Method for manufacturing an electricity storage device

Abstract

To provide a method of manufacturing a power storage device improved in stability of welding of current collector foil and a collector.SOLUTION: A method of manufacturing a power storage device is a method of manufacturing a power storage device that comprises: a positive electrode 40 having a plurality of laminated positive electrode current collector foils 52 and a positive electrode collector 44 connected to the laminated positive electrode current collector foils 52; and a negative electrode 60 having a plurality of laminated negative electrode current collector foils 72 and a negative electrode collector 64 connected to the laminated negative electrode current collector foils 72. The manufacturing method includes: applying a tensile force along a predetermined linear direction to the plurality of laminated current collector foils pressed against the collector, while pressing the plurality of laminated current collector foils against the collector, in at least one of the positive electrode 40 and the negative electrode 60; and applying a laser beam L to a portion positioned on a predetermined linear direction on a surface of the plurality of laminated current collector foils pressed against the collector.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Conventionally, resistance welding or ultrasonic welding has been widely used to join multiple current collecting foils and a current collector of each electrode included in an electrode assembly. Meanwhile, from the viewpoint of cost reduction, technological developments have been made to join multiple current collecting foils and a current collector by laser welding. For example, Patent Documents 1 to 3 disclose welding jigs having through holes through which laser light passes. These welding jigs are configured so that pressure can be applied to multiple stacked current collecting foils in the stacking direction around the through holes. For example, Patent Document 1 discloses that a protrusion is provided on a metal plate (e.g., a current collector) below the portion of the metal foil (e.g., a current collecting foil) where laser welding is to be performed, and by pressing the periphery with a jig, the metal foil and the metal plate can be brought into close contact with each other for laser welding. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-030280 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-136242 [Patent Document 3] Japanese Patent Application Publication No. 2019-067570 Summary of the Invention [Problem to be solved by the invention]

[0004] When laser welding multiple stacked current collecting foils and current collectors, it is desirable that there are no gaps between the current collecting foils and between the current collecting foils and the current collector. If there are gaps, problems such as blowholes, spatter, and breakage of the current collecting foils may occur, reducing welding stability. Because the areas of the current collecting foil where laser welding is to be performed are irradiated with laser light, it is difficult to directly press the areas irradiated with laser light to prevent gaps from occurring.

[0005] The present technology has been made in view of the above circumstances, and its main purpose is to provide a method for manufacturing an electricity storage device with improved welding stability between the current collecting foil and the current collector. [Means for solving the problem]

[0006] The disclosed method for manufacturing an electricity storage device includes a positive electrode including a plurality of stacked positive electrode current collector foils and a positive electrode current collector connected to the stacked positive electrode current collector foils, and a negative electrode including a plurality of stacked negative electrode current collector foils and a negative electrode current collector connected to the stacked negative electrode current collector foils. The disclosed method includes applying tension to the pressed stacked current collector foils along a predetermined linear direction while pressing the pressed stacked current collector foils against the current collector, for at least one of the positive electrode and the negative electrode, and irradiating a portion of the surface of the pressed stacked current collector foils against the current collector with laser light that is located in the predetermined linear direction. According to this manufacturing method, by applying tension in a predetermined linear direction to the multiple stacked current collecting foils, wrinkles in the current collecting foils can be more uniformly smoothed out. This reduces wrinkles in the current collecting foils pressed against the current collector, thereby reducing gaps between the current collecting foils. As a result, welding stability can be improved when laser welding the current collector to the multiple stacked current collecting foils pressed against the current collector. [Brief explanation of the drawings]

[0007] [Figure 1]1 is a schematic cross-sectional view showing an outline of the configuration of a nonaqueous electrolyte secondary battery according to one embodiment. [Figure 2] FIG. 1 is an exploded view schematically illustrating the configuration of an electrode assembly of a nonaqueous electrolyte secondary battery according to one embodiment. [Figure 3] 1 is a schematic diagram roughly illustrating a laser welding method according to a first embodiment. [Figure 4] 5 is a schematic diagram roughly illustrating a laser welding method according to a second embodiment. FIG. [Figure 5] 10A and 10B are schematic diagrams showing a method of applying pressure to the laser light irradiation unit in the stacking direction of the current collecting foils. [Figure 6] 10 is a schematic diagram roughly illustrating a laser welding method according to a third embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present technology will be described in detail below. Matters necessary for implementing the present technology (e.g., a method for assembling an electricity storage device, etc.) other than those specifically mentioned in this specification (e.g., a method for laser welding a current collector foil and a current collector of an electrode body) can be understood as design matters for a person skilled in the art based on prior art in the relevant field. The content of the present technology can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field.

[0009] Each drawing is a schematic drawing, and the dimensional relationships (length, width, thickness, etc.) do not necessarily reflect the actual dimensional relationships. Furthermore, in the drawings described below, the same reference numerals are used to designate components and parts that perform the same functions, and redundant explanations may be omitted or simplified. Furthermore, in this specification, when a numerical range is described as "A to B (where A and B are any numerical values)," this means "A or more and B or less," and also encompasses the meanings of "greater than A and less than B," "greater than A and B or less," and "greater than A and less than B."

[0010] In this specification, the term "electricity storage device" refers to a device that can be charged and discharged. Electricity storage devices include batteries such as primary batteries and secondary batteries (e.g., lithium ion secondary batteries and nickel-metal hydride batteries), and capacitors (physical batteries) such as electric double layer capacitors. Below, a non-aqueous electrolyte secondary battery, which is one embodiment of an electricity storage device manufactured by the manufacturing method disclosed herein, will be described. Note that the electricity storage device manufactured by the present technology is not limited to a non-aqueous electrolyte secondary battery.

[0011] 1 is a schematic cross-sectional view roughly illustrating the configuration of a nonaqueous electrolyte secondary battery 100 according to one embodiment. The nonaqueous electrolyte secondary battery 100 includes an electrode assembly 20, a case 30, a positive electrode 40, a negative electrode plate 70, and a nonaqueous electrolyte (not shown). The positive electrode 40 includes a positive electrode terminal 42, a positive electrode current collector 44, and a positive electrode plate 50. The negative electrode 60 includes a negative electrode terminal 62, a negative electrode current collector 64, and the negative electrode plate 70. Although not particularly limited, in this embodiment, the nonaqueous electrolyte secondary battery 100 is a lithium-ion secondary battery.

[0012] As shown in FIG. 1, the nonaqueous electrolyte secondary battery 100 is a rectangular sealed battery constructed by housing a flat electrode assembly (wound electrode assembly) 20 and a nonaqueous electrolyte (not shown) inside a case 30. The case 30 includes a case body 32 having an opening and a sealing member 34 that seals the opening. In this example, the sealing member 34 is plate-shaped. The sealing member 34 is provided with a positive electrode terminal 42 and a negative electrode terminal 62 for external connection. The sealing member 34 also includes a thin-walled safety valve 36 that is designed to release internal pressure in the case 30 when the internal pressure rises above a predetermined level. The case 30 also includes an injection port (not shown) for injecting the nonaqueous electrolyte. The case 30 is preferably made of a metal material that is high in strength, lightweight, and has good thermal conductivity. Examples of such metal materials include aluminum and steel.

[0013] FIG. 2 is an exploded view schematically illustrating the configuration of an electrode assembly 20 of a nonaqueous electrolyte secondary battery 100 according to one embodiment. In FIG. 2, the electrode assembly 20 is a wound electrode assembly in which a long sheet-like positive electrode plate 50 and a long sheet-like negative electrode plate 70 are stacked with two long sheet-like separators 80 interposed between them so that their longitudinal directions are aligned, and then wound around a winding axis WL. The positive electrode plate 50 includes a positive electrode current collector foil 52 and a positive electrode active material layer 54 arranged in the longitudinal direction on one or both sides (both sides in this case) of the positive electrode current collector foil 52. One edge of the positive electrode current collector foil 52 in the direction of the winding axis WL (i.e., the sheet width direction perpendicular to the longitudinal direction) is provided with a strip-shaped portion along the edge where the positive electrode active material layer 54 is not formed and the positive electrode current collector foil 52 is exposed (i.e., a positive electrode current collector foil exposed portion 52a). The negative electrode plate 70 includes a negative electrode current collector foil 72 and a negative electrode active material layer 74 arranged in the longitudinal direction on one or both sides (both sides in this example) of the negative electrode current collector foil 72. The other edge of the negative electrode current collector foil 72 in the winding axis WL direction (i.e., the edge opposite the positive electrode current collector foil exposed portion 52a) has a strip-shaped portion along the edge where the negative electrode active material layer 74 is not formed and the negative electrode current collector foil 72 is exposed (i.e., the negative electrode current collector foil exposed portion 72a). The positive electrode current collector foil 52 has a plurality of positive electrode current collector foil exposed portions 52a stacked in the thickness direction of the electrode body 20. The plurality of stacked positive electrode current collector foil exposed portions 52a are joined to the positive electrode current collector 44 by laser welding (i.e., a laser welded portion is provided). The negative electrode current collector foil 72 has a plurality of negative electrode current collector foil exposed portions 72a stacked in the thickness direction of the electrode body 20. The plurality of stacked negative electrode current collector foil exposed portions 72a are joined to the negative electrode current collector 64 by laser welding (i.e., laser welded portions are provided). The positive electrode current collector 44 is electrically connected to the positive electrode terminal 42 for external connection, thereby realizing electrical continuity between the inside and outside of the case 30 (see FIG. 1). Similarly, the negative electrode current collector 64 is electrically connected to the negative electrode terminal 62 for external connection, thereby realizing electrical continuity between the inside and outside of the case 30 (see FIG. 1). The positive electrode current collector 44 may be, for example, plate-shaped. The portion of the positive electrode current collector 44 that is joined to the positive electrode current collector foil exposed portion 52a may have a thickness of, for example, 0.5 mm to 3 mm. The negative electrode current collector 64 may be, for example, plate-shaped.The thickness of the portion of the negative electrode current collector 64 that is joined to the exposed portion 72a of the negative electrode current collector foil may be, for example, 0.5 to 3 mm.

[0014] An insulating member (not shown) for insulating the positive electrode terminal 42 from the sealing member 34 can be disposed between the positive electrode terminal 42 and the sealing member 34. The insulating member is made of, for example, a resin member having electrical insulation properties. Examples of such resins include polyolefin resins such as polypropylene (PP), fluorinated resins such as perfluoroalkoxyethylene copolymer (PFA) and polytetrafluoroethylene (PTFE), and polyphenylene sulfide (PPS). The insulating members may also be disposed between the negative electrode terminal 62 and the sealing member 34, between the positive electrode current collector 44 and the sealing member 34, and between the negative electrode current collector 64 and the sealing member 34.

[0015] The positive electrode current collector foil 52 may be, for example, an aluminum foil. The thickness of the positive electrode current collector foil 52 may be, for example, 5 to 20 μm. The positive electrode active material layer 54 includes a positive electrode active material. As the positive electrode active material, a known positive electrode active material used in lithium ion secondary batteries may be used, for example, a lithium composite metal oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNiO2, LiCoO2, LiFeO2, LiMn2O4, LiNi 0.5 Mn 1.5 Examples of the positive electrode active material layer 54 include LiCrMnO4, LiCrMnO4, LiFePO4, etc. The positive electrode active material layer 54 may also include a conductive material, a binder, etc. Suitable conductive materials include carbon black such as acetylene black (AB) and other carbon materials (such as graphite). Suitable binders include polyvinylidene fluoride (PVDF), for example. The positive electrode active material layer 54 can be formed by dispersing the positive electrode active material and materials (such as a conductive material and a binder) used as needed in an appropriate solvent (for example, N-methyl-2-pyrrolidone: NMP) to prepare a paste-like (or slurry-like) composition (positive electrode mixture paste), applying an appropriate amount of the composition to the surface of the positive electrode current collector foil 52, and drying the composition.

[0016] The negative electrode current collector foil 72 may be, for example, a copper foil. The thickness of the negative electrode current collector foil 72 may be, for example, 5 to 20 μm. The negative electrode active material layer 74 includes a negative electrode active material. As the negative electrode active material, for example, a carbon material such as graphite, hard carbon, or soft carbon may be used. The negative electrode active material layer 74 may further include a binder, a thickener, or the like. As the binder, for example, styrene butadiene rubber (SBR) or the like may be used. As the thickener, for example, carboxymethyl cellulose (CMC) or the like may be used. The negative electrode active material layer 74 can be formed, for example, by dispersing the negative electrode active material and materials (such as a binder) used as needed in an appropriate solvent (such as ion-exchanged water) to prepare a paste-like (or slurry-like) composition, applying an appropriate amount of the composition to the surface of the negative electrode current collector foil 72, and drying it.

[0017] As the separator 80, various conventional microporous sheets can be used, such as microporous resin sheets made of resins such as polyethylene (PE) and polypropylene (PP). Such microporous resin sheets may have a single-layer structure or a multi-layer structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). Separator 80 may also have a heat-resistant layer (HRL).

[0018] Conventional nonaqueous electrolytes can be used, for example, nonaqueous electrolytes containing a supporting salt in an organic solvent (nonaqueous solvent). Nonaqueous solvents include aprotic solvents such as carbonates, esters, and ethers. Among these, carbonates, such as ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC), are preferred. Alternatively, fluorine-based solvents, such as fluorinated carbonates, such as monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC), monofluoromethyl difluoromethyl carbonate (F-DMC), and trifluorodimethyl carbonate (TFDMC), are preferred. These nonaqueous solvents can be used alone or in appropriate combinations of two or more. Lithium salts, such as LiPF, LiBF, and LiClO, are preferred as supporting salts. The concentration of the supporting salt is not particularly limited, but is preferably about 0.7 mol / L or more and 1.3 mol / L or less. The nonaqueous electrolyte may contain components other than the nonaqueous solvent and supporting salt described above, as long as the effects of the present technology are not significantly impaired. For example, the nonaqueous electrolyte may contain various additives such as a gas generating agent, a film-forming agent, a dispersant, and a thickener.

[0019] An electricity storage device such as the nonaqueous electrolyte secondary battery 100 can be used for various purposes, and can be suitably used, for example, as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car, a truck, etc. The type of vehicle is not particularly limited, and examples thereof include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), and a battery electric vehicle (BEV).

[0020] The shape of the power storage device disclosed herein is not limited to a rectangular shape, and may be a coin type, a button type, a cylindrical type, or the like, and may also be configured as a laminated case type battery. The battery disclosed herein may also be a polymer battery using a polymer electrolyte instead of a nonaqueous electrolyte, an all-solid-state battery using a solid electrolyte, or the like.

[0021] A method for manufacturing the electricity storage device disclosed herein is described below. The manufacturing method disclosed herein includes a welding step of joining multiple stacked current collecting foils of an electrode assembly to a current collector (positive electrode current collector 44 or negative electrode current collector 64) by laser welding. Specifically, the welding step includes, for at least one of the positive and negative electrodes, pressing the multiple stacked current collecting foils against the current collector, applying tension to the pressed multiple stacked current collecting foils along a predetermined linear direction, and irradiating a portion of the surface of the multiple stacked current collecting foils pressed against the current collector that is located in the predetermined linear direction with laser light. In this way, applying tension to the multiple stacked current collecting foils in the predetermined linear direction can more uniformly smooth out wrinkles in the current collecting foils. This reduces wrinkles in the current collecting foils pressed against the current collector, thereby reducing gaps between the current collecting foils. As a result, welding stability can be improved in the laser welding between the multiple stacked current collecting foils pressed against the current collector and the current collector. For example, it is possible to suppress the occurrence of spatters, blowholes, breakage of the current collecting foils, etc., which may occur due to gaps between the current collecting foils. Furthermore, in addition to the welding step, the manufacturing method disclosed herein may include, for example, a preparation step, an assembly step, a housing step, a sealing step, a liquid injection step, etc., in any order as necessary.

[0022] In the preparation step, for example, an electrode assembly is prepared. The electrode assembly may be a wound electrode assembly such as the electrode assembly 20 described above, or a laminated electrode assembly in which multiple positive electrode plates and multiple negative electrode plates are alternately stacked with separators interposed therebetween. Here, the above-described electrode assembly 20 will be used as an example for explanation.

[0023] Next, the welding step will be described. Here, a method of laser welding a current collector foil (positive current collector foil 52) and a current collector (positive current collector 44) in the positive electrode 40 will be described as an example. FIG. 3 is a schematic diagram roughly illustrating a laser welding method according to the first embodiment. As shown in FIG. 3, first, a plurality of positive current collector foils 52 (specifically, exposed portions 52a of the positive current collector foil) are stacked. The number of positive current collector foils 52 is not particularly limited, but may be, for example, about 10 to 120 sheets, or about 20 to 100 sheets. In this embodiment, a first pressure unit 200 is provided that presses the plurality of stacked positive current collector foils 52 in the stacking direction, and a second pressure unit 300 is provided that presses the plurality of stacked positive current collector foils 52 in the stacking direction at a position different from the first pressure unit 200. In this embodiment, the first pressing unit 200 sandwiches the plurality of stacked positive current collector foil exposed portions 52a in the stacking direction between a first upper jig 210 disposed on one surface of the plurality of stacked positive current collector foil exposed portions 52a and a first lower jig 220 disposed on the other surface of the plurality of stacked positive current collector foil exposed portions 52a. The second pressing unit 300 sandwiches the plurality of stacked positive current collector foil exposed portions 52a in the stacking direction between a second upper jig 310 disposed on one surface of the plurality of stacked positive current collector foil exposed portions 52a and a second lower jig 320 disposed on the other surface of the plurality of stacked positive current collector foil exposed portions 52a. The first pressing unit 200 preferably presses the plurality of stacked positive current collector foil exposed portions 52a in the stacking direction so that there are no gaps between the plurality of stacked positive current collector foil exposed portions 52a. Also, it is preferable that the second pressure applying unit 300 also applies pressure to the plurality of stacked positive current collector foil exposed portions 52a in the stacking direction so as to eliminate gaps between the plurality of stacked positive current collector foil exposed portions 52a. Although the first upper jig 210, the first lower jig 220, the second upper jig 310, and the second lower jig 320 are illustrated here as independent jigs, they may be integrated into an integrated jig in any combination as long as the first pressure section 200 and the second pressure section 300 can be provided.

[0024] Next, the plurality of stacked positive current collector foil exposed portions 52a are pressed against the surface of the positive current collector 44 while being sandwiched between the first pressing unit 200 and the second pressing unit 300. The portion of the plurality of stacked positive current collector foil exposed portions 52a pressed against the surface of the positive current collector 44 is the portion between the first pressing unit 200 and the second pressing unit 300. It is preferable to prevent gaps from forming between the plurality of stacked positive current collector foil exposed portions 52a and the surface of the positive current collector 44. This improves welding stability. A laser beam irradiation portion 500, onto which laser beam L is irradiated, is present on the surface of the plurality of stacked positive current collector foil exposed portions 52a pressed against the surface of the positive current collector 44. The laser beam irradiation portion 500 is, in other words, a portion to be laser welded.

[0025] Next, an external force is applied in a direction in which the first pressing unit 200 and the second pressing unit 300 are aligned (linear direction ST in FIG. 3 ) to stretch the multiple stacked positive current collector foil exposed portions 52a, thereby applying tension. That is, the portion in contact with the positive current collector 44 is stretched (tensioned). The method of applying tension is not particularly limited, but for example, tension can be achieved by applying an external force (pulling) the multiple stacked positive current collector foil exposed portions 52a sandwiched between the first pressing unit 200 in the direction opposite the second pressing unit 300 side (to the right in FIG. 3 ). For example, tension can be applied to the multiple stacked positive current collector foil exposed portions 52a by moving the first upper jig 210 in the direction opposite the second pressing unit 300 side while the first lower jig 220 is fixed. Alternatively, the first lower jig 220 may be moved in the direction away from the second pressing unit 300 while the first upper jig 210 remains fixed, thereby applying tension to the plurality of stacked positive current collector foil exposed portions 52a. Alternatively, both the first upper jig 210 and the first lower jig 220 may be moved in the direction away from the second pressing unit 300, thereby applying tension to the plurality of stacked positive current collector foil exposed portions 52a. That is, the first pressing unit 200 may clamp and pull the plurality of stacked positive current collector foil exposed portions 52a. On the other hand, the second pressing unit 300 may fix the plurality of stacked positive current collector foil exposed portions 52a while applying pressure in the stacking direction. Furthermore, similarly to the above-described first pressing unit 200, tension may be applied to the plurality of stacked positive electrode current collector foil exposed portions 52a by moving the second upper jig 310 and / or the second lower jig 320 in the direction opposite to the first pressing unit 200 (to the left in FIG. 3 ). When tension is applied by moving the first pressing unit 200 and / or the second pressing unit 300 in this manner, the tension is generated in the linear direction in which the first pressing unit 200 and the second pressing unit 300 are aligned. This smooths out wrinkles in the plurality of stacked positive electrode current collector foil exposed portions 52a between the first pressing unit 200 and the second pressing unit 300, thereby reducing gaps in the stacking direction of the stacked positive electrode current collector foil exposed portions 52a.

[0026] It is preferable that tension be applied to the multiple stacked positive current collector foil exposed portions 52a only in one linear direction (unidirectional). Applying tension in multiple directions or in the radial direction of a circle can easily cause wrinkles to form in the multiple stacked positive current collector foil exposed portions 52a. Furthermore, applying tension in only one linear direction allows the stacked positive current collector foil exposed portions 52a to adhere more uniformly in the stacking direction, and effectively reduces gaps between the stacked positive current collector foil exposed portions 52a.

[0027] In the method described above, tension is applied to the plurality of stacked positive current collector foil exposed portions 52a after they are pressed against the positive current collector 44, but the order is not limited thereto. For example, tension may be applied to the plurality of stacked positive current collector foil exposed portions 52a, and then the plurality of stacked positive current collector foil exposed portions 52a may be pressed against the positive current collector 44. By applying tension to the plurality of stacked positive current collector foil exposed portions 52a before pressing them against the positive current collector 44, the plurality of stacked positive current collector foil exposed portions 52a can be pressed against the positive current collector 44 in a state where wrinkles in the plurality of stacked positive current collector foil exposed portions 52a are smoothed out, and therefore the gap between the positive current collector foil exposed portions 52a and the positive current collector 44 can be suitably reduced.

[0028] The first pressing unit 200 and the second pressing unit 300 may be provided after the plurality of stacked positive electrode current collector foil exposed portions 52a and positive electrode current collector 44 are stacked together. In Fig. 3, the first pressing unit 200 and the second pressing unit 300 clamp the plurality of stacked positive electrode current collector foil exposed portions 52a by directly applying jigs to both sides in the stacking direction, but as in other embodiments described later, the surfaces of the plurality of stacked positive electrode current collector foil exposed portions 52a and the positive electrode current collector 44 may be clamped together in a state in which the plurality of stacked positive electrode current collector foil exposed portions 52a and the positive electrode current collector 44 are stacked together.

[0029] Next, a laser beam L is irradiated onto the surface of the plurality of stacked positive current collector foil exposed portions 52a pressed against the positive current collector 44. At this time, the laser beam L is irradiated onto at least a portion of a region of the surface of the plurality of stacked positive current collector foil exposed portions 52a pressed against the positive current collector 44 that is located in the linear direction in which tension is generated. In other words, the laser beam irradiator 500 is located in the linear direction ST in which tension is generated. This allows the plurality of stacked positive current collector foil exposed portions 52a and the positive current collector 44 to be laser welded together. Note that the portion to be laser welded (the laser beam irradiator 500) may be one location, or multiple locations.

[0030] The type of laser light L is not particularly limited, and examples thereof include a YAG laser, a CO2 laser, a semiconductor laser, a disk laser, a fiber laser, etc. The laser output, laser irradiation time, amount of heat input by the laser, etc. are appropriately adjusted depending on the materials of the current collecting foil, current collector, etc., and are not particularly limited.

[0031] The method for laser welding the negative electrode current collector foil 72 and the negative electrode current collector 64 in the negative electrode 60 may be the same as the method for laser welding the positive electrode current collector foil 52 and the positive electrode current collector 44 described above. For example, this can be understood by replacing "positive electrode" with "negative electrode" in the above description. In this embodiment, the negative electrode current collector foil 72 (more specifically, the multiple laminated negative electrode current collector foil exposed portions 72a) and the negative electrode current collector 64 are laser welded together in the same manner as the positive electrode 40. In this manner, the positive electrode current collector 44 and the negative electrode current collector 64 are attached to the electrode assembly 20.

[0032] In the assembly process, for example, a positive electrode current collector 44 attached to the electrode body 20 is joined to a positive electrode terminal 42 attached to the sealing member 34, and a negative electrode current collector 64 attached to the electrode body 20 is joined to a negative electrode terminal 62 attached to the sealing member 34, thereby constructing an assembly including the sealing member 34, electrode body 20, positive electrode terminal 42, positive electrode current collector 44, negative electrode terminal 62, and negative electrode current collector 64. The attachment method for each component may be according to a known method, and the components can be joined by, for example, crimping, laser welding, ultrasonic welding, resistance welding, or the like. Note that the current collector and terminal of each electrode do not need to be joined after the welding process, and may be joined in advance before the welding process.

[0033] In the accommodation step, for example, the electrode body 20 is accommodated inside the case body 12. Here, the electrode body 20 of the assembled structure constructed above is accommodated in the case body 12, and the sealing member 34 is overlapped with the opening of the case body 12. At this time, an insulating film that has been formed into a bag or box shape in advance may be placed between the electrode body 20 and the case body 12.

[0034] In the sealing step, for example, the overlapping portion of the sealing member 34 and the case body 12 is welded to seal the case body 12. The welding method may be a conventionally known method, for example, laser welding.

[0035] In the liquid injection step, a non-aqueous electrolyte is injected according to a conventionally known method through an injection port provided in the case 30. Note that depending on the type of electricity storage device, the liquid injection step may be omitted.

[0036] Thereafter, for example, initial charging, aging treatment, and the like are performed under predetermined conditions to produce a usable non-aqueous electrolyte secondary battery 100 (electricity storage device).

[0037] Another embodiment of the laser welding method in the welding step will be described below. FIG. 4 is a schematic diagram outlining a laser welding method according to a second embodiment. FIG. 5 is a schematic diagram showing a method of applying pressure with a laser light irradiation unit in the stacking direction of the current collector foil. As shown in FIG. 4, in the second embodiment, a first pressure unit 200 and a second pressure unit 300 are provided at a portion where a plurality of stacked positive current collector foil exposed portions 52a and positive current collectors 44 are overlapped. The positive current collectors 44 are also disposed on a base 400. The base 400 is a portion on which the workpieces to be welded are placed during laser welding. The base 400 may be similar to bases used in conventionally known laser welding.

[0038] In the first pressure applying unit 200, a first roller 230 is placed on the surface of the plurality of stacked positive current collector foil exposed portions 52a. The plurality of stacked positive current collector foil exposed portions 52a and positive current collectors 44 are sandwiched between the first roller 230 and a base 400, and the plurality of stacked positive current collector foil exposed portions 52a is pressed in the stacking direction. In the second pressure applying unit 300, a second roller 330 is placed on the surface of the plurality of stacked positive current collector foil exposed portions 52a. The plurality of stacked positive current collector foil exposed portions 52a and positive current collectors 44 are sandwiched between the second roller 330 and the base 400, and the plurality of stacked positive current collector foil exposed portions 52a is pressed in the stacking direction. The first pressure unit 200 and / or the second pressure unit 300 may be provided at a position where the positive electrode current collector 44 is not disposed (see the arrangement of the first pressure unit 200 and the second pressure unit 300 in FIG. 3).

[0039] As shown in FIG. 4, the first roller 230 can be configured to be rotatable in place around an axis 232. By rotating the first roller 230 along a predetermined linear direction ST in which tension is applied, tension is applied to the multiple stacked positive electrode current collector foil exposed portions 52a. Specifically, the first roller 230 can be rotated so that the first roller 230 stretches the positive electrode current collector foil exposed portions 52a toward the opposite side from the laser light irradiation unit 500 at the portion where the first roller 230 contacts the positive electrode current collector foil exposed portions 52a (counterclockwise in FIG. 4). The first roller 230 may continue to rotate, or the rotation of the first roller 230 may stop when the forces in the linear direction ST are balanced.

[0040] The second roller 330 may have a configuration similar to that of the first roller 230, and may be configured to be rotatable around an axis 332. When the first roller 230 is rotated, the second roller 330 does not need to be rotated. That is, it is sufficient to pressurize the multiple stacked positive electrode current collector foil exposed portions 52a in the stacking direction, and fix the positions of the multiple stacked positive electrode current collector foil exposed portions 52a. Therefore, in this case, the second upper jig 310 as in the first embodiment described above may be disposed in the second pressure unit 300 instead of the second roller 330. Furthermore, when rotating the first roller 230, the second roller 330 may be rotated along a predetermined linear direction ST in which tension is applied. Specifically, the second roller 330 may be rotated (clockwise in FIG. 4 ) so that the second roller 330 extends the positive electrode current collector foil exposed portion 52a in the area where the second roller 330 contacts the positive electrode current collector foil exposed portion 52a toward the opposite side from the laser light irradiation unit 500. The rotation direction of the first roller 230 and the rotation direction of the second roller 330 may be opposite.

[0041] As shown in FIG. 5 , before applying tension to the plurality of stacked positive current collector foil exposed portions 52a, it is preferable to move the first pressure applying unit 200 along the linear direction ST so as to pass through the laser light irradiation unit 500 (the arrow in FIG. 5 indicates the movement direction of the first pressure applying unit 200). In other words, it is preferable that the laser light irradiation unit 500 applies pressure to the plurality of stacked positive current collector foil exposed portions 52a in the stacking direction, and then continuously applies tension to the plurality of stacked positive current collector foil exposed portions 52a. Note that, when moving the first pressure applying unit 200, it is preferable to fix the plurality of stacked positive current collector foil exposed portions 52a with the second pressure applying unit 300. This can further reduce gaps between the plurality of stacked positive current collector foil exposed portions 52a at the laser light irradiation unit 500. Note that this process is not limited to the second embodiment and can be adopted in other embodiments as well.

[0042] In the second embodiment, the first roller 230 is rotated along the linear direction ST to apply tension to the plurality of stacked positive current collector foil exposed portions 52a to smooth out wrinkles in the laser light irradiation portions 500, and laser welding is achieved by irradiating the laser light irradiation portions 500 with laser light L. In the second embodiment, the rotation of the first roller 230 applies tension to the plurality of stacked positive current collector foil exposed portions 52a only along the linear direction ST, and therefore the tension is applied more uniformly, making it easier to smooth out wrinkles in the positive current collector foil exposed portions 52a and suitably reducing gaps between the stacked positive current collector foil exposed portions 52a.

[0043] Fig. 6 is a schematic diagram roughly illustrating a laser welding method according to the third embodiment. In Fig. 6, the ends of the multiple stacked positive current collector foil exposed portions 52a are arranged to extend beyond the end of the positive current collector 44 in the linear direction ST in which tension is applied. In the first pressing unit 200, a first pressing plate 240 is arranged on the surface of the multiple stacked positive current collector foil exposed portions 52a. In addition, in this example, in the second pressing unit 300, a second pressing plate 340 is arranged on the surface of the multiple stacked positive current collector foil exposed portions 52a.

[0044] The first presser plate 240 is disposed such that an opposing surface 242 that faces the surface of the plurality of stacked positive current collector foil exposed portions 52a is inclined in the linear direction ST so that the end sides of the plurality of stacked positive current collector foil exposed portions 52a are lowered. Next, the first presser plate 240 applies pressure in the stacking direction of the plurality of stacked positive current collector foil exposed portions 52a so that the opposing surface 242 of the first presser plate 240 contacts both the plurality of stacked positive current collector foil exposed portions 52a that are stacked on the end of the positive current collector 44 and the end portions of the plurality of stacked positive current collector foil exposed portions 52a that protrude from the end of the positive current collector 44. At this time, the first presser plate 240 applies pressure to the plurality of stacked positive current collector foil exposed portions 52a along the direction in which the positive current collector 44 and the plurality of stacked positive current collector foil exposed portions 52a are stacked together (the up-and-down direction in FIG. 6 ). 6 indicates the direction of pressure application by the first presser plate 240 or the second presser plate 340. By tilting the opposing surface 242 of the first presser plate 240 as described above, the vector of the pressure applied by the first presser plate 240 is resolved into a force that applies pressure to the multiple stacked positive current collector foil exposed portions 52a in the stacking direction, and a force in a direction that pulls the multiple stacked positive current collector foil exposed portions 52a (the direction opposite to the second presser member 300 side in the linear direction ST). As a result, tension can be applied to the multiple stacked positive current collector foil exposed portions 52a along the linear direction ST.

[0045] The inclination angle θ of the facing surface 242 of the first pressing plate 240 relative to the positive current collector foil exposed portion 52a is not particularly limited, but may be, for example, 5° or more, 10° or more, or 15° or more. The larger the inclination angle θ, the stronger the tension generated in the multiple stacked positive current collector foil exposed portions 52a, making it possible to more effectively smooth out wrinkles in the multiple stacked positive current collector foil exposed portions 52a. The inclination angle θ may be, for example, 75° or less, 60° or less, or 45° or less. If the inclination angle θ is too large, the force pressing the multiple stacked positive current collector foil exposed portions 52a in the stacking direction becomes weak, which may result in insufficient fixation of the multiple stacked positive current collector foil exposed portions 52a during laser welding, thereby reducing welding stability.

[0046] 6, the first pressing plate 240 has the opposing surface 242 as an inclined surface, but this is not limiting. The first pressing plate 240 may be, for example, a rectangular parallelepiped plate. In this case, the opposing surface 242 of the first pressing plate 240 may be inclined at an inclination angle θ with respect to the surface of the plurality of stacked positive current collector foil exposed portions 52a, and the plurality of stacked positive current collector foil exposed portions 52a may be pressed from the stacking direction.

[0047] The second presser plate 340 in the second pressing unit 300 may have a configuration similar to that of the first presser plate 240. An opposing surface 342 of the second presser plate 340 that faces the surface of the plurality of stacked positive current collector foil exposed portions 52a is understood to correspond to the opposing surface 242 of the first presser plate 240. The pressing method in the second pressing unit 300 may be similar to that of the first pressing unit 200. Note that in the present embodiment, the second presser plate 340 is disposed in the second pressing unit 300, but the second pressing unit 300 may simply press the plurality of stacked positive current collector foil exposed portions 52a in the stacking direction to fix the plurality of stacked positive current collector foil exposed portions 52a, and aspects of the second pressing unit 300 in other embodiments may be adopted as appropriate.

[0048] 6, first presser plate 240 and second presser plate 340 are independent of each other, but they may be formed from a single plate having portions corresponding to both opposing surfaces 242 of first presser plate 240 and opposing surfaces 342 of second presser plate 340. For example, it may be a plate having a through-hole for passing laser light L, and having a pair of inclined surfaces (the pair of inclined surfaces corresponding to opposing surfaces 242 of first presser plate 240 and opposing surfaces 342 of second presser plate 340) facing each other across the through-hole in a predetermined linear direction.

[0049] Several embodiments of the manufacturing method disclosed herein have been described above. The above embodiments are merely examples. The present technology can be implemented in various other forms. The technology described in the claims includes various modifications and alterations of the above-exemplified embodiments. For example, it is possible to replace part of the above-described embodiments with other modified embodiments, or to add other modified embodiments to the above-described embodiments. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate.

[0050] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Item 1: A method for manufacturing an electricity storage device including a positive electrode including a plurality of stacked positive electrode current collector foils and a positive electrode current collector connected to the stacked positive electrode current collector foils, and a negative electrode including a plurality of stacked negative electrode current collector foils and a negative electrode current collector connected to the stacked negative electrode current collector foils, the method comprising: applying tension to the pressed stacked current collector foils along a predetermined linear direction while pressing the plurality of stacked current collector foils against the current collector, at least one of the positive electrode and the negative electrode; and irradiating a portion of the surface of the plurality of stacked current collector foils pressed against the current collector with laser light, the portion being located in the predetermined linear direction. Item 2: The manufacturing method according to item 1, further comprising providing a first pressure applying unit that applies pressure to the plurality of stacked current collecting foils in the stacking direction in the predetermined linear direction, and a second pressure applying unit that applies pressure to the plurality of stacked current collecting foils in the stacking direction at a position different from the first pressure applying unit, and applying tension to the plurality of stacked current collecting foils located between the first pressure applying unit and the second pressure applying unit. Item 3: The manufacturing method according to Item 2, wherein the first pressure applying unit clamps the plurality of stacked current collecting foils in the stacking direction, and applies tension to the plurality of stacked current collecting foils by applying an external force in a direction opposite to the second pressure applying unit. Item 4: The manufacturing method according to Item 2 or 3, wherein in the first pressure unit, a roller is placed on the surface of the plurality of stacked current collecting foils, and tension is applied to the plurality of stacked current collecting foils by rotating the roller along the predetermined linear direction. Item 5: The manufacturing method according to Item 2 or 3, including overlapping the plurality of stacked current collecting foils in the predetermined linear direction so that their ends extend beyond the end of the current collector, and in the first pressure unit, arranging a presser plate on the current collecting foil side so that a surface of the presser plate facing the current collecting foil is inclined with respect to a surface of the current collecting foil, and using the opposing surface to pressurize the ends of the plurality of stacked current collecting foils extending beyond the end of the current collector and the plurality of stacked current collecting foils located on the end of the current collector. Item 6: The manufacturing method according to any one of Items 2 to 5, further comprising, before irradiating the laser light, moving the first pressure applying unit along the linear direction so as to pass through the surfaces of the plurality of stacked current collecting foils onto which the laser light is irradiated. [Explanation of symbols]

[0051] 20 Electrode body 30 cases 40 positive electrode 42 Positive terminal 44 Positive electrode current collector 50 positive electrode plate 52 Positive electrode current collector foil 52a Positive electrode current collector foil exposed part 60 negative electrode 62 Negative terminal 64 Negative electrode current collector 70 negative electrode plate 72 Negative electrode current collecting foil 72a Exposed part of negative electrode current collector foil 80 Separator 100 Nonaqueous electrolyte secondary battery 200 First pressure section 210 First upper jig 220 First lower jig 230 First Roller 240 First holding plate 300 Second pressure section 310 Second upper jig 320 Second lower jig 330 Second Roller 340 Second holding plate 400 base 500 Laser light irradiation unit

Claims

1. a positive electrode including a plurality of stacked positive electrode current collector foils and a positive electrode current collector connected to the stacked positive electrode current collector foils; a negative electrode including a plurality of stacked negative electrode current collector foils and a negative electrode current collector connected to the stacked negative electrode current collector foils; A method for manufacturing an electricity storage device comprising: overlapping the plurality of stacked current collecting foils in at least one of the positive electrode and the negative electrode so that their ends extend beyond the ends of the current collector, and applying tension to the pressed plurality of stacked current collecting foils along a predetermined linear direction while pressing the plurality of stacked current collecting foils against the current collector; and irradiating a laser beam onto a portion of a surface of the plurality of stacked current collecting foils pressed against the current collector, the portion being positioned in the predetermined linear direction; It encompasses applying tension along the predetermined linear direction to the pressed stacked current collecting foils includes providing a first pressure unit that presses the stacked current collecting foils in the stacking direction in the predetermined linear direction, and a second pressure unit that presses the stacked current collecting foils in the stacking direction at a position different from the first pressure unit, and applying tension to the stacked current collecting foils located between the first pressure unit and the second pressure unit, When pressing the plurality of stacked current collecting foils against the current collector, the first pressure unit places a first pressure plate on the current collecting foil side, and the surface of the first pressure plate facing the current collecting foil is inclined at a predetermined angle with respect to the surface of the current collecting foil, and the opposing surface inclined at the predetermined angle is pressed against the current collecting foil, thereby applying pressure to an area from an end of the plurality of stacked current collecting foils that protrudes from the end of the current collector to the plurality of stacked current collecting foils located on the end of the current collector. Manufacturing method.

2. A manufacturing method as described in claim 1, wherein, when the plurality of stacked current collecting foils are pressed against the current collector, a second pressure plate is placed on the side of the current collecting foil in the second pressure section, and the surface of the second pressure plate facing the current collecting foil is inclined at the predetermined angle relative to the surface of the current collecting foil, and the facing surface of the second pressure plate inclined at the predetermined angle is pressed against the current collecting foil, thereby applying pressure to the area from the ends of the plurality of stacked current collecting foils that extend beyond the end of the current collector to the plurality of stacked current collecting foils located on the end of the current collector.

3. 3. The manufacturing method according to claim 1, wherein tension is applied to the plurality of stacked current collecting foils by applying a pulling force in a direction opposite to the second pressure unit while the plurality of stacked current collecting foils are clamped in the stacking direction by the first pressure unit.

4. A manufacturing method as described in claim 1 or 2, wherein the specified angle is greater than or equal to 5° and less than or equal to 75°.

5. A manufacturing method described in claim 1 or 2, wherein the surface of the collector in the portion where the multiple laminated collector foils are overlapped is flat.

6. 3. The manufacturing method according to claim 1, further comprising, before the laser light is irradiated, moving the first pressure unit along the linear direction so as to pass through surfaces of the plurality of stacked current collecting foils that are to be irradiated with the laser light.

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