Secondary battery and its manufacturing method, battery pack

Abstract

The present invention provides a secondary battery that has higher reliability. This secondary battery comprises an electrode winding body, a first electrode current collector plate, and a second electrode current collector plate. The electrode winding body has a laminate in which a first electrode and a second electrode are laminated with a separator interposed therebetween, said laminate being wound about a central axis that extends in a first direction, and having a first end surface and a second end surface that are on opposite sides from each other in the first direction. The first electrode current collector plate faces the first end surface of the electrode winding body and is connected to the first electrode. The second electrode current collector plate faces the second end surface of the electrode winding body and is connected to the second electrode. The first electrode has a first electrode covered portion in which a first electrode current collector is covered by a first electrode active material layer, and a first electrode exposed portion in which the first electrode current collector is exposed and not covered by the first electrode active material layer. A plurality of first edge portions among the first electrode exposed portion, said first edge portions being adjacent in the radial direction of the electrode winding body, are bent toward the central axis so as to overlap each other, thereby forming the first end surface, and each tip portion of the plurality of first edge portions includes a first curved surface.

Description

Technical Field

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

Background Art

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

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

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

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

[0007] A secondary battery according to one embodiment of the present disclosure comprises an electrode winding body, a first electrode current collector plate, and a second electrode current collector plate. The electrode winding body is formed by winding a laminate in which a first electrode and a second electrode are stacked with a separator between them, around a central axis extending in a first direction, and has a first end face and a second end face facing each other in the first direction. The first electrode current collector plate is connected to the first electrode while facing the first end face of the electrode winding body. The second electrode current collector plate is connected to the second electrode while facing the second end face of the electrode winding body. The first electrode has a first electrode covering portion in which the first electrode current collector is covered with a first electrode active material layer, and a first electrode exposed portion in which the first electrode current collector is exposed without being covered by the first electrode active material layer. Here, a plurality of first edges of the electrode winding body that are adjacent in the radial direction of the exposed first electrode are bent toward the central axis so as to overlap each other, forming a first end face, and each of the tips of the plurality of first edges includes a first curved surface.

[0008] According to one embodiment of the secondary battery of this disclosure, the adhesion between multiple first edges of the first electrode current collector and the first electrode current collector plate is improved without the shape of the electrode winding being distorted, resulting in a good bonding state. Therefore, internal resistance can be reduced, and a higher output can be obtained.

[0009] Furthermore, the effects of this disclosure are not necessarily limited to those described herein, but may include any 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 the configuration 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 configuration of the 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 FIG. 1. [Figure 4C] Figure 4C is an enlarged cross-sectional view showing an enlarged positive electrode edge shown in FIG. 4B. [Figure 5A] Figure 5A is a developed view of the negative electrode shown in FIG. 1. [Figure 5B] Figure 5B is a cross-sectional view of the negative electrode shown in FIG. 1. [Figure 5C] Figure 5C is an enlarged cross-sectional view showing an enlarged negative electrode edge shown in FIG. 5B. [Figure 6A] Figure 6A is a plan view of the positive electrode current collector shown in FIG. 1. [Figure 6B] Figure 6B is a plan view of the negative electrode current collector shown in FIG. 1. [Figure 7] Figure 7 is a perspective view for explaining the manufacturing process of the secondary battery shown in FIG. 1. [Figure 8A] Figure 8A is a schematic diagram showing the step of cutting the positive electrode current collector in the manufacturing process of the secondary battery of FIG. 7. [Figure 8B] Figure 8B is a schematic diagram showing an enlarged cut surface of the positive electrode current collector cut by the step of FIG. 8A. [Figure 9A] Figure 9A is a schematic diagram showing the step of cutting the negative electrode current collector in the manufacturing process of the secondary battery of FIG. 7. [Figure 9B] Figure 9B is a schematic diagram showing an enlarged cut surface of the negative electrode current collector cut by the step of FIG. 9A. [Figure 10] Figure 10 is a block diagram showing the circuit configuration of a battery pack to which the secondary battery according to an embodiment of the present disclosure is applied. [Figure 11A] Figure 11A is an enlarged cross-sectional view showing an enlarged positive electrode edge of Comparative Example 1. [Figure 11B] Figure 11B is an enlarged cross-sectional view showing an enlarged negative electrode edge of Comparative Example 1.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. The order of description is as follows. 0. Background 1. Secondary battery 1-1. Structure 1-2. Operation 1-3. Manufacturing method 1-4. Function and effect 1-5. Variation 2. Application examples 2-1. Battery pack 2-2. Power storage system

[0012] <0. Background> Conventionally, a secondary battery having a positive electrode terminal (positive electrode tab) and a negative electrode terminal (negative electrode tab) for current extraction, which are electrically connected to the positive electrode and the negative electrode constituting the battery element, respectively, has been widely used. Here, it is called a secondary battery with a tab structure. However, generally, in a secondary battery with a tab structure, the positive electrode terminal and the negative electrode terminal have a strip-shaped elongated shape, and the area of the connection portion between the positive electrode terminal and the positive electrode and the area of the connection portion between the negative electrode terminal and the negative electrode are narrow. Therefore, the electrical resistance at these connection portions becomes high, which can cause an increase in the internal resistance of the battery. In recent years, charge and discharge at a higher load rate have been increasingly demanded. However, in a secondary battery with a tab structure, when charging at a high load rate, the temperature inside the battery tends to rise because the internal resistance is large.

[0013] Therefore, the applicant has developed a secondary battery called a so-called tabless structure that does not use electrode terminals (tabs) connected to the positive electrode and the negative electrode of the battery element (see, for example, Patent Document 1 mentioned above). In this tabless structure secondary battery, instead of using a positive electrode tab and a negative electrode tab, a positive electrode current collector plate and a negative electrode current collector plate are used, and the positive electrode current collector plate and the negative electrode current collector plate are connected to the positive electrode and the negative electrode of the battery element with a larger contact surface. Therefore, the internal resistance is extremely small compared to a secondary battery with a tab structure, enabling charge and discharge with a relatively large current.

[0014] Thus, secondary batteries with a tablet structure have significantly lower internal resistance compared to secondary batteries with a tab structure, which helps suppress the rise in battery temperature during charging at high load rates. The applicant has further investigated and proposed a secondary battery with a tablet structure that can further reduce internal resistance. The secondary battery described below in detail.

[0015] <1. Secondary battery> First, a secondary battery according to one embodiment of this disclosure will be described.

[0016] 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 battery using an electrode reactant other than lithium.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] [1-1. Structure] (Lithium-ion secondary battery 1) Figure 1 shows the 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. In the secondary battery 1 shown in Figure 1, the electrode winding 20, which serves as the battery element, is housed inside the cylindrical outer casing 11.

[0021] 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 an outer casing 11. The electrode winding body 20 is a structure in which a positive electrode 21 and a negative electrode 22 are stacked and wound together via a separator 23. The electrode winding body 20 is impregnated with an electrolyte, which is a liquid electrolyte. The secondary battery 1 may further include one or more of a thermal resistance (PTC) element and a reinforcing member inside the outer casing 11.

[0022] (Outer can 11) The outer casing 11 has a hollow cylindrical structure in which, for example, the lower end in the Z-axis direction (height direction) is closed and the upper end is open. Therefore, the upper end of the outer casing 11 is an open end 11N. The constituent material of the outer casing 11 includes, for example, a metal material such as iron. However, the surface of the outer casing 11 may be plated with, for example, a metal material such as nickel. The insulating plates 12 and 13 are arranged facing each other in the Z-axis direction, for example, with the electrode winding 20 sandwiched between them. In this specification, in the Z-axis direction, the open end 11N and its vicinity may be referred to as the upper part of the secondary battery 1, and the closed part of the outer casing 11 and its vicinity may be referred to as the lower part of the secondary battery 1.

[0023] (Insulating boards 12, 13) Each of the insulating plates 12 and 13 is, for example, a dish-shaped plate having a surface perpendicular to the central axis CL of the electrode winding 20, i.e., a surface perpendicular to the Z-axis in Figure 1. The insulating plates 12 and 13 are arranged so as to sandwich the electrode winding 20.

[0024] (Crimping structure 11R) At the open end 11N of the outer casing 11, a crimped structure 11R is formed, in which, for example, the battery cover 14 and the safety valve mechanism 30 are crimped together via a gasket 15. The battery cover 14 seals the outer casing 11 with the electrode winding 20 and the like housed inside. The crimped structure 11R is a so-called crimp structure and has a bent portion 11P that functions as a so-called crimped portion.

[0025] (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 contains, for example, the same material as the outer casing 11. 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.

[0026] (Gasket 15) The gasket 15 is a sealing member mainly interposed between the folded portion 11P of the outer can 11 and the battery cover 14. The gasket 15 seals the gap between the folded portion 11P and the battery cover 14. However, the surface of the gasket 15 may be coated with, for example, asphalt. The gasket 15 contains, for example, one or more types of insulating materials. The type of insulating material is not particularly limited, but examples include polymer materials such as polybutylene terephthalate (PBT) and polypropylene (PP). Among these, polybutylene terephthalate is preferred as the insulating material. This is because it sufficiently seals the gap between the folded portion 11P and the battery cover 14 while electrically separating the outer can 11 and the battery cover 14 from each other.

[0027] (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.

[0028] (Electrode winding body 20) The electrode winding 20 is a power generation element that carries out the 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.

[0029] Figure 2 is an unfolded view of the electrode winding 20, schematically representing a part of the laminate S20 including the positive electrode 21, the negative electrode 22, and the separator 23. In the laminate S20 obtained by unfolding the electrode winding 20, the positive electrode 21 and the negative electrode 22 are stacked on top of each other via the separator 23. The separator 23 has, for example, two base materials, namely a first separator member 23A and a second separator member 23B. Therefore, the electrode winding 20 has a four-layer laminate S20 in which the positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are stacked in that order. The positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are all substantially strip-shaped members with the W-axis direction as the short side and the L-axis direction as the long side.

[0030] As shown in Figure 3, the electrode winding body 20 is formed by winding the laminate S20 around a central axis CL (see Figure 1) 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. At this time, the laminate S20 is wound in an orientation where the W-axis direction approximately coincides with the Z-axis direction. Figure 3 shows one example configuration along the horizontal cross-section perpendicular to the Z-axis direction of the electrode winding body 20. However, in Figure 3, the separator 23 is omitted from the illustration 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.

[0031] The positive electrode 21, negative electrode 22, and separator 23 are wound such that the separator 23 is positioned on the outermost circumference and innermost circumference of the electrode winding body 20, respectively. Furthermore, at the outermost circumference of the electrode winding body 20, the negative electrode 22 is positioned outside the positive electrode 21. That is, as shown in Figure 3, the outermost positive electrode portion 21out of the positive electrode 21 contained in the electrode winding body 20 is positioned inside the outermost negative electrode portion 22out of the negative electrode 22 contained in the electrode winding body 20. Here, the outermost positive electrode portion 21out is the outermost one turn of the positive electrode 21 in the electrode winding body 20. The outermost negative electrode portion 22out is the outermost one turn of the negative electrode 22 in the electrode winding body 20. On the other hand, at the innermost circumference of the electrode winding body 20, the negative electrode 22 is positioned inside the positive electrode 21. In other words, as shown in Figure 3B, the innermost negative electrode portion 22in, located at the innermost circumference of the negative electrode 22 included in the electrode winding body 20, is located inside the innermost positive electrode portion 21in, located at the innermost circumference of the positive electrode 21 included in the electrode winding body 20. Here, the innermost positive electrode portion 21in is the innermost one turn of the positive electrode 21 in the electrode winding body 20. The innermost negative electrode portion 22in is the innermost one turn of the negative electrode 22 in the electrode winding body 20. The number of turns of the positive electrode 21, the negative electrode 22, and the separator 23 are not particularly limited and can be set arbitrarily.

[0032] 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 and a positive electrode active material layer 21B provided on the positive electrode current collector 21A. The positive electrode active material layer 21B may be provided on only one side of the positive electrode current collector 21A, or on both sides of the positive electrode current collector 21A. Figure 4B shows the case where the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A. More specifically, the positive electrode current collector 21A includes an inner circumferential surface 21A1 of the positive electrode current collector facing the winding center side of the electrode winding body 20, i.e., the central axis CL, and an outer circumferential surface 21A2 of the positive electrode current collector facing the opposite side of the winding center side of the electrode winding body 20, i.e., the side opposite to the inner circumferential surface 21A1. The positive electrode 21 has a positive electrode active material layer 21B, which includes an inner circumferential active material layer 21B1 that covers at least a portion of the inner circumferential surface 21A1 of the positive electrode current collector, and an outer circumferential active material layer 21B2 that covers at least a portion of the outer circumferential surface 21A2 of the positive electrode current collector. In this specification, the inner circumferential active material layer 21B1 and the outer circumferential active material layer 21B2 may be referred to collectively as the positive electrode active material layer 21B without distinction.

[0033] The positive electrode 21 has a positive electrode covering portion 211 in which the positive electrode current collector 21A is covered with a positive electrode active material layer 21B, and a positive electrode exposed portion 212 in which the positive electrode current collector 21A is exposed without being covered by the positive electrode active material layer 21B. As shown in Figure 4A, the positive electrode covering portion 211 and the positive electrode exposed portion 212 each extend along the L-axis direction, which is the longitudinal direction of the positive electrode 21, from the inner circumference edge 21E1 to the outer circumference edge 21E2 of the electrode winding body 20. Here, the L-axis direction corresponds to the winding direction of the electrode winding body 20. That is, in the positive electrode 21, in the winding direction of the electrode winding body 20, the positive electrode current collector 21A is covered with the positive electrode active material layer 21B from the inner circumference edge 21E1 to the outer circumference edge 21E2 of the positive electrode 21. The positive electrode covering portion 211 and the positive electrode exposed portion 212 are adjacent to each other in the W-axis direction, which is the short-side direction of the positive electrode 21. The W-axis direction substantially coincides with the central axis CL. Furthermore, as shown in Figure 2, in the electrode winding body 20, the inner edge 21E1 of the innermost positive electrode portion 21in is set back inward from the inner edge 22E1 of the innermost negative electrode portion 22in.

[0034] Incidentally, Figures 4A and 4B schematically show the positive electrode current collector 21A extending linearly along the W-axis. However, in reality, the positive electrode edge portion 212E of the positive electrode exposed portion 212 is bent toward the central axis CL as shown in Figure 1 and connected to the positive electrode current collector plate 24. As shown in Figure 4C, each of the tips of the multiple overlapping positive electrode edge portions 212E includes a curved surface 21RS as a second curved surface. Figure 4C is an enlarged cross-sectional view showing an enlarged view of the positive electrode edge portion 212E of the positive electrode 21. The curved surface 21RS is, for example, a burr formed during shearing. The curved surface 21RS faces the positive electrode current collector plate 24. Furthermore, each of the tips of the multiple positive electrode edge portions 212E includes a projection 21PR as a second projection that protrudes on the opposite side from the positive electrode current collector plate 24. The projection 21PR is, for example, a burr formed during shearing. It is preferable that an insulating layer 101 be provided near the boundary between the positive electrode covering portion 211 and the positive electrode exposed portion 212. The insulating layer 101, like the positive electrode covering portion 211 and the positive electrode exposed portion 212, is preferable to extend from the inner circumference edge 21E1 to the outer circumference edge 21E2 of the electrode winding body 20. Furthermore, it is preferable that the insulating layer 101 be bonded to at least one of the first separator member 23A and the second separator member 23B. This is because it is possible to prevent misalignment between the positive electrode 21 and the separator 23. In addition, it is preferable that the insulating layer 101 contains a resin containing polyvinylidene fluoride (PVDF). This is because the insulating layer 101 contains PVDF, which allows it to swell due to the solvent contained in the electrolyte, for example, and adhere well to the separator 23. The detailed configuration of the positive electrode 21 will be described later.

[0035] Figure 5A is an unfolded view of the negative electrode 22, schematically representing its state before winding. Figure 5B shows the cross-sectional configuration of the negative electrode 22. Note that Figure 5B shows the cross-section in the direction of the arrow along the VB-VB line shown in Figure 5A. The negative electrode 22 includes, for example, a negative electrode current collector 22A and a negative electrode active material layer 22B provided on the negative electrode current collector 22A. The negative electrode active material layer 22B may be provided on, for example, only one side of the negative electrode current collector 22A, or on both sides of the negative electrode current collector 22A. Figure 5B shows the case where the negative electrode active material layer 22B is provided on both sides of the negative electrode current collector 22A. More specifically, the negative electrode current collector 22A includes an inner circumferential surface 22A1 of the negative electrode current collector facing the winding center side of the electrode winding body 20, i.e., the central axis CL, and an outer circumferential surface 22A2 of the negative electrode current collector facing the opposite side of the winding center side of the electrode winding body 20, i.e., the side opposite to the inner circumferential surface 22A1 of the negative electrode current collector. The negative electrode 22 has a negative electrode active material layer 22B, which includes an inner circumferential active material layer 22B1 that covers at least a portion of the inner circumferential surface 22A1 of the negative electrode current collector, and an outer circumferential active material layer 22B2 that covers at least a portion of the outer circumferential surface 22A2 of the negative electrode current collector. In this specification, the inner circumferential active material layer 22B1 and the outer circumferential active material layer 22B2 may be referred to collectively as the negative electrode active material layer 22B without distinction.

[0036] The negative electrode 22 has a negative electrode covering portion 221 in which a negative electrode active material layer 22B covers the negative electrode current collector 22A, and a negative electrode exposed portion 222 in which the negative electrode current collector 22A is exposed without being covered by the negative electrode active material layer 22B. As shown in Figure 5A, the negative electrode covering portion 221 and the negative electrode exposed portion 222 each extend along the L-axis direction, which is the longitudinal direction of the negative electrode 22. The negative electrode exposed portion 222 extends from the inner circumferential edge 22E1 to the outer circumferential edge 22E2 of the negative electrode 22 in the winding direction of the electrode winding body 20. In contrast, the negative electrode covering portion 221 is not provided at the inner circumferential edge 22E1 and the outer circumferential edge 22E2 of the negative electrode 22. As shown in Figure 5A, a part of the negative electrode exposed portion 222 is formed to sandwich the negative electrode covering portion 221 in the L-axis direction, which is the longitudinal direction of the negative electrode 22. Specifically, the negative electrode exposed portion 222 includes a first portion 222A, a second portion 222B, and a third portion 222C. The first portion 222A is provided adjacent to the negative electrode covering portion 221 in the W-axis direction and extends in the L-axis direction from the inner circumferential edge 22E1 to the outer circumferential edge 22E2 of the negative electrode 22. The second portion 222B and the third portion 222C are provided so as to sandwich the negative electrode covering portion 221 in the L-axis direction. The second portion 222B is located, for example, near the inner circumferential edge 22E1 of the negative electrode 22, and the third portion 222C is located near the outer circumferential edge 22E2 of the negative electrode 22. In Figures 5A and 5B, the negative electrode current collector 22A is schematically shown as extending linearly along the W-axis direction. However, in reality, the negative electrode edge portion 222E of the exposed negative electrode portion 222 is bent toward the central axis CL as shown in Figure 1 and connected to the negative electrode current collector plate 25. The detailed configuration of the negative electrode 22 will be described later.

[0037] 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 portion 212 and the first portion 222A of the negative electrode exposed portion 222 are oriented in opposite directions along the W axis, which is the width direction. 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.

[0038] In the secondary battery 1, as shown in Figure 2, when the width of the exposed positive electrode portion 212 is A and the width of the first portion 222A of the exposed negative electrode portion 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 exposed positive electrode portion 212 that protrudes from the outer edge of the separator 23 in the width direction is C, and the length of the first portion 222A of the exposed negative electrode portion 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).

[0039] As shown in Figure 1, at the upper part of the secondary battery 1, multiple positive electrode edges 212E of the electrode winding body 20, which are wound around the central axis CL and are adjacent in the radial direction (R direction), are bent toward the central axis CL so as to overlap each other, forming the upper end face 41 of the electrode winding body 20. Similarly, at the lower part of the secondary battery 1, multiple negative electrode edges 222E of the negative electrode exposed portion 222, which are wound around the central axis CL, are bent toward the central axis CL so as to overlap each other, forming the lower end face 42 of the electrode winding body 20. Therefore, multiple positive electrode edges 212E of the positive electrode exposed portion 212 are gathered at the upper end face 41 of the electrode winding body 20, and multiple negative electrode edges 222E of the negative electrode exposed portion 222 are gathered at the lower end face 42 of the electrode winding body 20. Multiple positive electrode edges 212E, which are bent toward the central axis CL, are flat surfaces in order to improve contact between the positive electrode current collector plate 24 for extracting current and the positive electrode edge 212E. Similarly, multiple negative electrode edges 222E, which are bent toward the central axis CL, are flat surfaces in order to improve contact between the negative electrode current collector plate 25 for extracting current and the negative electrode edge 222E. Note that the term "flat surface" here includes not only perfectly flat surfaces but also surfaces with some irregularities or surface roughness to the extent that the positive electrode exposed portion 212 and the negative electrode exposed portion 222 can be joined to the positive electrode current collector plate 24 and the negative electrode current collector plate 25, respectively.

[0040] As shown in Figure 5C, each of the tips of the multiple overlapping negative electrode edges 222E includes a curved surface 22RS as a first curved surface. Figure 5C is an enlarged cross-sectional view showing an enlarged view of the negative electrode edges 222E of the negative electrode 22. The curved surface 22RS is, for example, a sagging surface formed during shearing. The curved surface 22RS faces the negative electrode current collector plate 25. Furthermore, each of the tips of the multiple negative electrode edges 222E includes a projection 22PR as a first projection that protrudes on the side opposite to the negative electrode current collector plate 25. The projection 22PR is, for example, a burr formed during shearing.

[0041] 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 portion 212 is lower than that of the negative electrode exposed portion 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 portion 212 and the negative electrode exposed portion 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 positive electrode edges 212E (Figure 1) of the positive electrode exposed portion 212 are bent and overlap appropriately. Therefore, the positive electrode exposed portion 212 and the positive electrode current collector plate 24 can be easily joined. Similarly, the multiple negative electrode edges 222E (Figure 1) of the exposed negative electrode portion 222 are bent and overlap appropriately. This facilitates joining the exposed negative electrode portion 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.

[0042] As shown in Figure 2, the portion of the positive electrode exposed portion 212 of the positive electrode 21 that faces the negative electrode 22 across the separator 23 is covered by an insulating layer 101. The insulating layer 101 has a width of, for example, 3 mm in the W-axis direction. The insulating layer 101 covers the entire area of ​​the positive electrode exposed portion 212 of the positive electrode 21 that faces the negative electrode covering portion 221 of the negative electrode 22 via the separator 23. The insulating layer 101 can effectively prevent internal short circuits in the secondary battery 1 when, for example, foreign matter enters between the negative electrode covering portion 221 and the positive electrode exposed portion 212. Furthermore, the insulating layer 101 can absorb shocks when the secondary battery 1 is subjected to impact, effectively preventing bending of the positive electrode exposed portion 212 and short circuits between the positive electrode exposed portion 212 and the negative electrode 22.

[0043] (Insulating tape 53, 54) The secondary battery 1 may further have insulating tapes 53, 54 in the gap between the outer casing 11 and the electrode winding 20. The exposed positive electrode portion 212 and the exposed negative electrode portion 222, which are concentrated at the end faces 41, 42, are conductors such as exposed metal foil. Therefore, if the exposed positive electrode portion 212 and the exposed negative electrode portion 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 on the 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. 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.

[0044] (Positive electrode current collector plate 24 and negative electrode current collector plate 25) In a typical lithium-ion secondary battery, for example, leads for current extraction are welded to one point each on the positive and negative electrodes. However, this results in high internal resistance of the lithium-ion secondary battery, causing it to overheat and become hot during discharge, making it unsuitable for high-rate discharge. Therefore, in the secondary battery 1 of this embodiment, the positive electrode current collector plate 24 is positioned facing the end face 41, and the negative electrode current collector plate 25 is positioned facing the end face 42. The positive electrode edge 212E of the positive electrode exposed portion 212 on the end face 41 and the positive electrode current collector plate 24 are joined at multiple points, and the negative electrode edge 222E of the negative electrode exposed portion 222 on the end face 42 and the negative electrode current collector plate 25 are joined at multiple points. The joining of the positive electrode edge 212E to the positive electrode current collector plate 24 and the joining of the negative electrode edge 222E to the negative electrode current collector plate 25 is performed, for example, by laser welding. This reduces the internal resistance of the secondary battery 1. The fact that the end faces 41 and 42 are flat surfaces, as described above, also contributes to the reduction of resistance. 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 electrically connected to the outer casing 11, for example. Figure 6A is a schematic diagram showing one example of the configuration of the positive electrode current collector plate 24. Figure 6B is a schematic diagram showing one example of the 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 materials.

[0045] As shown in Figure 6A, the positive electrode current collector plate 24 has a shape in which a roughly rectangular strip-shaped portion 32 is connected to a roughly fan-shaped portion 31. A through hole 35 is formed near the center of the fan-shaped portion 31. In the secondary battery 1, the positive electrode current collector plate 24 is provided such that the through hole 35 overlaps with the through hole 26 in the Z-axis direction. The shaded portion in Figure 6A is the insulating portion 32A of the strip-shaped portion 32. The insulating portion 32A is a part of the strip-shaped portion 32 to which insulating tape is attached or insulating material is applied. The lower part of the strip-shaped portion 32 is the connection portion 32B to the sealing plate which also serves as an external terminal. Note that, as shown in Figure 1, if the secondary battery 1 has a battery structure in which a metal center pin is not provided in the through hole 26, the possibility of the strip-shaped portion 32 coming into contact with the negative electrode potential portion 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.

[0046] The shape of the negative electrode current collector plate 25 shown in Figure 6B is almost the same as the shape of the positive electrode current collector plate 24 shown in Figure 6A. However, the strip-shaped portion 34 of the negative electrode current collector plate 25 is different from the strip-shaped portion 32 of the positive electrode current collector plate 24. The strip-shaped portion 34 of the negative electrode current collector plate 25 is shorter than the strip-shaped portion 32 of the positive electrode current collector plate 24, and does not have a portion corresponding to the insulating portion 32A of the positive electrode current collector plate 24. The strip-shaped portion 34 is provided with multiple circular protrusions 37, indicated by the circles. During resistance welding, the current concentrates on the protrusions 37, causing the protrusions 37 to melt and the strip-shaped portion 34 to be welded to the bottom of the outer casing 11. Similar to the positive electrode current collector plate 24, the negative electrode current collector plate 25 has a through hole 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 through hole 36 overlaps with the through hole 26 in the Z-axis direction.

[0047] The fan-shaped portion 31 of the positive electrode current collector plate 24 covers only a portion of the 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 end face 42 due to its planar shape. There are two main reasons why the fan-shaped portions 31 and 33 do not cover the entire end faces 41 and 42. Firstly, to allow the electrolyte to penetrate smoothly into the electrode winding body 20 when assembling the secondary battery 1, for example. Secondly, to facilitate the release of gas generated when the lithium-ion secondary battery experiences abnormally high temperatures or overcharge conditions.

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

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

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

[0051] (Negative electrode active material layer 22B) The negative electrode active material layer 22B contains one or more negative electrode materials capable of intercalating and releasing lithium as the negative electrode active material. However, the negative electrode active material layer 22B may further contain one or more other materials such as a negative electrode binder and a negative electrode conductive agent. The negative electrode material is, for example, a carbon material. This is because a high energy density can be stably obtained because the change in crystal structure during intercalation and release of lithium is very small. In addition, since the carbon material also functions as a negative electrode conductive agent, the conductivity of the negative electrode active material layer 22B is improved. Examples of carbon materials include easily graphitizable carbon, poorly graphitizable carbon, and graphite. However, the interplanar spacing of the (002) planes in poorly graphitizable carbon is preferably 0.37 nm or more. The interplanar spacing of the (002) planes in graphite is preferably 0.34 nm or less. More specifically, carbon materials include, for example, 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.

[0052] Further, the negative electrode active material layer 22B may contain, as a negative electrode active material, a silicon-containing material containing at least one of silicon, silicon oxide, carbon-silicon compound, and silicon alloy. The silicon-containing material is a general term for materials containing silicon as a constituent element. However, the silicon-containing material may contain only silicon as a constituent element. Note that the type of the silicon-containing material may be only one type or two or more types. The silicon-containing material can form an alloy with lithium, and may be a simple substance of silicon, an alloy of silicon, a compound of silicon, a mixture of two or more of them, or a material containing one or two or more phases of them. Also, the silicon-containing material may be crystalline, amorphous, or may contain both a crystalline part and an amorphous part. However, since the simple substance described here means a general simple substance, it may contain trace amounts of impurities. That is, the purity of the simple substance is not necessarily limited to 100%. The alloy of silicon contains, for example, as a constituent element other than silicon, any one or two or more of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium. The compound of silicon contains, for example, as a constituent element other than silicon, any one or two or more of carbon and oxygen. 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 a constituent element other than silicon. Specifically, the alloy of silicon and the compound of silicon are, for example, SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, and SiO v (0 < v ≤ 2) and the like. However, the range of v can be arbitrarily set, for example, 0.2 < v < 1.4 may also be used.

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

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

[0055] (electrolyte) The electrolyte contains a solvent and an electrolyte salt. However, the electrolyte may further contain one or more other materials such as additives. The solvent contains one or more non-aqueous solvents such as organic solvents. An electrolyte containing a non-aqueous solvent is a so-called non-aqueous electrolyte. The non-aqueous solvent contains, for example, 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.

[0056] The electrolyte salt contains one or more types of salts, such as lithium salts. However, the electrolyte salt may also contain salts other than lithium salts. These salts other than lithium 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 (Li2SF6), 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 electrolyte salt content is not particularly limited, but is preferably 0.3 mol / kg to 3 mol / kg relative to the solvent. When the electrolyte contains LiPF6 as the electrolyte salt, the concentration of LiPF6 in the electrolyte should be 1.25 mol / kg or more and 1.45 mol / kg or less. This is because it prevents cycle degradation due to salt consumption (decomposition) during high-load rate charging, thereby improving high-load cycle characteristics. When the electrolyte further contains LiBF4 in addition to LiPF6 as the electrolyte salt, the concentration of LiBF4 in the electrolyte should be 0.001 (weight%) or more and 0.1 (weight%) or less. This is because it more effectively prevents cycle degradation due to salt consumption (decomposition) during high-load rate charging, thereby further improving high-load cycle characteristics.

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

[0058] [1-3. Manufacturing method] The manufacturing method of the secondary battery 1 will be explained with reference to Figures 1 to 5B, as well as Figures 7 to 9B. Figure 7 is a perspective view illustrating the manufacturing process of the secondary battery shown in Figure 1. Figures 8A and 8B are schematic diagrams illustrating the process of cutting out a positive electrode current collector 21A having a predetermined width by shearing. Figures 9A and 9B are schematic diagrams illustrating the process of cutting out a negative electrode current collector 22A having a predetermined width by shearing.

[0059] First, a positive electrode current collector 21A is prepared, and a positive electrode 21 having a positive electrode covering portion 211 and a positive electrode exposed portion 212 is formed by selectively forming a positive electrode active material layer 21B on the surface of the positive electrode current collector 21A. Furthermore, the positive electrode current collector 21A of the positive electrode exposed portion 212 is cut so that the width A of the positive electrode exposed portion 212 (see Figure 2) becomes a predetermined dimension. Specifically, as shown in Figure 8A, for example, the positive electrode current collector 21A is sheared by pressing the lower blade LB against the inner circumferential surface 21A1 of the positive electrode current collector and the upper blade UB against the outer circumferential surface 21A2 of the positive electrode current collector, and applying pressure in the directions indicated by the arrows using the lower blade LB and the upper blade UB. As a result, a cut surface extending in the L-axis direction is formed. This cut surface is the portion that becomes the multiple positive electrode edge portions 212E of the electrode winding body 20. As shown in Figure 8B, the positive electrode edge portion 212E includes a curved surface 21RS which is a sagging surface and a projection 21PR which is a burr.

[0060] Next, a negative electrode current collector 22A is prepared, and a negative electrode 22 having a negative electrode covering portion 221 and a negative electrode exposed portion 222 is formed by selectively forming a negative electrode active material layer 22B on the surface of the negative electrode current collector 22A. Furthermore, the negative electrode current collector 22A of the negative electrode exposed portion 222 is cut so that the width B (see Figure 2) of the first portion 222A of the negative electrode exposed portion 222 becomes a predetermined dimension. Specifically, as shown in Figure 9A, for example, the negative electrode current collector 22A is sheared by pressing the lower blade LB against the inner circumferential surface 22A1 of the negative electrode current collector and the upper blade UB against the outer circumferential surface 22A2 of the negative electrode current collector, and applying pressure in the directions indicated by the arrows using the lower blade LB and the upper blade UB. As a result, a cut surface extending in the L-axis direction is formed. This cut surface is the portion that becomes the multiple negative electrode edge portions 222E of the electrode winding body 20. As shown in Figure 9B, the negative electrode edge portion 222E includes a curved surface 22RS which is a sagging surface and a projection 22PR which is a burr.

[0061] The positive electrode 21 and negative electrode 22 prepared as described above may be subjected to a drying process. Next, the positive electrode 21 and negative electrode 22 are stacked via the first separator member 23A and the second separator member 23B so that the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 are on opposite sides in the W-axis direction, thereby creating a laminate S20. After that, the laminate S20 is wound in a spiral shape so that through holes 26 are formed. Furthermore, fixing tape 46 is attached to the outermost circumference of the spirally wound laminate S20. This gives the electrode winding body 20 as shown in Figure 7(A).

[0062] Next, as shown in Figure 7(B), by pressing the end of, for example, a 0.5 mm thick flat plate against the end faces 41 and 42 of the electrode winding body 20 perpendicularly, that is, in the Z-axis direction, the end face 4 Sections 1 and 42 are locally bent. As a result, grooves 43 are created that extend radially (in the R direction) from the through-hole 26. Note that the number and arrangement of grooves 43 shown in Figure 7(B) are illustrative examples and the present disclosure is not limited thereto.

[0063] Next, as shown in Figure 7(C), substantially the same pressure is applied substantially simultaneously and substantially the same from above and below the electrode winding body 20, in a direction substantially perpendicular to the end faces 41 and 42. At this time, a rod-shaped jig, for example, is inserted into the through hole 26. By doing so, the positive electrode exposed portion 212 and the negative electrode edge portion 222E of the negative electrode exposed portion 222 are bent, respectively, so that the end faces 41 and 42 become flat surfaces. At this time, the positive electrode edge portion 212E of the positive electrode exposed portion 212 and the negative electrode edge portion 222E of the negative electrode exposed portion 222 on the end faces 41 and 42 are bent while overlapping toward the through hole 26. After that, the fan-shaped portion 31 of the positive electrode current collector plate 24 is joined to the 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 end face 42 by laser welding or the like.

[0064] Next, insulating tapes 53 and 54 are attached to the predetermined positions on the electrode winding body 20. Then, as shown in Figure 7(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.

[0065] Next, the electrode winding body 20 assembled as described above is inserted into the outer casing 11 shown in Figure 7(E), and then the bottom of the outer casing 11 is welded to the negative electrode current collector plate 25. 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 is welded to the safety valve mechanism 30.

[0066] Next, as shown in Figure 7(F), the constricted portion 11S is used to seal the gasket 15, the safety valve mechanism 30, and the battery cover 14.

[0067] With the above steps, the secondary battery 1 of this embodiment is completed.

[0068] [1-4. Action and Effects] As described above, in the secondary battery 1 of this embodiment, multiple positive electrode edges 212E adjacent in the radial direction of the electrode winding body 20 in the positive electrode exposed portion 212 are bent toward the central axis CL so as to overlap each other, forming an end face 41. Furthermore, in the secondary battery 1 of this embodiment, multiple negative electrode edges 222E adjacent in the radial direction of the electrode winding body 20 in the negative electrode exposed portion 222 are bent toward the central axis CL so as to overlap each other, forming an end face 42. Here, each of the multiple positive electrode edges 212E includes a curved surface 21RS, and each of the multiple negative electrode edges 222E includes a curved surface 22RS. As a result, the contact area between the multiple positive electrode edges 212E of the positive electrode current collector 21A and the positive electrode current collector plate 24 is increased without distorting the shape of the electrode winding body 20, improving mutual adhesion and resulting in a good bonding state. Similarly, without the shape of the electrode winding 20 being distorted, the contact area between multiple negative electrode edges 222E of the negative electrode current collector 22A and the negative electrode current collector plate 25 increases, improving mutual adhesion and resulting in a good bonding state. Therefore, the internal resistance of the secondary battery 1 can be reduced, and a higher output can be obtained.

[0069] In contrast, if, for example, multiple positive electrode edges 212E each have sharp corners or protrusions facing the positive electrode current collector plate 24 without including a curved surface 21RS, or if multiple negative electrode edges 222E each have sharp corners or protrusions facing the positive electrode current collector plate 24 without including a curved surface 22RS, then the positive electrode edges 212E and the positive electrode current collector plate 24 will make point contact, or the negative electrode edges 222E and the negative electrode current collector plate 25 will make point contact. In such cases, the contact area between the positive electrode edges 212E and the positive electrode current collector plate 24 and the contact surface between the negative electrode edges 222E and the negative electrode current collector plate 25 will be affected. The products are all relatively smaller compared to this embodiment.

[0070] In this embodiment, the curved surface 21RS is positioned opposite the positive electrode current collector plate 24, and the curved surface 22RS is positioned opposite the negative electrode current collector plate 25. This increases the contact area between the positive electrode edge 212E and the positive electrode current collector plate 24, and between the negative electrode edge 222E and the negative electrode current collector plate 25, compared to the case where the curved surfaces 21RS and 22RS are absent, thereby ensuring a good contact state. As a result, the contact resistance at the interface between the positive electrode edge 212E and the positive electrode current collector plate 24, and the contact resistance at the interface between the negative electrode edge 222E and the negative electrode current collector plate 25 can be reduced.

[0071] Furthermore, in this embodiment, when manufacturing the electrode winding body 20, the projection 21PR faces away from the positive electrode current collector plate 24 and the projection 22PR faces away from the negative electrode current collector plate 25, that is, the projections 21PR and 22PR are oriented toward the central axis CL when the laminate is wound, and then the positive electrode edge 212E and the negative electrode edge 222E are bent. As a result, unintended wrinkles and folds are less likely to occur in the positive electrode edge 212E and the negative electrode edge 222E, and flat end faces 41 and 42 can be easily obtained.

[0072] If the electrode winding body 20 is manufactured such that the protrusions 21PR and 22PR face outward, unintended wrinkles and folds are likely to occur in the positive electrode edge 212E and negative electrode edge 222E when they are bent. As a result, it becomes difficult to secure a large contact area between the positive electrode edge 212E and the positive electrode current collector plate 24, and between the negative electrode edge 222E and the negative electrode current collector plate 25. Furthermore, if welding of the positive electrode edge 212E to the positive electrode current collector plate 24 and the negative electrode edge 222E to the negative electrode current collector plate 25 is performed by laser welding, there is a possibility that holes may be created in the positive electrode current collector plate 24 and the negative electrode current collector plate 25, reducing the contact area. Therefore, it is desirable that the projection 21PR faces away from the positive electrode current collector plate 24 and the projection 22PR faces away from the negative electrode current collector plate 25.

[0073] <2. Application Examples> The applications of the secondary battery 1 as one embodiment of the present disclosure described above are, for example, as follows.

[0074] [2-1. Battery Pack] Figure 10 is a block diagram showing an example of a circuit configuration when a battery according to one embodiment of the present invention (hereinafter appropriately referred to as a secondary battery) is applied to a battery pack 300. The battery pack 300 comprises a battery pack 301, an outer casing, a switch section 304 comprising a charge control switch 302a and a discharge control switch 303a, a current detection resistor 307, a temperature detection element 308, and a control unit 310.

[0075] 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.

[0076] The battery pack 301 is formed by connecting multiple secondary batteries 301a in series or parallel. The secondary battery 1 described above can be used as the secondary battery 301a. In Figure 10, 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).

[0077] The switch section 304 includes 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. The diode 302b controls the charging current flowing from the positive terminal 321 towards the battery pack 301. The polarity is reversed to the current flow and forward to the discharge current flowing from the negative terminal 322 towards the battery pack 301. The diode 303b has polarity that is forward to the charging current and reverse to the discharge current. In Figure 10, the switch 304 is provided on the + side, but it may also be provided on the - side.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] [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.

[0086] 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.

[0087] Electric vehicles include railway cars, golf carts, electric carts, and electric vehicles (including hybrid vehicles), and these are used as power sources or auxiliary power sources for their operation. Energy storage devices include power sources for buildings such as houses, or for storing electricity in power generation facilities. [Examples]

[0088] Examples of the present disclosure will be described below.

[0089] (Example 1) As described below, a cylindrical secondary battery 1, as shown in Figure 1, was fabricated, and its battery characteristics were evaluated. In this case, a lithium-ion secondary battery with dimensions of 21 mm in diameter and 70 mm in length was fabricated.

[0090] [Manufacturing method] First, a 12 μm thick aluminum foil was prepared as the positive electrode current collector 21A. Next, a positive electrode binder consisting of a layered lithium oxide with a Ni ratio of 85% or more of lithium nickel cobalt aluminum oxide (NCA) and polyvinylidene fluoride was prepared as the positive electrode active material, and a carbon A positive electrode mixture was obtained by mixing a conductive additive containing a mixture of black, acetylene black, and Ketjenblack. The mixing ratio of the positive electrode active material, positive electrode binder, and conductive additive was 96.4:2:1.6. Subsequently, the positive electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like positive electrode mixture slurry. Next, the positive electrode mixture slurry was applied to predetermined areas on both sides of the positive electrode current collector 21A using a coating apparatus, and the positive electrode mixture slurry was dried to form the positive electrode active material layer 21B. Furthermore, an insulating layer 101 with a width of 3 mm and a thickness of 8 μm was formed by applying a paint containing polyvinylidene fluoride (PVDF) to the surface of the positive electrode exposed portion 212 adjacent to the positive electrode covering portion 211 and drying it. Subsequently, the positive electrode active material layer 21B was compression molded using a roll press. This resulted in obtaining a positive electrode 21 having a positive electrode coating portion 211 and a positive electrode exposed portion 212. The positive electrode 21 was then sheared to a width of 60 mm in the W-axis direction of the positive electrode coating portion 211 and a width of 7 mm in the W-axis direction of the positive electrode exposed portion 212. The cross-section of the positive electrode edge portion 212E of the sheared positive electrode exposed portion 212 was observed using a Keyence VHX-6000 microscope at a magnification of approximately 500 to 2000 times, confirming the formation of a curved surface 21RS and a projection 21PR. The length of the positive electrode 21 in the L-axis direction was set to 1700 mm.

[0091] Furthermore, a copper foil with a thickness of 8 μm was prepared as the negative electrode current collector 22A. Next, a negative electrode mixture was obtained by mixing a negative electrode active material, which was a mixture of a carbon material consisting of graphite and SiO, a negative electrode binder consisting of polyvinylidene fluoride, and a conductive additive, which was a mixture of carbon black, acetylene black, and Ketjen black. The mixing ratio of the negative electrode active material, negative electrode binder, and conductive additive was set to 96.1:2.9:1.0. In addition, the mixing ratio of graphite and SiO in the negative electrode active material was set to 95:5. Subsequently, the negative electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry was applied to predetermined areas on both sides of the negative electrode current collector 22A using a coating apparatus, and then the negative electrode mixture slurry was dried to form the negative electrode active material layer 22B. Subsequently, the negative electrode active material layer 22B was compression molded using a roll press. This resulted in obtaining a negative electrode 22 having a negative electrode covering portion 221 and a negative electrode exposed portion 222. The negative electrode 22 was then sheared to a width of 62 mm in the W-axis direction of the negative electrode covering portion 221, and a width of 4 mm in the W-axis direction of the first portion 222A of the negative electrode exposed portion 222. The cross-section of the negative electrode edge portion 222E of the sheared negative electrode exposed portion 222 was observed using a Keyence VHX-6000 microscope at a magnification of approximately 500 to 2000 times, confirming the formation of a curved surface 22RS and a projection 22PR. The length of the negative electrode 22 in the L-axis direction was set to 1760 mm.

[0092] Next, a laminate S20 was fabricated by stacking the positive electrode 21 and the negative electrode 22 via a first separator member 23A and a second separator member 23B such that the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 were on opposite sides in the W-axis direction. At that time, the laminate S20 was fabricated so that the positive electrode active material layer 21B did not protrude from the negative electrode active material layer 22B in the W-axis direction. A polyethylene sheet having a width of 65 mm and a thickness of 14 μm was used as the first separator member 23A and the second separator member 23B. After that, the laminate S20 was wound in a spiral shape so that through holes 26 were formed and notches were positioned near the central axis CL, and fixing tape 46 was attached to the outermost circumference of the wound laminate S20. This obtained the electrode winding body 20.

[0093] Next, the end of a 0.5 mm thick flat plate was pressed against the end faces 41 and 42 of the electrode winding body 20 in the Z-axis direction, thereby locally bending the end faces 41 and 42 and creating grooves 43 that extend radially (R-direction) from the through hole 26.

[0094] Next, substantially the same pressure was applied substantially simultaneously and substantially perpendicular to the end faces 41 and 42 from above and below the electrode winding body 20, causing the first portion 222A of the positive electrode exposed portion 212 and the negative electrode exposed portion 222 to bend, making the end faces 41 and 42 flat surfaces. At this time, the positive electrode edge 212E of the positive electrode exposed portion 212 and the negative electrode edge 222E of the negative electrode exposed portion 222 on the end faces 41 and 42 were bent while overlapping toward the through hole 26. After that, the fan-shaped portion 31 of the positive electrode current collector plate 24 was joined to the end face 41 by laser welding, and the fan-shaped portion 33 of the negative electrode current collector plate 25 was joined to the end face 42 by laser welding.

[0095] Next, insulating tapes 53 and 54 were attached to the predetermined positions on the electrode winding body 20. Then, the strip portion 32 of the positive electrode current collector plate 24 was bent and inserted through the hole 12H of the insulating plate 12, and the strip portion 34 of the negative electrode current collector plate 25 was bent and inserted through the hole 13H of the insulating plate 13.

[0096] Next, the electrode winding body 20 assembled as described above was inserted into the outer casing 11, and then the bottom of the outer casing 11 and the negative electrode current collector plate 25 were welded together. After that, a constricted portion 11S was formed near the open end 11N of the outer casing 11. Furthermore, after the electrolyte was injected into the outer casing 11, The strip-shaped portion 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 were welded together.

[0097] As the electrolyte, a solvent was used which consisted of ethylene carbonate (EC) and dimethyl carbonate (DMC) as the main solvents, to which fluoroethylene carbonate (FEC) and succinonitrile (SN) were added, and which contained LiBF4 and LiPF6 as electrolyte salts. In the lithium-ion secondary battery of this example, the respective content (weight %) of EC, DMC, FEC, SN, LiBF4, and LiPF6 in the electrolyte was 12.7:56.2:12.0:1.0:1.0:17.1.

[0098] Finally, the constricted portion 11S was used to seal the gasket 15, the safety valve mechanism 30, and the battery cover 14.

[0099] Based on the above, a secondary battery as Example 1 was obtained.

[0100] (Comparative Example 1) A secondary battery of Comparative Example 1 was manufactured in the same manner as in Example 1, except that the projection 21PR was positioned opposite the positive electrode current collector plate 24 as shown in Figure 11A, and the projection 22PR was positioned opposite the negative electrode current collector plate 25 as shown in Figure 11B.

[0101] [Evaluation of battery characteristics] The DC resistance values ​​of the secondary batteries of Example 1 and Comparative Example 1, obtained as described above, were measured, and the results shown in Table 1 were obtained. Specifically, the DC resistance value was obtained by calculating the slope of the voltage when the discharge current was increased from 0[A] to 100[A] in 5 seconds. In Table 1, the DC resistance value of the secondary battery of Comparative Example 1 is set to 1, and the DC resistance value of Example 1 is shown as a relative value.

[0102] [Table 1]

[0103] As shown in Table 1, in Example 1, the DC resistance value was reduced by approximately 7% compared to Comparative Example 1. From this result, it was confirmed that the secondary battery of this disclosure improves the adhesion between the positive electrode 21 and the positive electrode current collector plate 24, and the adhesion between the negative electrode 22 and the negative electrode current collector plate 25, resulting in a good bonding state and a reduction in internal resistance.

[0104] The present disclosure has been described above with reference to one embodiment and one example, but the configuration of the present disclosure is not limited to the configuration described in one embodiment and one example, and can be modified in various ways. For example, in the above embodiment, a plurality of positive electrode edges 212E constituting the end face 41 each include a curved surface 21RS, and a plurality of negative electrode edges 222E constituting the end face 42 each include a curved surface 22RS, but the present disclosure is not limited thereto. The present disclosure may, for example, have only a plurality of positive electrode edges 212E each include a curved surface 21RS, or have a plurality of negative electrode edges 222E each include a curved surface 22RS. Furthermore, a subset of the plurality of positive electrode edges 212E may include a curved surface 21RS, or a subset of the plurality of negative electrode edges 222E may include a curved surface 22RS.

[0105] Furthermore, the secondary battery of this disclosure is not limited to the configurations shown in Figures 4A and 5A, respectively, for the positive and negative electrodes. For example, one or more slits may be provided in the positive electrode exposed portion 212 or the negative electrode exposed portion 222. Such slits may extend, for example, in the W-axis direction, or in a direction oblique to both the W-axis and L-axis directions.

[0106] Furthermore, although the above embodiment and examples described the case where the electrode reactant is lithium, the electrode reactant is not particularly limited. For this reason, the electrode reactant may be other alkali metals such as sodium and potassium, as described above, or alkaline earth metals such as beryllium, magnesium and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0107] The effects described herein are illustrative only, and the effects of this disclosure are not limited to those described herein. Therefore, other effects may be obtained with respect to this disclosure.

[0108] Furthermore, this disclosure may take the following forms: <1> A laminate in which a first electrode and a second electrode are stacked with a separator in between is wound around a central axis extending in a first direction, and the electrode winding body has a first end face and a second end face that face each other in the first direction, A first electrode current collector plate is connected to the first electrode while facing the first end face of the electrode winding body, A second electrode current collector plate, which is connected to the second electrode while facing the second end face of the electrode winding body, Equipped with, The first electrode has a first electrode covering portion in which the first electrode current collector is covered with a first electrode active material layer, and a first electrode exposed portion in which the first electrode current collector is exposed without being covered with the first electrode active material layer. The first electrode exposed portion is formed by bending a plurality of radially adjacent first edges of the electrode winding body toward the central axis so as to overlap each other, and each of the leading edges of the plurality of first edges includes a first curved surface. Secondary battery. <2> Each of the multiple first end portions includes a first projection that protrudes on the side opposite to the first electrode current collector plate. the above <1> The rechargeable battery described. <3> The second electrode has a second electrode covering portion in which the second electrode current collector is covered with a second electrode active material layer, and a second electrode exposed portion in which the second electrode current collector is exposed without being covered with the second electrode active material layer. Multiple second edges of the electrode winding body that are adjacent in the radial direction of the exposed second electrode are bent toward the central axis so as to overlap each other, forming the second end face, and each of the tips of the multiple second edges includes a second curved surface. the above <1> or <2> The rechargeable battery described. <4> The tips of the plurality of second edges include a second projection that protrudes on the side opposite to the second electrode current collector plate. the above <3> The rechargeable battery described. <5> The first electrode is the negative electrode, and the second electrode is the positive electrode. the above <1> from <4> A rechargeable battery as described in one of the following. <6> The second electrode has a second electrode covering portion in which the second electrode current collector is covered with a second electrode active material layer, and a second electrode exposed portion in which the second electrode current collector is exposed without being covered with the second electrode active material layer and is joined to the second electrode current collector plate. The first electrode current collector is made of copper foil or copper alloy foil, and the second electrode current collector is made of aluminum foil or aluminum alloy foil. the above <1> from <5> A rechargeable battery as described in one of the following. <7> The first electrode current collector plate and the first end face are joined by welding. the above <1> from <6> A rechargeable battery as described in one of the following. <8> The first electrode current collector plate comprises nickel, nickel alloy, copper, copper alloy, or a composite material thereof. The second electrode current collector plate includes aluminum or an aluminum alloy. the above <1> from <7> A rechargeable battery as described in one of the following. <9> The second electrode active material layer includes a negative electrode active material containing at least one of silicon, silicon oxide, silicon carbon compound, and silicon alloy. the above <6> The rechargeable battery described. <10> The first electrode active material layer includes a positive electrode active material containing at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. the above <5> The rechargeable battery described. <11> the above <1> from <10> A rechargeable battery as described in any one of the following, A control unit for controlling the secondary battery, The outer casing enclosing the aforementioned secondary battery and A battery pack that has [a certain feature]. <12> By selectively forming a first electrode active material layer on the first electrode current collector, a first electrode is fabricated in which a first electrode covering portion, where the first electrode active material layer covers the first electrode current collector, and a first electrode exposed portion, where the first electrode current collector is exposed without being covered by the first electrode active material layer, are provided adjacent to each other in a first direction, and the first electrode extends in a second direction perpendicular to the first direction. By cutting the first electrode current collector of the exposed first electrode portion along the second direction, a cut surface is created that includes the first curved surface and extends in the second direction, The second electrode is fabricated by selectively forming a second electrode active material layer on the second electrode current collector, After sequentially stacking the first electrode and the first separator and the second electrode and the second separator to create a laminate, an electrode winding body is produced by winding the laminate around a central axis extending in the first direction. By bending a plurality of first edges of the wound first electrode that are adjacent in the radial direction of the electrode winding body toward the central axis, a first end face is formed in which the plurality of first edges overlap each other, The first electrode current collector plate is joined to the first end face, The electrode winding body is joined to the second end face opposite to the first end face in the first direction and to the second electrode current collector plate. including A method for manufacturing secondary batteries.

Claims

1. A laminate in which a first electrode and a second electrode are stacked with a separator in between is wound around a central axis extending in a first direction, and the electrode winding body has a first end face and a second end face that face each other in the first direction, A first electrode current collector plate is connected to the first electrode while facing the first end face of the electrode winding body, A second electrode current collector plate, which is connected to the second electrode while facing the second end face of the electrode winding body, Equipped with, The first electrode has a first electrode covering portion in which the first electrode current collector is covered with a first electrode active material layer, and a first electrode exposed portion in which the first electrode current collector is exposed without being covered with the first electrode active material layer. Multiple first edges of the electrode winding body, which are adjacent in the radial direction of the exposed first electrode, are bent toward the central axis so as to overlap each other, forming the first end face, and each of the tips of the multiple first edges includes a first sagging surface that contacts the first electrode current collector plate and a first burr that protrudes toward the side opposite the first electrode current collector plate. Secondary battery.

2. The second electrode has a second electrode covering portion in which the second electrode current collector is covered with a second electrode active material layer, and a second electrode exposed portion in which the second electrode current collector is exposed without being covered by the second electrode active material layer. Multiple second edges of the electrode winding body, which are adjacent in the radial direction, are bent toward the central axis so as to overlap each other, forming the second end face, and each of the tips of the multiple second edges includes a second sagging surface facing the second electrode current collector plate. The secondary battery according to claim 1.

3. The tips of the plurality of second edges include a second burr that protrudes on the side opposite to the second electrode current collector plate. The secondary battery according to claim 2.

4. The first electrode is the negative electrode, and the second electrode is the positive electrode. A secondary battery according to any one of claims 1 to 3.

5. The second electrode has a second electrode covering portion in which the second electrode current collector is covered with a second electrode active material layer, and a second electrode exposed portion in which the second electrode current collector is exposed without being covered with the second electrode active material layer and is joined to the second electrode current collector plate. The first electrode current collector is made of copper foil or copper alloy foil, and the second electrode current collector is made of aluminum foil or aluminum alloy foil. A secondary battery according to any one of claims 1 to 3.

6. The first electrode current collector plate and the first end face are joined by welding. A secondary battery according to any one of claims 1 to 3.

7. The first electrode current collector plate comprises nickel, nickel alloy, copper, copper alloy, or a composite material thereof. The second electrode current collector plate includes aluminum or an aluminum alloy. A secondary battery according to any one of claims 1 to 3.

8. The first electrode active material layer includes a negative electrode active material containing at least one of silicon, silicon oxide, silicon carbon compound, and silicon alloy. The secondary battery according to claim 5.

9. The second electrode active material layer includes a positive electrode active material containing at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. The secondary battery according to claim 2.

10. A secondary battery according to any one of claims 1 to 3, 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].

11. By selectively forming a first electrode active material layer on the first electrode current collector, a first electrode is manufactured in which a first electrode covering portion, where the first electrode active material layer covers the first electrode current collector, and a first electrode exposed portion, where the first electrode current collector is exposed without being covered by the first electrode active material layer, are provided adjacent to each other in a first direction, and the first electrode extends in a second direction perpendicular to the first direction. By cutting the first electrode current collector of the exposed first electrode portion along the second direction, a cut surface is created that includes the first curved surface and extends in the second direction, The second electrode is fabricated by selectively forming a second electrode active material layer on the second electrode current collector, After sequentially stacking the first electrode and the first separator and the second electrode and the second separator to create a laminate, an electrode winding body is produced by winding the laminate around a central axis extending in the first direction. By bending a plurality of first edges of the wound first electrode that are adjacent in the radial direction of the electrode winding body toward the central axis, a first end face is formed in which the plurality of first edges overlap each other, The first electrode current collector plate is joined to the first end face, The electrode winding body is joined to the second end face opposite to the first end face in the first direction and to the second electrode current collector plate. Includes, The first end face is formed so as to include the first curved surface of each of the tip portions of the plurality of first edges. A method for manufacturing secondary batteries.

12. The first burr on one of the plurality of first edges is in contact with another first edge adjacent to that first edge. The secondary battery according to claim 11.

Images