Method for manufacturing power storage module and welding device

Abstract

This method for manufacturing a power storage module includes: a preparation step for preparing an electrode 4 with a resin frame by welding a first resin frame 41 made of resin to an outer edge part of an electrode foil 42 provided with an active material layer; an arrangement step for arranging a second resin frame 5 made of resin on the first resin frame 41 of the electrode 4 with a resin frame so as to be overlapped; a temporary fixing step for temporarily fixing the first resin frame 41 and the second resin frame 5 overlapped in the arrangement step by spot welding using a hot iron 8; and a lamination step for forming a laminate by laminating a plurality of electrodes 4 with a resin frame to which the second resin frame 5 is temporarily fixed as one lamination unit. The temporary fixing step includes arranging a sheet member 9 between a tip part 8a of the hot iron 8 and the first resin frame 41 or the second resin frame 5, and spot welding the first resin frame 41 and the second resin frame 5 with the sheet member 9 interposed therebetween.

Description

Manufacturing method and welding device for energy storage module

[0001] The present disclosure relates to a manufacturing method and welding apparatus for an energy storage module.

[0002] A conventional method for manufacturing an energy storage module is described in, for example, Patent Document 1. In the method of Patent Document 1, a bipolar electrode and a resin frame are prepared (preparation step), and the resin frame is welded to the peripheral edge of the electrode plate of the bipolar electrode while applying pressure to form a bipolar electrode unit (welding step). Then, a plurality of bipolar electrode units are stacked in the stacking direction to form an electrode stack (stacking step). After the electrode stack is formed, the stacked resin frames are welded together to seal the electrode stack (sealing step).

[0003] JP 2020-95909 A JP 2020-9631 A

[0004] In an energy storage module manufactured by the above-described manufacturing method, as described in Patent Document 2, for example, a stacked unit may be formed by stacking a resin spacer on a resin frame welded to an electrode plate. When arranging such a spacer, it is considered to temporarily fix the spacer to the resin frame at the stage where the spacer is placed on the resin frame in order to prevent misalignment between the resin frame and the spacer during the subsequent stacking process. The temporary fixation of the spacer to the resin frame is performed by spot welding the spacer to the resin frame using, for example, a hot iron or the like.

[0005] When the spacer and the resin frame are spot-welded using a hot iron, the generation of burrs at the welded portion becomes an issue. If the stacked units are stacked with burrs at the welded portion of the spacer, gaps due to the burrs will form between the spacer and the resin frame between adjacent stacked units in the stacking direction, which may result in poor sealing in the electrode stack that has undergone the sealing process.

[0006] An object of the present disclosure is to provide a manufacturing method and welding device for an energy storage module that can suppress the occurrence of burrs at welding points where resin members are temporarily fixed together.

[0007] In a manufacturing method of an energy storage module according to one aspect of the present disclosure, the temporary fixing step involves spot welding the first resin frame and the second resin frame via a sheet member placed at the tip of a hot iron. With this technique, when the resin constituting the first resin frame or the second resin frame melts due to the heat from the hot iron, the molten resin flows along the surface of the sheet member, preventing the resin from protruding due to the application of the hot iron. This allows the resin to cool and harden in a flattened state, preventing burrs from forming at the welding points where the resin members are temporarily fixed together.

[0008] This method for manufacturing an energy storage module further includes a restraining step of restraining the stack in the stacking direction of the stacked units and applying a restraining load to the first resin frame and the second resin frame aligned in the stacking direction, and an end face welding step of welding the outer edges of the first resin frame and the second resin frame adjacent in the stacking direction together while the restraining load is applied. This configuration suppresses burrs at the welded points between the first resin frame and the second resin frame 5 in the temporary fixing step, thereby ensuring sufficient adhesion between the first resin frame and the second resin frame between adjacent stacked units in the restraining step. Therefore, in the end face welding step, the outer edges of the first resin frame and the second resin frame are well welded together, effectively suppressing poor sealing of the stack.

[0009] In the temporary fixing process, the tip of the hot iron is pressed against the first or second resin frame while tension is applied to the sheet member. This configuration prevents the sheet member from warping when the molten resin flows along the surface of the sheet member. This maintains the flatness of the resin and more reliably prevents burrs from occurring at the welding points.

[0010] In this method for manufacturing an energy storage module, the resin-framed electrode has a rectangular shape having four sides in a plan view, one of the four sides being set as a reference side, and in the arrangement step, the second resin frame is arranged so that the side on which the liquid inlet portion is formed overlaps the reference side, and in the temporary fixing step, the first resin frame and the second resin frame are spot-welded via a sheet member at least along the reference side, and in the stacking step, stacked units are stacked while aligning the reference side as a stacking reference. When a reference side is set in the resin-framed electrode and stacked units are stacked with the reference side aligned, portions of the sides other than the reference side that include the spot-welded portions of the first resin frame and the second resin frame can be removed as excess portions before stacking, but portions of the reference side that include the spot-welded portions of the first resin frame and the second resin frame must be left. Therefore, by spot welding the first resin frame and the second resin frame via the sheet member at least at the reference edge and suppressing the occurrence of burrs at the welding point, it is possible to suitably ensure adhesion between the first resin frame and the second resin frame between adjacent stacked units.

[0011] In the arrangement step, a separator is placed on the resin-framed electrode before the second resin frame is placed, and then the outer edge of the separator is fixed to the first resin frame. In the temporary fixing step, the first resin frame and the second resin frame are spot-welded via a sheet member in a region between the outer edge of the electrode foil and the outer edge of the separator as viewed from the stacking direction. This configuration makes it possible to suppress the occurrence of burrs at the weld points between the first resin frame and the second resin frame, taking into consideration the positional relationship of the separator with respect to the resin-framed electrode.

[0012] A welding device according to one aspect of the present disclosure includes a hot iron for spot welding resin members (a first resin frame and a second resin frame) together, with a sheet material attached to the tip of the hot iron that covers a wider area than the tip. Consider a case in which the welding device is used to spot weld two overlapping resin members (a first resin frame and a second resin frame) from the upper resin member (the second resin frame) side. In this case, a sheet material is attached to the tip of the hot iron. As a result, when the resin constituting the upper resin member (the second resin frame) is melted by heat from the hot iron, the molten resin material flows along the surface of the sheet material, preventing the resin member from protruding due to the application of the hot iron. This allows the resin members to cool and harden in a flattened state, preventing burrs from forming at the welding point.

[0013] According to the present disclosure, it is possible to provide a manufacturing method and welding device for an energy storage module that can suppress the occurrence of burrs at welding points where resin members are temporarily fixed together.

[0014] FIG. 1 is a schematic cross-sectional view of an energy storage module manufactured by a method for manufacturing an energy storage module according to an embodiment. FIG. 2( a) is a cross-sectional view of a stacked unit, and FIG. 2( b) is a plan view of the stacked unit. FIG. 3 is a flowchart showing one step of a method for manufacturing an energy storage module. FIG. 4( a) is a diagram for explaining the arrangement of separators in an arrangement step, and FIG. 4( b) is a diagram for explaining the arrangement of a second resin frame in the arrangement step. FIG. 5 is a perspective view of a heat iron and a sheet member used in the temporary fixing step shown in FIG. 3. FIG. 6 is a diagram for explaining the temporary fixing step shown in FIG. 3. FIG. 7( a) is a diagram showing spot welding in the temporary fixing step according to a comparative example, and FIG. 7( b) is a diagram for explaining welded points in the temporary fixing step according to the comparative example. FIG. 8( a) is a diagram showing spot welding in the temporary fixing step according to an embodiment, and FIG. 8( b) is a diagram for explaining welded points in the temporary fixing step according to an embodiment. FIG. 9 is a diagram for explaining the stacking step shown in FIG. 3. FIG. 10 is a diagram for explaining the restraining step shown in FIG. 3. Fig. 11 is a diagram for explaining the end face welding process shown in Fig. 3. Fig. 12 is a diagram showing an example of spot welding using an adsorption plate. Fig. 13(a) is a diagram showing an example of a state before a hot iron is pressed against a sheet member when a tensioning mechanism is used. Fig. 13(b) is a diagram showing an example of a state after a hot iron is pressed against a sheet member when a tensioning mechanism is used. Fig. 14 is a diagram showing the state of spot welding in a temporary fixing process using a hot iron according to a modified example. Fig. 15 is a diagram showing the state of spot welding in a temporary fixing process using a hot iron according to another modified example.

[0015] Hereinafter, a preferred embodiment of a manufacturing method and welding apparatus for an energy storage module according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0016] 1 is a schematic cross-sectional view of an energy storage module 1 manufactured by a manufacturing method for an energy storage module 1 according to one embodiment. The energy storage module 1 is used as a battery for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The energy storage module 1 is a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. The energy storage module 1 may be an electric double layer capacitor or an all-solid-state battery. Here, a case where the energy storage module 1 is a lithium-ion secondary battery is illustrated as an example.

[0017] The energy storage module 1 includes an electrode stack 2 and a sealing portion 20. The electrode stack 2 includes a plurality of bipolar electrodes 11 stacked in a stacking direction D1, a positive terminal electrode 13, and a negative terminal electrode 12. That is, the electrode stack 2 is formed by stacking a plurality of bipolar electrodes 11 between the positive terminal electrode 13 and the negative terminal electrode 12. The sealing portion 20 is provided on the periphery of the electrode stack 2 and seals a plurality of spaces formed inside the electrode stack 2.

[0018] The bipolar electrode 11 includes an electrode foil 42, a positive electrode active material layer 44, and a negative electrode active material layer 43. When viewed from the stacking direction D1 (in a plan view), the electrode foil 42 has a four-sided rectangular shape. The negative electrode active material layer 43 is provided on a first surface 42a of the electrode foil 42. The positive electrode active material layer 44 is provided on a second surface 42b of the electrode foil 42 opposite the first surface 42a. That is, in the bipolar electrode 11, the first surface 42a of the electrode foil 42 functions as a negative electrode, and the second surface 42b of the electrode foil 42 functions as a positive electrode. Multiple bipolar electrodes 11 are stacked such that the positive electrode active material layer 44 of one bipolar electrode 11 faces the negative electrode active material layer 43 of another bipolar electrode 11. Here, as shown in FIG. 1 , the bipolar electrode 11 has a first surface 42 a of the electrode foil 42 facing the positive terminal electrode 13 side, and a second surface 42 b of the electrode foil 42 facing the negative terminal electrode 12 side.

[0019] The positive electrode active material layer 44 and the negative electrode active material layer 43 have a rectangular shape with four sides when viewed from the stacking direction D1. The negative electrode active material layer 43 is slightly larger than the positive electrode active material layer 44 when viewed from the stacking direction D1. That is, when viewed from the stacking direction D1, the outer edge of the positive electrode active material layer 44 is located more inward than the outer edge of the negative electrode active material layer 43. Furthermore, the electrode foil 42 is slightly larger than the negative electrode active material layer 43 and the positive electrode active material layer 44 when viewed from the stacking direction D1. That is, when viewed from the stacking direction D1, the outer edge of the electrode foil 42 is located more outward than the outer edge of the negative electrode active material layer 43 on the first surface 42a. As a result, an uncoated region 42a1 where the negative electrode active material layer 43 is not formed is formed on the first surface 42a so as to surround the outer edge of the negative electrode active material layer 43. Similarly, on the second surface 42b, the outer edge of the electrode foil 42 is located outside the outer edge of the positive electrode active material layer 44. As a result, on the second surface 42b, an uncoated region 42b1 where the positive electrode active material layer 44 is not formed is formed so as to surround the outer edge of the positive electrode active material layer 44.

[0020] The negative terminal electrode 12 has an electrode foil 42 and a negative electrode active material layer 43 provided on a first surface 42a of the electrode foil 42. The negative terminal electrode 12 does not have a positive electrode active material layer 44. That is, in the negative terminal electrode 12, no active material layer is provided on a second surface 42b of the electrode foil 42. The negative terminal electrode 12 is stacked on the bipolar electrode 11 at one end in the stacking direction D1. The negative terminal electrode 12 is stacked on the bipolar electrode 11 so that the negative electrode active material layer 43 faces the positive electrode active material layer 44 of the bipolar electrode 11. Therefore, the second surface 42b of the electrode foil 42 of the negative terminal electrode 12 faces outside the electrode stack 2 and serves as the negative electrode terminal surface of the energy storage module 1.

[0021] The positive terminal electrode 13 has an electrode foil 42 and a positive electrode active material layer 44 provided on a second surface 42b of the electrode foil 42. The positive terminal electrode 13 does not have a negative electrode active material layer 43. That is, in the positive terminal electrode 13, no active material layer is provided on a first surface 42a of the electrode foil 42. The positive terminal electrode 13 is laminated on the bipolar electrode 11 at the other end in the lamination direction D1. The positive terminal electrode 13 is laminated on the bipolar electrode 11 so that its positive electrode active material layer 44 faces the negative electrode active material layer 43 of the bipolar electrode 11. Therefore, the first surface 42a of the electrode foil 42 of the positive terminal electrode 13 faces outside the electrode stack 2 and serves as the positive electrode terminal surface of the energy storage module 1.

[0022] The electrode foil 42 is a chemically inactive electrical conductor that allows current to continue to flow through the positive electrode active material layer 44 and the negative electrode active material layer 43 during discharge or charge of the lithium ion secondary battery. The material of the electrode foil 42 is, for example, a metal material, a conductive resin material, or a conductive inorganic material. The conductive resin material is, for example, a conductive polymer material or a resin in which a conductive filler is added to a non-conductive polymer material. The electrode foil 42 may have multiple layers. In this case, each layer of the electrode foil 42 may contain the above-mentioned metal material or conductive resin material.

[0023] A coating layer may be formed on the electrode foil 42. The coating layer may be formed by a known method such as plating or spray coating. The electrode foil 42 may be, for example, in the form of a plate, foil, film, or mesh. The electrode foil 42 may be, for example, a metal foil. Examples of metal foils include aluminum foil, copper foil, nickel foil, titanium foil, and stainless steel foil. The electrode foil 42 may be an alloy foil of the above metals or a foil formed by integrating multiple metal foils. In this embodiment, the electrode foil 42 of the bipolar electrode 11 is a laminated foil formed by bonding a first electrode foil 421 and a second electrode foil 422 together via a conductive adhesive layer. The thickness of the first electrode foil 421 is thicker than the thickness of the second electrode foil 422. The thickness of the first electrode foil 421 is, for example, 30 μm to 100 μm. The thickness of the second electrode foil 422 is, for example, 5 μm to 10 μm. The first electrode foil 421 is, for example, an aluminum foil, and the second electrode foil 422 is, for example, a copper foil.

[0024] The positive electrode active material layer 44 contains a positive electrode active material capable of absorbing and releasing charge carriers such as lithium ions. Examples of the positive electrode active material include lithium composite metal oxides having a layered rock salt structure, metal oxides having a spinel structure, and polyanion compounds. The positive electrode active material may be any material that can be used in lithium ion secondary batteries. The positive electrode active material layer 44 may contain a plurality of positive electrode active materials. In this embodiment, the positive electrode active material layer 44 contains an olivine-type lithium iron phosphate (LiFePO ) as a composite oxide. ４ )

[0025] The negative electrode active material layer 43 includes a negative electrode active material capable of absorbing and releasing charge carriers such as lithium ions. The negative electrode active material may be a simple substance, an alloy, or a compound. Examples of the negative electrode active material include metallic lithium (Li), carbon, and metal compounds. The negative electrode active material may be an element or a compound thereof that can be alloyed with lithium. Examples of carbon include natural graphite, artificial graphite, hard carbon (non-graphitizable carbon), and soft carbon (easily graphitizable carbon). Examples of artificial graphite include highly oriented graphite and mesocarbon microbeads. Examples of elements that can be alloyed with lithium include silicon (Si) and tin. In this embodiment, the negative electrode active material layer 43 includes graphite as a carbon-based material.

[0026] Each of the positive electrode active material layer 44 and the negative electrode active material layer 43 (hereinafter sometimes simply referred to as "active material layer") may further contain, as necessary, a conductive additive for improving electrical conductivity, a binder, an electrolyte (polymer matrix, ion-conductive polymer, electrolyte solution, etc.), an electrolyte supporting salt (lithium salt) for improving ionic conductivity, etc. The conductive additive is added to improve the conductivity of each electrode (bipolar electrode 11, negative electrode terminal electrode 12, positive electrode terminal electrode 13). Examples of the conductive additive include acetylene black, carbon black, and graphite.

[0027] Examples of binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber; thermoplastic resins such as polypropylene and polyethylene; imide resins such as polyimide and polyamideimide; alkoxysilyl group-containing resins; acrylic resins such as acrylic acid and methacrylic acid; styrene-butadiene rubber (SBR); carboxymethyl cellulose; alginates such as sodium alginate and ammonium alginate; water-soluble cellulose ester crosslinked bodies; and starch-acrylic acid graft polymers. These binders may be used alone or in combination. Examples of solvents that may be used include water and N-methyl-2-pyrrolidone (NMP).

[0028] Separators 6 are disposed between adjacent bipolar electrodes 11, between the negative terminal electrode 12 and the bipolar electrode 11, and between the positive terminal electrode 13 and the bipolar electrode 11. The separators 6 are interposed between the positive electrode active material layer 44 and the negative electrode active material layer 43, which face each other in the stacking direction D1. The separators 6 separate the positive and negative electrodes, preventing short circuits due to contact between adjacent electrodes, while allowing charge carriers such as lithium ions to pass through. The positive electrode includes one electrode foil 42 and the positive electrode active material layer 44 formed on the second surface 42b of one electrode foil 42. The negative electrode includes the electrode foil 42 facing the positive electrode via the separator 6 and the negative electrode active material layer 43 formed on the first surface 42a of the opposing electrode foil 42.

[0029] The separator 6 may be, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains an electrolyte. Examples of materials for the separator 6 include polypropylene, polyethylene, polyolefin, and polyester. The separator 6 may have a single-layer structure or a multilayer structure. The multilayer structure may include, for example, a ceramic layer as an adhesive layer or a heat-resistant layer. The separator 6 may be impregnated with an electrolyte. The separator 6 may be composed of an electrolyte such as a polymer electrolyte or an inorganic electrolyte. Examples of the electrolyte impregnated in the separator 6 include a liquid electrolyte (electrolytic solution) containing a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent, and a polymer gel electrolyte containing an electrolyte retained in a polymer matrix.

[0030] When the separator 6 is impregnated with an electrolyte solution, the electrolyte salt may be LiFSI, LiClO ４ , LiAsF ６ , LiPF ６ , LiBF ４ , LiCF ３ SO ３ , LiN(FSO ２ ) ２ , LiN(CF ３ SO ２ ) ２Known lithium salts such as those listed above may be used. Furthermore, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers may be used as the nonaqueous solvent. Two or more of these known solvent materials may be used in combination.

[0031] The sealing unit 20 includes a first resin frame 41 and a second resin frame 5. The first resin frame 41 and the second resin frame 5 are each made of resin. The sealing unit 20 is bonded to the first surface 42a and the second surface 42b of each electrode foil 42 at the outer edge 42c of each electrode foil 42. The sealing unit 20 maintains a gap between adjacent electrode foils 42 so that a pair of adjacent electrode foils 42 in the stacking direction D1 do not contact each other. The sealing unit 20 seals each space S between adjacent electrode foils 42 in the stacking direction D1. That is, a space S is defined by the electrode foils 42 adjacent in the stacking direction D1 and the sealing unit 20. Each space S contains a positive electrode active material layer 44, a negative electrode active material layer 43, a separator 6, and an electrolyte. The electrolyte to be contained in the space S is injected into the space S through a through-hole 20a formed in the sealing unit 20 during the manufacturing process. The through-holes 20a are holes for injecting the electrolyte. After the electrolyte is accommodated in the space S, the through-holes 20a are finally sealed with a separate member. The sealing portion 20 prevents the electrolyte from permeating to the outside. The sealing portion 20 suppresses the intrusion of moisture and other substances into the space S from the outside of the energy storage module 1. The outer edge portion 6a of each separator 6 is fixed to the sealing portion 20. The sealing portion 20 contains an insulating material. Examples of resin materials that constitute the sealing portion 20 include various resin materials such as polypropylene, polyethylene, acid-modified polypropylene (acid-modified PP), acid-modified polyethylene (acid-modified PE), polystyrene, ABS resin, and acrylonitrile-styrene resin. The resin materials that constitute the first resin frame 41 and the second resin frame 5 may be the same or different.

[0032] The first resin frame 41 is joined to the first surface 42a and the second surface 42b of each electrode foil 42 at the outer edge 42c of each electrode foil 42. The first resin frame 41 is a rectangular frame-shaped member in a plan view. The first resin frame 41 is provided so as to extend from the first surface 42a of the electrode foil 42 through the outer edge 42d to the second surface 42b. In other words, the first resin frame 41 has a portion covering the outer edge 42c. The first resin frame 41 includes an overlapping portion 411 that overlaps the electrode foil 42 in the stacking direction D, and a protruding portion 412 that protrudes outward beyond the outer edge 42c of the electrode foil 42 and does not overlap the electrode foil 42 in the stacking direction D. The first resin frame 41 is welded to the first surface 42a and the second surface 42b of the electrode foil 42 at the overlapping portion 411. Examples of resin materials that can be used to form the first resin frame 41 include polypropylene, polyethylene, acid-modified polypropylene (acid-modified PP), acid-modified polyethylene (acid-modified PE), polystyrene, ABS resin, acrylonitrile-styrene resin, etc. The outer edge 6 a of the separator 6 may be fixed to the first resin frame 41 by welding.

[0033] The second resin frame 5 is disposed between adjacent first resin frames 41 in the stacking direction D1. The second resin frame 5 can also be referred to as a spacer. The first resin frames 41 and the second resin frames 5 are alternately stacked along the stacking direction D1. The second resin frame 5 is sandwiched between adjacent first resin frames 41. The second resin frame 5, together with adjacent first resin frames 41, defines a space S between adjacent electrode foils 42. The second resin frame 5 has a rectangular frame shape in plan view and includes an overlapping portion 51 that overlaps the electrode foil 42 in the stacking direction D1 and a protruding portion 52 that protrudes outward beyond the outer edge portion 42c of the electrode foil 42 and does not overlap the electrode foil 42 in the stacking direction D1. The second resin frame 5 is welded to each of a pair of adjacent first resin frames 41 in the stacking direction D1 at the edge of the protruding portion 52. The outer edge 6 a of the separator 6 may be sandwiched between the first resin frame 41 and the second resin frame 5 .

[0034] The welded end 7 is formed by integrally welding the end faces of the first resin frames 41 and the second resin frames 5 stacked in the stacking direction D1. The welded end 7 seals each of the spaces S by welding the outer edge 41 a of the first resin frame 41 to the outer edge 5 a of the second resin frame 5. The sealed outer edges 41 a and 5 a form the outer surface 7 s of the energy storage module 1. In this embodiment, the resin material forming the first resin frame 41 is acid-modified polyethylene or acid-modified polypropylene, and the resin material forming the second resin frame 5 is polyethylene or polypropylene. Acid-modified polyethylene and acid-modified polypropylene have properties that make them more easily adhere to metals than non-acid-modified polyethylene and non-acid-modified polypropylene. In this embodiment, in which the electrode foil 42 is made of a metal foil such as copper foil or aluminum foil, forming the first resin frame 41 from acid-modified polyethylene or acid-modified polypropylene can improve the adhesive strength (bonding strength) of the resin frame to the electrode foil. On the other hand, for the second resin frame 5 , which does not require adhesion to the electrode foil, inexpensive polyethylene or polypropylene is used, thereby reducing the cost of the energy storage module 1 .

[0035] The laminate 30 is formed, for example, by stacking a plurality of laminate units 3 in the stacking direction D1. FIG. 2( a) is a cross-sectional view of the laminate unit 3, and FIG. 2( b) is a plan view of the laminate unit 3. As shown in FIG. 2( a), the laminate unit 3 is a unit including a resin-framed electrode 4, a second resin frame 5, and a separator 6. Here, the resin-framed electrode 4 is formed by joining a first resin frame 41 to each electrode (bipolar electrode 11, negative electrode terminal electrode 12, positive electrode terminal electrode 13) that constitutes the electrode laminate 2. The resin-framed electrode 4 including the bipolar electrode 11 includes a first resin frame 41, an electrode foil 42, a negative electrode active material layer 43, and a positive electrode active material layer 44. The resin-framed electrode 4 including the negative electrode terminal electrode 12 includes a first resin frame 41, an electrode foil 42, and a negative electrode active material layer 43. The resin-framed electrode 4 including the positive terminal electrode 13 includes a first resin frame 41, an electrode foil 42, and a positive active material layer 44. In other words, the electrode foil 42 is a component of the bipolar electrode 11, the negative terminal electrode 12, and the positive terminal electrode 13, as well as a component of the laminate unit 3. The first surface 42a and the second surface 42b of the electrode foil 42 of each electrode constituting the electrode laminate 2 include coated regions where active material layers (positive active material layer 44 and negative active material layer 43) are formed, and uncoated regions 42a1 and 42b1 where no active material layers are formed. The uncoated regions 42a1 and 42b1 may be provided to surround the coated regions. The first resin frame 41 is welded to the first surface 42a and the second surface 42b of the electrode foil 42 in the uncoated regions 42a1 and 42b1 of the electrode foil 42.

[0036] As shown in Fig. 2(b), the second resin frame 5 and the first resin frame 41 are each formed in a frame shape. In the example of Fig. 2, the outer edge 5a of the second resin frame 5 and the outer edge 41a of the first resin frame 41 are aligned when viewed from the stacking direction D1. The outer edge 42d of the electrode foil 42 is located between the outer edge 41a of the first resin frame 41 and the inner edge 41b of the first resin frame 41. The outer edge 42d of the electrode foil 42 is also located between the outer edge 5a of the second resin frame 5 and the inner edge 5b of the second resin frame 5.

[0037] As shown in FIG. 2( b), the electrode foil 42 has a four-sided rectangular shape in a plan view. In the following description, for convenience of explanation, one in-plane direction of the electrode foil 42 perpendicular to the stacking direction D1 may be referred to as the vertical direction D2, and the other direction perpendicular to the stacking direction D1 and the vertical direction D2 may be referred to as the horizontal direction D3. One of the four sides of the electrode foil 42 is set as a reference side 42e. The reference side 42e serves as a reference position when stacking the stacked units 3 to form the stack 30. The second resin frame 5 includes a liquid inlet 5c at the reference side 42e. The liquid inlet 5c may be a recess that extends in the horizontal direction D3, which is perpendicular to the stacking direction D1, and is recessed in the stacking direction D1 so as to connect the outer edge 5a of the second resin frame 5 with the inner edge 5b of the second resin frame 5. The liquid inlet 5c may be a notch formed by cutting out a portion of the frame-shaped second resin frame 5 so that the inner edge 5b and the outer edge 5a are connected. In this case, the liquid inlet 5c may be formed to divide the second resin frame 5. As will be described in detail later, in the stacking process in which the stack units 3 are stacked to form the stack 30, a communication hole-forming member HM (see FIG. 9 ) described below is placed in the liquid inlet 5c. In the electrode stack 2, the first resin frame 41 of one of two stack units 3 adjacent to each other in the stacking direction D1 covers the liquid inlet 5c of the other stack unit 3, thereby forming the above-mentioned through hole 20a in the sealing portion 20. After the stacking process, the end face of the sealing portion 20 is welded with the communication hole-forming member HM placed in the through hole 20a. After the end faces are welded, the through-hole forming member HM is pulled out from the end faces, whereby an injection port for injecting an electrolyte into the space S formed between adjacent electrode foils 42 is formed in the end face of the sealing portion 20 .

[0038] 2( a) shows the laminate unit 3 including the bipolar electrode 11, but the energy storage module 1 also includes a laminate unit including a positive terminal electrode 13 and a laminate unit including a negative terminal electrode 12. Compared to the laminate unit 3, the laminate unit including the positive terminal electrode 13 differs from the laminate unit 3 in that the negative electrode active material layer 43 is not formed on the first surface 42 a of the electrode foil 42 and that it does not include the second resin frame 5 and the separator 6, but the rest is the same. The laminate unit including the negative terminal electrode 12 differs from the laminate unit 3 only in that the positive electrode active material layer 44 is not formed on the second surface 42 b of the electrode foil 42, but the rest is the same. Below, the laminate unit 3 including the bipolar electrode 11 will be described as an example.

[0039] Next, one embodiment of a method for manufacturing the energy storage module 1 will be described. FIG. 3 is a flowchart showing one step of the method for manufacturing the energy storage module 1. In this manufacturing method, first, a resin-framed electrode 4 is prepared by welding a first resin frame 41 to an outer edge portion 42 c of an electrode foil 42 provided with a positive electrode active material layer 44 and a negative electrode active material layer 43 (preparation step). Then, a resin-framed second resin frame 5 is placed on the first resin frame 41 of the resin-framed electrode 4 (placement step ST1). FIGS. 4( a) and 4(b) are views for explaining the placement step ST1. As shown in FIG. 4( a), in the placement step ST1, a separator 6 is first placed on the resin-framed electrode 4. At this time, the outer edge (end surface) 6 b of the separator 6 is positioned between the inner edge 41 b of the first resin frame 41 and the outer edge 42 d of the electrode foil 42, as viewed from the stacking direction D1, and is fixed to the first resin frame 41. 4(b), the second resin frame 5 is placed on the first resin frame 41 of the resin-framed electrode 4. At this time, the outer edge 6a of the separator 6 may be sandwiched between the second resin frame 5 and the first resin frame 41.

[0040] Next, the first resin frame 41 and the second resin frame 5 are temporarily fixed by spot welding to produce a resin-framed electrode 4 with the second resin frame 5 temporarily fixed (temporary fixing step ST2). In the temporary fixing step ST2, a welding device 10 and a sheet member 9 are used for spot welding. Figure 5 is a perspective view of the welding device 10 and the sheet member 9. The welding device 10 is equipped with a heat iron 8. The heat iron 8 has, for example, a cylindrical main body 8c and a tip 8a that tapers from the main body 8c toward a tip surface 8b.

[0041] The sheet member 9 has excellent heat resistance and thermal conductivity and exhibits high releasability with respect to the resin to be welded. The sheet member 9 may be, for example, glass cloth, a sheet-like member made of glass fiber. The glass cloth may be, for example, glass fiber impregnated with a fluorine-based compound. Impregnating the glass cloth with a fluorine-based compound sufficiently enhances the releasability of the sheet member 9 from the second resin frame 5 after spot welding. Meanwhile, glass fiber has a higher thermal conductivity than fluorine-based compounds, which prevents the heat applied from the hot iron 8 to the second resin frame 5 from being blocked by the sheet member 9. The sheet member 9 is not limited to the glass cloth described above, and any known release sheet may be used. For example, the sheet member 9 may be a multilayer film including a heat-resistant base layer and a release layer formed on the surface of the base layer. Here, the base layer may be, for example, CFRP or polypropylene. The release layer may be, for example, a fluororesin, polystyrene resin, or silicone resin. In this embodiment, a manufacturing method using glass cloth as the sheet member 9 will be described.

[0042] In the temporary fixing step ST2, the sheet member 9 is placed over a wider area than the tip 8a of the hot iron 8. Here, the area of ​​the sheet member 9 is set to, for example, several times to several tens of times the area of ​​the tip surface 8b, and the center of the sheet member 9 is aligned with the center of the tip 8a of the hot iron 8. As a result, the sheet member 9 is placed between the tip 8a of the hot iron 8 and the second resin frame 5 so that the outer edge of the tip surface 8b and the outer edge of the main body 8c are within the area of ​​the sheet member 9 when viewed from the stacking direction D1.

[0043] When arranging the sheet member 9, tension may be applied to the sheet member 9. There are no particular limitations on the method of applying tension, but the sheet member 9 may be spanned across a pair of support members (not shown) and tension may be applied to the sheet member 9 outside the pair of support members to apply tension in the in-plane direction (the in-plane direction of the surface of the second resin frame 5) to the sheet member 9 between the pair of support members. For example, tension may be applied to the portion of the sheet member 9 where the hot iron 8 abuts by pulling both ends of the sheet member 9 in the direction opposite to the direction in which the hot iron 8 is pressed against the sheet member 9 (the direction toward the second resin frame 5).

[0044] In the temporary fixing step ST2, as shown in FIG. 6 , the first resin frame 41 and the second resin frame 5 are spot-welded from the second resin frame 5 side via the sheet member 9 described above. Various arrangements can be used for the arrangement of the sheet member 9 between the tip 8a of the hot iron 8 and the second resin frame 5. For example, the sheet member 9 may be placed on the second resin frame 5, and the hot iron 8 may be pressed against the sheet member 9 on the second resin frame 5. Alternatively, the sheet member 9 may be brought into contact with the tip surface 8b of the hot iron 8 in advance, and the tip surface 8b with the sheet member 9 in contact may be pressed against the second resin frame 5. In either arrangement, the sheet member 9 may be in intimate contact with the surface of the second resin frame 5 when the tip surface 8b of the hot iron 8 is pressed against the surface.

[0045] The spot welding between the first resin frame 41 and the second resin frame 5 via the sheet member 9 is performed at least on the reference edge 42e. For the three edges other than the reference edge 42e, the first resin frame 41 and the second resin frame 5 may be spot-welded by pressing the hot iron 8 directly against the second resin frame 5 without using the sheet member 9. In this case, the welded areas that are welded without using the sheet member 9 may be cut and removed all at once after the stacked units 3 are stacked and before the sealing process is performed.

[0046] In this embodiment, the position of spot welding between the first resin frame 41 and the second resin frame 5 via the sheet member 9 is in region R between the outer edge 42d of the electrode foil 42 and the outer edge 6b of the separator 6 when viewed from the stacking direction D1. The position of spot welding may be anywhere within region R. For example, the position of spot welding may be the center of region R, a position in region R closer to the outer edge 42d of the electrode foil 42, or a position in region R closer to the outer edge 6b of the separator 6.

[0047] The position of the spot welding between the first resin frame 41 and the second resin frame 5 via the sheet member 9 may be outside of region R when viewed from the stacking direction D1. Specifically, the position of the spot welding between the first resin frame 41 and the second resin frame 5 via the sheet member 9 may be the protruding portion 52 of the second resin frame 5 and the protruding portion 412 of the first resin frame 41 when viewed from the stacking direction D1. When spot welding is performed outside of region R, the first resin frame 41 and the second resin frame 5 may be spot-welded from the first resin frame 41 side via the sheet member 9. For example, the sheet member 9 may be placed on the first resin frame 41, and the hot iron 8 may be pressed against the sheet member 9 on the first resin frame 41. Alternatively, the sheet member 9 may be brought into contact with the tip surface 8b of the hot iron 8 in advance, and the tip surface 8b in contact with the sheet member 9 may be pressed against the first resin frame 41.

[0048] Spot welding within region R can reduce adverse effects on the sealing of the energy storage module 1 compared to spot welding outside region R. As will be described in detail later, when spot welding the first resin frame 41 and the second resin frame 5 is performed by pressing a hot iron 8 against the second resin frame 5 from the second resin frame 5 side via a sheet member 9, the generation of large burrs around the welded points on the second resin frame 5 can be suppressed. However, even if burrs are not generated, there is a risk of minute irregularities occurring in the area including the welded points. For example, when spot welding is performed at an end near the outer edge 5a of the second resin frame 5 (outside region R), such minute irregularities will occur at the end of the second resin frame 5. The minute irregularities occurring at the end of the second resin frame 5 can cause a decrease in the welding quality of the welded end 7 formed by welding the outer edge 41a of the first resin frame 41 to the outer edge 5a of the second resin frame 5. Therefore, in the end face welding process, when welding the outer edges 41a of the first resin frame 41 and the outer edges 5a of the second resin frame 5 in adjacent stacking units 3 in the stacking direction D1, in order to reduce the adverse effect that the welding points for temporarily fixing the resin members have on the sealing properties of the energy storage module 1, it is more appropriate to perform spot welding within a region R that is sufficiently separated from the part where the end faces are welded.

[0049] In the temporary fixing step ST2, when the tip 8a of the hot iron 8 is pressed directly against the surface of the second resin frame 5 as in the conventional method, the heat from the hot iron 8 melts the resin constituting the second resin frame 5, as shown in FIG. 7( a). In the conventional example, the molten resin bulges along the outer surface of the tip 8a of the hot iron 8 pressed against the second resin frame 5. Then, as shown in FIG. 7( b), the bulged resin cools and hardens, generating burrs B protruding from the surface of the second resin frame 5 around the welding points HP of the second resin frame 5. If the laminated units 3 are stacked with burrs B generated at the welding points HP of the second resin frame 5, gaps due to the burrs may occur between the second resin frame 5 and the first resin frame 41 between adjacent laminated units 3 in the stacking direction. The accumulation of these gaps in the stacking direction may result in deviations from the design values ​​of the dimensions of the laminate 30 in the stacking direction D1. If the dimension of the stacking direction D1 of the laminate 30 deviates from the design value, the restraint pressure in the stacking direction applied to the laminate 30 in subsequent processes such as end face welding (welding the outer edges of the second resin frame 5 and the first resin frame 41) will be uneven, leading to poor sealing of the laminate 30.

[0050] In contrast, in the present embodiment, when a sheet member 9 is placed between the tip 8a of the hot iron 8 and the second resin frame 5 in the temporary fixing step ST2, the heat from the hot iron 8 melts the resin constituting the second resin frame 5, as shown in FIG. 8( a). In this embodiment, the molten resin flows along the surface 9a of the sheet member 9 (the surface opposite to the surface in contact with the tip surface 8b) that is in close contact with the surface of the second resin frame 5. Because the sheet member 9 is placed between the tip 8a of the hot iron 8 and the second resin frame 5, which is a resin member, the tip 8a of the hot iron 8 is prevented from sinking into the molten second resin frame 5, and the resin is prevented from bulging due to the pressure of the hot iron 8. As a result, as shown in FIG. 8( b), the generation of burrs B around the welding point HP of the second resin frame 5 can be suppressed.

[0051] After the temporary fixing step ST2, as shown in FIG. 9 , a plurality of resin-framed electrodes 4 with the second resin frames 5 temporarily fixed thereto are stacked as a single laminate unit 3 to form a laminate 30 (lamination step ST3). In the lamination step ST3, a communication hole-forming member HM is placed in the liquid injection port 5c formed in the second resin frame 5 of each laminate unit 3. Then, with the communication hole-forming member HM placed in the liquid injection port 5c, the laminate units 3 are stacked. The communication hole-forming member HM is, for example, a metal plate whose surface is coated with PTFE (polytetrafluoroethylene). In the lamination step ST3, first, a resin-framed electrode 4 including a negative electrode terminal electrode 12 is placed at one end in the stacking direction D1. Next, a plurality of resin-framed electrodes 4 including a bipolar electrode 11 are stacked on the resin-framed electrode 4 including the negative electrode terminal electrode 12. Finally, a resin-framed electrode 4 including a positive electrode terminal electrode 13 is placed on the plurality of stacked resin-framed electrodes 4 including the bipolar electrode 11. The resin-framed electrode 4 including the positive terminal electrode 13 is disposed at the other end in the stacking direction D1.

[0052] In this embodiment, the laminated units 3 are stacked with the reference edge 42e described above aligned as a stacking reference. Because the through-hole-forming member HM is not present on sides other than the reference edge 42e, a portion of the protruding portion 52 of the second resin frame 5 and the protruding portion 412 of the first resin frame 41 may be removed as excess after stacking. The laminated units 3 are stacked on the reference edge 42e, including the spot-welded portions of the first resin frame 41 and the second resin frame 5. In this embodiment, because the generation of burrs B around the welded points HP is suppressed in the temporary fixing step ST2 described above, the generation of gaps due to burrs B between adjacent resin-framed electrodes 4 in the stacking direction D1 is suppressed in the electrode laminate 2 obtained by stacking.

[0053] Next, the stack 30 is restrained in the stacking direction D1 of the stack unit 3 (restraint step S4). In the restraint step ST4, as shown in FIG. 10 , the stack 30 is restrained by sandwiching it between a pair of restraint plates 15A and 15B from both ends in the stacking direction D1. Specifically, one restraint plate 15A is disposed on the positive terminal electrode 13 side, and the other restraint plate 15B is disposed on the negative terminal electrode 12 side, and a predetermined restraint pressure is applied between the restraint plates 15A and 15B. The pair of restraint plates 15A and 15B have, for example, a rectangular shape when viewed from the stacking direction D1. As an example, the outer edge 5 a of the second resin frame 5 and the outer edge 41 a of the first resin frame 41 may be located outside the outer edges 15 a of the pair of restraint plates 15A and 15B (on the opposite side from the electrode foil 42). Alternatively, outer edges 15a of the pair of restraint plates 15A, 15B may coincide with outer edges 42d of electrode foil 42. In the lamination step ST3, gaps due to burrs B between the second resin frame 5 and the first resin frame 41 are suppressed, and therefore, in the restraint step ST4, between adjacent laminated units 3, sufficient adhesion can be ensured between the first resin frame 41 of one laminated unit 3 and the second resin frame 5 of another laminated unit.

[0054] After the stack 30 is restrained, the outer edges 41 a of the first resin frames 41 and the outer edges 5 a of the second resin frames 5 in stack units 3 adjacent to each other in the stacking direction D1 are welded together (edge ​​welding step ST5). In the edge welding step ST5, as shown in FIG. 11 , the edge faces of the stack 30 (the outer edges 41 a of the first resin frames 41 and the outer edges 5 a of the second resin frames 5) are heated by a heat source HS. When viewed from the stacking direction D1, the stack 30 has four faces defined by the outer edges 41 a of the first resin frames 41 and the outer edges 5 a of the second resin frames 5. In the edge welding step ST5, the four faces of the stack 30 are heated by the heat source HS. In this step, all four faces may be heated simultaneously, pairs of faces may be heated simultaneously, or faces may be heated one by one. The heat source HS may be composed of four heat sources corresponding to each face of the laminate 30 when viewed from the stacking direction D1, or may be configured to surround the periphery of the laminate 30. In the edge welding process ST5, the heat sources HS are arranged at a predetermined interval from each face of the laminate 30. Heating by the heat source HS may be radiant heating using an infrared heater. Alternatively, for the three faces including the three sides other than the reference edge 42e, heating may be performed by pressing a heat source HS such as a hot plate directly against the end face. This melts the outer edge 41a of the first resin frame 41 and the outer edge 5a of the second resin frame 5 adjacent to each other in the stacking direction, and the outer edges 41a of the first resin frame 41 and the outer edges 5a of the second resin frame 5 adjacent to each other in the stacking direction are welded to each other. Furthermore, as described above, in the restraining step ST4, sufficient adhesion between the first resin frame 41 and the second resin frame 5 between adjacent stacked units 3 can be ensured, thereby achieving good welding between the outer edges 41 a of the first resin frame 41 and the outer edges 5 a of the second resin frame 5, and effectively suppressing poor sealing of the electrode stack 2. In the end face welding step ST5, the plurality of first resin frames 41 and the plurality of second resin frames 5 are integrated to form welded end portions 7, and the energy storage module 1 is manufactured.

[0055] As described above, in the manufacturing method for the energy storage module 1 according to one aspect of the present disclosure, in the temporary fixing step ST2, the first resin frame 41 and the second resin frame 5 are spot-welded via the sheet member 9 placed at the tip 8a of the hot iron 8. With this method, when the resin constituting the first resin frame 41 or the second resin frame 5 is melted by the heat from the hot iron 8, the molten resin flows along the surface 9a of the sheet member 9, preventing the resin from bulging due to the pressure of the hot iron 8. This allows the resin to cool and harden in a flattened state, preventing burrs from occurring at the welding point HP.

[0056] The manufacturing method for the energy storage module 1 further includes a restraining step ST4 in which the stack 30 is restrained in the stacking direction D1 of the stacked unit 3 and a restraining load is applied to the first resin frame 41 and the second resin frame 5 aligned in the stacking direction D1, and an end face welding step ST5 in which, with the restraining load applied, the outer edges of the first resin frame 41 and the second resin frame 5 adjacent in the stacking direction D1 are welded together. With this configuration, burrs are suppressed at the weld points HP between the first resin frame 41 and the second resin frame 5 in the temporary fixing step ST2, and as a result, sufficient adhesion between the first resin frame 41 and the second resin frame 5 between adjacent stacked units 3 can be ensured in the restraining step ST4. Therefore, in the end face welding step ST5, the outer edges 41 a of the first resin frame 41 and the outer edges 5 a of the second resin frame 5 are well welded together, effectively suppressing poor sealing of the stack 30.

[0057] In the temporary fixing step ST2, the tip 8a of the hot iron 8 is pressed against the first resin frame 41 or the second resin frame 5 while tension is applied to the sheet member 9. This configuration makes it possible to prevent the sheet member 9 from bending when the molten resin flows along the surface 9a of the sheet member 9. This maintains the flatness of the resin and more reliably prevents burrs from occurring at the welding point HP.

[0058] In this manufacturing method for the energy storage module 1, the resin-framed electrode 4 has a rectangular shape having four sides in a plan view, one of which is set as a reference side 42e. In the arrangement process ST1, the second resin frame 5 is arranged so that the side on which the liquid inlet portion 5c is formed overlaps the reference side 42e. In the temporary fixing process ST2, the first resin frame 41 and the second resin frame 5 are spot-welded via the sheet member 9 at least along the reference side 42e. In the stacking process ST3, the stacked units 3 are stacked while aligning the reference side 42e as a stacking reference. When the reference side 42e is set on the resin-framed electrode 4 and the stacked units 3 are stacked with the reference side 42e aligned, portions of the sides other than the reference side 42e that include the spot-welded portions of the first resin frame 41 and the second resin frame 5 can be removed as excess portions before stacking, but portions of the reference side 42e that include the spot-welded portions of the first resin frame 41 and the second resin frame 5 must be left. Therefore, by spot welding the first resin frame 41 and the second resin frame 5 via the sheet member 9 at least at the reference edge 42e and suppressing the occurrence of burrs at the welding point HP, it is possible to suitably ensure adhesion between the first resin frame 41 and the second resin frame 5 between adjacent stacked units 3.

[0059] In the arrangement step ST1, before arranging the second resin frame 5, the separator 6 is placed on the resin-framed electrode 4, and then the outer edge 6a of the separator 6 is fixed to the first resin frame 41. In the temporary fixing step ST2, the first resin frame 41 and the second resin frame 5 are spot-welded via the sheet member 9 in the region between the outer edge 42d of the electrode foil 42 and the outer edge 6b of the separator 6, as viewed from the stacking direction D1. With this configuration, it is possible to suppress the occurrence of burrs at the welding points HP between the first resin frame 41 and the second resin frame 5, taking into consideration the positional relationship of the separator 6 with respect to the resin-framed electrode 4.

[0060] A welding device according to one aspect of the present disclosure includes a hot iron 8 for spot welding resin members (a first resin frame 41 and a second resin frame 5), with a sheet member 9 attached to the tip 8a of the hot iron 8. Assume, for example, that the welding device is used to spot weld two overlapping resin members (the first resin frame 41 and the second resin frame 5) from the upper resin member (the second resin frame 5). In this case, the tip 8a of the hot iron 8 is provided with a sheet member 9 that is wider than the tip 8a. As a result, when the resin constituting the upper resin member (the second resin frame 5) is melted by heat from the hot iron 8, the molten resin member flows along the surface 9a of the sheet member 9, preventing the resin member from protruding due to the application of the hot iron 8. This allows the resin members to cool and harden in a flattened state, preventing burrs from forming at the welding point HP.

[0061] Although the embodiments of the present disclosure have been described above, the present disclosure is not necessarily limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0062] In the temporary fixing step ST2, the first resin frame 41 and the second resin frame 5 may be spot-welded via the sheet member 9 along at least one of the three sides other than the reference side 42e, as with the reference side 42e. All of the three sides other than the reference side 42e may be spot-welded via the sheet member 9. Of the three sides other than the reference side 42e, one side may be spot-welded via the sheet member 9, and the remaining two sides may be spot-welded by directly abutting the tip end 8a against the second resin frame 5 without using the sheet member 9.

[0063] In the temporary fixing step ST2, tension does not necessarily need to be applied to the sheet member 9. For example, a sheet-like sheet member 9 may be placed on the second resin frame 5, and a hot iron 8 may be pressed against the sheet member 9 to spot weld it. In the stacking step ST3, a plurality of stacked units 3 may be stacked as a single unit to form the electrode stack 2. For example, after the temporary fixing ST2, three stacked units 3 may be temporarily fixed to each other along the stacking direction D1, and in the stacking step ST3, the three stacked units 3 may be stacked as a single unit.

[0064] In the placement step ST1, the second resin frame 5 may be adsorbed by a suction plate. Fig. 12 is a diagram showing an example of spot welding using a suction plate 60. In the example of Fig. 12, in the placement step ST1, the second resin frame 5 is adsorbed by the suction plate 60, and the second resin frame 5 is placed on the first resin frame 41. Then, in the temporary fixing step ST2, with the second resin frame 5 adsorbed to the suction plate 60, the first resin frame 41 and the second resin frame 5 are temporarily fixed by spot welding via the suction plate 60.

[0065] The suction plate 60 has a rectangular shape with four sides in a plan view. The suction plate 60 is made of, for example, metal. The suction plate 60 includes, for example, a suction pad and an air pipe (not shown). The air pipe draws in and exhausts air from within the suction pad, thereby attaching and detaching the second resin frame 5, which is disposed opposite the suction pad, to the suction plate 60. In the example of FIG. 12 , the outer edge of the suction plate 60 is located outside the outer edge 41 a of the first resin frame 41 and the outer edge 5 a of the second resin frame 5, but it may also coincide with the outer edge 41 a of the first resin frame 41 and the outer edge 5 a of the second resin frame 5.

[0066] The suction plate 60 includes multiple notches 60a on the side corresponding to the reference side 42e (see FIG. 2(b)). The multiple notches 60a expose the second resin frame 5 in a plan view. The multiple notches 60a extend in the horizontal direction D3 from the side corresponding to the reference side 42e. Tips of the multiple notches 60a may be located closer to the inner edge 5b of the second resin frame 5 than the outer edge 6b of the separator 6 (see FIG. 2(b)). In the temporary fixing step ST3, the suction plate 60 suctions the second resin frame 5 so that the positions of spot welding via the multiple notches 60a are in the region R (see FIG. 6) between the outer edge 42d of the electrode foil 42 (see FIG. 2(b)) and the outer edge 6b of the separator 6. The multiple notches 60a may be arranged evenly or unevenly in the vertical direction D2. In either case, the suction plate 60 suctions the second resin frame 5 so that the multiple notches 60a are positioned on both sides of the liquid pouring port 5c. In the example of Fig. 12, the two notches 60a are positioned so as to sandwich the liquid pouring port 5c therebetween.

[0067] The suction plate 60 includes multiple notches 60b along the sides corresponding to the three sides excluding the reference side 42e. The multiple notches 60b expose the second resin frame 5 in a plan view. The multiple notches 60b extend in the horizontal direction D3 or the vertical direction D2 from the sides corresponding to the three sides excluding the reference side 42e. In the example of FIG. 12 , the tips of the multiple notches 60b are located closer to the outer edge 41a of the first resin frame 41 than the outer edge 42d of the electrode foil 42. The welding regions on the three sides excluding the reference side 42e may be cut and removed all at once before the sealing process. Therefore, in the temporary fixing process ST3, the suction plate 60 does not necessarily need to suction the second resin frame 5 so that the position of the spot welding via the multiple notches 60b is in region R.

[0068] In the temporary fixing step ST2, a tension applying mechanism may be used to apply tension to the sheet member 9. FIG. 13A is a diagram illustrating an example of a case in which a tension applying mechanism 90 is used, before the hot iron 8 is pressed against the sheet member 9. The tension applying mechanism 90 includes a pair of first support rollers 91 and 92, a second support roller 93, a third support roller 94, a sheet feed roller 95, and a sheet take-up roller 96. In the tension applying mechanism 90, the sheet member 9 fed from the sheet feed roller 95 is transported in the transport direction A1, passes through the pair of first support rollers 91 and 92, the second support roller 93, and the third support roller 94, and is then taken up by the sheet take-up roller 96. The sheet member 9 contacts the outer peripheries of the pair of first support rollers 91 and 92, the second support roller 93, and the third support roller 94, thereby transporting the sheet member 9 under a certain tension. Between the pair of first support rollers 91, 92, the sheet member 9 is stretched across the heat iron 8. The sheet member 9 is stretched so as to leave a gap between the sheet member 9 and the surface of the second resin frame 5. Tension is applied to the sheet member 9 between the pair of first support rollers 91, 92 in the in-plane direction (the in-plane direction of the surface of the second resin frame 5).

[0069] 13(b) is a diagram showing an example of the state after the hot iron 8 is pressed against the sheet member 9 when the tensioning mechanism 90 is used. In the temporary fixing step ST2, with tension applied to the sheet member 9 between the pair of first support rollers 91, 92, the hot iron 8 is pressed against the second resin frame 5 via the sheet member 9. At this time, as shown in FIG. 13(b), tension is applied to the sheet member 9 not only in the in-plane direction but also in the direction in which the hot iron 8 is pressed. This makes it even easier to suppress deflection of the sheet member 9 during temporary fixing.

[0070] The sheet member 9 may not be used in the temporary fixing step ST2. In the temporary fixing step ST2, the tip of a hot iron may be pressed against the first resin frame 41 or the second resin frame 5 to spot-weld the first resin frame 41 and the second resin frame 5. In the temporary fixing step ST2, a modified hot iron 8A as shown in FIG. 14 may be used instead of the hot iron 8. The hot iron 8A has a heat-generating portion 81 and a protective portion 82 that covers the heat-generating portion. The heat-generating portion 81 has, for example, a cylindrical main body 81c and a tip portion 81a that tapers from the main body 81c toward a tip surface 81b. The protective portion 82 has, for example, a cylindrical main body 82c and a tip portion 82a that tapers from the main body 82c toward a tip surface 82b. The main body portion 81c of the heat generating portion 81 is located inside the main body portion 82c of the protective portion 82. When viewed from the stacking direction D1, the center of the main body portion 81c coincides with the center of the main body portion 82c. The protective portion 82 may be configured to be slightly shorter than the heat generating portion 81 so that the tip surface 81b of the heat generating portion 81 protrudes from the tip surface 82b, or may be configured so that the tip surface 82b of the protective portion 82 and the tip surface 81b of the heat generating portion 81 are flush with each other. The center of the tip surface 82b coincides with the center of the tip surface 81b. The protective portion 82 is made of a material that has high heat resistance and lower thermal conductivity than metals such as aluminum and copper. The protective portion 82 may be made of, for example, a ceramic material with low thermal conductivity. This makes it difficult for heat from the heat generating portion 81 to be absorbed by the protective portion 82, allowing heat to be sufficiently transferred to the second resin frame 5.

[0071] 14, in the temporary fixing step ST2 when the hot iron 8A is used, the tip 81a of the heat-generating portion 81 and the tip 82a of the protective portion 82 are pressed directly against the second resin frame 5. By pressing the second resin frame 5 around the welding point HP with the protective portion 82, the molten resin flows along the surface of the protective portion 82, preventing the resin from bulging due to the pressure of the heat-generating portion 81. This maintains the flatness of the resin and prevents burrs from occurring at the welding point HP.

[0072] The hot iron 8A may be used together with the sheet member 9. In this case, in the temporary fixing step ST2, the sheet member 9 may be placed on the second resin frame 5, and the leading end surface 81b of the heat generating portion 81 and the leading end surface 82b of the protective portion 82 may be pressed against the sheet member 9. Alternatively, the sheet member 9 may be brought into contact with the leading end surfaces 81b and 82b in advance, and the leading end surfaces 81b and 82b in contact with the sheet member 9 may then be pressed against the second resin frame 5. In either embodiment, when the leading end surfaces 81b and 82b are pressed against the surface of the second resin frame 5, the sheet member 9 may be in close contact with the surface of the second resin frame 5.

[0073] Instead of the hot iron 8A, a hot iron 8B having an annular cap member 83 fixed around the tip 8a of the hot iron 8 may be used, as shown in FIG. 15 . As shown in FIG. 15 , the hot iron 8B may be used together with a sheet member 9. The cap member 83 is an annular member including a through-hole 83a. The cap member 83 is made of a resin material with high heat resistance and low thermal conductivity. The cap member 83 may be made of Teflon (registered trademark) resin, for example. In the temporary fixing process ST2, temporary fixing is performed using the hot iron 8B to which the cap member 83 is attached so that the tip surface 8b is exposed from the through-hole 83a. In the temporary fixing process ST2, the sheet member 9 may be placed on the second resin frame 5, and the tip 8a may be pressed against the sheet member 9 while the cap member 83 is abutted against the sheet member 9 around the tip 8a. Alternatively, the sheet member 9 may be brought into contact with the tip surface 8b of the hot iron 8 in advance, and the tip surface 8b in contact with the sheet member 9 may be pressed against the second resin frame 5. In either case, when the tip surface 8b of the hot iron 8B is pressed against the second resin frame 5, the sheet member 9 can be brought into close contact with the surface of the second resin frame 5. This maintains the flatness of the resin and prevents burrs from occurring at the welding point HP.

[0074] The hot iron 8B does not have to be used together with the sheet member 9. In the temporary fixing step ST2, the tip 8a of the hot iron 8B may be pressed against the first resin frame 41 or the second resin frame 5 to spot-weld the first resin frame 41 and the second resin frame 5. In the temporary fixing step ST2, the tip 8a may be pressed against the second resin frame 5 while the cap member 83 is abutted against the resin member around the tip 8a. In this case, the molten resin flows along the surface of the cap member 83, preventing the resin from bulging due to the pressing of the hot iron 8.

[0075] The gist of the present disclosure is as follows: [1] to [6]: [1] A method for manufacturing an energy storage module, comprising: a preparation step of welding a first resin frame to an outer edge of an electrode foil having an active material layer provided thereon to prepare a resin-framed electrode; an arrangement step of overlaying a second resin frame on the first resin frame of the resin-framed electrode; a temporary fixing step of temporarily fixing the first resin frame and the second resin frame that have been overlaid in the arrangement step by spot welding using a hot iron; and a lamination step of stacking a plurality of the resin-framed electrodes with the second resin frame temporarily fixed thereto as a single laminate unit to form a laminate, wherein in the temporary fixing step, a sheet member is placed between a tip of the hot iron and the first resin frame or the second resin frame, and the first resin frame and the second resin frame are spot-welded via the sheet member. [2] The method for manufacturing an electric storage module according to [1], further comprising: a restraining step of restraining the stack in a stacking direction of the stacked unit and applying a restraining load to the first resin frame and the second resin frame aligned in the stacking direction, and an end face welding step of welding outer edges of the first resin frame and the second resin frame adjacent to each other in the stacking direction while the restraining load is applied. [3] The method for manufacturing an electric storage module according to [1] or [2], further comprising: a restraining step of restraining the stack in a stacking direction of the stacked unit and applying a restraining load to the first resin frame and the second resin frame aligned in the stacking direction, and an end face welding step of welding outer edges of the first resin frame and the second resin frame adjacent to each other in the stacking direction while the restraining load is applied. [4] The method for manufacturing an energy storage module according to any one of [1] to [3], wherein the resin-framed electrode has a rectangular shape having four sides in a planar view, and one of the four sides is set as a reference side, and in the arranging step, the second resin frame is arranged so that the side on which the liquid inlet portion is formed overlaps the reference side, and in the temporary fixing step, the first resin frame and the second resin frame are spot-welded via the sheet member at least at the reference side, and in the stacking step, the stacked units are stacked while aligning the reference side as a stacking reference.[5] The method for manufacturing an electric storage module according to any one of [1] to [4], wherein in the positioning step, a separator is placed on the resin-framed electrode before the second resin frame is placed, and then an outer edge of the separator is fixed to the first resin frame, and in the temporary fixing step, spot welding of the first resin frame and the second resin frame is performed via the sheet member in an area between the outer edge of the electrode foil and the outer edge of the separator as viewed from the stacking direction of the stacked unit. [6] A welding device comprising a heat iron for spot welding resin members together, and a sheet member having a wider area than the tip of the heat iron is provided at the tip of the heat iron.

[0076] 1...energy storage module, 2...electrode laminate, 3...lamination unit, 4...electrode with resin frame, 5...second resin frame, 5a...outer edge of second resin frame, 6...separator, 6a...outer edge of separator, 6b...outer edge of separator, 8...heat iron, 8a...tip, 9...sheet member, 10...welding device, 30...laminate, 41...first resin frame, 41a...outer edge of first resin frame, 42...electrode foil, 42c...outer edge of electrode foil, 42d...outer edge of electrode foil, 42e...reference side, D1...stacking direction, ST1...arrangement process, ST2...temporary fixing process, ST3...stacking process, ST4...restraint process, ST5...end face welding process.

Claims

1. A method for manufacturing an energy storage module, comprising: a preparation step of welding a first resin frame to an outer edge of an electrode foil having an active material layer provided thereon to prepare a resin-framed electrode; an arrangement step of overlapping and arranging a second resin frame on the first resin frame of the resin-framed electrode; a temporary fixing step of temporarily fixing the first resin frame and the second resin frame that have been overlapped in the arrangement step by spot welding using a hot iron; and a lamination step of stacking a plurality of the resin-framed electrodes to which the second resin frame has been temporarily fixed as one lamination unit to form a laminate, wherein in the temporary fixing step, a sheet member is placed between the tip of the hot iron and the first resin frame or the second resin frame, and the first resin frame and the second resin frame are spot welded via the sheet member.

2. A method for manufacturing an energy storage module as described in claim 1, further comprising: a restraining step of restraining the stack in the stacking direction of the stacked unit and applying a restraining load to the first resin frame and the second resin frame aligned in the stacking direction; and an end face welding step of welding together outer edges of the first resin frame and the second resin frame adjacent in the stacking direction while the restraining load is applied.

3. A method for manufacturing a storage module as described in claim 1 or 2, wherein in the temporary fixing process, the tip of the hot iron is pressed against the first resin frame or the second resin frame while tension is applied to the sheet member.

4. A method for manufacturing an energy storage module according to any one of claims 1 to 3, wherein the resin-framed electrode has a rectangular shape having four sides in a plan view, one of the four sides being set as a reference side, wherein in the positioning step, the second resin frame is positioned so that the side on which the liquid injection port portion is formed overlaps the reference side, wherein in the temporary fixing step, the first resin frame and the second resin frame are spot-welded via the sheet member at least at the reference side, and wherein in the stacking step, the stacked units are stacked while aligning the reference side as a stacking reference.

5. A method for manufacturing an energy storage module as described in any one of claims 1 to 4, wherein in the arrangement step, before arranging the second resin frame, a separator is placed on top of the resin-framed electrode, and then an outer edge portion of the separator is fixed to the first resin frame, and in the temporary fixing step, spot welding of the first resin frame and the second resin frame is performed via the sheet member in a region between the outer edge of the electrode foil and the outer edge of the separator when viewed from the stacking direction of the stacked unit.

6. A welding device comprising a hot iron for spot welding resin members together, the tip of the hot iron being provided with a sheet member having a larger area than the tip.

Images