Secondary battery and battery pack

Abstract

To provide a secondary battery with an excellent reliability.SOLUTION: A secondary battery comprises: an electrode winding body in which a lamination body containing a positive electrode, a negative electrode, and a separator is wound along a longitudinal direction of the lamination body, and includes a penetration hole penetrated to a width direction orthogonal to the longitudinal direction; and an outer casing that houses the electrode winding body. The positive electrode includes: a positive electrode collector that is expanded to both of the longitudinal direction and the width direction; and a positive electrode active material layer provided to the positive electrode collector. The positive electrode active material layer contains: a first thin film part, a film thickness part that has a thickness larger than a thickness of the first thin film part, and is adjacent to the first thin film part in the longitudinal direction; and a second thin film part that is positioned to the side opposite to the first thin film part in view from the film thickness part.SELECTED DRAWING: Figure 4A

Description

[Technical field]

[0001] The present disclosure relates to a secondary battery and a battery pack including the same. [Background technology]

[0002] Due to the widespread use of various electronic devices such as mobile phones, secondary batteries have been developed as power sources that are small and lightweight and can obtain high energy density. These secondary batteries have a battery element housed inside an exterior member, and various studies have been conducted on the configuration of the secondary battery (for example, see Patent Document 1).

[0003] Patent Document 1 proposes a secondary battery that employs a so-called tabless structure to reduce internal resistance and enable charging and discharging with a relatively large current. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2021 / 020237 Summary of the Invention [Problem to be solved by the invention]

[0005] Various studies have been conducted to improve the performance of secondary batteries, but there is still room for improvement in the reliability of secondary batteries.

[0006] Therefore, a highly reliable secondary battery is desired. [Means for solving the problem]

[0007] A secondary battery according to an embodiment of the present disclosure includes an electrode winding body in which a laminate including a positive electrode, a negative electrode, and a separator is wound along the longitudinal direction of the laminate, and the electrode winding body has a through hole penetrating in a width direction perpendicular to the longitudinal direction, and an outer can housing the electrode winding body. The positive electrode has a positive electrode current collector extending in both the longitudinal direction and the width direction, and a positive electrode active material layer provided on the positive electrode current collector. The positive electrode active material layer includes a first thin portion, a thick portion having a thickness greater than that of the first thin portion and adjacent to the first thin portion in the longitudinal direction, and a second thin portion located on the opposite side of the thick portion to the first thin portion. Effect of the Invention

[0008] According to the secondary battery of the embodiment of the present disclosure, the positive electrode active material layer includes a first thin portion, which can reduce stress concentration near the central axis of the electrode winding body due to expansion of the negative electrode. Furthermore, the positive electrode active material layer includes a second thin portion, which can reduce the thickness of the positive electrode active material layer at the outer peripheral end of the electrode winding body, thereby suppressing deformation of the positive electrode during expansion of the negative electrode, which is caused by a step in the positive electrode active material layer at the outer peripheral end edge of the electrode winding body. As a result, short-circuiting between the positive electrode and the negative electrode can be prevented, and excellent reliability can be ensured.

[0009] Note that the effects of the present disclosure are not necessarily limited to the effects described herein, but may be any of a series of effects related to the present disclosure described below. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view illustrating an example of a vertical cross-sectional structure of a secondary battery according to an embodiment of the present disclosure taken along a height direction. [Diagram 2] FIG. 2 is a schematic diagram showing an example of the configuration of a laminate including the positive electrode, the negative electrode, and the separator shown in FIG. [Diagram 3] FIG. 3 is a cross-sectional view showing one example of the horizontal cross-sectional structure of the electrode winding body shown in FIG. [Figure 4A] FIG. 4A is a development view of the positive electrode shown in FIG. [Figure 4B] FIG. 4B is a first cross-sectional view of the positive electrode shown in FIG. [Figure 4C] FIG. 4C is a second cross-sectional view of the positive electrode shown in FIG. [Figure 5A] FIG. 5A is a development view of the negative electrode shown in FIG. [Figure 5B] FIG. 5B is a cross-sectional view of the negative electrode shown in FIG. [Figure 6A] FIG. 6A is a plan view of the positive electrode current collector plate shown in FIG. [Figure 6B] FIG. 6B is a plan view of the negative electrode current collector plate shown in FIG. [Figure 7] FIG. 7 is a perspective view illustrating a manufacturing process of the secondary battery shown in FIG. [Figure 8] FIG. 8 is a block diagram showing a circuit configuration of a battery pack to which the secondary battery according to one embodiment of the present disclosure is applied. [Figure 9] FIG. 9 is a cross-sectional view of a positive electrode according to a first modified example of the present disclosure. [Figure 10A] FIG. 10A is a development view showing a positive electrode according to a second modified example of the present disclosure. [Figure 10B] FIG. 10B is a cross-sectional view illustrating the positive electrode shown in FIG. 10A. [Figure 11A] FIG. 11A is a development view of a positive electrode according to a third modified example of the present disclosure. [Figure 11B] FIG. 11B is an exploded view of a negative electrode used together with the positive electrode shown in FIG. 11A. [Figure 12A] FIG. 12A is a first cross-sectional view of the positive electrode shown in FIG. 11A. [Figure 12B] FIG. 12B is a second cross-sectional view of the positive electrode shown in FIG. 11A. [Figure 13A] FIG. 13A is a development view showing a positive electrode according to a fourth modified example of the present disclosure. [Figure 13B] FIG. 13B is a cross-sectional view illustrating the positive electrode shown in FIG. 13A. [Figure 14] FIG. 14 is a cross-sectional view showing a configuration example of a vertical cross-sectional structure of the secondary battery of Example 1 taken along the height direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. The description will be given in the following order. 1. Secondary battery 1-1.Configuration 1-2.Operation 1-3. Manufacturing method 1-4. Actions and Effects 2. Application Examples 2-1.Battery pack 2-2. Energy storage system 3. Variations

[0012] <1. Secondary battery> First, a secondary battery according to an embodiment of the present disclosure will be described.

[0013] In this embodiment, a cylindrical lithium ion secondary battery having a cylindrical external appearance will be described as an example. However, the secondary battery of the present disclosure is not limited to a cylindrical lithium ion secondary battery, and may be a lithium ion secondary battery having an external appearance of a shape other than a cylindrical shape, or may be a battery using an electrode reactant other than lithium.

[0014] The charge / discharge principle of the secondary battery is not particularly limited, but the following describes a case where the battery capacity is obtained by utilizing the absorption and release of the electrode reactant. This secondary battery includes a positive electrode and a negative electrode as well as an electrolyte. In this secondary battery, the charge capacity of the negative electrode is larger than the discharge capacity of the positive electrode in order to prevent the electrode reactant from being deposited on the surface of the negative electrode during charging. That is, the electrochemical capacity per unit area of ​​the negative electrode is set to be larger than the electrochemical capacity per unit area of ​​the positive electrode.

[0015] The type of the electrode reactant is not particularly limited as described above, but specifically, it is a light metal such as an alkali metal or an alkaline earth metal. The alkali metal is lithium, sodium, potassium, etc., and the alkaline earth metal is beryllium, magnesium, calcium, etc.

[0016] In the following, an example will be given in which the electrode reactant is lithium. A secondary battery that obtains battery capacity by utilizing the absorption and release of lithium is a so-called lithium ion secondary battery. In this lithium ion secondary battery, lithium is absorbed and released in an ionic state.

[0017] [1-1. Configuration] (Lithium-ion secondary battery 1) Fig. 1 shows a vertical cross-sectional configuration along the height direction of a lithium-ion secondary battery 1 (hereinafter simply referred to as secondary battery 1) according to the present embodiment. The secondary battery 1 shown in Fig. 1 includes a substantially cylindrical outer can 11 and an electrode winding body 20 as a battery element housed in the outer can 11. Furthermore, the secondary battery 1 includes an outer tube 50 that covers the outer peripheral surface of the outer can 11. In this specification, the height direction of the secondary battery 1 is defined as the Z-axis direction.

[0018] Specifically, the secondary battery 1 includes, for example, a pair of insulating plates 12, 13, an electrode winding body 20, a positive electrode current collector 24 as a first electrode current collector, and a negative electrode current collector 25 as a second electrode current collector inside an outer can 11. The electrode winding body 20 is, for example, a structure in which a positive electrode 21 and a negative electrode 22 are stacked and wound with a separator 23 interposed therebetween. The electrode winding body 20 is impregnated with an electrolytic solution that is a liquid electrolyte. The secondary battery 1 may further include, inside the outer can 11, one or more of a potent thermosensitive resistor (PTC) element and a reinforcing member.

[0019] (Outer can 11) The outer can 11 is a container that houses the positive electrode current collector 24, the negative electrode current collector 25, the electrode winding body 20, and the like. The outer can 11 has a bottom 11B and a side wall 11W. The bottom 11B is also a negative electrode terminal that is connected to the negative electrode 22 via the negative electrode current collector 25. The outer can 11 has, for example, a hollow cylindrical structure with a closed lower end in the Z-axis direction and an open upper end. Therefore, the upper end of the outer can 11 is an open end 11N, and the lower end of the outer can 11 is closed by the bottom 11B that is substantially disk-shaped. Between the open end 11N and the bottom 11B is a side wall 11W that surrounds the electrode winding body 20. The side wall 11W is erected in the height direction along the outer edge of the bottom 11B so as to surround the electrode winding body 20, and includes an open end 11N on the opposite side to the bottom 11B that is open so that the electrode winding body 20 can be inserted therethrough. The constituent material of the outer can 11 includes, for example, a metal material such as iron. However, the surface of the outer can 11 may be plated with a metal material such as nickel. The insulating plates 12 and 13 are disposed, for example, facing each other in the Z-axis direction with the electrode winding body 20 sandwiched therebetween. In this specification, in the Z-axis direction, the open end 11N and its vicinity are sometimes referred to as the upper part of the secondary battery 1, and the part where the outer can 11 is closed and its vicinity are sometimes referred to as the lower part of the secondary battery 1.

[0020] (Outer tube 50) The exterior tube 50 surrounds the side surface 11WS1 which is the outer surface of the side wall portion 11W of the exterior can 11. However, as shown in Fig. 1, the exterior tube 50 may cover the folded portion 11P (described later) at the upper end portion of the exterior can 11. The exterior tube 50 may also cover a part of the bottom surface 11BS which is the outer surface of the bottom portion 11B of the exterior can 11. The exterior tube 50 is made of a heat-shrinkable insulating film containing, for example, a polyester resin, a polyamide resin, a thermoplastic elastomer resin, or the like.

[0021] (Washer 55) A washer 55 is provided in the gap between the exterior tube 50 and the bent portion 11P of the exterior can 11. The washer 55 is an insulating ring member having an opening 55K in a central region in a plane perpendicular to the height direction. A protrusion 14T in the central region of the battery lid 14 is inserted into the opening 55K. The washer 55 may be made of, for example, black modified polyphenylene ether.

[0022] (Insulating plates 12, 13) Each of the insulating plates 12 and 13 is, for example, a dish-shaped plate having a surface perpendicular to the central axis CL of the wound electrode body 20, i.e., a surface perpendicular to the Z-axis in Fig. 1. The insulating plates 12 and 13 are arranged to sandwich the wound electrode body 20 therebetween.

[0023] (Crimped structure 11R) At the open end 11N of the exterior can 11, for example, a structure in which the battery lid 14 and the safety valve mechanism 30 are crimped via a gasket 15, i.e., a crimped structure 11R, is formed. The exterior can 11 is sealed by the battery lid 14 with the electrode wound body 20 and the like housed inside the exterior can 11. The crimped structure 11R is a so-called crimp structure, and has a bent portion 11P as a so-called crimp portion.

[0024] (Battery cover 14) The battery lid 14 is mainly a closing member that closes the open end 11N when the electrode winding body 20 and the like are housed inside the exterior can 11. The battery lid 14 is, for example, a conductor containing the same material as the material forming the exterior can 11. The battery lid 14 closes the open end 11N of the exterior can 11 and is connected to the positive electrode current collector 24. Therefore, the battery lid 14 is also a positive electrode terminal that is connected to the positive electrode 21 via the positive electrode current collector 24. The central region of the battery lid 14 protrudes upward (in the +Z direction), for example. As a result, the peripheral region of the battery lid 14 other than the central region is in contact with, for example, the safety valve mechanism 30.

[0025] (Gasket 15) The gasket 15 is a sealing member that is mainly interposed between the folded portion 11P of the outer can 11 and the battery lid 14. The gasket 15 seals the gap between the folded portion 11P and the battery lid 14. However, the surface of the gasket 15 may be coated with, for example, asphalt. The gasket 15 contains, for example, one or more types of insulating materials. The type of insulating material is not particularly limited, but is, for example, a polymer material such as polybutylene terephthalate (PBT) and polypropylene (PP). Among them, the insulating material is preferably polybutylene terephthalate. This is because the gap between the folded portion 11P and the battery lid 14 is sufficiently sealed while electrically isolating the outer can 11 and the battery lid 14 from each other.

[0026] (Safety valve mechanism 30) The safety valve mechanism 30 is mainly configured to release the internal pressure by releasing the sealed state of the outer can 11 as necessary when the pressure inside the outer can 11 (internal pressure) increases. The internal pressure of the outer can 11 increases due to, for example, gas generated due to a decomposition reaction of the electrolyte during charging and discharging. The internal pressure of the outer can 11 may also increase due to heating from the outside.

[0027] (Electrode winding body 20) The electrode winding body 20 is disposed between a positive electrode current collector 24 and a negative electrode current collector 25. The electrode winding body 20 has an upper end face 41 facing the positive electrode current collector 24 in the height direction, and a lower end face 42 facing the negative electrode current collector 25 in the height direction. The electrode winding body 20 is a power generating element that causes charge / discharge reactions to proceed, and is housed inside the exterior can 11. The electrode winding body 20 includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolytic solution that is a liquid electrolyte.

[0028] FIG. 2 is a development view of the electrode winding body 20, and is a schematic representation of a part of the laminate S20 including the positive electrode 21 as the first electrode, the negative electrode 22 as the second electrode, and the separator 23. In the laminate S20 obtained by developing the electrode winding body 20, the positive electrode 21 and the negative electrode 22 are laminated with the separator 23 interposed therebetween. The separator 23 has, for example, two base materials, that is, the first separator member 23A and the second separator member 23B. Therefore, the electrode winding body 20 has a four-layer laminate S20 in which the positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are laminated in this order. The positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are all substantially strip-shaped members with the W direction as the short side direction and the L direction as the long side direction.

[0029] As shown in FIG. 3, the electrode winding body 20 is formed by winding the laminate S20 around a through hole 26 along a central axis CL extending in the Z-axis direction so as to form a spiral shape in a horizontal cross section perpendicular to the Z-axis direction. At this time, the laminate S20 is wound in a position in which the W direction is approximately aligned with the Z-axis direction. Note that FIG. 3 shows an example of a configuration along a horizontal cross section perpendicular to the Z-axis direction in the electrode winding body 20. However, in FIG. 3, the separator 23 is omitted in order to improve visibility. The electrode winding body 20 has an approximately cylindrical appearance as a whole. The positive electrode 21 and the negative electrode 22 are wound while maintaining a state in which they face each other via the separator 23. A through hole 26 is formed as an internal space at the center of the electrode winding body 20. The through hole 26 is a hole for inserting a winding core for assembling the electrode winding body 20 and an electrode rod for welding. The through hole extends in the Z-axis direction along the central axis CL, and penetrates the electrode winding body 20. Therefore, the laminate S20 is wound around the through hole .

[0030] The positive electrode 21, the negative electrode 22, and the separator 23 are wound so that the separator 23 is disposed at the outermost circumference and the innermost circumference of the electrode winding body 20. In addition, the negative electrode 22 is disposed outside the positive electrode 21 at the outermost circumference of the electrode winding body 20. That is, as shown in FIG. 3, the positive electrode outermost circumference part 21out located at the outermost circumference of the positive electrode 21 included in the electrode winding body 20 is disposed inside the negative electrode outermost circumference part 22out located at the outermost circumference of the negative electrode 22 included in the electrode winding body 20. Here, the positive electrode outermost circumference part 21out is the outermost one-turn part of the positive electrode 21 in the electrode winding body 20. The negative electrode outermost circumference part 22out is the outermost one-turn part of the negative electrode 22 in the electrode winding body 20. On the other hand, the negative electrode 22 is disposed inside the positive electrode 21 at the innermost circumference of the electrode winding body 20. That is, as shown in Fig. 3, the negative electrode innermost circumferential portion 22in located at the innermost periphery of the negative electrode 22 included in the electrode winding body 20 is located inside the positive electrode innermost circumferential portion 21in located at the innermost periphery of the positive electrode 21 included in the electrode winding body 20. Here, the positive electrode innermost circumferential portion 21in is the innermost one-turn portion of the positive electrode 21 in the electrode winding body 20. The negative electrode innermost circumferential portion 22in is the innermost one-turn portion of the negative electrode 22 in the electrode winding body 20. The number of turns of each of the positive electrode 21, the negative electrode 22, and the separator 23 is not particularly limited and can be set arbitrarily.

[0031] FIG. 4A is a development view of the positive electrode 21, and is a schematic representation of the state before winding. Each of FIG. 4B and FIG. 4C shows a cross-sectional configuration of the positive electrode 21. However, FIG. 4B shows a cross-section in the direction of the arrow along the line IVB-IVB shown in FIG. 4A. FIG. 4C shows a cross-section in the direction of the arrow along the line IVC-IVC shown in FIG. 4A. The positive electrode 21 has a positive electrode collector 21A, a positive electrode active material layer 21B, and an insulating layer 101. The positive electrode active material layer 21B may be provided, for example, on only one side of the positive electrode collector 21A, or on both sides of the positive electrode collector 21A. FIG. 4B shows a case where the positive electrode active material layer 21B is provided on both sides of the positive electrode collector 21A. More specifically, the positive electrode current collector 21A includes a positive electrode current collector inner peripheral surface 21A1 facing the central axis CL and a positive electrode current collector outer peripheral surface 21A2 opposite to the positive electrode current collector inner peripheral surface 21A1. The positive electrode 21 has, as the positive electrode active material layer 21B, a positive electrode inner peripheral side active material layer 21B1 covering at least a part of the positive electrode current collector inner peripheral surface 21A1 and a positive electrode outer peripheral side active material layer 21B2 covering at least a part of the positive electrode current collector outer peripheral surface 21A2. In this specification, the positive electrode inner peripheral side active material layer 21B1 and the positive electrode outer peripheral side active material layer 21B2 may be collectively referred to as the positive electrode active material layer 21B without distinguishing between them. The positive electrode active material layer 21B extends in both the L direction and the W direction perpendicular to the L direction. The L direction is the winding direction of the laminate S20. The W direction substantially coincides with the central axis CL.

[0032] The positive electrode current collector 21A includes a positive electrode covering region 211 covered by the positive electrode active material layer 21B, and a positive electrode exposed region 212 extending in the W direction without being covered by the positive electrode active material layer 21B. The insulating layer 101 extends in the L direction along a first edge 21BT1 of the positive electrode active material layer 21B located at a boundary K between the positive electrode covering region 211 and the positive electrode exposed region 212. In the positive electrode 21 of this embodiment, as shown in FIG. 4B, the first edge 21BT1 of the positive electrode active material layer 21B is an inclined surface, and the insulating layer 101 is in contact with the first edge 21BT1. That is, the insulating layer 101 is formed so as to cover the vicinity of the first edge 21BT1 of the positive electrode active material layer 21B. The positive electrode active material layer 21B includes thin portions 61 and 62 and thick portions 71 to 73. In the positive electrode 21 of the present embodiment, the thin portions 61, 62 and the thick portions 71-73 are formed on both the positive electrode current collector inner peripheral surface 21A1 and the positive electrode current collector outer peripheral surface 21A2. That is, both the positive electrode inner peripheral side active material layer 21B1 and the positive electrode outer peripheral side active material layer 21B2 each include the thin portions 61, 62 and the thick portions 71-73. However, in the positive electrode 21, it is sufficient that at least one of the positive electrode inner peripheral side active material layer 21B1 and the positive electrode outer peripheral side active material layer 21B2 includes the thin portions 61, 62 and the thick portions 71-73. In addition, in Fig. 4B and Fig. 4C, the thin parts 61, 62 and the thick parts 71, 72, 73 constituting the positive electrode inner periphery side active material layer 21B1 are described as thin parts 61-1, 62-1 and thick parts 71-1, 72-1, 73-1, respectively, for convenience, and the thin parts 61, 62 and the thick parts 71, 72, 73 constituting the positive electrode outer periphery side active material layer 21B2 are described as thin parts 61-2, 62-2 and thick parts 71-2, 72-2, 73-2, respectively, for convenience. In the example shown in Fig. 4C, the position in the L direction of the boundary 21B1K1 between the thin part 61-1 and the thick part 73-1 substantially coincides with the position in the L direction of the boundary 21B2K1 between the thin part 61-2 and the thick part 73-2. Furthermore, the position in the L direction of a boundary 21B1K2 between the thin portion 62-1 and the thick portion 73-1 substantially coincides with the position in the L direction of a boundary 21B2K2 between the thin portion 62-2 and the thick portion 73-2.

[0033] Each of the thick portions 71 to 73 has a thickness larger than that of the thin portions 61 and 62. The thickness of the thin portions 61 and 62 can be, for example, about half the thickness of each of the thick portions 71 to 73. The thicknesses of the thick portions 71 to 73 may be the same as each other or different from each other. In detail, as shown in FIG. 4B and FIG. 4C, in the positive electrode inner periphery side active material layer 21B1, the thickness T71-1 of the thick portion 71-1, the thickness T72-1 of the thick portion 72-1, and the thickness T73-1 of the thick portion 73-1 are larger than the thickness T61-1 of the thin portion 61-1 and the thickness T62-1 of the thin portion 62-1. In the example shown in FIG. 4B and FIG. 4C, the thickness T71-1 of the thick portion 71-1, the thickness T72-1 of the thick portion 72-1, and the thickness T73-1 of the thick portion 73-1 are equal to each other. Similarly, in the positive-electrode outer peripheral side active material layer 21B2, the thickness T71-2 of the thick portion 71-2, the thickness T72-2 of the thick portion 72-2, and the thickness T73-2 of the thick portion 73-2 are larger than the thickness T61-2 of the thin portion 61-2 and the thickness T62-2 of the thin portion 62-2. In the example shown in FIG. 4B and FIG. 4C, the thickness T71-2 of the thick portion 71-2, the thickness T72-2 of the thick portion 72-2, and the thickness T73-2 of the thick portion 73-2 are equal to each other. The thickness T61-1 and the thickness T61-2 may be equal to each other or may be different from each other. Furthermore, the thicknesses T71-1, T72-1, and T73-1 may be equal to or different from the thicknesses T71-2, T72-2, and T73-2, respectively.

[0034] The thin portion 61 includes the edge 21E1 of the positive electrode 21 on the winding center side in the L direction. The length of the thin portion 61 in the L direction may be, for example, about 1 to 5 revolutions of the electrode winding body 20 starting from the edge 21E1 on the winding center side. The thick portion 71 is adjacent to the thin portion 61 in the W direction. More specifically, the thick portion 71 is located between the thin portion 61 and the insulating layer 101 in the W direction. The thick portion 71 includes the first edge 21BT1 and may be in contact with the insulating layer 101. The thick portion 72 includes the second edge 21BT2 located on the opposite side to the first edge 21BT1 in the W direction. The thick portion 73 is provided on the opposite side to the edge 21E1 on the winding center side as viewed from the thin portion 61 in the L direction.

[0035] The thin portion 62 is provided on the opposite side of the thin portion 61 from the thick portion 73. The thin portion 62 includes the outer peripheral winding edge 21E2 in the L direction of the positive electrode 21. The length of the thin portion 62 in the L direction may be, for example, about 1 / 2 circumference of the electrode wound body 20 starting from the outer peripheral winding edge 21E2. The positive electrode active material layer 21B further includes a thick portion 74 adjacent to the thin portion 62 in the W direction. More specifically, the thick portion 74 is located between the thin portion 62 and the insulating layer 101 in the W direction. The thick portion 74 includes the first edge 21BT1 and may be in contact with the insulating layer 101. The positive electrode active material layer 21B further includes a thick portion 75. The thick portion 75 includes the second edge 21BT2. The thick portions 71 to 75 may be separated from one another, or may be partially or entirely integrated.

[0036] As shown in FIG. 4A, the positive electrode covering region 211 and the positive electrode exposed region 212 each extend along the L direction from the winding center side edge 21E1 of the positive electrode 21 to the winding outer peripheral side edge 21E2. That is, in the positive electrode 21, the positive electrode active material layer 21B covers the positive electrode current collector 21A from the winding center side edge 21E1 of the positive electrode 21 to the winding outer peripheral side edge 21E2 of the positive electrode 21 in the winding direction of the electrode winding body 20. The positive electrode covering region 211 and the positive electrode exposed region 212 are adjacent to each other in the W direction, which is the short side direction of the positive electrode 21. Note that FIG. 4A and FIG. 4B show the positive electrode current collector 21A in a state of being extended linearly along the W direction. However, in reality, the positive electrode edge portion 212E of the positive electrode exposed region 212 is bent toward the central axis CL as shown in FIG. 1 and connected to the positive electrode current collector plate 24. That is, the end of the positive electrode exposed region 212 in the W direction constitutes an upper end surface 41 and is connected to the positive electrode current collector plate 24 (see FIG. 1). The upper end surface 41 is formed by bending the positive electrode edge portion 212E of the positive electrode exposed region 212 toward the through hole 26 in a rolled state.

[0037] An insulating layer 101 may be provided near the boundary between the positive electrode covering region 211 and the positive electrode exposed region 212. The insulating layer 101 may extend from the winding center side edge 21E1 to the winding outer periphery side edge 21E2 of the electrode winding body 20, similar to the positive electrode covering region 211 and the positive electrode exposed region 212. The insulating layer 101 may be bonded to at least one of the first separator member 23A and the second separator member 23B. This is because it is possible to prevent the occurrence of misalignment between the positive electrode 21 and the separator 23. The insulating layer 101 may include a resin containing polyvinylidene fluoride (PVDF). By containing PVDF, the insulating layer 101 may swell due to a solvent contained in the electrolyte, for example, and may be well bonded to the separator 23.

[0038] FIG. 5A is a development view of the negative electrode 22, and is a schematic representation of the state before winding. FIG. 5B shows a cross-sectional configuration of the negative electrode 22. Note that FIG. 5B shows a cross section in the direction of the arrows along the line VB-VB shown in FIG. 5A. The negative electrode 22 includes, for example, a negative electrode collector 22A as a second electrode collector, and a negative electrode active material layer 22B that covers a part of the negative electrode collector 22A. The negative electrode active material layer 22B may be provided, for example, on only one side of the negative electrode collector 22A, or on both sides of the negative electrode collector 22A. FIG. 5B shows a case where the negative electrode active material layer 22B is provided on both sides of the negative electrode collector 22A. More specifically, the negative electrode current collector 22A includes a negative electrode current collector inner peripheral surface 22A1 facing the central axis CL and a negative electrode current collector outer peripheral surface 22A2 opposite to the negative electrode current collector inner peripheral surface 22A1. The negative electrode 22 has, as the negative electrode active material layer 22B, a negative electrode inner peripheral side active material layer 22B1 covering at least a part of the negative electrode current collector inner peripheral surface 22A1 and a negative electrode outer peripheral side active material layer 22B2 covering at least a part of the negative electrode current collector outer peripheral surface 22A2. In this specification, the negative electrode inner peripheral side active material layer 22B1 and the negative electrode outer peripheral side active material layer 22B2 may be collectively referred to as the negative electrode active material layer 22B without distinguishing between them.

[0039] The negative electrode 22 has a negative electrode covering region 221 in which the negative electrode collector 22A is covered with the negative electrode active material layer 22B, and a negative electrode exposed region 222 in which the negative electrode collector 22A is exposed without being covered with the negative electrode active material layer 22B. As shown in FIG. 5A, the negative electrode covering region 221 and the negative electrode exposed region 222 each extend along the L direction, which is the longitudinal direction of the negative electrode 22. The negative electrode exposed region 222 extends from the winding center side edge 22E1 to the winding outer periphery side edge 22E2 of the negative electrode 22 in the winding direction of the electrode winding body 20. In contrast, the negative electrode covering region 221 is not provided on the winding center side edge 22E1 and the winding outer periphery side edge 22E2 of the negative electrode 22. As shown in FIG. 5A, a part of the negative electrode exposed region 222 is formed so as to sandwich the negative electrode covering region 221 in the L direction. Specifically, the negative electrode exposed region 222 includes a first portion 222A, a second portion 222B, and a third portion 222C. The negative electrode 22 further has a lower edge 22E3 extending in the L direction at the lower side of the electrode winding body 20. The first portion 222A is provided adjacent to the negative electrode covered region 221 in the W direction, and extends in the L axis direction from the winding center side edge 22E1 to the winding outer periphery side edge 22E2 of the negative electrode 22. That is, the first portion 222A is a region extending in the W direction from the negative electrode active material layer 22B. The second portion 222B and the third portion 222C are provided so as to sandwich the negative electrode covering region 221 in the L direction. The first portion 222A is located near the lower end edge 22E3 of the negative electrode 22. The second portion 222B is located, for example, near the winding center side end edge 22E1 of the negative electrode 22, and the third portion 222C is located near the winding outer periphery side end edge 22E2 of the negative electrode 22. Note that in FIG. 5A and FIG. 5B, the negative electrode current collector 22A is illustrated in a state of being extended linearly along the W direction in a schematic manner. However, in reality, the negative electrode edge portion 222E of the negative electrode exposed region 222 is bent toward the central axis CL as shown in FIG. 1, and is connected to the negative electrode current collector 25. That is, the end portion in the W direction of the negative electrode exposed region 222 constitutes the lower end surface 42 and is connected to the negative electrode current collector 25 (see FIG. 1). The lower end surface 42 is formed by bending the negative electrode edge portion 222E of the negative electrode exposed region 222 toward the through-hole 26 in a wound state.

[0040] In the laminate S20 of the electrode winding body 20, the positive electrode 21 and the negative electrode 22 are laminated via the separator 23 so that the positive electrode exposed region 212 and the first portion 222A of the negative electrode exposed region 222 are oriented opposite to each other along the width direction W. The electrode winding body 20 has an end portion of the separator 23 fixed by attaching a fixing tape 46 to a side surface portion 45 thereof, thereby preventing loosening of the winding.

[0041] In the secondary battery 1, as shown in FIG. 2, when the width of the positive electrode exposed region 212 is A and the width of the first portion 222A of the negative electrode exposed region 222 is B, it is preferable that A>B. For example, when the width A=7 (mm), the width B=4 (mm). In addition, when the width of the portion of the positive electrode exposed region 212 that protrudes from the outer edge of the separator 23 in the width direction is C, and the length of the portion of the first portion 222A of the negative electrode exposed region 222 that protrudes from the outer edge of the opposite side in the width direction of the separator 23 is D, it is preferable that C>D. For example, when the width C=4.5 (mm), the width D=3 (mm).

[0042] As shown in Fig. 1, in the upper part of the secondary battery 1, a plurality of adjacent positive electrode edges 212E in the radial direction (R direction) of the electrode winding body 20 in the positive electrode exposed region 212 wound around the central axis CL are bent toward the central axis CL so as to overlap with each other, forming an upper end surface 41 of the electrode winding body 20. Similarly, in the lower part of the secondary battery 1, a plurality of adjacent negative electrode edges 222E in the radial direction (R direction) in the negative electrode exposed region 222 wound around the central axis CL are bent toward the central axis CL so as to overlap with each other, forming a lower end surface 42 of the electrode winding body 20. Therefore, a plurality of positive electrode edges 212E of the positive electrode exposed region 212 are gathered at the upper end surface 41 of the electrode winding body 20, and a plurality of negative electrode edges 222E of the negative electrode exposed region 222 are gathered at the lower end surface 42 of the electrode winding body 20. In order to improve the contact between the positive electrode current collector 24 for extracting the current and the positive electrode edge 212E, the multiple positive electrode edges 212E bent toward the central axis CL are flat. Similarly, in order to improve the contact between the negative electrode current collector 25 for extracting the current and the negative electrode edge 222E, the multiple negative electrode edges 222E bent toward the central axis CL are flat. The flat surface here includes not only a completely flat surface, but also a surface having some unevenness or surface roughness to the extent that the positive electrode exposed region 212 and the negative electrode exposed region 222 can be joined to the positive electrode current collector 24 and the negative electrode current collector 25, respectively.

[0043] The positive electrode current collector 21A is made of, for example, aluminum foil, as described later. On the other hand, the negative electrode current collector 22A is made of, for example, copper foil, as described later. In this case, the positive electrode current collector 21A is softer than the negative electrode current collector 22A. That is, the Young's modulus of the positive electrode exposed region 212 is lower than that of the negative electrode exposed region 222. For this reason, in one embodiment, it is more preferable that the widths A to D have a relationship of A>B and C>D. In that case, when the positive electrode exposed region 212 and the negative electrode exposed region 222 are folded simultaneously from both electrode sides with the same pressure, the heights measured from the tip of the separator 23 at the folded parts may be approximately the same for the positive electrode 21 and the negative electrode 22. At this time, the multiple positive electrode edges 212E (FIG. 1) of the positive electrode exposed region 212 are folded and overlap appropriately. Therefore, the positive electrode exposed region 212 and the positive electrode current collector 24 can be easily joined. Similarly, the negative electrode edges 222E (FIG. 1) of the negative electrode exposed region 222 are folded and overlap each other to a suitable degree. This facilitates joining of the negative electrode exposed region 222 and the negative electrode current collector plate 25. The joining here means joining them together by, for example, laser welding, but the joining method is not limited to laser welding.

[0044] As shown in FIG. 2, the portion of the positive electrode exposed region 212 of the positive electrode 21 facing the negative electrode 22 with the separator 23 interposed therebetween is covered with the insulating layer 101. The insulating layer 101 has a width of, for example, 3 mm in the W direction. The insulating layer 101 covers the entire region of the positive electrode exposed region 212 of the positive electrode 21 facing the negative electrode covering region 221 of the negative electrode 22 via the separator 23. The insulating layer 101 can effectively prevent an internal short circuit of the secondary battery 1 when, for example, a foreign object enters between the negative electrode covering region 221 and the positive electrode exposed region 212. In addition, when an impact is applied to the secondary battery 1, the insulating layer 101 can absorb the impact and effectively prevent bending of the positive electrode exposed region 212 and short circuit between the positive electrode exposed region 212 and the negative electrode 22.

[0045] (Insulating tape 53, 54) The secondary battery 1 may further have insulating tapes 53, 54 in the gap between the exterior can 11 and the electrode winding body 20. The positive electrode exposed area 212 and the negative electrode exposed area 222 gathered at the upper end face 41 and the lower end face 42 are conductors such as bare metal foil. Therefore, if the positive electrode exposed area 212 and the negative electrode exposed area 222 are close to the exterior can 11, a short circuit may occur between the positive electrode 21 and the negative electrode 22 through the exterior can 11. In addition, when the positive electrode current collector 24 at the upper end face 41 and the exterior can 11 are close to each other, a short circuit may occur. For this reason, it is preferable that insulating tapes 53, 54 are provided as insulating members. The insulating tapes 53, 54 are, for example, adhesive tapes whose base layer is made of any one of polypropylene, polyethylene terephthalate, and polyimide, and whose base layer has an adhesive layer on one side. In order to prevent the installation of the insulating tapes 53, 54 from reducing the volume of the electrode winding body 20, the insulating tapes 53, 54 are positioned so as not to overlap with the fixing tape 46 attached to the side portion 45, and the thickness of the insulating tapes 53, 54 is set to be equal to or less than the thickness of the fixing tape 46.

[0046] (Positive electrode current collector 24 and negative electrode current collector 25) In a normal lithium ion secondary battery, for example, a lead for current extraction is welded to each of the positive and negative electrodes. However, this is not suitable for high-rate discharge because the internal resistance of the lithium ion secondary battery is large and the lithium ion secondary battery heats up and becomes hot during discharge. Therefore, in the secondary battery 1 of this embodiment, the positive electrode current collector 24 is arranged to face the upper end face 41, and the negative electrode current collector 25 is arranged to face the lower end face 42, and the positive electrode covering region 211 present on the upper end face 41 and the positive electrode current collector 24 are welded at multiple points, and the negative electrode covering region 221 present on the lower end face 42 and the negative electrode current collector 25 are welded at multiple points. In this way, the internal resistance of the secondary battery 1 is reduced. The fact that the upper end face 41 and the lower end face 42 are flat as described above also contributes to the reduction in resistance. The positive electrode current collector 24 is provided between the battery cover 14 and the upper end face 41. The positive electrode current collector 24 is electrically connected to the battery cover 14 via, for example, a safety valve mechanism 30. The negative electrode current collector 25 is provided between the bottom 11B and the lower end surface 42 of the outer can 11. The negative electrode current collector 25 is electrically connected to, for example, the inner surface of the bottom 11B of the outer can 11. FIG. 6A is a development showing an example of the configuration of the positive electrode current collector 24. FIG. 6B is a development showing an example of the configuration of the negative electrode current collector 25. The positive electrode current collector 24 is a metal plate made of, for example, aluminum or an aluminum alloy, or a composite material thereof. The negative electrode current collector 25 is a metal plate made of, for example, nickel, a nickel alloy, copper, or a copper alloy, or a composite material of two or more of these.

[0047] As shown in FIG. 6A, the positive electrode current collector 24 has a sector-shaped portion 31 having a substantially sector shape and a strip-shaped portion 32 having a substantially rectangular shape. However, the shape of the positive electrode current collector 24 is not limited to the shape shown in FIG. 6A and can be arbitrarily selected. In the secondary battery 1, the positive electrode current collector 24 is housed in the exterior can 11 in a state in which the strip-shaped portion 32 is folded with respect to the sector-shaped portion 31 as shown in FIG. 1. FIG. 6A shows the positive electrode current collector 24 in an unfolded state. The sector-shaped portion 31 is a facing portion that faces and is connected to the upper end surface 41. The sector-shaped portion 31 has an outer edge that includes, for example, a straight portion and a curved portion. An opening 35 is formed near the center of the sector-shaped portion 31. FIG. 6A illustrates a case in which the opening 35 has a circular planar shape in a horizontal plane perpendicular to the Z-axis direction. The strip-shaped portion 32 is connected to, for example, a straight portion of the outer edge of the sector-shaped portion 31. The strip portion 32 extends in a direction intersecting with the straight portion 31S of the sector portion 31. As shown in Fig. 1, in the secondary battery 1, the positive electrode current collector plate 24 is provided so that the opening 35 overlaps with the through hole 26 in the Z-axis direction. That is, the opening 35 is provided at a position where it overlaps with a part of the upper end surface 41 on the winding center side in the Z-axis direction.

[0048] The hatched portion in FIG. 6A is the insulating portion 32A of the strip-shaped portion 32. The insulating portion 32A is a part of the strip-shaped portion 32 to which an insulating tape is attached or an insulating material is applied. The lower part of the strip-shaped portion 32A is a connection portion 32B to the sealing plate, which also serves as an external terminal. The sealing plate is electrically connected to the battery cover 14. As shown in FIG. 1, when the secondary battery 1 has a battery structure in which the through hole 26 does not have a metal center pin, the strip-shaped portion 32 is less likely to come into contact with a portion of the negative electrode potential. Therefore, the positive electrode current collector 24 does not need to have the insulating portion 32A. When the positive electrode current collector 24 does not have the insulating portion 32A, the charge / discharge capacity can be increased by widening the width between the positive electrode 21 and the negative electrode 22 by an amount equivalent to the thickness of the insulating portion 32A.

[0049] The shape of the negative electrode current collector 25 shown in FIG. 6B is almost the same as the shape of the positive electrode current collector 24 shown in FIG. 6A. The negative electrode current collector 25 has a sector-shaped portion 33 having a substantially sector shape and a strip-shaped portion 34 having a substantially rectangular shape. However, the shape of the negative electrode current collector 25 is not limited to the shape shown in FIG. 6B and can be arbitrarily selected. In the secondary battery 1, the negative electrode current collector 25 is accommodated in the exterior can 11 in a state in which the strip-shaped portion 34 is folded with respect to the sector-shaped portion 33 as shown in FIG. 1. FIG. 6B shows the negative electrode current collector 25 in an unfolded state. The sector-shaped portion 33 is a facing portion that faces and is connected to the lower end surface 42. The sector-shaped portion 33 has an outer edge that includes, for example, a straight portion and a curved portion. The strip-shaped portion 34 is connected to, for example, a straight portion 33S of the outer edge of the sector-shaped portion 33. The strip-shaped portion 34 extends in a direction that intersects with the straight portion of the sector-shaped portion 33. The strip portion 34 of the negative current collector 25 is shorter than the strip portion 32 of the positive current collector 24, and does not have a portion corresponding to the insulating portion 32A of the positive current collector 24. The strip portion 34 is provided with a plurality of circular protrusions 37 indicated by circles. At least some of the plurality of protrusions 37 are welded to the bottom 11B of the outer can 11. During resistance welding, a current is concentrated on the protrusions 37, which melt the protrusions 37 and weld the strip portion 34 to the bottom 11B of the outer can 11. As with the positive current collector 24, the negative current collector 25 has an opening 36 formed near the center of the sector portion 33. In the secondary battery 1, the negative current collector 25 is provided such that the opening 36 overlaps with the through hole 26 in the Z-axis direction. FIG. 6B illustrates a case in which the opening 36 has a circular planar shape in a horizontal plane perpendicular to the Z-axis direction.

[0050] The sector-shaped portion 31 of the positive electrode current collector 24 covers only a part of the upper end surface 41 due to its planar shape. Similarly, the sector-shaped portion 33 of the negative electrode current collector 25 covers only a part of the lower end surface 42 due to its planar shape. There are two reasons why the sector-shaped portion 31 and the sector-shaped portion 33 do not cover the entire upper end surface 41 and the lower end surface 42. The first reason is, for example, to allow the electrolyte to smoothly penetrate into the electrode winding body 20 when assembling the secondary battery 1. In particular, in the secondary battery 1 of this embodiment, the positive electrode current collector 24 is provided so that the opening 35 is positioned so as to overlap a part of the upper end surface 41 on the winding center side in the Z-axis direction. Therefore, a part of the positive electrode edge portion 212E constituting the upper end surface 41 is not covered by the sector-shaped portion 31 of the positive electrode current collector 24 and is exposed to the opening 35. Therefore, the secondary battery 1 has a structure in which the electrolyte penetrates into the electrode winding body 20 more quickly. The second reason is to facilitate the release to the outside of gas that is generated when the lithium-ion secondary battery is subjected to an abnormally high temperature or is overcharged.

[0051] (Positive electrode current collector 21A) The positive electrode current collector 21A includes a conductive material such as aluminum, etc. The positive electrode current collector 21A is, for example, a metal foil made of aluminum or an aluminum alloy.

[0052] (Positive electrode active material layer 21B) The positive electrode active material layer 21B contains, as a positive electrode active material, any one or more of positive electrode materials capable of absorbing and releasing lithium. However, the positive electrode active material layer 21B may further contain any one or more of other materials such as a positive electrode binder and a positive electrode conductor. The positive electrode material is preferably a lithium-containing compound, more specifically, a lithium-containing composite oxide and a lithium-containing phosphate compound. The lithium-containing composite oxide is an oxide containing lithium and one or more other elements, i.e., elements other than lithium, as constituent elements. The lithium-containing composite oxide has, for example, any one of a layered rock salt type and a spinel type crystal structure. The lithium-containing phosphate compound is a phosphate compound containing lithium and one or more other elements as constituent elements, and has, for example, an olivine type crystal structure. The positive electrode active material layer 21B may contain, in particular, at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide as a positive electrode active material. The positive electrode binder contains, for example, one or more of synthetic rubber and polymer compounds. The synthetic rubber is, for example, styrene butadiene rubber, fluorine rubber, and ethylene propylene diene. The polymer compound is, for example, polyvinylidene fluoride and polyimide. The positive electrode conductive agent contains, for example, one or more of carbon materials. The carbon materials are, for example, graphite, carbon black, acetylene black, and ketjen black. However, the positive electrode conductive agent may be a metal material, a conductive polymer, or the like, as long as it is a material having conductivity.

[0053] (Negative electrode current collector 22A) The negative electrode collector 22A includes a conductive material such as copper. The negative electrode collector 22A is a metal foil made of nickel, a nickel alloy, copper, or a copper alloy. The surface of the negative electrode collector 22A is preferably roughened. This is because the adhesion of the negative electrode active material layer 22B to the negative electrode collector 22A is improved by a so-called anchor effect. In this case, it is sufficient that the surface of the negative electrode collector 22A is roughened at least in the region facing the negative electrode active material layer 22B. The roughening method is, for example, a method of forming fine particles using an electrolytic process. In the electrolytic process, fine particles are formed on the surface of the negative electrode collector 22A by an electrolytic method in an electrolytic bath, so that the surface of the negative electrode collector 22A is provided with irregularities. Copper foil produced by an electrolytic method is generally called electrolytic copper foil.

[0054] (Negative electrode active material layer 22B) The negative electrode active material layer 22B contains, as the negative electrode active material, any one or more of negative electrode materials capable of absorbing and releasing lithium. However, the negative electrode active material layer 22B may further contain any one or more of other materials such as a negative electrode binder and a negative electrode conductor. The negative electrode material is, for example, a carbon material. This is because a high energy density can be stably obtained since the change in the crystal structure during the absorption and release of lithium is very small. In addition, since the carbon material also functions as a negative electrode conductor, the conductivity of the negative electrode active material layer 22B is improved. The carbon material is, for example, graphitizable carbon, non-graphitizable carbon, graphite, etc. However, the plane spacing of the (002) plane in the non-graphitizable carbon is preferably 0.37 nm or more. The plane spacing of the (002) plane in graphite is preferably 0.34 nm or less. More specifically, the carbon material is, for example, pyrolytic carbon, cokes, glassy carbon fiber, organic polymer compound calcined body, activated carbon, and carbon black. The cokes include pitch coke, needle coke, and petroleum coke. The organic polymer compound calcined body is a product of calcining (carbonizing) a polymer compound such as a phenolic resin and a furan resin at an appropriate temperature. In addition, the carbon material may be low-crystalline carbon heat-treated at a temperature of about 1000°C or less, or amorphous carbon. The shape of the carbon material may be any of fibrous, spherical, granular, and scaly. In the secondary battery 1, when the open circuit voltage at the time of full charge, i.e., the battery voltage, is 4.25V or more, the amount of lithium released per unit mass is greater even if the same positive electrode active material is used, compared to when the open circuit voltage at the time of full charge is 4.20V. For this reason, the amounts of the positive electrode active material and the negative electrode active material are adjusted accordingly. This allows a high energy density to be obtained.

[0055] Further, the negative electrode active material layer 22B may contain, as a negative electrode active material, a silicon-containing material containing at least one of silicon, silicon oxide, carbon-silicon compound, and silicon alloy. The silicon-containing material is a general term for materials containing silicon as a constituent element. However, the silicon-containing material may contain only silicon as a constituent element. Note that the type of the silicon-containing material may be only one type or two or more types. The silicon-containing material can form an alloy with lithium, and may be a single substance of silicon, an alloy of silicon, a compound of silicon, a mixture of two or more of them, or a material containing one or two or more phases of them. Further, the silicon-containing material may be crystalline, amorphous, or may contain both a crystalline part and an amorphous part. However, since the single substance described here means a general single substance, it may contain a trace amount of impurities. That is, the purity of the single substance is not necessarily limited to 100%. The alloy of silicon contains, for example, any one or two or more of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium as constituent elements other than silicon. The compound of silicon contains, for example, any one or two or more of carbon and oxygen as constituent elements other than silicon. Note that the compound of silicon may contain any one or two or more of a series of constituent elements described for the alloy of silicon as a constituent element other than silicon. Specifically, the alloy of silicon and the compound of silicon are, for example, SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, and SiO v (0 < v ≤ 2) and the like. However, the range of v can be arbitrarily set, for example, 0.2 < v < 1.4 may also be possible.

[0056] (Separator 23) The separator 23 is interposed between the positive electrode 21 and the negative electrode 22. The separator 23 allows lithium ions to pass while preventing a short circuit of current caused by contact between the positive electrode 21 and the negative electrode 22. The separator 23 is, for example, one or more types of porous membranes such as synthetic resins and ceramics, and may be a laminated membrane of two or more types of porous membranes. The synthetic resin is, for example, polytetrafluoroethylene, polypropylene, and polyethylene. However, the separator 23 may have a base material made of a single-layer polyolefin porous membrane containing polyethylene. This is because good high-output characteristics can be obtained compared to a laminated membrane. When the first separator member 23A and the second separator member constituting the separator 23 are each a single-layer porous membrane made of polyolefin, the thickness of the porous membrane may be, for example, 10 μm or more and 15 μm or less. When the single-layer porous membrane made of polyolefin has a thickness of 10 μm or more, internal short circuits can be sufficiently avoided. If the thickness of the single-layered porous film made of polyolefin is 15 μm or less, better discharge capacity characteristics can be obtained. In addition, the surface density of the porous film is, for example, 6.3 g / m 2 More than 8.3g / m 2 The surface density of the single-layer porous film made of polyolefin is preferably 6.3 g / m or less. 2 If the surface density of the single-layered porous film made of polyolefin is 8.3 g / m or more, internal short circuits can be sufficiently avoided. 2 If the content is less than this, better discharge capacity characteristics can be obtained.

[0057] In particular, the separator 23 may include, for example, the porous membrane as the substrate and a polymer compound layer provided on one or both sides of the substrate layer. This is because the adhesiveness of the separator 23 to each of the positive electrode 21 and the negative electrode 22 is improved, and thus the distortion of the electrode winding body 20 is suppressed. This suppresses the decomposition reaction of the electrolyte and also suppresses leakage of the electrolyte impregnated in the substrate layer, so that the resistance is less likely to increase even when charging and discharging are repeated, and battery swelling is suppressed. The polymer compound layer includes, for example, a polymer compound such as polyvinylidene fluoride. This is because it has excellent physical strength and is electrochemically stable. However, the polymer compound may be other than polyvinylidene fluoride. When forming this polymer compound layer, for example, a solution in which a polymer compound is dissolved in an organic solvent or the like is applied to the substrate layer, and then the substrate layer is dried. Note that the substrate layer may be immersed in the solution and then dried. The polymer compound layer may contain one or more types of insulating particles such as inorganic particles, for example, aluminum oxide and aluminum nitride.

[0058] (electrolyte) The electrolyte contains a solvent and an electrolyte salt. However, the electrolyte may further contain any one or more of other materials such as additives. The solvent contains any one or more of non-aqueous solvents such as organic solvents. The electrolyte containing a non-aqueous solvent is a so-called non-aqueous electrolyte. The non-aqueous solvent contains, for example, a fluorine compound and a dinitrile compound. The fluorine compound contains, for example, at least one of fluorinated ethylene carbonate, trifluorocarbonate, trifluoroethyl methyl carbonate, fluorinated carboxylic acid ester, and fluorine ether. The non-aqueous solvent may further contain at least one of nitrile compounds other than the dinitrile compound, such as a mononitrile compound or a trinitrile compound. As the dinitrile compound, for example, succinonitrile (SN) is preferable. However, the dinitrile compound is not limited to succinonitrile, and may be other dinitrile compounds such as adiponitrile.

[0059] The electrolyte salt includes, for example, one or more of salts such as lithium salt. However, the electrolyte salt may include, for example, a salt other than lithium salt. The salt other than lithium is, for example, a salt of a light metal other than lithium. The lithium salt is, for example, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), dilithium hexafluorosilicate (Li2SF6), lithium chloride (LiCl), and lithium bromide (LiBr). Among them, any one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate are preferred, and lithium hexafluorophosphate is more preferred. The content of the electrolyte salt is not particularly limited, but is preferably 0.3 mol / kg to 3 mol / kg relative to the solvent. When the electrolyte contains LiPF6 as the electrolyte salt, the concentration of LiPF6 in the electrolyte is preferably 1.25 mol / kg or more and 1.45 mol / kg or less. This is because cycle deterioration due to consumption (decomposition) of salt during high-load rate charging can be prevented, and high-load cycle characteristics are improved. When the electrolyte salt further contains LiBF4 in addition to LiPF6, the concentration of LiBF4 in the electrolyte is preferably 0.001 (wt%) or more and 0.1 (wt%) or less. This is because cycle deterioration due to consumption (decomposition) of salt during high-load rate charging can be more effectively prevented, and high-load cycle characteristics are further improved.

[0060] [1-2. Operation] In the secondary battery 1 of the present embodiment, for example, during charging, lithium ions are released from the positive electrode 21 and are absorbed in the negative electrode 22 via the electrolyte. In addition, in the secondary battery 1, for example, during discharging, lithium ions are released from the negative electrode 22 and are absorbed in the positive electrode 21 via the electrolyte.

[0061] [1-3. Manufacturing method] A method for manufacturing the secondary battery 1 will be described with reference to Fig. 7 in addition to Figs. 1 to 6B. Fig. 7 is a perspective view illustrating the manufacturing process of the secondary battery shown in Fig. 1.

[0062] First, a positive electrode current collector 21A is prepared, and a positive electrode active material layer 21B is selectively formed on the surface of the positive electrode current collector 21A. Then, an insulating layer 101 is formed on the surface of the positive electrode current collector 21A along the first edge 21BT1 of the positive electrode active material layer 21B. Furthermore, predetermined regions of the positive electrode active material layer 21B are dug down by, for example, laser ablation to form the thin portions 61 and 62. The positive electrode 21 is obtained by the above operations. Next, a negative electrode current collector 22A is prepared, and a negative electrode active material layer 22B is selectively formed on the surface of the negative electrode current collector 22A to form a negative electrode 22 having a negative electrode covering region 221 and a negative electrode exposed region 222. A drying process may be performed on the positive electrode 21 and the negative electrode 22. Next, the positive electrode 21 and the negative electrode 22 are stacked with the first separator member 23A and the second separator member 23B interposed therebetween so that the positive electrode exposed region 212 and the first portion 222A of the negative electrode exposed region 222 are opposite each other in the W direction, thereby producing the laminate S20. After that, the laminate S20 is spirally wound so that the through-holes 26 are formed. At that time, for example, a cylindrical winding core is used as a jig, and the laminate S20 is wound around the cylindrical winding core. Furthermore, a fixing tape 46 is attached to the outermost circumference of the spirally wound laminate S20, and then the winding core is removed. In this way, the electrode wound body 20 is obtained as shown in FIG. 7(A).

[0063] Next, as shown in Fig. 7B, an edge of a flat plate having a thickness of, for example, 0.5 mm is pressed perpendicularly against the upper end face 41 and the lower end face 42 of the electrode winding body 20, i.e., in the Z-axis direction, to locally bend a part of the upper end face 41 and a part of the lower end face 42. As a result, grooves 43 are formed that extend radially from the through-holes 26 in the radial direction (R direction). Note that the number and arrangement of the grooves 43 shown in Fig. 7B are merely examples and the present disclosure is not limited thereto.

[0064] 7C, substantially the same pressure is applied from above and below the electrode winding body 20 in a substantially vertical direction to the upper end face 41 and the lower end face 42 at the same time. At this time, for example, a rod-shaped jig is inserted into the through hole 26. By doing so, the positive electrode exposed region 212 and the first part 222A of the negative electrode exposed region 222 are bent so that the upper end face 41 and the lower end face 42 are flat. At this time, it is preferable that a plurality of adjacent parts in the radial direction of the electrode winding body 20 among the positive electrode edge portion 212E of the positive electrode exposed region 212 on the upper end face 41 bend toward the through hole 26 so as to overlap each other. Similarly, it is preferable that a plurality of adjacent parts in the radial direction of the electrode winding body 20 among the negative electrode edge portion 222E of the negative electrode exposed region 222 on the lower end face 42 bend toward the through hole 26 so as to overlap each other. Thereafter, the sectorial portion 31 of the positive current collector 24 is joined to the upper end face 41 by laser welding or the like, and the sectorial portion 33 of the negative current collector 25 is joined to the lower end face 42 by laser welding or the like.

[0065] Next, insulating tapes 53, 54 are attached to predetermined positions of the electrode winding body 20. Thereafter, as shown in (D) of Fig. 7, the belt-shaped portion 32 of the positive current collector plate 24 is folded, and the belt-shaped portion 32 is inserted into the hole 12H of the insulating plate 12. In addition, the belt-shaped portion 34 of the negative current collector plate 25 is folded, and the belt-shaped portion 34 is inserted into the hole 13H of the insulating plate 13.

[0066] Next, the electrode winding body 20 assembled as described above is inserted into the exterior can 11 shown in Fig. 7(E), and then the bottom 11B of the exterior can 11 is welded to the negative electrode current collector 25. Then, a constricted portion 11S is formed near the open end 11N of the exterior can 11. Furthermore, an electrolyte is injected into the exterior can 11, and then the band-shaped portion 32 of the positive electrode current collector 24 is welded to the safety valve mechanism 30.

[0067] 7(F), the outer can 11 is sealed with the gasket 15, the safety valve mechanism 30, and the battery lid 14, making use of the narrowed portion 11S. Finally, the outer can 11 with the washer 55 attached to the battery lid 14 is covered with the outer tube 50, and then the outer tube 50 is heated and shrunk, for example by applying hot air to the outer tube 50, so that the outer tube 50 is tightly attached to the outer surface of the outer can 11.

[0068] Through the above steps, the secondary battery 1 of the present embodiment is completed.

[0069] [1-4. Actions and Effects] In this manner, in the secondary battery 1 of the present embodiment, the thin portion 61 and the thick portion 71 are provided adjacent to each other in the W direction perpendicular to the winding direction (L direction) in the positive electrode active material layer 21B. In this manner, by providing the thin portion 61 having a small thickness in a part of the positive electrode active material layer 21B, it is possible to reduce stress concentration inside the electrode winding body 20 accommodated in the outer can 11. Specifically, when the negative electrode 22 expands inside the electrode winding body 20 due to charging and discharging, it is possible to prevent the occurrence of large deformation such as buckling (bending) of the positive electrode current collector 21A. This is because the amount of electrode reactant (e.g., lithium ions) supplied to a part of the negative electrode active material layer 22B facing the thin portion 61 is reduced, thereby suppressing the expansion and contraction of the part of the negative electrode active material layer 22B facing the thin portion 61. As a result, the stress applied to the separator 23 separating the positive electrode 21 and the negative electrode 22 is also alleviated, and even if the thickness of the separator 23 is reduced, the separator 23 can be prevented from breaking, and the occurrence of a short circuit between the positive electrode 21 and the negative electrode 22 can be prevented. That is, the separator 23 can be made thinner. As a result, the gap between the positive electrode 21 and the negative electrode 22 can be narrowed, the internal resistance of the electrode winding body 20 can be reduced, and the charge / discharge rate characteristics can be improved and the capacity of the secondary battery 1 can be increased. On the other hand, since the positive electrode active material layer 21B includes the thick portion 71 at a position adjacent to the thin portion 61 in the W direction, the separator 23 disposed between the positive electrode active material layer 21B and the negative electrode active material layer 22B can be firmly held. As a result, the electrode winding body 20 is less likely to collapse when the electrode winding body 20 expands and contracts, and the separator 23 can be prevented from shifting from a predetermined position. As a result, it is possible to prevent a short circuit from occurring between the positive electrode 21 and the negative electrode 22. Therefore, according to the secondary battery 1 of the present embodiment, excellent reliability can be ensured.

[0070] In the secondary battery 1 of the present embodiment, the thin portion 61 includes the edge 21E1 of the positive electrode 21 on the winding center side in the L direction. That is, the thin portion 61 is provided at a position of the positive electrode active material layer 21 closest to the winding center. This makes it possible to effectively reduce stress concentration in the vicinity of the center of the electrode winding body 20, where stress concentration is likely to occur significantly, within the inside of the electrode winding body 20.

[0071] In addition, in the secondary battery 1 of the present embodiment, the thick portion 71 is provided between the thin portion 61 and the insulating layer 101. This ensures a sufficient thickness for the insulating layer 101, thereby improving the insulating performance of the insulating layer 101. Furthermore, by making the thick portion 71 contact with the insulating layer 101, it is possible to make the insulating layer 101 less likely to fall off the positive electrode current collector 21A and the positive electrode active material layer 21B.

[0072] Furthermore, in the secondary battery 1 of the present embodiment, the positive electrode active material layer 21B further includes a thick portion 72 including the second edge 21BT2 located opposite the first edge 21BT1 in the W direction, so that the separator 23 arranged between the positive electrode active material layer 21B and the negative electrode active material layer 22B can be more firmly held.

[0073] In the secondary battery 1 of the present embodiment, the positive electrode active material layer 21B further includes a thick portion 73 provided on the opposite side of the winding center side edge 21E1 in the L direction as viewed from the thin portion 61. This is advantageous in ensuring a predetermined battery capacity while mitigating stress concentration in the vicinity of the winding center of the electrode winding body 20.

[0074] In the secondary battery 1 of the present embodiment, both the positive electrode inner periphery side active material layer 21B1 and the positive electrode outer periphery side active material layer 21B2 include the thin portion 61 and the thick portions 71-73, so that it is possible to more effectively alleviate stress concentration in the vicinity of the winding center of the electrode wound body 20. In the secondary battery 1 of the present embodiment, the thin portion 61 is provided in a region including the center in the W direction, which is the width direction of the positive electrode 21, so that it is possible to effectively alleviate stress concentration inside the electrode wound body 20.

[0075] In addition, in the secondary battery 1 of this embodiment, in addition to the thin portion 61, a thin portion 62 is also provided on the outer periphery of the electrode winding body 20. Therefore, the step between the portion where the positive electrode 21 is present and the portion where the positive electrode 21 is not present on the outer periphery of the electrode winding body 20 can be made smaller than when a positive electrode 21 without the thin portion 62 is used. Therefore, stress concentration on the portion of the separator 23 that overlaps with the outer periphery of the winding edge 21E2 can be alleviated. Therefore, even if the thickness of the separator 23 is reduced, the separator 23 can be prevented from breaking, and a short circuit between the positive electrode 21 and the negative electrode 22 can be prevented. That is, the separator 23 can be made thinner. As a result, the gap between the positive electrode 21 and the negative electrode 22 can be narrowed, the internal resistance of the electrode winding body 20 can be reduced, and the charge / discharge rate characteristics can be improved and the capacity of the secondary battery 1 can be increased. Furthermore, if the secondary battery is a lithium ion secondary battery, sufficient battery capacity can be stably obtained by utilizing the absorption and release of lithium, so that higher operational reliability can be obtained.

[0076] <2. Application Examples> The secondary battery 1 according to the embodiment of the present disclosure may be used, for example, as described below.

[0077] [2-1. Battery pack] 8 is a block diagram showing an example of a circuit configuration in which a battery according to an embodiment of the present invention (hereinafter referred to as a secondary battery) is applied to a battery pack 300. The battery pack 300 includes a battery pack 301, an exterior, a switch unit 304 including a charge control switch 302a and a discharge control switch 303a, a current detection resistor 307, a temperature detection element 308, and a control unit 310.

[0078] The battery pack 300 includes a positive terminal 321 and a negative terminal 322, and during charging, the positive terminal 321 and the negative terminal 322 are connected to the positive terminal and the negative terminal of a charger, respectively, for charging. When the electronic device is in use, the positive terminal 321 and the negative terminal 322 are connected to the positive terminal and the negative terminal of the electronic device, respectively, for discharging.

[0079] The battery pack 301 is formed by connecting a plurality of secondary batteries 301a in series or parallel. The secondary battery 1 described above can be used as the secondary batteries 301a. Note that, although Fig. 8 shows an example in which six secondary batteries 301a are connected in 2 parallel 3 series (2P3S), any other connection method such as n parallel m series (n and m are integers) may be used.

[0080] Switch unit 304 includes charge control switch 302a and diode 302b, as well as discharge control switch 303a and diode 303b, and is controlled by control unit 310. Diode 302b has a polarity in the reverse direction to the charge current flowing from positive terminal 321 to battery pack 301, and a polarity in the forward direction to the discharge current flowing from negative terminal 322 to battery pack 301. Diode 303b has a polarity in the forward direction to the charge current, and a polarity in the reverse direction to the discharge current. Although switch unit 304 is provided on the + side in FIG. 8, it may be provided on the - side.

[0081] The charge control switch 302a is controlled by the charge / discharge control unit so that it is turned off when the battery voltage reaches the overcharge detection voltage and so that the charging current does not flow in the current path of the assembled battery 301. After the charge control switch 302a is turned off, only discharging is possible through the diode 302b. In addition, the control unit 310 controls the switch so that it is turned off when a large current flows during charging and so that the charging current flowing in the current path of the assembled battery 301 is interrupted. The discharge control switch 303a is controlled by the control unit 310 so that it is turned off when the battery voltage reaches the overdischarge detection voltage and so that the discharging current does not flow in the current path of the assembled battery 301. After the discharge control switch 303a is turned off, only charging is possible through the diode 303b. In addition, the control unit 310 controls the switch so that it is turned off when a large current flows during discharging and so that the discharging current flowing in the current path of the assembled battery 301 is interrupted.

[0082] Temperature detection element 308 is, for example, a thermistor that is provided near battery pack 301 and measures the temperature of battery pack 301 and supplies the measured temperature to control unit 310. Voltage detection unit 311 measures the voltage of battery pack 301 and each secondary battery 301a that constitutes it, A / D converts the measured voltage, and supplies it to control unit 310. Current measurement unit 313 measures the current using current detection resistor 307, and supplies this measured current to control unit 310. Switch control unit 314 controls charge control switch 302a and discharge control switch 303a of switch unit 304 based on the voltage and current input from voltage detection unit 311 and current measurement unit 313.

[0083] When the voltage of any of the multiple secondary batteries 301a falls below the overcharge detection voltage or the overdischarge detection voltage, or when a large current suddenly flows, the switch control unit 314 sends a control signal to the switch unit 304 to prevent overcharging, overdischarging, and overcurrent charging and discharging. Here, for example, if the secondary battery is a lithium ion secondary battery, the overcharge detection voltage is set to, for example, 4.20V±0.05V, and the overdischarge detection voltage is set to, for example, 2.4V±0.1V.

[0084] The charge / discharge switch may be a semiconductor switch such as a MOSFET. In this case, the parasitic diode of the MOSFET functions as the diodes 302b and 303b. When a P-channel FET is used as the charge / discharge switch, the switch control section 314 supplies control signals DO and CO to the gates of the charge control switch 302a and the discharge control switch 303a, respectively. When the charge control switch 302a and the discharge control switch 303a are P-channel types, they are turned on by a gate potential that is lower than the source potential by a predetermined value or more. That is, in normal charge and discharge operations, the control signals CO and DO are at a low level, and the charge control switch 302a and the discharge control switch 303a are turned on.

[0085] For example, in the event of overcharging or overdischarging, the control signals CO and DO are set to a high level, and the charge control switch 302a and the discharge control switch 303a are set to an OFF state.

[0086] The memory 317 is made up of RAM and ROM, such as a non-volatile memory such as EPROM (Erasable Programmable Read Only Memory). In the memory 317, numerical values ​​calculated by the control unit 310 and the internal resistance value of each secondary battery 301a in the initial state measured during the manufacturing process are stored in advance, and can be rewritten as necessary. In addition, by storing the full charge capacity of the secondary battery 301a, it is possible to calculate, for example, the remaining capacity together with the control unit 310.

[0087] The temperature detection unit 318 measures the temperature using the temperature detection element 308, and performs charge / discharge control in the event of abnormal heat generation, and performs correction in the calculation of remaining capacity.

[0088] [2-2. Energy storage system] The secondary battery according to the embodiment of the present disclosure described above can be mounted on devices such as electronic devices, electric vehicles, electric aircraft, and power storage devices, or can be used to supply power.

[0089] Examples of electronic devices include notebook computers, smartphones, tablet devices, PDAs (personal digital assistants), mobile phones, wearable devices, cordless phone handsets, video movie players, digital still cameras, e-books, electronic dictionaries, music players, radios, headphones, game consoles, navigation systems, memory cards, pacemakers, hearing aids, power tools, electric shavers, refrigerators, air conditioners, televisions, stereos, water heaters, microwave ovens, dishwashers, washing machines, dryers, lighting equipment, toys, medical equipment, robots, road conditioners, and traffic lights.

[0090] Examples of electric vehicles include railroad cars, golf carts, electric carts, electric cars (including hybrid cars), and the like, and the device is used as a driving power source or auxiliary power source for these vehicles. Examples of power storage devices include power storage power sources for buildings such as homes, or for power generation facilities.

[0091] <3. Modifications> (First Modification) Next, a description will be given of a positive electrode 21-1 as a first modified example applied to secondary battery 1 of the above embodiment. Fig. 9 shows a cross-sectional configuration of positive electrode 21-1, and corresponds to Fig. 4C showing positive electrode 21 of the above embodiment.

[0092] As shown in FIG. 9, in the positive electrode 21-1 as the first modified example, the position of the boundary 21B1K1 in the L direction is different from the position of the boundary 21B2K1 in the L direction. That is, the length L1 from the edge 21E1 on the winding center side to the position of the boundary 21B1K1 is different from the length L2 from the edge 21E1 on the winding center side to the position of the boundary 21B2K1. Also, the position of the boundary 21B1K2 in the L direction is different from the position of the boundary 21B2K2 in the L direction. That is, the length L3 from the edge 21E2 on the winding outer periphery side to the position of the boundary 21B1K2 is different from the length L4 from the edge 21E2 on the winding outer periphery side to the position of the boundary 21B2K2. Except for these points, the configuration of the positive electrode 21-1 is substantially the same as the configuration of the positive electrode 21 in the above embodiment. In the configuration example of the positive electrode 21-1 shown in Fig. 9, the length L1 is longer than the length L2, and the length L3 is shorter than the length L4, but the present disclosure is not limited to this. The length L1 may be shorter than the length L2. Also, the length L3 may be longer than the length L4.

[0093] In this way, in the positive electrode 21-1, the L-direction position of the boundary 21B1K1 is different from the L-direction position of the boundary 21B2K1, and the L-direction position of the boundary 21B1K2 is different from the L-direction position of the boundary 21B2K2. That is, the L-direction position of the step in the positive electrode inner periphery side active material layer 21B1 is different from the L-direction position of the step in the positive electrode outer periphery side active material layer 21B2. Therefore, the location where stress is concentrated on the positive electrode current collector inner periphery surface 21A1 caused by the expansion of the negative electrode 22 is shifted from the location where stress is concentrated on the positive electrode current collector outer periphery surface 21A2 caused by the expansion of the negative electrode 22. Therefore, the stress applied to the positive electrode current collector 21A is dispersed. Therefore, according to a secondary battery 1 including an electrode winding body 20 having a positive electrode 21-1 as the first modified example, stress concentration inside the electrode winding body 20 due to expansion and contraction can be further alleviated compared to the case where the positive electrode 21 of the above embodiment is used.

[0094] (Second Modification) Next, a positive electrode 21-2 as a second modified example applied to the secondary battery 1 of the above embodiment will be described with reference to Fig. 10A and Fig. 10B. Fig. 10A is a development view of the positive electrode 21-2, and corresponds to Fig. 4A showing the positive electrode 21 of the above embodiment. Fig. 10B is a development view of the positive electrode 21-2, and corresponds to Fig. 4C showing the positive electrode 21 of the above embodiment. Fig. 10B shows a cross section taken along the line XB-XB shown in Fig. 10A as viewed in the direction of the arrows.

[0095] As shown in FIG. 10A and FIG. 10B, in the positive electrode 21-2 as the second modified example, the positive electrode active material layer 21B further includes a groove portion U1 between the thin portion 61 and the thick portion 73, and further includes a groove portion U2 between the thin portion 62 and the thick portion 73. In detail, the positive electrode inner periphery side active material layer 21B1 includes a groove portion U1-1 between the thin portion 61-1 and the thick portion 73-1, and further includes a groove portion U2-1 between the thin portion 62-1 and the thick portion 73-1. In addition, the positive electrode outer periphery side active material layer 21B2 includes a groove portion U1-2 between the thin portion 61-2 and the thick portion 73-2, and further includes a groove portion U2-2 between the thin portion 62-2 and the thick portion 73-2. The groove portions U1 (U1-1, U1-2) and the groove portions U2 (U2-1, U2-2) all extend in the W direction. The groove portion U1 has a thickness smaller than the thickness T61-1 of the thin portion 61-1 of the positive electrode inner periphery side active material layer 21B1. Similarly, the groove portion U2 has a thickness smaller than the thickness T61-2 of the thin portion 61-2 of the positive electrode outer periphery side active material layer 21B2. Note that, in the configuration example of the positive electrode 21-2A in Figs. 10A and 10B, the cross-sectional shapes of the groove portions U1 and U2 are substantially U-shaped, but the cross-sectional shapes of the groove portions U1 and U2 are not limited to the shapes shown in Figs. 10A and 10B, respectively, and can be selected arbitrarily.

[0096] In the positive electrode 21-2, the width of the groove portion U1 and the width of the groove portion U2 may be the same in the L direction, or the width of the groove portion U1 and the width of the groove portion U2 may be different. The width of the groove portion U1 is the length in the L direction from the position of the boundary 73U1 between the thick portion 73-1 and the groove portion U1 to the position of the boundary 61U1 between the thin portion 61-1 and the groove portion U1. The width of the groove portion U2 is the length in the L direction from the position of the boundary 73U2 between the thick portion 73-2 and the groove portion U2 to the position of the boundary 61U2 between the thin portion 61-2 and the groove portion U2. The width of the groove portion U1 and the width of the groove portion U2 are, for example, about 150 μm.

[0097] 10A and 10B, the position of the boundary 73U1 in the L direction is different from the position of the boundary 73U2 in the L direction, and the position of the boundary 61U1 in the L direction is different from the position of the boundary 61U2 in the L direction. However, in the present disclosure, the position of the boundary 73U1-1 in the L direction may be the same as the position of the boundary 73U1-2 in the L direction. Alternatively, the position of the boundary 73U2-1 in the L direction may be the same as the position of the boundary 73U2-2 in the L direction.

[0098] 10A and 10B, the positive electrode inner periphery side active material layer 21B1 includes the groove portion U1 and the positive electrode outer periphery side active material layer 21B2 includes the groove portion U2, but the positive electrode 21-2 may include only one of the groove portion U1 and the groove portion U2. Furthermore, the positive electrode 21-2 may have only one of the positive electrode inner periphery side active material layer 21B1 and the positive electrode outer periphery side active material layer 21B2.

[0099] In this way, the positive electrode 21-2 as the second modified example includes at least one of the groove portion U1 and the groove portion U2, so that when used in the secondary battery 1, the separator 23 can be more firmly held between the positive electrode 21-2 and the negative electrode 22. This is because, by a part of the separator 23 entering at least one of the groove portion U1 and the groove portion U2, the separator 23 sandwiched between the positive electrode 21-2 and the negative electrode 22 is less likely to be displaced or come off from a predetermined position. In addition, in the positive electrode 21-2 as the second modified example, the groove portions U1 and U2 are provided in the positive electrode active material layer 21B, so that when the negative electrode 22 expands due to charging, a part of the expanded negative electrode active material layer 22B can be accommodated in the groove portions U1 and U2. Therefore, the stress concentration inside the outer can 11 can be further alleviated. As a result, in the secondary battery 1 using the positive electrode 21-2, it is possible to effectively prevent a short circuit between the positive electrode 21 and the negative electrode 22, and to ensure better reliability.

[0100] (Third Modification) Next, with reference to FIG. 11A and FIG. 11B, a positive electrode 21-3 and a negative electrode 22-3 as a third modified example of the present disclosure will be described. FIG. 11A is an expanded view of the positive electrode 21-3, and corresponds to FIG. 4A showing the positive electrode 21 of the above embodiment. FIG. 11B is an expanded view of the negative electrode 22-3, and corresponds to FIG. 5A showing the negative electrode 22 of the above embodiment. In the above embodiment, the secondary battery 1 including the so-called tabless structure positive electrode 21 and negative electrode 22 has been described as an example, but the present disclosure is not limited thereto. The secondary battery of the present disclosure may include a positive electrode 21-3 having a tab structure with a positive electrode lead 28 shown in FIG. 11A, and a negative electrode 22-3 having a tab structure with a negative electrode lead 27 shown in FIG. 11B.

[0101] As shown in FIG. 11A, the positive electrode 21-3 includes a positive electrode collector 21A, a positive electrode active material layer 21B, and a protective tape 21C. The positive electrode active material layer 21B covers a part of the surface of the positive electrode collector 21A. As shown in FIG. 11A, the positive electrode covering region 211 and the positive electrode exposed region 212 each extend from the upper end edge 21UT of the positive electrode 21-3 to the lower end edge 21BT of the positive electrode 21-3 along the W direction, which is the short side direction of the positive electrode 21-3. In addition, the two positive electrode exposed regions 212 are provided at both ends of the positive electrode 21-3 in the L direction, which is the long side direction. One of the two positive electrode exposed regions 212 includes the inner peripheral side edge 21S of the positive electrode innermost circumferential portion 21in (FIG. 3) of the positive electrode 21, and the other of the two positive electrode exposed regions 212 includes the winding outer peripheral side edge 21E of the positive electrode outermost circumferential portion 21out (FIG. 3) of the positive electrode 21. The positive electrode covering region 211 is disposed so as to be sandwiched between the two positive electrode exposed regions 212 in the L direction. That is, the positive electrode active material layer 21B is not present at both ends in the L direction, which is the longitudinal direction of the positive electrode current collector 21A. The protective tape 21C is provided in a part of the positive electrode exposed region 212. More specifically, the protective tape 21C covers a portion of the positive electrode exposed region 212 of the positive electrode current collector 21A that faces the negative electrode active material layer 22B. 11A, of the two positive electrode exposed regions 212, the positive electrode lead 28 is provided in the outer positive electrode exposed region 212, but it may also be provided in the inner positive electrode exposed region 212. A positive electrode lead 28 is attached to the positive electrode current collector 21A in the inner positive electrode exposed region 212.

[0102] The protective tape 21C is preferably adhered to the separator 23. This is because it is possible to prevent misalignment between the positive electrode 21 and the separator 23. The protective tape 21C is preferably made of a material that does not swell. This is because it is possible to prevent damage to the negative electrode due to swelling. The protective tape 21C is preferably made of a material that does not swell. This is because it is possible to prevent damage to the negative electrode due to swelling. The protective tape 21C is preferably made of a resin that contains, for example, polyimide (PI).

[0103] As shown in FIG. 11B, the negative electrode 22-3 includes a negative electrode current collector 22A and a negative electrode active material layer 22B. The negative electrode active material layer 22B is provided on both sides of the negative electrode current collector 22A. The negative electrode 22-3 has a negative electrode covering region 221 and a negative electrode exposed region 222. As shown in FIG. 11B, the negative electrode covering region 221 and the negative electrode exposed region 222 each extend from the upper end edge 22UT of the negative electrode 22 to the lower end edge 22BT of the negative electrode 22 along the W direction, which is the short-side direction of the negative electrode 22. In addition, two negative electrode exposed regions 222 are provided at both ends of the negative electrode 22 in the L direction, which is the longitudinal direction. One of the two negative electrode exposed regions 222 includes the inner circumferential edge 22S of the negative electrode innermost circumferential portion 22in (FIG. 2) of the negative electrode 22, and the other of the two negative electrode exposed regions 222 includes the outer circumferential edge 22E of the negative electrode outermost circumferential portion 22out (FIG. 2) of the negative electrode 22. The negative electrode covering region 221 is disposed so as to be sandwiched between the two negative electrode exposed regions 222 in the L direction. That is, the negative electrode active material layer 22B is not present at both ends in the L direction, which is the longitudinal direction of the negative electrode current collector 22A. The size and position of the region of the negative electrode active material layer 22B covering the surface 22Aout may be different from or may be the same as each other.

[0104] The negative electrode lead 27 is attached to the negative electrode current collector 22A in the negative electrode exposed region 222. More specifically, it is attached to the negative electrode current collector 22A in the negative electrode exposed region 222 on the outer periphery of the two negative electrode exposed regions 222. The negative electrode lead 27 is provided such that a part of it protrudes downward from the lower end edge 22BT of the negative electrode 22.

[0105] Each of Fig. 12A and Fig. 12B shows a cross-sectional configuration of the positive electrode 21-3. Fig. 12A shows a cross-section along the line XIIA-XIIA shown in Fig. 11A. Fig. 12B shows a cross-section along the line XIIB-XIIB shown in Fig. 11A.

[0106] The positive electrode active material layer 21B includes thin portions 61, 62 and thick portions 71-75. In the positive electrode 21 of the present embodiment, the thin portions 61, 62 and the thick portions 71-75 are formed on both the positive electrode current collector inner peripheral surface 21A1 and the positive electrode current collector outer peripheral surface 21A2. That is, both the positive electrode inner peripheral side active material layer 21B1 and the positive electrode outer peripheral side active material layer 21B2 include the thin portions 61, 62 and the thick portions 71-75, respectively. In addition, in Figures 12A and 12B, the thin portions 61, 62 and thick portions 71, 72, 73, 74, 75 constituting the positive electrode inner periphery side active material layer 21B1 are referred to as thin portions 61-1, 62-1 and thick portions 71-1, 72-1, 73-1, 74-1, 75-1, respectively, for convenience, and the thin portions 61, 62 and thick portions 71, 72, 73, 74, 75 constituting the positive electrode outer periphery side active material layer 21B2 are referred to as thin portions 61-2, 62-2 and thick portions 71-2, 72-2, 73-2, 74-2, 75-2, respectively, for convenience. 12B, the position in the L direction of boundary 21B1K1 between thin portion 61-1 and thick portion 73-1 coincides with the position in the L direction of boundary 21B2K1 between thin portion 61-2 and thick portion 73-2. Furthermore, the position in the L direction of boundary 21B1K2 between thin portion 62-1 and thick portion 73-1 coincides with the position in the L direction of boundary 21B2K2 between thin portion 62-2 and thick portion 73-2.

[0107] The thin portion 61 includes the edge (inner peripheral edge) 21BS of the positive electrode active material layer 21B on the winding center side in the L direction. The thin portion 61 may extend in the L direction, for example, from the inner peripheral edge 21BS as a starting point, over a range of about 1 to 5 revolutions of the electrode wound body 20. The thick portion 71 is adjacent to the thin portion 61 in the W direction. More specifically, the thick portion 71 is located between the thin portion 61 and the upper end edge 21UT in the W direction. The thick portion 71 includes the first end edge 21BT1. The thick portion 72 is located on the opposite side of the thick portion 71 from the thin portion 61 in the W direction. That is, the thick portion 72 is located between the lower end edge 21BT located on the opposite side of the upper end edge 21UT in the W direction and the thin portion 61. The thick portion 72 includes the lower end edge 21BT. The thick portion 73 is provided on the opposite side of the inner peripheral edge 21S as viewed from the thin portion 61 in the L direction. The thin portion 62 is provided on the opposite side of the thin portion 61 as viewed from the thick portion 73. The thin portion 62 includes the L-direction outer peripheral winding edge 21E of the positive electrode active material layer 21B in the positive electrode 21. The thick portion 74 is adjacent to the thin portion 62 in the W direction. More specifically, the thick portion 74 is located between the thin portion 62 and the upper edge 21UT in the W direction. The thick portion 74 includes the first edge 21BT1. The thick portion 75 is located on the opposite side of the thick portion 74 as viewed from the thin portion 62 in the W direction. That is, the thick portion 75 is located between the lower edge 21BT located on the opposite side of the upper edge 21UT in the W direction and the thin portion 62. The thick portion 75 includes the lower end edge 21BT. The thick portions 71 to 75 may be separated from one another, or may be partially or entirely integrated.

[0108] In the secondary battery including the positive electrode 21-3 and the negative electrode 22-3 as the third modified example, thin portions 61, 62 are provided in the positive electrode active material layer 21B, so that the same effects as those of the above embodiment can be expected.

[0109] (Fourth Modification) Next, a positive electrode 21-4 as a fourth modified example of the present disclosure will be described. FIG. 13A is a development view of the positive electrode 21-4, and FIG. 13B shows a cross-sectional configuration of the positive electrode 21-4. In the positive electrode 21-4, as shown in FIG. 13A and FIG. 13B, both the positive electrode inner periphery side active material layer 21B1 and the positive electrode outer periphery side active material layer 21B2 provided on the positive electrode current collector 21A include thin portions 61, 62 that extend over the entire W direction of the positive electrode covering region 211. Except for this point, the configuration of the positive electrode 21-4 is substantially the same as that of the positive electrode 21-3 (FIG. 11A). In the secondary battery including the positive electrode 21-4 as the fourth modified example, the thin portions 61, 62 are provided in the positive electrode active material layer 21B, so that the same effects as those of the above embodiment can be expected. EXAMPLES

[0110] An embodiment of the present disclosure will be described.

[0111] [Production method] Example 1 As described below, a cylindrical secondary battery shown in FIG. 14 was fabricated, which was equipped with the positive electrode 21-4 shown in FIGS. 13A and 13B and the negative electrode 22-3 shown in FIG. 11B.

[0112] In the secondary battery shown in FIG. 14, for example, a pair of insulating plates 12, 13 and an electrode winding body 20 are housed inside a cylindrical outer can 11. The electrode winding body 20 is sandwiched between the insulating plates 12 and 13 in the Z direction. A safety valve mechanism 30 is attached to the outer can 11. The outer can 11 is sealed by, for example, a battery lid 14. However, this secondary battery may further include a thermosensitive resistor (PTC) element and a reinforcing member inside the outer can 11. The safety valve mechanism 30 is provided on the inside of the battery lid 14 in the Z direction. The safety valve mechanism 30 is a mechanism that releases the internal pressure of the outer can 11 by releasing the sealed state of the outer can 11 as necessary when the internal pressure of the outer can 11 increases. The internal pressure of the outer can 11 increases due to gas generated due to a decomposition reaction of the electrolyte during charging and discharging.

[0113] As the secondary battery of Example 1, a cylindrical lithium ion secondary battery (diameter=outer diameter 18 mm and length 65 mm) shown in FIG. 14 was fabricated by the procedure described below.

[0114] (Preparation of positive electrode) First, the positive electrode active material (LiNi 0.8 Co 0.15 Al 0.05 94 parts by mass of ethylenediaminetetraacetate (ethylenediaminetetraacetate), 3 parts by mass of a positive electrode binder (polyvinylidene fluoride), and 3 parts by mass of a positive electrode conductive agent (graphite) were mixed together to prepare a positive electrode mixture. Next, the positive electrode mixture was added to a solvent (N-methyl-2-pyrrolidone, an organic solvent), and the organic solvent was stirred to prepare a paste-like positive electrode mixture slurry. Next, the positive electrode mixture slurry was applied to both sides of a positive electrode current collector 21A (a strip-shaped aluminum foil having a thickness of 15 μm) using a coating device, and then the positive electrode mixture slurry was dried to form a positive electrode active material layer 21B. Next, the positive electrode active material layer 21B was compression-molded using a roll press machine. Furthermore, predetermined regions of the positive electrode active material layer 21B were dug down by laser ablation to form thin-walled portions 61 and 62. At that time, as shown in FIG. 13A and FIG. 13B, by leaving a part of the positive electrode active material layer 21B, the thick portion 73 was formed without forming the thick portions 71, 72. That is, the thin portions 61, 62 were formed so as to extend over the entire W direction of the positive electrode covering region 211. In addition, the thin portion 61 included the inner peripheral edge 21S, and the thin portion 62 included the outer peripheral edge 21E. In this manner, the positive electrode active material layer 21B including the thin portions 61, 62 and the thick portion 73 was formed on both sides of the positive electrode current collector 21A. Finally, the protective tape 21C was attached to a predetermined position of the positive electrode current collector 21A to obtain a positive electrode 21-3.

[0115] (Preparation of negative electrode) First, 95 parts by mass of a negative electrode active material (graphite), 3 parts by mass of a negative electrode binder (styrene butadiene rubber (SBR)), and 2 parts by mass of a negative electrode conductive agent (carbon black) were mixed together to prepare a negative electrode mixture. Next, the negative electrode mixture was added to a solvent (water), and the organic solvent was stirred to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry was applied to both sides of a negative electrode current collector 22A (a strip-shaped copper foil having a thickness of 15 μm) using a coating device, and then the negative electrode mixture slurry was dried to form a negative electrode active material layer 22B. Finally, the negative electrode active material layer 22B was compression-molded using a roll press machine to obtain a negative electrode 22-3.

[0116] (Preparation of electrolyte) After adding the electrolyte salt (LiPF6) to the solvent (ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate), the solvent was stirred. In this case, the mixing ratio (weight ratio) of the solvent was ethylene carbonate:ethyl methyl carbonate:dimethyl carbonate = 20:20:60, and the content of the electrolyte salt was 1 mol / kg relative to the solvent.

[0117] (Secondary battery assembly) First, an aluminum positive electrode lead 28 was welded to the positive electrode 21-3 (positive electrode current collector 21A), and a nickel negative electrode lead 27 was welded to the negative electrode 22-3 (negative electrode current collector 22A). Next, the positive electrode 21-3 and the negative electrode 22-3 were laminated with each other via a separator 23 (a porous polyethylene film having a thickness of 16 μm), and then the positive electrode 21-3, the negative electrode 22-3, and the separator 23 were wound to produce a wound body having a through hole 20C. When producing this wound body, the positive electrode 21-3 and the negative electrode 22-3 were aligned so that the entire overlapping region between the negative electrode lead 27 and the negative electrode current collector 22A in the stacking direction of the positive electrode 21-3 and the negative electrode 22-3 overlaps with the protective tape 21C in the stacking direction.

[0118] Next, the electrode wound body 20 was housed inside a nickel-plated iron exterior can 11 together with a pair of insulating plates 12, 13. The positive electrode lead 28 was welded to a safety valve mechanism 30, and the negative electrode lead 27 was welded to the exterior can 11. Next, an electrolyte was injected into the interior of the exterior can 11 using a reduced pressure method, and the electrolyte was impregnated into the wound body.

[0119] Next, asphalt was added to a solvent (ethylcyclohexane, an organic solvent) and the solvent was stirred to prepare a coating solution, which was then applied to a polypropylene gasket 15.

[0120] Finally, the open end 11N of the exterior can 11, the battery lid 14 and the safety valve mechanism 30 were crimped together via a polypropylene gasket 15 to form a crimped structure 11R.

[0121] As a result, the open end 11N of the outer can 11 was closed by the battery lid 14, and the electrode winding body 20 and the like were housed inside the outer can 11, so that a cylindrical lithium ion secondary battery was assembled.

[0122] (Stabilization of secondary batteries) The secondary battery was charged and discharged for one cycle in a room temperature environment (temperature = 23°C). During charging, the battery was charged at a constant current of 0.1C until the voltage reached 4.2V, and then charged at a constant voltage of 4.2V until the current reached 0.05C. During discharging, the battery was discharged at a constant current of 0.1C until the voltage reached 3.0V. 0.1C is the current value at which a battery capacity (theoretical capacity) of 4000mAh is fully discharged in 10 hours, and 0.05C is the current value at which a battery capacity of 4000mAh is fully discharged in 20 hours.

[0123] This electrochemically stabilized the state of the secondary battery, resulting in the creation of a cylindrical lithium-ion secondary battery.

[0124] (Reference example 1) A secondary battery of Reference Example 1 was produced in the same manner as in Example 1, except that only the thin portion 61 out of the thin portion 61 and the thin portion 62 was formed in the positive electrode active material layer 21B provided on both sides of the positive electrode current collector 21A.

[0125] [Evaluation of battery characteristics] The secondary batteries obtained as described above in Example 1 and Reference Example 1 were examined for the presence or absence of winding defects, the incidence of short circuits after charge / discharge cycles, and the incidence of short circuits after high-temperature storage. The results are shown in Table 1.

[0126] [Table 1]

[0127] (Whether or not winding is defective) The electrode windings of each secondary battery were evaluated for the presence or absence of physical shorts when electrolyte was not injected. Specifically, HPT (high potential test) was performed. At that time, the insulation resistance was set at 0.2 kV as the reference value. The number of samples was 10,000.

[0128] (Short circuit occurrence rate after charge / discharge cycles) After carrying out a cycle test under the following test conditions, the capacitor was stored for one week in a 25°C environment, and if a voltage drop of 4.1 V or more was observed, it was determined that a short circuit had occurred. The number of samples was 100. Specifically, the cycle test was carried out under the following test conditions.

[0129] (Cycle test conditions) (1) Environmental temperature: 23°C. (2) Charging conditions: constant current constant voltage (CC-CV) charging was performed. The battery was charged at a constant current of 10 A up to a voltage of 4.2 V, and then charged at a constant voltage of 4.2 V. The cutoff current was 1 A. (3) Rest time after charging: 60 minutes. (4) Discharge conditions: Constant current (CC) discharge was performed at a constant current of 50 A. The cut-off voltage was set to 2 V. Discharge was stopped when the temperature reached 85° C. (5) Rest after discharge: The battery was rested until the surface temperature of the battery was below 50°C. . (6) Number of cycles: 100 cycles.

[0130] (Short circuit occurrence rate after high temperature storage) Each secondary battery was fully charged. Specifically, it was charged to a voltage of 4.2 V at a constant current of 0.2 C, and then charged at a constant voltage of 4.2 V. The cut-off current was 15 mA. Then, after storing in a thermostatic chamber at 60°C for 60 days, the voltage of each secondary battery was measured. If the voltage dropped to less than 4 V, it was determined that a short circuit had occurred. The number of samples was 20.

[0131] As shown in Table 1, in Example 1, no winding failure, no short circuit after charge / discharge cycles, and no short circuit after high-temperature storage occurred. In contrast, in Reference Example 1, short circuits after charge / discharge cycles occurred at a rate of 200 ppm (2 out of 10,000 samples). Also, in Reference Example 1, short circuits after high-temperature storage occurred at a rate of 10% (2 out of 20 samples).

[0132] From the above results, it was confirmed that the secondary battery of the present disclosure can ensure superior safety.

[0133] Although the present disclosure has been described above with reference to one embodiment and some modified examples, the configuration of the present disclosure is not limited to the configuration described in the above embodiment and some modified examples, and can be modified in various ways. For example, in the above embodiment, the thin portion 61 as the first thin portion is provided at a position in contact with the winding center side edge 21E1 of the positive electrode 21, but the present disclosure is not limited to this. The first thin portion (thin portion 61) may be provided at a location away from the winding center side edge 21E1 of the positive electrode 21. Similarly, the thin portion 62 as the second thin portion is not limited to a location in contact with the winding outer peripheral side edge 21E2 of the positive electrode 21. The second thin portion (thin portion 62) may be provided at a location away from the winding outer peripheral side edge 21E2 of the positive electrode 21.

[0134] In the above embodiment and examples, the electrode reactant is lithium, but the electrode reactant is not particularly limited. Therefore, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0135] The effects described in this specification are merely examples, and the effects of the present disclosure are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present disclosure.

[0136] The present disclosure may take the following forms. <1> an electrode winding body in which a laminate including a positive electrode, a negative electrode, and a separator is wound along a longitudinal direction of the laminate and has a through hole penetrating in a width direction perpendicular to the longitudinal direction; an exterior can that houses the electrode winding body; Equipped with The positive electrode is a positive electrode current collector extending in both the longitudinal direction and the width direction; a positive electrode active material layer provided on the positive electrode current collector; having The positive electrode active material layer includes a first thin portion, a thick portion having a thickness greater than that of the first thin portion and adjacent to the first thin portion in the longitudinal direction, and a second thin portion located on the opposite side of the first thin portion from the thick portion. Secondary battery. <2> The first thin portion includes an end edge of the positive electrode on the winding center side in the longitudinal direction. the above <1> The secondary battery described herein. <3> The second thin portion includes an outer peripheral end edge of the positive electrode in the longitudinal direction. the above <1> or <2> The secondary battery described herein. <4> The positive electrode active material layer is a first groove portion located between the first thin portion and the thick portion; a second groove portion located between the second thin portion and the thick portion; Also includes the above <1> from <3> 13. The secondary battery according to claim 12, <5> the positive electrode current collector includes an inner peripheral surface of the positive electrode current collector facing the winding center side of the electrode winding body, and an outer peripheral surface of the positive electrode current collector facing the outside opposite to the winding center side of the electrode winding body, The first thin portion, the thick portion, and the second thin portion are formed on both the inner peripheral surface of the positive electrode current collector and the outer peripheral surface of the positive electrode current collector. the above <1> from <4> 13. The secondary battery according to claim 12, <6> the positive electrode current collector includes an inner peripheral surface of the positive electrode current collector facing the winding center side of the electrode winding body and an outer peripheral surface of the positive electrode current collector facing the outside opposite to the winding center side of the electrode winding body, and extends in both the longitudinal direction and the width direction; the positive electrode active material layer includes a first positive electrode active material layer provided on an inner peripheral surface of the positive electrode current collector, and a second positive electrode active material layer provided on an outer peripheral surface of the positive electrode current collector, each of the first positive electrode active material layer and the second positive electrode active material layer includes the first thin portion and the thick portion; In the longitudinal direction, a position of a first boundary between the first thin portion of the first positive electrode active material layer and the thick portion of the first positive electrode active material layer and a position of a second boundary between the first thin portion of the second positive electrode active material layer and the thick portion of the second positive electrode active material layer are different from each other; a position of a third boundary between the second thin portion of the first positive electrode active material layer and the thick portion of the first positive electrode active material layer, and a position of a fourth boundary between the second thin portion of the second positive electrode active material layer and the thick portion of the second positive electrode active material layer are different from each other. the above <1> from <5> 13. The secondary battery according to claim 12, <7> the above <1> from <6> A secondary battery according to any one of the above items, A control unit that controls the secondary battery; an exterior body that encapsulates the secondary battery; A battery pack having [Explanation of symbols]

[0137] 1...Lithium ion secondary battery, 11...Outer can, 11B...Bottom, 11N...Open end, 11W...Side wall, 12, 13...Insulating plate, 14...Battery cover, 15...Gasket, 20...Electrode winding body, S20...Laminate, 21...Positive electrode, 21A...Positive electrode current collector, 21B...Positive electrode active material layer, 21BT1...First edge, 211...Positive electrode covering region, 212...Positive electrode exposed region, 22...Negative electrode, 22A...Negative electrode current collector, 22B...Negative electrode active material layer, 221...Negative electrode covering region, 222...Negative electrode exposed region, 23...separator, 23A...first separator member, 23B...second separator member, 24...positive electrode current collecting plate, 25...negative electrode current collecting plate, 26...through hole, 30...safety valve mechanism, 31, 33...fan-shaped portion, 32, 34...strip-shaped portion, 35, 36...opening, 37...protrusion, 41...upper end surface, 42...lower end surface, 50...outer tube, 53, 54...insulating tape, 55...washer, 61...thin portion, 71-73...thick portion, 101...insulating layer, CL...central axis.

Claims

1. an electrode winding body in which a laminate including a positive electrode, a negative electrode, and a separator is wound along a longitudinal direction of the laminate and has a through hole penetrating in a width direction perpendicular to the longitudinal direction; an exterior can that houses the electrode winding body; Equipped with The positive electrode is a positive electrode current collector extending in both the longitudinal direction and the width direction; a positive electrode active material layer provided on the positive electrode current collector; having The positive electrode active material layer includes a first thin portion, a thick portion having a thickness greater than that of the first thin portion and adjacent to the first thin portion in the longitudinal direction, and a second thin portion located on the opposite side of the first thin portion from the thick portion. Secondary battery.

2. The first thin portion includes an end edge of the positive electrode on the winding center side in the longitudinal direction. The secondary battery according to claim 1 .

3. The second thin portion includes an outer peripheral end edge of the positive electrode in the longitudinal direction. The secondary battery according to claim 1 .

4. The positive electrode active material layer is a first groove portion located between the first thin portion and the thick portion; a second groove portion located between the second thin portion and the thick portion; Also includes The secondary battery according to claim 1 .

5. the positive electrode current collector includes an inner peripheral surface of the positive electrode current collector facing the winding center side of the electrode winding body, and an outer peripheral surface of the positive electrode current collector facing the outside opposite to the winding center side of the electrode winding body, The first thin portion, the thick portion, and the second thin portion are formed on both the inner peripheral surface of the positive electrode current collector and the outer peripheral surface of the positive electrode current collector, respectively. The secondary battery according to claim 1 .

6. the positive electrode current collector includes an inner peripheral surface of the positive electrode current collector facing the winding center side of the electrode winding body and an outer peripheral surface of the positive electrode current collector facing the outside opposite to the winding center side of the electrode winding body, and extends in both the longitudinal direction and the width direction; the positive electrode active material layer includes a first positive electrode active material layer provided on an inner peripheral surface of the positive electrode current collector, and a second positive electrode active material layer provided on an outer peripheral surface of the positive electrode current collector, each of the first positive electrode active material layer and the second positive electrode active material layer includes the first thin portion and the thick portion; In the longitudinal direction, a position of a first boundary between the first thin portion of the first positive electrode active material layer and the thick portion of the first positive electrode active material layer and a position of a second boundary between the first thin portion of the second positive electrode active material layer and the thick portion of the second positive electrode active material layer are different from each other; A position of a third boundary between the second thin portion of the first positive electrode active material layer and the thick portion of the first positive electrode active material layer and a position of a fourth boundary between the second thin portion of the second positive electrode active material layer and the thick portion of the second positive electrode active material layer are different from each other. The secondary battery according to claim 1 .

7. The secondary battery according to any one of claims 1 to 6, A control unit that controls the secondary battery; an exterior body that encapsulates the secondary battery; A battery pack having

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