Method for manufacturing a wound electrode body, method for manufacturing an electricity storage device including the wound electrode body, and apparatus for manufacturing the wound electrode body

Abstract

To provide a technique capable of obtaining a power storage device including a wound electrode body with appropriately suppressed springback.SOLUTION: In a preferred embodiment of a manufacturing method of a wound electrode body disclosed herein, the manufacturing method includes: a preparation step (S1) of preparing a positive electrode sheet, a negative electrode sheet, and a separator sheet; a winding step (S2) of winding the positive electrode sheet and the negative electrode sheet via the separator sheet to manufacture a winding body; and a wrapping step (S3) of stretching the separator sheet existing in a winding end area of the winding body at predetermined strength and wrapping the separator sheet around the winding body. Herein, the manufacturing method further includes, after the wrapping step, a pressing step (S4) of pressing the winding body to mold the winding body into a flat shape.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a wound electrode body, a method for manufacturing an electricity storage device including the wound electrode body, and an apparatus for manufacturing the wound electrode body. [Background technology]

[0002] For example, Patent Document 1 below discloses a method for manufacturing a secondary battery equipped with a wound electrode body, which includes a step of fabricating a wound electrode body by placing a separator sheet on which a heat-resistant layer is formed between positive and negative electrode sheets and winding them. It is described that this method for manufacturing a secondary battery suppresses loosening of the wound electrode body (hereinafter also referred to as "springback"). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-137985 Summary of the Invention [Problem to be solved by the invention]

[0004] However, according to the investigations of the present inventors, it has been found that there is still room for improvement in the manufacturing method of the secondary battery as described above in terms of suppressing springback of the wound electrode body. Furthermore, it has been found that when a wound electrode body in which springback has occurred as described above is inserted into a battery case, a load is likely to be applied to the joint between the wound electrode body and the sealing plate (for example, the electrode current collector terminal located between the wound electrode body and the sealing plate). In other words, there is a need for further development of a technology that can obtain an electricity storage device including a wound electrode body in which springback is suitably suppressed.

[0005] The present disclosure has been made in consideration of the above circumstances, and its main purpose is to provide a technology that can obtain an electricity storage device including a wound electrode body in which springback is suitably suppressed. [Means for solving the problem]

[0006] To achieve this objective, the present disclosure provides a method for manufacturing a wound electrode assembly in which a positive electrode sheet and a negative electrode sheet are stacked with a separator sheet interposed therebetween and wound. This method for manufacturing a wound electrode assembly preferably includes a preparation step of preparing the positive electrode sheet, the negative electrode sheet, and the separator sheet. This method for manufacturing a wound electrode assembly preferably also includes a winding step of winding the positive electrode sheet and the negative electrode sheet with the separator sheet interposed therebetween to produce a wound assembly. This method for manufacturing a wound electrode assembly preferably also includes a winding step of stretching the separator sheet present in the winding end region of the wound assembly with a predetermined strength and winding it around the wound assembly. As will be described in detail below, this method for manufacturing a wound electrode assembly with this configuration can produce a wound electrode assembly in which springback is suitably suppressed. Therefore, a power storage device can be obtained that includes a wound electrode assembly in which springback is suitably suppressed.

[0007] From another aspect, the present disclosure provides a method for manufacturing an electricity storage device, in which an electricity storage device is constructed using a wound electrode body obtained by any of the methods for manufacturing a wound electrode body disclosed herein. By using this method for manufacturing an electricity storage device, it is possible to obtain an electricity storage device including a wound electrode body in which springback is suitably suppressed.

[0008] From another aspect, the present disclosure provides a manufacturing apparatus for a wound electrode body in which a positive electrode sheet and a negative electrode sheet are stacked and wound with a separator sheet interposed therebetween. The manufacturing apparatus for a wound electrode body preferably includes a winding core that winds the positive electrode sheet and the negative electrode sheet with the separator sheet interposed therebetween to produce a wound body. The manufacturing apparatus for a wound electrode body preferably also includes a holding member that holds the wound body so that tension is not applied to sheets other than the separator sheet present in the winding end region of the wound body. The manufacturing apparatus for a wound electrode body preferably also includes a stretching member that stretches the separator sheet present in the winding end region of the wound body with a predetermined strength. As will be described in detail later, a manufacturing apparatus for a wound electrode body with such a configuration can produce a wound electrode body in which springback is suitably suppressed. Therefore, an electricity storage device can be obtained that includes a wound electrode body in which springback is suitably suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a front view schematically illustrating the internal structure of a battery according to an embodiment. [Figure 2] FIG. 1 is a perspective view schematically showing a wound electrode body according to one embodiment. [Figure 3] 1 is a flowchart showing each step of a battery manufacturing method according to one embodiment. [Figure 4] 1 is a schematic diagram showing the configuration of a wound electrode body manufacturing apparatus according to one embodiment. FIG. [Figure 5] 1A to 1C are schematic diagrams for explaining the production of a wound body according to an embodiment. [Figure 6] 5A and 5B are schematic diagrams for explaining adjustment of the position of a separator sheet according to one embodiment. [Figure 7] 5A and 5B are schematic diagrams for explaining adjustment of the position of a separator sheet according to one embodiment. [Figure 8] 5A and 5B are schematic diagrams for explaining cutting of a separator sheet according to one embodiment. [Figure 9]10A and 10B are schematic diagrams for explaining the stretching of a separator sheet present in the winding end region of a winding body according to an embodiment. [Figure 10] 10 is a schematic diagram for explaining winding while stretching a separator sheet present in the winding end region of a winding body according to one embodiment. FIG. [Figure 11] 3A and 3B are schematic diagrams for explaining application of tape to a roll according to one embodiment. [Figure 12] FIG. 2 is a schematic diagram illustrating a configuration of a winding body according to an embodiment. [Figure 13] FIG. 2 is a schematic diagram illustrating a state of a wound body before pressing according to an embodiment. [Figure 14] FIG. 2 is a schematic diagram illustrating a state of a rolled body after pressing according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Several embodiments of the technology disclosed herein will be described below with reference to the drawings. In the following drawings, components and parts that perform the same function are denoted by the same reference numerals. Furthermore, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relationships. Matters other than those specifically mentioned in this specification that are necessary for implementing the technology disclosed herein (e.g., the general configuration and manufacturing process of an energy storage device that does not characterize this disclosure) can be understood as design matters by those skilled in the art based on conventional technology in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field. Furthermore, the following description is not intended to limit the present disclosure to the following embodiments. The battery manufacturing method disclosed herein may include additional steps at any stage, and steps that are not described as essential may be omitted as appropriate. Furthermore, the order of steps may be changed as long as the effects of the technology disclosed herein are achieved.

[0011] In this specification, the notation "A to B" indicating a range means "greater than A and less than B." It also encompasses the meanings of "greater than A" and "less than B." In addition, in this specification, the term "electricity storage device" refers to a device that can charge and discharge. Electricity storage devices include batteries such as primary batteries and secondary batteries (for example, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries, and nickel-metal hydride batteries), and capacitors (physical batteries) such as electric double layer capacitors. The electrolyte may be any of a liquid electrolyte (electrolytic solution), a gel electrolyte, and a solid electrolyte. Hereinafter, a lithium ion secondary battery (hereinafter simply referred to as "battery 100"), which is one embodiment of the electricity storage device disclosed herein, will be described as an example.

[0012] <Overall battery configuration> First, a brief description will be given of the configuration of a battery 100 obtained by the manufacturing method of a battery according to this embodiment. Here, Fig. 1 is a front view schematically showing the internal structure of a battery according to one embodiment. Fig. 2 is a perspective view schematically showing a wound electrode body according to one embodiment. As shown in Fig. 1, the battery 100 includes a flat wound electrode body 20, a non-aqueous electrolyte 80, and a battery case (i.e., an outer container) 30 that houses the wound electrode body 20 and the non-aqueous electrolyte 80.

[0013] As shown in Fig. 2, the wound electrode body 20 has a configuration in which a laminate, in which a long positive electrode sheet 50 and a long negative electrode sheet 60 are stacked with two long separator sheets 70 interposed therebetween, is wound in the longitudinal direction. The positive electrode sheet 50 has a configuration in which a positive electrode active material layer 54 is formed along the longitudinal direction on one or both sides (both sides in this case) of a long positive electrode current collector foil 52. The negative electrode sheet 60 has a configuration in which a negative electrode active material layer 64 is formed along the longitudinal direction on one or both sides (both sides in this case) of a long negative electrode current collector foil 62. The positive electrode active material layer-free portions 52a (i.e., portions where the positive electrode active material layer 54 is not formed and the positive electrode current collector foil 52 is exposed) and the negative electrode active material layer-free portions 62a (i.e., portions where the negative electrode active material layer 64 is not formed and the negative electrode current collector foil 62 is exposed) are formed so as to protrude outward from both ends of the wound electrode body 20 in the winding axis direction (i.e., the width direction perpendicular to the longitudinal direction). A core portion 20a, where the positive electrode active material layer 54 and the negative electrode active material layer 64 face each other, is located in the center in the winding axis direction. A positive electrode current collector terminal 42a and a negative electrode current collector terminal 44a are joined to the positive electrode current collector foil laminated portion 52A, which is made up of a plurality of stacked positive electrode active material layer-free portions 52a, and the negative electrode current collector foil laminated portion 62A, which is made up of a plurality of stacked negative electrode active material layer-free portions 62a, respectively. Note that WL in FIG. 2 indicates the winding axis.

[0014] The positive electrode current collector foil 52 constituting the positive electrode sheet 50 may be a known positive electrode current collector foil used in lithium ion secondary batteries, examples of which include aluminum foil, aluminum alloy foil, etc. The thickness of the positive electrode current collector foil 52 is not particularly limited and is, for example, 3 μm to 35 μm, and preferably 5 μm to 20 μm.

[0015] The positive electrode active material layer 54 contains a positive electrode active material. The positive electrode active material may be a known positive electrode active material used in lithium-ion secondary batteries. Specifically, for example, a lithium composite oxide, a lithium transition metal phosphate compound, or the like may be used as the positive electrode active material. The crystal structure of the positive electrode active material is not particularly limited and may be a layered structure, a spinel structure, an olivine structure, or the like. Examples of lithium composite oxides include lithium nickel composite oxides, lithium cobalt composite oxides, lithium manganese composite oxides, lithium nickel manganese composite oxides, lithium nickel cobalt manganese composite oxides, lithium nickel cobalt aluminum composite oxides, and lithium iron nickel manganese composite oxides. These positive electrode active materials may be used alone or in combination of two or more. A preferred positive electrode active material is a lithium nickel cobalt manganese composite oxide.

[0016] The average particle diameter (median diameter: D50) of the positive electrode active material is not particularly limited, but is, for example, 0.05 μm to 25 μm, preferably 1 μm to 20 μm, and more preferably 3 μm to 15 μm. The average particle diameter (D50) of the positive electrode active material can be determined, for example, by a laser diffraction scattering method.

[0017] The content of the positive electrode active material in the positive electrode active material layer 54 (i.e., the content of the positive electrode active material relative to the total mass of the positive electrode active material layer 54) is not particularly limited, but is, for example, 80 mass % or more, preferably 85 mass % or more, and more preferably 90 mass % or more.

[0018] The positive electrode active material layer 54 may contain components other than the positive electrode active material (i.e., optional components). Examples of the optional components include a conductive material, a binder, etc. Suitable conductive materials include carbon materials such as carbon black (e.g., acetylene black), carbon nanotubes (CNTs), and graphite. Suitable binders include polyvinylidene fluoride (PVDF), etc. When CNTs are used as the conductive material, the positive electrode active material layer 54 may further contain a dispersant for the CNTs.

[0019] The content of the conductive material in the positive electrode active material layer 54 is not particularly limited, but is preferably 0.1% by mass to 15% by mass, and more preferably 0.5% by mass to 13% by mass. The content of the binder in the positive electrode active material layer 54 is not particularly limited, but is preferably 1% by mass to 15% by mass, and more preferably 1.5% by mass to 10% by mass. The thickness of the positive electrode active material layer 54 is not particularly limited, but is, for example, 10 μm to 300 μm, and preferably 20 μm to 200 μm. The positive electrode sheet 50 may contain an insulating layer (not shown) at the boundary between the positive electrode active material layer non-forming portion 52a and the positive electrode active material layer 54. The insulating layer may contain, for example, ceramic particles.

[0020] A known negative electrode current collector foil used in lithium ion secondary batteries, such as copper foil, may be used as the negative electrode current collector foil 62 that constitutes the negative electrode sheet 60. The thickness of the negative electrode current collector foil 62 is not particularly limited and is, for example, 3 μm to 35 μm, and preferably 5 μm to 20 μm.

[0021] The negative electrode active material layer 64 contains a negative electrode active material. As the negative electrode active material, for example, a carbon material such as graphite, hard carbon, or soft carbon can be used. The graphite may be natural graphite or artificial graphite, or may be amorphous carbon-coated graphite in which graphite is coated with an amorphous carbon material.

[0022] The average particle diameter (median diameter: D50) of the negative electrode active material is not particularly limited, but is, for example, 0.1 μm to 50 μm, preferably 1 μm to 25 μm, and more preferably 5 μm to 20 μm. The average particle diameter (D50) of the negative electrode active material can be determined, for example, by a laser diffraction scattering method.

[0023] The negative electrode active material layer 64 may contain components other than the active material, such as a binder or a thickener. Examples of binders that can be used include styrene butadiene rubber (SBR) and polyvinylidene fluoride (PVDF). Examples of thickeners that can be used include carboxymethyl cellulose (CMC). The content of the negative electrode active material in the negative electrode active material layer 64 is preferably 90% by mass or more, more preferably 95% to 99% by mass. The content of the binder in the negative electrode active material layer 64 is preferably 0.1% to 8% by mass, more preferably 0.5% to 3% by mass. The content of the thickener in the negative electrode active material layer 64 is preferably 0.3% to 3% by mass, more preferably 0.5% to 2% by mass. The thickness of the negative electrode active material layer 64 is not particularly limited, but is, for example, 10 μm to 300 μm, and preferably 20 μm to 200 μm.

[0024] Examples of separator sheet 70 include porous sheets (films) made of resins such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Among these, separator sheet 70 is preferably made of a polyolefin resin such as PE or PP, from the viewpoint of suitability for stretching by stretching member 216, as described below. Furthermore, such porous sheets may have a single-layer structure or a laminated 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). A heat-resistant layer (HRL) may be provided on the surface of separator sheet 70.

[0025] The thickness of the separator sheet 70 is not particularly limited, but is, for example, 5 μm to 50 μm, and preferably 10 μm to 30 μm. In this embodiment, the wound electrode body 20 includes two separator sheets 70. The air permeability of the separator sheet 70 is, for example, 30 sec / 100 cc to 500 sec / 100 cc, and may be 30 sec / 100 cc to 300 sec / 100 cc or 50 sec / 100 cc to 200 sec / 100 cc. In this embodiment, the two separators have the same configuration, but in other embodiments, they may have different configurations. In other embodiments, the separator sheet 70 may be a single sheet. As in this embodiment, the separator sheet 70 is preferably longer than the positive electrode sheet 50 and the negative electrode sheet 60 so that the separator sheet 70 is present in the winding end region of the wound electrode body 20A (see separator sheet 70A in FIG. 2).

[0026] Although not particularly limited, the tensile strength of separator sheet 70 is, for example, 0.1 MPa or more, and from the viewpoint of being suitable for use by stretching using stretching member 216 described below, is preferably 0.5 MPa or more, and more preferably 1 MPa or more. The upper limit of the tensile strength of separator sheet 70 is, for example, 10 MPa or less, and may be 7 MPa or less. Such tensile strength can be measured, for example, based on JIS K7161.

[0027] The number of windings (number of turns) of the wound electrode body 20 (or the wound body 20A described later) is not particularly limited, but may be, for example, 10 or more, 20 or more, 30 or more, or 40 or more. The upper limit of the number of windings is, for example, 60 or less, or may be 50 or less.

[0028] The nonaqueous electrolyte 80 typically contains a nonaqueous solvent and a supporting salt (electrolyte salt). As the nonaqueous solvent, various organic solvents such as carbonates, ethers, esters, nitriles, sulfones, and lactones commonly used in electrolyte solutions for lithium-ion secondary batteries can be used without any particular limitation. Of these, carbonates and esters are preferred, and specific examples thereof include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl acetate, and methyl propionate. One of these nonaqueous solvents can be used alone, or two or more can be used in appropriate combination.

[0029] As the supporting salt, for example, lithium salts such as LiPF6, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI) (preferably LiPF6) can be suitably used. The concentration of the supporting salt is preferably 0.7 mol / L to 1.3 mol / L.

[0030] The nonaqueous electrolyte 80 may contain various additives other than the above-mentioned components, such as film-forming agents such as vinylene carbonate (VC) and oxalate complexes; gas generating agents such as biphenyl (BP) and cyclohexylbenzene (CHB); and thickeners, as long as the effects of the present disclosure are not significantly impaired.

[0031] The battery case 30 includes a case body 32 and a lid 34. The battery case 30 is made of, for example, a metal (e.g., aluminum, stainless steel, nickel-plated steel, etc.). The battery case 30 is preferably made of aluminum because it has good electrical conductivity, thermal conductivity, strength, and light weight. The case body 32 has a flattened rectangular parallelepiped shape, one of whose faces (the top face in the figure) is an opening. The lid 34 has a generally rectangular shape that fits the shape of the opening. The lid 34 is provided with a positive electrode terminal 42 and a negative electrode terminal 44 for external connection, as well as a thin-walled safety valve 36 that is configured to release internal pressure when the internal pressure of the battery case 30 rises above a predetermined level. The lid also has a liquid injection hole (not shown) for injecting a nonaqueous electrolyte 80. The positive electrode terminal 42 is electrically connected to a positive electrode current collector terminal 42a. The negative electrode terminal 44 is electrically connected to a negative electrode current collector terminal 44a. The positive electrode terminal 42 and the positive electrode current collector terminal 42a are made of, for example, aluminum, an aluminum alloy, etc. The negative electrode terminal 44 and the negative electrode current collector terminal 44a are made of, for example, copper, a copper alloy, etc.

[0032] <Wound electrode body manufacturing equipment> Next, a manufacturing apparatus for a wound electrode body according to the present embodiment will be described. Here, FIG. 4 is a schematic diagram showing the configuration of a wound electrode body manufacturing apparatus according to one embodiment. FIG. 5 is a schematic diagram for explaining the production of a wound body according to one embodiment. FIGS. 6 and 7 are schematic diagrams for explaining the adjustment of the position of a separator sheet according to one embodiment. FIG. 8 is a schematic diagram for explaining the cutting of a separator sheet according to one embodiment. FIG. 9 is a schematic diagram for explaining the stretching of a separator sheet present in the winding end region of a wound body according to one embodiment. FIG. 10 is a schematic diagram for explaining winding while stretching a separator sheet present in the winding end region of a wound body according to one embodiment. FIG. 11 is a schematic diagram for explaining the application of tape to a wound body according to one embodiment. FIG. 12 is a schematic diagram showing the configuration of a wound body according to one embodiment. Note that, for ease of explanation, only the first winding core 204 is shown in FIGS. 9 to 11.

[0033] Here, the "winding end region" may be, for example, a region from the outermost periphery (corresponding to the region P1-P2 in FIG. 12 ) to within five peripheries, four peripheries, three peripheries, two peripheries, or one periphery, among the turns (turns) of the sheet constituting the wound body. Alternatively, the "winding end region" may be only the outermost periphery among the turns (turns) of the sheet constituting the wound body, or may be a region within one-half of the outermost periphery. For example, in this embodiment, the winding end region is only the outermost periphery (i.e., the region P1-P2 in FIG. 12 ), and the separator sheet 70A present at the outermost periphery is stretched in the winding process described below. Furthermore, from the viewpoint of facilitating stretching of the separator sheet 70 in the winding process described below, it is preferable that the winding end region of the wound body 20A does not include the positive electrode sheet 50 and the negative electrode sheet 60, and is composed of only two separator sheets 70, as in this embodiment. However, the technology disclosed here is not limited to the above description.

[0034] First, the wound electrode body manufacturing apparatus 200 according to this embodiment is a manufacturing apparatus for manufacturing a wound electrode body 20 in which a positive electrode sheet 50 and a negative electrode sheet 60 are stacked with a separator sheet 70 interposed therebetween and wound. The wound electrode body manufacturing apparatus 200 includes a winding core (here, a first winding core 204) for winding the positive electrode sheet 50 and the negative electrode sheet 60 with the separator sheet 70 interposed therebetween to produce a wound body 20A. The wound electrode body manufacturing apparatus 200 also includes a holding member 214 for holding the wound body 20A so that tension is not applied to sheets other than the separator sheet 70A present in the winding end region of the wound body 20A (here, the positive electrode sheet 50, the negative electrode sheet 60, and the separator sheet 70 present on the inner circumferential side of the separator sheet 70A present in the winding end region of the wound body 20A). The wound electrode body manufacturing apparatus 200 is provided with a stretching member 216 that stretches the separator sheet 70A present at the winding end region of the wound body 20A with a predetermined strength.

[0035] As described above, the wound electrode body manufacturing apparatus 200 includes a holding member 214 that holds the wound body 20A so that tension is not applied to sheets other than the separator sheet 70A present in the winding end region of the wound body 20A, and a stretching member 216 that stretches the separator sheet 70 present in the winding end region of the wound body 20A with a predetermined strength. This allows the separator sheet 70A present in the winding end region of the wound body 20A to be selectively stretched, and the wound body 20A can be fastened by the stretched separator sheet 70A. This fastening allows a load to be continuously applied to the wound body 20A (wound electrode body 20), thereby suitably suppressing springback of the wound electrode body 20. Below, each component of the wound electrode body manufacturing apparatus 200 according to this embodiment will be described.

[0036] The first winding core 204 shown in FIG. 4 is a member that winds up the positive electrode sheet 50 and the negative electrode sheet 60 with the separator sheet 70 interposed therebetween. The first winding core 204 has the function of holding each sheet that is wound around its circumferential surface. As shown in FIG. 4, in this embodiment, in addition to the first winding core 204, a second winding core 206 and a third winding core 208 are also provided. Here, the third winding core 208 is a member that operates when adjusting the position of the separator sheet 70, which will be described later. The first winding core 204, the second winding core 206, and the third winding core 208 are located within the index 202. Note that the first winding core 204, the second winding core 206, and the third winding core 208 are two semicircular members and have a two-part structure here, but these winding cores may have a cylindrical shape, or a flat winding core may be used when winding into a flat shape.

[0037] 7 is a roller that adjusts the position of the separator sheet 70 to an appropriate position when cutting the separator sheet 70, which will be described later. Also, a cutter 212 shown in FIG. 8 is a cutter that cuts the separator sheet 70 to a desired length.

[0038] The holding member 214 shown in FIG. 9 is a member that holds the wound body 20A so as not to apply tension to sheets (here, the positive electrode sheet 50, the negative electrode sheet 60, and the separator sheet 70) other than the separator sheet 70A present in the winding end region of the wound body 20A (here, the region P1 to P2 in FIG. 12). The holding member 214 can selectively stretch the separator sheet 70A present in the winding end region of the wound body 20A. Note that at this time, additional tightening of the positive electrode sheet 50, the negative electrode sheet 60, and the separator sheet 70 present on the inner periphery side of the separator sheet 70A present in the winding end region of the wound body 20A is suppressed. In this embodiment, the shape of the holding member 214 is cylindrical, but is not limited to this, and in other embodiments, various other shapes such as rectangular or elliptical may be used.

[0039] The stretching member 216 stretches the separator sheet 70A at the outermost periphery of the winding body 20A with a predetermined strength. As shown in FIG. 9 , the stretching member 216 includes a chuck 216A (e.g., an electrostatic chuck) for holding the separator sheet 70 and a spring 216B for stretching the separator sheet 70. The spring 216B is connected to, for example, a cylinder (not shown). The strength of the stretching member 216 for stretching the separator sheet 70A at the winding end region of the winding body 20A (hereinafter simply referred to as "stretching strength") is, for example, 20 N or more, 30 N or more, and is preferably 40 N or more, more preferably 50 N or more, and even more preferably 60 N or more, from the viewpoint of suitably binding the winding body 20A with the stretched separator sheet 70A. The stretching strength is, for example, 100N or less, and from the viewpoint of suitably preventing breakage of the separator sheet 70A, is preferably 90N or less, more preferably 80N or less, and even more preferably 70N or less.

[0040] 11 is a member that applies a stop tape to the winding end of the separator sheet 70 of the winding body 20A. As the tape, any stop tape used for this type of winding body can be used without any particular restrictions.

[0041] It is preferable that each component of the wound electrode manufacturing apparatus 200 has a required actuator as appropriate. The control device is configured to control each component of the wound electrode manufacturing apparatus 200 so that required operations are performed at predetermined timings in accordance with a preset program. The control device can be embodied by a computer such as a microcontroller, for example.

[0042] <Method of manufacturing a wound electrode body> Next, a method for manufacturing a wound electrode body according to this embodiment will be described with reference to a wound electrode body manufacturing apparatus 200 that embodies the method for manufacturing a wound electrode body. Here, FIG. 3 is a flowchart showing each step of a method for manufacturing a battery according to one embodiment. First, the method for manufacturing a wound electrode body according to this embodiment is a method for manufacturing a wound electrode body 20 in which a positive electrode sheet 50 and a negative electrode sheet 60 are stacked with a separator sheet 70 interposed therebetween and wound. This method for manufacturing a wound electrode body includes a preparation step (step S1) of preparing the positive electrode sheet 50, the negative electrode sheet 60, and the separator sheet 70. This method for manufacturing a wound electrode body also includes a winding step (step S2) of winding the positive electrode sheet 50 and the negative electrode sheet 60 with the separator sheet 70 interposed therebetween to produce a wound body 20A. This method for manufacturing a wound electrode body also includes The method includes a winding step (step S3) in which separator sheet 70A present in the winding end region of winding body 20A is stretched with a predetermined strength and wound around winding body 20A. In this embodiment, after the winding step, a pressing step (step S4) is further included in which winding body 20A is pressed to form a flat shape.

[0043] As described above, in the method for manufacturing the wound electrode body, in the winding step (step S2), the separator sheet 70A present at the winding end region of the wound body 20A is stretched with a predetermined strength and wound around the wound body 20A. This allows the wound body 20A to be fastened by the stretched separator sheet 70A. This fastening allows a load to be continuously applied to the wound body 20A (wound electrode body 20), thereby suitably suppressing springback of the wound electrode body 20. Each step is described below.

[0044] (Preparation process: Step S1) In this step, a positive electrode sheet 50, a negative electrode sheet 60, and a separator sheet 70 are prepared. In this embodiment, two separator sheets 70 are prepared. As in this embodiment, it is preferable to prepare a separator sheet 70 that is longer than the positive electrode sheet 50 and the negative electrode sheet 60 so that the separator sheet 70 is present in the winding end region of the wound body 20A.

[0045] (Winding process: step S2) In this process, the positive electrode sheet 50 and the negative electrode sheet 60 are wound with the separator sheet 70 interposed therebetween to produce the wound body 20A. In this embodiment, the wound body 20A is produced so that only the separator sheet 70 is present in the winding end region. Specifically, as shown in FIG. 5 , the positive electrode sheet 50, the negative electrode sheet 60, and the separator sheet 70 are first wound around the first winding core 204. At this time, the third winding core 208 is moved to the rear so as not to interfere with the position adjustment of the separator sheet 70. Next, as shown in FIG. 6 , the index 202 is rotated 120° in the direction of arrow S. Next, as shown in FIG. 7 , the third winding core 208 is rotated by an angle sufficient to sandwich the separator sheet 70. The position of the separator sheet 70 is adjusted by the adjustment roller 210 so that the third winding core 208 can sandwich the separator sheet 70. Then, the third winding core 208 is advanced onto the surface of the index 202. Next, as shown in Fig. 8, the separator sheet 70 is cut to the desired length by the cutter 212. At this time, it is preferable that the separator sheet 70 on both sides of the cutter 212 is held down by the chucks 216A.

[0046] (Winding process: step S3) In this step, the separator sheet 70A in the winding end region of the winding body 20A is stretched to a predetermined tension and then wound around the winding body 20A. Specifically, as shown in Fig. 9, first, the winding body 20A is held by a holding member 214 so that no tension is applied to sheets other than the separator sheet 70A in the winding end region of the winding body 20A (here, the positive electrode sheet 50, negative electrode sheet 60, and separator sheet 70 in regions other than the winding end region of the winding body 20A). At this time, additional tightening of the positive electrode sheet 50, negative electrode sheet 60, and separator sheet 70 located on the inner periphery side of the separator sheet 70A in the winding end region of the winding body 20A is suppressed. 9 and 10, the separator sheet 70A present in the winding end region of the winding body 20A is stretched by the stretching member 216 in the direction of the arrow T with a predetermined strength, and then wound around the winding body 20A. At this time, by synchronizing the speed of the first winding core 204 in the direction of the arrow V with the speed of the stretching member 216 in the direction of the arrow U, the separator sheet 70A can be wound around the winding body 20A in a stretched state. Alternatively, even without such feedback control, slight differences in diameter can be absorbed by the length of the spring 216B. Note that the stretching strength described in the section <Wound electrode assembly manufacturing apparatus> can be referenced for the stretching strength of the separator sheet 70A present in the winding end region of the winding body 20A.

[0047] 11, the holding member 214 is retracted in the direction of the arrow W. Then, a tape application member is used to apply a take-up tape to the take-up end of the wound body 20A fabricated as described above.

[0048] (Pressing process: Step S4) In this embodiment, the winding step is followed by a pressing step of pressing the wound electrode body 20A to form a flat shape. FIG. 13 is a schematic diagram showing the wound electrode body according to one embodiment before pressing. FIG. 14 is a schematic diagram showing the wound electrode body according to one embodiment after pressing. This pressing step can be performed by pressing the wound electrode body 20A produced as described above in the direction of the outline arrow using a press 300. While not particularly limited, the pressing pressure can be, for example, 20 N to 200 kN (preferably, 50 N to 120 kN). This pressing may be a heated press or a non-heated press. By performing this pressing step, springback of the wound electrode body 20 can be more effectively suppressed. The wound electrode body 20 can be produced in the manner described above.

[0049] <Battery manufacturing method> Next, the positive electrode current collector terminal 42a and the negative electrode current collector terminal 44a are attached to the positive electrode current collector foil laminated portion 52A and the negative electrode current collector foil laminated portion 62A of the wound electrode body 20 fabricated as described above by resistance welding, ultrasonic welding, or the like. Here, it is assumed that the positive electrode terminal 42, the negative electrode terminal 44, the positive electrode current collector terminal 42a, and the negative electrode current collector terminal 44a are attached to the lid 34 of the battery case 30. In this way, the wound electrode body 20 is connected to the lid 34 of the battery case 30. Then, the wound electrode body 20 is inserted into the case body 32 through the opening of the case body 32. The case body 32 and the lid 34 are then sealed by laser welding or the like.

[0050] Next, the non-aqueous electrolyte 80 is prepared according to a known method. The non-aqueous electrolyte 80 is poured into the battery case 30 through the pouring hole in the lid 34 of the battery case 30, and the pouring hole is sealed. In this manner, the battery 100 can be obtained.

[0051] Battery 100 can be used for a variety of purposes. Specific applications include portable power sources for personal computers, portable electronic devices, portable terminals, etc.; power sources for driving vehicles such as electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); and storage batteries for small-sized power storage devices, with battery 100 being particularly preferred as a power source for driving vehicles. Battery 100 can also be used in the form of a battery pack, typically consisting of a plurality of batteries connected in series and / or parallel.

[0052] Although one embodiment of the present disclosure has been described above, the above embodiment is merely an example. The present disclosure can be implemented in various other forms. The present disclosure can be implemented based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. The technology described in the claims includes various modifications and alterations of the above-exemplified embodiment. For example, it is possible to replace part of the above-described embodiment with other modified embodiments, and it is also possible to add other modified embodiments to the above-described embodiment. Furthermore, if a technical feature is not described as essential, it can be deleted as appropriate.

[0053] For example, in the above embodiment, the shape of the wound electrode body 20 is flat, but is not limited to this. In other embodiments, the shape of the wound electrode body may be cylindrical or the like.

[0054] For example, in the above embodiment, the method for manufacturing the wound electrode body includes the pressing step (step S4), but is not limited to this. For example, if the wound electrode body is cylindrical, the pressing step can be omitted.

[0055] Although the embodiments of the present disclosure have been described above, the above embodiments are merely examples. The present disclosure can be implemented in various other forms. The present disclosure can be implemented based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. The technology described in the claims includes various modifications and alterations of the above-exemplified embodiments.

[0056] As described above, specific aspects of the technology disclosed herein include those described in the following items. Item 1: A method for manufacturing a wound electrode body in which a positive electrode sheet and a negative electrode sheet are stacked with a separator sheet interposed therebetween and wound, the method comprising the following steps: a preparation step of preparing the positive electrode sheet, the negative electrode sheet, and the separator sheet; a winding step of winding the positive electrode sheet and the negative electrode sheet with the separator sheet interposed therebetween to produce a wound body; and a winding step of stretching the separator sheet present in the winding end region of the wound body with a predetermined strength and winding it around the wound body. Item 2: The method for manufacturing a wound electrode body according to Item 1, wherein the predetermined strength is 40 N or more. Item 3: A method for producing a wound electrode body according to Item 1 or 2, further comprising a pressing step of pressing the wound body to form it into a flat shape after the winding step. Item 4: A method for producing an electricity storage device, comprising constructing an electricity storage device using a wound electrode body obtained by the method for producing a wound electrode body according to any one of items 1 to 3. Item 5: A manufacturing apparatus for a wound electrode body in which a positive electrode sheet and a negative electrode sheet are stacked with a separator sheet interposed therebetween and wound, the manufacturing apparatus for a wound electrode body comprising: a winding core that winds the positive electrode sheet and the negative electrode sheet with the separator sheet interposed therebetween to produce a wound body; a holding member that holds the wound body so that no tension is applied to sheets other than the separator sheet present in the winding end region of the wound body; and a stretching member that stretches the separator sheet present in the winding end region of the wound body with a predetermined strength. Item 6: The manufacturing device for a wound electrode body according to Item 5, wherein the predetermined strength is 40 N or more. [Explanation of symbols]

[0057] 20 Wound electrode body 20a Core 30 Battery case 32 Case body 34 Lid 36 Safety valve 42 Positive terminal 42a Positive current collecting terminal 44 Negative terminal 44a Negative electrode current collecting terminal 50 Positive electrode sheet (positive electrode) 52 Positive electrode current collector foil 52a Portion where positive electrode active material layer is not formed 52A Positive current collector foil laminate 54 Cathode active material layer 60 negative electrode sheet (positive electrode) 62 Negative electrode current collecting foil 62a Part where negative electrode active material layer is not formed 62A negative electrode current collector foil laminate 64 Negative electrode active material layer 70 Separator sheet (separator) 80 Non-aqueous electrolyte 100 batteries 200 Wound electrode manufacturing equipment 202 Index 204 First winding core 206 Second winding core 208 Third winding core 210 Adjustment roller 212 Cutter 214 Retaining member 216 Extension member 218 Tape-attached parts 300 press machine

Claims

1. A method for producing a wound electrode body in which a positive electrode sheet and a negative electrode sheet are stacked with a separator sheet interposed therebetween and wound, the method comprising the following steps: a preparation step of preparing the positive electrode sheet, the negative electrode sheet, and the separator sheet; a winding step of winding the positive electrode sheet and the negative electrode sheet with the separator sheet interposed therebetween to prepare a wound body; and a winding step of stretching the separator sheet present in the winding end region of the winding body with a force of 40 N or more and winding the separator sheet around the winding body; A method for manufacturing a wound electrode body, comprising:

2. The method for manufacturing a wound electrode body according to claim 1 , further comprising a pressing step of pressing the wound body to form it into a flat shape after the winding step.

3. A method for manufacturing an electricity storage device, comprising constructing an electricity storage device using a wound electrode body obtained by the method for manufacturing a wound electrode body according to claim 1 or 2.

4. A manufacturing apparatus for a wound electrode body in which a positive electrode sheet and a negative electrode sheet are stacked with a separator sheet interposed therebetween and wound, a winding core for winding the positive electrode sheet and the negative electrode sheet with the separator sheet interposed therebetween to produce a wound body; a holding member that holds the winding body so that no tension is applied to sheets other than the separator sheet present in the winding end region of the winding body; a stretching member that stretches the separator sheet present in the winding end region of the winding body at a force of 40 N or more; A manufacturing apparatus for a wound electrode body, comprising:

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