Rechargeable batteries and battery packs

Abstract

Provided is a secondary battery which has excellent safety. According to the present invention, an electrode wound body has a first end surface that faces a positive electrode current collector plate in the height direction, and a second end surface that faces a negative electrode current collector plate in the height direction. A positive electrode comprises: a positive electrode current collector covered part in which a positive electrode current collector is covered with a positive electrode active material layer; and a positive electrode current collector exposed part in which the positive electrode current collector is exposed without being covered with the positive electrode active material layer. At least a part of the positive electrode current collector exposed part constitutes the first end surface and is connected to the positive electrode current collector plate. A negative electrode comprises: a negative electrode current collector covered part in which a negative electrode current collector is covered with a negative electrode active material layer; and a negative electrode current collector exposed part in which the negative electrode current collector is exposed without being covered with the negative electrode active material layer. At least a part of the negative electrode current collector exposed part constitutes the second end surface and is connected to the negative electrode current collector plate. The positive electrode comprises an insulating layer which covers a facing portion of the positive electrode current collector exposed part, the facing portion facing the negative electrode active material layer with a separator being interposed therebetween. The elongation of the insulating layer is 180% or more.

Description

Technical Field

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

Background Art

[0002] Due to the widespread use of various electronic devices such as mobile phones, the development of secondary batteries is underway as a power source that is small and lightweight and can obtain a high energy density. This secondary battery includes a battery element housed inside an exterior member, and various studies have been made regarding the configuration of the secondary battery (see, for example, Patent Document 1).

[0003] In Patent Document 1, a structure called a so-called tabless structure is adopted, and a secondary battery that reduces internal resistance and enables charge and discharge with a relatively large current has been proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] Various studies have been made to improve the performance of secondary batteries. However, there is room for improvement in the safety of secondary batteries.

[0006] Therefore, a secondary battery with excellent safety is desired.

[0007] A secondary battery according to one embodiment of the present disclosure comprises a positive electrode current collector plate, a negative electrode current collector plate, and an electrode winding body disposed between the positive electrode current collector plate and the negative electrode current collector plate, having a through hole penetrating in the height direction, and in which a laminate including a positive electrode, a negative electrode, and a separator is wound. The electrode winding body has a first end face facing the positive electrode current collector plate in the height direction and a second end face facing the negative electrode current collector plate in the height direction. The positive electrode includes a positive electrode current collector and a positive electrode active material layer and an insulating layer covering a portion of the positive electrode current collector. The positive electrode includes a positive electrode current collector covering portion in which the positive electrode current collector is covered by the positive electrode active material layer, and a positive electrode current collector exposed portion in which the positive electrode current collector is exposed without being covered by the positive electrode active material layer. At least a portion of the positive electrode current collector exposed portion constitutes the first end face and is connected to the positive electrode current collector plate. The negative electrode includes a negative electrode current collector and a negative electrode active material layer covering a portion of the negative electrode current collector. The negative electrode includes a negative electrode current collector covering portion, where the negative electrode current collector is covered by a negative electrode active material layer, and a negative electrode current collector exposed portion, where the negative electrode current collector is not covered by the negative electrode active material layer. At least a portion of the negative electrode current collector exposed portion constitutes a second end face and is connected to the negative electrode current collector plate. The insulating layer covers the portion of the positive electrode current collector exposed portion that faces the negative electrode active material layer across the separator, and has an elongation rate of 180% or more.

[0008] In one embodiment of the secondary battery of this disclosure, the elongation rate of the insulating layer covering the portion of the positive electrode current collector exposed that faces the negative electrode active material layer across the separator is 180% or more. Therefore, even if foreign matter such as metal powder is mixed between the insulating layer and the negative electrode active material layer, it is possible to effectively prevent the insulating layer from rupturing or cracking. Therefore, a secondary battery according to one embodiment of the present disclosure can ensure excellent safety.

[0009] Furthermore, the effects of this disclosure are not necessarily limited to those described herein, and may include those described herein. Any of the effects of the series of effects related to this disclosure described herein may be used. [Brief explanation of the drawing]

[0010] [Figure 1]Figure 1 is a cross-sectional view showing an example of a vertical cross-sectional structure along the height direction of a secondary battery in one embodiment of the present disclosure. [Figure 2] Figure 2 is a schematic diagram showing one example of the configuration of a laminate including the positive electrode, negative electrode, and separator shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view showing one example of the horizontal cross-sectional structure of the electrode winding body shown in Figure 1. [Figure 4A] Figure 4A is an exploded view of the positive electrode shown in Figure 1. [Figure 4B] Figure 4B is a cross-sectional view of the positive electrode shown in Figure 1. [Figure 5A] Figure 5A is an unfolded view of the negative electrode shown in Figure 1. [Figure 5B] Figure 5B is a cross-sectional view of the negative electrode shown in Figure 1. [Figure 6] Figure 6 is an enlarged cross-sectional view showing an example of a configuration of a part of the vertical cross-sectional structure of the secondary battery shown in Figure 1. [Figure 7A] Figure 7A is a plan view of the positive electrode current collector plate shown in Figure 1. [Figure 7B] Figure 7B is a plan view of the negative electrode current collector plate shown in Figure 1. [Figure 8] Figure 8 is a perspective view illustrating the manufacturing process of the secondary battery shown in Figure 1. [Figure 9] Figure 9 is a block diagram showing the circuit configuration of a battery pack using a secondary battery according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0011] Hereinafter, one embodiment of this disclosure will be described in detail with reference to the drawings. The order of description is as follows. 1. Secondary battery 1-1. Composition 1-2.Operation 1-3. Manufacturing method 1-4. Action and Effects 2. Application Examples 2-1. Battery pack 2-2. Energy Storage System

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

[0013] In the present embodiment, a cylindrical lithium-ion secondary battery having a cylindrical appearance will be exemplified and described. 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 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. Hereinafter, the case where the battery capacity is obtained by utilizing the occlusion and release of the electrode reactant will be described. This secondary battery includes an electrolyte together with a positive electrode and a negative electrode. In this secondary battery, in order to prevent the electrode reactant from depositing on the surface of the negative electrode during charging, the charging capacity of the negative electrode is larger than the discharging capacity of the positive electrode. 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. Specifically, it is a light metal such as an alkali metal and an alkaline earth metal. The alkali metals include lithium, sodium, potassium, etc., and the alkaline earth metals include beryllium, magnesium, calcium, etc.

[0016] Hereinafter, the case where the electrode reactant is lithium will be taken as an example. A secondary battery in which the battery capacity is obtained by utilizing the occlusion and release of lithium is a so-called lithium-ion secondary battery. In this lithium-ion secondary battery, lithium is occluded and released in an ionic state.

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

[0018] Specifically, the secondary battery 1 includes, for example, a pair of insulating plates 12 and 13, an electrode winding body 20, a positive electrode current collector plate 24 as a first electrode current collector plate, and a negative electrode current collector plate 25 as a second electrode current collector plate, all inside an outer casing 11. The electrode winding body 20 is a structure in which a positive electrode 21 and a negative electrode 22 are stacked and wound together via a separator 23. The electrode winding body 20 is impregnated with an electrolyte, which is a liquid electrolyte. The secondary battery 1 may further include one or more of the following inside the outer casing 11: a thermal resistance (PTC) element and a reinforcing member.

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

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

[0021] (Washer 55) A washer 55 is provided in the gap between the outer tube 50 and the bent portion 11P of the outer can 11. The washer 55 is an insulating ring member having an opening 55K in the central region in a plane perpendicular to the height direction. The opening 55K is located in the central region of the battery cover 14. Convex part It is inserted through. For example, a black modified polyphenylene ether can be used as the constituent material of the washer 55.

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

[0023] (Crimping structure 11R) At the open end 11N of the outer casing 11, a crimped structure 11R is formed, in which, for example, the battery cover 14 and the safety valve mechanism 30 are crimped together via a gasket 15. The battery cover 14 seals the outer casing 11 with the electrode winding 20 and the like housed inside. The crimped structure 11R is a so-called crimp structure and has a bent portion 11P that functions as a so-called crimped portion.

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

[0025] (Gasket 15) The gasket 15 is a sealing member mainly interposed between the folded portion 11P of the outer can 11 and the battery cover 14. The gasket 15 seals the gap between the folded portion 11P and the battery cover 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 examples include polymer materials such as polybutylene terephthalate (PBT) and polypropylene (PP). Among these, polybutylene terephthalate is preferred as the insulating material. This is because it sufficiently seals the gap between the folded portion 11P and the battery cover 14 while electrically separating the outer can 11 and the battery cover 14 from each other.

[0026] (Safety valve mechanism 30) The safety valve mechanism 30 is primarily designed to release the internal pressure inside the outer can 11 by releasing the sealed state of the outer can 11 as needed when the internal pressure rises. The causes of the rise in internal pressure inside the outer can 11 include, for example, gases generated due to the decomposition reaction of the electrolyte during charging and discharging. In addition, the internal pressure inside the outer can 11 may also rise due to external heating.

[0027] (Electrode winding body 20) The electrode winding 20 is positioned between the positive electrode current collector plate 24 and the negative electrode current collector plate 25. The electrode winding 20 has an upper end face 41 that faces the positive electrode current collector plate 24 in the height direction, and a negative electrode current collector in the height direction. It has a plate 25 and a lower end face 42 facing it. The electrode winding 20 is a power generation element that carries out a charge-discharge reaction and is housed inside the outer casing 11. The electrode winding 20 includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte which is a liquid electrolyte.

[0028] Figure 2 is an unfolded view of the electrode winding 20, schematically representing a part of the laminate S20 which includes a positive electrode 21 as the first electrode, a negative electrode 22 as the second electrode, and a separator 23. In the laminate S20 obtained by unfolding the electrode winding 20, the positive electrode 21 and the negative electrode 22 are stacked on top of each other via the separator 23. The separator 23 has, for example, two base materials, namely a first separator member 23A and a second separator member 23B. Therefore, the electrode winding 20 has a four-layer laminate S20 in which the positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are stacked in that 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-axis direction as the short side and the L-axis direction as the long side.

[0029] As shown in Figure 3, the electrode winding body 20 is formed by winding the laminate S20 around a through hole 26 along a central axis CL extending in the Z-axis direction, such that it forms a spiral shape in a horizontal cross-section perpendicular to the Z-axis direction. At this time, the laminate S20 is wound in an orientation where the W-axis direction approximately coincides with the Z-axis direction. Note that Figure 3 shows one example configuration along a horizontal cross-section perpendicular to the Z-axis direction of the electrode winding body 20. However, in Figure 3, the separator 23 is omitted to improve visibility. The electrode winding body 20 has a generally cylindrical appearance. The positive electrode 21 and the negative electrode 22 are wound while maintaining a state of facing each other via the separator 23. A through hole 26 is formed in the center of the electrode winding body 20 as an internal space. The through hole 26 is a hole for inserting the winding core for assembling the electrode winding body 20 and the 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.

[0030] The positive electrode 21, negative electrode 22, and separator 23 are wound such that the separator 23 is positioned on the outermost circumference and innermost circumference of the electrode winding body 20, respectively. Furthermore, at the outermost circumference of the electrode winding body 20, the negative electrode 22 is positioned outside the positive electrode 21. That is, as shown in Figure 3, the outermost positive electrode portion 21out of the positive electrode 21 contained in the electrode winding body 20 is positioned inside the outermost negative electrode portion 22out of the negative electrode 22 contained in the electrode winding body 20. Here, the outermost positive electrode portion 21out is the outermost one turn of the positive electrode 21 in the electrode winding body 20. The outermost negative electrode portion 22out is the outermost one turn of the negative electrode 22 in the electrode winding body 20. On the other hand, at the innermost circumference of the electrode winding body 20, the negative electrode 22 is positioned inside the positive electrode 21. In other words, as shown in Figure 3, the innermost negative electrode portion 22in, located at the innermost circumference of the negative electrode 22 included in the electrode winding body 20, is located inside the innermost positive electrode portion 21in, located at the innermost circumference of the positive electrode 21 included in the electrode winding body 20. Here, the innermost positive electrode portion 21in is the innermost one turn of the positive electrode 21 in the electrode winding body 20. The innermost negative electrode portion 22in is the innermost one turn of the negative electrode 22 in the electrode winding body 20. The number of turns of the positive electrode 21, the negative electrode 22, and the separator 23 are not particularly limited and can be set arbitrarily.

[0031] Figure 4A is an unfolded view of the positive electrode 21, schematically representing its state before winding. Figure 4B shows the cross-sectional configuration of the positive electrode 21. Note that Figure 4B shows the cross-section in the direction of the arrow along the IVB-IVB line shown in Figure 4A. The positive electrode 21 includes, for example, a positive electrode current collector 21A, a positive electrode active material layer 21B that covers a part of the positive electrode current collector 21A, and an insulating layer 21C. Note that the insulating layer 21C is omitted in Figure 1. The positive electrode active material layer 21B may be provided on only one side of the positive electrode current collector 21A, or on both sides of the positive electrode current collector 21A. Figure 4B shows the case where the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A. More specifically, the positive electrode current collector 21A includes an inner circumferential surface 21A1 of the positive electrode current collector facing the winding center side of the electrode winding body 20, i.e., the central axis CL, and an outer circumferential surface 21A2 of the positive electrode current collector facing the opposite side of the winding center side of the electrode winding body 20, i.e., the side opposite to the inner circumferential surface 21A1. The positive electrode 21 has a positive electrode active material layer 21B, which includes an inner circumferential active material layer 21B1 that covers at least a portion of the inner circumferential surface 21A1 of the positive electrode current collector, and an outer circumferential active material layer 21B2 that covers at least a portion of the outer circumferential surface 21A2 of the positive electrode current collector. In this specification, the inner circumferential active material layer 21B1 and the outer circumferential active material layer 21B2 may be referred to collectively as the positive electrode active material layer 21B without distinction.

[0032] The positive electrode 21 has a positive electrode current collector covering portion 211 in which the positive electrode current collector 21A is covered with a positive electrode active material layer 21B, and a positive electrode current collector exposed portion 212 in which the positive electrode current collector 21A is exposed without being covered by the positive electrode active material layer 21B. As shown in Figure 4A, the positive electrode current collector covering portion 211 and the positive electrode current collector exposed portion 212 each extend along the L-axis direction, which is the longitudinal direction of the positive electrode 21, from the central axis side edge 21E1 to the outer circumference side edge 21E2 of the positive electrode 21. Here, the L-axis direction corresponds to the winding direction of the electrode winding body 20. That is, in the positive electrode 21, in the winding direction of the electrode winding body 20, the positive electrode current collector 21A is covered with the positive electrode active material layer 21B from the central axis side edge 21E1 to the outer circumference side edge 21E2 of the positive electrode 21. The positive electrode current collector covering portion 211 and the positive electrode current collector exposed portion 212 are adjacent to each other in the W-axis direction, which is the short-side direction of the positive electrode 21. The W-axis direction substantially coincides with the central axis CL. Figure 3 As shown, in the electrode winding body 20, the central axis-side end edge 21E1 of the innermost positive electrode portion 21in is positioned further inward than the central axis-side end edge 22E1 of the innermost negative electrode portion 22in. Furthermore, the positive electrode 21 has a lower end edge 21E3 that extends in the L-axis direction on the lower side of the electrode winding body 20. In Figures 4A and 4B, the positive electrode current collector 21A is schematically shown as extending linearly along the W-axis direction. However, in reality, the positive electrode edge portion 212E of the exposed positive electrode current collector portion 212 is bent toward the central axis CL as shown in Figure 1 and is connected to the positive electrode current collector plate 24. That is, the W-axis direction end of the exposed positive electrode current collector portion 212 constitutes the upper end face 41 and is connected to the positive electrode current collector plate 24 (see Figure 1). The upper end face 41 is formed by bending the positive electrode edge 212E of the positive electrode current collector exposed portion 212 toward the through hole 26 while it is wound around the positive electrode current collector.

[0033] It is preferable that an insulating layer 21C be provided near the boundary between the positive electrode current collector covering portion 211 and the positive electrode current collector exposed portion 212. The insulating layer 21C, like the positive electrode current collector covering portion 211 and the positive electrode current collector exposed portion 212, is preferable to extend along the L-axis direction from the central axis side edge 21E1 to the outer circumference side edge 21E2 of the electrode winding body 20. Furthermore, it is preferable that the insulating layer 21C be bonded to at least one of the first separator member 23A and the second separator member 23B. This is because it prevents misalignment between the positive electrode 21 and the separator 23. The detailed configuration of the positive electrode 21 will be described later.

[0034] Figure 5A is an unfolded view of the negative electrode 22, schematically representing its state before winding. Figure 5B shows the cross-sectional configuration of the negative electrode 22. Note that Figure 5B shows the cross-section in the direction of the arrow along the VB-VB line shown in Figure 5A. The negative electrode 22 includes, for example, a negative electrode current collector 22A and a negative electrode active material layer 22B that covers a part of the negative electrode current collector 22A. The negative electrode active material layer 22B may be provided on, for example, only one side of the negative electrode current collector 22A, or on both sides of the negative electrode current collector 22A. Figure 5B shows the case where the negative electrode active material layer 22B is provided on both sides of the negative electrode current collector 22A. More specifically, the negative electrode current collector 22A includes an inner circumferential surface 22A1 of the negative electrode current collector facing the winding center side of the electrode winding body 20, i.e., the central axis CL, and an outer circumferential surface 22A2 of the negative electrode current collector facing the opposite side of the winding center side of the electrode winding body 20, i.e., the side opposite to the inner circumferential surface 22A1 of the negative electrode current collector. The negative electrode 22 has a negative electrode active material layer 22B, which includes an inner circumferential active material layer 22B1 that covers at least a portion of the inner circumferential surface 22A1 of the negative electrode current collector, and an outer circumferential active material layer 22B2 that covers at least a portion of the outer circumferential surface 22A2 of the negative electrode current collector. In this specification, the inner circumferential active material layer 22B1 and the outer circumferential active material layer 22B2 may be referred to collectively as the negative electrode active material layer 22B without distinction.

[0035] The negative electrode 22 has a negative electrode current collector covering portion 221 in which the negative electrode current collector 22A is covered with a negative electrode active material layer 22B, and a negative electrode current collector exposed portion 222 in which the negative electrode current collector 22A is exposed without being covered by the negative electrode active material layer 22B. As shown in Figure 5A, the negative electrode current collector covering portion 221 and the negative electrode current collector exposed portion 222 each extend along the L-axis direction, which is the longitudinal direction of the negative electrode 22. The negative electrode current collector exposed portion 222 extends from the central axis side edge 22E1 to the outer circumference side edge 22E2 of the negative electrode 22 in the winding direction of the electrode winding body 20. In contrast, the negative electrode current collector covering portion 221 is not provided at the central axis side edge 22E1 and the outer circumference side edge 22E2 of the negative electrode 22. As shown in Figure 5A, a portion of the exposed negative electrode current collector portion 222 is formed to sandwich the negative electrode current collector covering portion 221 in the L-axis direction, which is the longitudinal direction of the negative electrode 22. Specifically, the exposed negative electrode current collector portion 222 includes a first portion 222A, a second portion 222B, and a third portion 222C. The negative electrode 22 also has a lower end edge 22E3 that extends in the L-axis direction on the lower side of the electrode winding body 20. The first portion 222A is provided adjacent to the negative electrode current collector covering portion 221 in the W-axis direction and extends in the L-axis direction from the central axis side end edge 22E1 to the outer circumference side end edge 22E2 of the negative electrode 22. The second portion 222B and the third portion 222C are provided to sandwich the negative electrode current collector covering portion 221 in the L-axis direction. The first portion 222A is located near the lower edge 22E3 of the negative electrode 22. The second portion 222B is located near, for example, the central axis side edge 22E1 of the negative electrode 22, and the third portion 222C is located near the outer circumference side edge 22E2 of the negative electrode 22. In Figures 5A and 5B, the negative electrode current collector 22A is schematically shown as extending linearly along the W-axis. However, in reality, the negative electrode edge portion 222E of the exposed portion 222 of the negative electrode current collector is bent toward the central axis CL as shown in Figure 1 and connected to the negative electrode current collector plate 25. That is, the W-axis side end of the exposed portion 222 of the negative electrode current collector constitutes the lower end face 42 and is connected to the negative electrode current collector plate 25 (see Figure 1). The lower end face 42 is formed by bending the negative electrode edge portion 222E of the exposed portion 222 of the negative electrode current collector toward the through hole 26 when it is wound up. The detailed configuration of the negative electrode 22 will be described later.

[0036] In the laminate S20 of the electrode winding body 20, the positive electrode 21 and the negative electrode 22 are laminated via the separator 23 such that the positive electrode current collector exposed portion 212 and the first portion 222A of the negative electrode current collector exposed portion 222 face each other along the W-axis direction which is the width direction. The electrode winding body 20 is configured such that the end of the separator 23 is fixed by attaching a fixing tape 46 to its side surface portion 45, thereby preventing unwinding.

[0037] In the secondary battery 1, as shown in FIG. 2, when the width of the positive electrode current collector exposed portion 212 is A and the width of the first portion 222A of the negative electrode current collector exposed portion 222 is B, it is preferable that A > B. For example, when the width A = 7 (mm), the width B = 4 (mm). Also, among the positive electrode current collector exposed portion 212, the width of the portion protruding from the outer edge in the width direction of the separator 23 is C, and among the first portion 222A of the negative electrode current collector exposed portion 222, the width of part portion protruding from the outer edge on the opposite side of 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). The numerical values of the widths A to D and the magnitude relationship of the numerical values of the widths A to D described here are merely examples, and the present disclosure is not limited to the numerical values and the magnitude relationship of the numerical values described here. Also, the length in the Z-axis direction of the negative electrode active material layer 22B (negative electrode current collector covering portion 221) is longer than the length in the Z-axis direction of the positive electrode active material layer 21B (positive electrode current collector covering portion 211). That is, the width W22B of the negative electrode active material layer 22B is wider than the width W21B of the positive electrode active material layer 21B (W21B < W22B). This is to prevent the lithium ions released from the positive electrode 21 from depositing on the surface of the negative electrode 22 by making all portions of the positive electrode active material layer 21B face the negative electrode active material layer 22B through the separator 23.

[0038] As shown in Figure 1, at the upper part of the secondary battery 1, multiple positive electrode edges 212E of the electrode winding body 20, which are adjacent in the radial direction (R direction) of the exposed positive electrode current collector portion 212 wound around the central axis CL, are bent toward the central axis CL so as to overlap each other, forming the upper end face 41 of the electrode winding body 20. Similarly, at the lower part of the secondary battery 1, multiple negative electrode edges 222E of the exposed negative electrode current collector portion 222, which are wound around the central axis CL, are bent toward the central axis CL so as to overlap each other, forming the lower end face 42 of the electrode winding body 20. Therefore, multiple positive electrode edges 212E of the exposed positive electrode current collector portion 212 are gathered at the upper end face 41 of the electrode winding body 20, and multiple negative electrode edges 222E of the exposed negative electrode current collector portion 222 are gathered at the lower end face 42 of the electrode winding body 20. Multiple positive electrode edges 212E, which are bent toward the central axis CL, are flat surfaces in order to improve contact between the positive electrode current collector plate 24 for extracting current and the positive electrode edge 212E. Similarly, multiple negative electrode edges 222E, which are bent toward the central axis CL, are flat surfaces in order to improve contact between the negative electrode current collector plate 25 for extracting current and the negative electrode edge 222E. Note that the term "flat surface" here includes not only perfectly flat surfaces but also surfaces with some irregularities or surface roughness to the extent that the exposed portion 212 of the positive electrode current collector and the exposed portion 222 of the negative electrode current collector can be joined to the positive electrode current collector plate 24 and the negative electrode current collector plate 25, respectively.

[0039] The positive electrode current collector 21A is made of, for example, aluminum foil, as will be described later. On the other hand, the negative electrode current collector 22A is made of, for example, copper foil, as will be described later. In this case, the positive electrode current collector 21A is softer than the negative electrode current collector 22A. That is, the Young's modulus of the exposed portion 212 of the positive electrode current collector is lower than the Young's modulus of the exposed portion 222 of the negative electrode current collector. For this reason, in one embodiment, it is more preferable that the relationship A>B and C>D holds with respect to widths A to D. In that case, when the exposed portion 212 of the positive electrode current collector and the exposed portion 222 of the negative electrode current collector are bent simultaneously from both poles with the same pressure, the height measured from the tip of the separator 23 of the bent portion may be about the same for the positive electrode 21 and the negative electrode 22. At this time, multiple positive electrode edges 212E (Figure 1) of the exposed portion 212 of the positive electrode current collector are bent and overlap appropriately. Therefore, the exposed portion 212 of the positive electrode current collector and the positive electrode current collector plate 24 can be easily joined. Similarly, the multiple negative electrode edges 222E (Figure 1) of the exposed portion 222 of the negative electrode current collector are bent and overlap appropriately. Therefore, the exposed portion 222 of the negative electrode current collector and the negative electrode current collector plate 25 can be easily joined. Joining here means, for example, joining by laser welding, but the joining method is not limited to laser welding.

[0040] Figure 6 is an enlarged cross-sectional view showing an example of a configuration of a part of the vertical cross-sectional structure of the secondary battery 1 shown in Figure 1. As shown in Figures 2 and 6, the portion FP of the positive electrode 21's positive electrode current collector exposed portion 212 that faces the negative electrode 22 across the separator 23 is covered by an insulating layer 21C. The insulating layer 21C has a width of, for example, 3 mm in the W-axis direction. The insulating layer 21C covers the entire area of ​​the positive electrode 21's positive electrode current collector exposed portion 212 that faces the negative electrode current collector covering portion 221 of the negative electrode 22 via the separator 23. The insulating layer 21C can effectively prevent internal short circuits in the secondary battery 1 when, for example, foreign matter enters between the negative electrode current collector covering portion 221 and the positive electrode current collector exposed portion 212. Furthermore, the insulating layer 21C absorbs the impact when the secondary battery 1 is subjected to shock, effectively preventing bending of the exposed portion 212 of the positive electrode current collector and short-circuiting between the exposed portion 212 of the positive electrode current collector and the negative electrode 22.

[0041] The insulating layer 21C covers the opposing portion FP (described later) of the positive electrode current collector exposed portion 212 that faces the negative electrode active material layer 22B (described later) with the separator 23 in between, and has an elongation rate of, for example, 180% or more. Furthermore, the insulating layer 21C is preferably a resin containing modified PVDF (polyvinylidene fluoride) or copolymer PVDF. This is because, by containing modified PVDF or copolymer PVDF in the insulating layer 21C, the insulating layer 21C can swell due to the solvent contained in the electrolyte, for example, and can adhere well to the separator 23. Also, by containing modified PVDF or copolymer PVDF in the insulating layer 21C, a better elongation rate can be obtained. Examples of constituent materials for the insulating layer 21C include PVDF that has been modified or copolymerized with TFE (tetrafluoroethylene), HFP (hexafluoropropylene), acrylic acid, and maleic acid.

[0042] (Insulating tape 53, 54) The secondary battery 1 may further have insulating tapes 53, 54 in the gap between the outer casing 11 and the electrode winding 20. The exposed positive electrode current collector portion 212 and the exposed negative electrode current collector portion 222, which are concentrated at the upper end face 41 and the lower end face 42, are conductors such as exposed metal foil. Therefore, if the exposed positive electrode current collector portion 212 and the exposed negative electrode current collector portion 222 are close to the outer casing 11, a short circuit may occur between the positive electrode 21 and the negative electrode 22 via the outer casing 11. Also, a short circuit may occur when the positive electrode current collector plate 24 on the upper end face 41 is close to the outer casing 11. For this reason, it is preferable to provide insulating tapes 53, 54 as insulating members. The insulating tapes 53, 54 are, for example, adhesive tapes in which the base material layer is made of one of polypropylene, polyethylene terephthalate, or polyimide, and the base material layer has an adhesive layer on one side of the base material layer. In order to avoid reducing the volume of the electrode winding body 20 by installing the insulating tapes 53 and 54, the insulating tapes 53 and 54 are positioned so as not to overlap with the fixing tape 46 attached to the side portion 45, and the thickness of the insulating tapes 53 and 54 is set to be less than or equal to the thickness of the fixing tape 46.

[0043] (Positive electrode current collector plate 24 and negative electrode current collector plate 25) In a typical lithium-ion secondary battery, for example, leads for current extraction are welded to one point each on the positive and negative electrodes. However, this results in high internal resistance of the lithium-ion secondary battery, causing it to overheat and become hot during discharge, making it unsuitable for high-rate discharge. Therefore, in the secondary battery 1 of this embodiment, the positive electrode current collector plate 24 is positioned facing the upper end face 41, and the negative electrode current collector plate 25 is positioned facing the lower end face 42. The positive electrode current collector covering portion 211 on the upper end face 41 and the positive electrode current collector plate 24 are welded at multiple points, and the negative electrode current collector covering portion 221 on the lower end face 42 and the negative electrode current collector plate 25 are welded at multiple points. This reduces the internal resistance of the secondary battery 1. The fact that the upper end face 41 and the lower end face 42 are flat surfaces, as described above, also contributes to the reduction in resistance. The positive electrode current collector plate 24 is provided between the battery cover 14 and the upper end face 41. The positive electrode current collector plate 24 is electrically connected to the battery cover 14, for example, via a safety valve mechanism 30. The negative electrode current collector plate 25 is provided between the bottom 11B and the lower end face 42 of the outer casing 11. The negative electrode current collector plate 25 is electrically connected to the inner surface of the bottom 11B of the outer casing 11, for example. Figure 7A is an exploded view showing one example configuration of the positive electrode current collector plate 24. Figure 7B is an exploded view showing one example configuration of the negative electrode current collector plate 25. The positive electrode current collector plate 24 is a metal plate made of, for example, a single material of aluminum or an aluminum alloy, or a composite material thereof. The negative electrode current collector plate 25 is a metal plate made of, for example, a single material of nickel, a nickel alloy, copper, or a copper alloy, or a composite material of two or more of these.

[0044] As shown in Figure 7A, the positive electrode current collector plate 24 has a roughly fan-shaped portion 31 and a roughly rectangular strip portion 32. However, the shape of the positive electrode current collector plate 24 is as shown in Figure 7A. 7AThe shape is not limited to those shown and can be arbitrarily selected. In the secondary battery 1, the positive electrode current collector plate 24 is housed in the outer casing 11 with the strip-shaped portion 32 bent relative to the fan-shaped portion 31, as shown in Figure 1. Figure 7A shows the positive electrode current collector plate 24 in an unfolded state. The fan-shaped portion 31 is an opposing portion that is connected to and opposite the upper end face 41. The fan-shaped portion 31 has an outer edge that includes, for example, a straight portion and a curved portion. An opening 35 is formed near the center of the fan-shaped portion 31. Figure 7A illustrates the case where 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, the straight portion of the outer edge of the fan-shaped portion 31. The strip-shaped portion 32 is connected to the straight portion of the fan-shaped portion 31 minutes and They extend in intersecting directions. As shown in Figure 1, in the secondary battery 1, the positive electrode current collector plate 24 is provided such that the opening 35 overlaps with the through hole 26 in the Z-axis direction. That is, the opening 35 is provided in a position that overlaps with a part of the upper end face 41 on the winding center side in the Z-axis direction.

[0045] figure 7A The shaded portion is the insulating portion 32A of the strip-shaped portion 32. The insulating portion 32A is a part of the strip-shaped portion 32 to which insulating tape is attached or insulating material is applied. The portion of the strip-shaped portion 32 below the insulating portion 32A is the connection portion 32B to the sealing plate which also serves as an external terminal. The sealing plate is electrically connected to the battery cover 14. Note that, as shown in Figure 1, if the secondary battery 1 has a battery structure in which the through hole 26 does not have a metal center pin, the possibility of the strip-shaped portion 32 coming into contact with the negative electrode potential portion is low. For this reason, the positive electrode current collector plate 24 does not need to have an insulating portion 32A. If the positive electrode current collector plate 24 does not have an insulating portion 32A, the charge and 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.

[0046] figure 7B The shape of the negative electrode current collector plate 25 shown in Figure 7A The shape of the positive electrode current collector plate 24 is almost the same as shown in Figure 25. The negative electrode current collector plate 25 has a roughly fan-shaped portion 33 and a roughly rectangular strip portion 34. However, the shape of the negative electrode current collector plate 25 is as shown in Figure 25. 7BThe shape is not limited to that shown and can be arbitrarily selected. In the secondary battery 1, the negative electrode current collector plate 25 is housed in the outer casing 11 with the strip-shaped portion 34 bent relative to the fan-shaped portion 33, as shown in Figure 1. 7B This represents the unfolded negative electrode current collector plate 25. The fan-shaped portion 33 is an opposing portion that is connected to and opposite the lower end face 42. The fan-shaped portion 33 has an outer edge that includes, for example, a straight portion and a curved portion. The strip-shaped portion 34 is, for example, the straight portion of the outer edge of the fan-shaped portion 33. minutes They are connected. The strip-shaped portion 34 extends in a direction intersecting the straight portion of the fan-shaped portion 33. The strip-shaped portion 34 of the negative electrode current collector plate 25 is shorter than the strip-shaped portion 32 of the positive electrode current collector plate 24 and does not have a portion corresponding to the insulating portion 32A of the positive electrode current collector plate 24. Multiple circular protrusions 37, indicated by circles, are provided on the strip-shaped portion 34. At least some of the multiple protrusions 37 are welded to the bottom 11B of the outer casing 11. During resistance welding, the current concentrates on the protrusions 37, causing the protrusions 37 to melt and the strip-shaped portion 34 to be welded to the bottom 11B of the outer casing 11. Similar to the positive electrode current collector plate 24, the negative electrode current collector plate 25 has an opening 36 formed near the center of the fan-shaped portion 33. In the secondary battery 1, the negative electrode current collector plate 25 is provided such that the opening 36 overlaps with the through hole 26 in the Z-axis direction. 7B The example given is when the opening 36 has a circular planar shape in a horizontal plane perpendicular to the Z-axis direction.

[0047] The fan-shaped portion 31 of the positive electrode current collector plate 24 covers only a portion of the upper end face 41 due to its planar shape. Similarly, the fan-shaped portion 33 of the negative electrode current collector plate 25 covers only a portion of the lower end face 42 due to its planar shape. There are two reasons, for example, why the fan-shaped portions 31 and 33 do not cover the entire upper end face 41 and lower end face 42. The first reason is to allow the electrolyte to penetrate smoothly into the electrode winding body 20 when assembling the secondary battery 1. In particular, in the secondary battery 1 of this embodiment, the positive electrode current collector plate 24 is positioned such that the opening 35 overlaps with a portion of the upper end face 41 on the winding center side in the Z-axis direction. As a result, a portion of the positive electrode edge 212E that constitutes the upper end face 41 is exposed to the opening 35 without being covered by the fan-shaped portion 31 of the positive electrode current collector plate 24. Therefore, the secondary battery 1 has a structure that allows the electrolyte to penetrate into the electrode winding body 20 more quickly. The second reason is to facilitate the release of gases generated when lithium-ion rechargeable batteries experience abnormally high temperatures or overcharge conditions.

[0048] (Positive electrode current collector 21A) The positive electrode current collector 21A contains a conductive material such as aluminum. The positive electrode current collector 21A is, for example, a metal foil made of aluminum or an aluminum alloy.

[0049] (Positive electrode active material layer 21B) The positive electrode active material layer 21B contains one or more positive electrode materials capable of intercalating and deintercalating lithium as the positive electrode active material. However, the positive electrode active material layer 21B may further contain one or more other materials such as a positive electrode binder and a positive electrode conductive agent. The positive electrode material is preferably a lithium-containing compound, and more specifically, preferably a lithium-containing composite oxide and a lithium-containing phosphate compound. A lithium-containing composite oxide is an oxide that contains lithium and one or more other elements, i.e., elements other than lithium, as constituent elements. A lithium-containing composite oxide has a crystal structure such as layered rock salt type and spinel type. A lithium-containing phosphate compound is a phosphate compound that contains lithium and one or more other elements as constituent elements, and has a crystal structure such as olivine type. In particular, the positive electrode active material layer 21B may contain at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide as the positive electrode active material. The positive electrode binder contains one or more of the following: synthetic rubber and polymer compounds. Examples of synthetic rubber include styrene-butadiene rubber, fluororubber, and ethylene-propylenediene. Examples of polymer compounds include polyvinylidene fluoride and polyimide. The positive electrode conductive agent contains one or more of the following: carbon materials. Examples of carbon materials include graphite, carbon black, acetylene black, and Ketjen black. However, the positive electrode conductive agent may also be a metal material or a conductive polymer, as long as it is a conductive material.

[0050] (Negative electrode current collector 22A) The negative electrode current collector 22A contains a conductive material such as copper. The negative electrode current collector 22A is a metal foil made of, for example, nickel, a nickel alloy, copper, or a copper alloy. It is preferable that the surface of the negative electrode current collector 22A is roughened. This is because the adhesion of the negative electrode active material layer 22B to the negative electrode current collector 22A is improved by the so-called anchoring effect. In this case, it is sufficient that the surface of the negative electrode current collector 22A is roughened in at least the region facing the negative electrode active material layer 22B. A method of roughening the surface is, for example, a method of forming fine particles using electrolytic treatment. In electrolytic treatment, fine particles are formed on the surface of the negative electrode current collector 22A by electrolysis in an electrolytic cell, so that the surface of the negative electrode current collector 22A has irregularities. Copper foil produced by electrolysis is generally called electrolytic copper foil.

[0051] (Negative electrode active material layer 22B) The negative electrode active material layer 22B contains one or more negative electrode materials capable of intercalating and releasing lithium as the negative electrode active material. However, the negative electrode active material layer 22B may further contain one or more other materials such as a negative electrode binder and a negative electrode conductive agent. The negative electrode material is, for example, a carbon material. This is because a high energy density can be stably obtained because the change in crystal structure during intercalation and release of lithium is very small. In addition, since the carbon material also functions as a negative electrode conductive agent, the conductivity of the negative electrode active material layer 22B is improved. Examples of carbon materials include easily graphitizable carbon, poorly graphitizable carbon, and graphite. However, the interplanar spacing of the (002) planes in poorly graphitizable carbon is preferably 0.37 nm or more. The interplanar spacing of the (002) planes in graphite is preferably 0.34 nm or less. More specifically, carbon materials include, for example, pyrolytic carbons, cokes, glassy carbon fibers, calcined organic polymer compounds, activated carbon, and carbon blacks. These cokes include pitch coke, needle coke, and petroleum coke. Calcined organic polymer compounds are obtained by calcining (carbonizing) polymer compounds such as phenolic resins and furan resins at an appropriate temperature. In addition, the carbon material may be low-crystalline carbon heat-treated at a temperature of approximately 1000°C or lower, or amorphous carbon. The carbon material may take the form of fibers, spheres, granules, or flakes. However, this is also acceptable. In secondary battery 1, when the open-circuit voltage at full charge, i.e., the battery voltage, is 4.25V or higher, the amount of lithium released per unit mass increases compared to when the open-circuit voltage at full charge is 4.20V, even when using the same positive electrode active material. Therefore, the amounts of positive electrode active material and negative electrode active material are adjusted accordingly. This results in a high energy density.

[0052] Further, the negative electrode active material layer 22B may contain, as a negative electrode active material, a silicon-containing material containing at least one of silicon, silicon oxide, carbon-silicon compound, and silicon alloy. The silicon-containing material is a general term for materials containing silicon as a constituent element. However, the silicon-containing material may contain only silicon as a constituent element. Note that the type of the silicon-containing material may be only one type or two or more types. The silicon-containing material can form an alloy with lithium, and may be a 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 possible.

[0053] (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 through while preventing short circuits of current caused by contact between the positive electrode 21 and the negative electrode 22. The separator 23 is made of one or more of the following porous films: synthetic resin and ceramic, for example, or a laminated film of two or more porous films. Examples of synthetic resins include polytetrafluoroethylene, polypropylene, and polyethylene. However, the separator 23 preferably has a substrate made of a single-layer polyolefin porous film containing polyethylene, because it provides better high-power characteristics compared to a laminated film. When the first separator member 23A and the second separator member constituting the separator 23 are each single-layer porous films made of polyolefin, the thickness of the porous film is preferably, for example, 10 μm or more and 15 μm or less. Having a single-layer porous film made of polyolefin with a thickness of 10 μm or more allows for sufficient avoidance of internal short circuits. Better discharge capacity characteristics can be obtained if the thickness of the single-layer porous film made of polyolefin is 15 μm or less. Furthermore, the surface density of the porous film is, for example, 6.3 g / m². 2 More than 8.3g / m 2 The following conditions are preferable: The surface density of a single-layer porous film made of polyolefin is 6.3 g / m². 2 If the above conditions are met, internal short circuits can be sufficiently avoided. The surface density of the single-layer porous film made of polyolefin is 8.3 g / m². 2 The following conditions will result in better discharge capacity characteristics.

[0054] In particular, the separator 23 may include, for example, a porous membrane as a substrate as described above, and a polymer compound layer provided on one or both sides of the substrate layer. This is because the adhesion of the separator 23 to the positive electrode 21 and the negative electrode 22 is improved, thereby suppressing distortion of the electrode winding 20. As a result, the decomposition reaction of the electrolyte is suppressed, and leakage of the electrolyte impregnated into the substrate layer is also suppressed, so that the resistance does not increase easily even after repeated charging and discharging, 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 something other than polyvinylidene fluoride. When forming this polymer compound layer, for example, a solution in which the polymer compound is dissolved in an organic solvent is applied to the substrate layer, and then the substrate layer is dried. Alternatively, the substrate layer may be immersed in the solution and then dried. This polymer compound layer may contain one or more types of insulating particles, such as inorganic particles. Examples of inorganic particles include aluminum oxide and aluminum nitride.

[0055] (electrolyte) The electrolyte contains a solvent and an electrolyte salt. However, the electrolyte may further contain one or more other materials such as additives. The solvent contains one or more non-aqueous solvents such as organic solvents. An electrolyte containing a non-aqueous solvent is a so-called non-aqueous electrolyte. The non-aqueous solvent contains, for example, fluorine compounds and dinitrile compounds. The fluorine compounds include, for example, at least one of fluorinated ethylene carbonate, trifluorocarbonate, trifluoroethyl methyl carbonate, fluorinated carboxylic acid esters, and fluorine ethers. The non-aqueous solvent may also contain nitrile compounds other than dinitrile compounds, such as mononitrile compounds and TrinitrileThe mixture may further contain at least one of the compounds. A preferred dinitrile compound is, for example, succinonitrile (SN). However, the dinitrile compound is not limited to succinonitrile, but may be other dinitrile compounds such as adiponitrile.

[0056] The electrolyte salt contains one or more types of salts, such as lithium salts. However, the electrolyte salt may also contain salts other than lithium salts. These non-lithium salts are, for example, salts of light metals other than lithium. Examples of lithium salts include lithium hexafluoride phosphate (LiPF6), lithium tetraborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoride arsenate (LiAsF6), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), and dilithium hexafluorosilicate (Li2 Si Examples include LiPF6, lithium chloride (LiCl), and lithium bromide (LiBr). Among these, one or more of lithium hexafluoride phosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoride arsenate are preferred, with lithium hexafluoride phosphate being 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 should be 1.25 mol / kg or more and 1.45 mol / kg or less. This is because it prevents cycle degradation due to salt consumption (decomposition) during high-load rate charging, thereby improving high-load cycle characteristics. When the electrolyte further contains LiBF4 in addition to LiPF6 as the electrolyte salt, the concentration of LiBF4 in the electrolyte should be 0.001 (weight%) or more and 0.1 (weight%) or less. This is because it more effectively prevents cycle degradation caused by salt consumption (decomposition) during high-load rate charging, thereby further improving high-load cycle characteristics.

[0057] [1-2. Operation] In the secondary battery 1 of this embodiment, for example, during charging, lithium ions are released from the positive electrode 21 and absorbed into the negative electrode 22 via the electrolyte. Also, in the secondary battery 1, for example, during discharge, lithium ions are released from the negative electrode 22 and absorbed into the positive electrode 21 via the electrolyte.

[0058] [1-3. Manufacturing method] Figures 1-1 7B In addition, the manufacturing method of the secondary battery 1 will be explained with reference to Figure 8. Figure 8 is a perspective view illustrating the manufacturing process of the secondary battery shown in Figure 1.

[0059] First, a positive electrode current collector 21A is prepared, and a positive electrode 21 having a positive electrode current collector covering portion 211 and a positive electrode current collector exposed portion 212 is formed by selectively forming a positive electrode active material layer 21B on the surface of the positive electrode current collector 21A. Next, a negative electrode current collector 22A is prepared, and a negative electrode active material layer 22B is selectively formed on the surface of the negative electrode current collector 22A to form a negative electrode 22 having a negative electrode current collector covering portion 221 and a negative electrode current collector exposed portion 222. The positive electrode 21 and the negative electrode 22 may be subjected to a drying treatment. Subsequently, a laminate S20 is manufactured by stacking the positive electrode 21 and the negative electrode 22 via a first separator member 23A and a second separator member 23B such that the positive electrode current collector exposed portion 212 and the first portion 222A of the negative electrode current collector exposed portion 222 are on opposite sides in the W-axis direction. Next, the laminate S20 is wound in a spiral shape so that through holes 26 are formed. At this time, for example, a cylindrical winding core is used as a jig, and the laminate S20 is wound around the cylindrical winding core. Furthermore, after attaching fixing tape 46 to the outermost circumference of the spirally wound laminate S20, the winding core is removed. This gives the electrode winding body 20 as shown in Figure 8(A).

[0060] Next, as shown in Figure 8(B), the end of a flat plate, for example, with a thickness of 0.5 mm, is pressed perpendicularly to the upper end face 41 and lower end face 42 of the electrode winding body 20, i.e., in the Z-axis direction, thereby locally bending a portion of the upper end face 41 and a portion of the lower end face 42. As a result, grooves 43 are created that extend radially (in the R direction) from the through hole 26. Note that the number and arrangement of grooves 43 shown in Figure 8(B) are illustrative examples and the present disclosure is not limited thereto.

[0061] Next, as shown in Figure 8(C), substantially the same pressure is applied substantially simultaneously and substantially the same way to the upper end face 41 and the lower end face 42 of the electrode winding body 20 from above and below, in a direction substantially perpendicular to each other. At this time, a rod-shaped jig, for example, is inserted into the through hole 26. By doing so, the first portion 222A of the exposed positive electrode current collector portion 212 and the exposed negative electrode current collector portion 222 are bent, respectively, so that the upper end face 41 and the lower end face 42 become flat surfaces. At this time, it is desirable that multiple adjacent portions of the positive electrode edge portion 212E of the exposed positive electrode current collector portion 212 on the upper end face 41 bend toward the through hole 26 so that they overlap each other in the radial direction of the electrode winding body 20. Similarly, it is desirable that multiple adjacent portions of the negative electrode edge portion 222E of the exposed negative electrode current collector portion 222 on the lower end face 42 bend toward the through hole 26 so that they overlap each other in the radial direction of the electrode winding body 20. Subsequently, the fan-shaped portion 31 of the positive electrode current collector plate 24 is joined to the upper end face 41 by laser welding or the like, and the fan-shaped portion 33 of the negative electrode current collector plate 25 is joined to the lower end face 42 by laser welding or the like.

[0062] Next, insulating tapes 53 and 54 are attached to the predetermined positions on the electrode winding body 20. Then, as shown in Figure 8(D), the strip portion 32 of the positive electrode current collector plate 24 is bent and inserted through the hole 12H of the insulating plate 12. Also, the strip portion 34 of the negative electrode current collector plate 25 is bent and inserted through the hole 13H of the insulating plate 13.

[0063] Next, the electrode winding body 20 assembled as described above is inserted into the outer casing 11 shown in Figure 8(E), and then the bottom 11B of the outer casing 11 and the negative electrode current collector plate 25 are welded together. After that, a constriction is formed near the open end 11N of the outer casing 11. department Forming. Furthermore, after injecting the electrolyte into the outer can 11, the strip portion 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 are welded together.

[0064] Next, as shown in Figure 8(F), the waist department The outer can 11 is sealed using the gasket 15, safety valve mechanism 30, and battery cover 14. Finally, the outer tube 50 is placed over the outer can 11 with the washer 55 attached on top of the battery cover 14, and then the outer tube 50 is heated and shrunk by applying hot air to it, so that the outer tube 50 is tightly attached to the outer surface of the outer can 11.

[0065] With the above steps, the secondary battery 1 of this embodiment is completed.

[0066] [1-4. Action and Effects] As described above, in the secondary battery 1 of this embodiment, the elongation rate of the insulating layer 21C covering the opposing portion FP of the positive electrode current collector exposed portion 212 that faces the negative electrode active material layer 22B across the separator 23 is set to 180% or more. Therefore, even if foreign matter such as metal powder is mixed between the insulating layer 21C and the negative electrode active material layer 22B and the cell is pressurized, the insulating layer 21C pressed against the foreign matter will stretch, effectively preventing the insulating layer 21C from rupturing or cracking. Consequently, it is possible to effectively prevent a short circuit between the positive electrode 21 and the negative electrode 22 via the foreign matter. Thus, the secondary battery 1 of this embodiment can ensure excellent safety.

[0067] In particular, in secondary battery 1, by including modified PVDF (polyvinylidene fluoride) or copolymer PVDF in the insulating layer 21C, a better elongation rate can be obtained, and a higher level of safety can be ensured.

[0068] <2. Application Examples> The applications of the secondary battery 1 as one embodiment of the present disclosure described above are, for example, as follows.

[0069] [2-1. Battery Pack] Figure 9 is a block diagram showing an example of a circuit configuration when a battery according to one embodiment of the present invention (hereinafter appropriately referred to as a secondary battery) is applied to a battery pack 300. The battery pack 300 comprises a battery pack 301, an outer casing, a switch section 304 comprising 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.

[0070] The battery pack 300 is equipped with a positive terminal 321 and a negative terminal 322. During charging, the positive terminal 321 and the negative terminal 322 are connected to the positive and negative terminals of the charger, respectively, and charging takes place. When using electronic equipment, the positive terminal 321 and the negative terminal 322 are connected to the positive and negative terminals of the electronic equipment, respectively, and discharge takes place.

[0071] The battery pack 301 is formed by connecting multiple secondary batteries 301a in series or in parallel. The secondary battery 1 described above can be used as the secondary battery 301a. In Figure 9, an example is shown where six secondary batteries 301a are connected in 2 parallel and 3 series (2P3S), but any other connection method is acceptable, such as n parallel and m series (where n and m are integers).

[0072] The switch unit 304 comprises a charge control switch 302a and a diode 302b, and a discharge control switch 303a and a diode 303b, and is controlled by the control unit 310. Diode 302b has polarity that is reverse to the charging current flowing from the positive terminal 321 towards the battery pack 301, and forward to the discharge current flowing from the negative terminal 322 towards the battery pack 301. Diode 303b has polarity that is forward to the charging current and reverse to the discharge current. Note that in Figure 9, the switch unit 304 is provided on the + side. However, it may also be provided on the - side.

[0073] The charge control switch 302a is turned off when the battery voltage reaches the overcharge detection voltage, and is controlled by the charge / discharge control unit to prevent charging current from flowing through the current path of the battery pack 301. After the charge control switch 302a is turned off, only discharge is possible via the diode 302b. Furthermore, if a large current flows during charging, it is turned off by the control unit 310 to cut off the charging current flowing through the current path of the battery pack 301. The discharge control switch 303a is turned off when the battery voltage reaches the over-discharge detection voltage, and is controlled by the control unit 310 to prevent discharge current from flowing through the current path of the battery pack 301. After the discharge control switch 303a is turned off, only charging is possible via the diode 303b. Furthermore, if a large current flows during discharge, it is turned off by the control unit 310 to cut off the discharge current flowing through the current path of the battery pack 301.

[0074] The temperature detection element 308 is, for example, a thermistor, and is located near the battery pack 301 to measure the temperature of the battery pack 301 and supply the measured temperature to the control unit 310. The voltage detection unit 311 measures the voltage of the battery pack 301 and each of the secondary batteries 301a that make up the battery pack, performs A / D conversion on this measured voltage, and supplies it to the control unit 310. The current measurement unit 313 measures the current using the current detection resistor 307 and supplies this measured current to the control unit 310. The switch control unit 314 controls the charge control switch 302a and the discharge control switch 303a of the switch unit 304 based on the voltage and current input from the voltage detection unit 311 and the current measurement unit 313.

[0075] The switch control unit 314 prevents overcharging, over-discharging, and overcurrent charging / discharging by sending a control signal to the switch unit 304 when the voltage of any of the multiple secondary batteries 301a falls below the overcharge detection voltage or the over-discharge detection voltage, or when a large current flows rapidly. 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 over-discharge detection voltage is set to, for example, 2.4V ± 0.1V.

[0076] The charge / discharge switch can use a semiconductor switch such as a MOSFET. In this case, the parasitic diodes of the MOSFET function as diodes 302b and 303b. When a P-channel FET is used as the charge / discharge switch, the switch control unit 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 type, they turn ON when the gate potential is lower than a predetermined value or more below the source potential. That is, in normal charging and discharging operation, the control signals CO and DO are set to a low level, and the charge control switch 302a and the discharge control switch 303a are turned ON.

[0077] For example, in the event of overcharging or over-discharging, the control signals CO and DO are set to high levels, and the charge control switch 302a and the discharge control switch 303a are turned OFF.

[0078] Memory 317 consists of RAM and ROM, such as EPROM (Erasable Programmable Read Only Memory), which is a non-volatile memory. Memory 317 pre-stores numerical values ​​calculated by the control unit 310 and the internal resistance values ​​of each secondary battery 301a in its initial state, measured during the manufacturing process, and can be rewritten as needed. In addition, by storing the full charge capacity of the secondary battery 301a, it is possible to calculate the remaining capacity, for example, in conjunction with the control unit 310.

[0079] 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, as well as making corrections when calculating the remaining capacity.

[0080] [2-2. Energy Storage Systems] The secondary battery according to one embodiment of the present disclosure described above can be installed in or used to supply power to devices such as electronic equipment, electric vehicles, electric aircraft, and energy storage devices.

[0081] Examples of electronic devices include laptop computers, smartphones, tablet devices, PDAs (personal digital assistants), mobile phones, wearable devices, cordless phone handsets, video cameras, 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 devices, robots, road conditioners, and traffic lights.

[0082] Electric vehicles include railway cars, golf carts, electric carts, and electric vehicles (including hybrid vehicles), and these are used as power sources or auxiliary power sources for their operation. Energy storage devices include power sources for buildings such as houses, or for storing electricity in power generation facilities. [Examples]

[0083] Examples of the present disclosure will be described below.

[0084] [Manufacturing method] (Example 1) As described below, a cylindrical secondary battery, as shown in Figure 1, was fabricated. In this case, a lithium-ion secondary battery with nominal dimensions of 21 mm in diameter and 70 mm in length was created.

[0085] First, a 12 μm thick aluminum foil was prepared as the positive electrode current collector 21A. Next, a positive electrode mixture was obtained by mixing a positive electrode binder consisting of layered lithium oxide (NCA) with a Ni ratio of 85% or more, polyvinylidene fluoride, and a conductive additive mixed with carbon black, acetylene black, and Ketjen black. The mixing ratio of the positive electrode active material, positive electrode binder, and conductive additive was 96.4:2:1.6. Subsequently, 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. Subsequently, the positive electrode mixture slurry was applied to predetermined areas on both sides of the positive electrode current collector 21A using a coating apparatus, and the positive electrode mixture slurry was dried to form the positive electrode active material layer 21B. Furthermore, an insulating layer 21C with a width of 3 mm and a thickness of 8 μm was formed by applying a PVDF copolymerized with TFE paint to the surface of the exposed positive electrode current collector portion 212 adjacent to the covered portion 211 and drying it. After that, the positive electrode active material layer 21B was compression molded using a roll press machine. As a result, a positive electrode 21 having a covered portion 211 and an exposed positive electrode current collector portion 212 was obtained. Subsequently, the positive electrode 21 was sheared to make the width of the covered portion 211 in the W-axis direction 60 mm and the width of the exposed positive electrode current collector portion 212 in the W-axis direction 7 mm. The length of the positive electrode 21 in the L-axis direction was made 1700 mm.

[0086] Furthermore, a copper foil with a thickness of 8 μm was prepared as the negative electrode current collector 22A. Next, a negative electrode mixture was obtained by mixing a negative electrode active material, which was a mixture of a carbon material consisting of graphite and SiO, a negative electrode binder consisting of polyvinylidene fluoride, and a conductive additive, which was a mixture of carbon black, acetylene black, and Ketjen black. The mixing ratio of the negative electrode active material, negative electrode binder, and conductive additive was set to 96.1:2.9:1.0. In addition, the mixing ratio of graphite and SiO in the negative electrode active material was set to 95:5. Subsequently, 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. Subsequently, the negative electrode mixture slurry was applied to predetermined areas on both sides of the negative electrode current collector 22A using a coating apparatus, and then the negative electrode mixture slurry was dried to form the negative electrode active material layer 22B. Subsequently, the negative electrode active material layer 22B was compression molded using a roll press. This resulted in obtaining a negative electrode 22 having a negative electrode current collector covering portion 221 and a negative electrode current collector exposed portion 222. The negative electrode 22 was then sheared to set the width of the negative electrode current collector covering portion 221 in the W-axis direction to 62 mm, and the width of the first portion 222A of the negative electrode current collector exposed portion 222 in the W-axis direction to 4 mm. Furthermore, the length of the negative electrode 22 in the L-axis direction was set to 1760 mm.

[0087] Next, a laminate S20 was fabricated by stacking the positive electrode 21 and the negative electrode 22 via a first separator member 23A and a second separator member 23B such that the exposed portion 212 of the positive electrode current collector and the first portion 222A of the exposed portion 222 of the negative electrode current collector were on opposite sides in the W-axis direction. At that time, the laminate S20 was fabricated so that the positive electrode active material layer 21B did not protrude from the negative electrode active material layer 22B in the W-axis direction. A polyethylene sheet having a width of 65 mm and a thickness of 14 μm was used as the first separator member 23A and the second separator member 23B. After that, the laminate S20 was wound in a spiral shape so that through holes 26 were formed, and fixing tape 46 was attached to the outermost circumference of the wound laminate S20.

[0088] Next, by pressing the end of a 0.5 mm thick flat plate against the upper end face 41 and the lower end face 42 of the electrode winding body 20 in the Z-axis direction, the upper end face 41 and the lower end face 42 were locally bent, creating grooves 43 that extend radially (R-direction) from the through hole 26.

[0089] Next, substantially the same pressure was applied substantially simultaneously and perpendicularly to the upper end face 41 and lower end face 42 from above and below the electrode winding body 20. This bent the exposed portion 212 of the positive electrode current collector and the first portion 222A of the exposed portion 222 of the negative electrode current collector, respectively, making the upper end face 41 and lower end face 42 flat surfaces. At this time, the positive electrode edge 212E of the exposed portion 212 of the exposed portion 212 of the exposed portion 222E of the exposed portion 222 of the exposed portion 222 of the negative electrode current collector on the upper end face 41 and lower end face 42 were bent while overlapping toward the through hole 26. After that, the fan-shaped portion 31 of the positive electrode current collector plate 24 was joined to the upper end face 41 by laser welding, and the fan-shaped portion 33 of the negative electrode current collector plate 25 was joined to the lower end face 42 by laser welding.

[0090] Next, insulating tapes 53 and 54 were attached to the predetermined positions on the electrode winding body 20. Then, the strip portion 32 of the positive electrode current collector plate 24 was bent and inserted through the hole 12H of the insulating plate 12, and the strip portion 34 of the negative electrode current collector plate 25 was bent and inserted through the hole 13H of the insulating plate 13.

[0091] Next, the electrode winding body 20 assembled as described above was inserted into the outer casing 11, and then the bottom 11B of the outer casing 11 and the negative electrode current collector plate 25 were welded together.

[0092] Subsequently, a constricted portion 11S was formed near the open end 11N of the outer casing 11. Furthermore, after injecting the electrolyte into the outer casing 11, the strip-shaped portion 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 were welded together.

[0093] As the electrolyte, a solvent was used which consisted of ethylene carbonate (EC) and dimethyl carbonate (DMC) as the main solvents, to which fluoroethylene carbonate (FEC) and succinonitrile (SN) were added, and which contained LiBF4 and LiPF6 as electrolyte salts. In the lithium-ion secondary battery of this example, the respective content (weight %) of EC, DMC, FEC, SN, LiBF4, and LiPF6 in the electrolyte was 12.7:56.2:12.0:1.0:1.0:17.1.

[0094] Finally, the constricted portion 11S is used to seal the gasket 15, safety valve mechanism 30 and battery cover 14. Ta.

[0095] Based on the above, the secondary battery of Example 1 was obtained.

[0096] (Example 2) When fabricating the positive electrode 21, an insulating layer 21C with a width of 3 mm and a thickness of 8 μm was formed by applying and drying a PVDF copolymerized with HFP. Except for this point, the secondary battery of Example 2 was fabricated in the same manner as the secondary battery of Example 1.

[0097] (Example 3) When fabricating the positive electrode 21, an insulating layer 21C with a width of 3 mm and a thickness of 8 μm was formed by applying and drying a PVDF coating modified with acrylic acid. Except for this point, the secondary battery of Example 3 was fabricated in the same manner as the secondary battery of Example 1.

[0098] (Example 4) When fabricating the positive electrode 21, an insulating layer 21C with a width of 3 mm and a thickness of 8 μm was formed by applying a PVDF coating modified with maleic acid and drying it. Except for this point, the secondary battery of Example 4 was fabricated in the same manner as the secondary battery of Example 1.

[0099] (Comparative Example 1) When preparing the positive electrode 21, an insulating layer 21C with a width of 3 mm and a thickness of 8 μm was formed by applying and drying an acrylic paint. Except for this point, the secondary battery of Comparative Example 1 was prepared in the same manner as the secondary battery of Example 1.

[0100] (Comparative Examples 2-5) When preparing the positive electrode 21, an insulating layer 21C with a width of 3 mm and a thickness of 8 μm was formed by applying and drying an unmodified polymer PVDF coating. Except for this point, the secondary batteries of Comparative Examples 2 to 5 were prepared in the same manner as the secondary battery of Example 1.

[0101] (Comparative Example 6) When preparing the positive electrode 21, an insulating layer 21C with a width of 3 mm and a thickness of 8 μm was formed by applying and drying a PVDF coating copolymerized with CTFE (chlorotrifluoroethylene). Except for this point, the secondary battery of Comparative Example 6 was prepared in the same manner as the secondary battery of Example 1.

[0102] [Evaluation of battery characteristics] For each of the secondary batteries obtained as described above, tensile strength and elongation were measured, and a forced internal short-circuit test was performed. The results are summarized in Table 1.

[0103] [Table 1]

[0104] (Tensile strength and elongation) Strip-shaped samples were taken from the insulating layer 21C used in each of the secondary batteries in Examples 1-4 and Comparative Examples 1-6, and tested according to "JIS K 7161-2014 Plastics - Test method for tensile properties". A tensile test was conducted in accordance with the regulations of the "Test Specification Act," and the tensile strength (maximum stress observed during the test) [N] and the elongation rate [%] until the test specimen fractured were measured. The dimensions of the test specimen were 10 mm in length between the grips (60 mm in length including the gripping portion) and 3 mm in width. The tensile speed was 10 mm / min.

[0105] (Forced internal short circuit test) For each secondary battery in Examples 1-4 and Comparative Examples 1-6, the test was conducted in accordance with the "Forced Internal Short Circuit Test of Single Cells" in "JIS C8714:2007 Safety Tests for Single Cells and Battery Packs of Lithium-ion Rechargeable Batteries for Portable Electronic Devices". Specifically, the electrode winding of each secondary battery was unfolded, a nickel chip (L-shaped, 0.2 mm high, 0.1 mm wide, 1 mm on each side) was placed between the insulating layer 21C covering the positive electrode current collector 21A and the negative electrode active material layer 22B, and then the electrode winding was rewound. After that, the electrode winding was placed in a constant temperature bath set to a predetermined temperature, and pressure was applied to the area where the nickel chip was placed. The pressure was applied by pressing a pressure jig against the area where the nickel chip was placed on the electrode winding at a speed of 0.1 mm / second until the pressure reached 800 N. Here, a voltage drop of 50 mV or more from the initial voltage was detected, which was judged to be a short circuit, and the test was terminated at the point when a short circuit was detected.

[0106] As shown in Table 1, in the forced internal short-circuit test, short circuits occurred in all of Comparative Examples 1-6, whereas no short circuits occurred in Examples 1-4. This is because, in Examples 1-4, the elongation rate was 180% or more, so even if foreign matter was present, cracks in the insulating layer 21C would not occur. This is thought to be because no fracture or breakage occurred.

[0107] Based on the above results, it was confirmed that the secondary battery described in this disclosure can ensure excellent safety.

[0108] Although the present disclosure has been described above with reference to one embodiment, the configuration of the present disclosure is not limited to the configuration described in the above embodiment and can be modified in various ways. For example, in the above embodiment, a modified PVDF or copolymer PVDF was given as an example of a constituent material of the insulating layer 21C, but the present disclosure is not limited thereto and other types of resin materials can be used.

[0109] Furthermore, although the above embodiment and examples describe a cylindrical secondary battery equipped with an electrode winding body having a circular cross-sectional shape, the disclosure is not limited thereto. For example, a rectangular secondary battery equipped with an electrode winding body having an elliptical, flattened cross-sectional shape may also be used.

[0110] Furthermore, although the above embodiment and examples described the case where the electrode reactant is lithium, the electrode reactant is not particularly limited. For this reason, the electrode reactant may be other alkali metals such as sodium and potassium, as described above, or alkaline earth metals such as beryllium, magnesium and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0111] The effects described herein are illustrative only, and the effects of this disclosure are not limited to those described herein. Therefore, other effects may be obtained with respect to this disclosure.

[0112] This disclosure may take the following forms: <1> Positive electrode current collector plate, Negative electrode current collector plate, An electrode winding body is positioned between the positive electrode current collector plate and the negative electrode current collector plate, and is wound around a through hole through which a laminate containing a positive electrode, a negative electrode, and a separator penetrates in the height direction. Equipped with, The electrode winding body has a first end face facing the positive electrode current collector plate in the height direction, and a second end face facing the negative electrode current collector plate in the height direction. The positive electrode includes a positive electrode current collector, a positive electrode active material layer covering a portion of the positive electrode current collector, and an insulating layer. The positive electrode includes a positive electrode current collector covering portion in which the positive electrode current collector is covered by the positive electrode active material layer, and a positive electrode current collector exposed portion in which the positive electrode current collector is not covered by the positive electrode active material layer. At least a portion of the exposed portion of the positive electrode current collector constitutes the first end face and is connected to the positive electrode current collector plate. The negative electrode includes a negative electrode current collector and a negative electrode active material layer covering a portion of the negative electrode current collector. The negative electrode includes a negative electrode current collector covering portion in which the negative electrode current collector is covered by the negative electrode active material layer, and a negative electrode current collector exposed portion in which the negative electrode current collector is not covered by the negative electrode active material layer. At least a portion of the exposed negative electrode current collector constitutes the second end face and is connected to the negative electrode current collector plate. The insulating layer covers the portion of the exposed positive electrode current collector that faces the negative electrode active material layer across the separator, and has an elongation rate of 180% or more. Secondary battery. <2> The length of the negative electrode active material layer in the height direction is longer than the length of the positive electrode active material layer in the height direction. the above <1> The rechargeable battery described. <3> The insulating layer contains modified PVDF (polyvinylidene fluoride) or copolymer PVDF. the above <1> or <2> The rechargeable battery described. <4> The insulating layer is made of PVDF that has been modified or copolymerized with TFE (tetrafluoroethylene), HFP (hexafluoropropylene), acrylic acid, and maleic acid. the above <1> from <3> A rechargeable battery as described in one of the following. <5> The first end face is formed by bending the edge of the exposed portion of the positive electrode current collector toward the through hole while it is wound around the body. The second end face is formed by bending the edge of the exposed portion of the negative electrode current collector toward the through hole while it is wound up. the above <1> from <4> A rechargeable battery as described in one of the following. <6> The cover portion connected to the positive electrode current collector plate, The system further comprises an outer casing that houses the positive electrode current collector plate, the negative electrode current collector plate, and the electrode winding body, and is connected to the negative electrode current collector plate, The outer can has a bottom and a wall portion that is erected in the height direction along the outer edge of the bottom so as to surround the electrode winding and includes an open end on the opposite side of the bottom through which the electrode winding can be inserted. The lid portion closes the open end of the outer can. the above <1> from <5> A rechargeable battery as described in one of the following. <7> the above <1> from <6> A rechargeable battery as described in any one of the following, A control unit for controlling the secondary battery, The outer casing enclosing the aforementioned secondary battery and A battery pack that has [a certain feature].

Claims

1. Positive electrode current collector plate, Negative electrode current collector plate, Displaced between the positive electrode current collector plate and the negative electrode current collector plate, the electrode winding body has a through hole that penetrates in the height direction, and a laminate including a positive electrode, a negative electrode and a separator is wound around it. Equipped with, The electrode winding body has a first end face facing the positive electrode current collector plate in the height direction, and a second end face facing the negative electrode current collector plate in the height direction. The positive electrode includes a positive electrode current collector, a positive electrode active material layer covering a portion of the positive electrode current collector, and an insulating layer. The positive electrode includes a positive electrode current collector covering portion in which the positive electrode current collector is covered by the positive electrode active material layer, and a positive electrode current collector exposed portion in which the positive electrode current collector is not covered by the positive electrode active material layer. At least a portion of the exposed portion of the positive electrode current collector constitutes the first end face and is connected to the positive electrode current collector plate. The negative electrode includes a negative electrode current collector and a negative electrode active material layer covering a portion of the negative electrode current collector. The negative electrode includes a negative electrode current collector covering portion in which the negative electrode current collector is covered by the negative electrode active material layer, and a negative electrode current collector exposed portion in which the negative electrode current collector is not covered by the negative electrode active material layer. At least a portion of the exposed negative electrode current collector constitutes the second end face and is connected to the negative electrode current collector plate. The insulating layer covers the portion of the exposed positive electrode current collector that faces the negative electrode active material layer across the separator, and has an elongation rate of 180% or more. Secondary battery.

2. The length of the negative electrode active material layer in the height direction is longer than the length of the positive electrode active material layer in the height direction. The secondary battery according to claim 1.

3. The insulating layer contains modified PVDF (polyvinylidene fluoride) or copolymer PVDF. The secondary battery according to claim 1.

4. The insulating layer is made of PVDF that has been modified or copolymerized with TFE (tetrafluoroethylene), HFP (hexafluoropropylene), acrylic acid, and maleic acid. The secondary battery according to claim 1.

5. The first end face is formed by bending the edge of the exposed portion of the positive electrode current collector toward the through hole while it is wound around the body. The second end face is formed by bending the edge of the exposed portion of the negative electrode current collector toward the through hole while it is wound up. The secondary battery according to claim 1.

6. The cover portion connected to the positive electrode current collector plate, The system further comprises an outer casing that houses the positive electrode current collector plate, the negative electrode current collector plate, and the electrode winding body, and is connected to the negative electrode current collector plate, The outer can has a bottom and a wall portion that is erected in the height direction along the outer edge of the bottom so as to surround the electrode winding and includes an open end on the opposite side of the bottom through which the electrode winding can be inserted. The lid covers the open end of the outer can. The secondary battery according to claim 1.

7. A secondary battery according to any one of claims 1 to 6, A control unit for controlling the secondary battery, The outer casing enclosing the aforementioned secondary battery and A battery pack that has [a certain feature].

Images