Method for manufacturing electric power storage module, and electric power storage module

Abstract

Provided is a method for manufacturing an electric power storage module, the method comprising: a resin frame attachment step for forming a resin-framed electrode; a stacking step for forming a stacked body by alternately stacking resin-framed electrodes and metal inserts in a first direction so that the inserts are arranged between adjacent resin frames; a restraining step for restraining the stacked body in the first direction using a pair of restraining plates; and a welding step for forming a weld by melting, using a heater, an end section of an outer portion that is separated from an inner portion as seen from the first direction. In the stacking step, the stacked body is formed such that the inserts extend in a second direction intersecting the first direction, and as seen from the first direction, second-direction first ends of the inserts overlap the inner portion and second-direction second ends of the inserts protrude from the outer portion. In the welding step, the inserts are heated to a temperature that is equal to or higher than the melting temperature of the resin frames.

Description

Electricity storage module manufacturing method and electricity storage module

[0001] The present disclosure relates to a method for manufacturing an energy storage module and 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, the ends of an electrically insulating frame (sealing layer) are welded together to form a resin sealing portion that seals the internal space between the electrodes. When welding the ends of the sealing layers, a metal insert is inserted between the sealing layers to form a communication hole that functions as a liquid inlet in the sealing portion. However, in the vicinity of the insert, the insert is prone to heat dissipation, so the end-face weld portion may not be formed thick enough. This may result in a decrease in sealing performance.

[0005] An object of the present disclosure is to provide a method for manufacturing an electricity storage module that can suppress deterioration in sealing performance, and an electricity storage module.

[0006] A method for manufacturing an energy storage module according to one aspect of the present disclosure includes a laminate in which a plurality of electrodes including a bipolar electrode are laminated in a first direction, and a sealing portion formed by laminating, in the first direction, a plurality of resin frame portions provided on the outer edge of the electrode so as to surround the laminate when viewed from the first direction, each of the plurality of resin frame portions having an outer portion provided on the outside of the electrode and an inner portion provided on the inside of the electrode when viewed from the first direction, the method comprising the steps of: a resin frame portion attachment step of joining the inner portion to the outer edge of the electrode to form an electrode with a resin frame portion; and a step of arranging a metal nest between adjacent resin frame portions in the first direction. The method includes a stacking step of alternately stacking electrodes with resin frame portions and inserts in a first direction to form a stack; a restraining step of restraining the stack in the first direction with a pair of restraint plates; and a welding step of melting the ends of multiple outer portions with a heater to form integrated welded portions as viewed from the first direction, wherein in the stacking step, the inserts extend in a second direction intersecting the first direction, and are formed so that, as viewed from the first direction, a first end of the insert in the second direction overlaps with the inner portion and a second end of the insert in the second direction protrudes from the outer portion, and in the welding step, the inserts are heated to a temperature equal to or higher than the melting temperature of the resin frame portion.

[0007] In the manufacturing method of the energy storage module, the insert is heated by the non-contact heater to a temperature equal to or higher than the melting temperature of the resin frame, so that heat from the resin frame is less likely to transfer from the peripheral portion of the insert to the insert. As a result, the welded portion is formed with sufficient thickness even at the peripheral portion of the insert. As a result, deterioration of sealing performance can be suppressed.

[0008] The heater may be a non-contact heater, and the insert may be heated by the heat of the non-contact heater in the welding process.

[0009] In the restraining step, an end of the outer portion may be provided on the outer side of the restraining plate when viewed from the first direction.

[0010] In the welding step, the insert may be heated so that the thickness of the peripheral portion of the insert at the welded portion is equal to or greater than the thickness of the portion other than the peripheral portion of the welded portion.

[0011] The heater may have a shape extending in a first direction, the heater may be longer than the laminate in the first direction, and in the welding step, a plurality of heaters may be arranged in a direction intersecting the first direction.

[0012] The resin frame portion provided in the bipolar electrode may have a first sealing layer joined to the outer edge of the first surface of the electrode, a second sealing layer joined to the outer edge of the second surface opposite the first surface of the electrode, and a spacer layer disposed on the first sealing layer or the second sealing layer.

[0013] An energy storage module according to one aspect of the present disclosure comprises a stack of a plurality of electrodes, including bipolar electrodes, stacked in a first direction, and a resin sealing portion provided on the outer edge of the electrode so as to surround the stack when viewed from the first direction, wherein the sealing portion has an inner portion arranged inside the outer edge of the electrode and joined to the outer edge, an outer portion arranged outside the outer edge of the electrode, and a welding portion at which an end of the outer portion spaced apart from the inner portion is welded, and the sealing portion has a communication hole formed therein that extends in a second direction intersecting the first direction and communicates with an internal space formed between the electrodes, and the welding portion includes a peripheral portion of the communication hole, and the thickness of the peripheral portion of the welding portion is thicker than the thickness of the portion that is not the peripheral portion of the welding portion.

[0014] In the above-described energy storage module, the welded portion is formed with a sufficient thickness even at the peripheral edge of the communication hole, thereby making it possible to prevent deterioration of sealing performance.

[0015] The thickness of the welded portion may increase in the peripheral portion as it approaches the communication hole.

[0016] According to the present disclosure, it is possible to provide a manufacturing method for an electricity storage module that can suppress deterioration in sealing performance, and an electricity storage module.

[0017] FIG. 1 is a schematic plan view showing an energy storage module according to an embodiment. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a partial enlarged view of FIG. 2. FIG. 4 is a flowchart showing a method for manufacturing an energy storage module according to an embodiment. FIG. 5 is a cross-sectional view for explaining a method for manufacturing an energy storage module according to an embodiment. FIG. 6 is a cross-sectional view showing an example of an end face weld formed by a welding process according to a comparative example. FIG. 7 is a cross-sectional view showing an example of an end face weld formed by a welding process according to an embodiment. FIG. 8 is a cross-sectional view showing another example of an end face weld formed by a welding process according to an embodiment.

[0018] 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.

[0019] (Electricity storage module) FIG. 1 is a schematic plan view of an electric storage module according to an embodiment. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a partial enlarged view of FIG. 2. The electric storage module 1 according to the embodiment shown in FIGS. 1 to 3 can be used as a battery for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The electric storage module 1 is, for example, a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. The electric storage module 1 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 electric storage module 1.

[0020] The energy storage module 1 has a module body 2 and a pair of conductive plates (not shown). The module body 2 is disposed between the pair of conductive plates in the Z-axis direction. The pair of conductive plates apply a restraint load in the Z-axis direction to the module body 2. The conductive plates are conductive and also function as terminals for extracting current from the energy storage module 1. The conductive plates can be used to electrically connect multiple energy storage modules 1. A cooling flow path may be formed in the conductive plate. The energy storage module 1 can be cooled by circulating a cooling medium through the cooling flow path formed in the conductive plate.

[0021] The module body 2 includes an electrode stack (stack) 12 and a resin sealing portion 13. The electrode stack 12 is configured by stacking multiple electrodes in the Z-axis direction (first direction). The Z-axis direction is the stacking direction of the multiple electrodes. The multiple electrodes include multiple bipolar electrodes 14, a positive terminal electrode 16, and a negative terminal electrode 17. Separators 15 are interposed between adjacent electrodes.

[0022] The plurality of bipolar electrodes 14 are disposed between the positive terminal electrode 16 and the negative terminal electrode 17 in the Z-axis 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.

[0023] 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. The first surface 21a and the second surface 21b face opposite each other in the Z-axis direction. 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.

[0024] 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.

[0025] 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 outer edge portion 21c of the current collector 21 is exposed.

[0026] 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 surface of the 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 Z-axis direction.

[0027] 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.

[0028] 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).

[0029] 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 outer edge portion 21c of the current collector 21 is exposed. In one example, when viewed from the Z-axis direction, the positive electrode active material layer 22 is contained within the area of ​​the negative electrode active material layer 23. That is, 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. In one example, when viewed from the Z-axis direction, the negative electrode active material layer 23 is contained within the area of ​​the conductive plate. That is, the outer edge of the negative electrode active material layer 23 may be slightly smaller than the outer edge of the conductive plate.

[0030] In one example, the negative electrode active material layer 23 may be provided on the second surface 21b of the current collector 21 via an adhesive layer. The adhesive layer used for the negative electrode active material layer 23 may be the same as the adhesive layer used for the positive electrode active material layer 22. In one example, the adhesive layer may be provided on the entire surface of the second surface 21b of the current collector 21.

[0031] 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 carbon such as graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, and soft 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 used in the negative electrode active material layer 23 may be the same as those used in the positive electrode active material layer 22.

[0032] 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.

[0033] In the electrode stack 12, bipolar electrodes 14, 14 adjacent in the Z-axis 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 the bipolar electrodes 14, 14 adjacent in the Z-axis direction. In this embodiment, the separator 15 is a sheet-like member having a rectangular shape in a plan view, and prevents short-circuiting between the bipolar electrodes 14, 14 adjacent in the Z-axis direction.

[0034] 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 and smaller than the current collector 21 when viewed from the Z-axis direction. When viewed from the Z-axis direction, the end 15a 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 Z-axis direction, the end 15a of the separator 15 does not overlap with either the positive electrode active material layer 22 or the negative electrode active material layer 23.

[0035] 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 that constitute the separator 15 include polypropylene, polyethylene, polyolefin, and polyester. 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.

[0036] 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 be rectangular, 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 using 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.

[0037] 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.

[0038] 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 on one end side in the Z-axis direction of the electrode laminate 12 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 positive electrode active material layer 22 and the negative electrode active material layer 23 are not provided on the second surface 21b of the current collector 21, and the second surface 21b is electrically connected to an adjacent conductive plate. The current collector 21 used in the positive terminal electrode 16 may be made of aluminum foil.

[0039] The negative terminal electrode 17 is composed of a current collector 21 and a negative electrode active material layer 23 provided on the second surface 21b of the current collector 21. The negative terminal electrode 17 is arranged on the other end side in the Z-axis direction of the electrode laminate 12 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. The current collector 21 used in the negative terminal electrode 17 may be made of copper foil.

[0040] The separators 15 are arranged between the bipolar electrodes 14, 14 adjacent to each other in the Z-axis 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 arrangement of the separators 15 prevents 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.

[0041] The sealing portion 13 is a member that seals the internal space S between the current collectors 21, 21 adjacent to each other in the Z-axis direction. The sealing portion 13 has electrical insulation properties. When viewed from the Z-axis direction, the sealing portion 13 is provided on the outer edge portion 21c of the current collector 21 so as to surround the electrode stack 12. The sealing portion 13 is joined to the outer edge portion 21c of the current collector 21. When viewed from the Z-axis direction, the sealing portion 13 is, for example, separated from the positive electrode active material layer 22 and the negative electrode active material layer 23. When viewed from the Z-axis direction, the inner edge portion of the sealing portion 13 may overlap the positive electrode active material layer 22 and the negative electrode active material layer 23. When viewed from the Z-axis direction, the sealing portion 13 has a rectangular frame shape. When viewed from the Z-axis direction, the sealing portion 13 is disposed between the current collectors 21, 21 adjacent to each other in the Z-axis 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 energy storage module 1, an internal space S is defined by the current collectors 21, 21 adjacent to each other in the Z-axis direction and the sealing portion 13. 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 Z-axis direction, and therefore also functions as a spacer that maintains the distance between the adjacent current collectors 21, 21.

[0042] The sealing portion 13 includes a plurality of first sealing layers 31 made of resin, a plurality of second sealing layers 32 made of resin, and a plurality of spacer layers 33 made of resin. The first sealing layer 31 is spaced apart from the positive electrode active material layer 22 and bonded to the outer edge portion 21c of the first surface 21a of each current collector 21. The second sealing layer 32 is spaced apart from the negative electrode active material layer 23 and bonded to the outer edge portion 21c of the second surface 21b of each current collector 21. The first sealing layer 31 may be spaced apart from or overlap the negative electrode active material layer 23 when viewed from the Z-axis direction. The first sealing layer 31 and the second sealing layer 32 are provided on the outer edge portion 21c of the current collector 21 so as to extend beyond the outer edge 21d of the current collector 21.

[0043] When viewed from the Z-axis direction, the first seal layer 31 and the second seal layer 32 have a frame shape (here, a rectangular frame shape) that follows the outer edge 21d of the current collector 21. The outer edge 21d forms the outer edge of the electrode. When viewed from the Z-axis direction, the outer edge 21d of the current collector 21 is larger than the inner edge 31a of the first seal layer 31 and the inner edge 32a of the second seal layer 32, and smaller than the outer edge 31b of the first seal layer 31 and the outer edge 32b of the second seal layer 32. When viewed from the Z-axis direction, the first seal layer 31 is bonded to the first surface 21a in a region from the inner edge 31a of the first seal layer 31 to the outer edge 21d of the current collector 21. When viewed from the Z-axis direction, the second seal layer 32 is bonded to the second surface 21b in a region from the inner edge 32a of the second seal layer 32 to the outer edge 21d of the current collector 21.

[0044] The first sealing layer 31 and the second sealing layer 32 may have, for example, the same shape. The thickness (length in the Z-axis direction) of the first sealing layer 31 and the second sealing layer 32 may be 100 μm or more and 200 μm or less. The first sealing layer 31 and the second sealing layer 32 may have different shapes.

[0045] The first sealing layer 31 and the second sealing layer 32 are made of, for example, the same resin material. The first sealing layer 31 and the second sealing layer 32 are made of, for example, a polyolefin-based 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 sealing layer 31 and the second sealing layer 32 may be different from each other.

[0046] The spacer layer 33 is disposed between the first seal layer 31 and the second seal layer 32 adjacent to each other in the Z-axis direction without any current collector 21 therebetween. The spacer layer 33 is disposed between the first seal layer 31 and the second seal layer 32 between the current collectors 21 adjacent to each other in the Z-axis direction. One layer each of the first seal layer 31, the second seal layer 32, and the spacer layer 33 is disposed between the current collectors 21 adjacent to each other in the Z-axis direction.

[0047] The spacer layer 33, together with the first seal layer 31 and the second seal layer 32, seals the internal space S formed between the current collectors 21, 21 adjacent to each other in the Z-axis direction. The spacer layer 33 has a frame shape (here, a rectangular frame shape) that follows the outer edge 21d of the current collector 21 when viewed from the Z-axis direction. The outer edge 33b of the spacer layer 33 may be located at the same position as the outer edge 31b of the first seal layer 31 and the outer edge 32b of the second seal layer 32 when viewed from the Z-axis direction. The thickness (length in the Z-axis direction) of the spacer layer 33 may be thicker than the thicknesses (lengths in the Z-axis direction) of the first seal layer 31 and the second seal layer 32, and may be 200 μm or more and 500 μm or less.

[0048] The spacer layer 33 is made of, for example, a resin material different from that of the first seal layer 31 and the second seal layer 32. The spacer layer 33 is made of, for example, a polyolefin-based resin material having electrolyte resistance, such as acid-modified PE, acid-modified PP, polyethylene, or polypropylene. The spacer layer 33 may have, for example, higher crystallinity than the first seal layer 31 and the second seal layer 32. This can suppress moisture permeation through the sealing portion 13.

[0049] As shown in Fig. 2, the sealing portion 13 has an inner portion 13a and an outer portion 13b. When viewed from the Z-axis direction, the inner portion 13a is disposed inside the outer edge 21d of the current collector 21 and is joined to the outer edge portion 21c. When viewed from the Z-axis direction, the outer portion 13b is disposed outside the outer edge 21d of the current collector 21. The inner portion 13a is configured to include inner portions of multiple first sealing layers 31, inner portions of multiple second sealing layers 32, and inner portions of multiple spacer layers 33. The outer portion 13b is configured to include outer portions of multiple first sealing layers 31, outer portions of multiple second sealing layers 32, and outer portions of multiple spacer layers 33.

[0050] The sealing portion 13 has an end surface weld 34 (welded portion) at the end of the outer portion 13b separated from the inner portion 13a when viewed from the Z-axis direction, i.e., at the outer edge of the sealing portion 13. The end surface weld 34 is formed by welding the outer edges of the first sealing layers 31, the second sealing layers 32, and the spacer layers 33 together, outside the outer edge 21d of the current collector 21 when viewed from the Z-axis direction. As an example, the first sealing layer 31, the second sealing layer 32, and the spacer layer 33 are not welded to each other except at the end surface weld 34 and are only in contact with each other. A gap V is formed between the end surface weld 34 and the outer edge 21d of the current collector 21. The first sealing layer 31 and the second sealing layer 32 are separated from each other by the gap V.

[0051] The end surface welded portion 34 has a rectangular frame shape when viewed from the Z-axis direction, and surrounds the electrode stack 12. The side surface of the end surface welded portion 34 opposite the internal space S extends along the Z-axis direction and forms 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.

[0052] The thickness of the end face weld 34 is defined by the distance between the inner surface and the outer surface of the end face weld 34. The thickness of the end face weld 34 is the length of the end face weld 34 in a direction perpendicular to the outer surface. The thickness of the end face weld 34 is, for example, 1 mm or more and 10 mm or less. By making the thickness of the end face weld 34 1 mm or more, a decrease in sealing performance can be suppressed. The thickness of the end face weld 34 may be 3 mm or more.

[0053] If the heating time or temperature during formation of the end face weld 34 is increased in order to thicken the end face weld 34, the outer surface of the end face weld 34 may be burned. Even if an attempt is made to provide a resin layer on such an outer surface by, for example, injection molding, it is difficult for the resin layer to be welded to the end face weld 34. By keeping the thickness of the end face weld 34 at 10 mm or less, damage to the surface of the end face weld 34 can be suppressed.

[0054] The sealing portion 13 has a communication hole 35 formed therein that communicates with the internal space S formed between the electrodes. The communication hole 35 extends in a direction intersecting the Z-axis direction. In this embodiment, the communication hole 35 extends in the X-axis direction. As an example, the communication hole 35 is formed by partially cutting out the spacer layer 33, and penetrates the spacer layer 33 and the end face weld portion 34. The communication hole 35 has one opening in the internal space S and the other opening on the outer surface of the sealing portion 13 formed by the end face weld portion 34.

[0055] In the energy storage module 1, a cell including one internal space S is formed between adjacent current collectors 21, 21. Here, one communication hole 35 is formed for one cell. The communication hole 35 can be used as a liquid filling port for filling the internal space S with an electrolyte solution. 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 1 having a rectangular shape when viewed from the Z-axis direction, the side on which the communication hole 35 is provided is referred to as the liquid filling port side. The multiple communication holes 35 are, for example, distributed in the Y-axis direction so that the communication holes 35 provided in internal spaces S adjacent to each other in the Z-axis direction do not overlap each other when viewed from the Z-axis direction. In FIG. 1 , only one communication hole 35 is indicated by a dashed line, and the other communication holes 35 are not shown.

[0056] When viewed from the Z-axis direction, the inner edge 33a of the spacer layer 33 around the liquid inlet is located inside (closer to the internal space S) than the inner edge 31a of the first seal layer 31 and the inner edge 32a of the second seal layer 32. 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 edges 31a and 32a, and is exposed from the first seal layer 31 and the second seal layer 32 so as to face the internal space S. When viewed from the Z-axis 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 31a of the first seal layer 31 and the inner edge 32a of the second seal layer 32, or may be located inside the inner edge 31a of the first seal layer 31 and the inner edge 32a of the second seal layer 32.

[0057] As shown in FIG. 3 , the end face weld 34 includes a peripheral portion 36 of the communicating hole 35. The peripheral portion 36 faces the internal space of the communicating hole 35. The peripheral portion 36 includes the end of the inner surface of the communicating hole 35 that faces the outer surface of the sealing portion 13. The peripheral portion 36 surrounds the communicating hole 35 when viewed from the X-axis direction. The thickness of the peripheral portion 36 is thicker than the thickness of a portion of the end face weld 34 that is not the peripheral portion 36. The portion of the end face weld 34 that is not the peripheral portion 36 refers to the portion of the end face weld 34 other than the peripheral portion 36, or the portion of the end face weld 34 excluding the peripheral portion 36. The thickness of the end face weld 34 at the peripheral portion 36 increases toward the communicating hole 35. That is, the thickness of the end face weld 34 is thickest at the inner surface of the communicating hole 35 near the liquid inlet. The thickness of the end surface weld 34 at the liquid inlet side is the length in the X-axis direction of the end surface weld 34. The thickness of the end surface weld 34 at the side opposite the liquid inlet side of the energy storage module 1 is also the length in the X-axis direction of the end surface weld 34. The thickness of the end surface weld 34 at the two sides of the energy storage module 1 adjacent to the liquid inlet side is the length in the Y-axis direction of the end surface weld 34.

[0058] (Manufacturing Method of Energy Storage Module) Fig. 4 is a flowchart showing a manufacturing method of an energy storage module according to the embodiment. Fig. 5 is a cross-sectional view for explaining the manufacturing method of an energy storage module according to the embodiment. As shown in Fig. 4, the manufacturing method of an energy storage module 1 according to the embodiment includes a resin frame attachment step S1, a stacking step S2, a restraining step S3, and a welding step S4. By performing these steps in this order, the energy storage module 1 is obtained.

[0059] The resin frame attachment step S1 is a step of providing a resin frame 11 on the electrode. As an example, the bipolar electrode 14 and the negative terminal electrode 17 are provided with a first seal layer 31, a second seal layer 32, and a spacer layer 33 as a resin frame 11A. The positive terminal electrode 16 is provided with a first seal layer 31 and a second seal layer 32 as a resin frame 11B. In the resin frame attachment step S1, the inner portions of the first seal layer 31 and the second seal layer 32 are bonded to the outer edge portions 21c of the first surfaces 21a and the second surfaces 21b of the electrodes. The outer portions of the first seal layer 31 and the second seal layer 32 are positioned to extend outside the outer edge 21d of the electrodes. The bonding of the first seal layer 31 and the second seal layer 32 may be performed using a contact-type heating device such as an impulse sealer or an ultrasonic sealer, or may be performed using a non-contact heating device such as a laser sealer.

[0060] In the case of the bipolar electrode 14 and the negative terminal electrode 17, a spacer layer 33 is then provided on the second seal layer 32. At this time, the end 15a of the separator 15 is sandwiched between the second seal layer 32 and the spacer layer 33. The separator 15 and the spacer layer 33 may be partially welded to the second seal layer 32 by, for example, spot welding. The spacer layer 33 is provided so that its outer edge 33b coincides with the outer edge 31b of the first seal layer 31 and the outer edge 32b of the second seal layer 32. This results in a resin-framed electrode in which the inner portion 11a of the resin frame 11, whose outer portion 11b is located outside the outer edge 21d of the electrode, is joined to the outer edge 21c of the electrode.

[0061] When viewed from the Z-axis direction, the resin frame 11 has an inner portion 11a provided inside the outer edge portion 21c of the electrode and an outer portion 11b provided outside the outer edge portion 21c of the electrode. The inner portion 11a is stacked in the Z-axis direction to form the inner portion 13a of the sealing portion 13. The outer portion 11b is stacked in the Z-axis direction to form the outer portion 13b of the sealing portion 13.

[0062] As shown in FIG. 5 , the stacking process S2 is a process of alternately stacking the resin frame-attached electrodes and the metal inserts 4 in the Z-axis direction so that the metal inserts 4 are disposed between adjacent resin frame portions 11, 11, to form the stack 10. The stack 10 is the stack that becomes the module main body 2. The sealing portion 13 is formed by stacking a plurality of resin frame portions 11 in the Z-axis direction. The inserts 4 are rectangular metal plates when viewed from the Z-axis direction. The inserts 4 are made of, for example, stainless steel. The inserts 4 are used to form communication holes 35 in the sealing portion 13. The thickness of the inserts 4 is, for example, slightly thinner than the thickness of the spacer layer 33.

[0063] The laminate 10 is formed so that the insert 4 extends in the X-axis direction (second direction) and, when viewed from the Z-axis direction, a first end 4a of the insert 4 in the X-axis direction overlaps with the inner portion of the resin frame 11, and a second end 4b in the X-axis direction protrudes from the outer portion of the resin frame 11. The insert 4 is disposed in a cutout partially provided in the spacer layer 33. This cutout serves as a through hole 35. A release layer such as a fluorine coating may be provided on the surface of the insert 4 to facilitate peeling from the resin. The release layer is provided on a portion of the insert 4 near the first end 4a disposed between the resin frames 11, 11, and does not necessarily have to be provided on a portion near the second end 4b protruding from the outer portion of the resin frame 11.

[0064] The restraining step S3 is a step of restraining the stack 10 in the Z-axis direction with a pair of restraining plates 6 so that the outer portions 11b of the laminated resin frame portions 11 protrude. The pair of restraining plates 6 are provided so that, when viewed from the Z-axis direction, the second ends 4b of the inserts 4 and the ends 11c of the outer portions of the resin frame portions 11 protrude from the restraining plates 6. A resin portion 7 made of, for example, polytetrafluoroethylene (PTFE) is disposed between the restraining plates 6 and the resin frame portion 11. The restraining plates 6 are not in direct contact with the resin frame portion 11.

[0065] 5 , the welding step S4 is a step of using a heater 5 to melt an end 11c of the outer portion 11b of the resin frame 11 that is spaced from the inner portion 11a as viewed in the Z-axis direction, thereby forming an end surface welded portion 34. That is, in the welding step S4, the end 11c of the resin frame 11 that protrudes from the restraint plate 6 as viewed in the Z-axis direction is welded. Because the end 11c protrudes from the restraint plate 6 in this way, it can be easily welded.

[0066] The heater 5 has a shape extending in the Z-axis direction. The length of the heater 5 in the Z-axis direction is longer than the total length of the multiple stacked resin frame portions 11 in the Z-axis direction. The length of the heater 5 in the Z-axis direction is, for example, 30 mm or more. The total length of the multiple stacked resin frame portions 11 in the Z-axis direction is, for example, 20 mm. The heater 5 is, for example, a non-contact heater. The non-contact heater is, for example, an infrared (IR) heater. The non-contact heater is, for example, a carbon filament heater. A laser device such as an infrared laser may be used as the heater 5. The multiple heaters 5 may be lined up along the sides of the rectangular laminate 10 when viewed in the Z-axis direction. That is, in the welding process S4, the multiple heaters 5 may be arranged in a direction intersecting the Z-axis direction, specifically in the X-axis and Y-axis directions.

[0067] The heater 5 is disposed at a distance from the insert 4 and the resin frame 11. When the heater 5 is an IR heater, the resin frame 11 melts by absorbing infrared rays. Specifically, in the resin material constituting the resin frame 11, intermolecular vibrational motion is activated by absorbing infrared rays, and the energy of the vibrational motion is converted into heat, melting the resin material. Metals absorb infrared rays less easily than resins. Therefore, the insert 4 is less likely to be heated by infrared rays than the resin frame 11. Furthermore, metals have higher heat dissipation properties than resins. Therefore, the insert 4 has higher heat dissipation properties than the resin frame 11 and is more susceptible to heat loss. In actual IR heaters, a portion of the input power is not converted into infrared rays and contributes to heating the filament itself, which is the infrared radiation source. The heated filament heats the air near the filament. Therefore, when the insert 4 is disposed near the heater 5, the insert 4 is heated by atmospheric heating, in which heat from the heater 5 is transferred through the nearby air.

[0068] If the distance between the heater 5 and the insert 4 is long or the heater 5 output is weak, the insert 4 is difficult to heat even by ambient heating. If the temperature of the insert 4 is lower than that of the resin frame 11, heat is transferred from the resin frame 11 heated by infrared rays to the insert 4. This heat transfer is more likely to occur closer to the insert 4. Therefore, there is a risk that the end face welds 34 will not be formed with sufficient thickness at the peripheral portion of the insert 4. FIG. 6 is a cross-sectional view showing an example of an end face weld formed by a welding process according to a comparative example. In the welding process according to the comparative example, as shown in FIG. 6, the end face welds 34 will not be formed with sufficient thickness at the peripheral portion of the insert 4. This is because the temperature of the insert 4 is lower than that of the resin frame 11, so heat from the resin frame 11 at the peripheral portion of the insert 4 is transferred to the insert 4 and dissipated from the insert 4.

[0069] In contrast, in the welding step S4 according to the embodiment, the insert 4 is heated by the heater 5 to a temperature equal to or higher than the melting temperature of the resin frame 11. This prevents heat from being transferred from the resin frame 11, which is heated by infrared rays, to the insert 4. As a result, the end-face welded portion 34 is formed at a thickness sufficient to prevent a decrease in sealing performance even at the peripheral edge portion 36. Note that if the heater 5 is placed too close to the resin frame 11, the resin material may be heated not only by radiation via infrared rays but also by heat transferred by conduction to the air in contact with the heater 5 and by air convection, resulting in burning (discoloration to brown). Therefore, it is necessary to maintain a sufficient distance between the heater 5 and the resin frame 11 to prevent the resin material from burning due to heat transferred from the heater 5 by conduction and convection. However, because infrared rays cannot heat metal or air, the insert 4 must be heated by heat transferred from the heater 5 by conduction and convection. Therefore, in the welding step S4, the insert 4 is extended to the vicinity of the heater 5 while maintaining a distance between the heater 5 and the resin frame portion 11, and the insert 4 is heated by conduction and convection.

[0070] FIG. 7 is a cross-sectional view showing one example of an end surface weld formed by the welding process according to the embodiment. FIG. 8 is a cross-sectional view showing another example of an end surface weld formed by the welding process according to the embodiment. As shown in FIGS. 7 and 8 , the end surface weld 34 is formed to a sufficient thickness even at the peripheral edge 36. In the welding process S4, as shown in FIG. 7 , the insert 4 may be heated so that the thickness of the end surface weld 34 at the peripheral edge 36 is thicker than at other portions. As shown in FIG. 8 , the insert 4 may be heated so that the thickness of the end surface weld 34 at the peripheral edge 36 is equal to or greater than at other portions. The insert 4 is removed after the welding process S4, and electrolyte is poured into the internal space S through the communication hole 35. The restraint plate 6 and the resin part 7 are removed from the energy storage module 1 after the electrolyte is poured.

[0071] As described above, in the manufacturing method of the energy storage module 1, the insert 4 is heated by the heater 5 to a temperature equal to or higher than the melting temperature of the resin frame 11, so heat is less likely to transfer from the peripheral portion of the insert 4 to the insert 4. As a result, the end face welded portion 34 is formed with a sufficient thickness even in the peripheral portion of the insert 4, i.e., the peripheral portion 36 of the communication hole 35. As a result, deterioration of sealing performance can be suppressed.

[0072] In the welding step S4, the insert 4 is heated by the heat of the heater 5, which is a non-contact heater. Therefore, the insert 4 can be heated by the heater 5 to a temperature equal to or higher than the melting temperature of the resin frame portion 11.

[0073] In the welding step S4, the insert 4 may be heated so that the thickness of the peripheral edge portion 36 of the end face welded portion 34 becomes equal to or greater than the thickness of the portion other than the peripheral edge portion 36 of the end face welded portion 34. In this case, deterioration of the sealing performance can be reliably suppressed.

[0074] In the welding step S4, the insert 4 may be heated so that the thickness of the peripheral edge 36 of the end face weld 34 is greater than the thickness of the portion of the end face weld 34 other than the peripheral edge 36. In this case, deterioration of the sealing performance can be more reliably suppressed. The thickness of the end face weld 34 may be increased in the peripheral edge 36 as it approaches the communicating hole 35. In this case, the thickness of the end face weld 34 is thickest on the inner surface of the communicating hole 35. Therefore, deterioration of the sealing performance can be more reliably suppressed.

[0075] The heater 5 has a shape that extends in the Z-axis direction. The heater 5 is longer than the laminate 10 in the Z-axis direction. In the welding step S4, a plurality of heaters 5 are arranged in a direction that intersects with the Z-axis direction. This allows the end face welds 34 to be formed efficiently.

[0076] The resin frame 11A provided on the bipolar electrode 14 has a first seal layer 31 bonded to the outer edge 21c of the first surface 21a of the bipolar electrode 14, a second seal layer 32 bonded to the outer edge 21c of the second surface 21b of the bipolar electrode 14, and a spacer layer 33 disposed on the first seal layer 31. The first seal layer 31 and the second seal layer 32 improve the bondability of the resin frame 11A to the bipolar electrode 14. The spacer layer 33 ensures that adjacent electrodes are spaced apart.

[0077] In the energy storage module 1, the end surface welded portion 34 is formed with a sufficient thickness even at the peripheral portion 36 of the communication hole 35. As a result, deterioration of the sealing performance can be suppressed.

[0078] 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.

[0079] For example, in the welding step S4, the insert 4 may be heated by the heater 5 to a temperature equal to or higher than the melting temperature of the resin frame 11, and may be heated so that the thickness of the end face welded portion 34 is thinner at the peripheral portion 36 than at other portions. Even in this case, the thickness of the end face welded portion 34 at the peripheral portion 36 is thicker than in a configuration in which the insert 4 is not heated by the heater 5 to a temperature equal to or higher than the melting temperature of the resin frame 11. This makes it possible to suppress a decrease in sealing performance.

[0080] In the resin frame attachment process S1 described above, a spacer layer 33 is provided on the second seal layer 32 of the bipolar electrode 14 and the negative terminal electrode 17, but a spacer layer 33 may also be provided on the first seal layer 31 of the bipolar electrode 14 and the positive terminal electrode 16.

[0081] An aspect of the present disclosure can be expressed as follows: [Clause 1] A method for manufacturing an energy storage module, comprising: a stack in which a plurality of electrodes including bipolar electrodes are stacked in a first direction; and a sealing portion formed by stacking a plurality of resin frame portions in the first direction, the resin frame portions being provided on outer peripheral portions of the electrodes so as to surround the stack when viewed from the first direction, and each of the plurality of resin frame portions having an outer portion provided on the outside of the electrode and an inner portion provided on the inside of the electrode when viewed from the first direction, the method comprising: a resin frame attachment step of joining the inner portion to the outer peripheral portion of the electrode to form a resin-framed electrode; a stacking step of alternately stacking the resin-framed electrode and the metal inserts in the first direction so that a metal insert is disposed between the resin frames adjacent to each other in the first direction to form a stack; a restraining step of restraining the stack in the first direction with a pair of restraint plates; and a welding step of melting end portions of the plurality of outer portions with a heater when viewed from the first direction to form an integrated welded portion, The method for manufacturing an electric storage module according to Clause 1, wherein, in the laminating step, the inserts of the stacked body extend in a second direction intersecting the first direction, and are formed so that, as viewed from the first direction, a first end of the insert in the second direction overlaps with the inner portion and a second end of the insert in the second direction protrudes from the outer portion, and in the welding step, the inserts are heated to a temperature equal to or higher than the melting temperature of the resin frame portion. [Clause 2] The method for manufacturing an electric storage module according to Clause 1, wherein the heater is a non-contact heater, and in the welding step, the inserts are heated by heat from the non-contact heater. [Clause 3] The method for manufacturing an electric storage module according to Clause 1 or 2, wherein, in the restraining step, the end of the outer portion is provided outside the restraining plate as viewed from the first direction. [Clause 4] The method for manufacturing an electric storage module according to any one of Clauses 1 to 3, wherein, in the welding step, the inserts are heated so that a thickness of a peripheral portion of the insert at the welded portion is equal to or greater than a thickness of a portion other than the peripheral portion of the welded portion.[Clause 5] The method for manufacturing an electric storage module according to any one of Clauses 1 to 4, wherein the heater has a shape extending in the first direction, the heater is longer than the laminate in the first direction, and in the welding step, a plurality of the heaters are arranged in a direction intersecting the first direction. [Clause 6] The method for manufacturing an electric storage module according to any one of Clauses 1 to 5, wherein the resin frame provided on the bipolar electrode has a first seal layer joined to the outer edge of a first surface of the bipolar electrode, a second seal layer joined to the outer edge of a second surface of the bipolar electrode opposite to the first surface, and a spacer layer arranged on the first seal layer or the second seal layer. [Clause 7] An energy storage module comprising: a stack of a plurality of electrodes including bipolar electrodes stacked in a first direction; and a resin sealing portion provided on an outer edge of the electrodes so as to surround the stack as viewed from the first direction, wherein the sealing portion has, as viewed from the first direction, an inner portion arranged inside the outer edge of the electrodes and joined to the outer edge, an outer portion arranged outside the outer edge of the electrodes, and a welded portion at which an end of the outer portion spaced apart from the inner portion is welded, wherein the sealing portion has a communication hole extending in a second direction intersecting the first direction and communicating with an internal space formed between the electrodes, the welded portion includes a peripheral portion of the communication hole, and a thickness of the peripheral portion of the welded portion is thicker than a thickness of a portion other than the peripheral portion of the welded portion. [Clause 8] The energy storage module according to Clause 7, wherein the thickness of the welded portion increases in the peripheral portion as it approaches the communication hole.

[0082] 1…Electrode storage module, 4…Entrance, 4a…1st end, 4b…2nd end, 5…Hair, 6…Restriction plate, 10…Layer, 11, 11A, 11B…Resin bracket, 11a…Inner portion, 11b…Outer portion, 11c…End, 12…Electrode laminate (laminate), 13…Seal, 13a…Inner portion, 13b…Outer portion, 14…Viapore RA electrode, 21a…1st surface, 21b…2nd surface, 21c…outer edge, 21d…outer edge, 31…1st shield layer, 32…2nd shield layer, 33…spec layer, 34…end face melted portion (melted portion), 35…connecting hole, 36…peripheral portion, S…inner space, S1…resin portion removal process, S2…lamination process, S3…constraint process, S4…melting process

Claims

1. A method for manufacturing an energy storage module comprising: a laminate in which a plurality of electrodes including a bipolar electrode are laminated in a first direction; and a sealing portion formed by laminating a plurality of resin frame portions in the first direction, the resin frame portions being provided on the outer edge portions of the electrodes so as to surround the laminate as viewed from the first direction, wherein each of the plurality of resin frame portions has an outer portion provided on the outside of the electrode and an inner portion provided on the inside of the electrode as viewed from the first direction, the method comprising: a resin frame attachment step of joining the inner portion to the outer edge portion of the electrode to form a resin-framed electrode; a stacking step of stacking the resin-framed electrode and the metal inserts alternately in the first direction so that a metal insert is disposed between the resin frame portions adjacent to each other in the first direction to form a laminate; a restraining step of restraining the laminate in the first direction with a pair of restraining plates; and a welding step of melting ends of the plurality of outer portions by a heater as viewed from the first direction to form an integrated welded portion, a first end of the insert in the second direction overlaps with the inner portion and a second end of the insert in the second direction protrudes from the outer portion when viewed from the first direction; and a second end of the insert in the second direction protrudes from the outer portion when viewed from the first direction; and a second end of the insert in the second direction protrudes from the outer portion when viewed from the first direction.

2. The method for producing an electric storage module according to claim 1, wherein the heater is a non-contact heater, and in the welding step, the insert is heated by heat from the non-contact heater.

3. The method for manufacturing an energy storage module according to claim 1 or 2, wherein in the restraining step, the end of the outer portion is provided outside the restraining plate when viewed from the first direction.

4. A method for manufacturing an energy storage module as described in claim 1 or 2, wherein in the welding step, the insert is heated so that the thickness of the peripheral portion of the insert at the welded portion is equal to or greater than the thickness of the non-peripheral portion of the welded portion.

5. A method for manufacturing an energy storage module as described in claim 1 or 2, wherein the heater has a shape extending in the first direction, the heater is longer than the laminate in the first direction, and in the welding process, a plurality of the heaters are arranged in a direction intersecting the first direction.

6. A method for manufacturing an energy storage module as described in claim 1 or 2, wherein the resin frame portion provided on the bipolar electrode has a first seal layer joined to the outer edge portion of a first surface of the bipolar electrode, a second seal layer joined to the outer edge portion of a second surface of the bipolar electrode opposite the first surface, and a spacer layer disposed on the first seal layer or the second seal layer.

7. An energy storage module comprising: a laminate in which a plurality of electrodes including bipolar electrodes are stacked in a first direction; and a resin sealing portion provided on an outer edge of the electrodes so as to surround the laminate when viewed from the first direction, wherein the sealing portion has, when viewed from the first direction, an inner portion arranged inside the outer edge of the electrodes and joined to the outer edge, an outer portion arranged outside the outer edge of the electrodes, and a welding portion at which an end of the outer portion spaced apart from the inner portion is welded, wherein the sealing portion has a communication hole extending in a second direction intersecting the first direction and communicating with an internal space formed between the electrodes, the welding portion includes a peripheral portion of the communication hole, and a thickness of the peripheral portion of the welding portion is thicker than a thickness of a portion of the welding portion other than the peripheral portion.

8. The energy storage module according to claim 7, wherein the thickness of the welded portion increases in the peripheral portion toward the communication hole.

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