Electrode body for power storage device, power storage device, and method for manufacturing electrode body for power storage device

Abstract

An electrode body (14) for a power storage device comprises a positive electrode, a negative electrode (12), and a separator disposed between the positive electrode and the negative electrode (12), wherein the positive electrode and the negative electrode (12) are wound with the separator interposed therebetween. One electrode (12) of the negative electrode (12) and the positive electrode has: a core body; a lamination part in which a mixture layer is laminated on at least one surface of the core body; and an uncoated part (44) which is provided at an end portion positioned closer to one side in the axial direction than the lamination part, and in which the mixture layer is not laminated. The tip-side portion of the uncoated part (44) is continuously tilted toward the inner peripheral side along the entire periphery.

Description

Electrode body for a power storage device, power storage device, and method for manufacturing an electrode body for a power storage device

[0001] The present disclosure relates to an electrode body for a power storage device, a power storage device, and a method for manufacturing an electrode body for a power storage device.

[0002] Conventionally, as described in Patent Document 1, as a secondary battery, an uncoated portion where the mixture layer of the core of the negative electrode is not laminated is projected from the axial end portion of the electrode body, and the projected uncoated portion and the current collector are welded. This configuration is known. In this configuration, in order to facilitate welding, protruding portions extending in the radial direction are formed at four positions on the end surface of the current collector or the pressing jig, and the four protruding portions are pressed against the tips of the uncoated portions rising in the axial direction, thereby pushing down the four positions in the circumferential direction of the uncoated portion to the inner circumferential side.

[0003] Japanese Patent Application Laid-Open No. 2010-257851

[0004] In the configuration described in Patent Document 1, at the end of the negative electrode, it is largely pushed down to the inner circumferential side only at four positions that are widely separated in the circumferential direction of the uncoated portion. At this time, there is a portion that is not pushed down to the inner circumferential side in a part of the circumferential direction of the uncoated portion of the negative electrode. In this configuration, a large local load is likely to be applied to the uncoated portion of the negative electrode. As a result, there is a possibility that foreign matter deposition occurs due to the separation of the mixture layer from the core in the vicinity of the uncoated portion of the negative electrode. On the other hand, if the load when pushing down the uncoated portion of the negative electrode is too small, the overall amount of pushing down of the uncoated portion to the inner circumferential side becomes small, and the axial length of the electrode body becomes large, so there is a possibility that the electrode body cannot fit into the outer can. In the above, the disadvantages in the uncoated portion of the negative electrode were explained, but when pushing down the uncoated portion at the end of the positive electrode, the same disadvantages as above occur. Also, in the above, the disadvantages of the electrode body for a secondary battery were explained, but the same disadvantages may occur in electrode bodies for power storage devices other than secondary batteries.

[0005] Therefore, an object of the present disclosure is to provide an electrode body for a power storage device, a power storage device, and a method for manufacturing an electrode body for a power storage device that can prevent the separation of the mixture layer from the core in the vicinity of the uncoated portion of the electrode and can sufficiently increase the amount of pushing down of the uncoated portion at the end of the electrode to the inner circumferential side.

[0006] The electrode body for an energy storage device according to this disclosure comprises a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the positive electrode and the negative electrode are wound around the separator, and one of the negative electrode and the positive electrode has a core body and a laminated portion on at least one side of the core body on which a composite layer is laminated, and an uncoated portion provided at the end located axially to one side of the laminated portion, on which the composite layer is not laminated, and the tip portion of the uncoated portion is continuously bent inward along its entire circumference.

[0007] The energy storage device according to this disclosure comprises an electrode body for the energy storage device according to this disclosure and an outer casing for housing the electrode body, and a current collector plate is attached to the tip of the unpainted portion.

[0008] The first method for manufacturing an electrode body for an energy storage device according to this disclosure includes a pressing step in which the electrode body is held, the lower surface of the molding plate is inclined with respect to the horizontal direction, and the electrode body is pressed against an uncoated portion located at the upper end of the electrode body, thereby pressing it down, and the electrode body is rotated around an axis along the vertical direction, wherein the contact point between the uncoated portion and the molding plate is moved in a spiral shape from the outside to the inside at the upper end of the uncoated portion, and the inclination angle of the lower surface of the molding plate with respect to the horizontal plane is reduced along the trajectory of the contact point from the initial pressing to the final pressing.

[0009] The second method for manufacturing an electrode body for an energy storage device according to this disclosure includes a step in which, while holding the electrode body in a holding part, the electrode body is rotated around an axis in the vertical direction, the holding part is moved along a horizontal linear path, and as the holding part moves, a hemispherical pressing part, which is previously supported on the upper side of the linear path, is pressed from the outer circumference side against an uncoated part extending in the vertical direction, and the uncoated part is pushed down toward the inner circumference, and in the pushing down step, the contact point between the uncoated part and the pressing part is moved in a spiral shape from the outside toward the inside at the upper end of the uncoated part.

[0010] According to this disclosure, in an electrode body for an energy storage device, the tip portion of the uncoated area at the end of the electrode is continuously tilted inward along its entire circumference. This allows for a sufficiently large amount of inward tilting of the uncoated area without applying large localized loads to the tip portion of the uncoated area at multiple widely separated positions in the circumferential direction. As a result, peeling of the composite layer from the core body near the uncoated area of ​​the electrode can be prevented, and the amount of inward tilting of the uncoated area at the end of the electrode can be sufficiently large.

[0011] This is an axial cross-sectional view of a secondary battery, which is an energy storage device according to one embodiment of the present disclosure. This is a perspective view showing a portion of the electrode body for a secondary battery, which is an electrode body for an energy storage device according to the embodiment, unfolded before both axial ends are pushed down. This is an enlarged view corresponding to part A in Figure 1 before the negative electrode current collector plate is joined to the electrode body for a secondary battery according to the embodiment. This is a diagram showing the electrode body for a secondary battery removed from Figure 1 and viewed from below. This is a diagram showing one example of a method for pushing down the unpainted portion of the negative electrode toward the inner circumference in the manufacturing method of the electrode body for a secondary battery according to the embodiment. This is a schematic perspective view showing the state when one circumferential portion of a part of the electrode body for a secondary battery is pushed down toward the inner circumference in the embodiment. This is a diagram showing the trajectory traced by the contact point between the molding plate and the unpainted portion when the unpainted portion is pushed down toward the inner circumference in the manufacturing method of the electrode body for a secondary battery according to the embodiment. This is a diagram showing the relationship for control between the radial distance (r) from the central axis of the electrode body to the contact point between the molding plate and the unpainted portion and the angle θ made with the horizontal plane of the lower surface of the molding plate in the embodiment. This is a schematic diagram showing the change in the inclination angle of the lower surface of the molding plate with respect to the horizontal plane when the contact point between the molding plate and the unpainted portion moves inward in half of the cross-section of the unpainted portion in the embodiment. This is a diagram showing the electrode body for a secondary battery from another embodiment, taken out and viewed from below. This is a perspective view of the processing device for pushing the unpainted portion of the negative electrode inward in the manufacturing method of the electrode body for a secondary battery from another embodiment. This is a schematic diagram showing the state of the holding part that holds the electrode body in the processing device shown in Figure 9 before it starts to move. This is a schematic diagram showing the state in which the pressing part of the pressing jig is pressed against the unpainted portion of the negative electrode using the processing device shown in Figure 9.

[0012] Hereinafter, embodiments of the electrode body for the energy storage device, the energy storage device, and the method for manufacturing the electrode body for the energy storage device according to this disclosure will be described in detail with reference to the drawings. Note that the energy storage device of this disclosure may be a secondary battery other than the secondary battery described below, such as a capacitor. The secondary battery may be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. In the following, a cylindrical non-aqueous electrolyte secondary battery will be described as the secondary battery in the embodiment of the energy storage device, but the energy storage device of this disclosure can employ various configurations as long as it is an energy storage device equipped with a wound electrode body.

[0013] It is intended from the outset that new embodiments can be constructed by appropriately combining the characteristic features of the embodiments and modifications described below. In the following embodiments, the same reference numerals are used for the same components in the drawings, and redundant explanations are omitted. In addition, multiple drawings include schematic diagrams, and the dimensional ratios such as length, width, and height of each component do not necessarily match between different drawings. In this specification, the axial opening side of the outer casing 15 of the cylindrical secondary battery 10 is referred to as "upper," and the axial bottom side is referred to as "lower." That is, the bottom of the outer casing 15 is described as the lower end. The energy storage devices of this disclosure are not necessarily limited to those in which the bottom of the outer casing is located vertically below when in use. For example, the bottom of the outer casing may be configured to be vertically above the opening of the outer casing when in use. Furthermore, this disclosure is not limited to the embodiments and modifications described below, and various improvements and changes are possible within the scope of the claims of this application and their equivalents.

[0014] Figure 1 is an axial cross-sectional view of a secondary battery 10, which is an energy storage device according to the embodiment. Figure 2 is a perspective view of a secondary battery electrode body 14, which is an electrode body for an energy storage device according to the embodiment, showing a portion of both axial ends unfolded before being pushed down. Hereinafter, the secondary battery electrode body 14 will be referred to as electrode body 14.

[0015] As shown in Figures 1 to 4, the secondary battery 10 comprises a wound electrode body 14, a non-aqueous electrolyte (not shown), and an outer casing 15 and a sealing body 16, which are metal cans. The wound electrode body 14 has a positive electrode 11, a negative electrode 12, and a separator 13, with the positive electrode 11 and the negative electrode 12 wound in a spiral shape via the separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 are all in the shape of a roughly rectangular, elongated strip. The non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.

[0016] In the electrode body 14, as shown in Figure 2, the positive electrode 11 protrudes above the negative electrode 12 and the separator 13, and the negative electrode 12 protrudes below the positive electrode 11 and the separator 13.

[0017] As shown in Figure 2, the positive electrode 11 has an uncoated positive electrode portion 34 in which the positive electrode core 30 is exposed without a positive electrode mixture layer 32. The uncoated positive electrode portion 34 is located at the upper end, which is one end in the winding axis direction (hereinafter sometimes referred to as the axis direction) from the winding start end to the winding end in the longitudinal direction of the electrode plate of the positive electrode 11. The longitudinal direction of the electrode plate is the direction corresponding to the winding direction in the wound state of the positive electrode 11 or negative electrode 12, and is the longitudinal direction of the elongated rectangle when the positive electrode 11 or negative electrode 12 is viewed in the thickness direction when the positive electrode 11 or negative electrode 12 is unfolded along a plane.

[0018] The negative electrode 12 has an uncoated negative electrode portion 44 in which the negative electrode core body 40 (Figure 2) is exposed without a negative electrode mixture layer 42 (Figure 2). The uncoated negative electrode portion 44 is located at the lower end, which is the other end in the axial direction, from the beginning end to the end end in the longitudinal direction of the electrode plate of the negative electrode 12. Therefore, the upper end in the axial direction of the electrode body 14 is composed of the uncoated positive electrode portion 34, and the lower end in the axial direction of the electrode body 14 is composed of the uncoated negative electrode portion 44.

[0019] The non-aqueous electrolyte has ionic conductivity (e.g., lithium ion conductivity). The non-aqueous electrolyte comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte is not limited to a liquid electrolyte (non-aqueous electrolyte solution), but may also be a solid electrolyte using a gel-like polymer or the like. The secondary battery 10 is preferably a lithium-ion battery. The electrolyte salt may be, for example, LiBF ４ LiPF６ Lithium salts such as the above are used. Non-aqueous solvents include, for example, esters such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP), as well as ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may contain halogen-substituted products in which at least some of the hydrogen atoms of these solvents are replaced with halogen atoms such as fluorine.

[0020] Examples of halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated linear carbonates, and fluorinated linear carboxylic acid esters such as methyl fluoropropionate (FMP). In terms of suppressing the deterioration of the charge-discharge cycle characteristics of non-aqueous electrolyte secondary batteries or improving the input characteristics, the non-aqueous electrolyte preferably contains 5% by mass or more of FEC relative to the mass of the non-aqueous electrolyte, and more preferably contains 5% to 15% by mass of FEC.

[0021] As solid electrolytes, for example, solid or gel-like polymer electrolytes, inorganic solid electrolytes, etc., are used. Polymer electrolytes include, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As matrix polymers, for example, polymer materials that absorb non-aqueous solvents and gel are used. As polymer materials, for example, fluororesins, acrylic resins, polyether resins, etc., are used. As inorganic solid electrolytes, for example, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.) are used.

[0022] The positive electrode 11 has a positive electrode core 30 and a positive electrode mixture layer 32 formed on both sides of the positive electrode core 30. The positive electrode core 30 can be made of a metal foil that is stable in the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal arranged on its surface. The thickness of the positive electrode core 30 is, for example, 10 μm or more and 30 μm or less. The positive electrode mixture layer 32 contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core 30, drying the coating film, and then compressing it to form the positive electrode mixture layer 32 on both sides of the positive electrode core 30. The positive electrode mixture layer 32 may be formed on only one side of the positive electrode core 30. The thickness of the positive electrode mixture layer 32 is, for example, 10 μm to 150 μm on one side of the positive electrode core 30.

[0023] The positive electrode active material is mainly composed of a lithium-containing metal composite oxide. Examples of metal elements contained in the lithium-containing metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. A preferred example of a lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al.

[0024] Examples of conductive agents included in the positive electrode mixture layer 32 include carbon materials such as carbon black, acetylene black, Ketjen black, and graphite. Examples of binders included in the positive electrode mixture layer 32 include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resin, acrylic resin, and polyolefin resin. These resins may be used in combination with cellulose derivatives such as carboxymethylcellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

[0025] On both sides of the upper end of the positive electrode core 30, a positive electrode protective layer may be provided between the positive electrode mixture layer 32 and the uncoated positive electrode portion 34. The positive electrode protective layer can be an inorganic filler protective layer composed of, for example, an inorganic material additive such as alumina, a resin such as a water-insoluble polymer such as polyvinylidene fluoride (PVdF), and a conductive additive such as acetylene black (AB) or carbon black (CB) in a predetermined ratio.

[0026] The negative electrode 12 has a negative electrode core 40 and a negative electrode mixture layer 42 formed on both sides of the negative electrode core 40. The negative electrode core 40 can be made of a metal foil that is stable in the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with the metal arranged on its surface. The thickness of the negative electrode core 40 is, for example, 5 μm to 30 μm. The negative electrode mixture layer 42 contains a negative electrode active material and a binder. The negative electrode 12 can be manufactured, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder onto the negative electrode core 40, drying the coating, and then compressing it to form the negative electrode mixture layer 42 on both sides of the negative electrode core 40. The negative electrode mixture layer 42 may be formed on only one side of the negative electrode core 40. The thickness of the negative electrode mixture layer 42 is, for example, 10 μm to 150 μm on one side of the negative electrode core 40.

[0027] Generally, carbon materials that reversibly intercalate and release lithium ions are used as the negative electrode active material. Preferred carbon materials are graphite such as natural graphite such as flake graphite, lump graphite, and earthy graphite, and artificial graphite such as lump graphite and graphitized mesophase carbon microbeads. The negative electrode mixture layer 42 may contain a silicon (Si) material as the negative electrode active material. In addition, metals other than Si that alloy with lithium, alloys containing such metals, compounds containing such metals, etc., may be used as the negative electrode active material.

[0028] The binder contained in the negative electrode mixture layer 42 may be fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, etc., as in the case of the positive electrode 11, but preferably styrene-butadiene rubber (SBR) or a modified version thereof is used. In addition to SBR, the negative electrode mixture layer 42 may also contain CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, etc.

[0029] A porous sheet having ion permeability and insulating properties is used for the separator 13. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. The material of the separator 13 is preferably polyethylene, polyolefin resins such as polypropylene, or cellulose. The separator 13 may have either a single-layer structure or a laminated structure. A heat-resistant layer or the like may be formed on the surface of the separator 13.

[0030] As shown in Figure 1, the secondary battery 10 has a negative electrode current collector plate 17 made of metal, such as nickel or a nickel alloy, on the axially lower side of the electrode body 14. The negative electrode current collector plate can be cross-shaped or disc-shaped, etc. An unpainted negative electrode portion 44 protruding from the electrode body 14 is joined to the negative electrode current collector plate 17, and the negative electrode current collector plate 17 is joined to the inner surface of the bottom plate of the outer casing 15. The outer casing 15, to which the unpainted negative electrode portion 44 is electrically connected via the negative electrode current collector plate 17, becomes the negative electrode terminal.

[0031] The secondary battery 10 has a positive electrode current collector plate 18 located inside the outer casing 15. The positive electrode current collector plate 18 is a metal disc made of aluminum or an aluminum alloy, etc., and is located above the electrode body 14 in the axial direction. When the positive electrode current collector plate 18 is disc-shaped, a through hole is formed to allow gas generated in the electrode body to escape upward. The unpainted positive electrode portion 34 protruding from the electrode body 14 is joined to the positive electrode current collector plate 18 in a state where it is pushed inward in at least a part of its circumferential direction. As a result, the positive electrode current collector plate 18 is fixed to the upper end of the electrode body 14 in the axial direction and electrically connected. The secondary battery 10 has an annular insulating plate 19 above the positive electrode current collector plate 18 in the axial direction.

[0032] One end of the positive electrode connection lead 20 is joined to the upper surface of the positive electrode current collector plate 18 by welding or the like. The positive electrode connection lead 20 extends through a through-hole in the insulating plate 19 towards the sealing body 16, and the other end of the positive electrode connection lead 20 is connected to the lower surface of the internal terminal plate 22 of the sealing body 16 by welding or the like. The cap 26 that forms the top plate of the sealing body 16 is electrically connected to the internal terminal plate 22. As a result, the positive electrode current collector plate 18 is electrically connected to the cap 26, and the cap 26 becomes the positive electrode terminal. The positive electrode connection lead 20 is a conductive member made of a metal mainly composed of aluminum.

[0033] The secondary battery 10 further includes a resin gasket 27 positioned between the outer casing 15 and the sealing body 16. The gasket 27 is sandwiched between the outer casing 15 and the sealing body 16, insulating the sealing body 16 from the outer casing 15. The gasket 27 serves as a sealing material to maintain airtightness inside the battery and as an insulating material to insulate the outer casing 15 from the sealing body 16. The outer casing 15 has an annular groove 21 in a part of its axial direction.

[0034] The grooved portion 21 can be formed, for example, by spinning a part of the side surface radially inward to create a recess in the radial direction. The outer casing 15 has a bottomed cylindrical portion including the grooved portion 21 and an annular shoulder portion. The bottomed cylindrical portion houses the electrode body 14 and the non-aqueous electrolyte, and the shoulder portion is bent radially inward from the opening end of the bottomed cylindrical portion and extends inward. The shoulder portion is formed when the upper end of the outer casing 15 is bent inward and crimped to the periphery of the sealing body 16. The sealing body 16 is crimped and fixed to the outer casing 15 via a gasket 27 between the shoulder portion and the grooved portion 21. In this way, the internal space of the secondary battery 10 is sealed.

[0035] The sealing body 16 has a structure in which an internal terminal plate 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26 are stacked in order from the electrode body 14 side. Each component constituting the sealing body 16 has, for example, a disc shape or a ring shape, and each component except the insulating member 24 is electrically connected to one another. The internal terminal plate 22 has at least one through hole. The lower valve body 23 and the upper valve body 25 are connected at their respective centers, and the insulating member 24 is interposed between their respective peripheral edges.

[0036] When the secondary battery 10 overheats abnormally and its internal pressure rises to a predetermined value, the lower valve body 23 deforms and ruptures, pushing the upper valve body 25 towards the cap 26, thereby interrupting the current path between the lower valve body 23 and the upper valve body 25. If the internal pressure rises further and reaches a predetermined value, the upper valve body 25 ruptures, and gas is discharged from the through-hole 26a of the cap 26. This gas discharge prevents the secondary battery 10 from deforming or rupturing due to an excessive rise in internal pressure, thereby improving the safety of the secondary battery 10. Furthermore, it can suppress the impact on adjacent components (not shown) due to deformation or rupture of the secondary battery 10.

[0037] Next, with reference to Figures 1 to 4, the surrounding configuration of the joint between the electrode body 14 and the negative electrode current collector plate 17 at the bottom of the secondary battery 10, and the configuration of the negative electrode 12 will be explained. Figure 3 is an enlarged view corresponding to part A in Figure 1 of the electrode body 14 before the negative electrode current collector plate 17 is joined. Figure 4 is a view of the electrode body 14 taken out of Figure 1 and viewed from below.

[0038] As shown in Figure 3, the negative electrode 12 has a laminated portion 45 in which a negative electrode mixture layer 42 is laminated on both sides of the negative electrode core body 40, and an uncoated negative electrode portion 44 provided at the end located on the lower side (one axial side) of the laminated portion 45, on the negative electrode current collector plate 17 side. The uncoated negative electrode portion 44 has an axial extension portion 47 extending substantially parallel to the axial direction of the electrode body 14, and an inward-facing tilted portion 48 tilted inward from the lower end of the axial extension portion 47. The inward-facing tilted portion 48 is welded to the upper surface of the negative electrode current collector plate 17. As a result, the uncoated negative electrode portion 44 is provided at the lower axial end of the negative electrode 12 on the negative electrode current collector plate 17 side, and the negative electrode mixture layer is not laminated therein.

[0039] In this example, the tip portion of the uncoated negative electrode section 44 is continuously tilted inward along its entire circumference. This prevents the negative electrode mixture layer 42 from peeling off from the negative electrode core 40 at the end of the negative electrode 12, as described later, and allows for a sufficiently large amount of inward tilting of the uncoated negative electrode section 44.

[0040] More specifically, in this example, when viewed from the lower side which is one side in the axial direction, the entire area from the outer peripheral side end to the inner peripheral side end of the uncoated negative electrode portion 44 is tilted inward such that the tip of the uncoated negative electrode portion 44 is arranged in a spiral shape with a decreasing radius of curvature toward the inner circumference.

[0041] Note that the uncoated negative electrode portion 44 may be configured such that when viewed from the lower side, only a part from the outer peripheral side end to the inner peripheral side end, for example, from the outer peripheral side end to between the outer peripheral side end and the inner peripheral side end, is tilted inward such that the tip of the uncoated negative electrode portion 44 is arranged in a spiral shape with a decreasing radius of curvature toward the inner circumference.

[0042] Furthermore, in the uncoated negative electrode portion 44, a plurality of unit elements 49 that are laminated in the radial direction in a part in the circumferential direction and are integrated and displaced in the circumferential direction are arranged in a spiral shape. Some of the unit elements 49 are tilted inward in the radial direction with a part of the end portion in the circumferential direction overlapping so as to enter the inner circumference side with respect to another unit element 49 adjacent to one side in the circumferential direction, thereby forming a folding portion 50, and the folding portion 50 is repeated in the spiral direction together with the unit elements 49.

[0043] For example, in the example shown in FIG. 4, the unit element 49 indicated by B1 in a part in the circumferential direction is tilted inward in the radial direction with a part of the end portion B1 in the circumferential direction overlapping so as to enter the inner circumference side with respect to the unit element 49 indicated by B2 adjacent to the right side in FIG. 4 which is one side in the circumferential direction, thereby forming a folding portion 50, and the folding portion 50 is repeated in the spiral direction. As a result, while the folding portion 50 absorbs the surplus portion generated in the portion including the tip edge due to the tilting of the uncoated negative electrode portion 44 toward the inner circumference side, the tip portion of the uncoated negative electrode portion can be continuously tilted toward the inner circumference side along the spiral direction.

[0044] Next, with reference to Figures 5 to 8B, the method for tilting the uncoated negative electrode portion 44 toward the inner circumference in the manufacturing method of the electrode body 14 will be explained in more detail. Figure 5 is a diagram showing one example of the method for pushing the uncoated negative electrode portion 44 of the negative electrode 12 toward the inner circumference in the manufacturing method of the electrode body 14. As shown in Figure 5, the uncoated negative electrode portion 44, in its axially upright state before being tilted toward the inner circumference, has a flat shape with no irregularities throughout its tip edge. This makes it easier to tilt the tip portion of the uncoated negative electrode portion 44 toward the inner circumference, and thus suppresses an increase in electrical resistance, unlike the case where the tip edge of the uncoated negative electrode portion 44 has a shape with repeated irregularities along the longitudinal direction of the electrode plate, which is the winding direction.

[0045] The manufacturing method of the electrode body 14 in this example includes a pressing step. In the pressing step, the electrode body 14 is held by a holding part (not shown) as shown in Figure 5, such that the projection 62 extending axially from the uncoated negative electrode portion 44 is at the upper end and the axial direction coincides with the vertical direction. Then, with the lower surface 61 of the flat molding plate 60 inclined with respect to the horizontal direction along the horizontal plane L, it is pressed against the outer peripheral end of the uncoated negative electrode portion 44 located at the upper end of the electrode body 14, thereby pressing down the uncoated negative electrode portion 44. At the same time, the electrode body 14 is rotated around the central axis O of the electrode body 14, which is the axis of rotation along the vertical direction. For this purpose, for example, the holding part that holds the electrode body 14 is rotated in the direction of arrow α around the central axis O by a rotation drive part (not shown). The rotation drive part includes a motor, and the rotation shaft of the motor, which is oriented in the vertical direction, rotates the holding part.

[0046] As a result, a load is applied to the uncoated negative electrode portion 44 from the lower surface 61 of the molding plate 60, causing the tip of the uncoated negative electrode portion 44 to bend inward. At this time, as schematically shown in Figure 6, in a part of the circumferential direction of the uncoated negative electrode portion 44, the part that will become another unit element 49 on the left side moves inward with the part that will become the unit element 49 on the right side of Figure 6(a), which is one side in the circumferential direction, as it bends inward. As a result, two unit elements 49 connected by a folded portion 50 are formed, as shown in Figure 6(b), and this is repeated in the circumferential direction. As a result, the portion of the uncoated negative electrode portion 44 that is pushed inward continues in the circumferential direction along the entire circumference.

[0047] Further, in the pushing-down step, the contact point between the uncoated negative electrode portion 44 and the forming plate 60 (FIG. 5) is moved spirally from the outside to the inside at the upper end of the uncoated negative electrode portion 44, and the inclination angle of the lower surface of the forming plate 60 with respect to the horizontal plane is decreased from the initial pressing stage to the final pressing stage along the locus of the contact point. FIG. 7 shows the control locus drawn by the contact point between the forming plate 60 and the uncoated negative electrode portion 44 when the uncoated negative electrode portion 44 is pushed down to the inner peripheral side. The contact point moves from C1 to C2. C2 is located on the central axis O. The forming plate 60 shown in FIG. 5 is configured to be able to change the inclination angle with respect to the horizontal plane about a horizontal axis so as to draw this movement locus.

[0048] Further, FIG. 8A shows the relationship for control between the radial distance (r) from the central axis O of the electrode body 14 to the contact point between the forming plate 60 and the uncoated negative electrode portion 44, and the inclination angle θ of the lower surface of the forming plate 60 with respect to the horizontal plane L. As shown in FIG. 8, when the radial distance r changes from the radial distance r1 at the C1 position in FIG. 7 to the radial distance 0 at the C2 position, the inclination angle θ decreases linearly and monotonically.

[0049] When the contact point moves along the movement locus in this way, for example, when the contact point is at the C3 position, the radial distance r3 between the contact point and the central axis O of the electrode body 14 is determined. From the radial distance r3 and the relationship shown in FIG. 8A, the inclination angle θ of the lower surface of the forming plate 60 is determined.

[0050] The inclination angle θ of the lower surface 61 of the forming plate 60 with respect to the horizontal plane L is changed by an inclination angle changing mechanism including a motor (not shown). At this time, the inclination angle changing mechanism is controlled by the control device so that the inclination angle θ changes according to the movement locus shown in FIG. 7.

[0051] As a result, in the electrode body 14, the upper end of the uncoated negative electrode portion 44 is gradually pushed to the inner peripheral side by the forming plate 60 from the outer peripheral side to the inner peripheral side.

[0052] For example, as schematically shown in Figure 8B, the inclination angle of the lower surface of the molding plate 60 gradually decreases from θ1 to θ4. In Figure 8B, the lines L1, L2, L3, and L4 schematically represent the lower surface of the molding plate 60. In Figure 8B, one side of the cross-sectional shape of the axial cross-section of the electrode body 14 is schematically shown as a rectangle. Line L1 indicates the initial pressing position of the uncoated negative electrode portion by the molding plate 60, and the pressing position changes toward the inner circumference in the order of lines L2, L3, and L4. At this time, the amount of pushing down of the uncoated negative electrode portion by the molding plate 60 at each contact point can be made almost uniform, and the amount of pushing down at each point is small. Therefore, it is possible to further suppress the application of a large localized load to the uncoated negative electrode portion, and thus more reliably prevent the peeling of the negative electrode mixture layer from the negative electrode core. In addition, the final deformation amount of the uncoated negative electrode portion by the molding plate can be increased. As a result, the amount of pushing down of the uncoated negative electrode portion before and after the pushing down step can be made sufficiently large.

[0053] Furthermore, in this example, the winding direction of the electrode body 14 coincides with the rotation direction α of the electrode body 14 when the uncoated negative electrode portion 44 is pushed down. As a result, as shown in Figure 4, when the electrode body 14 is viewed from the axial side of the uncoated negative electrode portion 44, the uncoated negative electrode portion 44 is tilted inward in the winding direction, with the circumferential end of the front unit element 49 overlapping the inner circumference of the adjacent unit element 49 on the rear side in the winding direction.

[0054] According to the electrode body 14 and its manufacturing method described above, the tip portion of the uncoated negative electrode portion 44 at the end of the negative electrode 12 is continuously tilted inward along its entire circumference. This allows for a sufficiently large amount of inward tilting of the uncoated negative electrode portion 44 without applying large localized loads at multiple widely separated positions in the circumferential direction to the tip portion of the uncoated negative electrode portion 44. As a result, peeling of the negative electrode mixture layer 42 from the negative electrode core body 40 near the uncoated negative electrode portion 44 of the negative electrode 12 can be prevented, and the amount of inward tilting of the uncoated negative electrode portion 44 can be sufficiently large.

[0055] The above describes the configuration of the part that pushes the uncoated portion of the negative electrode 12 inward and a method for obtaining that configuration. However, the configuration of the part that pushes the uncoated portion of the positive electrode 11 inward and a method for obtaining that configuration can be configured in the same way as the uncoated portion of the negative electrode 12. In this case, the configuration of the embodiment can be applied to the configuration of the part that pushes one or both of the uncoated portions of the positive electrode and the negative electrode inward.

[0056] Figure 8C shows an electrode body 14a from another embodiment, viewed from below, which is the side of the uncoated negative electrode portion 44 in the axial direction. In this example, the winding direction of the electrode body 14a and the rotation direction β of the electrode body 14a when the uncoated negative electrode portion 44 is pushed down are opposite. As a result, as shown in Figure 8C, when the electrode body 14a is viewed from below in the axial direction, the uncoated negative electrode portion 44 is tilted inward in the winding direction, with the circumferential end of the front unit element 49a overlapping the outer circumference of the adjacent unit element 49a on the rear side in the winding direction. In this example, the other configurations and operations are the same as those in Figures 1 to 8B.

[0057] Figure 9 is a perspective view of a processing device 90 for pushing down the uncoated negative electrode portion 44 toward the inner circumference in a method for manufacturing an electrode body 14 in another embodiment. The processing device 90 includes a guide member 91 having a horizontal straight path such as a rail on its upper side, a movable part 92 provided to be movable along the straight path, a holding part 94 supported above the movable part 92 and holding the electrode body 14 in the upper position, and a columnar first support part 95 provided to stand upright integrally with the guide member 91.

[0058] The movable part 92 moves along a straight path by a robot cylinder mechanism or the like. The holding part 94 protrudes above the movable part 92 and is fixed to the upper end of a rotating shaft 93 that is aligned in the vertical direction, and is rotatable. The rotating shaft 93 is rotationally driven by a motor (not shown) provided inside the movable part 92. The electrode body 14 is held by the holding part 94 so that its axial direction is aligned in the vertical direction, and the uncoated negative electrode portion 44 extending in the axial direction is positioned at its upper end. The axial direction of the electrode body 14 is located on the extension of the rotating shaft 93.

[0059] A second support portion 96 is provided above the first support portion 95, which is movable in the vertical direction and fixed in position by a screw (not shown). The second support portion 96 has a plate portion 97 that protrudes laterally from its lower end, and a hemispherical pressing portion 98 is supported below the plate portion 97. The pressing portion 98 can rotate freely around an axis in the vertical direction relative to the plate portion 97. As a result, the pressing portion 98 is supported in advance on the upper side of the straight path.

[0060] Figure 10 is a schematic diagram showing the state of the holding part 94 that holds the electrode body 14 in the processing apparatus 90 before movement begins. Figure 11 is a schematic diagram showing the state in which the pressing part 98 has been moved downward using the processing apparatus 90 and is pressed against the uncoated negative electrode portion 44 at the upper end.

[0061] When processing the uncoated negative electrode portion 44 to tilt inward using the processing device 90, the electrode body 14 held by the holding portion 94 is rotated around an axis aligned vertically by the rotation of the rotating shaft 93. While rotating the electrode body 14, the holding portion 94 is moved along a linear path together with the moving portion 92. At this time, the moving portion 92 is moved at a constant speed in the horizontal direction. As the holding portion 94 moves, the hemispherical pressing portion 98 is pressed against the uncoated negative electrode portion 44, which extends vertically, from the outer circumference, performing a pushing-down step that pushes the uncoated negative electrode portion 44 inward. In this pushing-down step, the uncoated negative electrode portion 44 is pressed by the pressing portion 98 for two or more rotations. As a result, the contact point between the uncoated negative electrode portion 44 and the pressing portion 98 moves in a spiral shape from the outside to the inside at the upper end of the uncoated negative electrode portion 44. Therefore, the amount of deformation of the uncoated portion 44 of the negative electrode due to the pressing portion 98 over one rotation is reduced, while the uncoated portion 44 of the negative electrode can be tilted significantly towards the inner circumference.

[0062] As a result, as shown in Figure 4 or Figure 8C, an electrode body 14 can be obtained in which the uncoated negative electrode portion 44 is continuously tilted inward along its entire circumference, and when the uncoated negative electrode portion 44 is viewed from one axial side, the tip of the uncoated negative electrode portion 44 is arranged spirally inward. In this example, the other configurations and operations are the same as those in Figures 1 to 8B or Figure 8C.

[0063] This disclosure is further illustrated by the following embodiments. Configuration 1: An electrode body for an energy storage device, comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the positive electrode and the negative electrode are wound around the separator, and one of the negative electrode and the positive electrode has a core body and a laminated portion on at least one side of the core body on which a composite layer is laminated, and an uncoated portion provided at an end located axially to one side of the laminated portion, on which the composite layer is not laminated, wherein the tip portion of the uncoated portion is continuously bent inward along its entire circumference. Configuration 2: The electrode body for an energy storage device according to Configuration 1, wherein, when viewed from the axial side, at least a portion of the uncoated portion is bent inward so that the tip of the uncoated portion is arranged in a spiral shape with a decreasing radius of curvature towards the inward circumference. Configuration 3: The electrode body for a power storage device according to Configuration 2, wherein the unpainted portion is bent inward so that, when viewed from one side in the axial direction, the tip of the unpainted portion is arranged spirally from the outer edge to the inner edge. Configuration 4: The electrode body for a power storage device according to Configuration 2, wherein a circumferential portion of the unpainted portion is bent inward so that a portion in the circumferential direction is recessed into the inner circumference with respect to a portion adjacent to one side in the circumferential direction, with the ends of the circumferential portion overlapping in the radial direction, thereby forming a folded portion, and the folded portion is repeated in the spiral direction. Configuration 5: The electrode body for a power storage device according to any one of Configurations 1 to 4, wherein one of the electrodes is the negative electrode. Configuration 6: The electrode body for a power storage device according to any one of Configurations 1 to 5, wherein the unpainted portion, when standing upright in the axial direction before being bent inward, has a flat tip edge with no irregularities throughout. Configuration 7: An energy storage device comprising an electrode body for an energy storage device described in any one of Configurations 1 to 6, and an outer can for housing the electrode body, wherein a current collector plate is joined to the tip of the unpainted portion.Configuration 8: A method for manufacturing an electrode body for an energy storage device as described in Configuration 1, comprising a pressing step in which the electrode body is held, the lower surface of a molding plate is inclined with respect to the horizontal direction, and the electrode body is pressed against the unpainted portion located at the upper end of the electrode body and pressed down, and the electrode body is rotated around an axis along the vertical direction, wherein in the pressing step, the contact point between the unpainted portion and the molding plate is moved in a spiral shape from the outside to the inside at the upper end of the unpainted portion, and the inclination angle of the lower surface of the molding plate with respect to the horizontal plane is reduced along the trajectory of the contact point from the initial pressing to the final pressing stage. Configuration 9: A method for manufacturing an electrode body for an energy storage device as described in Configuration 1, comprising: holding the electrode body in a holding part, rotating the electrode body around an axis extending in the vertical direction, moving the holding part along a horizontal straight path, and, as the holding part moves, pressing a hemispherical pressing part, which has been previously supported on the upper side of the straight path, against the unpainted part extending in the vertical direction from the outer circumference, thereby pushing the unpainted part inward in a pushing-down step, wherein in the pushing-down step, the contact point between the unpainted part and the pressing part moves in a spiral shape from the outside to the inside at the upper end of the unpainted part.

[0064] 10 Secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14, 14a Electrode body for secondary battery (electrode body), 15 Outer can, 16 Sealing body, 17 Negative electrode current collector plate, 18 Positive electrode current collector plate, 19 Insulating plate, 20 Positive electrode connection lead, 21 Grooved section, 22 Internal terminal plate, 23 Lower valve body, 24 Insulating member, 25 Insulating member, 25 Upper valve body, 26 Cap, 27 Gasket, 30 Positive electrode core body, 32 Positive electrode mixture layer, 34 Positive electrode uncoated section, 40 Negative electrode core body, 42 Negative electrode mixture layer, 44 Negative electrode uncoated section, 45 Laminated section, 47 Axial extension section, 48 Inner circumference side tilted section, 49 Unit element, 50 Folded section, 60 Molding plate, 61 Lower side surface, 62 90 Protruding part, 91 Processing device, 92 Guide member, 92 Moving part, 93 Rotating shaft, 94 Holding part, 95 First support part, 96 Second support part, 97 Plate part, 98 Pressing part.

Claims

1. An electrode body for an energy storage device, comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the positive electrode and the negative electrode are wound around the separator, wherein one of the negative electrode and the positive electrode has a core body and a laminated portion on at least one side of the core body on which a composite layer is laminated, and has an uncoated portion provided at an end located axially to one side of the laminated portion, on which the composite layer is not laminated, and the tip portion of the uncoated portion is continuously bent inward along its entire circumference.

2. The electrode body for an energy storage device according to claim 1, wherein, when viewed from one side in the axial direction, at least a portion of the uncoated portion is tilted inward so that the tip of the uncoated portion is arranged in a spiral shape with a decreasing radius of curvature toward the inner circumference.

3. The electrode body for an energy storage device according to claim 2, wherein the uncoated portion is tilted inward so that, when viewed from one side in the axial direction, the tip of the uncoated portion is arranged spirally from the outer circumference end to the inner circumference end.

4. The electrode body for an energy storage device according to claim 2, wherein a portion of the uncoated portion in the circumferential direction folds inward in a radial direction, with the end of the portion overlapping with the portion adjacent to one side in the circumferential direction, thereby forming a folded portion, and the folded portion is repeated in a spiral direction.

5. The electrode body for an energy storage device according to claim 1, wherein one of the electrodes is the negative electrode.

6. The electrode body for an energy storage device according to claim 1, wherein the uncoated portion, when in an axially upright state before being tilted toward the inner circumference, has a flat surface with no irregularities throughout its tip edge.

7. An energy storage device comprising an electrode body for an energy storage device according to claim 1, and an outer casing for housing the electrode body, wherein a current collector plate is joined to the tip of the unpainted portion.

8. A method for manufacturing an electrode body for an energy storage device according to claim 1, comprising a pressing step of holding the electrode body, tilting the lower surface of a molding plate with respect to the horizontal direction, pressing and pressing down the electrode body against the unpainted portion located at the upper end of the electrode body, and rotating the electrode body around an axis along the vertical direction, wherein in the pressing step, the contact point between the unpainted portion and the molding plate is moved in a spiral manner from the outside to the inside at the upper end of the unpainted portion, and the inclination angle of the lower surface of the molding plate with respect to the horizontal plane is reduced along the trajectory of the contact point from the initial pressing to the final pressing stage.

9. A method for manufacturing an electrode body for an energy storage device according to claim 1, comprising: holding the electrode body in a holding part, rotating the electrode body around an axis in the vertical direction while moving the holding part along a horizontal linear path, and, as the holding part moves, pressing a hemispherical pressing part, which has been previously supported on the upper side of the linear path, against the unpainted part extending in the vertical direction from the outer circumference, thereby pushing the unpainted part inward in a pushing-down step, wherein in the pushing-down step, the contact point between the unpainted part and the pressing part is moved in a spiral shape from the outside to the inside at the upper end of the unpainted part.

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