Rechargeable batteries and battery packs

Abstract

To provide a secondary battery with excellent performance. [Solution] This secondary battery comprises an electrode winding body in which a laminate containing a first electrode, a second electrode, and a separator is wound along the longitudinal direction of the laminate and has through holes penetrating in the width direction perpendicular to the longitudinal direction, and a first electrode current collector plate and a second electrode current collector plate facing each other on either side of the electrode winding body in the width direction. The electrode winding body has a first end face facing the first electrode current collector plate in the width direction and a second end face facing the second electrode current collector plate in the width direction. The first electrode current collector plate and the first end face are joined by one or more first joints. Each of the one or more first joints has a meander-shaped planar form including a plurality of first linear portions and a plurality of first folded portions. In each of the one or more first joints, the length in the winding direction from the a-th first folded portion to the a+1-th first folded portion of the first joint is longer than the length in the winding direction from the first first folded portion to the second first folded portion, counting from the winding center of the electrode winding body.

Description

Technical Field

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

Background Art

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

[0003] In Patent Document 1, a secondary battery has been proposed that adopts a so-called tabless structure to reduce internal resistance and enable charge and discharge with a relatively large current.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

[0006] Therefore, a secondary battery having excellent performance is desired.

Means for Solving the Problems

[0007] A secondary battery according to one embodiment of the present disclosure comprises an electrode winding body in which a laminate including a first electrode, a second electrode, and a separator is wound along the longitudinal direction of the laminate and has through holes penetrating in a width direction perpendicular to the longitudinal direction, and a first electrode current collector plate and a second electrode current collector plate facing each other on either side of the electrode winding body in the width direction. The electrode winding body has a first end face facing the first electrode current collector plate in the width direction and a second end face facing the second electrode current collector plate in the width direction. Each of the one or more first joints formed by joining the first electrode current collector plate and the first end face has a meander-shaped planar form in a plane perpendicular to the through hole, including a plurality of first linear portions adjacent in the radial direction of the electrode winding body and a plurality of first folded portions connecting the plurality of first linear portions. In each of the one or more first junctions, when the number of first folded portions is n (where n is a natural number), the length in the winding direction from the a-th (where a is a natural number between 2 and n) first folded portion to the a+1-th first folded portion, counting from the winding center of the electrode winding body, is longer than the length in the winding direction from the first first folded portion to the second first folded portion, counting from the winding center of the electrode winding body. [Effects of the Invention]

[0008] According to one embodiment of the secondary battery of this disclosure, each of the one or more first junctions has a meander-shaped planar form, and the length in the winding direction of the first junction from the a-th first fold portion to the a+1-th first fold portion, counting from the winding center, is longer than the length in the winding direction from the first first fold portion to the second first fold portion, counting from the winding center of the electrode winding body, among the plurality of first fold portions of the first junction. Therefore, current can be extracted evenly from the entire laminate from the innermost to the outermost part of the electrode winding body. Thus, high output can be obtained. Thus, the secondary battery of one embodiment of the present disclosure achieves excellent performance.

[0009] Furthermore, the effects of this disclosure are not necessarily limited to those described herein, but may include any of the effects of the series of effects related to this disclosure described later. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a cross-sectional view showing an example of a vertical cross-sectional structure along the height direction of a secondary battery in one embodiment of the present disclosure. [Figure 2] Figure 2 is a schematic diagram showing one example of the configuration of a laminate including the positive electrode, negative electrode, and separator shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view showing one example of the horizontal cross-sectional structure of the electrode winding body shown in Figure 1. [Figure 4A] Figure 4A is an exploded view of the positive electrode shown in Figure 1. [Figure 4B] Figure 4B is a cross-sectional view of the positive electrode shown in Figure 1. [Figure 5A] Figure 5A is an unfolded view of the negative electrode shown in Figure 1. [Figure 5B] Figure 5B is a cross-sectional view of the negative electrode shown in Figure 1. [Figure 6A] Figure 6A is a plan view showing the upper end face of the electrode winding shown in Figure 1. [Figure 6B] Figure 6B is a plan view showing the lower end face of the electrode winding shown in Figure 1. [Figure 7A] Figure 7A is a plan view of the positive electrode current collector plate shown in Figure 1. [Figure 7B] Figure 7B is a plan view of the negative electrode current collector plate shown in Figure 1. [Figure 8A] Figure 8A is a plan view showing an example of the configuration of the first joint between the upper end face of the electrode winding body shown in Figure 1 and the positive electrode current collector plate. [Figure 8B] Figure 8B is a plan view showing an example of the configuration of the second joint between the lower end face of the electrode winding body shown in Figure 1 and the negative electrode current collector plate. [Figure 9A] Figure 9A is a schematic plan view showing an enlarged view of the first joint shown in Figure 8A. [Figure 9B]FIG. 9B is a cross-sectional view showing a cross-section of the first joint portion shown in FIG. 8A and its vicinity. [Figure 10A] FIG. 10A is a schematic plan view showing an enlarged view of the second joint portion shown in FIG. 8B. [Figure 10B] FIG. 10B is a cross-sectional view showing a cross-section of the second joint portion shown in FIG. 8B and its vicinity. [Figure 11] FIG. 11 is a perspective view for explaining the manufacturing process of the secondary battery shown in FIG. 1. [Figure 12] FIG. 12 is a block diagram showing a circuit configuration of a battery pack to which the secondary battery according to an embodiment of the present disclosure is applied. [Figure 13A] FIG. 13A is a plan view showing a configuration example of a first joint portion between an upper end surface of an electrode winding body and a positive electrode current collector plate in a secondary battery as a first modification example of the present disclosure. [Figure 13B] FIG. 13B is a schematic plan view showing an enlarged view of the first joint portion of the first modification example shown in FIG. 13A. [Figure 14A] FIG. 14A is a plan view showing a configuration example of a first joint portion between an upper end surface of an electrode winding body and a positive electrode current collector plate in a secondary battery as a second modification example of the present disclosure. [Figure 14B] FIG. 14B is a schematic plan view showing an enlarged view of the first joint portion of the second modification example shown in FIG. 14A. [Figure 15A] FIG. 15A is a plan view showing a configuration example of a first joint portion between an upper end surface of an electrode winding body and a positive electrode current collector plate in a secondary battery as a first example of a third modification example of the present disclosure. [Figure 15B] FIG. 15B is a plan view showing a configuration example of a first joint portion between an upper end surface of an electrode winding body and a positive electrode current collector plate in a secondary battery as a second example of a third modification example of the present disclosure. [Figure 16] FIG. 16 is a plan view showing a configuration example of a first joint portion between an upper end surface of an electrode winding body and a positive electrode current collector plate in a secondary battery as a fourth modification example of the present disclosure. [Figure 17] FIG. 17 is a plan view showing a configuration example of a first joint portion between an upper end surface of an electrode winding body and a positive electrode current collector plate in a secondary battery as a fifth modification example of the present disclosure. [Figure 18] Figure 18 is a plan view showing an example of the configuration of the first joint between the upper end face of the electrode winding and the positive electrode current collector plate in a secondary battery as a sixth modified example of the present disclosure. [Figure 19] Figure 19 is a plan view showing an example of the configuration of the first joint between the upper end face of the electrode winding and the positive electrode current collector plate in a secondary battery as a seventh modification of the present disclosure. [Figure 20] Figure 20 is a plan view showing an example of the configuration of the first joint between the upper end face of the electrode winding and the positive electrode current collector plate in a secondary battery as an eighth modified example of the present disclosure. [Figure 21] Figure 21 is a plan view showing an example of the configuration of the first joint between the upper end face of the electrode winding and the positive electrode current collector plate in a secondary battery as a ninth modified example of the present disclosure. [Figure 22] Figure 22 is a plan view showing an example of the configuration of the first joint between the upper end face of the electrode winding and the positive electrode current collector plate in a secondary battery as a tenth modified example of the present disclosure. [Figure 23] Figure 23 is a plan view showing the first joint between the upper end face of the electrode winding and the positive electrode current collector plate in a secondary battery as a first comparative example. [Figure 24A] Figure 24A is a plan view showing the first joint between the upper end face of the electrode winding and the positive electrode current collector plate in a secondary battery, which is a second comparative example. [Figure 24B] Figure 24B is a schematic plan view showing an enlarged view of the first joint shown in Figure 24A. [Modes for carrying out the invention]

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

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

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

[0014] The charging and discharging principle of a secondary battery is not particularly limited, but the following explanation will describe a case where the battery capacity is obtained by utilizing the intercalation and deintercalation of electrode reactants. This secondary battery includes an electrolyte along with a positive electrode and a negative electrode. In this secondary battery, in order to prevent the deposition of electrode reactants on the surface of the negative electrode during charging, the charging capacity of the negative electrode is greater than the discharge capacity of the positive electrode. That is, the electrochemical capacity per unit area of ​​the negative electrode is set to be greater than the electrochemical capacity per unit area of ​​the positive electrode.

[0015] As mentioned above, the types of electrode reactants are not particularly limited, but specifically, they are light metals such as alkali metals and alkaline earth metals. Alkali metals include lithium, sodium, and potassium, while alkaline earth metals include beryllium, magnesium, and calcium.

[0016] In the following example, we will consider the case where lithium is the electrode reactant. A secondary battery that obtains battery capacity by utilizing the intercalation and deintercalation of lithium is a so-called lithium-ion secondary battery. In this lithium-ion secondary battery, lithium is intercalated and deintercalated in an ionic state.

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

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

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

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

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

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

[0023] (Crimping structure 11R) At the open end 11N of the outer casing 11, a crimped structure 11R is formed, in which, for example, the battery cover 14 and the safety valve mechanism 30 are crimped together via a gasket 15. The battery cover 14 seals the outer casing 11 with the electrode winding 20 and the like housed inside. The crimped structure 11R has a bent portion 11P, which is a so-called crimped portion. Furthermore, a constricted portion 11S is provided between the bent portion 11P and the insulating plate 12, where a part of the outer casing 11 protrudes inward.

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

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

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

[0027] (Electrode winding body 20) The electrode winding 20 is positioned between the positive electrode current collector plate 24 and the negative electrode current collector plate 25. The electrode winding 20 has an upper end face 41 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 20 is a power generation element that carries out a charge-discharge reaction and is housed inside the outer casing 11. The electrode winding 20 includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte which is a liquid electrolyte. Here, the positive electrode 21 is a specific example corresponding to one aspect of the "first electrode" of this disclosure. The negative electrode 22 is a specific example corresponding to one aspect of the "second electrode" of this disclosure. The upper end face 41 is a specific example corresponding to one aspect of the "first end face" of this disclosure. Furthermore, the lower end face 42 is a specific example corresponding to one aspect of the "second end face" of this disclosure.

[0028] Figure 2 is an unfolded view of the electrode winding 20. In other words, Figure 2 schematically represents a part of the laminate S20 obtained by unfolding the electrode winding 20. The laminate S20 includes a positive electrode 21, a negative electrode 22, and a separator 23. In the laminate S20, the positive electrode 21 and the negative electrode 22 are laminated to each other via the separator 23. The separator 23 has, for example, two base materials, namely a first separator member 23A and a second separator member 23B. Therefore, the electrode winding 20 has a four-layer laminate S20 in which the positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are laminated in that order. The positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are all substantially strip-shaped members with the W direction as the short side and the L direction as the long side. Here, the positive electrode 21 is a specific example corresponding to one embodiment of the "first electrode" of this disclosure. The negative electrode 22 is a specific example corresponding to one embodiment of the "second electrode" of this disclosure.

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

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

[0031] Figure 4A is an unfolded view of the positive electrode 21, schematically representing its state before winding. Figure 4B shows the cross-sectional configuration of the positive electrode 21. Note that Figure 4B shows the cross-section in the direction of the arrow along the IVB-IVB line shown in Figure 4A. The positive electrode 21 includes, for example, a positive electrode current collector 21A, a positive electrode active material layer 21B that covers a part of the positive electrode current collector 21A, and an insulating layer 100. The positive electrode active material layer 21B and the insulating layer 100 may be provided on only one side of the positive electrode current collector 21A, or on both sides of the positive electrode current collector 21A. Figure 4B shows the case where the positive electrode active material layer 21B and the insulating layer 100 are provided on both sides of the positive electrode current collector 21A. More specifically, the positive electrode current collector 21A includes an inner circumferential surface 21A1 of the positive electrode current collector facing the winding center side of the electrode winding body 20, i.e., the central axis CL, and an outer circumferential surface 21A2 of the positive electrode current collector facing the opposite side of the winding center side of the electrode winding body 20, i.e., the side opposite to the inner circumferential surface 21A1. The positive electrode 21 has a positive electrode active material layer 21B, which includes an inner circumferential active material layer 21B1 covering at least a portion of the inner circumferential surface 21A1 of the positive electrode current collector, and an outer circumferential active material layer 21B2 covering at least a portion of the outer circumferential surface 21A2 of the positive electrode current collector. In this specification, the inner circumferential active material layer 21B1 and the outer circumferential active material layer 21B2 may be referred to collectively as the positive electrode active material layer 21B without distinction. The positive electrode active material layer 21B extends in both the L direction and the W direction perpendicular to the L direction. The L direction is the winding direction of the laminate S20. The W direction substantially coincides with the central axis CL. Here, the positive electrode current collector 21A is a specific example corresponding to one embodiment of the "first electrode current collector" of this disclosure. Furthermore, the positive electrode active material layer 21B is a specific example corresponding to one embodiment of the "first electrode active material layer" of this disclosure.

[0032] The positive electrode current collector 21A includes a positive electrode covering region 211 covered by the positive electrode active material layer 21B, and a positive electrode exposed region 212 that extends in the W direction without being covered by the positive electrode active material layer 21B. As shown in Figure 4A, the positive electrode covering region 211 and the positive electrode exposed region 212 each extend along the L direction, which is the longitudinal direction of the positive electrode 21, from the edge 21E1 on the winding center side of the positive electrode 21 to the edge 21E2 on the winding outer circumference side. Here, the L direction corresponds to the winding direction of the electrode winding body 20. That is, in the positive electrode 21, the positive electrode current collector 21A is covered by the positive electrode active material layer 21B from the edge 21E1 on the winding center side of the positive electrode 21 to the edge 21E2 on the winding outer circumference side of the positive electrode 21 in the winding direction of the electrode winding body 20. The positive electrode covering region 211 and the positive electrode exposed region 212 are adjacent to each other in the W direction, which is the short direction of the positive electrode 21. The W direction substantially coincides with the central axis CL. The positive electrode active material layer 21B extends in both the L direction, which is the long direction of the positive electrode 21, and the W direction, which is the width direction perpendicular to the L direction. Also, as shown in Figure 3, in the electrode winding body 20, the edge 21E1 on the winding center side of the innermost positive electrode portion 21in is set back inward from the edge 22E1 on the winding center side of the innermost negative electrode portion 22in. Furthermore, as shown in Figure 4A, the positive electrode 21 has a lower edge 21E3 that extends in the L direction on the lower side of the electrode winding body 20. Note that Figures 4A and 4B schematically show the positive electrode current collector 21A in a state that extends linearly along the W direction. However, in reality, the positive electrode edge 212E of the positive electrode exposed region 212 is bent toward the central axis CL, as shown in Figure 1, and is connected to the positive electrode current collector plate 24. That is, the end of the positive electrode exposed region 212 in the W direction constitutes the upper end face 41 and is connected to the positive electrode current collector plate 24 (see Figure 1). The upper end face 41 is formed by bending the positive electrode edge 212E of the positive electrode exposed region 212 toward, for example, the through hole 26 when it is wound. Note that the positive electrode edge 212E includes multiple adjacent parts in the radial direction (R direction) of the electrode winding body 20, and it is sufficient that at least a part of these multiple parts is bent toward the through hole 26.

[0033] An insulating layer 100 is preferably provided at the boundary between the positive electrode covering region 211 and the positive electrode exposed region 212, and in its vicinity. The insulating layer 100, like the positive electrode covering region 211 and the positive electrode exposed region 212, preferably extends from the edge 21E1 on the winding center side of the electrode winding body 20 to the edge 21E2 on the winding outer circumference side. Furthermore, the insulating layer 100 is preferably bonded to at least one of the first separator member 23A and the second separator member 23B. This is because it prevents misalignment between the positive electrode 21 and the separator 23. In addition, the insulating layer 100 preferably contains a resin containing polyvinylidene fluoride (PVDF). This is because the insulating layer 100 contains PVDF, which allows it to swell due to the solvent contained in the electrolyte, for example, and adhere well to the separator 23.

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

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

[0036] In the laminated electrode winding body 20, the positive electrode 21 and the negative electrode 22 are laminated with a separator 23 in between, such that the positive electrode exposed region 212 and the first portion 222A of the negative electrode exposed region 222 are oriented in opposite directions along the width direction, W. The ends of the separator 23 are fixed to the side portion 45 of the electrode winding body 20 by attaching fixing tape 46, thereby preventing loosening of the winding.

[0037] In secondary battery 1, as shown in Figure 2, when the width of the positive electrode exposed region 212 is A and the width of the first portion 222A of the negative electrode exposed region 222 is B, it is preferable that A > B. For example, when width A = 7 (mm), width B = 4 (mm). Also, when the width of the portion of the positive electrode exposed region 212 that protrudes from the outer edge in the width direction of the separator 23 is C, and the length of the portion of the first portion 222A of the negative electrode exposed region 222 that protrudes from the outer edge on the opposite side in the width direction of the separator 23 is D, it is preferable that C > D. For example, when width C = 4.5 (mm), width D = 3 (mm).

[0038] As shown in Figure 1, at the upper part of the secondary battery 1, multiple adjacent portions of the positive electrode edge 212E of the positive electrode exposed region 212 wound around the central axis CL are bent toward the central axis CL so as to overlap each other in the radial direction (R direction) of the electrode winding body 20, forming the upper end face 41 of the electrode winding body 20. Similarly, at the lower part of the secondary battery 1, multiple adjacent portions of the negative electrode edge 222E of the negative electrode exposed region 222 wound around the central axis CL are bent toward the central axis CL so as to overlap each other in the radial direction (R direction), forming the lower end face 42 of the electrode winding body 20. Therefore, multiple portions of the positive electrode edge 212E of the positive electrode exposed region 212 converge at the upper end face 41 of the electrode winding body 20, and multiple portions of the negative electrode edge 222E of the negative electrode exposed region 222 converge at the lower end face 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, multiple portions of the positive electrode edge portion 212E, which is bent toward the central axis CL, are flat surfaces. Similarly, to improve contact between the negative electrode current collector plate 25 for extracting current and the negative electrode edge portion 222E, multiple portions of the negative electrode edge portion 222E, which is bent toward the central axis CL, are flat surfaces. Note that the term "flat surface" here includes not only perfectly flat surfaces but also surfaces with some irregularities or surface roughness to the extent that the positive electrode exposed region 212 and the negative electrode exposed region 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 will be described later. On the other hand, the negative electrode current collector 22A is made of, for example, copper foil, as will be described later. In this case, the positive electrode current collector 21A is softer than the negative electrode current collector 22A. That is, the Young's modulus of the positive electrode exposed region 212 is lower than that of the negative electrode exposed region 222. For this reason, in one embodiment, it is more preferable that the widths A to D have the relationship A > B and C > D. In that case, when the positive electrode exposed region 212 and the negative electrode exposed region 222 are bent simultaneously from both electrode sides with the same pressure, the height measured from the tip of the separator 23 of the bent portion may be about the same for the positive electrode 21 and the negative electrode 22. At this time, multiple parts of the positive electrode edge 212E (Figure 1) are bent and overlap appropriately. Therefore, the joining of the positive electrode exposed region 212 and the positive electrode current collector plate 24 can be easily performed. Similarly, multiple portions of the negative electrode edge 222E (Figure 1) are bent and overlap appropriately. This facilitates joining the negative electrode exposed region 222 to the negative electrode current collector plate 25. Joining here means, for example, being joined by laser welding, but the joining method is not limited to laser welding.

[0040] As shown in Figure 2, the portion of the positive electrode exposed region 212 of the positive electrode 21 that faces the negative electrode 22 across the separator 23 is covered by the insulating layer 100. The insulating layer 100 has a width of, for example, 3 mm in the W-axis direction. The insulating layer 100 covers the entire area of ​​the positive electrode exposed region 212 of the positive electrode 21 that faces the negative electrode covered region 221 of the negative electrode 22 via the separator 23. The insulating layer 100 can effectively prevent internal short circuits in the secondary battery 1 when, for example, foreign matter enters between the negative electrode covered region 221 and the positive electrode exposed region 212. Furthermore, when the secondary battery 1 is subjected to an impact, the insulating layer 100 can absorb the impact and effectively prevent bending of the positive electrode exposed region 212 and short circuits between the positive electrode exposed region 212 and the negative electrode 22.

[0041] (Positive electrode current collector 21A) The positive electrode current collector 21A contains a conductive material such as aluminum. The positive electrode current collector 21A is, for example, a metal foil made of aluminum or an aluminum alloy.

[0042] (Positive electrode active material layer 21B) The positive electrode active material layer 21B contains one or more positive electrode materials capable of intercalating and deintercalating lithium as the positive electrode active material. However, the positive electrode active material layer 21B may further contain one or more other materials such as a positive electrode binder and a positive electrode conductive agent. The positive electrode material is preferably a lithium-containing compound, and more specifically, preferably a lithium-containing composite oxide and a lithium-containing phosphate compound. A lithium-containing composite oxide is an oxide that contains lithium and one or more other elements, i.e., elements other than lithium, as constituent elements. A lithium-containing composite oxide has a crystal structure such as layered rock salt type and spinel type. A lithium-containing phosphate compound is a phosphate compound that contains lithium and one or more other elements as constituent elements, and has a crystal structure such as olivine type. In particular, the positive electrode active material layer 21B may contain at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide as the positive electrode active material. The positive electrode binder contains one or more of the following: synthetic rubber and polymer compounds. Examples of synthetic rubber include styrene-butadiene rubber, fluororubber, and ethylene-propylenediene. Examples of polymer compounds include polyvinylidene fluoride and polyimide. The positive electrode conductive agent contains one or more of the following: carbon materials. Examples of carbon materials include graphite, carbon black, acetylene black, and Ketjen black. However, the positive electrode conductive agent may also be a metal material or a conductive polymer, as long as it is a conductive material.

[0043] (Negative electrode current collector 22A) The negative electrode current collector 22A contains a conductive material such as copper. The negative electrode current collector 22A is a metal foil made of, for example, nickel, a nickel alloy, copper, or a copper alloy. It is preferable that the surface of the negative electrode current collector 22A is roughened. This is because the adhesion of the negative electrode active material layer 22B to the negative electrode current collector 22A is improved by the so-called anchoring effect. In this case, it is sufficient that the surface of the negative electrode current collector 22A is roughened in at least the region facing the negative electrode active material layer 22B. A method of roughening the surface is, for example, a method of forming fine particles using electrolytic treatment. In electrolytic treatment, fine particles are formed on the surface of the negative electrode current collector 22A by electrolysis in an electrolytic cell, so that the surface of the negative electrode current collector 22A has irregularities. Copper foil produced by electrolysis is generally called electrolytic copper foil.

[0044] (Negative electrode active material layer 22B) The negative electrode active material layer 22B contains one or more negative electrode materials capable of intercalating and releasing lithium as the negative electrode active material. However, the negative electrode active material layer 22B may further contain one or more other materials such as a negative electrode binder and a negative electrode conductive agent. The negative electrode material is, for example, a carbon material. This is because a high energy density can be stably obtained because the change in crystal structure during intercalation and release of lithium is very small. In addition, since the carbon material also functions as a negative electrode conductive agent, the conductivity of the negative electrode active material layer 22B is improved. Examples of carbon materials include easily graphitizable carbon, poorly graphitizable carbon, and graphite. However, the interplanar spacing of the (002) planes in poorly graphitizable carbon is preferably 0.37 nm or more. The interplanar spacing of the (002) planes in graphite is preferably 0.34 nm or less. More specifically, carbon materials include, for example, pyrolysis carbons, cokes, glassy carbon fibers, calcined organic polymer compounds, activated carbon, and carbon blacks. These cokes include pitch coke, needle coke, and petroleum coke. Calcined organic polymer compounds are obtained by calcining (carbonizing) polymer compounds such as phenolic resins and furan resins at an appropriate temperature. In addition, the carbon material may be low-crystalline carbon heat-treated at a temperature of approximately 1000°C or lower, or amorphous carbon. The carbon material may take the form of fibers, spheres, granules, or flakes. In secondary battery 1, when the open-circuit voltage at full charge, i.e., the battery voltage, is 4.25V or higher, the amount of lithium released per unit mass increases compared to when the open-circuit voltage at full charge is 4.20V, even when using the same positive electrode active material. Therefore, the amounts of positive electrode active material and negative electrode active material are adjusted accordingly. This results in a high energy density.

[0045] Further, the negative electrode active material layer 22B may contain, as a negative electrode active material, a silicon-containing material containing at least one of silicon, silicon oxide, carbon-silicon compound, and silicon alloy. The silicon-containing material is a general term for materials containing silicon as a constituent element. However, the silicon-containing material may contain only silicon as a constituent element. Note that the type of the silicon-containing material may be only one type or two or more types. The silicon-containing material can form an alloy with lithium, and may be a single substance of silicon, an alloy of silicon, a compound of silicon, a mixture of two or more of them, or a material containing one or two or more phases of them. Also, the silicon-containing material may be crystalline, amorphous, or may contain both a crystalline part and an amorphous part. However, since the single substance described here means only a general single substance, it may contain a trace amount of impurities. That is, the purity of the single substance is not necessarily limited to 100%. The alloy of silicon contains, for example, any one or two or more of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium as constituent elements other than silicon. The compound of silicon contains, for example, any one or two or more of carbon and oxygen as constituent elements other than silicon. Note that the compound of silicon may contain any one or two or more of the series of constituent elements described for the alloy of silicon as constituent elements other than silicon. Specifically, the alloy of silicon and the compound of silicon are, for example, SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, and SiO v (0 < v ≤ 2) and the like. However, the range of v can be arbitrarily set, and for example, 0.2 < v < 1.4 may also be acceptable.

[0046] Figure 6A is a schematic plan view showing the upper end face 41 of the electrode winding body 20 as viewed from the positive electrode current collector plate 24. The upper end face 41 is formed when the positive electrode edge portion 212E in the W direction of the positive electrode exposed region 212 is bent toward the through hole 26 when the laminate S20 is wound. As shown in Figure 6A, the upper end face 41 is provided with one or more grooves 41G and protrusions 41T. The one or more grooves 41G extend from the outer edge 20PE of the electrode winding body 20 toward the inner edge 20IE of the electrode winding body 20. The protrusions 41T are portions that protrude toward the positive electrode current collector plate 24 more than the one or more grooves 41G. Here, the grooves 41G may be continuous from the outer edge 20PE to the inner edge 20IE, or they may be interrupted in the middle. Furthermore, there are multiple grooves 41G, and it is desirable that the lengths of these multiple grooves 41G are substantially equal to each other. Furthermore, it is preferable that the multiple 41Gs have the same shape, for example, the same planar shape or the same cross-sectional shape. Figure 6A illustrates a case where the upper end face 41 includes eight grooves 41G and eight protrusions 41T. The number of grooves 41G is preferably between 3 and 16. The eight grooves 41G extend radially from the through hole 26. The protrusions 41T are the parts of the upper end face 41 excluding the grooves 41G. The protrusions 41T of the upper end face 41 are joined to the positive electrode current collector plate 24.

[0047] Figure 6B is a schematic plan view showing the lower end face 42 of the electrode winding body 20 as viewed from the negative electrode current collector plate 25. The lower end face 42 is formed when the negative electrode edge portion 222E in the W direction of the negative electrode exposed region 222 bends toward the through hole 26 when the laminate S20 is wound. As shown in Figure 6B, the lower end face 42 is provided with one or more grooves 42G and protrusions 42T. The one or more grooves 42G extend from the outer edge 20PE of the electrode winding body 20 toward the inner edge 20IE of the electrode winding body 20. The protrusions 42T are portions that protrude toward the negative electrode current collector plate 25 more than the one or more grooves 42G. Here, the grooves 42G may be continuous from the outer edge 20PE to the inner edge 20IE, or they may be interrupted in the middle. Furthermore, there are multiple grooves 42G, and it is desirable that the lengths of these multiple grooves 42G are substantially equal to each other. Furthermore, the multiple grooves 42G may have the same shape as each other, for example, that is, the same planar shape or the same cross-sectional shape. Figure 6B illustrates a case where the lower end face 42 includes eight grooves 42G and eight protrusions 42T. The number of grooves 42G is preferably between 3 and 16. The eight grooves 42G extend radially from the through hole 26. The protrusions 42T are the parts of the lower end face 42 excluding the grooves 42G. The protrusions 42T of the lower end face 42 are joined to the negative electrode current collector plate 25.

[0048] (Insulating tape 53, 54) The secondary battery 1 may further have insulating tapes 53, 54 in the gap between the outer casing 11 and the electrode winding 20. The positive electrode exposed region 212 and the negative electrode exposed region 222, which are concentrated at the upper end face 41 and the lower end face 42, are conductors such as exposed metal foil. Therefore, if the positive electrode exposed region 212 and the negative electrode exposed region 222 are in close proximity to the outer casing 11, a short circuit may occur between the positive electrode 21 and the negative electrode 22 via the outer casing 11. Also, a short circuit may occur when the positive electrode current collector plate 24 facing the upper end face 41 is in close proximity to the outer casing 11. For this reason, it is preferable to provide insulating tapes 53, 54 as insulating members. The insulating tapes 53, 54 are, for example, adhesive tapes in which the base material layer is made of one of polypropylene, polyethylene terephthalate, or polyimide, and the base material layer has an adhesive layer on one side of the base material layer. In order to avoid reducing the volume of the electrode winding body 20 by installing the insulating tapes 53 and 54, the insulating tapes 53 and 54 are positioned so as not to overlap with the fixing tape 46 attached to the side portion 45, and the thickness of the insulating tapes 53 and 54 is set to be less than or equal to the thickness of the fixing tape 46.

[0049] (Positive electrode current collector plate 24 and negative electrode current collector plate 25) In typical lithium-ion secondary batteries, for example, one lead for current extraction is welded to each of the positive and negative electrodes. However, this results in high internal resistance of the lithium-ion secondary battery, causing it to overheat and become hot during discharge, making it unsuitable for high-rate discharge. Therefore, in the secondary battery 1 of this embodiment, the positive electrode current collector plate 24 is positioned facing the upper end face 41, and the negative electrode current collector plate 25 is positioned facing the lower end face 42. The positive electrode exposed area 212 on the upper end face 41 and the positive electrode current collector plate 24 are welded at multiple points, and the negative electrode exposed area 222 on the lower end face 42 and the negative electrode current collector plate 25 are welded at multiple points. This reduces the internal resistance of the secondary battery 1. The fact that the upper end face 41 and the lower end face 42 are flat surfaces, as described above, also contributes to the reduction in resistance. The positive electrode current collector plate 24 is provided between the battery cover 14 and the upper end face 41. The positive electrode current collector plate 24 is electrically connected to the battery cover 14, for example, via a safety valve mechanism 30. The negative electrode current collector plate 25 is provided between the bottom 11B and the lower end face 42 of the outer casing 11. The negative electrode current collector plate 25 is electrically connected to the inner surface of the bottom 11B of the outer casing 11, for example. Figure 7A is an exploded view showing one example configuration of the positive electrode current collector plate 24. Figure 7B is an exploded view showing one example configuration of the negative electrode current collector plate 25. The positive electrode current collector plate 24 is a metal plate made of, for example, a single material of aluminum or an aluminum alloy, or a composite material thereof. The negative electrode current collector plate 25 is a metal plate made of, for example, a single material of nickel, a nickel alloy, copper, or a copper alloy, or a composite material of two or more of these.

[0050] As shown in Figure 7A, the positive electrode current collector plate 24 has a substantially fan-shaped portion 31 and a substantially rectangular strip portion 32. However, the shape of the positive electrode current collector plate 24 is not limited to the shape shown in Figure 7A and can be arbitrarily selected. In the secondary battery 1, the positive electrode current collector plate 24 is housed in the outer casing 11 with the strip portion 32 folded relative to the fan-shaped portion 31, as shown in Figure 1. Figure 7A shows the positive electrode current collector plate 24 in an unfolded state. The fan-shaped portion 31 is an opposing portion that is connected to and opposite the convex portion 41T of the upper end face 41. The fan-shaped portion 31 has an outer edge that includes, for example, a straight portion and a curved portion. An opening 35 is formed near the center of the fan-shaped portion 31. Figure 7A illustrates the case where the opening 35 has a circular planar shape in a horizontal plane perpendicular to the Z-axis direction. The strip portion 32 is connected to, for example, the straight portion of the outer edge of the fan-shaped portion 31. The strip portion 32 extends in a direction intersecting the straight portion of the fan-shaped portion 31. As shown in Figure 1, in the secondary battery 1, the positive electrode current collector plate 24 is provided such that the opening 35 overlaps with the through hole 26 in the Z-axis direction. That is, the opening 35 is provided in a position that overlaps with a part of the upper end face 41 on the winding center side in the Z-axis direction.

[0051] The shaded area in Figure 7A is the insulating portion 32A of the strip-shaped portion 32. The insulating portion 32A is a part of the strip-shaped portion 32 to which insulating tape is attached or insulating material is applied. The lower part of the strip-shaped portion 32 below the insulating portion 32A is the connection portion 32B to the sealing plate which also serves as an external terminal. The sealing plate is electrically connected to the battery cover 14. Note that, as shown in Figure 1, if the secondary battery 1 has a battery structure in which there is no metal center pin in the through hole 26, the possibility of the strip-shaped portion 32 coming into contact with the negative electrode potential is low. Therefore, the positive electrode current collector plate 24 does not need to have an insulating portion 32A. If the positive electrode current collector plate 24 does not have an insulating portion 32A, the charge and discharge capacity can be increased by widening the width between the positive electrode 21 and the negative electrode 22 by an amount equivalent to the thickness of the insulating portion 32A.

[0052] The shape of the negative electrode current collector plate 25 shown in Figure 7B is almost the same as the shape of the positive electrode current collector plate 24 shown in Figure 7A. The negative electrode current collector plate 25 has a roughly fan-shaped portion 33 and a roughly rectangular strip portion 34. However, the shape of the negative electrode current collector plate 25 is not limited to the shape shown in Figure 6B and can be arbitrarily selected. In the secondary battery 1, the negative electrode current collector plate 25 is housed in the outer casing 11 with the strip portion 34 bent relative to the fan-shaped portion 33, as shown in Figure 1. Figure 7B shows the negative electrode current collector plate 25 in an unfolded state. The fan-shaped portion 33 is an opposing portion that is connected opposite to the convex portion 42T of the lower end face 42. The fan-shaped portion 33 has an outer edge that includes, for example, a straight portion and a curved portion. The strip portion 34 is connected, for example, to the straight portion of the outer edge of the fan-shaped portion 33. The strip portion 34 extends in a direction intersecting the straight portion of the fan-shaped portion 33. The strip portion 34 of the negative electrode current collector plate 25 is shorter than the strip portion 32 of the positive electrode current collector plate 24 and does not have a portion corresponding to the insulating portion 32A of the positive electrode current collector plate 24. Multiple circular protrusions 37, indicated by circles, are provided on the strip portion 34. At least some of the multiple protrusions 37 are welded to the bottom portion 11B of the outer casing 11. During resistance welding, the current concentrates on the protrusions 37, causing them to melt and welding the strip portion 34 to the bottom portion 11B of the outer casing 11. Similar to the positive electrode current collector plate 24, the negative electrode current collector plate 25 has an opening 36 formed near the center of the fan-shaped portion 33. In the secondary battery 1, the negative electrode current collector plate 25 is provided such that the opening 36 overlaps with the through hole 26 in the Z-axis direction. Figure 7B illustrates the case where the opening 36 has a circular planar shape in a horizontal plane perpendicular to the Z-axis direction.

[0053] The fan-shaped portion 31 of the positive electrode current collector plate 24 covers only a portion of the upper end face 41 due to its planar shape. Similarly, the fan-shaped portion 33 of the negative electrode current collector plate 25 covers only a portion of the lower end face 42 due to its planar shape. There are two reasons, for example, why the fan-shaped portions 31 and 33 do not cover the entire upper end face 41 and lower end face 42. The first reason is to allow the electrolyte to penetrate smoothly into the electrode winding body 20 when assembling the secondary battery 1. In particular, in the secondary battery 1 of this embodiment, the positive electrode current collector plate 24 is positioned such that the opening 35 overlaps with a portion of the upper end face 41 on the winding center side in the Z-axis direction. As a result, a portion of the positive electrode edge 212E that constitutes the upper end face 41 is exposed to the opening 35 without being covered by the fan-shaped portion 31 of the positive electrode current collector plate 24. Therefore, the secondary battery 1 has a structure that allows the electrolyte to penetrate into the electrode winding body 20 more quickly. The second reason is to facilitate the release of gases generated when lithium-ion rechargeable batteries experience abnormally high temperatures or overcharge conditions.

[0054] (Separator 23) The separator 23 is interposed between the positive electrode 21 and the negative electrode 22. The separator 23 allows lithium ions to pass through while preventing short circuits of current caused by contact between the positive electrode 21 and the negative electrode 22. The separator 23 is made of one or more of the following porous films: synthetic resin and ceramic, for example, or a laminated film of two or more porous films. Examples of synthetic resins include polytetrafluoroethylene, polypropylene, and polyethylene. However, the separator 23 preferably has a substrate made of a single-layer polyolefin porous film containing polyethylene, because it provides better high-power characteristics compared to a laminated film. When the first separator member 23A and the second separator member 23B constituting the separator 23 are each single-layer porous films made of polyolefin, the thickness of the porous film should preferably be, for example, 10 μm or more and 15 μm or less. Having a single-layer porous film made of polyolefin with a thickness of 10 μm or more allows for sufficient avoidance of internal short circuits. Better discharge capacity characteristics can be obtained if the thickness of the single-layer porous film made of polyolefin is 15 μm or less. Furthermore, the surface density of the porous film is, for example, 6.3 g / m². 2 More than 8.3g / m 2 The following conditions are preferable: The surface density of a single-layer porous film made of polyolefin is 6.3 g / m². 2 If the above conditions are met, internal short circuits can be sufficiently avoided. The surface density of the single-layer porous film made of polyolefin is 8.3 g / m². 2 The following conditions will result in better discharge capacity characteristics.

[0055] In particular, the separator 23 may include, for example, a porous membrane as the substrate as described above, and a polymer compound layer provided on one or both sides of the substrate. This is because the adhesion of the separator 23 to the positive electrode 21 and the negative electrode 22 is improved, thereby suppressing distortion of the electrode winding 20. As a result, the decomposition reaction of the electrolyte is suppressed, and leakage of the electrolyte impregnated into the substrate layer is also suppressed, so that the resistance does not increase easily even after repeated charging and discharging, and battery swelling is suppressed. The polymer compound layer includes, for example, a polymer compound such as polyvinylidene fluoride. This is because it has excellent physical strength and is electrochemically stable. However, the polymer compound may be something other than polyvinylidene fluoride. When forming this polymer compound layer, for example, a solution in which the polymer compound is dissolved in an organic solvent is applied to the substrate layer, and then the substrate layer is dried. Alternatively, the substrate layer may be immersed in the solution and then dried. This polymer compound layer may contain one or more types of insulating particles, such as inorganic particles. Examples of inorganic particles include aluminum oxide and aluminum nitride.

[0056] (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 includes, for example, at least one of fluorinated ethylene carbonate, trifluorocarbonate, trifluoroethyl methyl carbonate, fluorinated carboxylic acid ester, and fluorine ether. The non-aqueous solvent may further contain at least one nitrile compound other than a dinitrile compound, such as a mononitrile compound or a trityl compound. As the dinitrile compound, succinonitrile (SN) is preferred, for example. However, the dinitrile compound is not limited to succinonitrile, and may be other dinitrile compounds such as adiponitrile.

[0057] The electrolyte salt contains one or more types of salts, such as lithium salts. However, the electrolyte salt may also contain salts other than lithium salts. These salts other than lithium salts are, for example, salts of light metals other than lithium. Examples of lithium salts include lithium hexafluoride phosphate (LiPF6), lithium tetraborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoride arsenate (LiAsF6), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), dilithium hexafluorosilicate (Li2SiF6), lithium chloride (LiCl), and lithium bromide (LiBr). In particular, one or more of lithium hexafluoride phosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoride arsenate are preferred, with lithium hexafluoride phosphate being more preferred. The content of the electrolyte salt is not particularly limited, but is preferably 0.3 mol / kg to 3 mol / kg relative to the solvent. When the electrolyte contains LiPF6 as the electrolyte salt, the concentration of LiPF6 in the electrolyte should be 1.25 mol / kg or more and 1.45 mol / kg or less. This is because it prevents cycle degradation due to salt consumption (decomposition) during high-load rate charging, thereby improving high-load cycle characteristics. When the electrolyte further contains LiBF4 in addition to LiPF6 as the electrolyte salt, the concentration of LiBF4 in the electrolyte should be 0.001% by weight or more and 0.1% by weight or less. This is because it more effectively prevents cycle degradation due to salt consumption (decomposition) during high-load rate charging, thereby further improving high-load cycle characteristics.

[0058] (First joint 61 and second joint 62) Figure 8A shows an example of the configuration of the first joint portion 61 between the upper end face 41 of the electrode winding body 20 and the positive electrode current collector plate 24 in a plane perpendicular to the central axis CL of the electrode winding body 20. As shown in Figure 8A, the fan-shaped portion 31 and the upper end face 41 of the positive electrode current collector plate 24 are joined to each other by one or more first joint portions 61. The fan-shaped portion 31 and the upper end face 41 are joined, for example, by welding. As a welding method, laser welding can be used, which fuses the contact portion between the fan-shaped portion 31 and the upper end face 41 by scanning and irradiating the contact portion with a laser. In the configuration example shown in Figure 8A, one first joint portion 61 is formed on each of the six protrusions 41T among the eight protrusions 41T separated by eight grooves 41G. The six first joint portions 61 are the portions where a part of each of the six protrusions 41T and a part of the fan-shaped portion 31 of the positive electrode current collector plate 24 are joined. Each of the six first joints 61 extends linearly in a meandering manner. Specifically, the six first joints 61 extend from the central axis CL, which is the winding center of the electrode winding body 20, toward the outer edge 20PE of the electrode winding body 20, while alternately bending to the left and right along the winding direction of the electrode winding body 20. The six first joints 61 are spaced apart and do not intersect with each other. However, parts of adjacent first joints 61 may be in contact with each other. The six first joints 61 are adjacent to each other, for example, in the radial direction of the electrode winding body 20, facing each other. The six first joints 61 extend, for example, in a direction perpendicular to the radial direction of the electrode winding body 20.

[0059] Figure 8B shows an example of the configuration of the second joint 62 between the lower end face 42 of the electrode winding 20 and the negative electrode current collector plate 25 in a plane perpendicular to the central axis CL of the electrode winding 20. As shown in Figure 8B, the fan-shaped portion 33 and the lower end face 42 of the negative electrode current collector plate 25 are joined to each other by one or more second joints 62. The fan-shaped portion 33 and the lower end face 42 are joined, for example, by welding. In the configuration example shown in Figure 8B, one second joint 62 is formed on each of the six protrusions 42T, which are separated by eight grooves 42G. The six second joints 62 are the portions where a part of each of the six protrusions 42T is joined to a part of the fan-shaped portion 33 of the negative electrode current collector plate 25. The six second joints 62 all extend linearly in a meandering manner. Specifically, the six second joints 62 extend from the central axis CL, which is the winding center of the electrode winding body 20, toward the outer edge 20PE of the electrode winding body 20, bending alternately to the left and right along the winding direction of the electrode winding body 20. The six second joints 62 are spaced apart from each other and do not intersect. The six second joints 62 are adjacent to each other, for example, in the radial direction of the electrode winding body 20, facing each other. The six second joints 62 extend, for example, in a direction perpendicular to the radial direction of the electrode winding body 20.

[0060] In the configuration examples shown in Figures 8A and 8B, six first joints 61 and six second joints 62 are provided, but this disclosure is not limited thereto. For example, the number of first joints 61 and second joints 62 can be one or more. However, it is preferable that the number of first joints 61 and second joints 62 be three or more, and particularly preferably four to six.

[0061] Figure 9A is a schematic plan view showing an enlarged view of the first joint 61. As shown in Figure 9A, each of the multiple first joints 61 has a meander-shaped planar form in a plane perpendicular to the through hole 26. Each of the multiple first joints 61 includes multiple first linear portions 61A and multiple first folded portions 61B. The multiple first linear portions 61A extend along the winding direction (θ direction) of the electrode winding body 20, that is, in a direction perpendicular to the radial direction (R direction) of the electrode winding body 20, and are discretely arranged adjacent to each other in the radial direction (R direction) of the electrode winding body 20. The multiple first folded portions 61B are curved portions that are bent to connect the multiple first linear portions 61A. In Figure 9A, seven first linear portions 61A1 to 61A7 are shown as examples of multiple first linear portions 61A, and six first folded portions 61B1 to 61B6 are shown as examples of multiple first folded portions 61B. However, the number of multiple first linear portions 61A is not limited to a specific number as long as it is two or more, and the number of multiple first folded portions 61B is not limited to a specific number as long as it is three or more. It is preferable that the multiple first linear portions 61A and the multiple first folded portions 61B have a certain width 61W.

[0062] In each of the multiple first joints 61, when the number of multiple first folded portions 61B is n (where n is a natural number), the length 61La of the electrode winding body 20 in the winding direction (θ direction) from the a-th (where a is a natural number between 2 and n) first folded portion 61Ba to the a+1th first folded portion 61B(a+1) of the multiple first folded portions 61B of the first joint 61 is longer than the length 61L1 of the electrode winding body 20 in the winding direction (θ direction) from the first first folded portion 61B1 to the second first folded portion 61B2 counting from the winding center of the electrode winding body 20 among the multiple first folded portions 61B of the first joint 61. Specifically, each of the lengths 61L2 to 61L4 shown in Figure 9A is longer than the length 61L1.

[0063] In particular, in the example configuration of the first joint 61 shown in Figure 9A, the length 61L(a+1) of the length 61L of the length 61L of the length 61L of the length 61L of the length 61L of the length 61L of the length 61L of the length 61L of the length 61L of the length 61B(a+1) of the length 61B(a+1) of the length 61B(a+1) of the length 61B(a+1) of the length 61B(a+1) of the length 61L of the length 61L of the length 61L of the length 61B(a+1) of the length 61L of the length 61L of the length 61B(a+1) of the length 61B(a+1) of the length 61B(a+1) of the length 61B(a- Specifically, in the example configuration of the first joint 61 shown in Figure 9A, length 61L2 is longer than length 61L1 (61L1 < 61L2), length 61L3 is longer than length 61L2 (61L2 < 61L3), and length 61L4 is longer than length 61L3 (61L3 < 61L4). In other words, in the example configuration of the first joint 61 shown in Figure 9A, the dimensions of the first joint 61 in the winding direction (θ direction) gradually increase from the winding center side toward the winding outer circumference side.

[0064] Furthermore, in the example configuration of the first joint 61 shown in Figure 9A, the ratio of length L(a+1) to length La, L(a+1) / La, is substantially equal to the ratio of length L(a+2) / L(a+1) to length L(a+1) in the winding direction (θ direction) from the (a+1)th first folded portion 61B(a+1) to the (a+2)th first folded portion 61B(a+2) counting from the winding center. Specifically, the ratio of length 61L2 to length 61L1 (61L2) / (61L1) is substantially equal to the ratio of length 61L3 to length 61L2 (61L3) / (61L2), and the ratio (61L3) / (61L2) is substantially equal to the ratio of length 61L4 to length 61L3 (61L4) / (61L3). That is, {(61L2 / 61L1)}≒{(61L3 / 61L2)}≒{(61L4 / 61L3)} That's how it is.

[0065] Figure 9B is a cross-sectional view showing the first joint portion 61 and its vicinity, which is the joint portion between the fan-shaped portion 31 of the positive electrode current collector plate 24 and the positive electrode edge portion 212E of the positive electrode current collector 21A. As shown in Figure 9B, it is preferable that the radial (R-direction) intervals 61D1 to 61D6 of the multiple first linear portions 61A are shorter than the radial (R-direction) lengths 41D1 to 41D5 of the portions 212E1 to 212E5 that form the upper end face 41 of the positive electrode edge portion 212E. With such a configuration, each of the multiple winding portions of the electrode winding body 20 wound around the central axis CL is joined to the fan-shaped portion 31 of the positive electrode current collector plate 24. In other words, the positive electrode edge portion 212E of the positive electrode current collector 21A and the fan-shaped portion 31 of the positive electrode current collector plate 24 are joined at more points, resulting in better extraction of current from the electrode winding body 20.

[0066] The second joint 62 may have substantially the same configuration as the first joint 61. Figure 10A is a schematic plan view showing an enlarged view of the second joint 62. As shown in Figure 10A, each of the multiple second joints 62 has a meander-shaped planar form in a plane perpendicular to the through hole 26. Each of the multiple second joints 62 includes multiple second linear portions 62A and multiple second folded portions 62B. The multiple second linear portions 62A extend along the winding direction (θ direction) of the electrode winding body 20 and are discretely arranged adjacent to each other in the radial direction (R direction) of the electrode winding body 20. The multiple second folded portions 62B are curved portions that bend to connect the multiple second linear portions 62A. In Figure 10A, seven second linear portions 62A1 to 62A7 are shown as examples of multiple second linear portions 62A, and six second folded portions 62B1 to 62B6 are shown as examples of multiple second folded portions 62B. However, the number of multiple second linear portions 62A is not limited to a specific number as long as it is two or more, and the number of multiple second folded portions 62B is not limited to a specific number as long as it is three or more. It is preferable that the multiple second linear portions 62A and the multiple second folded portions 62B have a certain width 62W.

[0067] In each of the multiple second junctions 62, when the number of multiple second folded portions 62B is m (where m is a natural number), the length 62Lb of

[0068] In particular, in the example configuration of the second joint 62 shown in Figure 10A, the length 61Lb in the winding direction (θ direction) of the electrode winding body 20 from the (b+1)th second folded portion 62B(b-1) (where b is a natural number between 2 and (m-1)) counted from the winding center of the electrode winding body 20 to the bth second folded portion 62Bb (counted from the winding center of the electrode winding body 20) is longer than the length 61Lb in the winding direction (θ direction) of the electrode winding body 20 from the bth second folded portion 62Bb to the (b+1)th second folded portion 62B(b+1) counted from the winding center of the electrode winding body 20. Specifically, in the example configuration of the second joint 62 shown in Figure 10A, length 62L2 is longer than length 62L1 (62L1 < 62L2), length 62L3 is longer than length 62L2 (62L2 < 62L3), and length 62L4 is longer than length 62L3 (62L3 < 62L4). In other words, in the example configuration of the second joint 62 shown in Figure 10A, the dimensions of the second joint 62 in the winding direction (θ direction) gradually increase from the winding center side toward the winding outer circumference side.

[0069] Furthermore, in the example configuration of the second joint 62 shown in Figure 10A, the ratio of length L(b+1) to length Lb, L(b+1) / Lb, is substantially equal to the ratio of length L(b+2) to length L(b+1) in the winding direction (θ direction) from the (b+1)th second folded portion 62B(b+1) to the (b+2)th second folded portion 62B(b+2) counting from the winding center, L(b+2) / L(b+1). Specifically, the ratio of length 62L2 to length 62L1 (62L2) / (62L1) is substantially equal to the ratio of length 62L3 to length 62L2 (62L3) / (62L2), and the ratio (62L3) / (62L2) is substantially equal to the ratio of length 62L4 to length 62L3 (62L4) / (62L3). That is, {(62L2 / 62L1)}≒{(62L3 / 62L2)}≒{(62L4 / 62L3)} That's how it is.

[0070] Figure 10B is a cross-sectional view showing the second joint portion 62 and its vicinity, which is the joint portion between the fan-shaped portion 33 of the negative electrode current collector plate 25 and the negative electrode edge portion 222E of the negative electrode current collector 22A. As shown in Figure 10B, it is preferable that each of the radial (R-direction) intervals 62D1 to 62D6 of the multiple second linear portions 62A is shorter than each of the radial (R-direction) lengths 42D1 to 42D5 of the portions 222E1 to 222E5 that form the lower end face 42 of the negative electrode edge portion 222E. With such a configuration, each of the multiple winding portions of the electrode winding body 20 wound around the central axis CL is joined to the fan-shaped portion 33 of the negative electrode current collector plate 25. In other words, the negative electrode edge portion 222E of the negative electrode current collector 22A and the fan-shaped portion 33 of the negative electrode current collector plate 25 are joined at more locations, resulting in better extraction of current from the electrode winding body 20.

[0071] [1-2. Operation] In the secondary battery 1 of this embodiment, for example, during charging, lithium ions are released from the positive electrode 21 and absorbed into the negative electrode 22 via the electrolyte. Also, in the secondary battery 1, for example, during discharge, lithium ions are released from the negative electrode 22 and absorbed into the positive electrode 21 via the electrolyte.

[0072] [1-3. Manufacturing method] The manufacturing method of the secondary battery 1 will be explained with reference to Figures 1 to 10B, as well as Figure 11. Figure 11 is a perspective view illustrating the manufacturing process of the secondary battery 1 shown in Figure 1.

[0073] First, a positive electrode current collector 21A is prepared, and a positive electrode active material layer 21B is selectively formed on the surface of the positive electrode current collector 21A. Then, an insulating layer 100 is formed on the surface of the positive electrode current collector 21A along the edge of the positive electrode active material layer 21B. A positive electrode 21 is obtained by the above operation. Next, a negative electrode current collector 22A is prepared, and a negative electrode active material layer 22B is selectively formed on the surface of the negative electrode current collector 22A to form a negative electrode 22 having a negative electrode covering region 221 and a negative electrode exposed region 222. The positive electrode 21 and the negative electrode 22 may be subjected to a drying treatment. Subsequently, a laminate S20 is manufactured by stacking the positive electrode 21 and the negative electrode 22 via a first separator member 23A and a second separator member 23B such that the positive electrode exposed region 212 and the first portion 222A of the negative electrode exposed region 222 are on opposite sides of each other in the W direction. Next, the laminate S20 is wound in a spiral shape so that through holes 26 are formed. At this time, for example, a cylindrical winding core is used as a jig, and the laminate S20 is wound around the cylindrical winding core. Furthermore, after attaching fixing tape 46 to the outermost circumference of the spirally wound laminate S20, the winding core is removed. This gives the electrode winding body 20 as shown in Figure 11(A).

[0074] Next, for example, the tip of a plate-shaped member having a wedge-shaped cross-section is pressed perpendicularly to the upper end face 41 and lower end face 42 of the electrode winding body 20, i.e., in the Z-axis direction, thereby locally bending a portion of the upper end face 41 and a portion of the lower end face 42 (primary press). As a result, multiple grooves 41G are formed on the upper end face 41 and multiple grooves 42G are formed on the lower end face 42. Note that the number and arrangement of grooves 41G shown in Figure 11(B) are illustrative examples and the present disclosure is not limited thereto.

[0075] Next, substantially the same pressure is applied substantially simultaneously and perpendicularly to the upper end face 41 and lower end face 42 from above and below the electrode winding body 20 (secondary press). At this time, a rod-shaped jig, for example, is inserted into the through hole 26. By doing so, as shown in Figure 11(C), the first portion 222A of the positive electrode exposed region 212 and the negative electrode exposed region 222 are bent, respectively, so that a part of the upper end face 41 and a part of the lower end face 42 are flattened, respectively, to form convex portions 41T and 42T (not shown in Figure 11). At this time, it is desirable that multiple adjacent portions of the positive electrode edge 212E of the positive electrode exposed region 212 on the upper end face 41 bend toward the through hole 26 so that they overlap each other in the radial direction of the electrode winding body 20. Similarly, it is preferable that multiple adjacent portions of the negative electrode edge 222E of the negative electrode exposed region 222 on the lower end face 42 bend toward the through hole 26 so that they overlap each other in the radial direction of the electrode winding body 20. After that, the fan-shaped portion 31 of the positive electrode current collector plate 24 is joined to the protrusion 41T of the upper end face 41 by laser welding or the like, and the fan-shaped portion 33 of the negative electrode current collector plate 25 is joined to the protrusion 42T of the lower end face 42 by laser welding or the like. This forms the first joint portion 61 and the second joint portion 62.

[0076] Next, insulating tapes 53 and 54 are attached to the predetermined positions on the electrode winding 20. Then, as shown in Figure 11(D), the strip portion 32 of the positive electrode current collector plate 24 is bent and inserted through the hole 12H of the insulating plate 12. Also, the strip portion 34 of the negative electrode current collector plate 25 is bent and inserted through the hole 13H of the insulating plate 13.

[0077] Next, the electrode winding body 20 assembled as described above is inserted into the outer casing 11 shown in Figure 11(E), and then the bottom 11B of the outer casing 11 and the negative electrode current collector plate 25 are welded together. After that, a constricted portion 11S is formed near the open end 11N of the outer casing 11. Furthermore, after the electrolyte is injected into the outer casing 11, the strip portion 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 are welded together.

[0078] Next, as shown in Figure 11(F), the constricted portion 11S is used to seal the outer can 11 with the gasket 15, safety valve mechanism 30, and battery cover 14. Finally, the outer tube 50 is placed over the outer can 11 with the washer 55 attached on top of the battery cover 14, and then the outer tube 50 is heated and shrunk by applying hot air to it, so that the outer tube 50 is tightly attached to the outer surface of the outer can 11.

[0079] With the above steps, the secondary battery 1 of this embodiment is completed.

[0080] [1-4. Action and Effects] Thus, in the secondary battery 1 of this embodiment, each of the one or more first junctions 61 has a meander-shaped planar form, and the length 61La of the first junction 61 from the a-th first fold portion 61Ba to the a+1-th first fold portion 61B(a+1), counting from the winding center, is longer than the length 61L1 of the first fold portion 61B1 to the second first fold portion 61B2, counting from the winding center of the electrode winding body 20, in the winding direction (θ direction). Therefore, current can be extracted evenly from the entire laminate S20 from the innermost to the outermost part of the electrode winding body 20. Thus, high output can be obtained. In addition, since it is possible to avoid localized high-frequency use of a part of the positive electrode active material layer 21B and the negative electrode active material layer 22B of the laminate S20, localized performance degradation of the positive electrode active material layer 21B and the negative electrode active material layer 22B can be suppressed. Therefore, good charge-discharge cycle characteristics can be obtained with secondary battery 1.

[0081] In contrast, the first junction portion 161-1 in the secondary battery 101, shown in Figure 23 as the first comparative example, extends linearly in the radial direction (R direction). Furthermore, although the first junction portion 161-2 in the secondary battery 102, shown in Figures 24A and 24B as the second comparative example, has a meander-shaped planar form, the length 161L1 in the winding direction (θ direction) from the first first folded portion 161B1 to the second first folded portion 161B2, counting from the winding center of the electrode winding body 20, is equal to the length 161La in the winding direction (θ direction) of the first junction portion 161-2 from the a-th first folded portion 161Ba to the a+1-th first folded portion 161B(a+1), counting from the winding center. Therefore, as the electrode winding body 20 moves from the winding center towards the winding outer circumference, the density of contact points between the positive electrode edge 212E of the positive electrode current collector 21A and the fan-shaped portion 31 of the positive electrode current collector plate 24 decreases. As a result, current cannot be sufficiently extracted from the positive electrode active material layer 21B and the negative electrode active material layer 22B in the winding portion of the electrode winding body 20 that is closer to the winding outer circumference. Consequently, sufficient output may not be obtained. In addition, the positive electrode active material layer 21B and the negative electrode active material layer 22B in the winding portion of the electrode winding body 20 that is closer to the winding center will be used at a high frequency, which may accelerate the deterioration of the charge-discharge cycle characteristics.

[0082] Furthermore, in the secondary battery 1 of this embodiment, each of the one or more second junctions 62 also has a meander-shaped planar form, and the length 62Lb in the winding direction (θ direction) of the second junction 62 from the bth second fold portion 62Bb to the b+1th second fold portion 62B(b+1), counting from the winding center, is longer than the length 62L1 in the winding direction (θ direction) from the first second fold portion 62B1 to the second second fold portion 62B2, counting from the winding center of the electrode winding body 20. As a result, current can be extracted more evenly from the entire laminate S20 from the innermost to the outermost part of the electrode winding body 20. Thus, even higher output can be obtained, and even better charge-discharge cycle characteristics can be obtained.

[0083] Furthermore, in the secondary battery 1 of this embodiment, the dimensions of the first joint 61 in the winding direction (θ direction) and the dimensions of the second joint 62 in the winding direction (θ direction) are arranged to gradually increase from the winding center side toward the winding outer circumference side. As a result, current can be extracted more evenly from the entire laminate S20 from the innermost part to the outermost part of the electrode winding body 20. Thus, even higher output power can be obtained, and even better charge-discharge cycle characteristics can be obtained.

[0084] Thus, according to the secondary battery 1 of one embodiment of the present disclosure, excellent performance is achieved.

[0085] <2. Application Examples> The applications of the secondary battery 1 as one embodiment of the present disclosure described above are, for example, as follows. [2-1. Battery Pack] Figure 12 is a block diagram showing an example of a circuit configuration when a battery according to one embodiment of the present invention (hereinafter appropriately referred to as a secondary battery) is applied to a battery pack 300. The battery pack 300 comprises a battery pack 301, an outer casing 305, a switch section 304 comprising a charge control switch 302a and a discharge control switch 303a, a current detection resistor 307, a temperature detection element 308, and a control unit 310.

[0086] The battery pack 300 is equipped with a positive terminal 321 and a negative terminal 322. During charging, the positive terminal 321 and the negative terminal 322 are connected to the positive and negative terminals of the charger, respectively, and charging takes place. When using electronic equipment, the positive terminal 321 and the negative terminal 322 are connected to the positive and negative terminals of the electronic equipment, respectively, and discharge takes place.

[0087] The battery pack 301 is formed by connecting multiple secondary batteries 301a in series or in parallel. The secondary battery 1 described above can be used as the secondary battery 301a. In Figure 12, an example is shown where six secondary batteries 301a are connected in 2 parallel and 3 series (2P3S), but any other connection method is acceptable, such as n parallel and m series (where n and m are integers).

[0088] The switch unit 304 comprises a charge control switch 302a and a diode 302b, and a discharge control switch 303a and a diode 303b, and is controlled by the control unit 310. Diode 302b has polarity that is reverse to the charging current flowing from the positive terminal 321 towards the battery pack 301, and forward to the discharge current flowing from the negative terminal 322 towards the battery pack 301. Diode 303b has polarity that is forward to the charging current and reverse to the discharge current. In Figure 12, the switch unit 304 is provided on the + side, but it may also be provided on the - side.

[0089] The charge control switch 302a is turned off when the battery voltage reaches the overcharge detection voltage, and is controlled by the charge / discharge control unit to prevent charging current from flowing through the current path of the battery pack 301. After the charge control switch 302a is turned off, only discharge is possible via the diode 302b. Furthermore, if a large current flows during charging, it is turned off by the control unit 310 to cut off the charging current flowing through the current path of the battery pack 301. The discharge control switch 303a is turned off when the battery voltage reaches the over-discharge detection voltage, and is controlled by the control unit 310 to prevent discharge current from flowing through the current path of the battery pack 301. After the discharge control switch 303a is turned off, only charging is possible via the diode 303b. Furthermore, if a large current flows during discharge, it is turned off by the control unit 310 to cut off the discharge current flowing through the current path of the battery pack 301.

[0090] The temperature detection element 308 is, for example, a thermistor, and is located near the battery pack 301 to measure the temperature of the battery pack 301 and supply the measured temperature to the control unit 310. The voltage detection unit 311 measures the voltage of the battery pack 301 and each of the secondary batteries 301a that make up the battery pack, performs A / D conversion on this measured voltage, and supplies it to the control unit 310. The current measurement unit 313 measures the current using the current detection resistor 307 and supplies this measured current to the control unit 310. The switch control unit 314 controls the charge control switch 302a and the discharge control switch 303a of the switch unit 304 based on the voltage and current input from the voltage detection unit 311 and the current measurement unit 313.

[0091] The switch control unit 314 prevents overcharging, over-discharging, and overcurrent charging / discharging by sending a control signal to the switch unit 304 when the voltage of any of the multiple secondary batteries 301a falls below the overcharge detection voltage or the over-discharge detection voltage, or when a large current flows rapidly. Here, for example, if the secondary battery is a lithium-ion secondary battery, the overcharge detection voltage is set to, for example, 4.20V ± 0.05V, and the over-discharge detection voltage is set to, for example, 2.4V ± 0.1V.

[0092] The charge / discharge switch can use a semiconductor switch such as a MOSFET. In this case, the parasitic diodes of the MOSFET function as diodes 302b and 303b. When a P-channel FET is used as the charge / discharge switch, the switch control unit 314 supplies control signals DO and CO to the gates of the charge control switch 302a and the discharge control switch 303a, respectively. When the charge control switch 302a and the discharge control switch 303a are P-channel type, they turn ON when the gate potential is lower than a predetermined value or more below the source potential. That is, in normal charging and discharging operation, the control signals CO and DO are set to a low level, and the charge control switch 302a and the discharge control switch 303a are turned ON.

[0093] For example, in the event of overcharging or over-discharging, the control signals CO and DO are set to high levels, and the charge control switch 302a and the discharge control switch 303a are turned OFF.

[0094] Memory 317 consists of RAM and ROM, such as EPROM (Erasable Programmable Read Only Memory), which is a non-volatile memory. Memory 317 pre-stores numerical values ​​calculated by the control unit 310 and the internal resistance values ​​of each secondary battery 301a in its initial state, measured during the manufacturing process, and can be rewritten as needed. In addition, by storing the full charge capacity of the secondary battery 301a, it is possible to calculate the remaining capacity, for example, in conjunction with the control unit 310.

[0095] The temperature detection unit 318 measures the temperature using the temperature detection element 308 and performs charge / discharge control in the event of abnormal heat generation, as well as making corrections when calculating the remaining capacity.

[0096] [2-2. Energy Storage Systems] The secondary battery according to one embodiment of the present disclosure described above can be installed in or used to supply power to devices such as electronic equipment, electric vehicles, electric aircraft, and energy storage devices.

[0097] Examples of electronic devices include laptop computers, smartphones, tablet devices, PDAs (personal digital assistants), mobile phones, wearable devices, cordless phone handsets, video cameras, digital still cameras, e-books, electronic dictionaries, music players, radios, headphones, game consoles, navigation systems, memory cards, pacemakers, hearing aids, power tools, electric shavers, refrigerators, air conditioners, televisions, stereos, water heaters, microwave ovens, dishwashers, washing machines, dryers, lighting equipment, toys, medical devices, robots, road conditioners, and traffic lights.

[0098] Electric vehicles include railway cars, golf carts, electric carts, and electric vehicles (including hybrid vehicles), and these are used as power sources or auxiliary power sources for their operation. Energy storage devices include power sources for buildings such as houses, or for storing electricity in power generation facilities.

[0099] <3. Variant> (First variation) Next, a secondary battery 1A, as a first modified example of the secondary battery 1 of the above embodiment, will be described. Figure 13A is a plan view showing an example of the configuration of the first joint portion 61-1 between the upper end face 41 of the electrode winding body 20 and the positive electrode current collector plate 24 in secondary battery 1A. Figure 13B is a schematic plan view showing an enlarged view of the first joint portion 61-1 shown in Figure 13A. In the first joint portion 61 of the above embodiment, the ratio of length L(a+1) to length La, L(a+1) / La, is substantially equal to the ratio of length L(a+2) / L(a+1) of the length in the winding direction (θ direction) from the (a+1)th first folded portion 61B(a+1) to the (a+2)th first folded portion 61B(a+2) counted from the winding center. In contrast, in the first joint 61-1 of this modified example, the ratio L(a+1) / La and the ratio L(a+2) / L(a+1) are different. Specifically, the ratio of length 61L3 to length 61L2 (61L3) / (61L2) is larger than the ratio of length 61L2 to length 61L1 (61L2) / (61L1). In addition, in the secondary battery 1A, the second joint 62 can be configured in the same way as the first joint 61-1.

[0100] (Second variation) Next, a secondary battery 1B, which is a second modification of the secondary battery 1 of the above embodiment, will be described. Figure 14A is a plan view showing an example of the configuration of the first joint portion 61-2 between the upper end face 41 of the electrode winding body 20 and the positive electrode current collector plate 24 in secondary battery 1B. Figure 14B is a schematic plan view showing an enlarged view of the first joint portion 61-2 shown in Figure 14A. In the first joint portion 61 of the above embodiment, the dimension of the first joint portion 61 in the winding direction (θ direction) gradually increases from the winding center side toward the winding outer circumference side. In contrast, the first joint portion 61-2 includes a portion where the length 61La is longer than the length 61L(a+1). However, the length 61L1 is the minimum. Specifically, in the example configuration of the first joint portion 61-2, 61L1 < 61L6 < 61L2 < 61L7 < 61L5 < 61L3 < 61L4. Furthermore, in the secondary battery 1B, the second junction 62 can have the same configuration as the first junction 61-2.

[0101] (Third variation) Next, secondary batteries 1C-1 and 1C-2 will be described as third modifications of the secondary battery 1 of the above embodiment. Figure 15A is a plan view showing an example of the configuration of the first joint 61 between the upper end face 41 of the electrode winding body 20 and the positive electrode current collector plate 24 in secondary battery 1C-1, which is the first example of the third modification. Figure 15B is a plan view showing an example of the configuration of the first joint 61 between the upper end face 41 of the electrode winding body 20 and the positive electrode current collector plate 24 in secondary battery 1C-2, which is the second example of the third modification. In the above embodiment, six first joints 61 are provided, but in secondary battery 1C-1, four first joints 61 are provided, and in secondary battery 1C-2, three first joints 61 are provided. In secondary batteries 1C-1 and 1C-2B, the respective second joints 62 can be configured in the same way as the respective first joints 61.

[0102] (Fourth variation) Next, a secondary battery 1D, which is a fourth modification of the secondary battery 1 of the above embodiment, will be described. Figure 16 is a plan view showing an example of the configuration of the first joint 61 between the upper end face 41 of the electrode winding body 20 and the positive electrode current collector plate 24 in the secondary battery 1D, which is the fourth modification. In the secondary battery 1D, which is the fourth modification, a portion extending radially, for example, is provided at the end of the first joint 61 on the winding center side. This makes it possible to increase the number of joint locations between the upper end face 41 and the positive electrode current collector plate 24, even in the narrow area near the opening 35 provided in the center of the fan-shaped portion 31 of the positive electrode current collector plate 24. In addition, in the secondary battery 1D, the second joint 62 can be configured in the same way as the first joint 61.

[0103] (Fifth variation) Next, a secondary battery 1E, which is a fifth modification of the secondary battery 1 of the above embodiment, will be described. Figure 17 is a plan view showing an example of the configuration of the first joint 61 between the upper end face 41 of the electrode winding body 20 and the positive electrode current collector plate 24 in the secondary battery 1E, which is the fifth modification. In the secondary battery 1E, which is the fifth modification, the first linear portion 61A of the first joint 61 does not extend in a straight line, but is curved along the winding direction. In addition, in the secondary battery 1E, the second joint 62 can be configured in the same way as the first joint 61.

[0104] (Sixth variation) Next, a secondary battery 1F, which is a sixth modification of the secondary battery 1 of the above embodiment, will be described. Figure 18 is a plan view showing an example of the configuration of the first joint 61 between the upper end face 41 of the electrode winding body 20 and the positive electrode current collector plate 24 in the secondary battery 1F, which is the sixth modification. In the secondary battery 1F, which is the sixth modification, a positive electrode current collector plate 24F is used instead of the positive electrode current collector plate 24. The positive electrode current collector plate 24F has a disc portion 241 instead of a fan-shaped portion 31 and a strip-shaped portion 242 instead of a strip-shaped portion 32. The disc portion 241 of the positive electrode current collector plate 24F has a planar shape that corresponds to the planar shape of the upper end face 41. Therefore, in the secondary battery 1F, each of the convex portions 41T can be joined to the disc portion 241 of the positive electrode current collector plate 24F by the first joint 61. Aside from that point, the configuration of secondary battery 1F is substantially the same as the configuration of secondary battery 1C-1, which is the first example of the third modified example shown in Figure 15A. In secondary battery 1F, the second junction 62 can also be configured in the same way as the first junction 61. A secondary battery 1F with this configuration can obtain a higher output than secondary battery 1C-1. In secondary battery 1F, the second junction 62 can also be configured in the same way as the first junction 61.

[0105] (Seventh variation) Furthermore, as shown in Figure 19 as the seventh modified example, the secondary battery 1G may be used, which does not have a strip-shaped portion and consists only of a disc portion having a planar shape corresponding to the planar shape of the upper end face 41. However, the positive electrode current collector plate 24G has an opening 35. In the secondary battery 1G as well, each of the protrusions 41T and the positive electrode current collector plate 24G can be joined by the first joint portion 61. In the secondary battery 1G, the second joint portion 62 can also be configured in the same way as the first joint portion 61.

[0106] (Variation 8) In this disclosure, a positive electrode current collector plate 24H may be used, as in the secondary battery 1H shown in Figure 20 as an eighth modified example. The positive electrode current collector plate 24H does not have a strip-shaped portion, but consists only of a disc portion having a planar shape corresponding to the planar shape of the upper end face 41, and does not have an opening 35. In the secondary battery 1H as well, each of the protrusions 41T can be joined to the positive electrode current collector plate 24H by the first joint portion 61. In the secondary battery 1H, the second joint portion 62 can also have the same configuration as the first joint portion 61.

[0107] (9th variation) In this disclosure, a positive electrode current collector plate 24I having a shape other than circular may be used, as in the secondary battery 1I shown in Figure 21 as a ninth modified example. In the secondary battery 1I, the second junction 62 can have the same configuration as the first junction 61.

[0108] (10th variation) In this disclosure, as shown in Figure 22 as a tenth modified example, the secondary battery 1J may have a single protrusion 41T instead of a groove 41G on the upper end face 41 of the electrode winding body 20. In the secondary battery 1I, the second junction 62 can have the same configuration as the first junction 61. That is, the lower end face 42 of the electrode winding body 20 may have a single protrusion 42T instead of a groove 42G.

[0109] The present disclosure has been described above with reference to one embodiment and several modifications, but the configuration of the present disclosure is not limited to the configuration described in the above embodiment and several modifications, and can be modified in various ways. For example, in the above embodiment, the case in which the electrode reactant is lithium was described, but the electrode reactant is not particularly limited. For this reason, the electrode reactant may be other alkali metals such as sodium and potassium, as described above, or alkaline earth metals such as beryllium, magnesium and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0110] Furthermore, in the secondary battery of this disclosure, the length of the first linear portion and the length of the second linear portion at the first junction are not particularly limited. Also, if multiple first junctions are provided, their shapes and thicknesses may be uniform for all of the first junctions, or the shapes and thicknesses of some of the first junctions may differ from those of the other first junctions. The same applies if multiple second junctions are provided.

[0111] Furthermore, if multiple first joints are provided, the number of first folded portions in each of the multiple first joints may be different. The same applies if multiple second joints are provided.

[0112] According to one embodiment of the secondary battery of this disclosure, each of the one or more first junctions has a predetermined meander-shaped planar form, so that current can be extracted without bias from the entire laminate from the innermost to the outermost part of the electrode winding. Therefore, high output can be obtained. The effects described herein are merely illustrative, and the effects of this disclosure are not limited to those described herein. Therefore, other effects may be obtained with respect to this disclosure. [Explanation of Symbols]

[0113] 1...Lithium-ion secondary battery, 11...Outer casing, 11B...Bottom, 11N...Open end, 11W...Side wall, 12,13...Insulating plate, 14...Battery cover, 15...Gasket, 20...Electrode winding, S20...Laminate, 21...Positive electrode, 21A...Positive electrode current collector, 21B...Positive electrode active material layer, 21BT1...First end edge, 211...Positive electrode covering region, 212...Positive electrode exposed region, 22...Negative electrode, 22A...Negative electrode current collector, 22B...Negative electrode active material layer, 221...Negative electrode covering region, 222...Negative electrode exposed region, 23...Separator, 23A...First separator member, 23B...First 2 Separator members, 24... Positive electrode current collector plate, 25... Negative electrode current collector plate, 26... Through hole, 30... Safety valve mechanism, 31, 33... Fan-shaped part, 32, 34... Strip-shaped part, 35, 36... Opening, 41... Upper end face, 41G1, 41G2... Groove part, 42... Lower end face, 42G1, 42G2... Groove part, 50... Outer tube, 53, 54... Insulating tape, 55... Washer, 61... First joint, 61A... First linear part, 61B... First folded part, 62... Second joint, 62A... Second linear part, 62B... Second folded part, 100... Insulating layer, CL... Central axis.

Claims

1. A laminate comprising a first electrode, a second electrode, and a separator is wound along the longitudinal direction of the laminate, and the electrode winding body has through holes penetrating in a width direction perpendicular to the longitudinal direction, The electrode winding body is sandwiched in the width direction by a first electrode current collector plate and a second electrode current collector plate facing each other. Equipped with, The electrode winding body has a first end face facing the first electrode current collector plate in the width direction, and a second end face facing the second electrode current collector plate in the width direction. The first electrode current collector plate and the first end face are joined by one or more first joints. Each of the one or more first joints has a meander-shaped planar form that includes a plurality of first linear portions adjacent to each other in the radial direction of the electrode winding body in a plane perpendicular to the through hole, and a plurality of first folded portions connecting the plurality of first linear portions. In each of the one or more first joints, when the number of the plurality of first folded portions is n (where n is a natural number), the length in the winding direction of the electrode winding body from the first first folded portion counted from the winding center of the plurality of first folded portions to the second first folded portion counted from the winding center is longer than the length in the winding direction of the electrode winding body from the a-th (where a is a natural number between 2 and n) first folded portion counted from the winding center of the first joint. Secondary battery.

2. In each of the one or more first joints, The first length in the winding direction from the (a-1)th first folded portion (where a is a natural number between 2 and (n-1)) counting from the winding center to the ath first folded portion counting from the winding center is greater than: The (a+1)th first folded portion from the winding center, counting from the a-th first folded portion. The second length in the winding direction up to the folded portion is longer. The secondary battery according to claim 1.

3. The ratio of the second length to the first length is, The ratio of the third length in the winding direction from the (a+1)th first fold portion to the (a+2)th first fold portion counted from the winding center to the second length is substantially equal to the ratio of the third length in the winding direction to the second length. The secondary battery according to claim 2.

4. The first electrode comprises a first electrode current collector and a first electrode active material layer covering a portion of the first electrode current collector. The first electrode includes a first electrode covering region in which the first electrode current collector foil is covered with a first electrode active material layer, and a first electrode exposed region adjacent to the first electrode covering region in the width direction, wherein the first electrode exposed region is joined to the first electrode current collector plate. The first end face is a plurality of bent portions of the edge of the first electrode exposed region in the wound state, The radial spacing between the plurality of first linear portions is shorter than the radial length of each of the plurality of portions that form the first end face of the edge of the first electrode exposure region. The secondary battery according to claim 1.

5. The first end face includes one or more first grooves extending in the radial direction and a first protrusion that protrudes further toward the first electrode current collector plate than the one or more first grooves. Each of the one or more first joints is a portion where a part of the first protrusion and a part of the first electrode current collector plate are joined together. The secondary battery according to claim 4.

6. The one or more first joints are a plurality of first joints, The plurality of first joints are provided spaced apart from each other. The secondary battery according to claim 1.

7. The number of the one or more first joints is three or more. The secondary battery according to claim 1.

8. The second electrode current collector plate and the second end face are joined by one or more second joints. Each of the one or more second joints has a meander-shaped planar form in a plane perpendicular to the through hole, including a plurality of second linear portions adjacent in the radial direction and a plurality of second folded portions connecting the plurality of second linear portions. In each of the one or more second joints, when the number of the plurality of second folded portions is m (where m is a natural number), the length in the winding direction from the b-th (where b is a natural number between 2 and m) second folded portion to the (b+1)th second folded portion of the plurality of second folded portions of the second joint is longer than the length in the winding direction from the first second folded portion counted from the winding center to the second second folded portion counted from the winding center. The secondary battery according to claim 1.

9. In each of the one or more second joints, The fourth length in the winding direction from the (b-1)th second folded portion (where b is a natural number between 2 and (m-1)) counting from the winding center to the bth second folded portion counting from the winding center is greater than: The fifth length in the winding direction, from the b-th second fold portion to the (b+1)th second fold portion counted from the winding center, is longer. The secondary battery according to claim 8.

10. The ratio of the fifth length to the fourth length is, The ratio of the sixth length in the winding direction from the (b+1)th second fold portion to the (b+2)th second fold portion counted from the winding center to the fifth length is substantially equal to the ratio of the sixth length in the winding direction to the fifth length. The secondary battery according to claim 9.

11. The second electrode comprises a second electrode current collector and a second electrode active material layer covering a portion of the second electrode current collector. The second electrode includes a second electrode covering region in which the second electrode current collector is covered with the second electrode active material layer, and a second electrode exposed region adjacent to the second electrode covering region in the width direction, wherein the second electrode exposed region is joined to the second electrode current collector plate. The second end face is a plurality of bent portions of the edge of the wound second electrode exposed region, The radial spacing between the plurality of second linear portions is shorter than the radial length of each of the plurality of portions that form the second end face of the edge of the second electrode exposed region. The secondary battery according to claim 8.

12. The second end face includes one or more second grooves extending in the radial direction and a second protrusion that protrudes further toward the second electrode current collector plate than the one or more second grooves. Each of the one or more second joints is a portion where a part of the second protrusion and a part of the second electrode current collector plate are joined together. The secondary battery according to claim 11.

13. The one or more second joints mentioned above are a plurality of second joints, The plurality of second joints are provided spaced apart from each other. The secondary battery according to claim 8.

14. The number of the aforementioned one or more second joints is three or more. The secondary battery according to claim 8.

15. The first electrode is the positive electrode, and the second electrode is the negative electrode. A secondary battery according to any one of claims 1 to 14.

16. A secondary battery according to any one of claims 1 to 14, A control unit for controlling the secondary battery, The outer casing enclosing the aforementioned secondary battery and A battery pack that has [a certain feature].

Images