal electrodes and a bipolar electrode disposed between the pair of terminal electrodes in the stacking direction, wherein the current collector of each of the pair of terminal electrodes has an inner surface facing the bipolar electrode and an outer surface facing the opposite side to the inner surface, and the sealing portion includes a plurality of sealing layers each having a first region welded to a peripheral edge of the current collector and a second region protruding from an outer edge of the current collector, and a spacer layer provided between the sealing layers adjacent to each other in the stacking direction, wherein the plurality of sealing layers include a first sealing layer provided on the outer surface, and the first sealing layer includes: a first resin layer welded to the outer surface; and a gas barrier resin layer provided on the first resin layer and having a lower gas permeability than the first resin layer. and a second resin layer provided on the gas barrier resin layer and sandwiching the gas barrier resin layer between itself and the first resin layer, wherein at least on an end face of the second region as viewed from the stacking direction, outer edge portions of the plurality of seal layers including the pair of first seal layers and an outer edge portion of the spacer layer are welded together to form an end face welded portion, and the gas barrier resin layer is provided so as to overlap at least the second region as viewed from the stacking direction. [2] The energy storage module according to [1], wherein the gas barrier resin layer is made of a resin material containing vinyl alcohol as a monomer. [3] The energy storage module according to [1] or [2], wherein the first seal layer is formed by connecting a plurality of sheet materials and includes a connecting portion where the first resin layer and the second resin layer of two of the sheet materials are overlapped and welded to each other, and the first resin layer and the second resin layer at the connecting portion are made of a polyolefin resin.[4] The energy storage module according to any one of [1] to [3], wherein the first resin layer is a polyolefin resin, the plurality of sealing layers further include a second sealing layer provided on the inner surface, the second sealing layer including a third resin layer made of polyolefin resin and welded to the inner surface, and the sealing portion further includes an outer edge weld portion where the first resin layer and the third resin layer are integrated with each other by welding so as to cover an outer edge of the current collector. [5] The energy storage module according to [4], wherein, as viewed from the stacking direction, the outer edge weld portion is disposed apart from the end face weld portion, and the gas barrier resin layer is provided at least between the outer edge weld portion and the end face weld portion as viewed from the stacking direction. [6] The energy storage module according to [4] or [5], wherein the second sealing layer further includes a core resin layer provided on the third resin layer and having higher crystallinity than the third resin layer.

[0085] 11, 11A, 11B... Energy storage module, 12... Electrode laminate (laminate), 13... Sealing portion, 14... Bipolar electrode, 16... Positive electrode terminal electrode, 17... Negative electrode terminal electrode, 21... Current collector, 21a... First surface, 21b... Second surface, 21c... Peripheral portion, 21d... Outer edge, 22... Positive electrode active material layer, 23... Negative electrode active material layer, 30... Seal layer, 31, 31A... First seal layer, 32...second seal layer (third resin layer), 33...spacer layer, 34...end face welded portion, 36...outer edge welded portion, 41...first resin layer, 42...gas barrier resin layer, 43...second resin layer, 44...third resin layer, 45...core resin layer, 46...fourth resin layer, 60...sheet material, 61...connecting portion, S...internal space, R1...first region, R2...second region, R2a...end face.

Claims

1. A laminate comprising a plurality of electrodes each having a current collector, and a resin sealing portion provided on a peripheral portion of the current collector so as to surround the laminate when viewed from a stacking direction of the plurality of electrodes, the plurality of electrodes including a pair of terminal electrodes and a bipolar electrode disposed between the pair of terminal electrodes in the stacking direction, the current collector of each of the pair of terminal electrodes having an inner surface facing the bipolar electrode and an outer surface facing the opposite side to the inner surface, the sealing portion including a plurality of sealing layers each having a first region welded to a peripheral portion of the current collector and a second region protruding from an outer edge of the current collector, and a spacer layer provided between the sealing layers adjacent to each other in the stacking direction, the plurality of sealing layers including a first sealing layer provided on the outer surface, the first sealing layer including: a first resin layer welded to the outer surface; and a gas barrier resin layer provided on the first resin layer and having a lower gas permeability than the first resin layer. a second resin layer provided on the gas barrier resin layer and sandwiching the gas barrier resin layer between the first resin layer and the second resin layer, wherein at least on an end face of the second region as viewed from the stacking direction, outer edges of the plurality of seal layers including a pair of the first seal layers and an outer edge of the spacer layer are integrated with each other by welding to form an end face welded portion, and the gas barrier resin layer is provided so as to overlap at least the second region as viewed from the stacking direction.

2. The energy storage module according to claim 1, wherein the gas barrier resin layer is made of a resin material containing vinyl alcohol as a monomer.

3. The energy storage module described in claim 1 or 2, wherein the first sealing layer is formed by connecting a plurality of sheet materials and includes a connecting portion in which the first resin layer and the second resin layer of two of the sheet materials are overlapped and welded to each other, and in the connecting portion, the first resin layer and the second resin layer are made of polyolefin resin.

4. The energy storage module as described in claim 1 or 2, wherein the first resin layer is a polyolefin resin, the plurality of sealing layers further include a second sealing layer provided on the inner surface, the second sealing layer includes a third resin layer made of polyolefin resin and welded to the inner surface, and the sealing portion further has an outer edge welded portion in which the first resin layer and the third resin layer are integrated with each other by welding so as to cover the outer edge of the current collector.

5. The energy storage module described in claim 4, wherein, when viewed from the stacking direction, the outer edge welded portion is positioned at a distance from the end face welded portion, and the gas barrier resin layer is provided at least between the outer edge welded portion and the end face welded portion when viewed from the stacking direction.

6. The energy storage module according to claim 4, wherein the second seal layer further includes a core resin layer provided on the third resin layer and having higher crystallinity than the third resin layer.

Images