Method for manufacturing an electricity storage device

Abstract

To provide a technique capable of improving welding stability between a current collector foil and a current collector.SOLUTION: A manufacturing method of a power storage device disclosed herein includes: preparing an electrode body that includes a laminated portion 52s including a plurality of laminated current collector foils of a first electrode, a first conductive member 46, and a second conductive member 48 having a size smaller than that of the first conductive member 46; disposing the second conductive member 48 on a first surface 46a of the first conductive member 46, and furthermore, disposing part of the laminated portion 52s on the second conductive member 48; pressing, against the second conductive member 48, a portion disposed on the second conductive member 48 in the laminated portion 52s by pressing, toward the first surface 46a, a portion outside a portion disposed on the second conductive member 48 in the laminated portion 52s; and irradiating a portion pressed against the second conductive member 48 in the laminated portion 52s with laser and laser-welding the laminated portion 52s and the first conductive member 46 while the second conductive member 48 is interposed therebetween.SELECTED DRAWING: Figure 5

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 technology that improves the welding stability between a current collecting foil and a current collector. [Means for solving the problem]

[0006] One aspect of a manufacturing method for an electricity storage device disclosed herein includes preparing an electrode body having a laminated portion in which a plurality of current collecting foils of a first electrode are stacked, a first conductive member, and a second conductive member smaller than the first conductive member; arranging the second conductive member on a first surface of the first conductive member, and further arranging a portion of the laminated portion of the current collecting foil on the second conductive member; pressing a portion of the laminated portion outside the portion arranged on the second conductive member toward the first surface, thereby pressing the portion of the laminated portion arranged on the second conductive member against the second conductive member; and irradiating a laser onto the portion of the laminated portion pressed against the second conductive member, and laser welding the laminated portion and the first conductive member with the second conductive member interposed therebetween. According to this manufacturing method, the region of the laminated portion, in which multiple current collecting foils are stacked, that overlaps with the second conductive member is pressed against the second conductive member, reducing the gap between the current collecting foils in that region. By irradiating the laminated portion in that region with a laser in this state, the occurrence of spattering, blowholes, foil breakage, etc. is suppressed, and welding stability is improved. [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 flowchart outlining an example of a manufacturing method disclosed herein. [Figure 4] 1A to 1C are schematic diagrams for explaining a preparation step and an arrangement step. [Figure 5] 5A and 5B are schematic diagrams for explaining a pressing step and a welding step. [Figure 6] FIG. 2 is a schematic diagram of the configuration in the vicinity of a laser welded portion. [Figure 7] 10A and 10B are schematic diagrams for explaining a preparation step and an arrangement step in the first modified example. [Figure 8] 10A and 10B are schematic diagrams for explaining a preparation step and an arrangement step in the second modified example. 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] FIG. 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 first electrode, a second electrode, and a nonaqueous electrolyte (not shown). In this embodiment, the first electrode is a positive electrode 40, and the second electrode is a negative electrode 60. 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 a negative electrode plate 70. Note that the first electrode may be a negative electrode, and the second electrode may be a positive electrode. 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 includes 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 case) 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).

[0014] The positive current collector foil 52 has a laminated portion 52s in which a plurality of positive current collector foil exposed portions 52a are laminated in the thickness direction of the electrode assembly 20. A portion of the laminated portion 52s is joined to the positive current collector 44 by laser welding. That is, the laminated portion 52s and the positive current collector 44 are connected (joined) via a laser weld. The laser weld corresponds to a weld 300 (see FIG. 6) described below, and will be described in detail there. The number of laminations of the positive current collector foil 52 (positive current collector foil exposed portions 52a) in the laminated portion 52s can be, for example, approximately 10 to 120, or 20 to 100. The negative current collector foil 72 has a laminated portion 72s in which a plurality of negative current collector foil exposed portions 72a are laminated in the thickness direction of the electrode assembly 20. A portion of the laminated portion 72s is joined to the negative current collector 64, for example, by laser welding. That is, the laminated portion 72s and the negative electrode current collector 64 may be connected (joined) via a laser welded portion. The number of laminations of the negative electrode current collector foil 72 (negative electrode current collector foil exposed portion 72a) in the laminated portion 72s may be, for example, about 10 to 120, or about 20 to 100. The joining between the current collector foil and the current collector in the negative electrode 60 may be the same as or different from that in the positive electrode 40. For example, the joining between the current collector foil and the current collector in the negative electrode 60 may be an ultrasonic joint, a resistance weld, or the like.

[0015] 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). As will be described in detail later, the positive electrode current collector 44 has a main body portion 46A and a protruding portion 48A (see FIG. 6). The negative electrode current collector 64 may have the same configuration as the positive electrode current collector 44, or may have a different configuration. For example, the negative electrode current collector 64 may be plate-shaped. The thickness of the portion of the negative electrode current collector 64 joined to the laminated portion 72s may be, for example, 0.5 to 3 mm. The negative electrode current collector 64 is preferably made of metal, and may be made of, for example, copper or a copper alloy.

[0016] At least a portion of the positive electrode terminal 42 is exposed on the outer surface side of the sealing member 34. This exposed portion is a portion that can be connected to an external member (e.g., a bus bar, an external conductive member). The positive electrode terminal 42 is, for example, inserted into a through hole provided in the sealing member 34, and a portion of it is disposed inside the case 30. Inside the case 30, the positive electrode terminal 42 and the positive electrode current collector 44 can be electrically connected. The positive electrode terminal 42 is made of, for example, a metal, and preferably made of aluminum or an aluminum alloy. The configuration of the negative electrode terminal 62 may be the same as that of the positive electrode terminal 42. The negative electrode terminal 62 is made of, for example, a metal, and preferably made of copper or a copper alloy.

[0017] 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.

[0018] 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 1.5Examples 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.

[0019] 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.

[0020] 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).

[0021] 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.

[0022] 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).

[0023] 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.

[0024] A method for manufacturing the electricity storage device disclosed herein will be described below. FIG. 3 is a flowchart roughly illustrating an example of the manufacturing method disclosed herein. As shown in FIG. 3, the manufacturing method disclosed herein may include a preparation step S10, an arrangement step S20, a pressing step S30, and a welding step S40. In addition to these steps, the manufacturing method disclosed herein may also include other steps at any stage. For example, it may include a housing step, a sealing step, a liquid injection step, etc.

[0025] Fig. 4 is a schematic diagram illustrating the preparation step S10 and the arrangement step S20. Fig. 5 is a schematic diagram illustrating the pressing step S30 and the welding step S40. Fig. 6 is a schematic diagram of the configuration in the vicinity of the laser welded portion. In the drawings, the symbol X indicates the horizontal direction, and the symbol Y indicates the vertical direction. The symbol Y may be the direction in which the first conductive member 46 and the second conductive member 48 overlap (are stacked). Furthermore, the symbol Y is preferably the vertical direction.

[0026] In the manufacturing method disclosed herein, first, when laser welding a laminated portion of a current collecting foil and a first conductive member serving as a current collector, a second conductive member smaller than the first conductive member is placed between the laminated portion and the first conductive member. This forms a protrusion composed of the second conductive member on the surface of the first conductive member. Next, a portion of the laminated portion is overlapped on the second conductive member. This causes the laminated portion to be in a floating state (a state in which there is a space between the laminated portion and the first conductive member) in a region of the laminated portion outside the region where it overlaps with the second conductive member. Therefore, the laminated portion in this floating state is pressed toward the first conductive member. This presses the region of the laminated portion overlapping with the second conductive member against the second conductive member, thereby reducing the gap between the current collecting foils in that region. Then, by irradiating the laminated portion in that region with a laser, the laminated portion, the second conductive member, and the first conductive member melt and are welded together. At this time, since the gaps between the current collecting foils in the laminated portion are reduced, the occurrence of spatters, blowholes, foil breakage, etc. is suppressed, and welding stability is improved. After the laser welding, it may be difficult to distinguish the boundary between the first conductive member and the second conductive member. Therefore, in this specification, it is described that after the laser welding, a current collector is produced that includes a main body derived from the first conductive member and a protrusion derived from the second conductive member.

[0027] In the preparation step S10, as shown in FIG. 3, an electrode assembly including a laminated portion in which multiple current collector foils of the first electrode are laminated, a first conductive member 46, and a second conductive member 48 smaller in size than the first conductive member 46 are prepared. For example, the electrode assembly 20 described above is prepared. The first electrode may be, for example, the positive electrode 40 described above. The following description will be given using the positive electrode 40 as an example of the first electrode. The electrode assembly 20 includes a laminated portion 52s in which multiple positive current collector foils 52 (specifically, exposed portions 52a of the positive current collector foil) are laminated. The electrode assembly 20 can be fabricated using a known method. The electrode assembly may be a laminated electrode assembly in which multiple positive electrode plates and multiple negative electrode plates are alternately laminated with separators interposed therebetween. The laminated portion may also be formed by stacking multiple tabs protruding from the ends of the current collector foils.

[0028] The first conductive member 46 corresponds to a main body portion 46A of the positive electrode current collector 44, which is produced after a welding step S40 (described later). The first conductive member 46 is a member or a part thereof that electrically connects the positive electrode terminal 42 to a laminated portion 52s, in which a plurality of positive electrode current collector foil exposed portions 52a are laminated, in the positive electrode 40. The shape of the first conductive member 46 is not particularly limited, and may be, for example, a plate-like member. The first conductive member 46 may have one or more bent portions in accordance with the arrangement of the laminated portion 52s and the positive electrode terminal 42 inside the nonaqueous electrolyte secondary battery 100. The first conductive member 46 has a first surface 46a that faces the laminated portion 52s of the positive electrode current collector foil 52. When the first conductive member 46 is plate-like, its average thickness (average thickness in a direction perpendicular to the first surface 46a (direction Y)) may be, for example, 0.5 mm to 3 mm.

[0029] The first conductive member 46 is made of a conductive material, such as a metal, such as aluminum, an aluminum alloy, copper, or a copper alloy. The first conductive member 46 may be made of, for example, the same metal as the current collector foil to which it is electrically connected, or the same metal as the electrode terminal to which it is electrically connected.

[0030] The second conductive member 48 corresponds to the protruding portion 48A of the positive electrode current collector 44, which is produced after a welding step S40, which will be described later. The second conductive member 48 has an upper surface 48a and a lower surface 48b. The lower surface 48b is a surface that contacts the first surface 46a of the first conductive member 46. The second conductive member 48 is smaller in size than the first conductive member 46. Specifically, when the second conductive member 48 is placed on the first surface 46a of the first conductive member 46, the length of the second conductive member 48 in at least one direction (e.g., direction X in FIG. 4) is shorter than the length of the first conductive member 46 in a planar view. Preferably, the entire second conductive member 48 is contained within the first surface 46a of the first conductive member 46 in a planar view.

[0031] The shape of the second conductive member 48 is not particularly limited. For example, it may be block-shaped, rod-shaped, plate-shaped, or the like. In the example shown in FIG. 3, the second conductive member 48 is plate-shaped. The average thickness of the second conductive member 48 is preferably thinner than the average thickness of the first conductive member 46. This makes the second conductive member 48 more likely to melt during laser irradiation, and facilitates stronger welding between the laminated portion 52s and the first conductive member 46. The average thickness of the second conductive member 48 may be, for example, 2.5 mm or less, 2 mm or less, 1.5 mm or less, or 1.2 mm or less. The average thickness of the second conductive member 48 may be, for example, 0.2 mm or more, 0.5 mm or more, or 1 mm or more. If the average thickness of the second conductive member 48 is too thin, the force with which the laminated portion 52s is pressed against the second conductive member 48 may be insufficient in the pressing step S30 described below. The average thickness of second conductive member 48 refers to the average thickness in the direction in which first conductive member 46 and second conductive member 48 overlap (direction Y in the drawing).

[0032] The melting point of second conductive member 48 is preferably lower than the melting point of first conductive member 46. This allows second conductive member 48 to melt before first conductive member 46 during laser welding, thereby reducing the gap between laminated portion 52s and first conductive member 46.

[0033] The hardness of second conductive member 48 is preferably lower than the hardness of first conductive member 46. The low hardness of second conductive member 48 makes it easier for laminated portion 52s to adhere to second conductive member 48, improving weldability. In this specification, "hardness" refers to Vickers hardness measured in accordance with JIS Z 2244:2009.

[0034] The second conductive member 48 may be made of any conductive material, and is not particularly limited. The second conductive member 48 may be made of, for example, metal, conductive resin, etc., but is preferably made of metal. Examples of metals include aluminum, aluminum alloys, copper, copper alloys, and solder.

[0035] When the first conductive member 46 and the second conductive member 48 are made of metal, the metal constituting the first conductive member 46 (also referred to as the "first metal") and the metal constituting the second conductive member 48 (also referred to as the "second metal") may be the same metal or different metals. In this specification, an alloy refers to a metal that is different from the metal that constitutes its main component. Also, even when alloys have the same main component, they are considered to be different metals if the elements that serve as the secondary components are different.

[0036] When the first conductive member 46 and the second conductive member 48 are made of the same metal, it is also preferable that the first conductive member 46 and the second conductive member 48 are made of the same metal as the plurality of positive current collector foils 52 that make up the laminated portion 52s. This improves welding stability. For example, it is preferable that the first conductive member 46, the second conductive member 48, and the positive current collector foils 52 are made of aluminum.

[0037] When the metal constituting first conductive member 46 and the metal constituting second conductive member 48 are different, it is preferable that one be made of an alloy and the other be made of a metal that is the main component of that alloy. For example, first conductive member 46 can be made of aluminum, and second conductive member 48 can be made of an aluminum alloy.

[0038] In the arrangement step S20, as shown in FIG. 4, the second conductive member 48 is arranged on the first surface 46a of the first conductive member 46. The first surface 46a of the first conductive member 46 and the lower surface 48b of the second conductive member 48 face each other. In this case, the second conductive member 48 is arranged so that it is located more inward than the end of the first conductive member 46 in at least one direction (for example, direction X in FIG. 4) in a plan view. Also, in the arrangement step S20, a portion of a laminated section 52s, in which multiple positive current collector foils 52 (positive current collector foil exposed portions 52a) are laminated, is arranged on the upper surface 48a of the second conductive member 48. In this case, in a portion of the second conductive member 48 outside the portion where the laminated section 52s and the second conductive member 48 are overlapped, portions where the laminated section 52s and the first surface 46a of the first conductive member 46 face each other are provided on both sides in a predetermined direction (direction X in FIG. 4). With this arrangement, as shown in FIG. 4, the region is broadly divided into a first region 210 in which the first conductive member 46, the second conductive member 48, and the laminated portion 52s are superimposed, and a second region 220 in which the laminated portion 52s and the first surface 46a of the first conductive member 46 face each other without the second conductive member 48 in between.

[0039] 4, the second region 220 is located outside the overlapping portion of the laminated portion 52s and the second conductive member 48. In the second region 220, the second conductive member 48 is not located, and therefore a gap is generated between the first conductive member 46 and the laminated portion 52s.

[0040] In the pressing step S30, the laminated portion 52s is pressed against the first surface 46a of the first conductive member 46 in the second region 220. As shown in FIG. 4, a presser plate 110 is used as a jig for performing this pressing. The presser plate 110 is disposed in the second region 220. In the second region 220, the presser plate 110 presses the surface (top layer) of the laminated portion 52s against the first surface 46a of the first conductive member 46, sandwiching the laminated portion 52s between the presser plate 110 and the first conductive member 46 (see FIG. 5). This causes the laminated portion 52s in the first region 210 to be pressed against the second conductive member 48. As a result, gaps between the positive current collector foils 52 of the laminated portion 52s in the first region 210 are reduced. A plurality of presser plates 110 may be used to press the laminated portion 52s in the second region 220. The presser plate 110 may be prepared as a single plate having a through hole, and the through hole may be aligned with the position of the first region 210 to press the laminated portion 52s in the second region 220. Note that the pressing of the laminated portion 52s in the second region 220 does not have to use the presser plate 110, and any other method may be used as long as it provides a similar effect.

[0041] Although not shown in the figure, in the second region 220, the laminated portion 52s located away from the second conductive member 48 sags toward the first conductive member 46 due to gravity. That is, as the laminated portion 52s moves away from the second conductive member 48, the gap between the laminated portion 52s and the first conductive member 46 gradually decreases. Therefore, in the second region 220, the portion where the laminated portion 52s is pressed toward the first conductive member 46 is preferably a portion where the gap between the laminated portion 52s and the first conductive member 46 is relatively large. For example, when the maximum gap distance between the laminated portion 52s and the first conductive member 46 is 100%, it is advisable to press the portion where the gap distance is 30% or more. Preferably, the portion where the gap distance is 50% or more, and more preferably the portion where the gap distance is 70% or more, is pressed. This allows the laminated portion 52s to be more closely attached to the second conductive member 48 in the first region 210, thereby further reducing the gap between the current collecting foils.

[0042] In the welding step S40, a laser L is irradiated onto the portion of the laminated portion 52s pressed against the second conductive member 48 (i.e., the portion of the first region 210). This allows the laminated portion 52s and the first conductive member 46 to be laser-welded together with the second conductive member 48 interposed therebetween. At this time, the gaps between the multiple positive electrode current collector foils 52 that make up the laminated portion 52s are reduced, which reduces the occurrence of spatter, blowholes, foil breakage, and the like, thereby improving welding stability.

[0043] The laser L may be irradiated to one location or two or more locations of the laminated portion 52s in the first region 210. The laser L may also be scanned to irradiate the laser L linearly.

[0044] The type of laser L is not particularly limited, and examples thereof include a YAG laser, a CO 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.

[0045] Using the above-described method, the laminated portion 52s and the positive electrode current collector 44 are joined by a weld 300, as shown in FIG. 6, for example. The weld 300 is a laser weld. The positive electrode current collector 44 includes a main body 46A derived from the first conductive member 46 and a protruding portion 48A derived from the second conductive member 48. That is, the main body 46A may be made of the first metal described above, and the protruding portion 48A may be made of the second metal described above. The protruding portion 48A protrudes from the surface of the main body 46A toward the laminated portion 52s. The weld 300 is provided across the laminated portion 52s, the protruding portion 48A, and the main body 46A, joining them together. In FIG. 6, the weld 300 is provided in a portion of the first region 210, but this is not limiting and the weld 300 may be provided over the entire first region 210.

[0046] In the negative electrode 60, the method for joining the laminated portion 72s, in which multiple negative electrode current collector foils 72 are laminated, and the negative electrode current collector 64 may be the same as the laser welding method described above, or may be another method. 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 using the same method 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.

[0047] 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 have to be joined after the welding process S40, and may be joined in advance before the welding process S40.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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).

[0052] Other embodiments of the laser welding method used in the welding step are described below. FIG. 7 is a schematic diagram illustrating the preparation step and placement step in a first modified example. In the example described above, the second conductive member 48 is plate-shaped, and as shown in FIG. 4, the approximately right-angled corner is disposed on the laminated portion 52s side. In the first modified example, as shown in FIG. 7, the second conductive member 148 has a chamfered corner 148c on the surface that contacts the laminated portion 52s. This prevents damage to the positive current collector foil 52 that constitutes the laminated portion 52s when the laminated portion 52s in the first region 210 is pressed against the second conductive member 148 in the pressing step. The type of chamfering of the corner 148c is not particularly limited and may be, for example, C-chamfering, R-chamfering, or light chamfering. The first modified example may be similar to the example described above except for the shape of the second conductive member.

[0053] FIG. 8 is a schematic diagram illustrating the preparation process and the arrangement process in the second modified example. In the second modified example, the second conductive member 248 has a lower surface 248b that contacts the first conductive member 46 and an upper surface 248a that faces the laminated portion 52s. The upper surface 248a is the surface that contacts the laminated portion 52s. The upper surface 248a is arched. This prevents damage to the positive current collector foil 52 that constitutes the laminated portion 52s when the laminated portion 52s in the first region 210 is pressed against the second conductive member 148 in the pressing process. The second modified example may be similar to the example described above, except for the shape of the second conductive member.

[0054] 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-described exemplary embodiments.

[0055] 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, preparing an electrode body having a laminated portion in which a plurality of current collecting foils of a first electrode are laminated, a first conductive member, and a second conductive member smaller in size than the first conductive member; disposing the second conductive member on a first surface of the first conductive member, and further disposing a portion of a laminated portion of the current collecting foil on the second conductive member; pressing a portion of the laminated portion that is located outside the portion of the laminated portion that is located on the second conductive member toward the first surface, thereby pressing the portion of the laminated portion that is located on the second conductive member against the second conductive member; and irradiating a laser beam onto a portion of the laminated portion pressed against the second conductive member, and laser welding the laminated portion and the first conductive member with the second conductive member interposed therebetween; A method for manufacturing an electricity storage device, comprising: Item 2: The manufacturing method according to item 1, wherein the second conductive member has a lower hardness than the first conductive member. Item 3: The manufacturing method according to item 1 or 2, wherein the average thickness of the second conductive member is thinner than the average thickness of the first conductive member in the direction in which the first conductive member and the second conductive member overlap. Item 4: The manufacturing method according to any one of Items 1 to 3, wherein the surface of the second conductive member that contacts the laminated portion has a corner, and the corner is chamfered. Item 5: The manufacturing method according to any one of Items 1 to 3, wherein the surface of the second conductive member that comes into contact with the laminated portion is arched. Item 6: The manufacturing method according to any one of Items 1 to 5, wherein the melting point of the second conductive member is lower than the melting point of the first conductive member. Item 7: The manufacturing method according to any one of Items 1 to 6, wherein the first conductive member and the second conductive member are made of different metals. Item 8: An electricity storage device comprising a case, an electrode body housed in the case and including a first electrode plate, and a current collector connected to the first electrode plate via a welded joint, wherein the electrode body comprises a laminated portion in which a plurality of current collecting foils of the first electrode plate are stacked, and the current collector comprises a main body portion made of a first metal and a protruding portion protruding from a surface of the main body portion and made of a second metal of a metal type different from the first metal, and wherein a part of the laminated portion and the protruding portion are joined at the welded joint. [Explanation of symbols]

[0056] 20 Electrode body 30 cases 40 positive electrode 42 Positive terminal 44 Positive electrode current collector 46 First conductive member 46A Main body 48, 148, 248 Second conductive member 48A Protrusion 50 positive electrode plate 52 Positive electrode current collector foil 52a Positive electrode current collector foil exposed part 52s laminated section 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 300 Welded Section

Claims

1. A method for manufacturing an electricity storage device, comprising: preparing an electrode body having a laminated portion in which a plurality of current collecting foils of a first electrode are laminated, a first conductive member, and a second conductive member having a size smaller than that of the first conductive member; disposing the second conductive member on a first surface of the first conductive member, and further disposing a portion of a laminated portion of the current collecting foil on the second conductive member; pressing a portion of the laminated portion that is outer than the portion disposed on the second conductive member toward the first surface, thereby pressing the portion of the laminated portion that is disposed on the second conductive member against the second conductive member; and irradiating a laser beam to a portion of the laminated portion pressed against the second conductive member, and laser welding the laminated portion and the first conductive member with the second conductive member interposed therebetween; Including, the hardness of the second conductive member is lower than the hardness of the first conductive member; A method for manufacturing an electricity storage device.

2. A method for manufacturing an electricity storage device, comprising: preparing an electrode body having a laminated portion in which a plurality of current collecting foils of a first electrode are laminated, a first conductive member, and a second conductive member having a size smaller than that of the first conductive member; disposing the second conductive member on a first surface of the first conductive member, and further disposing a portion of a laminated portion of the current collecting foil on the second conductive member; pressing a portion of the laminated portion that is outer than the portion disposed on the second conductive member toward the first surface, thereby pressing the portion of the laminated portion that is disposed on the second conductive member against the second conductive member; and irradiating a laser beam to a portion of the laminated portion pressed against the second conductive member, and laser welding the laminated portion and the first conductive member with the second conductive member interposed therebetween; Including, the melting point of the second conductive member is lower than the melting point of the first conductive member; A method for manufacturing an electricity storage device.

3. A method for manufacturing an electricity storage device, comprising: preparing an electrode body having a laminated portion in which a plurality of current collecting foils of a first electrode are laminated, a first conductive member, and a second conductive member having a size smaller than that of the first conductive member; disposing the second conductive member on a first surface of the first conductive member, and further disposing a portion of a laminated portion of the current collecting foil on the second conductive member; pressing a portion of the laminated portion that is outer than the portion disposed on the second conductive member toward the first surface, thereby pressing the portion of the laminated portion that is disposed on the second conductive member against the second conductive member; and irradiating a laser beam to a portion of the laminated portion pressed against the second conductive member, and laser welding the laminated portion and the first conductive member with the second conductive member interposed therebetween; Including, The first conductive member and the second conductive member are made of different metals. A method for manufacturing an electricity storage device.

4. The manufacturing method according to any one of claims 1 to 3, wherein the average thickness of the second conductive member is thinner than the average thickness of the first conductive member in a direction in which the first conductive member and the second conductive member overlap.

5. The manufacturing method according to any one of claims 1 to 3, wherein a surface of the second conductive member that contacts the laminated portion has a corner, and the corner is chamfered.

6. The manufacturing method according to any one of claims 1 to 3, wherein the surface of the second conductive member that comes into contact with the laminated portion is arched.

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