Method for manufacturing energy storage modules and welding apparatus

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

Technical Field

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

Background Art

[0002] As a conventional method for manufacturing an electricity storage module, there is the method described in Patent Document 1, for example. 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 being pressurized, thereby forming a bipolar electrode unit (welding step). Thereafter, a plurality of bipolar electrode units are stacked along the stacking direction to form an electrode stacked body (stacking step). After forming the electrode stacked body, the stacked resin frames are welded to each other to seal the electrode stacked body (sealing step).

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problem to be Solved by the Invention

[0004] In the electricity storage module manufactured by the above-described manufacturing method, as described in Patent Document 2, for example, a resin spacer may be further stacked on the resin frame welded to the electrode plate to form a stacked unit. When arranging such a spacer, in order to prevent positional displacement between the resin frame and the spacer during the subsequent stacking step, it is conceivable to temporarily fix the spacer to the resin frame at the stage when the spacer is arranged on the resin frame. The temporary fixing of the spacer to the resin frame is performed, for example, by spot-welding the spacer to the resin frame using a hot iron or the like.

[0005] When spacers and resin frames are spot-welded using a hot iron, the generation of burrs at the welded area becomes a problem. If burrs are present at the welded area of ​​the spacer when the laminated units are stacked, gaps will form between the spacer and the resin frame in adjacent laminated units in the stacking direction due to the burrs. As a result, there is a risk of sealing defects occurring in the electrode laminate after the sealing process has been carried out.

[0006] The purpose of this disclosure is to provide a method for manufacturing an energy storage module and a welding apparatus that can suppress the generation of burrs at the welding points where resin components are temporarily fixed together. [Means for solving the problem]

[0007] In a method for manufacturing an energy storage module according to one aspect of this disclosure, in the temporary fixing step, the first resin frame and the second resin frame are spot-welded together via a sheet member placed on the tip of a hot iron. With this method, 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, suppressing the bulging of the resin caused by the pressure of the hot iron. As a result, the resin cools and hardens in a flattened state, and the generation of burrs at the welding points where the resin members are temporarily fixed together is suppressed.

[0008] The manufacturing method for this energy storage module further comprises a restraining step of restraining the laminate in the stacking direction of the stacked unit and applying a restraining load to the first and second resin frames aligned in the stacking direction, and an end-face welding step of welding the outer edges of adjacent first and second resin frames in the stacking direction together while the restraining load is applied. With this configuration, burrs at the welding points between the first and second resin frames are suppressed in the temporary fixing step, and as a result, sufficient adhesion between the first and second resin frames between adjacent stacked units can be ensured in the restraining step. Therefore, in the end-face welding step, the welding between the outer edges of the first and second resin frames is good, and sealing defects of the laminate can be effectively suppressed.

[0009] In the temporary fixing process, tension is applied to the sheet member, and the tip of the hot iron is pressed towards the first or second resin frame. This configuration suppresses the bending of the sheet member as the molten resin flows along its surface. Therefore, the flatness of the resin is maintained, and the generation of burrs at the welding point can be more reliably suppressed.

[0010] In this method for manufacturing energy storage modules, the electrode with a resin frame has a rectangular shape with four sides in plan view, and one of these four sides is set as the reference side. In the placement step, the side of the second resin frame on which the liquid injection port is formed is placed so as to overlap with the reference side. In the temporary fixing step, spot welding is performed on the first resin frame and the second resin frame via a sheet member at least on the reference side. In the lamination step, the laminated units are stacked while aligning the reference side as the stacking reference. When setting a reference side for the electrode with a resin frame and stacking the laminated units while aligning the reference side, the parts including the spot-welded areas of the first and second resin frames on sides other than the reference side can be removed as excess parts before lamination, but the parts including the spot-welded areas of the first and second resin frames on the reference side must be left intact. Therefore, by performing spot welding of the first resin frame and the second resin frame via a sheet member at least along the reference edge, and suppressing the generation of burrs at the welding points, the adhesion between the first resin frame and the second resin frame between adjacent laminated units can be suitably ensured.

[0011] In the placement process, before placing the second resin frame, the separator is placed on top of the electrode with the resin frame, and then the outer edge of the separator is fixed to the first resin frame. In the temporary fixing process, spot welding of the first and second resin frames via a sheet member is performed in the region between the outer edge of the electrode foil and the outer edge of the separator, as viewed from the lamination direction. With this configuration, the generation of burrs at the welding point between the first and second resin frames can be suppressed while taking into account the placement relationship of the separator with respect to the electrode with the resin frame.

[0012] A welding apparatus according to one aspect of this disclosure includes a hot iron for spot welding resin members (a first resin frame and a second resin frame), and a sheet member with a wider surface area than the tip is provided at the tip of the hot iron. Let's consider a case where, for example, two resin members (a first resin frame and a second resin frame) are stacked on top of each other, and spot welding is performed on the upper resin member (the second resin frame). In this case, a sheet member is provided at the tip of the hot iron. As a result, when the resin constituting the upper resin member (the second resin frame) melts due to the heat from the hot iron, the molten resin flows along the surface of the sheet member, suppressing the bulging of the resin member caused by the pressure of the hot iron. As a result, the resin member cools and hardens in a flattened state, and the generation of burrs at the welding point is suppressed. [Effects of the Invention]

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

[0014] [Figure 1] Figure 1 is a schematic cross-sectional view of an energy storage module manufactured by a method for manufacturing an energy storage module according to one embodiment. [Figure 2] Figure 2(a) is a cross-sectional view of the laminated unit, and Figure 2(b) is a plan view of the laminated unit. [Figure 3] Figure 3 is a flowchart showing one step in the manufacturing process of an energy storage module. [Figure 4] Figure 4(a) is a diagram illustrating the arrangement of the separators in the placement process, and Figure 4(b) is a diagram illustrating the arrangement of the second resin frame in the placement process. [Figure 5] Figure 5 is a perspective view of the hot iron and sheet material used in the temporary fixing process shown in Figure 3. [Figure 6] Figure 6 is a diagram illustrating the temporary fixing process shown in Figure 3. [Figure 7]FIG. 7(a) is a diagram showing the state of spot welding in the temporary fixing step according to a comparative example, and FIG. 7(b) is a diagram for explaining the welding points in the temporary fixing step according to the comparative example. [Figure 8] FIG. 8(a) is a diagram showing the state of spot welding in the temporary fixing step according to an embodiment, and FIG. 8(b) is a diagram for explaining the welding points in the temporary fixing step according to the embodiment. [Figure 9] FIG. 9 is a diagram for explaining the stacking step shown in FIG. 3. [Figure 10] FIG. 10 is a diagram for explaining the constraining step shown in FIG. 3. [Figure 11] FIG. 11 is a diagram for explaining the end surface welding step shown in FIG. 3. [Figure 12] FIG. 12 is a diagram showing an example of spot welding using a suction plate. [Figure 13] FIG. 13(a) is a diagram showing an example before pressing a hot iron against a sheet member when a tension applying mechanism is used. FIG. 13(b) is a diagram showing an example after pressing the hot iron against the sheet member when the tension applying mechanism is used. [Figure 14] FIG. 14 is a diagram showing the state of spot welding in the temporary fixing step using a hot iron according to a modified example. [Figure 15] FIG. 15 is a diagram showing the state of spot welding in the temporary fixing step using a hot iron according to another modified example. DETAILED DESCRIPTION OF THE INVENTION

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

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

[0017] The energy storage module 1 comprises an electrode stack 2 and a sealing portion 20. The electrode stack 2 includes a plurality of bipolar electrodes 11 stacked in the 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 comprises an electrode foil 42, a positive electrode active material layer 44, and a negative electrode active material layer 43. The electrode foil 42 has a rectangular shape with four sides when viewed from the stacking direction D1 (in a plan view). The negative electrode active material layer 43 is provided on a first surface 42a, which is one of the surfaces of the electrode foil 42. The positive electrode active material layer 44 is provided on a second surface 42b, which is the surface of the electrode foil 42 opposite to the first surface 42a. That is, the bipolar electrode 11 is an electrode in which the first surface 42a of the electrode foil 42 functions as the negative electrode and the second surface 42b of the electrode foil 42 functions as the positive electrode. Multiple bipolar electrodes 11 are stacked so 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 Figure 1, the bipolar electrode 11 has a first surface 42a of the electrode foil 42 facing the positive terminal electrode 13, and a second surface 42b of the electrode foil 42 facing the negative terminal electrode 12.

[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. In other words, when viewed from the stacking direction D1, the outer edge of the positive electrode active material layer 44 is located inward from the outer edge of the negative electrode active material layer 43. Also, the electrode foil 42 is slightly larger than both the negative electrode active material layer 43 and the positive electrode active material layer 44 when viewed from the stacking direction D1. In other words, when viewed from the stacking direction D1, on the first surface 42a, the outer edge of the electrode foil 42 is located outward from the outer edge of the negative electrode active material layer 43. As a result, on the first surface 42a, an uncoated region 42a1 is formed where the negative electrode active material layer 43 is not formed, surrounding 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 is formed where the positive electrode active material layer 44 is not formed, surrounding the outer edge of the positive electrode active material layer 44.

[0020] The negative electrode terminal electrode 12 has an electrode foil 42 and a negative electrode active material layer 43 provided on the first surface 42a of the electrode foil 42. The negative electrode terminal electrode 12 does not have a positive electrode active material layer 44. In other words, in the negative electrode terminal electrode 12, there is no active material layer on the second surface 42b of the electrode foil 42. The negative electrode terminal electrode 12 is laminated on the bipolar electrode 11 at one end in the lamination direction D1. The negative electrode terminal electrode 12 is laminated on the bipolar electrode 11 such that its 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 electrode terminal electrode 12 faces outward from the electrode laminate 2 and is 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 the second surface 42b of the electrode foil 42. The positive terminal electrode 13 does not have a negative electrode active material layer 43. In other words, the positive terminal electrode 13 does not have an active material layer on the 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 such 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 outward from the electrode laminate 2 and is the positive terminal surface of the energy storage module 1.

[0022] The electrode foil 42 is a chemically inert 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 the discharge or charging 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 has been added to a non-conductive polymer material. The electrode foil 42 may consist of 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. This coating layer may be formed by known methods such as plating or spray coating. The electrode foil 42 may be in the form of a plate, foil, film, or mesh. The electrode foil 42 may be a metal foil, for example. Examples of metal foils include aluminum foil, copper foil, nickel foil, titanium foil, or stainless steel foil. The electrode foil 42 may be an alloy foil of the above metals or a foil in which multiple of the above metal foils are integrated. 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 greater 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, aluminum foil. The second electrode foil 422 is, for example, copper foil.

[0024] The positive electrode active material layer 44 contains a positive electrode active material capable of intercalating and releasing charge carriers such as lithium ions. Examples of positive electrode active materials include lithium composite metal oxides having a layered rock salt structure, metal oxides having a spinel structure, and polyanionic compounds. The positive electrode active material can be any material suitable for use in lithium-ion secondary batteries. The positive electrode active material layer 44 may contain multiple positive electrode active materials. In this embodiment, the positive electrode active material layer 44 contains olivine-type lithium iron phosphate (LiFePO4) as a composite oxide.

[0025] The negative electrode active material layer 43 contains a negative electrode active material capable of intercalating and releasing charge carriers such as lithium ions. The negative electrode active material may be an element, an alloy, or a compound. Examples of negative electrode active materials include metallic lithium (Li), carbon, and metal compounds. The negative electrode active material may also be an element or compound thereof that can be alloyed with lithium. Examples of carbon include natural graphite, artificial graphite, hard carbon (carbon that is difficult to graphitize), or soft carbon (carbon that is easily graphitized). Examples of artificial graphite include highly oriented graphite and mesocarbon microbeads. Examples of elements that can be alloyed with lithium include silicon (Si) or tin. In this embodiment, the negative electrode active material layer 43 contains 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 the "active material layer") may further contain, as necessary, conductive additives, binders, electrolytes (polymer matrix, ion-conducting polymer, electrolyte solution, etc.), electrolyte-supporting salts (lithium salts) to enhance ionic conductivity, etc. Conductive additives are added to enhance the conductivity of each electrode (bipolar electrode 11, negative electrode terminal electrode 12, positive electrode terminal electrode 13). Examples of conductive additives include acetylene black, carbon black, or graphite.

[0027] Examples of binders include fluororesins 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 or methacrylic acid; styrene-butadiene rubber (SBR); alginates such as carboxymethylcellulose, sodium alginate, and ammonium alginate; water-soluble cellulose ester crosslinked polymers; and starch-acrylic acid graft polymers. These binders can be used individually or in combination. Examples of solvents include water and N-methyl-2-pyrrolidone (NMP).

[0028] The separator 6 is positioned between adjacent bipolar electrodes 11, between the negative electrode terminal electrode 12 and the bipolar electrode 11, and between the positive electrode terminal electrode 13 and the bipolar electrode 11. The separator 6 is interposed between the positive electrode active material layer 44 and the negative electrode active material layer 43 facing each other in the stacking direction D1. The separator 6 is a component that allows charge carriers such as lithium ions to pass through while preventing short circuits caused by contact between adjacent electrodes by isolating the positive electrode and the negative electrode. Here, 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 an 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 electrolytes. 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 electrolytes impregnated into the separator 6 include a liquid electrolyte (electrolyte solution) containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent, or a polymer gel electrolyte containing an electrolyte held in a polymer matrix.

[0030] When the separator 6 is impregnated with an electrolyte, known lithium salts such as LiFSI, LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, and LiN(CF3SO2)2 may be used as the electrolyte salt. Furthermore, known solvents such as cyclic carbonates, cyclic esters, linear carbonates, linear esters, and ethers may be used as the non-aqueous solvent. Two or more of these known solvent materials may be used in combination.

[0031] The sealing portion 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 material. The sealing portion 20 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 sealing portion 20 maintains the spacing between adjacent electrode foils 42 so that adjacent pairs of electrode foils 42 in the stacking direction D1 do not come into contact with each other. The sealing portion 20 seals each of the spaces S between adjacent electrode foils 42 in the stacking direction D1. That is, the space S is defined by the adjacent electrode foils 42 in the stacking direction D1 and the sealing portion 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 contained in the space S is injected into the space S through a through hole 20a formed in the sealing portion 20 during the manufacturing process. The through-hole 20a is a hole for injecting the electrolyte. After the electrolyte is contained in the space S, the through-hole 20a is finally sealed with a separate component. The sealing part 20 prevents the electrolyte from permeating to the outside. The sealing part 20 suppresses the intrusion of moisture and other substances from the outside of the energy storage module 1 into the space S. The outer edge 6a of each separator 6 is fixed to the sealing part 20. The sealing part 20 contains an insulating material. Examples of resin materials that constitute the sealing part 20 include polypropylene, polyethylene, acid-modified polypropylene (acid-modified PP), acid-modified polyethylene (acid-modified PE), polystyrene, ABS resin, acrylonitrile styrene resin, and various other resin materials. The resin material that constitutes the first resin frame 41 and the resin material that constitutes 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 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 that covers the outer edge 42c. The first resin frame 41 includes an overlapping portion 411 that overlaps with the electrode foil 42 in the lamination direction D, and an overhanging portion 412 that extends outward from the outer edge 42c of the electrode foil 42 and does not overlap with the electrode foil 42 in the lamination 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 constitute the first resin frame 41 include polypropylene, polyethylene, acid-modified polypropylene (acid-modified PP), acid-modified polyethylene (acid-modified PE), polystyrene, ABS resin, and acrylonitrile styrene resin. The outer edge 6a of the separator 6 may be welded and fixed to the first resin frame 41.

[0033] The second resin frame 5 is positioned between adjacent first resin frames 41 in the lamination direction D1. The second resin frame 5 can also be described as a spacer. The first resin frames 41 and the second resin frame 5 are stacked alternately along the lamination direction D1. The second resin frame 5 is sandwiched between adjacent first resin frames 41. Together with the adjacent first resin frames 41, the second resin frame 5 defines the space S formed between adjacent electrode foils 42. In plan view, the second resin frame 5 has a rectangular frame shape and includes an overlapping portion 51 that overlaps with the electrode foil 42 in the lamination direction D1, and a protruding portion 52 that extends outward from the outer edge portion 42c of the electrode foil 42 and does not overlap with the electrode foil 42 in the lamination direction D1. The second resin frame 5 is welded to each of the pair of adjacent first resin frames 41 in the lamination direction D1 at the edge of the protruding portion 52. The outer edge 6a 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 welding together the end faces of multiple first resin frames 41 and multiple second resin frames 5 that are stacked in the stacking direction D1. The welded end 7 seals multiple spaces S by welding together the outer edge 41a of the first resin frame 41 and the outer edge 5a of the second resin frame 5. The sealed outer edges 41a and 5a constitute the outer surface 7s of the energy storage module 1. In this embodiment, the resin material constituting the first resin frame 41 is acid-modified polyethylene or acid-modified polypropylene, and the resin material constituting the second resin frame 5 is polyethylene or polypropylene. Acid-modified polyethylene and acid-modified polypropylene have properties that make them easier to adhere to metals compared to un-acid-modified polyethylene and un-acid-modified polypropylene. In this embodiment, where the electrode foil 42 is made of metal foil such as copper foil or aluminum foil, the adhesive strength (joining strength) of the resin frame to the electrode foil can be improved by constructing the first resin frame 41 from acid-modified polyethylene or acid-modified polypropylene. On the other hand, in the second resin frame 5, which does not require adhesion to the electrode foil, the cost of the energy storage module 1 can be reduced by using inexpensive polyethylene or polypropylene.

[0035] The laminate 30 is formed, for example, by stacking multiple laminate units 3 in the stacking direction D1. Figure 2(a) is a cross-sectional view of the laminate unit 3, and Figure 2(b) is a plan view of the laminate unit 3. As shown in Figure 2(a), the laminate unit 3 is a unit in which a resin-framed electrode 4, a second resin frame 5, and a separator 6 constitute a single unit. 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 constitute 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 electrode 4 with a resin frame, including the positive terminal electrode 13, comprises 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 laminated 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 a coated region where the active material layer (positive active material layer 44 and negative active material layer 43) is formed, and uncoated regions 42a1, 42b1 where the active material layer is not formed. The uncoated regions 42a1, 42b1 may be provided so as to surround the coated region. 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, 42b1 of the electrode foil 42.

[0036] As shown in Figure 2(b), the second resin frame 5 and the first resin frame 41 are each formed in a frame shape. In the example in Figure 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 lamination 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. Also, the outer edge 42d of the electrode foil 42 is 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 Figure 2(b), the electrode foil 42 has a rectangular shape with four sides in a plan view. In the following explanation, for convenience of explanation, one direction of the electrode foil 42 perpendicular to the lamination direction D1 may be called the vertical direction D2, and the other direction perpendicular to the lamination direction D1 and the vertical direction D2 may be called the horizontal direction D3. In the electrode foil 42, one of the four sides of the electrode foil 42 is set as the reference side 42e. The reference side 42e is the reference position when laminating the lamination units 3 to form the laminate 30. The second resin frame 5 includes a liquid injection port 5c at the reference side 42e. The liquid injection port 5c may be a recess that extends in the horizontal direction D3, which is perpendicular to the lamination direction D1, so as to connect the outer edge 5a and the inner edge 5b of the second resin frame 5, and is also recessed in the lamination direction D1. The liquid injection port portion 5c may be a notch formed by cutting out a part of the frame-shaped second resin frame 5 so that the inner edge 5b and the outer edge 5a are in communication. In that case, the liquid injection port portion 5c may be formed so as to divide the second resin frame 5. As will be described in detail later, in the lamination process in which the lamination units 3 are stacked to form the laminate 30, the communication hole forming member HM (see Figure 9), described later, is placed in the liquid injection port portion 5c. In the electrode laminate 2, the liquid injection port portion 5c of the other lamination unit 3 is covered by the first resin frame 41 of the lamination unit 3 located in one of the two adjacent lamination units 3 in the lamination direction D1, thereby forming the above-mentioned through hole 20a in the sealing portion 20. After the lamination process, with the communication hole forming member HM placed in the through hole 20a, the end face of the sealing portion 20 is welded. After end face welding, the communication hole forming member HM is pulled out from the end face, thereby forming an injection port on the end face of the sealing portion 20 for injecting electrolyte into the space S formed between adjacent electrode foils 42.

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

[0039] Next, an embodiment of a method for manufacturing the energy storage module 1 will be described. Figure 3 is a flowchart showing one step in the method for manufacturing the energy storage module 1. In this manufacturing method, first, a resin frame 41 made of resin is welded to the outer edge 42c of the electrode foil 42, which is provided with a positive electrode active material layer 44 and a negative electrode active material layer 43, to prepare an electrode with a resin frame 4 (preparation step). Then, a second resin frame 5 made of resin is placed on the first resin frame 41 of the electrode with a resin frame 4 (placement step ST1). Figures 4(a) and 4(b) are diagrams illustrating the placement step ST1. As shown in Figure 4(a), in the placement step ST1, first, a separator 6 is placed on the electrode with a resin frame 4. At that time, the outer edge (end face) 6b of the separator 6 is positioned between the inner edge 41b of the first resin frame 41 and the outer edge 42d of the electrode foil 42, as viewed from the stacking direction D1, and fixed to the first resin frame 41. Next, as shown in Figure 4(b), the second resin frame 5 is placed on top of the first resin frame 41 of the electrode 4 with a resin frame. 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 create an electrode 4 with a resin frame, in which the second resin frame 5 is temporarily fixed (temporary fixing step ST2). In 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 hot iron 8. The hot iron 8 has, for example, a cylindrical body portion 8c and a tip portion 8a that tapers from the body portion 8c toward the tip surface 8b.

[0041] The sheet member 9 is a member that has excellent heat resistance and thermal conductivity and high release properties from the resin to be welded. As the sheet member 9, for example, glass cloth, which is a sheet-like member made of glass fibers, is used. The glass cloth may be made of glass fibers impregnated with a fluorine-based compound, for example. By impregnating the glass cloth with a fluorine-based compound, the release properties of the sheet member 9 from the second resin frame 5 after spot welding can be sufficiently improved. On the other hand, since glass fibers have a higher thermal conductivity than fluorine-based compounds, the heat applied from the hot iron 8 to the second resin frame 5 can be prevented from being obstructed by the sheet member 9. The sheet member 9 is not limited to the glass cloth described above, and known release sheets can 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, fluororesin, polystyrene resin or silicone resin. In this embodiment, a manufacturing method when glass cloth is used as the sheet member 9 will be described.

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

[0043] When arranging the sheet member 9, tension may be applied to the sheet member 9. There are no particular restrictions on the method of applying tension, but tension may be applied to the sheet member 9 between the pair of support members in the in-plane direction (in the in-plane direction of the surface of the second resin frame 5) by bridging the sheet member 9 over a pair of support members (not shown) and applying tensile tension to the sheet member 9 outside of the pair of support members. For example, tensile tension may be applied to the part of the sheet member 9 that the hot iron 8 contacts by pulling both ends of the sheet member 9 in the opposite direction to the direction in which the hot iron 8 is pressed against the sheet member 9 (towards the second resin frame 5).

[0044] In the temporary fixing step ST2, as shown in Figure 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 configurations can be adopted for the arrangement of the sheet member 9 between the tip 8a of the soldering 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 soldering 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 soldering 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 any of these configurations, when the tip surface 8b of the soldering iron 8 is pressed against the second resin frame 5, the sheet member 9 may be in close contact with the surface of the second resin frame 5.

[0045] Spot welding of 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 sides other than the reference edge 42e, spot welding of the first resin frame 41 and the second resin frame 5 may be performed by directly pressing the hot iron 8 against the second resin frame 5 without using the sheet member 9. In that case, the welded area that was welded without using the sheet member 9 may be cut and removed all at once after the lamination of the lamination unit 3 but before the sealing process is performed.

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

[0047] The location of the point welding between the first resin frame 41 and the second resin frame 5 via the sheet member 9 may be outside the region R when viewed from the lamination direction D1. Specifically, the location of the point 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 lamination direction D1. When point welding is performed outside the region R, the first resin frame 41 and the second resin frame 5 may be point-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 soldering 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 soldering 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] When spot welding is performed within region R, the adverse effect on the sealing performance of the energy storage module 1 can be reduced compared to spot welding outside region R. As will be described in detail later, when spot welding is performed between the first resin frame 41 and the second resin frame 5 by pressing the hot iron 8 toward the second resin frame 5 from the second resin frame 5 side via the sheet member 9, the generation of large burrs around the welding point of the second resin frame 5 can be suppressed. However, even if burrs are not generated, there is a risk that the region including the welding point will have minute irregularities. For example, when spot welding is performed at an end close to 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. These minute irregularities at the end of the second resin frame 5 will 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 and 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 laminated units 3 in the lamination direction D1, it is more suitable to perform spot welding in a region R sufficiently separated from the part to be end-face welded in order to minimize the adverse effect of the welding points used to temporarily fix the resin members on the sealing performance of the energy storage module 1.

[0049] In the temporary fixing process ST2, if 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 resin constituting the second resin frame 5 melts due to the heat from the hot iron 8, as shown in Figure 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. Subsequently, as shown in Figure 7(b), as the bulged resin cools and hardens, a burr B is generated around the welding point HP of the second resin frame 5, protruding from the surface of the second resin frame 5. If the laminated units 3 are stacked with burr B present at the welding point HP of the second resin frame 5, a gap due to the burr may occur between the second resin frame 5 and the first resin frame 41 in adjacent laminated units 3 in the stacking direction. As this gap accumulates in the stacking direction, the dimension of the laminated body 30 in the stacking direction D1 may deviate from the design value. If the dimension of the laminate 30 in the lamination direction D1 deviates from the design value, the restraining pressure applied to the laminate 30 in the lamination direction during subsequent processes such as end face welding (welding of the outer edges of the second resin frame 5 and the first resin frame 41) will become uneven, leading to poor sealing of the laminate 30.

[0050] In contrast, as in this embodiment, when the sheet member 9 is placed between the tip 8a of the soldering iron 8 and the second resin frame 5 in the temporary fixing step ST2, the resin constituting the second resin frame 5 melts due to the heat from the soldering iron 8, as shown in Figure 8(a). In this embodiment, the molten resin flows along the surface 9a of the sheet member 9 that is in close contact with the surface of the second resin frame 5 (the surface opposite to the surface in contact with the tip surface 8b). At this time, because the sheet member 9 is placed between the tip 8a of the soldering iron 8 and the second resin frame 5, which is a resin material, the tip 8a of the soldering iron 8 is prevented from sinking into the molten second resin frame 5, and the bulging of the resin due to the pressure of the soldering iron 8 is suppressed. As a result, as shown in Figure 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 Figure 9, a laminate 30 is formed by stacking multiple resin-framed electrodes 4, each with a second resin frame 5 temporarily fixed, as a single laminate unit 3 (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 coated with PTFE (polytetrafluoroethylene) on its surface. In the lamination step ST3, first, a resin-framed electrode 4 including a negative electrode terminal electrode 12 is placed at one end of the lamination direction D1. Subsequently, multiple resin-framed electrodes 4 including bipolar electrodes 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 multiple stacked resin-framed electrodes 4 including bipolar electrodes 11. The electrode 4 with a resin frame, including the positive terminal electrode 13, will be positioned at the other end in the stacking direction D1.

[0052] In this embodiment, each laminated unit 3 is laminated with the above-described reference side 42e aligned as the lamination reference. On sides other than the reference side 42e, since there is no communication hole forming member HM, a portion of the protruding part 52 of the second resin frame 5 and the protruding part 412 of the first resin frame 41 may be removed as excess after lamination. On the reference side 42e, the laminated unit 3 is laminated including the point welding locations of the first resin frame 41 and the second resin frame 5. In this embodiment, since the generation of burrs B around the welding point 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 lamination direction D1 is suppressed in the electrode laminate 2 obtained by lamination.

[0053] Next, the laminate 30 is restrained in the stacking direction D1 of the stacking unit 3 (restraint step S4). In restraint step ST4, as shown in Figure 10, the laminate 30 is restrained by sandwiching it from both ends in the stacking direction D1 with a pair of restraint plates 15A and 15B. Specifically, one restraint plate 15A is placed on the positive terminal electrode 13 side, and the other restraint plate 15B is placed 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 5a of the second resin frame 5 and the outer edge 41a of the first resin frame 41 may be located outside the outer edge 15a of the pair of restraint plates 15A and 15B (on the opposite side from the electrode foil 42). Alternatively, the outer edges 15a of the pair of restraint plates 15A and 15B may coincide with the outer edge 42d of the electrode foil 42. In the lamination process ST3, the gap caused by burrs B between the second resin frame 5 and the first resin frame 41 is suppressed, so in the restraint process ST4, sufficient adhesion between the first resin frame 41 of one lamination unit 3 and the second resin frame 5 of another lamination unit can be ensured between adjacent lamination units 3.

[0054] After the laminate 30 is restrained, the outer edges 41a of the first resin frame 41 and the outer edges 5a of the second resin frame 5 in adjacent laminate units 3 in the lamination direction D1 are welded together (end face welding process ST5). In the end face welding process ST5, as shown in Figure 11, the end faces of the laminate 30 (the outer edges 41a of the first resin frame 41 and the outer edges 5a of the second resin frame 5) are heated by a heat source HS. When viewed from the lamination direction D1, the laminate 30 has four faces formed by the outer edges 41a of the first resin frame 41 and the outer edges 5a of the second resin frame 5. In the end face welding process ST5, the four faces of the laminate 30 are heated by a heat source HS. At that time, the four faces may be heated simultaneously, a pair of faces may be heated simultaneously, or one face may be heated sequentially. The heat source HS may consist of four heat sources corresponding to each face of the laminate 30 when viewed from the lamination direction D1, or it may be configured to surround the perimeter of the laminate 30. In the end face welding process ST5, the heat sources HS are placed at predetermined intervals from each face of the laminate 30. Heating by the heat sources HS may be done by radiant heating using an infrared heater. Alternatively, for three faces including the three sides other than the reference side 42e, a heat source HS such as a hot plate may be pressed directly against the end face for heating. As a result, 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 lamination direction melt, 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 lamination direction are welded together. Furthermore, as mentioned above, in the restraining process ST4, sufficient adhesion between the first resin frame 41 and the second resin frame 5 between adjacent laminated units 3 is ensured, resulting in good welding between the outer edges 41a of the first resin frame 41 and the outer edges 5a of the second resin frame 5, effectively suppressing sealing defects of the electrode laminate 2. In the end face welding process ST5, the multiple first resin frames 41 and the multiple second resin frames 5 are integrated to form a welded end 7, and the energy storage module 1 is manufactured.

[0055] As described above, in the method for manufacturing the energy storage module 1 according to one aspect of this disclosure, in the temporary fixing step ST2, the first resin frame 41 and the second resin frame 5 are spot-welded together via a sheet member 9 placed on 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 melts due to the heat from the hot iron 8, the molten resin flows along the surface 9a of the sheet member 9, suppressing the bulging of the resin caused by the pressure of the hot iron 8. As a result, the resin cools and hardens in a flattened state, and the generation of burrs at the welding point HP is suppressed.

[0056] The manufacturing method for the energy storage module 1 further comprises a restraining step ST4 in which the laminate 30 is restrained in the stacking direction D1 of the laminate unit 3 and a restraining load is applied to the first resin frame 41 and the second resin frame 5 which are aligned in the stacking direction D1, and an end face welding step ST5 in which the outer edges of the first resin frame 41 and the second resin frame 5 adjacent to each other in the stacking direction D1 are welded together while the restraining load is applied. With this configuration, burrs at the welding point HP between the first resin frame 41 and the second resin frame 5 are suppressed 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 laminate units 3 can be ensured in the restraining step ST4. Therefore, in the end face welding step ST5, the welding between the outer edge 41a of the first resin frame 41 and the outer edge 5a of the second resin frame 5 is good, and sealing defects of the laminate 30 can be effectively suppressed.

[0057] In the temporary fixing process ST2, tension is applied to the sheet member 9, and the tip 8a of the hot iron 8 is pressed toward the first resin frame 41 or the second resin frame 5. This configuration suppresses the bending of the sheet member 9 as the molten resin flows along the surface 9a of the sheet member 9. Therefore, the flatness of the resin is maintained, and the generation of burrs at the welding point HP can be suppressed more reliably.

[0058] In the manufacturing method of this energy storage module 1, the resin-framed electrode 4 has a rectangular shape with four sides in plan view, and one of these four sides is set as the reference side 42e. In the arrangement step ST1, the side of the second resin frame 5 on which the liquid injection port 5c is formed is placed so as to overlap with the reference side 42e. In the temporary fixing step ST2, spot welding of the first resin frame 41 and the second resin frame 5 via the sheet member 9 is performed at least on the reference side 42e. In the lamination step ST3, the lamination units 3 are stacked while aligning the reference side 42e as the lamination reference. When setting the reference side 42e on the resin-framed electrode 4 and stacking the lamination units 3 while aligning the reference side 42e, the parts including the spot-welded areas of the first resin frame 41 and the second resin frame 5 on sides other than the reference side 42e can be removed as excess parts before lamination, but on the reference side 42e, it is necessary to leave the parts including the spot-welded areas of the first resin frame 41 and the second resin frame 5. Therefore, by performing spot welding of the first resin frame 41 and the second resin frame 5 via the sheet member 9 at least on the reference side 42e, and suppressing the generation of burrs at the welding point HP, the adhesion between the first resin frame 41 and the second resin frame 5 between adjacent laminated units 3 can be suitably ensured.

[0059] In the placement step ST1, before placing the second resin frame 5, the separator 6 is placed on top of the electrode 4 with the resin frame, and then the outer edge 6a of the separator 6 is fixed to the first resin frame 41. In the temporary fixing step ST2, when viewed from the lamination direction D1, spot welding of the first resin frame 41 and the second resin frame 5 is performed 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. With this configuration, the positional relationship of the separator 6 with respect to the electrode 4 with the resin frame can be taken into consideration, and the generation of burrs at the welding point HP between the first resin frame 41 and the second resin frame 5 can be suppressed.

[0060] A welding apparatus according to one aspect of this disclosure includes a hot iron 8 for spot welding resin members (a first resin frame 41 and a second resin frame 5), and a sheet member 9 is provided at the tip 8a of the hot iron 8. Let's consider a case where, for example, two resin members (a first resin frame 41 and a second resin frame 5) are stacked on top of each other, and the two resin members are spot-welded from the side of the upper resin member (the second resin frame 5). In this case, the sheet member 9 is provided at the tip 8a of the hot iron 8, with a wider area than the tip 8a. As a result, when the resin constituting the upper resin member (the second resin frame 5) melts due to the heat from the hot iron 8, the molten resin flows along the surface 9a of the sheet member 9, suppressing the bulging of the resin member caused by the pressure of the hot iron 8. As a result, the resin member cools and hardens in a flattened state, and the generation of burrs at the welding point HP is suppressed.

[0061] While embodiments of this disclosure have been described above, this disclosure is not necessarily limited to the embodiments described above, and various modifications are possible without departing from its essence.

[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 on at least one of the three sides other than the reference side 42e, similar to the reference side 42e. Alternatively, spot welding may be performed via the sheet member 9 on all three sides other than the reference side 42e. Alternatively, one of the three sides other than the reference side 42e may be spot-welded via the sheet member 9, and the remaining two sides may be spot-welded by directly applying the tip portion 8a to the second resin frame 5 without using the sheet member 9.

[0063] In the temporary fixing step ST2, tension is not necessarily applied to the sheet member 9. For example, the sheet-shaped 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 lamination step ST3, the electrode laminate 2 may be formed by laminating multiple laminate units 3 as a single unit, one unit at a time. For example, after the temporary fixing step ST2, three layers of laminate units 3 may be temporarily fixed to each other along the lamination direction D1, and in the lamination step ST3, the three layers of laminate units 3 may be laminated as a single unit.

[0064] In the placement step ST1, the second resin frame 5 may be adsorbed by an adsorption plate. Figure 12 shows an example of spot welding using an adsorption plate 60. In the example in Figure 12, in the placement step ST1, the second resin frame 5 is adsorbed by the adsorption plate 60 and placed on the first resin frame 41. Then, in the temporary fixing step ST2, with the second resin frame 5 adsorbed by the adsorption plate 60, the first resin frame 41 and the second resin frame 5 are temporarily fixed together by spot welding via the adsorption 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 metal, for example. 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 the suction pad, causing the second resin frame 5, which is positioned opposite the suction pad, to be attached to and released from the suction plate 60. In the example of Figure 12, the outer edge of the suction plate 60 is located outside the outer edge 41a of the first resin frame 41 and the outer edge 5a of the second resin frame 5, but it may coincide with the outer edge 41a of the first resin frame 41 and the outer edge 5a of the second resin frame 5.

[0066] The suction plate 60 includes a plurality of notches 60a on the side corresponding to the reference side 42e (see Figure 2(b)). The second resin frame 5 is exposed in a plan view through the plurality of notches 60a. The plurality of notches 60a extend horizontally in the direction D3 from the side corresponding to the reference side 42e. The tips of the plurality of notches 60a may be located on the inner edge 5b side of the second resin frame 5 rather than the outer edge 6b of the separator 6 (see Figure 2(b)). In the temporary fixing step ST3, the suction plate 60 adsorbs the second resin frame 5 such that the position of point welding through the plurality of notches 60a is in the region R (see Figure 6) between the outer edge 42d of the electrode foil 42 (see Figure 2(b)) and the outer edge 6b of the separator 6. The plurality of notches 60a may be evenly distributed or unevenly distributed in the vertical direction D2. In either case, the adsorption plate 60 adsorbs the second resin frame 5 such that multiple notches 60a are located on both sides of the liquid injection port 5c. In the example shown in Figure 12, two notches 60a are positioned to sandwich the liquid injection port 5c.

[0067] The suction plate 60 includes a plurality of notches 60b along the sides corresponding to the three sides excluding the reference side 42e. In a plan view, the second resin frame 5 is exposed at the plurality of notches 60b. The plurality of notches 60b extend horizontally D3 or vertically D2 from the sides corresponding to the three sides excluding the reference side 42e. In the example of Figure 12, the tips of the plurality of notches 60b are located on the outer edge 41a side of the first resin frame 41 rather 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 performing the sealing process. Therefore, in the temporary fixing process ST3, the suction plate 60 does not necessarily need to adsorb the second resin frame 5 so that the position of point welding via the plurality of notches 60b is region R.

[0068] In the temporary fixing process ST2, a tension-applying mechanism may be used to apply tension to the sheet member 9. Figure 13(a) shows an example before the hot iron 8 is pressed against the sheet member 9 when the tension-applying mechanism 90 is used. The tension-applying mechanism 90 includes a pair of first support rollers 91, 92, a second support roller 93, a third support roller 94, a sheet feed roller 95, and a sheet winding roller 96. In the tension-applying mechanism 90, the sheet member 9 fed from the sheet feed roller 95 is conveyed in the conveying direction A1 and is wound onto the sheet winding roller 96 via the pair of first support rollers 91, 92, the second support roller 93, and the third support roller 94. The sheet member 9 is in contact with the outer circumference of each of the pair of first support rollers 91, 92, the second support roller 93, and the third support roller 94, thereby conveying the sheet member 9 under constant tension. Between a pair of first support rollers 91 and 92, the sheet member 9 is stretched across the hot iron 8. The sheet member 9 is stretched such that there is 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 and 92 in the in-plane direction (in the in-plane direction of the surface of the second resin frame 5).

[0069] Figure 13(b) shows an example of the process after pressing the hot iron 8 against the sheet member 9 when using the tension-applying mechanism 90. In the temporary fixing process ST2, with tension applied to the sheet member 9 between the pair of first support rollers 91 and 92, the hot iron 8 is pressed against the second resin frame 5 via the sheet member 9. At this time, as shown in Figure 13(b), tension is applied to the sheet member 9 not only in the in-plane direction but also in the direction against which the hot iron 8 is pressed. This makes it easier to further suppress the deflection of the sheet member 9 during temporary fixing.

[0070] In the temporary fixing step ST2, the sheet member 9 does not have to be used. In the temporary fixing step ST2, the tip of the soldering 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, instead of the soldering iron 8, a modified soldering iron 8A as shown in Figure 14 may be used. The soldering iron 8A has a heating element 81 that generates heat and a protective element 82 that covers the heating element. The heating element 81 has, for example, a cylindrical body 81c and a tip 81a that tapers from the body 81c toward the tip surface 81b. The protective element 82 has, for example, a cylindrical body 82c and a tip 82a that tapers from the body 82c toward the tip surface 82b. The main body portion 81c of the heating element 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 heating element 81 such that the tip surface 81b of the heating element 81 protrudes from the tip surface 82b of the protective portion 82, or it may be configured so that the tip surface 82b of the protective portion 82 and the tip surface 81b of the heating element 81 are flush. 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 a lower thermal conductivity than metals such as aluminum or copper. The protective portion 82 may, for example, be made of a ceramic material with low thermal conductivity. This makes it difficult for heat from the heating element 81 to be absorbed by the protective portion 82, and allows sufficient heat to be transferred to the second resin frame 5.

[0071] In the temporary fixing step ST2 when using the hot soldering iron 8A, for example, as shown in Figure 14, the tip 81a of the heating element 81 and the tip 82a of the protective element 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 element 82, the molten resin flows along the surface of the protective element 82, suppressing the bulging of the resin caused by the pressure of the heating element 81. This maintains the flatness of the resin and suppresses the generation of burrs at the welding point HP.

[0072] The heating 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 tip surface 81b of the heating element 81 and the tip surface 82b of the protective element 82 may be pressed against the sheet member 9. Alternatively, the sheet member 9 may be brought into contact with the tip surfaces 81b and 82b in advance, and the tip surfaces 81b and 82b of the sheet member 9 in contact with the second resin frame 5 may be pressed against it. In either embodiment, when the tip surfaces 81b and 82b are pressed against 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 soldering iron 8A, a soldering iron 8B may be used, as shown in Figure 15, in which an annular cap member 83 is fixed around the tip portion 8a of the soldering iron 8. As shown in Figure 15, the soldering iron 8B may be used together with the 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 that has high heat resistance and low thermal conductivity. The cap member 83 may be made of, for example, Teflon® resin. In the temporary fixing step ST2, temporary fixing is performed using the soldering iron 8B, on which the cap member 83 is attached so that the tip surface 8b is exposed from the through hole 83a. In the temporary fixing step ST2, the sheet member 9 may be placed on the second resin frame 5, and the tip portion 8a may be pressed against the sheet member 9 while the cap member 83 is brought into contact with the sheet member 9 around the tip portion 8a. Alternatively, the sheet member 9 may be brought into contact with the tip surface 8b of the soldering iron 8 beforehand, and the tip surface 8b with the sheet member 9 in contact may be pressed against the second resin frame 5. In either embodiment, when the tip surface 8b of the soldering iron 8B is pressed against the second resin frame 5, the sheet member 9 may be made to adhere closely to the surface of the second resin frame 5. This maintains the flatness of the resin and suppresses the generation of burrs at the welding point HP.

[0074] The hot iron 8B does not necessarily 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 of the cap member 83 may be pressed against the second resin frame 5 while the cap member 83 is in contact with the resin member surrounding the tip 8a. In this case, the molten resin flows along the surface of the cap member 83, suppressing the bulging of the resin caused by pressing the hot iron 8.

[0075] The gist of this disclosure is as follows: [1] to [6]. [1] A method for manufacturing an energy storage module, comprising: a preparation step of preparing an electrode with a resin frame by welding a first resin frame made of resin to the outer edge of an electrode foil having an active material layer; a placement step of placing a second resin frame made of resin on top of the first resin frame of the electrode with a resin frame; a temporary fixing step of temporarily fixing the first resin frame and the second resin frame that were placed on top of each other in the placement step by spot welding using a hot iron; and a lamination step of stacking a plurality of the electrodes with resin frames, each with the second resin frame temporarily fixed, as a single laminated 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 according to [1], further comprising: a restraining step of restraining the laminate in the stacking direction of the laminated unit and applying a restraining load to the first resin frame and the second resin frame which are 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 which are adjacent to each other in the stacking direction while the restraining load is applied. [3] The method for manufacturing an energy storage module according to [1] or [2], wherein in the temporary fixing step, tension is applied to the sheet member and the tip of the hot iron is pressed toward the first resin frame or the second resin frame. [4] The method for manufacturing an energy storage module according to any one of [1] to [3], wherein the electrode with a resin frame has a rectangular shape with four sides in a plan view, and one of the four sides is set as a reference side, and in the arrangement step, the side on which the liquid injection port of the second resin frame is formed is arranged to overlap the reference side, in the temporary fixing step, the first resin frame and the second resin frame are spot-welded via the sheet member at least on the reference side, and in the lamination step, the lamination units are stacked while aligning the reference side as the lamination reference. [5] A method for manufacturing an energy storage module according to any one of [1] to [4], wherein in the arrangement step, before arranging the second resin frame, a separator is placed on top of the electrode with the resin frame, and the 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 via the sheet member is performed in the region between the outer edge of the electrode foil and the outer edge of the separator, as viewed from the lamination direction of the laminated unit. [6] A welding device comprising a hot iron for spot welding resin members together, wherein a sheet member covering a wider area than the tip of the hot iron is provided at the tip of the hot iron. [Explanation of Symbols]

[0076] 1...Energy storage module, 2...Electrode laminate, 3...Laminate unit, 4...Electrode with resin frame, 5...Second resin frame, 5a...Outer edge of the second resin frame, 6...Separator, 6a...Outer edge of the separator, 6b...Outer edge of the separator, 8...Hot soldering iron, 8a...Tip, 9...Sheet member, 10...Welding device, 30...Laminate, 41...First resin frame, 41a...Outer edge of the first resin frame, 42...Electrode foil, 42c...Outer edge of the electrode foil, 42d...Outer edge of the electrode foil, 42e...Reference side, D1...Lamination direction, ST1...Placement process, ST2...Temporary fixing process, ST3...Lamination process, ST4...Restraint process, ST5...End face welding process.

Claims

1. A preparation step to prepare an electrode with a resin frame by welding a first resin frame made of resin to the outer edge of an electrode foil on which an active material layer is provided, The arrangement step involves placing a second resin frame made of resin on top of the first resin frame of the electrode with a resin frame, A temporary fixing step is performed in which the first resin frame and the second resin frame, which were stacked in the aforementioned arrangement step, are temporarily fixed by spot welding using a hot iron. The process includes a lamination step of stacking multiple electrodes with resin frames, each temporarily fixed to a second resin frame, as a single lamination unit to form a laminate, A method for manufacturing an energy storage module, 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 together via the sheet member.

2. A restraining step of restraining the laminate in the stacking direction of the stacking unit and applying a restraining load to the first resin frame and the second resin frame which are aligned in the stacking direction, A method for manufacturing an energy storage module according to claim 1, further comprising: an end-face welding step of welding the outer edges of the first resin frame and the second resin frame adjacent to each other in the stacking direction while the aforementioned restraining load is applied.

3. The method for manufacturing an energy storage module according to claim 1 or 2, wherein in the temporary fixing step, tension is applied to the sheet member and the tip of the hot iron is pressed toward the first resin frame or the second resin frame.

4. The aforementioned electrode with a resin frame has a rectangular shape with four sides in a plan view, and one of these four sides is set as the reference side. In the arrangement step, the side of the second resin frame on which the liquid injection port is formed is positioned so as to overlap with the reference side. In the temporary fixing step, spot welding is performed on the first resin frame and the second resin frame via the sheet member at least on the reference edge. The method for manufacturing an energy storage module according to claim 1 or 2, wherein in the lamination step, the lamination units are stacked while aligning the reference edge with the lamination reference.

5. In the aforementioned arrangement step, before arranging the second resin frame, the separator is placed on top of the electrode with the resin frame, and then the outer edge of the separator is fixed to the first resin frame. The method for manufacturing an energy storage module according to claim 1 or 2, wherein in the temporary fixing step, spot welding of the first resin frame and the second resin frame via the sheet member is performed in the region 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. Equipped with a hot iron for spot welding resin components together, A welding device wherein a sheet member covering a wider area than the tip of the aforementioned hot iron is provided at the tip of the hot iron.

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