Method for manufacturing power storage device

Abstract

To provide a method for manufacturing a power storage device which eliminates a thickness step of a spacer, and can prevent airtightness leakage when a power storage device is manufactured by being stacked on an electrode.SOLUTION: A method for manufacturing a power storage device includes a step of forming a lightening part in an overlapping part of a plurality of resin plates or the periphery of the overlapping part when overlapping the resin plates and manufacturing a spacer, and heating and compressing the overlapping part and thereby manufacturing the spacer.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present application relates to a method for manufacturing an electricity storage device. [Background technology]

[0002] A storage module is manufactured by stacking a bipolar electrode having a resin frame (first sealing layer, second sealing layer) and a frame-shaped spacer layer and welding the end faces of the resin frame and the spacer layer (for example, Patent Document 1). Patent Document 2 also describes a manufacturing method for an electricity storage module that uses a resin frame. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-046589 A [Patent Document 2] JP 2019-102127 A Summary of the Invention [Problem to be solved by the invention]

[0004] The spacer (spacer layer) is made by welding multiple resin plates arranged in a frame shape. When the spacer is made, a thickness difference occurs where the resin plates overlap. As a result, a minute gap due to the thickness difference occurs in the laminated portion of the resin frame and the spacer after the spacer is laminated together with the bipolar electrode. If the end faces of the resin frame and the spacer are welded in a state in which such a minute gap occurs, a void due to the gap occurs in the welded portion, which may lead to poor welding of the end faces. Poor welding of the end faces is undesirable as it can cause air leakage in the energy storage device.

[0005] An object of the present application is to provide a method for manufacturing an electricity storage device that can eliminate thickness differences in spacers and prevent air leakage when the spacers are stacked with electrodes to produce an electricity storage device. [Means for solving the problem]

[0006] In order to solve the above problems, the present inventors conducted extensive research and discovered the following. When manufacturing a spacer by welding plastic sheets, creating a hollowed-out section near the overlapping part of the spacer ensures an escape route for the plastic when adjusting the thickness, thereby ensuring uniformity in the thickness of the spacer.

[0007] Based on the above, the present inventors have completed the following invention. [1] A method for manufacturing an energy storage device, comprising the steps of: when stacking multiple resin plates to produce a spacer, forming a recess in the overlapping portion of the resin plates or around the overlapping portion; and heating and compressing the overlapping portion to produce a spacer.

[0008] [2] The method for manufacturing an energy storage device according to [1], wherein an area of ​​the hollowed-out portion is the same as an area of ​​the overlapping portion of the resin plate. [3] The method for manufacturing an electricity storage device according to [1] or [2], wherein the recess is provided in the overlapping portion of the resin plate.

[0009] [4] The method for manufacturing an electricity storage device according to any one of [1] to [3], wherein the recess is provided around the overlapping portion of the resin plate, at a position within 20 mm from an outer edge of the overlapping portion. [5] The method for producing an electricity storage device according to any one of [1] to [4], wherein the overlapping portions of the resin plates are heated and compressed at 150 to 200° C. and at 5 to 10 N to obtain a spacer. Effect of the Invention

[0010] According to the method for producing an electricity storage device of the present invention, thickness differences in the spacers are eliminated, and air leakage can be prevented when the spacers are laminated with the electrodes to produce an electricity storage device. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a side view that illustrates a schematic diagram of an electricity storage device. [Diagram 2]FIG. 2 is a schematic cross-sectional view showing the layer structure of the electricity storage module 11. As shown in FIG. [Diagram 3] 3(a) is a plan view of the spacer 33 as viewed from the stacking direction in the electricity storage module 11 of FIG. 2, and FIG. 3(b) is an enlarged view of the welded portion W. As shown in FIG. [Figure 4] FIG. 4 is a diagram showing the state of the spacer welding experiment. [Diagram 5] 5(a) to (c) are conceptual diagrams showing embodiments of positions where the lightening holes are formed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a method for manufacturing a storage device according to the present invention will be described with reference to the drawings.

[0013] <Method of manufacturing electricity storage device>

[0014] (Electricity storage device) Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and duplicated descriptions will be omitted. In the description, a Cartesian coordinate system defined by an X-axis, a Y-axis, and a Z-axis may be referred to.

[0015] 1 is a side view showing a schematic diagram of an example of an energy storage device. The energy storage device 1 can be used as a battery for various vehicles, such as a forklift, a hybrid vehicle, an electric vehicle, etc. The energy storage device 1 includes a module stack 2 including an energy storage module 11, connection members 3 and 4 electrically connected to the module stack 2, a pair of end plates 5 and 5 for restraining the module stack (stack) 2, and a fastening member 6 for fastening the end plates 5 and 5 together.

[0016] The module stack 2 is configured by stacking a plurality of power storage modules 11 and a plurality of conductive plates P in the Z-axis direction. In the example of FIG. 1, the module stack 2 includes two power storage modules 11 and three conductive plates P. The three conductive plates P are disposed between the power storage modules 11, 11 and at both ends of the module stack 2 in the stacking direction. These conductive plates P are electrically connected to electrodes that constitute the power storage module 11. Here, the two power storage modules 11 are connected in series by the conductive plates P.

[0017] (Energy storage module) 2 is a schematic cross-sectional view showing a layer structure of the electricity storage module 11. The electricity storage module 11 is a single cell having a rectangular parallelepiped shape that is flattened in the Z-axis direction. In this embodiment, a bipolar type lithium ion secondary battery is exemplified as the electricity storage module 11. The electricity storage module 11 is configured to include an electrode stack (stack) 12 including a plurality of bipolar electrodes 14, and a sealing portion 30. The bipolar electrodes 14 in the electrode stack 12 are stacked along the Z-axis direction. The stacking direction of the bipolar electrodes 14 is along the Z-axis direction and coincides with the stacking direction of the electricity storage modules 11 in the module stack 2.

[0018] The bipolar electrode 14 includes a current collector 21, a positive electrode active material layer (first active material layer) 22 provided on a first surface 21a of the current collector 21, and a negative electrode active material layer (second active material layer) 23 provided on a second surface 21b of the current collector 21. The current collector 21 and the positive electrode active material layer 22 provided on the first surface 21a of the current collector 21 constitute a positive electrode of the bipolar electrode 14, and the current collector 21 and the negative electrode active material layer 23 provided on the second surface 21b of the current collector 21 constitute a negative electrode of the bipolar electrode 14. The positive electrode active material layer 22 is formed in a rectangular shape at the center of the first surface 21a so that the periphery 21c of the current collector 21 is exposed. The negative electrode active material layer 23 is formed in a rectangular shape at the center of the second surface 21b so that the periphery 21c of the current collector 21 is exposed. In one example, when viewed from the stacking direction, the positive electrode active material layer 22 is contained within the region of the negative electrode active material layer 23. In other words, the outer edge of the positive electrode active material layer 22 is slightly smaller than the outer edge of the negative electrode active material layer 23.

[0019] The current collector 21 is a sheet-like conductive member having a rectangular shape in a plan view, and has a first surface 21a and a second surface 21b located on the opposite side of the first surface 21a. The current collector 21 is made of, for example, a metal foil or an alloy foil. Examples of the metal foil include copper foil, aluminum foil, titanium foil, and nickel foil. Examples of the alloy foil include stainless steel foil (e.g., SUS304, SUS316, SUS301, etc., as specified in JIS G 4305:2015), plated steel plate (e.g., cold-rolled steel plate (SPCC, etc.) as specified in JIS G 3141:2005), and plated stainless steel plate. The alloy foil may be an alloy foil of the metal exemplified as the material of the metal foil. The current collector 21 may be formed by integrating or laminating a plurality of metal foils, or may be formed by plating another metal on the surface of a metal foil.

[0020] The current collector 21 in the illustrated example may be, for example, a clad foil in which an aluminum foil and a copper foil are bonded together such that the first surface 21a is an aluminum layer and the second surface 21b is a copper layer. The aluminum layer on the first surface 21a of the current collector 21 may be chromated. The copper layer on the second surface 21b of the current collector 21 may be nickel-plated. In this case, the nickel-plated layer may be a roughened surface that is a protruding plated surface having fine protrusions on its surface.

[0021] The positive electrode active material layer 22 is a layered member including a positive electrode active material, a conductive assistant, and a binder. Examples of the positive electrode active material include a composite oxide, metallic lithium, and sulfur. The composition of the composite oxide includes at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. Examples of the composite oxide include olivine-type lithium iron phosphate (LiFePO4), LiCoO2, and LiNiMnCoO2.

[0022] The binder serves to bind the active material or the conductive assistant to the surface of the current collector 21 and maintain the conductive network in the electrode. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluorine rubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, acrylic resins containing monomer units such as acrylic acid and methacrylic acid, styrene-butadiene rubber (SBR), carboxymethyl cellulose, alginates such as sodium alginate and ammonium alginate, water-soluble cellulose ester crosslinked bodies, and starch-acrylic acid graft polymers. These binders can be used alone or in combination. Examples of the conductive assistant include acetylene black, carbon black, and graphite. The positive electrode active material layer 22 may contain a viscosity adjusting solvent such as N-methyl-2-pyrrolidone (NMP).

[0023] The negative electrode active material layer 23 is a layered member containing a negative electrode active material, a conductive assistant, and a binder. Examples of the negative electrode active material include graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, soft carbon, and other carbon, metal compounds, elements that can be alloyed with lithium or compounds of such elements, and boron-added carbon. Examples of elements that can be alloyed with lithium include silicon and tin. The conductive assistant and binder may be the same as those used in the positive electrode active material layer 22.

[0024] To form the positive electrode active material layer 22 and the negative electrode active material layer 23 on the current collector 21, a conventionally known method such as roll coating, die coating, dip coating, doctor blade, spray coating, curtain coating, etc. is used. Specifically, an active material, a solvent, and, if necessary, a binder and a conductive assistant are mixed to produce a slurry-like active material layer forming composition, which is then applied to the first surface 21a and the second surface 21b and then dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. The dried product may be compressed to increase the electrode density.

[0025] In the electrode laminate 12, the bipolar electrodes 14, 14 adjacent to each other in the stacking direction are arranged such that the positive electrode active material layer 22 and the negative electrode active material layer 23 face each other. A separator 15 is arranged between the bipolar electrodes 14, 14. In this embodiment, the separator 15 is a sheet-like member having a rectangular shape in a plan view, and prevents a short circuit between the bipolar electrodes 14, 14 adjacent to each other in the stacking direction.

[0026] The separator 15 has a rectangular shape that is slightly larger than the positive electrode active material layer 22 and the negative electrode active material layer 23 and slightly smaller than the current collector 21 when viewed from the stacking direction. An end portion 15a of the separator 15 is located outside the positive electrode active material layer 22 and the negative electrode active material layer 23 when viewed from the stacking direction. The end portion 15a of the separator 15 does not overlap either the positive electrode active material layer 22 or the negative electrode active material layer 23 when viewed from the stacking direction.

[0027] The separator 15 is formed, for example, in a sheet shape. The separator 15 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains an electrolyte. Examples of materials constituting the separator 15 include polypropylene, polyethylene, polyolefin, and polyester. The separator 15 may have a single-layer structure or a multilayer structure. In the case of a multilayer structure, the separator 15 may include, for example, a base material layer and a pair of adhesive layers, and may be bonded and fixed to the positive electrode active material layer 22 and the negative electrode active material layer 23 by the pair of adhesive layers. The separator 15 may include a ceramic layer that serves as a heat-resistant layer. The separator 15 may be reinforced with a vinylidene fluoride resin compound.

[0028] Examples of the electrolyte impregnated in the separator 15 include a liquid electrolyte (electrolytic solution) containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent, and a polymer gel electrolyte containing an electrolyte held in a polymer matrix. When the separator 15 is impregnated with an electrolyte, known lithium salts such as LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, and LiN(CF3SO2)2 can be used as the electrolyte salt. In addition, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers can be used as the non-aqueous solvent. Two or more of these known solvent materials may be used in combination.

[0029] The electrode laminate 12 has a positive terminal electrode 16 and a negative terminal electrode 17 in addition to the bipolar electrode 14. The positive terminal electrode 16 is composed of a current collector 21 and a positive electrode active material layer 22 provided on a first surface 21a of the current collector 21. The positive terminal electrode 16 is disposed on one end side in the lamination direction of the electrode laminate 12 so that the positive electrode active material layer 22 on the first surface 21a faces the negative electrode active material layer 23 of the terminal bipolar electrode 14. In the positive terminal electrode 16, the negative electrode active material layer 23 is not provided on the second surface 21b of the current collector 21, and the second surface 21b is electrically connected to the adjacent conductive plate P.

[0030] The negative terminal electrode 17 is composed of a current collector 21 and a negative electrode active material layer 23 provided on a second surface 21b of the current collector 21. The negative terminal electrode 17 is disposed on the other end side in the stacking direction of the electrode laminate 12 so that the negative electrode active material layer 23 on the second surface 21b faces the positive electrode active material layer 22 of the terminal bipolar electrode 14. In the negative terminal electrode 17, the positive electrode active material layer 22 is not provided on the first surface 21a of the current collector 21, and the first surface 21a is electrically connected to the adjacent conductive plate P.

[0031] The separator 15 is disposed between the bipolar electrodes 14, 14 adjacent to each other in the stacking direction, as well as between the bipolar electrode 14 and the positive terminal electrode 16, and between the bipolar electrode 14 and the negative terminal electrode 17. The separator 15 prevents short circuits between the bipolar electrode 14 and the positive terminal electrode 16, and between the bipolar electrode 14 and the negative terminal electrode 17.

[0032] The sealing portion 30 is a member that seals the space S between the current collectors 21 adjacent to each other in the stacking direction. The sealing portion 30 has electrical insulation properties. The sealing portion 30 is bonded (joined) to the edge of the current collector 21. The sealing portion 30 is spaced apart from the positive electrode active material layer 22 and the negative electrode active material layer 23 when viewed from the stacking direction. The sealing portion 30 is frame-shaped when viewed from the stacking direction, and is disposed between the current collectors 21 adjacent to each other in the stacking direction so as to surround the periphery of the positive electrode active material layer 22 and the negative electrode active material layer 23. In the electricity storage module 11, a space S is defined by the current collectors 21 adjacent to each other in the stacking direction and the sealing portion 30. An electrolyte (not shown) is accommodated in the space S. The sealing portion 30 is disposed between the current collectors adjacent to each other in the stacking direction, and thus also functions as a spacer that maintains a distance between the adjacent current collectors.

[0033] The sealing portion 30 in one example has a first seal layer 31, a second seal layer 32, and a spacer layer 33. The first seal layer 31, the second seal layer 32, and the spacer layer 33 each have a rectangular frame shape when viewed from the stacking direction. The first seal layer 31 is bonded to the first surface 21a along the periphery 21c of the current collector 21. In one example, when viewed from the stacking direction, the outer edge 31b of the first seal layer 31 is larger than the edge 21d of the current collector 21 and surrounds the current collector 21. Also, when viewed from the stacking direction, the edge 21d of the current collector 21 is larger than the inner edge 31a of the first seal layer 31 and surrounds the inner edge 31a of the first seal layer 31. The first seal layer 31 and the current collector 21 are bonded to each other in a region where they overlap each other when viewed from the stacking direction. That is, the first seal layer 31 and the current collector 21 are joined to each other in a region from the inner edge 31a of the first seal layer 31 to the edge 21d of the current collector 21. When viewed from the stacking direction, the inner edge 31a of the first seal layer 31 is separated from the positive electrode active material layer 22.

[0034] The second seal layer 32 is bonded to the second surface 21b along the periphery 21c of the current collector 21. In one example, the outer edge 32b of the second seal layer 32 is larger than the edge 21d of the current collector 21 and surrounds the current collector 21 when viewed from the stacking direction. For example, the second seal layer 32 and the current collector 21 are bonded to each other in an overlapping region. That is, the second seal layer 32 and the current collector 21 are bonded to each other in a region from the inner edge 32a of the second seal layer 32 to the edge 21d of the current collector 21. When viewed from the stacking direction, the inner edge 32a of the second seal layer 32 is spaced from the negative electrode active material layer 23.

[0035] In the positive terminal electrode 16, the first seal layer 31 is joined to the first surface 21a of the current collector 21, and the second seal layer 32 is not joined to the second surface 21b. In the negative terminal electrode 17, the second seal layer 32 is joined to the second surface 21b of the current collector 21, and the first seal layer 31 is not joined to the first surface 21a.

[0036] The spacer layer 33 is provided between the first seal layer 31 and the second seal layer 32, and is welded to the first seal layer 31 and the second seal layer 32. When viewed from the stacking direction, the inner edge 31a of the first seal layer 31 and the inner edge 32a of the second seal layer 32 are located inside the inner edge 33a of the spacer layer 33, respectively. The inner edges 31a, 32a are located, for example, 1 mm or more inside the inner edge 33a. That is, the inner edge 31a of the first seal layer 31 is exposed from the spacer layer 33 so as to face the space S. Also, the inner edge 32a of the second seal layer 32 is exposed from the spacer layer 33 so as to face the space S.

[0037] The spacer layer 33 is welded to the first seal layer 31 outside the inner edge 31a of the first seal layer 31 when viewed from the stacking direction. The spacer layer 33 is welded to the second seal layer 32 outside the inner edge 32a of the second seal layer 32 when viewed from the stacking direction. That is, a joining region R1 where the first seal layer 31, the second seal layer 32, and the spacer layer 33 are welded to each other is outside the inner edge 31a of the first seal layer 31 and the inner edge 32a of the second seal layer 32. In one example, the joining region R1 is outside the inner edge 33a of the spacer layer 33. In the illustrated example, the region outside the edge 21d of the current collector 21 is the joining region R1. That is, when viewed from the stacking direction, the first seal layer 31, the second seal layer 32, and the spacer layer 33 are welded to one another in a region from the edge 21d of the current collector 21 to the outer edges of the first seal layer 31, the second seal layer 32, and the spacer layer 33. Therefore, when viewed from the stacking direction, a portion of the spacer layer 33 located inside the joining region R1 is not welded (bonded) to the first seal layer 31 and the second seal layer 32.

[0038] An end portion 15a of the separator 15 is fixed to the second seal layer 32 on the inside of an inner edge 33a of the spacer layer 33. The end portion 15a is partially adhered (welded) to the second seal layer 32 by, for example, spot welding.

[0039] When viewed from the stacking direction, the first sealing layer 31 is spaced apart from the positive electrode active material layer 22, and the inner edge 31a is located outside the positive electrode active material layer 22. When viewed from the stacking direction, the second sealing layer 32 is spaced apart from the negative electrode active material layer 23, and the inner edge 32a is located outside the negative electrode active material layer 23. In this embodiment, when viewed from the stacking direction, the first sealing layer 31 is also spaced apart from the negative electrode active material layer 23, but the first sealing layer 31 may overlap the negative electrode active material layer 23 as long as it is spaced apart from the positive electrode active material layer 22.

[0040] In the stacking direction, the thickness of the first seal layer 31 and the thickness of the second seal layer 32 are, for example, thinner than the thickness of the spacer layer 33. The thickness of the first seal layer 31 is the thickness of a portion of the first seal layer 31 sandwiched between the current collector 21 and the spacer layer 33. The thickness of the second seal layer 32 is the thickness of a portion of the second seal layer 32 sandwiched between the current collector 21 and the spacer layer 33. The thickness of the spacer layer 33 is the thickness of a portion of the spacer layer 33 sandwiched between the first seal layer 31 and the second seal layer 32. The thickness of the first seal layer 31 and the second seal layer 32 may be, for example, 1 / 10 or more and 1 / 2 or less of the thickness of the spacer layer 33. The thicknesses of the first seal layer 31 and the second seal layer 32 may be equal to or greater than the thickness of the spacer layer 33, or may be different from each other. The thicknesses of the first seal layer 31 and the second seal layer 32 may be thicker than the spacer layer 33.

[0041] The first seal layer 31, the second seal layer 32, and the spacer layer 33 are made of a resin material having electrolyte resistance, such as acid-modified polyethylene (acid-modified PE), acid-modified polypropylene (acid-modified PP), polyethylene, or polypropylene. The resin materials constituting the first seal layer 31, the second seal layer 32, and the spacer layer 33 may be the same as or different from each other. In this embodiment, the first seal layer 31 and the second seal layer 32 are made of acid-modified polyethylene or acid-modified polypropylene. The spacer layer 33 is made of polyethylene or polypropylene.

[0042] (Spacer manufacturing method) Fig. 3 shows an example of a method for manufacturing the spacer 33. Fig. 3(a) is a plan view of the spacer 33 as viewed from the stacking direction in the electricity storage module 11 of Fig. 2. The spacer 33 is made using five resin plates 33A, 33B, 33C, 33D, and 33E, and the spacer is formed by overlapping parts of each resin plate and arranging them in a frame shape as shown in Fig. 3, and welding the overlapping parts of the resin plates using a hot iron or the like. However, as shown in an enlarged view of a portion W including the welded portion AD in Fig. 3(b), there is a problem in that the resin of the welded portion AD escapes to the outside as indicated by the arrow in the figure, increasing the thickness around the welded portion AD.

[0043] Figure 4 shows the spacer welding experiment conducted by the inventors. Two resin plates (S1, S2) with a thickness of 0.39 mm were used, and as shown in Figure 4, the two resin plates were placed one on top of the other so that an overlapping portion (welded portion AD) was generated, and a welding experiment was conducted using a hot iron. The welding conditions were as follows: welding temperature: 170°C, welding time: 20 seconds, welding load: 7.5 N. The only area that was pressed was the welded portion AD. The size of the welded portion AD was 20 mm in X and 46 mm in Y. After welding, the thickness of the welded portion AD and the thickness of the periphery of the welded portion, which is the resin plate S1 side of the welded portion AD, were measured. The thickness of the welded portion AD was measured at seven points indicated by dots in Fig. 4, and the thickness of the periphery of the welded portion was measured at two points (D1, D2) also indicated by dots in Fig. 4.

[0044] The plate thickness measurement results showed that the plate thickness at seven points in the welded portion AD was all within the standard value of 0.343 mm or more and 0.437 mm or less. However, at two points around the welded portion AD, D1 was 0.513 mm and D2 was 0.504 mm, which was outside the standard value. In addition, an experiment was conducted on welding the spacer created above to the resin frame surrounding the adjacent electrodes. As a result, gaps occurred due to the difference in thickness of the spacer during welding, resulting in poor welding (voids). Therefore, it was found that the use of such a spacer would result in poor airtightness.

[0045] In order to solve the above problems, the inventors discovered that when welding resin plates to produce a spacer, by providing a cutout at the overlapping portion between the resin plates (welded portion AD) or near the overlapping portion (welded portion AD) and heating and compressing the overlapping portion between the resin plates, it is possible to ensure an escape route for the resin when adjusting the thickness of the overlapping portion, thereby ensuring the uniformity of the thickness of the resulting spacer.

[0046] (Cutout formation) 5(a) to 5(c) show embodiments of the lightening hole H formed in the overlapping portion of the resin plate. As shown in Fig. 5(a), the lightening hole H may be formed around the overlapping portion (welded portion AD) of the resin plate, or as shown in Fig. 5(b), the lightening hole H may be formed in the overlapping portion (welded portion AD) of the resin plate. 5, as an example, holes having a circular cross section are formed, but the cross-sectional shape is not limited to a circle and may be holes having a rectangular cross section. Also, the holes may be through holes or blind holes, but it is preferable that the holes are through holes because this makes the spacer have a more uniform thickness after welding.

[0047] In addition, it is preferable that the area of ​​the cutout H such as a through hole is the same as the area of ​​the overlapping portion of the resin plate. Here, the area of ​​the cutout H is the total area of ​​the cutout portion when the cutout H is viewed in plan in the plan view shown in Fig. 5, and is the total cross-sectional area of ​​the through holes in Fig. 5. The periphery of the overlapping portion (welded portion AD) of the resin plates means preferably within 20 mm, more preferably within 15 mm, and further preferably within 10 mm from the outer edge of the welded portion AD.

[0048] 5(c), the area to the right of L1 is a cut area that is cut in a post-process after welding. From the viewpoint of further improving the thickness uniformity of the spacer to be formed, it is preferable to form a hollow H in the cut area. The cut region refers to the left and right ends of the frame-shaped spacer in Figure 3(a), and preferably 20 mm or less, more preferably 15 mm or less, and even more preferably 10 mm or less from the left and right outer edges of the spacer are removed as the cut region by cutting.

[0049] In Figure 5 above, the welded points AD between resin plates 33C and 33E in Figure 3 are shown as an example, but the same applies to the formation forms of the cutouts H in the welded points between resin plates 33A and 33C, the welded points between resin plates 33A and 33B, and the welded points between resin plates 33B and 33D.

[0050] (heat compression) The resin plates are placed with overlapping portions (welding points AD), and the overlapping portions are heated and compressed to weld the overlapping portions to form a frame-shaped spacer. The conditions for the heat compression are not particularly limited as long as the resin plates can be welded together, but the welding temperature is preferably 150°C to 200°C, and more preferably 160°C to 180°C. The welding load is preferably 5N to 10N, and more preferably 6N to 8N. The welding time is preferably 1 second to 5 minutes, and more preferably 5 seconds to 1 minute.

[0051] (Type of storage device) The method for producing an electric storage device of the present invention is applicable to various electric storage devices, but is particularly suitable for bipolar batteries having bipolar electrodes in which a positive electrode is formed on one side of a current collector and a negative electrode is formed on the other side of the current collector, and is more suitable for large electric storage devices having a large area in the direction perpendicular to the stacking direction of the electrodes. Here, a large-scale electricity storage device is one whose area in a direction perpendicular to the electrode lamination direction is preferably 500 cm 2 More than 10,000cm 2 Less than 700cm, more preferably 2 More than 5,000cm 2 below, More preferably, 800 cm 2 More than 3,000cm 2 This refers to a large-area flat battery having the following dimensions: [Explanation of symbols]

[0052] 1: Energy storage device 11: Energy storage module 33: Spacer 33A, 33B, 33C, 33D, 33E: Resin plate AD: Welded area H:Meatless

Claims

1. A manufacturing method for an energy storage device, comprising the steps of: when stacking multiple resin plates to produce a spacer, forming a hollowed-out area at or around the overlapping area of ​​the resin plates; and heating and compressing the overlapping area to produce a spacer.

2. The method for manufacturing an electricity storage device according to claim 1 , wherein an area of ​​the hollowed-out portion is the same as an area of ​​the overlapping portion of the resin plate.

3. The method for manufacturing an electricity storage device according to claim 1 , wherein the recess is provided at an overlapping portion of the resin plate.

4. The method for manufacturing an electricity storage device according to claim 1 , wherein the recess is provided around the overlapping portion of the resin plate and within 20 mm from an outer edge of the overlapping portion.

5. The method for producing an electricity storage device according to claim 1 or 2, wherein the spacer is obtained by heating and compressing the overlapping portions of the resin plates at 150 to 200° C. and at 5 to 10 N.

Images