Secondary battery and battery pack

Abstract

To provide a secondary battery of which an internal resistance is low.SOLUTION: A secondary battery comprises: first and second electrode winding bodies that include a winding structure that a lamination body containing a first electrode, a second electrode, and a separator is wound along a longitudinal direction of the lamination body, respectively, and include a penetration hole penetrated to a width direction of the lamination body orthogonal to the longitudinal direction; and an outer casing body that houses first and second electrode winding bodies. In each of the first and second electrode winding bodies, a first end surface in which a first electrode is exposed and a second end surface in which a second electrode is exposed are provided to both ends of the width direction of the lamination body. Both of the first and second electrode winding bodies are parallel to the width direction of the lamination body so that both of first end surfaces are faced each other.SELECTED DRAWING: Figure 1

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 performance of secondary batteries.

[0006] Therefore, a secondary battery with low internal resistance is desired. [Means for solving the problem]

[0007] A secondary battery according to an embodiment of the present disclosure includes first and second electrode windings, each having a winding structure in which a laminate including a first electrode, a second electrode, and a separator is wound along the longitudinal direction of the laminate, and each having a through-hole penetrating in the width direction of the laminate perpendicular to the longitudinal direction, and an exterior housing that houses the first and second electrode windings. Each of the first and second electrode windings has a first end face at which the first electrode is exposed and a second end face at which the second electrode is exposed, at both ends in the width direction of the laminate. The first and second electrode windings are arranged in the width direction of the laminate such that the first end faces of the respective electrode windings face each other. Effect of the Invention

[0008] According to the secondary battery of the embodiment of the present disclosure, the first and second electrode winding bodies are housed side by side in the exterior body so that the first end faces of the first and second electrode winding bodies face each other. This shortens the current collection distance in the secondary battery and reduces the internal resistance. As a result, the amount of heat generated inside the secondary battery is reduced, high-output discharge is possible, and excellent battery performance is obtained.

[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 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 perspective view illustrating the manufacturing process of the secondary battery following FIG. [Figure 9] FIG. 9 is a block diagram showing a circuit configuration of a battery pack to which the secondary battery according to an embodiment of the present disclosure is applied. [Figure 10] FIG. 10 is a cross-sectional view illustrating a configuration example of a vertical cross-sectional structure along the height direction of a secondary battery as a modified example of the present disclosure. [Figure 11A] FIG. 11A is a characteristic diagram showing the discharge load characteristic of the first embodiment. [Figure 11B] FIG. 11B is a characteristic diagram showing the discharge load characteristic of Comparative Example 1. 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 a pair of electrode winding bodies 20U, 20L as battery elements housed in the outer can 11. Furthermore, the secondary battery 1 includes an outer tube 50 that covers the outer circumferential surface of the outer can 11. In this specification, the height direction of the secondary battery 1 is defined as the Z-axis direction. In the secondary battery 1, the electrode winding body 20U and the electrode winding body 20L are arranged inside the outer can 11 so as to be aligned in the Z-axis direction.

[0018] More specifically, the secondary battery 1 includes, for example, a pair of insulating plates 12, 13, a pair of electrode winding bodies 20U, 20L, a pair of positive electrode current collectors 24U, 24L, a pair of negative electrode current collectors 25U, 25L, and an intermediate positive electrode current collector 27 inside an outer can 11. Each of the pair of electrode winding bodies 20U, 20L is a structure in which a positive electrode 21 and a negative electrode 22 are stacked and wound with a separator 23 interposed therebetween. Each of the pair of electrode winding bodies 20U, 20L is impregnated with an electrolyte solution that is a liquid electrolyte. The secondary battery 1 may further include, for example, one or more of a potent thermal sensitive resistor (PTC) element and a reinforcing member inside the outer can 11.

[0019] (Outer can 11) As described above, the outer can 11 is a container that houses the pair of electrode winding bodies 20U, 20L, the pair of positive electrode current collector plates 24U, 24L, and the pair of negative electrode current collector plates 25U, 25L. The outer can 11 is also a negative electrode terminal that is connected to the negative electrode 22 via the pair of negative electrode current collector plates 25U, 25L. The outer can 11 has a bottom 11B and a side wall 11W. The outer can 11 has, for example, a hollow cylindrical structure with a lower end in the Z-axis direction that is closed and an upper end that is open. 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. The side wall 11W exists between the open end 11N and the bottom 11B. The side wall 11W stands in the height direction along the outer edge of the bottom 11B so as to surround the pair of electrode winding bodies 20U, 20L. The side wall 11W includes an open end 11N on the opposite side to the bottom 11B, through which the pair of electrode windings 20U, 20L can be inserted. The bottom 11B is connected to the negative electrode 22 of the electrode winding 20L via the negative electrode current collector 25L. The side wall 11W is connected to the negative electrode 22 of the electrode winding 20U via the connection member 28 and the negative electrode current collector 25U in the vicinity of the open end 11N. The material constituting 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, for example, a metal material such as nickel. The insulating plate 12 and the insulating plate 13 are arranged to face each other so as to sandwich the pair of negative electrode current collectors 25U, 25L between them in the Z-axis direction, for example. 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 disk-shaped member having a surface perpendicular to the central axis CL of the secondary battery 1, i.e., a surface perpendicular to the Z-axis in Fig. 1, with an opening provided at the center. However, the insulating plate 12 may further have a cylindrical portion erected toward the inside of the electrode winding body 20U around the opening of the disk-shaped member. This is to prevent the connection member 29 described later from contacting the negative electrode 22 around the through-hole 26U of the electrode winding body 20U.

[0023] (Crimped structure 11R) At the open end 11N of the outer 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 battery lid 14 seals the outer can 11 with the pair of electrode wound bodies 20U, 20L, etc., housed inside the outer can 11. The crimped structure 11R is a so-called crimp structure, and has a bent portion 11P as a so-called crimp portion. In addition, a constricted portion 11S is provided below the bent portion 11P so that a part of the outer can 11 protrudes inward.

[0024] (Battery cover 14) The battery lid 14 is a closing member that mainly closes the open end 11N when the pair of electrode winding bodies 20U, 20L, etc. are stored inside the exterior can 11. The combination of the battery lid 14 and the exterior can 11 corresponds to a specific example of the "exterior body" of the present disclosure. The battery lid 14 and the bottom 11B of the exterior can 11 face each other in the Z-axis direction, sandwiching the pair of electrode winding bodies 20U, 20L therebetween. The battery lid 14 is a specific example that corresponds to the "first bottom" of the present disclosure, the bottom 11B of the exterior can 11 is a specific example that corresponds to the "second bottom" of the present disclosure, and the side wall 11W of the exterior can 11 is a specific example that corresponds to the "wall" of the present disclosure. The battery lid 14 faces the second end surface 42U (described later) of the electrode winding body 20U. The bottom 11B of the outer can 11 faces a second end surface 42L (described later) of the electrode winding body 20L. The battery lid 14 is, for example, a conductor containing the same material as the material forming the outer can 11. The battery lid 14 closes the open end 11N of the outer can 11 and is connected to the pair of positive electrode current collectors 24U, 24L. Therefore, the battery lid 14 is also a positive electrode terminal connected to each of the positive electrodes 21 of the pair of electrode winding bodies 20U, 20L via the pair of positive electrode current collectors 24U, 24L. 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 bodies 20U, 20L) The electrode winding body 20U and the electrode winding body 20L are arranged so as to be aligned in the Z-axis direction, which is the height direction of the secondary battery 1. Specifically, the electrode winding body 20U is located at the upper part of the secondary battery 1, and the electrode winding body 20L is located at the lower part of the secondary battery 1. The electrode winding body 20U has a first end surface 41U where the positive electrode 21 is exposed and a second end surface 42U where the negative electrode 22 is exposed, at both ends in the width direction of the laminate S20 described later, i.e., both ends in the Z-axis direction. The electrode winding body 20L has a first end surface 41L where the positive electrode 21 is exposed and a second end surface 42L where the negative electrode 22 is exposed, at both ends in the width direction of the laminate S20, i.e., both ends in the Z-axis direction. In the configuration example shown in FIG. 1, the electrode winding body 20U and the electrode winding body 20L are aligned in the Z-axis direction so that the first end surface 41U and the first end surface 41L face each other. Therefore, in the configuration example shown in FIG. 1, the second end surface 42U of the electrode winding body 20U faces the insulating plate 12 via the negative current collector 25U, and the second end surface 42L of the electrode winding body 20L faces the insulating plate 13 via the negative current collector 25L. Between the first end surface 41U and the first end surface 41L, the positive current collectors 24U, 24L and the intermediate positive current collector 27 are arranged. The intermediate positive current collector 27 is sandwiched between the positive current collector 24U and the positive current collector 24L in the Z-axis direction. The intermediate positive current collector 27 is a disc-shaped conductive member having an opening at a position corresponding to the through holes 26U, 26L, for example. The electrode winding bodies 20U, 20L are power generating elements that advance charge and discharge reactions. The electrode winding bodies 20U, 20L each include a positive electrode 21, a negative electrode 22, a separator 23, and an electrolytic solution which is a liquid electrolyte. Here, for example, the electrode winding body 20U is a specific example corresponding to the "first electrode winding body" of the present disclosure, and the electrode winding body 20L is a specific example corresponding to the "second electrode winding body" of the present disclosure. Also, for example, the positive electrode current collector 24U is a specific example corresponding to the "first first electrode current collector" of the present disclosure, and the positive electrode current collector 24L is a specific example corresponding to the "second first electrode current collector" of the present disclosure. Furthermore, the negative electrode current collector 25U is a specific example corresponding to the "first second electrode current collector" of the present disclosure, and the negative electrode current collector 25L is a specific example corresponding to the "second second electrode current collector" of the present disclosure.

[0028] The pair of electrode winding bodies 20U, 20L each include a laminate S20. The laminate S20 included in each of the pair of electrode winding bodies 20U, 20L has substantially the same configuration. FIG. 2 is a development view of the laminate S20, and is a schematic representation of a part of the laminate S20. As shown in FIG. 2, the laminate S20 includes a positive electrode 21 as a first electrode, a negative electrode 22 as a second electrode, and a separator 23. In the laminate S20, the positive electrode 21 and the negative electrode 22 are stacked on each other with the separator 23 interposed therebetween. The separator 23 has, for example, two base materials, that is, a first separator member 23A and a second separator member 23B. Therefore, the laminate S20 has a four-layer structure in which the positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are stacked in 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 pair of electrode winding bodies 20U, 20L are wound around a through hole 26 along a central axis CL extending in the Z-axis direction so that the laminate S20 forms 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 approximately coincides 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 bodies 20U, 20L. However, in FIG. 3, the separator 23 is omitted in order to improve visibility. The electrode winding bodies 20U, 20L have an appearance of a substantially cylindrical shape 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 bodies 20U, 20L. 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 26 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 26. In FIG. 1, the reference symbol 26U denotes the through hole 26 of the electrode winding body 20U, and the reference symbol 26L denotes the through hole 26 of the electrode winding body 20L. As shown in FIG. 1, the electrode winding body 20U and the electrode winding body 20L are arranged such that the through hole 26U and the through hole 26L communicate with each other in the Z-axis direction.

[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 portion 21out located at the outermost circumference of the positive electrode 21 included in each of the electrode winding bodies 20U and 20L is located inside the negative electrode outermost circumference portion 22out located at the outermost circumference of the negative electrode 22 included in each of the electrode winding bodies 20U and 20L. Here, the positive electrode outermost circumference portion 21out is the outermost one-turn portion of the positive electrode 21 in each of the electrode winding bodies 20U and 20L. The negative electrode outermost circumference portion 22out is the outermost one-turn portion of the negative electrode 22 in each of the electrode winding bodies 20U and 20L. On the other hand, the negative electrode 22 is disposed on the innermost side of the positive electrode 21 in each of the electrode windings 20U and 20L. That is, as shown in FIG. 3, the negative electrode innermost circumferential portion 22in located on the innermost side of the negative electrode 22 included in each of the electrode windings 20U and 20L is located on the innermost side of the positive electrode innermost circumferential portion 21in located on the innermost side of the positive electrode 21 included in each of the electrode windings 20U and 20L. Here, the positive electrode innermost circumferential portion 21in is the innermost one-turn portion of the positive electrode 21 in each of the electrode windings 20U and 20L. The negative electrode innermost circumferential portion 22in is the innermost one-turn portion of the negative electrode 22 in each of the electrode windings 20U and 20L. The number of turns 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. FIG. 4B shows a cross-sectional configuration of the positive electrode 21. Note that FIG. 4B shows a cross section in the direction of the arrows along the line IVB-IVB shown in FIG. 4A. The positive electrode 21 includes, for example, a positive electrode collector 21A as a first electrode collector, and a positive electrode active material layer 21B as a first electrode active material layer. 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 winding center side of the electrode winding body 20, i.e., facing the central axis CL, and a positive electrode current collector outer peripheral surface 21A2 facing the opposite side to the winding center side of the electrode winding body 20, i.e., the opposite side of 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, which is the longitudinal direction of the positive electrode 21, and the W direction, which is the width 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. As shown in FIG. 4A, the positive electrode covering region 211 and the positive electrode exposed region 212 each extend from the central axis side edge 21E1 to the outer circumferential side edge 21E2 of the positive electrode 21 along the L direction, which is the longitudinal direction of the positive electrode 21. Here, the L direction corresponds to the winding direction of the electrode winding bodies 20U, 20L. That is, in the positive electrode 21, the positive electrode active material layer 21B covers the positive electrode current collector 21A from the central axis side edge 21E1 of the positive electrode 21 to the outer circumferential side edge 21E2 of the positive electrode 21 in the winding direction of the electrode winding bodies 20U, 20L. 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. The W direction substantially coincides with the central axis CL. As shown in FIG. 2, in the electrode windings 20U and 20L, the central axis side edge 21E1 of the positive electrode innermost circumferential portion 21in is located in a position receding inward from the central axis side edge 22E1 of the negative electrode innermost circumferential portion 22in. The positive electrode 21 further has a lower edge 21E3 extending in the L direction at the lower side of the electrode winding body 20. Note that FIG. 4A and FIG. 4B show the positive electrode current collector 21A in a state of extending linearly along the W direction. However, in reality, the positive electrode edge 212E of the positive electrode exposed region 212 is bent toward the central axis CL as shown in FIG. 1, and is connected to the positive electrode current collectors 24U and 24L. That is, the ends of the positive electrode exposed region 212 in the W direction constitute the first end faces 41U, 41L and are connected to the positive electrode current collector plates 24U, 24L (see FIG. 1). The first end faces 41U, 41L are formed by bending the positive electrode edge portion 212E of the positive electrode exposed region 212 toward the through holes 26U, 26L in a rolled state.

[0033] 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 central axis side edge 21E1 to the outer circumferential side edge 21E2, 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 positional deviation 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, for example, a solvent contained in the electrolyte, and may be well bonded to the separator 23. The detailed configuration of the positive electrode 21 will be described later.

[0034] 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 winding center side of the electrode winding body 20, i.e., the central axis CL, and a negative electrode current collector outer peripheral surface 22A2 facing the opposite side to the winding center side of the electrode winding body 20, i.e., the opposite side of 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.

[0035] 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 central axis side edge 22E1 to the outer circumferential edge 22E2 of the negative electrode 22 in the winding direction of the electrode winding bodies 20U and 20L. In contrast, the negative electrode covering region 221 is not provided on the central axis side edge 22E1 and the outer circumferential 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, which is the longitudinal direction of the negative electrode 22. 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 covering region 221 in the W direction, and extends in the L direction from the central axis side edge 22E1 to the outer periphery side edge 22E2 of the negative electrode 22. The second portion 222B and the third portion 222C are provided to sandwich the negative electrode covering region 221 in the L direction. The first portion 222A is located near the lower edge 22E3 of the negative electrode 22. The second portion 222B is located near the central axis side edge 22E1 of the negative electrode 22, for example, and the third portion 222C is located near the outer periphery side edge 22E2 of the negative electrode 22. 5A and 5B, the negative electrode current collector 22A is illustrated as extending linearly along the W direction. However, in reality, the negative electrode edge 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 collectors 25U and 25L. That is, the end of the negative electrode exposed region 222 in the W direction constitutes the second end faces 42U and 42L and is connected to the negative electrode current collectors 25U and 25L (see FIG. 1). Each of the second end faces 42U and 42L is formed by bending the negative electrode edge 222E of the negative electrode exposed region 222 toward the through hole 26 in a rolled state. The detailed configuration of the negative electrode 22 will be described later.

[0036] In the laminate S20, the positive electrode 21 and the negative electrode 22 are laminated with the separator 23 interposed therebetween so that the positive electrode exposed region 212 and the first portion 222A of the negative electrode exposed region 222 are opposite to each other along the width direction W. The electrode windings 20U and 20L have the ends of the separator 23 fixed by attaching an insulating fixing tape 46 to their side portions 45, so that the windings do not become loose. The fixing tape 46 is preferably provided so as to cover the gap between the electrode windings 20U and 20L arranged in the Z-axis direction. This is to prevent the positive electrode current collectors 24U and 24L and the intermediate positive electrode current collector 27 provided in the gap between the electrode windings 20U and 20L from coming into contact with the inner surface of the side wall portion 11W of the exterior can 11, which is the negative electrode terminal, to cause an internal short circuit.

[0037] 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).

[0038] As shown in Fig. 1, in each of the electrode windings 20U, 20L, a plurality of adjacent positive electrode edges 212E in the radial direction (R direction) of the electrode winding 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, thereby forming first end faces 41U, 41L, respectively. Similarly, in each of the electrode windings 20U, 20L, 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, thereby forming second end faces 42U, 42L, respectively. Therefore, a plurality of positive electrode edges 212E of the positive electrode exposed region 212 are gathered at the first end faces 41U, 41L, respectively, and a plurality of negative electrode edges 222E of the negative electrode exposed region 222 are gathered at the second end faces 42U, 42L, respectively. In order to improve the contact between the positive electrode current collectors 24U, 24L and the positive electrode edge 212E for extracting the current, the positive electrode edge 212E bent toward the central axis CL may have a flat surface. Similarly, in order to improve the contact between the negative electrode current collectors 25U, 25L and the negative electrode edge 222E for extracting the current, the negative electrode edge 222E bent toward the central axis CL may have a flat surface. 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 collectors 24U, 24L and the negative electrode current collectors 25U, 25L, respectively.

[0039] The positive electrode collector 21A is made of, for example, aluminum foil, as described later. On the other hand, the negative electrode collector 22A is made of, for example, copper foil, as described later. In this case, the positive electrode collector 21A is softer than the negative electrode 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 collectors 24U and 24L 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 allows the negative electrode exposed region 222 and the negative electrode current collector plates 25U and 25L to be easily joined together. The joining here means that they are joined together by, for example, laser welding, but the joining method is not limited to laser welding.

[0040] 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.

[0041] (Positive current collector 24U, 24L) 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 collectors 24U and 24L are arranged to face the first end faces 41U and 41L, respectively, and the negative electrode current collectors 25U and 25L are arranged to face the second end faces 42U and 42L, respectively. Furthermore, the positive electrode covering regions 211 present on the first end faces 41U and 41L, respectively, and the positive electrode current collectors 24U and 24L are welded at multiple points, and the negative electrode covering regions 221 present on the second end faces 42U and 42L, respectively, and the negative electrode current collectors 25U and 25L are welded at multiple points. In this way, the internal resistance of the secondary battery 1 is reduced. The fact that the first end faces 41U, 41L and the second end faces 42U, 42L are flat as described above also contributes to the low resistance. The positive current collectors 24U, 24L are connected to the intermediate positive current collector 27. The intermediate positive current collector 27 is electrically connected to the battery cover 14 via, for example, a connection member 29 and a safety valve mechanism 30. Therefore, the positive current collectors 24U, 24L are electrically connected to the battery cover 14. The connection member 29 is a cylindrical member having a height direction in the width direction (W direction) of the laminate S20, or a partial cylindrical member having a slit provided in a part of a cylindrical member having a height direction in the width direction (W direction) of the laminate S20. The same material as the material of the positive current collector 24U described later can be used as the material of the connection member 29.

[0042] FIG. 6A is a development view showing one configuration example of the positive current collectors 24U, 24L. The positive current collectors 24U, 24L are metal plates made of, for example, aluminum or an aluminum alloy, or a composite material thereof. As shown in FIG. 6A, each of the positive current collectors 24U, 24L has a substantially sector-shaped sector portion 31 and a substantially rectangular strip portion 32. However, the shape of each of the positive current collectors 24U, 24L is not limited to the shape shown in FIG. 6A and can be selected arbitrarily. In the secondary battery 1, each of the positive current collectors 24U, 24L is accommodated in the exterior can 11 with the strip portion 32 folded relative to the sector portion 31 as shown in FIG. 1. FIG. 6A shows each of the positive current collectors 24U, 24L in an developed state. The sector portion 31 is a facing portion that faces and is connected to the first end faces 41U, 41L. The sector-shaped portion 31 has an outer edge including, 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 an example 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-shaped portion 32 extends in a direction intersecting with the straight portion 31S of the sector-shaped portion 31. In the secondary battery 1, each of the positive electrode current collector plates 24U, 24L is provided so that the opening 35 overlaps with the through holes 26U, 26L in the Z-axis direction. The portion indicated by diagonal lines in FIG. 6A is an insulating portion 32A of the strip-shaped portion 32. The insulating portion 32A is a portion of the strip-shaped portion 32 to which an insulating tape is attached or an insulating material is applied. In the strip-shaped portion 32, the lower portion of the insulating portion 32A is a connection portion 32B to the sealing plate that also serves as an external terminal. The sealing plate is electrically connected to the battery lid 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 portion 32 is less likely to come into contact with a portion of the negative electrode potential. Therefore, each of the positive electrode current collectors 24U, 24L does not need to have the insulating portion 32A. When each of the positive electrode current collectors 24U, 24L 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.

[0043] (Negative electrode current collector plate 25U, 25L) The negative electrode current collector 25U is provided between the battery cover 14 and the second end surface 42U of the electrode winding body 20U, and the negative electrode current collector 25L is provided between the bottom 11B and the second end surface 42L of the electrode winding body 20L. Each of the negative electrode current collectors 25U, 25L is electrically connected to, for example, the outer casing 11. FIG. 6B is a development view showing one configuration example of each of the negative electrode current collectors 25U, 25L. Each of the negative electrode current collectors 25U, 25L is a metal plate made of, for example, nickel, nickel alloy, copper, or copper alloy, or a composite material of two or more of these. The shape of the negative electrode current collectors 25U, 25L shown in FIG. 6B is almost the same as the shape of the positive electrode current collectors 24U, 24L shown in FIG. 6A. Each of the negative electrode current collectors 25U, 25L has a substantially sector-shaped fan-shaped portion 33 and a substantially rectangular strip-shaped portion 34. However, the shape of each of the negative electrode current collectors 25U, 25L is not limited to the shape shown in FIG. 6B, and can be arbitrarily selected. The width W34 of the strip portion 34 is, for example, about 3.0 mm to 8.0 mm. In the secondary battery 1, each of the negative electrode current collectors 25U, 25L is accommodated in the exterior can 11 in a state in which the strip portion 34 is folded with respect to the sector portion 33 as shown in FIG. 1. FIG. 6B shows each of the negative electrode current collectors 25U, 25L in an unfolded state. The sector portion 33 is a facing portion that faces and is connected to the second end faces 42U, 42L. The sector portion 33 has an outer edge that includes, for example, a straight portion and a curved portion. The strip portion 34 is connected to a part of the outer edge of the sector portion 33. The strip portion 34 extends in a direction that intersects with the straight portion of the sector portion 33. The strip portion 34 is shorter than the strip portion 32 and does not have a portion corresponding to the insulating portion 32A of the positive current collector plates 24U and 24L. The strip portion 34 is provided with a plurality of round projections 37 indicated by circles. At least some of the projections 37 provided on the strip portion 34 of the negative current collector plate 25L are welded to the bottom 11B of the outer can 11. During resistance welding, a current is concentrated on the projections 37, which melt the projections 37 and weld the strip portion 34 to the bottom 11B of the outer can 11. The strip portion 34 of the negative current collector plate 25U is electrically connected to the outer can 11 via a connection member 28 as a second connection member. The connection member 28 is an annular member provided so as to go around the central axis CL, and is made of, for example, a conductive material similar to the material of the negative current collector plate 25U.The connection member 28 is connected, for example, to the inner surface of the narrowed portion 11S of the exterior can 11. Like the positive current collector plates 24U, 24L, the negative current collector plates 25U, 25L have an opening 36 formed near the center of the sectorial portion 33. In the secondary battery 1, the negative current collector plates 25U, 25L are provided such that the opening 36 overlaps with the through hole 26 in the Z-axis direction. Fig. 6B illustrates an example in which the opening 36 has a circular planar shape in a horizontal plane perpendicular to the Z-axis direction.

[0044] The sector-shaped portion 31 of the positive electrode current collector plate 24U, 24L covers only a part of the first end surface 41U, 41L due to its planar shape. Similarly, the sector-shaped portion 33 of the negative electrode current collector plate 25U, 25L covers only a part of the second end surface 42U, 42L 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 first end surface 41U, 41L and the second end surface 42U, 42L. The first reason is, for example, to allow the electrolyte to smoothly permeate the electrode winding body 20U, 20L when assembling the secondary battery 1. The second reason is to facilitate the release of gas generated when the lithium ion secondary battery is in an abnormally high temperature state or an overcharged state to the outside.

[0045] (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.

[0046] (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.

[0047] (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.

[0048] (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.

[0049] Further, the negative electrode active material layer 22B may contain, as the 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 simple 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 simple substance described here means a general simple substance, it may contain a trace amount of impurities. That is, the purity of the simple 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 acceptable.

[0050] (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.

[0051] 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 is 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.

[0052] (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.

[0053] 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.

[0054] [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.

[0055] [1-3. Manufacturing method] A method for manufacturing the secondary battery 1 will be described with reference to Figures 7 and 8 in addition to Figures 1 to 6B. Figures 7 and 8 are perspective views illustrating the manufacturing process of the secondary battery shown in Figure 1.

[0056] First, the electrode winding bodies 20U and 20L are prepared. The electrode winding bodies 20U and 20L can be prepared in the same manner as each other as follows. First, a positive electrode collector 21A is prepared, and a positive electrode active material layer 21B is selectively formed on the surface of the positive electrode collector 21A. Then, an insulating layer 101 is formed on the surface of the positive electrode collector 21A so as to follow the edge of the positive electrode active material layer 21B (the boundary between the positive electrode covering region 211 and the positive electrode exposed region 212). Furthermore, a predetermined region of the positive electrode active material layer 21B is dug down by, for example, laser ablation to form a thin portion 61. The positive electrode 21 is obtained by the above operations. Next, a negative electrode collector 22A is prepared, and a negative electrode active material layer 22B is selectively formed on the surface of the negative electrode collector 22A to form a negative electrode 22 having a negative electrode covering region 221 and a negative electrode exposed region 222. The positive electrode 21 and the negative electrode 22 may be dried. 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, to prepare the laminate S20. Then, 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. As a result, the electrode winding bodies 20U and 20L are obtained as shown in FIG. 7(A).

[0057] Next, as shown in FIG. 7B, for example, an edge of a flat plate having a thickness of 0.5 mm is pressed against the first end faces 41U, 41L and the second end faces 42U, 42L of the electrode winding bodies 20U, 20L perpendicularly, i.e., in the Z-axis direction, to locally bend a part of the first end faces 41U, 41L and a part of the second end faces 42U, 42L. As a result, grooves 43 extending radially from the through holes 26U, 26L in the radial direction (R direction) are formed in each of the first end faces 41U, 41L and the second end faces 42U, 42L. Note that the number and arrangement of the grooves 43 shown in FIG. 7B are examples and the present disclosure is not limited thereto.

[0058] Next, substantially the same pressure is applied from above and below the electrode windings 20U, 20L substantially simultaneously in a substantially vertical direction to the first end faces 41U, 41L and the second end faces 42U, 42L. At this time, for example, a rod-shaped jig is inserted into the through holes 26U, 26L. By doing so, as shown in FIG. 7C, the positive electrode exposed region 212 and the first portion 222A of the negative electrode exposed region 222 are each bent so that the first end faces 41U, 41L and the second end faces 42U, 42L are each flat. At this time, it is preferable that a plurality of portions of the positive electrode edge portion 212E of the positive electrode exposed region 212 adjacent to each other in the radial direction of the electrode windings 20U, 20L are bent toward the through holes 26U, 26L so as to overlap each other. Similarly, it is preferable that a plurality of portions of the negative electrode edge portion 222E of the negative electrode exposed region 222 that are adjacent to each other in the radial direction of the electrode windings 20U, 20L bend toward the through holes 26U, 26L so as to overlap each other.

[0059] Thereafter, as shown in FIG. 7(D), the sector-shaped portions 31 of the positive electrode collector plates 24U, 24L are joined to the first end faces 41U, 41L by laser welding or the like, and the sector-shaped portions 33 of the negative electrode collector plates 25U, 25L are joined to the second end faces 42U, 42L by laser welding or the like.

[0060] 8(A), an insulating plate 12 is attached to sandwich the negative current collector 25U between the electrode winding body 20U and the insulating plate 12, and a connecting member 29 is inserted into the through hole 26U of the electrode winding body 20U. Thereafter, the lower end of the connecting member 29 is connected to the intermediate positive current collector 27, and the strip-shaped portion 32 of the positive current collector 24U is connected to the intermediate positive current collector 27. Furthermore, the strip-shaped portion 32 of the positive current collector 24L is connected to the intermediate positive current collector 27. This connects the electrode winding body 20U and the electrode winding body 20L via the intermediate positive current collector 27.

[0061] Next, the insulating plate 13 is attached so as to sandwich the negative electrode current collector 25L between the insulating plate 13 and the second end surface 42L of the electrode winding body 20L. Then, as shown in Fig. 8(B), a connected body in which the electrode winding body 20U and the electrode winding body 20L are connected is inserted into the inside of the outer can 11. Next, the negative electrode current collector 25L is welded to the inner surface of the bottom 11B of the outer can 11, for example, by inserting an electrode rod into the through hole of the connection member 29. Then, an electrolyte is injected into the outer can 11, and the electrolyte is allowed to permeate the electrode winding bodies 20U and 20L.

[0062] 8(C), the annular connection member 28 is connected to the band-shaped portion 34 of the negative electrode current collector 25U and to the inner surface of the narrowed portion 11S of the outer can 11. Furthermore, the narrowed portion 11S is utilized to seal the outer can 11 with the gasket 15, the safety valve mechanism 30, and the battery lid 14. Finally, the outer can 11 with the washer 55 attached to the battery lid 14 is covered with the outer tube 50, and 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 in close contact with the outer surface of the outer can 11.

[0063] Through the above steps, the secondary battery 1 of the present embodiment is completed.

[0064] [1-4. Actions and Effects] Thus, in the secondary battery 1 of this embodiment, the electrode winding body 20U and the electrode winding body 20L are accommodated side by side in the Z-axis direction so that the first end surface 41U and the first end surface 41L face each other inside the exterior body formed of the battery lid 14 and the exterior can 11. Therefore, in the secondary battery 1, the current collection distance is shorter than when, for example, a single electrode winding body whose dimension in the Z-axis direction is equal to the sum of the dimensions of the electrode winding body 20U and the electrode winding body 20L is mounted, and the internal resistance of the secondary battery 1 is reduced. As a result, the amount of heat generated inside the secondary battery 1 can be reduced, and excellent battery performance can be obtained, such as high-output discharge being possible.

[0065] In the secondary battery 1 of this embodiment, the positive electrode current collector 24U connected to the positive electrode 21 of the electrode winding body 20U and the positive electrode current collector 24L connected to the positive electrode 21 of the electrode winding body 20L are electrically connected via the intermediate positive electrode current collector 27, which is a disc-shaped conductive member. This makes it possible to ensure a larger contact area between the positive electrode current collector 24U and the intermediate positive electrode current collector 27 and a larger contact area between the positive electrode current collector 24U and the intermediate positive electrode current collector 27. This makes it possible to further reduce the internal resistance of the secondary battery 1.

[0066] In the secondary battery 1 of this embodiment, if the connection member 29 is a cylindrical member or a partially cylindrical member having a cavity along the Z-axis direction through which the through-hole 26U passes, the negative current collector 25L can be welded to the bottom 11B in a state in which the electrode winding body 20U and the electrode winding body 20L are connected in advance in the manufacturing process of the secondary battery 1. This ensures flexibility in the manufacturing process.

[0067] In the secondary battery 1 of this embodiment, for example, the strip portion 34 of the negative current collector 25U connected to the electrode winding body 20U is connected to the exterior can 11 via the annular connecting member 28, so that the connection resistance between the negative current collector 25U and the exterior can 11 can be reduced compared to, for example, a case in which the strip portion 34 of the negative current collector 25U is directly connected to the exterior can 11. As a result, the internal resistance of the secondary battery 1 can be further reduced.

[0068] 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.

[0069] <2. Application Examples> The secondary battery 1 according to the embodiment of the present disclosure may be used, for example, as described below.

[0070] [2-1. Battery pack] 9 is a block diagram showing an example of a circuit configuration in which a battery according to an embodiment of the present invention (hereinafter, appropriately 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] [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.

[0082] 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.

[0083] 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 sources for storing electricity in buildings such as houses, or power generation facilities.

[0084] <3. Modifications> (First Modification) Next, a secondary battery 2 as a first modified example of the present disclosure will be described. FIG. 10 shows a vertical cross-sectional configuration along the height direction of the secondary battery 2 as a first modified example of the present disclosure. In FIG. 10, the same components as those of the secondary battery 1 shown in FIG. 1 are given the same reference numerals as those of the secondary battery 1. The secondary battery 2 includes positive electrode tabs 61U, 61L instead of the positive electrode current collectors 24U, 24L, and negative electrode tabs 62U, 62L instead of the negative electrode current collectors 25U, 25L. In addition, insulating plates 63, 64 are further provided between the electrode winding body 20U and the electrode winding body 20L. The positive electrode tab 61U electrically connects the positive electrode 21 of the electrode winding body 20U to the battery lid 14, which is the positive electrode terminal. Similarly, the positive electrode tab 61L electrically connects the positive electrode 21 of the electrode winding body 20L to the battery lid 14. The negative electrode tab 62U electrically connects the negative electrode 22 of the electrode winding body 20U to the bottom 11B of the outer can 11, which is the negative electrode terminal. Similarly, the negative electrode tab 62L electrically connects the negative electrode 22 of the electrode winding body 20L to the bottom 11B of the outer can 11.

[0085] In the secondary battery 2 of this modification, the electrode winding body 20U and the electrode winding body 20L are also housed side by side in the Z-axis direction, so that the first end surface 41U and the first end surface 41L face each other, inside the exterior body formed of the battery lid 14 and the exterior can 11. Therefore, in the secondary battery 2, the current collection distance is shorter and the internal resistance of the secondary battery 1 is reduced, compared to the case where, for example, a single electrode winding body whose dimension in the Z-axis direction is equal to the sum of the dimensions of the electrode winding body 20U and the electrode winding body 20L is mounted. As a result, the amount of heat generated inside the secondary battery 2 can be reduced, and excellent battery performance can be obtained, such as enabling high-output discharge. EXAMPLES

[0086] An embodiment of the present disclosure will be described.

[0087] [Production method] Example 1 As described below, a cylindrical secondary battery as shown in Fig. 1 was fabricated. Here, a lithium ion secondary battery having nominal dimensions of 21 mm in diameter and 70 mm in length was fabricated.

[0088] First, an aluminum foil having a thickness of 12 μm was prepared as the positive electrode collector 21A. Next, a layered lithium oxide having a Ni ratio of 85% or more in lithium nickel cobalt aluminum oxide (NCA) as a positive electrode active material, a positive electrode binder made of polyvinylidene fluoride, and a conductive assistant made of a mixture of carbon black, acetylene black, and ketjen black were mixed to obtain a positive electrode mixture. The mixing ratio of the positive electrode active material, the positive electrode binder, and the conductive assistant was 96.4:2:1.6. Next, the positive electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like positive electrode mixture slurry. Next, the positive electrode mixture slurry was applied to predetermined areas on both sides of the positive electrode collector 21A using a coating device, and then the positive electrode mixture slurry was dried to form a positive electrode active material layer 21B. Further, a coating material containing polyvinylidene fluoride (PVDF) was applied to the surface of the positive electrode exposed region 212 adjacent to the positive electrode covering region 211, and dried to form an insulating layer 101 having a width of 3 mm and a thickness of 8 μm. After that, the positive electrode active material layer 21B was compression molded using a roll press. In this manner, a positive electrode 21 having the positive electrode covering region 211 and the positive electrode exposed region 212 was obtained. After that, the positive electrode 21 was sheared to set the width of the positive electrode exposed region 212 in the W direction to 7 mm. Furthermore, the length of the positive electrode 21 in the L direction was set to 1700 mm.

[0089] In addition, a copper foil having a thickness of 8 μm was prepared as the negative electrode current collector 22A. Next, a negative electrode active material obtained by mixing a carbon material made of graphite and SiO, a negative electrode binder made of polyvinylidene fluoride, and a conductive assistant made by mixing carbon black, acetylene black, and ketjen black was mixed to obtain a negative electrode mixture. The mixing ratio of the negative electrode active material, the negative electrode binder, and the conductive assistant was 96.1:2.9:1.0. In addition, the mixing ratio of graphite and SiO in the negative electrode active material was 95:5. Next, the negative electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry was applied to predetermined areas on both sides of the negative electrode current collector 22A using a coating device, and then the negative electrode mixture slurry was dried to form the negative electrode active material layer 22B. Thereafter, the negative electrode active material layer 22B was compression molded using a roll press. In this manner, the negative electrode 22 having the negative electrode covering region 221 and the negative electrode exposed region 222 was obtained. Thereafter, the negative electrode 22 was sheared to set the width in the W direction of the first portion 222A of the negative electrode exposed region 222 to 4 mm. In addition, the length in the L direction of the negative electrode 22 was set to 1760 mm.

[0090] Next, the positive electrode 21 and the negative electrode 22 were 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 were opposite each other in the W direction, to produce the laminate S20. At that time, the laminate S20 was produced so that the positive electrode active material layer 21B did not protrude from the negative electrode active material layer 22B in the W direction. As the first separator member 23A and the second separator member 23B, a polyethylene sheet having a width of 65 mm and a thickness of 5 μm was used. Thereafter, the laminate S20 was spirally wound so that the through-holes 26 were formed, and a fixing tape 46 was attached to the outermost circumference of the wound laminate S20. As a result of the above, the electrode wound bodies 20U and 20L were obtained, respectively.

[0091] Next, the edges of a 0.5 mm thick flat plate were pressed against the first end face 41 and the second end face 42 of the electrode windings 20U, 20L in the Z-axis direction, thereby locally bending the first end face 41 and the second end face 42, respectively, to create grooves 43 extending radially in the radial direction (R direction) from the through hole 26.

[0092] Next, substantially the same pressure was applied from above and below the electrode winding bodies 20U, 20L substantially simultaneously in a direction substantially perpendicular to the first end face 41 and the second end face 42. As a result, the positive electrode exposed region 212 and the first portion 222A of the negative electrode exposed region 222 were folded, respectively, and the first end face 41 and the second end face 42 were made flat. At this time, the positive electrode edge portion 212E of the positive electrode exposed region 212 and the negative electrode edge portion 222E of the negative electrode exposed region 222 on the first end face 41 and the second end face 42 were folded while overlapping toward the through hole 26. Thereafter, the sector-shaped portion 31 of the positive electrode current collector 24 was joined to the first end face 41 by laser welding, and the sector-shaped portion 33 of the negative electrode current collector 25 was joined to the second end face 42 by laser welding. The positive electrode current collector 24 used had a sector-shaped portion 31 provided with an opening 35 having an inner diameter D35 of 4.0 mm.

[0093] Next, the strip portion 32 of the positive current collector 24 was bent to insert the strip portion 32 into the hole in the insulating plate 12 , and the strip portion 34 of the negative current collector 25 was bent to insert the strip portion 34 into the hole in the insulating plate 13 .

[0094] Next, the lower end of the connecting member 29 was connected to the intermediate positive current collector 27, and the strip-shaped portion 32 of the positive current collector 24U was connected to the intermediate positive current collector 27, and the strip-shaped portion 32 of the positive current collector 24L was connected to the intermediate positive current collector 27. In this way, the electrode winding body 20U and the electrode winding body 20L were connected via the intermediate positive current collector 27.

[0095] Next, a connected body in which the electrode winding body 20U and the electrode winding body 20L are connected was inserted into the inside of the outer can 11. The inner diameter of the outer can 11 used was 20.80±0.05 mm. Next, an electrode bar was inserted into the through hole of the connection member 29, and the negative electrode current collector plate 25L was welded to the inner surface of the bottom part 1B of the outer can 11. After that, an electrolyte was injected into the outer can 11, and the electrolyte was allowed to permeate the electrode winding bodies 20U and 20L. The electrolyte used was a solvent in which fluoroethylene carbonate (FEC) and succinonitrile (SN) were added to ethylene carbonate (EC) and dimethyl carbonate (DMC) as the main solvent, and LiBF4 and LiPF6 were used as the electrolyte salt. In the lithium ion secondary battery of this Example, the respective contents (wt %) of EC, DMC, FEC, SN, LiBF4, and LiPF6 in the electrolyte were 12.7:56.2:12.0:1.0:1.0:17.1.

[0096] Next, the annular connecting member 28 was connected to the band-shaped portion 34 of the negative electrode current collector 25U and to the inner surface of the narrowed portion 11S of the outer can 11. Furthermore, the outer can 11 was sealed with the gasket 15, the safety valve mechanism 30, and the battery lid 14, utilizing the narrowed portion 11S. Finally, the outer can 11, on which the washer 55 was attached on the battery lid 14, was covered with the outer tube 50, and the outer tube 50 was heated and shrunk, for example, by applying hot air to the outer tube 50, and the outer tube 50 was brought into close contact with the outer surface of the outer can 11.

[0097] In this manner, a secondary battery 1 of Example 1 was obtained.

[0098] Comparative Example 1 As Comparative Example 1, a secondary battery was fabricated in which one electrode winding body 20 was provided instead of the two divided electrode winding bodies 20U and 20L.

[0099] [Evaluation of battery characteristics] The discharge load characteristics were examined for each of the secondary batteries obtained as described above in Example 1 and Comparative Example 1. The results are shown in Figures 11A and 11B.

[0100] FIG. 11A is a characteristic diagram showing the relationship between discharge capacity and discharge voltage in the secondary battery of Example 1. FIG. 11B is a characteristic diagram showing the relationship between discharge capacity and discharge voltage in the secondary battery of Comparative Example 1. In FIGS. 11A and 11B, the horizontal axis indicates discharge capacity [%] and the vertical axis indicates discharge voltage [V]. However, the discharge capacity on the horizontal axis is normalized with the discharge capacity at 1C, which is the rated current, set as 100%. When the secondary batteries of Example 1 and Comparative Example 1 were discharged at 1C, 10C, and 15C, respectively, the changes shown in FIGS. 11A and 11B were observed.

[0101] 11A and 11B, there was no significant difference in behavior between Example 1 and Comparative Example 1 in the 1 C discharge, but the difference between the two became evident when discharging at 10 C and 15 C. In other words, when the output was increased, Example 1 was able to suppress the drop in discharge voltage more than Comparative Example 1.

[0102] From the above results, it has been confirmed that the secondary battery of the present disclosure can reduce internal resistance, thereby reducing the amount of heat generated inside the secondary battery and enabling high-output discharge.

[0103] 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 first end faces on which the positive electrodes of the two electrode winding bodies are exposed are arranged to face each other, but the present disclosure is not limited to this. The second end faces on which the negative electrodes of the two electrode winding bodies are exposed may be arranged to face each other.

[0104] 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.

[0105] 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.

[0106] The present disclosure may take the following forms. <1> first and second electrode winding bodies each having a winding structure in which a laminate including a first electrode, a second electrode, and a separator is wound along a longitudinal direction of the laminate, and each having a through hole penetrating in a width direction of the laminate perpendicular to the longitudinal direction; an exterior body that houses the first and second electrode winding bodies; Equipped with each of the first and second electrode winding bodies has a first end surface from which the first electrode is exposed and a second end surface from which the second electrode is exposed, at both ends in a width direction of the laminate; The first and second electrode winding bodies are arranged in the width direction of the laminate so that the first end faces of the first and second electrode winding bodies face each other. Secondary battery. <2> The first and second electrode winding bodies are arranged so that the through holes of each of the first and second electrode winding bodies are in communication with each other. the above <1> The secondary battery described herein. <3> The exterior body is first and second bottom portions that face each other in the longitudinal direction of the laminate, sandwiching the first and second electrode winding bodies therebetween; a wall portion located between the first bottom portion and the second bottom portion and surrounding the first and second electrode winding bodies; having the first bottom portion faces the second end surface of the first electrode winding body, The second bottom portion faces the second end surface of the second electrode winding body. the above <1> or <2> The secondary battery described herein. <4> first and second first electrode current collectors facing the first end faces of the first and second electrode winding bodies, respectively; first and second electrode current collectors facing the second end faces of the first and second electrode winding bodies, respectively; Further equipped the above <1> from <3> 13. The secondary battery according to claim 12, <5> The first electrode is a first electrode active material layer extending in both the longitudinal direction and the width direction; a first electrode current collector including a first electrode covered region covered with the first electrode active material layer and a first electrode exposed region extending in the width direction from the first electrode active material layer; having The first end surface is formed by bending an edge portion of the first electrode exposed region toward the through hole in a rolled state. the above <4> The secondary battery described herein. <6> At least a part of the first electrode exposed region constitutes the first end surface and is connected to one of the first electrode current collector plates. the above <5> The secondary battery described herein. <7> The second electrode is a second electrode active material layer extending in both the longitudinal direction and the width direction; a second electrode current collector including a second electrode covered region covered with the second electrode active material layer and a second electrode exposed region extending in the width direction from the second electrode active material layer; having The second end surface is formed by bending an edge portion of the second electrode exposed region toward the through hole in a wound state. the above <5> or <6> The secondary battery described herein. <8> At least a part of the second electrode exposed region constitutes the second end surface and is connected to the first second electrode current collector plate or the second second electrode current collector plate. the above <7> The secondary battery according to claim 1. <9> the exterior body has a lid portion electrically connected to the first and second first electrode collector plates and a housing portion electrically connected to the first and second second electrode collector plates, the housing portion includes a bottom portion and a wall portion that is erected in the width direction along an outer edge of the bottom portion so as to surround the first and second electrode winding bodies and that includes an open end portion on the opposite side to the bottom portion, the open end portion being open so that the first and second electrode winding bodies can be inserted therethrough; The cover closes the open end of the storage section. the above <4> The secondary battery described herein. <10> the first second electrode current collector is provided between the lid portion and the second end surface of the first electrode winding body, The second electrode current collector is provided between the bottom and the second end surface of the second electrode winding body. the above <9> The secondary battery described herein. <11> a first connection member that electrically connects the lid portion to the first and second first electrode collector plates, The first connection member is inserted into the through hole of the first electrode winding body. the above <9> or <10> The secondary battery described herein. <12> The first connection member is a cylindrical member whose height direction is the width direction of the laminate, or a partially cylindrical member whose height direction is the width direction of the laminate and in which a slit is provided in a part of the cylindrical member. the above <11> The secondary battery according to claim 1. <13> Further, a second connection member is provided to electrically connect the housing portion and the first second electrode current collector plate, The second connecting member is an annular member that is connected to the inner surface of the housing portion. the above <9> from <12> 13. The secondary battery according to claim 12, <14> the above <1> from <13> A secondary battery according to any one of the above items, A control unit that controls the secondary battery; An exterior member that encapsulates the secondary battery; A battery pack having [Explanation of symbols]

[0107] 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, 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, 23 A...first separator member, 23B...second separator member, 24...positive electrode current collector plate, 25...negative electrode current collector plate, 26...through hole, 27...intermediate positive electrode current collector plate, 28...connecting member, 29...connecting member, 30...safety valve mechanism, 31, 33...fan-shaped portion, 32, 34...strip-shaped portion, 35, 36...opening, 37...protrusion, 41...first end surface, 42...second end surface, 50...outer tube, 55...washer, 61U, 61L...positive electrode tab, 62U, 62L...negative electrode tab, 101...insulating layer, CL...central axis.

Claims

1. first and second electrode winding bodies each having a winding structure in which a laminate including a first electrode, a second electrode, and a separator is wound along a longitudinal direction of the laminate, and each having a through hole penetrating the laminate in a width direction perpendicular to the longitudinal direction; an exterior body that houses the first and second electrode winding bodies; Equipped with each of the first and second electrode winding bodies has a first end surface from which the first electrode is exposed and a second end surface from which the second electrode is exposed, at both ends in a width direction of the laminate; The first and second electrode winding bodies are arranged in the width direction of the laminate so that the first end faces of the first and second electrode winding bodies face each other. Secondary battery.

2. The first and second electrode winding bodies are arranged so that the through holes of each of the first and second electrode winding bodies are in communication with each other. The secondary battery according to claim 1 .

3. The exterior body is first and second bottom portions that face each other in a longitudinal direction of the laminate, sandwiching the first and second electrode winding bodies therebetween; a wall portion located between the first bottom portion and the second bottom portion and surrounding the first and second electrode winding bodies; having the first bottom portion faces the second end surface of the first electrode winding body, The second bottom portion faces the second end surface of the second electrode winding body. The secondary battery according to claim 1 .

4. first and second first electrode current collectors facing the first end faces of the first and second electrode winding bodies, respectively; first and second electrode current collectors facing the second end faces of the first and second electrode winding bodies, respectively; Further equipped The secondary battery according to claim 1 .

5. The first electrode is a first electrode active material layer extending in both the longitudinal direction and the width direction; a first electrode current collector including a first electrode covered region covered with the first electrode active material layer and a first electrode exposed region extending in the width direction from the first electrode active material layer; having The first end surface is formed by bending an edge portion of the first electrode exposed region toward the through hole in a rolled state. The secondary battery according to claim 4.

6. At least a part of the first electrode exposed region constitutes the first end surface and is connected to one of the first electrode current collector plates. The secondary battery according to claim 5.

7. The second electrode is a second electrode active material layer extending in both the longitudinal direction and the width direction; a second electrode current collector including a second electrode covered region covered with the second electrode active material layer and a second electrode exposed region extending in the width direction from the second electrode active material layer; having The second end surface is formed by bending an edge portion of the second electrode exposed region toward the through hole in a wound state. The secondary battery according to claim 5.

8. At least a part of the second electrode exposed region constitutes the second end surface and is connected to the first second electrode collector plate or the second second electrode collector plate. The secondary battery according to claim 7.

9. the exterior body has a lid portion electrically connected to the first and second first electrode collector plates and a housing portion electrically connected to the first and second second electrode collector plates, the housing portion includes a bottom portion and a wall portion that is erected in the width direction along an outer edge of the bottom portion so as to surround the first and second electrode winding bodies and that includes an open end portion on the opposite side to the bottom portion, the open end portion being open so that the first and second electrode winding bodies can be inserted therethrough; The cover closes the open end of the storage section. The secondary battery according to claim 4.

10. the first second electrode current collector is provided between the lid portion and the second end surface of the first electrode winding body, The second electrode current collector is provided between the bottom and the second end surface of the second electrode winding body. The secondary battery according to claim 9.

11. a first connection member electrically connecting the lid portion to the first and second first electrode collector plates; The first connection member is inserted into the through hole of the first electrode winding body. The secondary battery according to claim 9.

12. The first connection member is a cylindrical member having a height direction that is the width direction of the laminate, or a partially cylindrical member having a slit provided in a part of the cylindrical member having a height direction that is the width direction of the laminate. The secondary battery according to claim 11.

13. A second connection member electrically connecting the housing portion and the first second electrode current collector plate, The second connecting member is an annular member that is connected to the inner surface of the housing portion. The secondary battery according to claim 9.

14. The secondary battery according to any one of claims 1 to 13, A control unit that controls the secondary battery; An exterior member that encapsulates the secondary battery; A battery pack having

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