Method for manufacturing an electricity storage device

Abstract

To provide a technique for obtaining a power storage device with suitably improved reliability.SOLUTION: A method for manufacturing a power storage device disclosed herein includes a preparation step (S1) of preparing an electrode body, a collection step (S2) of collecting an electrode current collecting foil laminate in at least one of a positive electrode current collecting foil laminate and a negative electrode current collecting foil laminate while sequentially shifting the pressing member so as to abut against the vicinity of the bending point from the end side opposite to the side where the core part of the electrode current collecting foil laminate is located toward the core part side in the width direction, and a joining step (S3) of joining the electrode current collecting foil laminate collected in the collection step to the current collecting terminal on the corresponding pole side.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] For example, Patent Document 1 listed below discloses a terminal welding method for welding a terminal to a laminated portion of the exposed current collecting foil in an electrode body formed by stacking electrodes having a portion in which an active material is carried on the current collecting foil and a portion in which the current collecting foil is exposed and protruding from the portion in which the active material is carried.The terminal welding method describes that when welding the laminated portion and the terminal, the portion in which the active material-carrying portion of the current collecting foil is pressed and restrained, and the active material-carrying portion of the electrode is pressed from both sides in the stacking direction by a pressing means, rather than the portion to be welded of the laminated portion, to collect the current collecting foil of the laminated portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5751218 Summary of the Invention [Problem to be solved by the invention]

[0004] However, according to the inventors' investigations, it was found that with the terminal welding method described above, sliding may occur between the current collecting foil and the pressing means when collecting the current collecting foil, which may cause distortion (load) in the current collecting foil. In other words, it was found that there is still room for improvement in the terminal welding method described above from the perspective of obtaining a highly reliable electricity storage device.

[0005] The present disclosure has been made in view of the above circumstances, and a main purpose thereof is to provide a technique that can obtain an electricity storage device with suitably improved reliability. [Means for solving the problem]

[0006] To achieve this object, the present disclosure provides a method for manufacturing an electricity storage device including an electrode assembly in which a positive electrode sheet and a negative electrode sheet are stacked with a separator sheet interposed therebetween, and current collector terminals corresponding to the positive electrode sheet and the negative electrode sheet, joined to the electrode assembly. The method for manufacturing such an electricity storage device includes a preparation step of preparing the electrode assembly, wherein a core portion where a positive electrode active material layer and a negative electrode active material layer face each other is present in a central portion in a predetermined width direction of the electrode assembly, and a positive electrode current collector foil laminated portion is present at one of both end portions in the width direction, where the positive electrode active material layer-free portion where the positive electrode active material layer is not formed protrudes from the negative electrode sheet, and a negative electrode current collector foil laminated portion is present at the other end portion of the both end portions, where the negative electrode active material layer-free portion where the negative electrode active material layer is not formed protrudes from the positive electrode sheet. The method for manufacturing such an electricity storage device preferably includes a foil collecting step of collecting the electrode current collecting foil laminate in at least one of the positive electrode current collecting foil laminate and the negative electrode current collecting foil laminate while sequentially shifting a pressing member so as to abut against the vicinity of a bending point of the electrode current collecting foil laminate from the end side opposite the side where the core portion is located to the core portion side. The method for manufacturing such an electricity storage device preferably also includes a joining step of joining the electrode current collecting foil laminate collected in the foil collecting step to the current collecting terminal on the corresponding electrode side. As will be described in detail later, the method for manufacturing an electricity storage device configured in this manner can suitably reduce the load on the current collecting foil during foil collection, thereby obtaining an electricity storage device with suitably improved reliability. [Brief explanation of the drawings]

[0007] [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] 10 is a graph illustrating a method for calculating a bending point in a positive electrode current collector foil laminate according to one embodiment. [Figure 5] FIG. 4 is a schematic diagram for explaining a bending point in a positive electrode current collector foil laminated portion according to one embodiment. [Figure 6] FIG. 2 is a schematic diagram illustrating a positive electrode current collector foil laminate according to one embodiment before foil collection. [Figure 7] FIG. 2 is a schematic diagram illustrating a positive electrode current collector foil laminate according to one embodiment after foil collection. [Figure 8] FIG. 2 is a side view schematically showing a connection portion between a wound electrode body and a current collecting terminal according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] 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.

[0009] 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.

[0010] <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-shaped electrode body 20 (here, a wound electrode body), a non-aqueous electrolyte 80, and a battery case (i.e., an outer container) 30 that houses the electrode body 20 and the non-aqueous electrolyte 80.

[0011] As shown in Fig. 2, the electrode assembly 20 has a configuration in which a laminate formed by stacking a long positive electrode sheet 50 and a long negative electrode sheet 60 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 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. WL in FIG. 2 indicates the winding axis.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] Examples of the separator sheet 70 include porous sheets (films) made of resins such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. 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 the separator sheet 70. 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] <Battery manufacturing method> Next, a method for manufacturing a battery according to this embodiment will be described. Here, Fig. 3 is a flowchart showing each step of the method for manufacturing a battery according to one embodiment. First, the method for manufacturing a battery 100 according to this embodiment is a method for manufacturing a battery including an electrode assembly 20 (here, a wound electrode assembly) in which a positive electrode sheet 50 and a negative electrode sheet 60 are stacked with a separator sheet 70 interposed therebetween, and current collector terminals (here, a positive electrode current collector terminal 42a and a negative electrode current collector terminal 44a) corresponding to the positive electrode sheet 50 and the negative electrode sheet 60, respectively, joined to the electrode assembly 20. 3, the manufacturing method of the battery 100 according to this embodiment includes a preparation step (step S1) of preparing an electrode body 20, in which a core portion 20a, where the positive electrode active material layer 54 and the negative electrode active material layer 64 face each other, is present in the center of the electrode body 20 in a predetermined width direction (here, corresponding to the X direction in FIG. 2), and a positive electrode current collector foil laminated portion 52A is present at one of both ends in the width direction, in which a positive electrode active material layer-free portion 52a, where the positive electrode active material layer 54 is not formed, protrudes from the negative electrode sheet 60, and a negative electrode current collector foil laminated portion 62A is present at the other end of the both ends, in which a negative electrode active material layer-free portion 62a, where the negative electrode active material layer 64 is not formed, protrudes from the positive electrode sheet 50. The manufacturing method for the battery 100 according to this embodiment also includes a foil collecting step (step S2) of collecting the electrode current collector foil laminate in at least one of the positive current collector foil laminate 52A and the negative current collector foil laminate 62A (here, in the positive current collector foil laminate 52A and the negative current collector foil laminate 62A) while sequentially shifting the pressing member 202 in the width direction from the end side opposite to the side where the core portion 20a of the electrode current collector foil laminate is located toward the core portion 20a so that the pressing member 202 abuts against the vicinity of the bending point P. The manufacturing method for the battery 100 according to this embodiment also includes a joining step (step S3) of joining the electrode current collector foil laminate collected in the foil collecting step to the corresponding polarity-side current collecting terminal.

[0028] According to the battery manufacturing method configured as described above, in the foil collecting step, the electrode current collecting foil is collected while tracing a trajectory that passes through the bending point (i.e., the bending point) of the electrode current collecting foil, making it difficult for the electrode current collecting foil to slide (in other words, slip) against the pressing member. This effectively reduces distortion in the electrode current collecting foil, thereby effectively preventing damage (breakage) of the electrode current collecting foil. In other words, according to the battery manufacturing method disclosed herein, it is possible to obtain an electricity storage device (e.g., a battery) with improved reliability. Each step will be described in detail below.

[0029] <Preparation process: Step S1> In this step, an electrode assembly 20 having the configuration described above is prepared. Specifically, the electrode assembly 20 (here, a wound electrode assembly) is produced according to a known method. For example, a positive electrode sheet 50, a negative electrode sheet 60, and two separator sheets 70 are prepared. Using a known winding machine, the positive electrode sheet 50 and the negative electrode sheet 60 are stacked and wound with the separator sheet 70 interposed between them. The resulting wound assembly is pressed from its side to form a flat shape, producing the electrode assembly 20 shown in FIG. 2.

[0030] <Foil gathering process: Step S2> In this step, in at least one of the positive current collector foil laminate portion 52A and the negative current collector foil laminate portion 62A (here, in the positive current collector foil laminate portion 52A and the negative current collector foil laminate portion 62A), the electrode current collector foil laminate is assembled by sequentially shifting the pressing member 202 in the width direction (corresponding to the X direction in FIG. 5 ) from the end R side opposite the side where the core portion 20a of the electrode current collector foil laminate is located toward the core portion 20a (here, in the direction of the outline arrow in FIG. 5 ) so as to abut against the vicinity of the bending point P. The bending point P can be said to be the point at which each positive electrode active material layer-free portion 52a constituting the positive current collector foil laminate portion 52A buckles when the pressing member 202 is sequentially shifted and moved from the end side opposite the side where the core portion 20a of the positive current collector foil laminate portion 52A is located toward the core portion 20a.

[0031] FIG. 4 is a graph illustrating a method for calculating a bending point in a positive current collector foil laminate according to an embodiment. FIG. 5 is a schematic diagram illustrating a bending point in a positive current collector foil laminate according to an embodiment. FIG. 6 is a schematic diagram illustrating a positive current collector foil laminate according to an embodiment before foil collection. FIG. 7 is a schematic diagram illustrating a positive current collector foil laminate according to an embodiment after foil collection. Note that while FIGS. 4 to 7 focus on the positive current collector foil laminate 52A of the electrode current collector foil laminate, foil collection can also be performed using a similar method for the negative current collector foil laminate 62A. In other words, the positive current collector foil laminate and the portion without a positive active material layer in the following description can be interpreted as the negative current collector foil laminate and the portion without a negative active material layer, respectively. For clarity, the negative electrode sheet 60 and separator sheet 70 are omitted from FIGS. 5 to 7.

[0032] First, in this step, a bending point P is determined for each of the positive electrode active material layer-free portions 52a to be collected, as shown in FIG. 5. Here, distances l1 to l4 in FIG. 5 indicate the distances from the end S on the core portion 20a side of the positive electrode current collector foil laminated portion 52A in the width direction to the bending points P1 to P4, respectively. Distance s indicates the distance between the positive electrode active material layer-free portions 52a. Thickness t indicates the thickness of the positive electrode active material layer-free portions 52a. The following method can be given as an example of a method for calculating the bending point P. Specifically, first, the value of distance l1 is determined. While not particularly limited, distance l1 can be set to a value within a range of approximately 40 to 80% (e.g., within a range of 50 to 70%) when the width direction length Q of the positive electrode current collector foil laminated portion 52A (more specifically, the positive electrode active material layer-free portions 52a constituting the positive electrode current collector foil laminated portion 52A) is taken as 100%. It is preferable to change the value of the distance l1 as appropriate depending on the foil collecting conditions, etc. Next, the following formula: l2=(l1 2 +s 2 ) 1 / 2 ,l3={l1 2 +(2s+t) 2} 1 / 2 ,l4={l1 2 +(3s+2t) 2} 1 / 2Distances l2 to l4 are calculated based on the n =[l1 2 +{(n-1)s+(n―2)t} 2 ] 1 / 2 (where n is an integer of 2 or greater). In this manner, a graph such as that shown in FIG. 4 is obtained. Here, the vertical axis of the graph shown in FIG. 4 represents the number of positive current collector foils 52 (in other words, the positive-electrode active material layer-free portions 52a), and the horizontal axis represents the distance from the end S to the bending point P in the width direction X of the positive current collector foil laminated portion 52A. In addition, in this embodiment, the central positive-electrode active material layer-free portion 52a1 of the positive-electrode active material layer-free portions 52a constituting the positive current collector foil laminated portion 52A does not have a bending point, and therefore the positive-electrode active material layer-free portions 52a located above the positive-electrode active material layer-free portion 52a1 are referred to as the first, second, third, and fourth foils, respectively. The bending points P in each of the positive-electrode active material layer-free portions 52a are referred to as P1, P2, P3, and P4, respectively. The bending points P11, P12, P13, and P14 in each of the positive electrode active material layer-free portions 52a1 present below the positive electrode active material layer-free portion 52a1 can be respectively assigned to P1, P2, P3, and P4. In this manner, each bending point P in the positive electrode active material layer-free portion 52a constituting the positive electrode current collector foil laminated portion 52A can be determined. Note that the bending point in the negative electrode current collector foil laminated portion 62A can also be determined in a similar manner. However, the method for calculating the bending point P is not limited to the above-described method. The bending point P can also be determined by conducting a preliminary test or the like.

[0033] Next, as shown in FIG. 6 , the pressing member 202 is moved in a sequentially shifted manner from the end R of the positive current collector foil laminate 52A, which is on the side opposite to the side where the core 20a of the positive current collector foil laminate 52A is located, toward the core 20a, so as to abut the vicinity of the bending point P of the positive current collector foil laminate 52A determined as described above. In this manner, the positive current collector foil laminate 52A can be collected as shown in FIG. 7 . This collecting step collects the positive electrode active material layer-free portions 52a while tracing a trajectory that passes through the bending point P, thereby reducing sliding between the positive electrode active material layer-free portions 52a and the pressing member 202. This effectively reduces distortion in the positive electrode active material layer-free portions 52a, thereby effectively preventing damage to the positive electrode active material layer-free portions 52a. Note that, when the length Q in the width direction of the positive current collector foil laminated part 52A (more specifically, the positive active material layer non-forming portion 52a constituting the positive current collector foil laminated part 52A) collected in the foil collecting step is taken as 100%, the "near the bending point P" preferably means a range of 5% or less in the front-to-rear direction (i.e., the width direction) of the bending point P, more preferably 3% or less, 1% or less, and particularly preferably 0% (i.e., on the bending point P). Note that the same applies to the negative current collector foil laminated part 62A.

[0034] Next, the foil pressing movable unit 200 used in the foil collecting process according to this embodiment will be described. As shown in FIG. 6, in this embodiment, two pressing members 202 are provided in the Y direction. The pressing members 200 are controlled by a control unit (not shown). The control unit stores information regarding the bending point P calculated by the method described above. The pressing members 202 (which may also be referred to as foil pressing members) are members for collecting the positive electrode active material layer-free portions 52a constituting the positive electrode current collector foil laminated unit 52A. The pressing members 202 are connected to a linearly moving cylinder (not shown) via a spring 204. The pressing strength of the pressing members 202 can be set, for example, according to a conventional pressing strength. The pressing members 202 are provided on a guide (linear motion guide: also referred to as an LM guide) 208 that is movable in the X direction in FIG. 6. A box-shaped unit 206 provided in the guide 208 includes a cam floor 210 that is movable in the X direction. The cam floor 210 is configured to be movable along a cam groove 212. As shown in FIGS. 6 and 7 , when the pressing member 202 approaches the foil collection position, the cam floor 210 moves along the cam groove 212, and in conjunction with this, the pressing member 202 moves so as to abut against a bending point P of each positive electrode active material layer-free portion 52a that constitutes the positive electrode current collector foil laminate 52A. The pressing member 202 is moved using a cylinder. In this way, the positive electrode current collector foil laminate 52A can be collected while performing a predetermined movement. Note that the negative electrode current collector foil laminate 62A can also be collected in a similar manner.

[0035] In FIG. 5 , the shorter the width direction (here, the X direction in FIG. 5 ) length of the positive current collector foil laminate 52A (more specifically, the positive active material layer-free portion 52a constituting the positive current collector foil laminate 52A) collected in the foil collecting step, the more likely the foil is to break due to sliding between the positive current collector foil laminate 52A and the pressing member 202, making it a more suitable subject for applying the technology disclosed herein. From this perspective, although not particularly limited, the width direction length Q of the positive current collector foil laminate 52A collected in the foil collecting step is preferably 30 mm or less, more preferably 25 mm or less, and even more preferably 20 mm or less. The lower limit of the length Q is, for example, 5 mm or more, and may be 10 mm or more. The same applies to the negative current collector foil laminate 62A.

[0036] Here, the number of windings of the electrode body 20 (here, a wound electrode body) is not particularly limited as long as the effects of the technology disclosed herein can be obtained. On the other hand, for example, the greater the number of windings of the electrode body 20, the more likely the electrode current collecting foil near the outermost surface of the electrode body 20 is to break due to sliding between the electrode body 20 and the pressing member 202, and therefore it can be said that it is suitable as a target for applying the technology disclosed herein. From this perspective, although not particularly limited, the number of windings of the electrode body 20 is preferably 10 or more, more preferably 20 or more, 30 or more, or 40 or more. Furthermore, the number of layers of the electrode body 20 may be, for example, 60 or less, or 50 or less. Note that when the electrode body is a laminated electrode body, the "number of windings" in the above description should be read as the "number of layers," and each value should be read as doubled.

[0037] The positive current collector foil 52 constituting the positive current collector foil laminate 52A is generally made of a metal foil with low rigidity (in other words, soft), such as aluminum foil or aluminum alloy foil, and therefore the foil is prone to breakage. That is, the embodiment in which at least the positive current collector foil laminate 52A is collected in the foil collecting step, as in the present embodiment, can be said to be suitable as a target for applying the technology disclosed herein. <Bonding process: Step S3>

[0038] Next, the positive electrode current collector terminal 42a and the negative electrode current collector terminal 44a are attached to the electrode current collector foil laminates (here, the positive electrode current collector foil laminate 52A and the negative electrode current collector foil laminate 62A) collected in the foil collecting process by pressure welding, resistance welding, ultrasonic welding, or the like (see FIG. 8 ). For example, when ultrasonically welding the foil collecting part 26 and the current collector terminals (positive electrode current collector terminal 42a, negative electrode current collector terminal 52a), it is preferable to incorporate a horn into one of a pair of pressing jigs (not shown) and use the other pressing jig as an anvil (receiving jig). This allows the current collector terminals to be connected while the foil collecting part 26 is being press-formed. Note that in this example, 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. This connects the electrode body 20 to the lid 34 of the battery case 30. Then, the electrode body 20 is inserted into the case body 32 through the opening of the case body 32. Thereafter, the case body 32 and the lid 34 are sealed together by laser welding or the like.

[0039] 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.

[0040] 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 preferred as a power source for driving vehicles. Lithium-ion secondary battery 200 can also be used in the form of a battery pack, typically consisting of a plurality of batteries connected in series and / or parallel.

[0041] 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.

[0042] For example, in the above embodiment, the technology disclosed herein is applied to both the positive electrode current collector foil laminate 52A and the negative electrode current collector foil laminate 62A, but is not limited to this. In other embodiments, the technology disclosed herein may be applied to only one of the positive electrode current collector foil laminate and the negative electrode current collector foil laminate.

[0043] For example, in the above embodiment, the electrode body 20 is a wound electrode body, but is not limited to this. In other embodiments, the electrode body may be a laminated electrode body in which a positive electrode sheet and a negative electrode sheet are laminated with a separator sheet interposed therebetween.

[0044] For example, in the above embodiment, a rectangular battery 100 including a flat electrode body 20 has been described. However, the battery may have another shape, such as a cylindrical shape.

[0045] 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. [Explanation of symbols]

[0046] 20 Electrode body 20a Core 26 Foil Collection Department 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 80 Non-aqueous electrolyte 100 Lithium-ion secondary battery 200 Movable foil holder 202 Pressing member (foil pressing) 204 Spring 206 units 208 Guide 210 Cam Floor 212 Cam groove P bending point

Claims

1. an electrode assembly in which a positive electrode sheet and a negative electrode sheet are stacked with a separator sheet interposed therebetween; current collecting terminals connected to the electrode body and corresponding to the positive electrode sheet and the negative electrode sheet; A method for manufacturing an electricity storage device, comprising the following steps: a preparation step of preparing the electrode body, wherein a core portion where a positive electrode active material layer and a negative electrode active material layer face each other is present in a central portion in a predetermined width direction of the electrode body, and a positive electrode current collector foil laminated portion is present in one of both end portions in the width direction, in which a positive electrode active material layer-free portion where the positive electrode active material layer is not formed protrudes from the negative electrode sheet, and a negative electrode current collector foil laminated portion is present in the other end portion of the both end portions, in which a negative electrode active material layer-free portion where the negative electrode active material layer is not formed protrudes from the positive electrode sheet; a foil collecting step in which, in at least one of the positive electrode current collector foil laminate and the negative electrode current collector foil laminate, a pressing member is sequentially shifted in the width direction from an end side of the electrode current collector foil laminate opposite to a side on which the core portion is present toward the core portion so as to abut against a vicinity of a bending point in an electrode active material layer-free portion constituting the electrode current collector foil laminate, wherein, in the direction in which the electrode active material layer-free portions are stacked, the bending point is not present in a central electrode active material layer-free portion among the electrode active material layer-free portions constituting the electrode current collector foil laminate, and the electrode active material layer-free portions on one side and the other side of the center are counted as the first, second, ..., nth from the center, and the distances from the end of the core portion side of each electrode active material layer-free portion to the bending point are defined as distances l 1 , l 2 , ..., l n , respectively. the pressing member is moved so that the length in the width direction of the portion where the electrode active material layer is not formed is within a range of 50 to 70% when the length in the width direction of the portion where the electrode active material layer is not formed is taken as 100%; and a joining step of joining the electrode current collecting foil laminated portion collected in the foil collecting step to the current collecting terminal on the corresponding electrode side; A method for manufacturing an electricity storage device, comprising:

2. The method for manufacturing an electricity storage device according to claim 1, wherein in the foil collecting step, the pressing member is moved so that the distances l 2 ...l n satisfy the following formula (I): l n = [l 1 2 + {(n-1)s+(n-2)t} 2 ] 1 / 2 ... (I) (Here, in the formula, s represents the distance between the electrode active material layer non-forming portions, t represents the thickness of the electrode active material layer non-forming portions, and n is an integer of 2 or more).

3. The method for manufacturing an electricity storage device according to claim 1 , wherein the electrode current collector foil laminate collected in the foil collecting step has a length in the width direction of 30 mm or less.

4. The method for manufacturing an electricity storage device according to claim 1 , wherein at least the positive electrode current collector foil laminated portion is collected in the foil collecting step.

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