Secondary battery and battery pack

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

Secondary batteries and battery packs

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

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

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

[0004] International Publication No. 2021 / 020235

[0005] Various efforts have been made to improve the performance of secondary batteries, but there is still 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 includes a positive electrode current collector, a negative electrode current collector, and an electrode winding disposed between the positive electrode current collector and the negative electrode current collector, the electrode winding having a through hole extending therethrough in the height direction and including a laminate wound around the positive electrode, the negative electrode, and a separator. The electrode winding has a first end face facing the positive electrode current collector in the height direction and a second end face facing the negative electrode current collector 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 with the positive electrode active material layer, and a positive electrode current collector exposed portion in which the positive electrode current collector is exposed and not 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. 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 coated portion in which the negative electrode current collector is coated with the negative electrode active material layer, and a negative electrode current collector exposed portion in which the negative electrode current collector is exposed without being covered with 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 a portion of the positive electrode current collector exposed portion that faces the negative electrode active material layer across the separator, and has an elongation of 180% or more.

[0008] In the secondary battery according to an embodiment of the present disclosure, the insulating layer covering the exposed portion of the positive electrode current collector facing the negative electrode active material layer across the separator has an elongation of 180% or more. Therefore, even if foreign matter such as metal powder gets mixed between the insulating layer and the negative electrode active material layer, the insulating layer can be effectively prevented from breaking or cracking. Therefore, the secondary battery according to an embodiment of the present disclosure can ensure excellent safety.

[0009] The effects of the present disclosure are not necessarily limited to the effects described here, but may be any of a series of effects related to the present disclosure described below.

[0010] FIG. 1 is a cross-sectional view illustrating an example of a vertical cross-sectional structure along the height direction of a secondary battery according to an embodiment of the present disclosure. FIG. 2 is a schematic diagram illustrating an example of a laminate including a positive electrode, a negative electrode, and a separator illustrated in FIG. 1 . FIG. 3 is a cross-sectional view illustrating an example of a horizontal cross-sectional structure of an electrode winding body illustrated in FIG. 1 . FIG. 4A is a developed view of the positive electrode illustrated in FIG. 1 . FIG. 4B is a cross-sectional view of the positive electrode illustrated in FIG. 1 . FIG. 5A is a developed view of the negative electrode illustrated in FIG. 1 . FIG. 5B is a cross-sectional view of the negative electrode illustrated in FIG. 1 . FIG. 6 is an enlarged cross-sectional view illustrating an example of a portion of the vertical cross-sectional structure of the secondary battery illustrated in FIG. 1 . FIG. 7A is a plan view of the positive electrode current collector illustrated in FIG. 1 . FIG. 7B is a plan view of the negative electrode current collector illustrated in FIG. 1 . FIG. 8 is a perspective view illustrating a manufacturing process of the secondary battery illustrated in FIG. 1 . FIG. 9 is a block diagram illustrating a circuit configuration of a battery pack to which the secondary battery according to an embodiment of the present disclosure is applied.

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

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

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

[0014] The charge / discharge principle of a secondary battery is not particularly limited, but the following description focuses on a case where battery capacity is obtained by utilizing the absorption / desorption of an electrode reactant. This secondary battery includes a positive electrode, a negative electrode, and an electrolyte. In this secondary battery, the charge capacity of the negative electrode is larger than the discharge capacity of the positive electrode to prevent deposition of the electrode reactant on the surface of the negative electrode during charging. In other words, 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 electrode reactant is not particularly limited as described above, but specifically includes light metals such as alkali metals and alkaline earth metals. Alkali metals include lithium, sodium, and potassium, and alkaline earth metals include beryllium, magnesium, and calcium.

[0016] In the following, we will take the case where the electrode reactant is lithium as an example. A secondary battery that obtains battery capacity by utilizing the absorption and desorption of lithium is called a lithium ion secondary battery. In this lithium ion secondary battery, lithium is absorbed and desorbed in the ionic state.

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

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

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

[0020] (Outer tube 50) The outer tube 50 surrounds the side surface 11WS1, which is the outer surface of the side wall portion 11W of the outer can 11. However, as shown in Fig. 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 portion of the bottom surface 11BS, which is the outer surface of the bottom portion 11B of the outer can 11. The outer tube 50 is made of a heat-shrinkable insulating film containing, for example, a polyester-based resin, a polyamide-based resin, or a thermoplastic elastomer resin.

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

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

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

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

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

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

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

[0028] FIG. 2 is a developed view of the electrode winding body 20, and schematically illustrates a portion of a laminate S20 including a positive electrode 21 as a first electrode, a negative electrode 22 as a second electrode, and a separator 23. In the laminate S20 obtained by developing the electrode winding body 20, the positive electrode 21 and the negative electrode 22 are stacked together with the separator 23 interposed therebetween. The separator 23 includes, for example, two substrates, namely, a first separator member 23A and a second separator member 23B. Thus, the electrode winding body 20 includes 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 this order. The positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are all substantially strip-shaped members with the W-axis direction as the short side direction and the L-axis direction as the long side direction.

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

[0030] The positive electrode 21, the negative electrode 22, and the separator 23 are wound such that the separator 23 is disposed at the outermost and innermost peripheries of the electrode winding body 20, respectively. At the outermost periphery of the electrode winding body 20, the negative electrode 22 is disposed outside the positive electrode 21. That is, as shown in FIG. 3 , a positive electrode outermost portion 21out located at the outermost periphery of the positive electrode 21 included in the electrode winding body 20 is disposed inside a negative electrode outermost portion 22out located at the outermost periphery of the negative electrode 22 included in the electrode winding body 20. Here, the positive electrode outermost portion 21out refers to the outermost portion of the positive electrode 21 in the electrode winding body 20, which corresponds to one circumference. The negative electrode outermost portion 22out refers to the outermost portion of the negative electrode 22 in the electrode winding body 20, which corresponds to one circumference. Meanwhile, at the innermost periphery of the electrode winding body 20, the negative electrode 22 is disposed inside the positive electrode 21. That is, as shown in Fig. 3, the negative electrode innermost circumferential portion 22in, which is located at the innermost periphery of the negative electrode 22 included in the electrode winding body 20, is located inside the positive electrode innermost circumferential portion 21in, which is located at the innermost periphery of the positive electrode 21 included in the electrode winding body 20. Here, the positive electrode innermost circumferential portion 21in is the innermost one-circumferential portion of the positive electrode 21 in the electrode winding body 20. The negative electrode innermost circumferential portion 22in is the innermost one-circumferential portion of the negative electrode 22 in the electrode winding body 20. The number of windings of each of the positive electrode 21, the negative electrode 22, and the separator 23 is not particularly limited and can be set as desired.

[0031] FIG. 4A is a developed view of the positive electrode 21, schematically illustrating the state before winding. FIG. 4B illustrates a cross-sectional configuration of the positive electrode 21. Note that FIG. 4B illustrates a cross section taken along line IVB-IVB in FIG. 4A as viewed from the arrow direction. The positive electrode 21 includes, for example, a positive electrode current collector 21A, a positive electrode active material layer 21B that covers a portion of the positive electrode current collector 21A, and an insulating layer 21C. Note that the insulating layer 21C is omitted from FIG. 1. The positive electrode active material layer 21B may be provided on only one surface of the positive electrode current collector 21A, or on both surfaces of the positive electrode current collector 21A. FIG. 4B illustrates a case in which the positive electrode active material layer 21B is provided on both surfaces of the positive electrode current collector 21A. More specifically, the positive electrode current collector 21A includes a positive electrode current collector inner peripheral surface 21A1 facing the winding center of the electrode wound body 20, i.e., facing the central axis CL, and a positive electrode current collector outer peripheral surface 21A2 facing the side opposite the winding center of the electrode wound body 20, i.e., on the opposite side of the positive electrode current collector inner peripheral surface 21A1. The positive electrode 21 has, as the positive electrode active material layer 21B, a positive electrode inner peripheral side active material layer 21B1 covering at least a portion of the positive electrode current collector inner peripheral surface 21A1, and a positive electrode outer peripheral side active material layer 21B2 covering at least a portion of the positive electrode current collector outer peripheral surface 21A2. Note that in this specification, the positive electrode inner peripheral side active material layer 21B1 and the positive electrode outer peripheral side active material layer 21B2 may be collectively referred to as the positive electrode active material layer 21B without distinguishing between them.

[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 the 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 with the positive electrode active material layer 21B. As shown in FIG. 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 peripheral edge 21E2 of the positive electrode 21. Here, the L-axis direction corresponds to the winding direction of the electrode wound body 20. That is, in the positive electrode 21, the positive electrode active material layer 21B covers the positive electrode current collector 21A from the central axis side edge 21E1 to the outer peripheral edge 21E2 of the positive electrode 21 in the winding direction of the electrode wound body 20. 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. As shown in FIG. 2 , in the electrode winding 20, the central axis-side edge 21E1 of the positive electrode innermost circumferential portion 21 in is positioned further inward than the central axis-side edge 22E1 of the negative electrode innermost circumferential portion 22 in. The positive electrode 21 also has a lower edge 21E3 extending in the L-axis direction at the lower side of the electrode winding 20. Note that FIGS. 4A and 4B schematically depict the positive electrode current collector 21A extending linearly along the W-axis direction. However, in reality, the positive electrode edge 212E of the positive electrode current collector exposed portion 212 is bent toward the central axis CL as shown in FIG. 1 and connected to the positive electrode current collector plate 24. That is, the end of the positive electrode current collector exposed portion 212 in the W-axis direction forms the upper end surface 41 and is connected to the positive electrode current collector plate 24 (see FIG. 1 ). The upper end surface 41 is formed by bending the positive electrode edge portion 212E of the positive electrode current collector exposed portion 212 toward the through hole 26 in a wound state.

[0033] An insulating layer 21C may be provided near the boundary between the positive electrode current collector cover portion 211 and the positive electrode current collector exposed portion 212. Similar to the positive electrode current collector cover portion 211 and the positive electrode current collector exposed portion 212, the insulating layer 21C may also extend along the L-axis direction from the central axis side edge 21E1 to the outer peripheral side edge 21E2 of the electrode winding body 20. The insulating layer 21C may also be bonded to at least one of the first separator member 23A and the second separator member 23B. This is because misalignment between the positive electrode 21 and the separator 23 can be prevented. The detailed configuration of the positive electrode 21 will be described later.

[0034] FIG. 5A is a developed view of the negative electrode 22, schematically illustrating the state before winding. FIG. 5B illustrates a cross-sectional configuration of the negative electrode 22. Note that FIG. 5B illustrates a cross section taken along line VB-VB in FIG. 5A as viewed from the arrow direction. The negative electrode 22 includes, for example, a negative electrode current collector 22A and a negative electrode active material layer 22B that covers a portion of the negative electrode current collector 22A. The negative electrode active material layer 22B may be provided on only one surface of the negative electrode current collector 22A, or on both surfaces of the negative electrode current collector 22A. FIG. 5B illustrates a case in which the negative electrode active material layer 22B is provided on both surfaces of the negative electrode current collector 22A. More specifically, the negative electrode current collector 22A includes a negative electrode current collector inner peripheral surface 22A1 facing the winding center of the electrode wound body 20, i.e., facing the central axis CL, and a negative electrode current collector outer peripheral surface 22A2 facing the side opposite the winding center of the electrode wound body 20, i.e., on the opposite side of the negative electrode current collector inner peripheral surface 22A1. The negative electrode 22 has, as the negative electrode active material layer 22B, a negative electrode inner peripheral side active material layer 22B1 covering at least a portion of the negative electrode current collector inner peripheral surface 22A1, and a negative electrode outer peripheral side active material layer 22B2 covering at least a portion of the negative electrode current collector outer peripheral surface 22A2. Note that in this specification, the negative electrode inner peripheral side active material layer 22B1 and the negative electrode outer peripheral side active material layer 22B2 may be collectively referred to as the negative electrode active material layer 22B without distinguishing between them.

[0035] The negative electrode 22 has a negative electrode current collector covered portion 221 in which a negative electrode active material layer 22B is covered on a negative electrode current collector 22A, 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 FIG. 5A , the negative electrode current collector covered 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 peripheral edge 22E2 of the negative electrode 22 in the winding direction of the electrode wound body 20. In contrast, the negative electrode current collector covered portion 221 is not provided on the central axis side edge 22E1 or the outer peripheral edge 22E2 of the negative electrode 22. 5A , a portion of the negative electrode current collector exposed portion 222 is formed to sandwich the negative electrode current collector cover portion 221 in the L-axis direction, which is the longitudinal direction of the negative electrode 22. Specifically, the negative electrode current collector exposed portion 222 includes a first portion 222A, a second portion 222B, and a third portion 222C. The negative electrode 22 further has a lower edge 22E3 extending in the L-axis direction at the lower side of the electrode winding body 20. The first portion 222A is provided adjacent to the negative electrode current collector cover portion 221 in the W-axis direction and extends in the L-axis direction from the central axis side edge 22E1 to the outer circumferential 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 cover 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 the central axis side edge 22E1 of the negative electrode 22, for example, and the third portion 222C is located near the outer peripheral edge 22E2 of the negative electrode 22. Note that FIGS. 5A and 5B schematically illustrate the negative electrode current collector 22A extending linearly along the W-axis direction. However, in reality, the negative electrode edge 222E of the negative electrode current collector exposed portion 222 is bent toward the central axis CL as shown in FIG. 1 and connected to the negative electrode current collector plate 25. That is, the end of the negative electrode current collector exposed portion 222 in the W-axis direction forms the lower end surface 42 and is connected to the negative electrode current collector plate 25 (see FIG. 1). The lower end surface 42 is formed by bending the negative electrode edge 222E of the negative electrode current collector exposed portion 222 toward the through-hole 26 in a wound state. 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 with the separator 23 interposed between them so that the positive electrode current collector exposed portion 212 and the first portion 222A of the negative electrode current collector exposed portion 222 face opposite each other along the W-axis direction, which is the width direction. The electrode winding body 20 has the end of the separator 23 fixed by attaching a fixing tape 46 to its side surface portion 45, preventing loosening of the winding.

[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 width A = 7 (mm), width B = 4 (mm). Furthermore, when the width of the portion of the positive electrode current collector exposed portion 212 that protrudes from the outer edge of the separator 23 in the width direction is C and the length of the portion of the first portion 222A of the negative electrode current collector exposed portion 222 that protrudes from the outer edge of the separator 23 on the opposite side in the width direction is D, it is preferable that C > D. For example, when width C = 4.5 (mm), width D = 3 (mm). Note that the numerical values ​​of widths A to D and the magnitude relationships of the numerical values ​​of widths A to D described herein are merely examples, and the present disclosure is not limited to the numerical values ​​and magnitude relationships described herein. Furthermore, the Z-axis direction of the negative electrode active material layer 22B (negative electrode current collector covering portion 221) is longer than 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 ensure that the entire positive electrode active material layer 21B faces the negative electrode active material layer 22B via the separator 23, thereby preventing lithium ions released from the positive electrode 21 from being deposited on the surface of the negative electrode 22.

[0038] 1 , at the upper part of the secondary battery 1, of the positive electrode current collector exposed portion 212 wound around the central axis CL, a plurality of adjacent positive electrode edge portions 212E in the radial direction (direction R) of the electrode winding body 20 are bent toward the central axis CL so as to overlap with each other, thereby constituting an upper end surface 41 of the electrode winding body 20. Similarly, at the lower part of the secondary battery 1, of the negative electrode current collector exposed portion 222 wound around the central axis CL, a plurality of adjacent negative electrode edge portions 222E in the radial direction (direction R) are bent toward the central axis CL so as to overlap with each other, thereby constituting a lower end surface 42 of the electrode winding body 20. Therefore, a plurality of positive electrode edge portions 212E of the positive electrode current collector exposed portion 212 are gathered at the upper end surface 41 of the electrode winding body 20, and a plurality of negative electrode edge portions 222E of the negative electrode current collector exposed portion 222 are gathered at the lower end surface 42 of the electrode winding body 20. To improve contact between the positive electrode current collector plate 24 for extracting current and the positive electrode edge portion 212E, the multiple positive electrode edge portions 212E are bent toward the central axis CL and have flat surfaces. Similarly, to improve contact between the negative electrode current collector plate 25 for extracting current and the negative electrode edge portion 222E, the multiple negative electrode edge portions 222E are bent toward the central axis CL and have flat surfaces. Note that the flat surface referred to here does not only include a completely flat surface, but also includes a surface that has some unevenness or surface roughness to the extent that the positive electrode current collector exposed portion 212 and the negative electrode current collector exposed portion 222 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 described below. Meanwhile, the negative electrode current collector 22A is made of, for example, copper foil, as described below. In this case, the positive electrode current collector 21A is softer than the negative electrode current collector 22A. That is, the Young's modulus of the positive electrode current collector exposed portion 212 is lower than that of the negative electrode current collector exposed portion 222. For this reason, in one embodiment, it is more preferable that the widths A to D satisfy the relationship A > B and C > D. In this case, when the positive electrode current collector exposed portion 212 and the negative electrode current collector exposed portion 222 are folded simultaneously from both electrode sides with the same pressure, the heights of the folded portions measured from the tip of the separator 23 may be approximately the same for the positive electrode 21 and the negative electrode 22. At this time, the multiple positive electrode edge portions 212E ( FIG. 1 ) of the positive electrode current collector exposed portion 212 are folded and overlap each other to a moderate degree. This allows easy joining of the positive current collector exposed portion 212 and the positive current collector plate 24. Similarly, the multiple negative electrode edge portions 222E ( FIG. 1 ) of the negative current collector exposed portion 222 are each folded and overlap appropriately. This allows easy joining of the negative current collector exposed portion 222 and the negative current collector plate 25. The term "joining" as used herein means joining them together by, for example, laser welding, but the joining method is not limited to laser welding.

[0040] FIG. 6 is an enlarged cross-sectional view illustrating an example of a portion of the vertical cross-sectional structure of the secondary battery 1 shown in FIG. 1 . As shown in FIGS. 2 and 6 , the facing portion FP of the positive electrode current collector exposed portion 212 of the positive electrode 21, which faces the negative electrode 22 across the separator 23, is covered with 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 region of the positive electrode current collector exposed portion 212 of the positive electrode 21 that faces the negative electrode current collector covered portion 221 of the negative electrode 22 with the separator 23 interposed therebetween. The insulating layer 21C can effectively prevent an internal short circuit in the secondary battery 1, for example, when foreign matter enters between the negative electrode current collector covered portion 221 and the positive electrode current collector exposed portion 212. In addition, when an impact is applied to the secondary battery 1, the insulating layer 21C absorbs the impact and can effectively prevent bending of the positive electrode current collector exposed portion 212 and short-circuiting between the positive electrode current collector exposed portion 212 and the negative electrode 22.

[0041] The insulating layer 21C covers a facing portion FP (described later) of the positive electrode current collector exposed portion 212 that faces the negative electrode active material layer 22B (described later) across the separator 23, and has an elongation percentage of, for example, 180% or more. The insulating layer 21C may be a resin containing modified PVDF (polyvinylidene fluoride) or copolymer PVDF. The inclusion of modified PVDF or copolymer PVDF in the insulating layer 21C allows the insulating layer 21C to swell with, for example, a solvent contained in the electrolyte solution, thereby enabling good adhesion to the separator 23. The inclusion of modified PVDF or copolymer PVDF in the insulating layer 21C also results in better elongation. Examples of materials for the insulating layer 21C include PVDF modified or copolymerized with TFE (tetrafluoroethylene), HFP (hexafluoropropylene), acrylic acid, and maleic acid.

[0042] (Insulating Tapes 53, 54) The secondary battery 1 may further include insulating tapes 53, 54 in the gap between the outer can 11 and the electrode winding 20. The positive electrode current collector exposed portion 212 and the negative electrode current collector exposed portion 222, which are gathered at the upper end surface 41 and the lower end surface 42, are conductors such as bare metal foil. Therefore, if the positive electrode current collector exposed portion 212 and the negative electrode current collector exposed portion 222 are in close proximity to the outer can 11, a short circuit may occur between the positive electrode 21 and the negative electrode 22 through the outer can 11. Furthermore, if the positive electrode current collector plate 24 on the upper end surface 41 comes close to the outer can 11, a short circuit may also occur. 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 whose base layer is made of one of polypropylene, polyethylene terephthalate, and polyimide and whose base layer has an adhesive layer on one surface. In order to prevent the installation of the insulating tapes 53, 54 from reducing the volume of the electrode winding body 20, the insulating tapes 53, 54 are positioned so as not to overlap with the fixing tape 46 attached to the side portion 45, and the thickness of the insulating tapes 53, 54 is set to be equal to or less than the thickness of the fixing tape 46.

[0043] (Positive current collector 24 and negative current collector 25) In a typical lithium-ion secondary battery, for example, a lead for current extraction is welded to each of the positive and negative electrodes. However, this increases the internal resistance of the lithium-ion secondary battery and causes the lithium-ion secondary battery to heat up and reach high temperatures during discharge, making it unsuitable for high-rate discharge. Therefore, in the secondary battery 1 of this embodiment, the positive current collector 24 is positioned opposite the upper end face 41 and the negative current collector 25 is positioned opposite the lower end face 42. The positive current collector cover 211 at the upper end face 41 is welded to the positive current collector 24 at multiple points, and the negative current collector cover 221 at the lower end face 42 is welded to the negative current collector 25 at multiple points. This reduces the internal resistance of the secondary battery 1. The flat surfaces of the upper end face 41 and the lower end face 42, as described above, also contribute to the low resistance. The positive current collector 24 is disposed between the battery lid 14 and the upper end surface 41. The positive current collector 24 is electrically connected to the battery lid 14, for example, via a safety valve mechanism 30. The negative current collector 25 is disposed between the bottom 11B of the outer can 11 and the lower end surface 42. The negative current collector 25 is electrically connected to the inner surface of the bottom 11B of the outer can 11, for example. FIG. 7A is a developed view showing an example of the configuration of the positive current collector 24. FIG. 7B is a developed view showing an example of the configuration of the negative current collector 25. The positive current collector 24 is a metal plate made of, for example, aluminum or an aluminum alloy, or a composite material thereof. The negative current collector 25 is a metal plate made of, for example, nickel, a nickel alloy, copper, or a copper alloy, or a composite material of two or more of these.

[0044] As shown in FIG. 7A , the positive current collector 24 has a substantially sector-shaped fan portion 31 and a substantially rectangular strip portion 32. However, the shape of the positive current collector 24 is not limited to the shape shown in FIG. 6A and can be selected arbitrarily. In the secondary battery 1, the positive current collector 24 is housed in the outer can 11 with the strip portion 32 folded relative to the fan portion 31, as shown in FIG. 1 . FIG. 7A shows the positive current collector 24 in an unfolded state. The fan portion 31 is a facing portion that faces and connects to the upper end surface 41. The fan portion 31 has an outer edge that includes, for example, straight and curved portions. An opening 35 is formed near the center of the fan portion 31. FIG. 7A illustrates a case in which the opening 35 has a circular planar shape in a horizontal plane perpendicular to the Z-axis direction. The strip portion 32 is connected to, for example, a straight portion of the outer edge of the fan portion 31. The strip portion 32 extends in a direction intersecting with the straight portion 31S of the sector portion 31. As shown in Fig. 1 , in the secondary battery 1, the positive electrode current collector plate 24 is provided so that the opening 35 overlaps with the through hole 26 in the Z-axis direction. That is, the opening 35 is provided at a position that overlaps with a part of the upper end surface 41 on the winding center side in the Z-axis direction.

[0045] The shaded portion in FIG. 6A is the insulating portion 32A of the strip portion 32. The insulating portion 32A is a portion of the strip portion 32 to which insulating tape is attached or an insulating material is applied. The portion of the strip portion 32 below the insulating portion 32A is a connection portion 32B to the sealing plate, which also serves as an external terminal. The sealing plate is electrically connected to the battery cover 14. Note that, as shown in FIG. 1 , if the secondary battery 1 has a battery structure without a metal center pin in the through hole 26, the strip portion 32 is unlikely to come into contact with a portion of the negative electrode potential. Therefore, the positive electrode current collector 24 may not have the insulating portion 32A. If the positive electrode current collector 24 does not have the insulating portion 32A, the charge / discharge capacity can be increased by increasing the width between the positive electrode 21 and the negative electrode 22 by an amount corresponding to the thickness of the insulating portion 32A.

[0046] The shape of the negative electrode current collector 25 shown in FIG. 6B is almost the same as the shape of the positive electrode current collector 24 shown in FIG. 6A . The negative electrode current collector 25 has a substantially sector-shaped fan portion 33 and a substantially rectangular band portion 34. However, the shape of the negative electrode current collector 25 is not limited to the shape shown in FIG. 6B and can be selected arbitrarily. In the secondary battery 1, the negative electrode current collector 25 is housed in the outer can 11 with the band portion 34 folded relative to the fan portion 33, as shown in FIG. 1 . FIG. 6B shows the negative electrode current collector 25 in an unfolded state. The fan portion 33 is a facing portion that faces and is connected to the lower end surface 42. The fan portion 33 has an outer edge that includes, for example, a straight portion and a curved portion. The band portion 34 is connected to, for example, a straight portion 33S of the outer edge of the fan portion 33. The band portion 34 extends in a direction that intersects with the straight portion of the fan portion 33. The strip portion 34 of the negative current collector 25 is shorter than the strip portion 32 of the positive current collector 24 and does not have a portion corresponding to the insulating portion 32A of the positive current collector 24. The strip portion 34 has a plurality of circular protrusions 37 indicated by circles. At least some of the protrusions 37 are welded to the bottom 11B of the outer can 11. During resistance welding, current concentrates on the protrusions 37, melting the protrusions 37 and welding the strip portion 34 to the bottom 11B of the outer can 11. Similar to the positive current collector 24, the negative current collector 25 has an opening 36 formed near the center of the sector-shaped portion 33. In the secondary battery 1, the negative current collector 25 is provided with the opening 36 overlapping the through-hole 26 in the Z-axis direction. FIG. 6B illustrates an example in which the opening 36 has a circular planar shape in a horizontal plane perpendicular to the Z-axis direction.

[0047] Due to its planar shape, the sector-shaped portion 31 of the positive current collector 24 covers only a portion of the upper end surface 41. Similarly, due to its planar shape, the sector-shaped portion 33 of the negative current collector 25 covers only a portion of the lower end surface 42. The sector-shaped portions 31 and 33 do not cover the entire upper end surface 41 and the entire lower end surface 42, for example, for the following two reasons. The first reason is to allow the electrolyte to smoothly penetrate into the electrode winding 20, for example, when assembling the secondary battery 1. In particular, in the secondary battery 1 of this embodiment, the positive current collector 24 is provided so that the opening 35 overlaps with a portion of the upper end surface 41 toward the center of the winding in the Z-axis direction. Therefore, a portion of the positive edge portion 212E constituting the upper end surface 41 is not covered by the sector-shaped portion 31 of the positive current collector 24 and is exposed to the opening 35. Therefore, the secondary battery 1 has a structure that allows the electrolyte to penetrate into the electrode winding 20 more quickly. The second reason is to facilitate the release of gas generated when the lithium ion secondary battery is in an abnormally high temperature state or an overcharged state.

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

[0049] (Positive Electrode Active Material Layer 21B) The positive electrode active material layer 21B contains, as the positive electrode active material, one or more positive electrode materials capable of absorbing and releasing lithium. 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 conductor. The positive electrode material is preferably a lithium-containing compound, more specifically, a lithium-containing composite oxide or a lithium-containing phosphate compound. The lithium-containing composite oxide is an oxide containing lithium and one or more other elements, i.e., elements other than lithium, as constituent elements. The lithium-containing composite oxide has, for example, a layered rock salt type or a spinel type crystal structure. The lithium-containing phosphate compound is a phosphate compound containing lithium and one or more other elements as constituent elements, and has, for example, an olivine type crystal structure. The positive electrode active material layer 21B preferably contains 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 includes, for example, one or more of synthetic rubber and polymer compounds. Examples of synthetic rubber include styrene butadiene rubber, fluorine-based rubber, and ethylene propylene diene. Examples of polymer compounds include polyvinylidene fluoride and polyimide. The positive electrode conductive agent includes, for example, one or more of 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. The surface of the negative electrode current collector 22A is preferably roughened. This is because the so-called anchor effect improves adhesion of the negative electrode active material layer 22B to the negative electrode current collector 22A. In this case, it is sufficient that the surface of the negative electrode current collector 22A is roughened at least in the region facing the negative electrode active material layer 22B. The roughening method may be, for example, a method of forming fine particles using an electrolytic process. In the electrolytic process, fine particles are formed on the surface of the negative electrode current collector 22A by electrolysis in an electrolytic bath, resulting in an uneven surface of the negative electrode current collector 22A. Copper foil produced by an electrolytic process is generally called electrolytic copper foil.

[0051] (Negative Electrode Active Material Layer 22B) The negative electrode active material layer 22B contains, as the negative electrode active material, one or more negative electrode materials capable of absorbing and releasing lithium. 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 conductor. The negative electrode material is, for example, a carbon material. This is because the crystal structure undergoes minimal change upon lithium absorption and desorption, thereby enabling a stable high energy density. Furthermore, the carbon material also functions as a negative electrode conductor, thereby improving the conductivity of the negative electrode active material layer 22B. Examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite. However, the interplanar spacing of the (002) plane of non-graphitizable carbon is preferably 0.37 nm or more. The interplanar spacing of the (002) plane of graphite is preferably 0.34 nm or less. More specifically, carbon materials include, for example, pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound calcined bodies, activated carbon, and carbon blacks. Examples of cokes include pitch coke, needle coke, and petroleum coke. Organic polymer compound calcined bodies are formed by calcining (carbonizing) polymer compounds such as phenolic resins and furan resins at an appropriate temperature. Alternatively, the carbon material may be low-crystalline carbon heat-treated at temperatures below approximately 1000°C, or amorphous carbon. The carbon material may be fibrous, spherical, granular, or flake-shaped. In the secondary battery 1, when the open-circuit voltage at full charge, i.e., the battery voltage, is 4.25 V or higher, the amount of lithium released per unit mass is greater than when the open-circuit voltage at full charge is 4.20 V, even when the same positive electrode active material is used. Therefore, the amounts of positive and negative electrode active materials are adjusted accordingly. This results in a high energy density.

[0052] The negative electrode active material layer 22B may also contain a silicon-containing material containing at least one of silicon, silicon oxide, carbon-silicon compound, and silicon alloy as the negative electrode active material. A silicon-containing material is a general term for materials containing silicon as a constituent element. However, a silicon-containing material may contain only silicon as a constituent element. The silicon-containing material may be of one type or two or more types. The silicon-containing material is capable of forming an alloy with lithium and may be silicon itself, a silicon alloy, a silicon compound, a mixture of two or more of these, or a material containing one or more of these phases. The silicon-containing material may be crystalline, amorphous, or contain both crystalline and amorphous portions. However, the element described here refers to a general element and may contain trace amounts of impurities. In other words, the purity of the element is not necessarily limited to 100%. Silicon alloys contain, for example, one or more of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, chromium, etc. as constituent elements other than silicon. Silicon compounds contain, for example, one or more of carbon, oxygen, etc. as constituent elements other than silicon. Note that silicon compounds may contain, for example, one or more of the series of constituent elements described for silicon alloys as constituent elements other than silicon. Specifically, silicon alloys and silicon compounds include, for example, SiB 4 , SiB 6 , Mg 2 Si, Ni 2 Si, TiSi 2 , MoSi 2 , CoSi 2 , NiSi 2 , CaSi 2 , CrSi 2 , Cu 5 Si, FeSi 2 , MnSi 2 , NbSi 2 , TaSi 2 , VSi 2 , WSi 2 , ZnSi2 , SiC, Si 3 N 4 , Si 2 N 2 O and SiO v (0<v≦2), etc. However, the range of v can be set arbitrarily, and may be, for example, 0.2<v<1.4.

[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 current short-circuiting due to contact between the positive electrode 21 and the negative electrode 22. The separator 23 may be made of one or more types of porous membranes, such as synthetic resins and ceramics, or may be a laminated membrane of two or more types of porous membranes. Examples of synthetic resins include polytetrafluoroethylene, polypropylene, and polyethylene. However, the separator 23 preferably has a substrate made of a single-layer polyolefin porous membrane containing polyethylene. This is because better high-output characteristics can be obtained compared to laminated membranes. When the first separator member 23A and the second separator member constituting the separator 23 are each a single-layer porous membrane made of polyolefin, the thickness of the porous membrane may be, for example, 10 μm or more and 15 μm or less. By making the single-layer porous membrane made of polyolefin 10 μm or more thick, internal short-circuiting can be sufficiently avoided. If the thickness of the single-layer porous film made of polyolefin is 15 μm or less, better discharge capacity characteristics can be obtained. In addition, the surface density of the porous film is, for example, 6.3 g / m ２ 8.3g / m or more ２ The surface density of the single-layer porous film made of polyolefin is preferably 6.3 g / m or less. ２ If the surface density of the single-layer porous film made of polyolefin is 8.3 g / m or more, internal short circuits can be sufficiently avoided. ２ If the content is less than this, better discharge capacity characteristics can be obtained.

[0054] In particular, the separator 23 may include, for example, the porous membrane as the substrate 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 each of the positive electrode 21 and the negative electrode 22 is improved, thereby suppressing distortion of the electrode winding body 20. This suppresses decomposition reactions of the electrolyte and also suppresses leakage of the electrolyte impregnated in the substrate layer, thereby making it difficult for resistance to increase even with repeated charge and discharge, and suppressing battery swelling. The polymer compound layer includes, for example, a polymer compound such as polyvinylidene fluoride. This is because it has excellent physical strength and is electrochemically stable. However, the polymer compound may be other than polyvinylidene fluoride. To form this polymer compound layer, for example, a solution in which a polymer compound is dissolved in an organic solvent or the like is applied to the substrate layer, and the substrate layer is then dried. Alternatively, the substrate layer may be immersed in the solution and then dried. The polymer compound layer may contain one or more types of insulating particles such as inorganic particles, for example, aluminum oxide and aluminum nitride.

[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, a fluorine compound and a dinitrile compound. The fluorine compound may include, for example, at least one of fluorinated ethylene carbonate, trifluorocarbonate, trifluoroethyl methyl carbonate, fluorinated carboxylic acid ester, and fluorinated ether. The non-aqueous solvent may also contain a nitrile compound other than a dinitrile compound, such as at least one of a mononitrile compound or a tritolyl compound. As the dinitrile compound, succinonitrile (SN) is preferable. However, the dinitrile compound is not limited to succinonitrile, and may be other dinitrile compounds, such as adiponitrile.

[0056] The electrolyte salt may include one or more salts, such as a lithium salt. However, the electrolyte salt may include a salt other than a lithium salt. The salt other than lithium may be, for example, a salt of a light metal other than lithium. Examples of the lithium salt include lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), dilithium hexafluorosilicate (Li2SF6), lithium chloride (LiCl), and lithium bromide (LiBr). Among these, one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate are preferred, with lithium hexafluorophosphate 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 solution contains LiPF as the electrolyte salt, ６ When the electrolyte contains LiPF ６ The concentration of the electrolyte salt is preferably 1.25 mol / kg or more and 1.45 mol / kg or less. This is because it is possible to prevent cycle deterioration due to salt consumption (decomposition) during high-load rate charging, thereby improving high-load cycle characteristics. ６ In addition to LiBF ４ When further containing LiBF in the electrolyte ４ The concentration of salt is preferably 0.001 (wt %) or more and 0.1 (wt %) or less, because this more effectively prevents cycle deterioration due to 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 are absorbed into the negative electrode 22 via the electrolyte. In addition, in the secondary battery 1, for example, during discharging, lithium ions are released from the negative electrode 22 and are absorbed into the positive electrode 21 via the electrolyte.

[0058] 1-3. Manufacturing Method] A method for manufacturing the secondary battery 1 will be described with reference to Fig. 8 in addition to Fig. 1 to Fig. 7. Fig. 8 is a perspective view illustrating the manufacturing process of the secondary battery shown in Fig. 1.

[0059] First, a positive electrode current collector 21A is prepared, and a positive electrode active material layer 21B is selectively formed on the surface of the positive electrode current collector 21A to form a positive electrode 21 having a positive electrode current collector coating portion 211 and a positive electrode current collector exposed portion 212. 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 coating portion 221 and a negative electrode current collector exposed portion 222. A drying treatment may be performed on the positive electrode 21 and the negative electrode 22. Next, a stack S20 is produced by stacking the positive electrode 21 and the negative electrode 22 with the first separator member 23A and the second separator member 23B interposed between them 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 opposite each other in the W-axis direction. Thereafter, the laminate S20 is spirally wound so as to form the through-holes 26. 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 a fixing tape 46 is attached to the outermost periphery of the spirally wound laminate S20, the winding core is removed. In this way, the electrode wound body 20 is obtained as shown in FIG. 8A.

[0060] Next, as shown in Fig. 8B , the edge of a flat plate having a thickness of, for example, 0.5 mm is pressed perpendicularly against the upper end surface 41 and the lower end surface 42 of the electrode winding body 20, i.e., in the Z-axis direction, thereby locally bending a portion of the upper end surface 41 and a portion of the lower end surface 42. As a result, grooves 43 are formed extending radially from the through-holes 26 in the radial direction (direction R). Note that the number and arrangement of grooves 43 shown in Fig. 8B are merely examples and the present disclosure is not limited thereto.

[0061] Next, as shown in FIG. 8C , substantially the same pressure is applied substantially simultaneously from above and below the electrode winding body 20 in a direction generally perpendicular to the upper end face 41 and the lower end face 42. At this time, a rod-shaped jig, for example, is inserted into the through-hole 26. This bends the positive electrode current collector exposed portion 212 and the first portion 222A of the negative electrode current collector exposed portion 222, respectively, so that the upper end face 41 and the lower end face 42 each become flat. At this time, it is preferable that adjacent portions of the positive electrode edge portion 212E of the positive electrode current collector exposed portion 212 on the upper end face 41 bend toward the through-hole 26 so as to overlap with each other in the radial direction of the electrode winding body 20. Similarly, it is preferable that adjacent portions of the negative electrode edge portion 222E of the negative electrode current collector exposed portion 222 on the lower end face 42 bend toward the through-hole 26 so as to overlap with each other in the radial direction of the electrode winding body 20. Thereafter, the sectorial portion 31 of the positive current collector plate 24 is joined to the upper end face 41 by laser welding or the like, and the sectorial portion 33 of the negative current collector 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 predetermined positions of the electrode winding body 20. Thereafter, as shown in Fig. 8(D), the strip portion 32 of the positive current collector plate 24 is bent and inserted into the hole 12H of the insulating plate 12. Also, the strip portion 34 of the negative current collector plate 25 is bent and inserted into the hole 13H of the insulating plate 13.

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

[0064] 8(F), the outer can 11 is sealed using the gasket 15, the safety valve mechanism 30, and the battery lid 14, utilizing the constricted portion 11S. Finally, the outer can 11, with the washer 55 attached to the battery lid 14, is covered with the outer tube 50, and the outer tube 50 is heated and shrunk by applying hot air to the outer tube 50, for example, and the outer tube 50 is then tightly attached to the outer surface of the outer can 11.

[0065] In this way, the secondary battery 1 of this embodiment is completed.

[0066] [1-4. Actions and Effects] As described above, in the secondary battery 1 of this embodiment, the insulating layer 21C covering the facing portion FP of the positive electrode current collector exposed portion 212 that faces the negative electrode active material layer 22B across the separator 23 has an elongation rate of 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 can be effectively prevented from breaking or cracking due to the stretching of the insulating layer 21C against which the foreign matter such as metal powder is pressed. Therefore, short-circuiting between the positive electrode 21 and the negative electrode 22 through the foreign matter can be effectively prevented. Therefore, the secondary battery 1 of this embodiment can ensure excellent safety.

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

[0068] 2. Application Examples The secondary battery 1 according to the embodiment of the present disclosure can be used in the following applications, for example.

[0069] 9 is a block diagram showing an example of a circuit configuration when a battery according to an embodiment of the present invention (hereinafter referred to as a secondary battery) is applied to a battery pack 300. The battery pack 300 includes a battery pack 301, an exterior, a switch unit 304 including a charge control switch 302a and a discharge control switch 303a, a current detection resistor 307, a temperature detection element 308, and a control unit 310.

[0070] The battery pack 300 includes a positive terminal 321 and a negative terminal 322. When charging, the positive terminal 321 and the negative terminal 322 are connected to the positive terminal and the negative terminal of a charger, respectively, for charging. When using the electronic device, the positive terminal 321 and the negative terminal 322 are connected to the positive terminal and the negative terminal of the electronic device, respectively, for discharging.

[0071] The battery pack 301 is formed by connecting a plurality of secondary batteries 301a in series or parallel. The secondary batteries 301a can be the secondary batteries 1 described above. While Fig. 9 shows an example in which six secondary batteries 301a are connected in a 2-parallel-3-series (2P3S) configuration, any other connection method, such as n-parallel or m-series (n and m are integers), is also acceptable.

[0072] The switch unit 304 includes a charge control switch 302a and a diode 302b, as well as a discharge control switch 303a and a diode 303b, and is controlled by the control unit 310. The diode 302b has a polarity opposite to the charge current flowing from the positive terminal 321 to the battery pack 301, and a polarity forward to the discharge current flowing from the negative terminal 322 to the battery pack 301. The diode 303b has a polarity forward to the charge current and opposite to the polarity of the discharge current. Although the switch unit 304 is provided on the + side in FIG. 9, it may also be provided on the - side.

[0073] The charge control switch 302a is controlled by the charge / discharge control unit so that it is turned off when the battery voltage reaches the overcharge detection voltage and so that no charging current flows in the current path of the battery pack 301. After the charge control switch 302a is turned off, only discharging is possible via the diode 302b. Furthermore, the control unit 310 controls the switch so that it is turned off when a large current flows during charging and so that the charging current flows in the current path of the battery pack 301. The discharge control switch 303a is controlled by the control unit 310 so that it is turned off when the battery voltage reaches the overdischarge detection voltage and so that no discharging current flows in 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, the control unit 310 controls the switch so that it is turned off when a large current flows during discharging and so that the discharging current flows in the current path of the battery pack 301.

[0074] The temperature detection element 308 is, for example, a thermistor, and is provided near the battery pack 301. It measures the temperature of the battery pack 301 and supplies 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 301, A / D converts the 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] When the voltage of any of the multiple secondary batteries 301a falls below the overcharge detection voltage or the overdischarge detection voltage, or when a large current suddenly flows, the switch control unit 314 sends a control signal to the switch unit 304 to prevent overcharging, overdischarging, and overcurrent charging / discharging. Here, for example, if the secondary battery is a lithium-ion secondary battery, the overcharge detection voltage is set to, for example, 4.20 V±0.05 V, and the overdischarge detection voltage is set to, for example, 2.4 V±0.1 V.

[0076] The charge / discharge switches can be semiconductor switches such as MOSFETs. In this case, the parasitic diodes of the MOSFETs function as diodes 302b and 303b. When P-channel FETs are used as the charge / discharge switches, switch control unit 314 supplies control signals DO and CO to the gates of charge control switch 302a and discharge control switch 303a, respectively. When charge control switch 302a and discharge control switch 303a are P-channel, they are turned ON by a gate potential that is lower than the source potential by a predetermined value or more. That is, during normal charge and discharge operations, control signals CO and DO are set to a low level, and charge control switch 302a and discharge control switch 303a are turned ON.

[0077] For example, in the event of overcharging or overdischarging, the control signals CO and DO are set to high level, and the charge control switch 302a and the discharge control switch 303a are set to the OFF state.

[0078] The memory 317 is made up of RAM or ROM, such as a non-volatile memory such as an erasable programmable read-only memory (EPROM). Numerical values ​​calculated by the control unit 310 and the internal resistance values ​​of the secondary batteries 301a in their initial states measured during the manufacturing process are stored in advance in the memory 317, and the memory 317 can be rewritten as needed. Furthermore, by storing the full charge capacity of the secondary batteries 301a, the remaining capacity can be calculated together with the control unit 310.

[0079] The temperature detection unit 318 measures the temperature using the temperature detection element 308, and controls charging and discharging when abnormal heat is generated, and corrects the calculation of the remaining capacity.

[0080] [2-2. Power Storage System] The secondary battery according to the embodiment of the present disclosure described above can be mounted on devices such as electronic devices, electric vehicles, electric aircraft, and power storage devices, or can be used to supply power.

[0081] Examples of electronic devices include notebook computers, smartphones, tablet devices, PDAs (personal digital assistants), mobile phones, wearable devices, cordless phone handsets, video movie players, digital still cameras, e-books, electronic dictionaries, music players, radios, headphones, game consoles, navigation systems, memory cards, pacemakers, hearing aids, power tools, electric shavers, refrigerators, air conditioners, televisions, stereos, water heaters, microwave ovens, dishwashers, washing machines, dryers, lighting equipment, toys, medical equipment, robots, road conditioners, and traffic lights.

[0082] Examples of electric vehicles include railcars, golf carts, electric carts, electric vehicles (including hybrid vehicles), and the like, and the device is used as a driving power source or auxiliary power source for these. Examples of power storage devices include power storage power sources for buildings such as homes, or for power generation facilities.

[0083] An embodiment of the present disclosure will be described.

[0084] [Fabrication Method] Example 1 As described below, a cylindrical secondary battery shown in Fig. 1 was fabricated. Here, a lithium ion secondary battery having nominal dimensions of 21 mm in diameter and 70 mm in length was fabricated.

[0085] First, a 12 μm thick aluminum foil was prepared as the positive electrode current collector 21A. Next, a layered lithium oxide having a Ni ratio of 85% or more in lithium nickel cobalt aluminum oxide (NCA) was used as the positive electrode active material. A positive electrode binder made of polyvinylidene fluoride was mixed with a conductive additive containing carbon black, acetylene black, and ketjen black to obtain a positive electrode mixture. The mixture ratio of the positive electrode active material, positive electrode binder, and conductive additive was 96.4:2:1.6. Next, the positive electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like positive electrode mixture slurry. Next, the positive electrode mixture slurry was applied to predetermined areas on both sides of the positive electrode current collector 21A using a coating device, and the positive electrode mixture slurry was then dried to form the positive electrode active material layer 21B. Furthermore, a coating of PVDF copolymerized with TFE was applied to the surface of the positive electrode current collector exposed portion 212 adjacent to the positive electrode current collector covering portion 211, and the coating was dried to form an insulating layer 21C having a width of 3 mm and a thickness of 8 μm. The positive electrode active material layer 21B was then compression-molded using a roll press. This resulted in a positive electrode 21 having the positive electrode current collector covering portion 211 and the positive electrode current collector exposed portion 212. The positive electrode 21 was then sheared to set the width of the positive electrode current collector covering portion 211 in the W-axis direction to 60 mm, and the width of the positive electrode current collector exposed portion 212 in the W-axis direction to 7 mm. The length of the positive electrode 21 in the L-axis direction was set to 1,700 mm.

[0086] Additionally, an 8 μm thick copper foil was prepared as the negative electrode current collector 22A. Next, a negative electrode active material consisting of a mixture of a carbon material made of graphite and SiO was prepared. A negative electrode binder consisting of polyvinylidene fluoride was mixed with a conductive additive consisting of a mixture of carbon black, acetylene black, and ketjen black to obtain a negative electrode mixture. The mixing ratio of the negative electrode active material, the negative electrode binder, and the conductive additive was 96.1:2.9:1.0. Furthermore, the mixing ratio of graphite to SiO in the negative electrode active material was 95:5. Subsequently, the negative electrode mixture was introduced into an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like negative electrode mixture slurry. Next, a coating device was used to apply the anode mixture slurry to predetermined regions on both sides of the anode current collector 22A, and the anode mixture slurry was then dried to form the anode active material layer 22B. The anode active material layer 22B was then compression-molded using a roll press. This resulted in a anode 22 having an anode current collector covering portion 221 and an anode current collector exposed portion 222. The anode 22 was then sheared to set the width of the anode current collector covering portion 221 in the W-axis direction to 62 mm, and the width of the first portion 222A of the anode current collector exposed portion 222 in the W-axis direction to 4 mm. The length of the anode 22 in the L-axis direction was 1,760 mm.

[0087] Next, the positive electrode 21 and the negative electrode 22 were stacked with the first separator member 23A and the second separator member 23B interposed therebetween so that the positive electrode current collector exposed portion 212 and the first portion 222A of the negative electrode current collector exposed portion 222 were opposite each other in the W-axis direction, thereby producing a laminate S20. The laminate S20 was produced so that the positive electrode active material layer 21B did not protrude from the negative electrode active material layer 22B in the W-axis direction. Polyethylene sheets having a width of 65 mm and a thickness of 14 μm were used as the first separator member 23A and the second separator member 23B. The laminate S20 was then spirally wound to form through-holes 26, and a fixing tape 46 was attached to the outermost periphery of the wound laminate S20.

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

[0089] Subsequently, substantially the same pressure was applied from above and below the electrode winding body 20 in a direction substantially perpendicular to the upper end face 41 and the lower end face 42 at the same time. As a result, the positive electrode current collector exposed portion 212 and the first portion 222A of the negative electrode current collector exposed portion 222 were each folded, making the upper end face 41 and the lower end face 42 flat. At this time, the positive electrode edge portion 212E of the positive electrode current collector exposed portion 212 and the negative electrode edge portion 222E of the negative electrode current collector exposed portion 222 at the upper end face 41 and the lower end face 42 were folded while overlapping toward the through hole 26. Thereafter, the sector-shaped portion 31 of the positive electrode current collector 24 was joined to the upper end face 41 by laser welding, and the sector-shaped portion 33 of the negative electrode current collector 25 was joined to the lower end face 42 by laser welding.

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

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

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

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

[0094] Finally, the gasket 15, the safety valve mechanism 30, and the battery cover 14 are sealed using the narrowed portion 11S.

[0095] In this way, the secondary battery of Example 1 was obtained.

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

[0097] Example 3 The secondary battery of Example 3 was fabricated in the same manner as the secondary battery of Example 1, except that an insulating layer 21C having a width of 3 mm and a thickness of 8 μm was formed by applying and drying a paint of PVDF modified with acrylic acid when fabricating the positive electrode 21.

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

[0099] (Comparative Example 1) When fabricating the positive electrode 21, an insulating layer 21C having 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 fabricated in the same manner as the secondary battery of Example 1.

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

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

[0102] [Evaluation of Battery Characteristics] Measurements of tensile strength and elongation, and a forced internal short circuit test were carried out for each of the secondary batteries obtained as described above in Examples 1 to 4 and Comparative Examples 1 to 6. The results are summarized in Table 1.

[0103]

[0104] (Tensile Strength and Elongation) Strip-shaped samples were taken from the insulating layer 21C used in each of the secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 6, and a tensile test was conducted in accordance with the provisions of "JIS K 7161-2014 Plastics - Test Method for Tensile Properties," to measure the tensile strength (maximum stress observed during the test) [N] and the elongation [%] until the test piece broke. The dimensions of the test piece were a length between the gripping tools of 10 mm (60 mm including the gripping part) and a width of 3 mm. The tensile speed was 10 mm / min.

[0105] (Forced Internal Short-Circuit Test) For each of the secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 6, a "Forced Internal Short-Circuit Test for a Single Cell" was conducted in accordance with "JIS C8714:2007 Safety Test for Cells and Assembled Cells of Lithium-Ion Storage Batteries for Portable Electronic Devices." Specifically, the electrode winding of each secondary battery was unfolded, and a small nickel piece (L-shaped, 0.2 mm high, 0.1 mm wide, and 1 mm on each side) was sandwiched between the insulating layer 21C covering the positive electrode current collector 21A and the negative electrode active material layer 22B, and the electrode winding was then unwound. The electrode winding was then placed in a thermostatic chamber set to a predetermined temperature, and pressure was applied to the portion where the nickel piece was sandwiched. The pressure was applied by pressing a pressure jig against the portion of the electrode winding where the nickel piece was sandwiched at a rate of 0.1 mm / sec until a force of 800 N was applied. Here, when a voltage drop of 50 mV or more from the initial voltage was detected, it was judged to be a short circuit, and if a short circuit was found, the test was terminated at that point.

[0106] As shown in Table 1, in the forced internal short circuit test, short circuits occurred in all of the comparative examples 1 to 6, whereas no short circuits occurred in any of the examples 1 to 4. This is thought to be because the elongation percentages of the examples 1 to 4 were 180% or more, so even if foreign matter was present, cracks or breaks did not occur in the insulating layer 21C.

[0107] From the above results, it was confirmed that the secondary battery of the present 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, the insulating layer 21C is made of a material containing modified PVDF or copolymer PVDF, but the present disclosure is not limited to this and other types of resin materials can be used.

[0109] Furthermore, in the above embodiment and example, a cylindrical secondary battery having an electrode wound body with a circular cross section has been described, but the present disclosure is not limited to this. For example, a prismatic secondary battery having an electrode wound body with a flattened elliptical cross section may also be used.

[0110] In addition, although the above embodiment and examples have been described with reference to a case where the electrode reactant is lithium, the electrode reactant is not particularly limited. Therefore, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0111] The effects described in this specification are merely examples, and the effects of the present disclosure are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present disclosure.

[0112] The present disclosure may take the following forms: <1> An electrode winding body, comprising: 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, the electrode winding body being formed by winding a laminate including a positive electrode, a negative electrode, and a separator around a through hole that penetrates the laminate in a height direction, the electrode winding body having a first end face facing the positive electrode current collector in the height direction and a second end face facing the negative electrode current collector in the height direction, the positive electrode including a positive electrode current collector and a positive electrode active material layer covering a portion of the positive electrode current collector, and an insulating layer, the positive electrode including a positive electrode current collector covered portion in which the positive electrode current collector is covered with the positive electrode active material layer, and a positive electrode current collector exposed portion in which the positive electrode current collector is exposed and not covered by the positive electrode active material layer, at least a portion of the positive electrode current collector exposed portion constituting the first end face and being connected to the positive electrode current collector, a negative electrode current collector covering portion in which the negative electrode current collector is covered with the negative electrode active material layer, and a negative electrode current collector exposed portion in which the negative electrode current collector is exposed and not covered with the negative electrode active material layer, at least a portion of the negative electrode current collector exposed portion forms the second end face and is connected to the negative electrode current collector plate, and the insulating layer covers a portion of the positive electrode current collector exposed portion that faces the negative electrode active material layer across the separator, and has an elongation of 180% or more. <2> The secondary battery according to <1> above, wherein the length in the height direction of the negative electrode active material layer is longer than the length in the height direction of the positive electrode active material layer. <3> The secondary battery according to <1> or <2> above, wherein the insulating layer contains modified PVDF (polyvinylidene fluoride) or copolymer PVDF. <4> The secondary battery according to any one of <1> to <3>, wherein the insulating layer is formed by modifying or copolymerizing PVDF with TFE (tetrafluoroethylene), HFP (hexafluoropropylene), acrylic acid, and maleic acid.<5> The secondary battery according to any one of <1> to <4>, wherein the first end surface is formed by bending an edge of the positive current collector exposed portion toward the through hole in a wound state, and the second end surface is formed by bending an edge of the negative current collector exposed portion toward the through hole in a wound state. <6> The secondary battery according to any one of <1> to <5>, further comprising: a lid connected to the positive current collector; and an outer can that houses the positive current collector, the negative current collector, and the electrode wound body and is connected to the negative current collector, wherein the outer can has a bottom and a wall that stands in the height direction along an outer edge of the bottom to surround the electrode wound body and includes an open end on the side opposite to the bottom, the open end being open so that the electrode wound body can be inserted therethrough, and the lid closes the open end of the outer can. <7> A battery pack including: the secondary battery according to any one of <1> to <6> above; a control unit that controls the secondary battery; and an exterior body that encapsulates the secondary battery.

Claims

1. a positive current collector plate, a negative current collector plate, an electrode wound body in which a laminate disposed between the positive current collector plate and the negative current collector plate and having a through hole penetrating in the height direction and including a positive electrode, a negative electrode, and a separator is wound, and comprising, the electrode wound body has a first end face facing the positive current collector plate in the height direction and a second end face facing the negative current collector plate in the height direction, the positive electrode includes a positive current collector and a positive electrode active material layer covering a part of the positive current collector and an insulating layer, the positive electrode includes a positive current collector covered portion where the positive current collector is covered by the positive electrode active material layer and a positive current collector exposed portion where the positive current collector is exposed without being covered by the positive electrode active material layer, at least a part of the positive current collector exposed portion constitutes the first end face and is connected to the positive current collector plate, the negative electrode includes a negative current collector and a negative electrode active material layer covering a part of the negative current collector, the negative electrode includes a negative current collector covered portion where the negative current collector is covered by the negative electrode active material layer and a negative current collector exposed portion where the negative current collector is exposed without being covered by the negative electrode active material layer, at least a part of the negative current collector exposed portion constitutes the second end face and is connected to the negative current collector plate, the insulating layer covers a facing portion of the positive current collector exposed portion that faces the negative electrode active material layer with the separator interposed therebetween 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 one in which PVDF is 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 being bent toward the through hole in a state where the edge of the positive current collector exposed portion is wound, the second end face is formed by being bent toward the through hole in a state where the edge of the negative current collector exposed portion is wound The secondary battery according to claim 1.

6. a lid portion connected to the positive current collector plate, Further comprising an exterior can that houses the positive electrode current collector, the negative electrode current collector, and the electrode wound body and is connected to the negative electrode current collector. The exterior can has a bottom portion and a wall portion that includes an open end portion that stands upright in the height direction along the outer edge of the bottom portion so as to surround the electrode wound body and is open so that the electrode wound body can be inserted, on the side opposite to the bottom portion. The lid portion covers the open end portion of the exterior can. The secondary battery according to claim 1.

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