SECONDARY BATTERY AND BATTERY PACK

Abstract

A secondary battery is provided that exhibits superior vibration resistance without compromising manufacturability. The secondary battery comprises an electrode coil and a battery housing. The electrode coil has a positive electrode and a negative electrode stacked on top of each other with a separator between them and wound around a central axis. The battery housing has a cylindrical outer shape, with one vertical direction corresponding to a direction along the central axis. The battery housing contains the electrode coil. The battery housing comprises a reservoir and a cover. The reservoir has a lower end and an upper end. The lower end is closed by a base. The upper end is positioned on one side opposite the lower end in the vertical direction and has an opening through which the electrode coil can pass.The cover part closes the opening of the container. If a flattening of the electrode winding body is a ratio of the maximum diameter of the electrode winding body to the minimum diameter of the electrode winding body, then the flattening of at least one section of an upper part of the electrode winding body is greater than the flattening of at least one section of a lower part of the electrode winding body.

Description

Technical field

[0001] The disclosure relates to a secondary battery and a battery pack that includes the secondary battery. Background technology

[0002] Various types of electronic devices, including mobile phones, are widespread. This widespread use has spurred the development of a secondary battery as an energy source, which is smaller in size and weight and offers a higher energy density. The secondary battery has a battery assembly contained within an outer casing element. Various configurations of the secondary battery have been considered (see, for example, PTL 1).

[0003] PTL 1 proposes a secondary battery that uses a so-called "tabless" structure to reduce internal resistance and enable charging and discharging with a relatively large current. List of patent literature

[0004] PTL 1: International Publication No. WO 2021 / 020235 Brief description of the invention

[0005] The performance improvement of a secondary battery has been examined in various ways. However, there is still room for improvement regarding the reliability of the secondary battery.

[0006] It is therefore desirable to provide a secondary battery that has superior vibration resistance and whose manufacturability is not impaired.

[0007] A secondary battery according to one embodiment of the disclosure comprises an electrode winding body and a battery housing. The electrode winding body has a positive electrode and a negative electrode stacked on top of each other with a separator between them and wound around a central axis. The battery housing has a substantially cylindrical outer shape, with one vertical direction corresponding to a direction along the central axis. The battery housing contains the electrode winding body. The battery housing comprises a container and a cover. The container has a lower end and an upper end. The lower end is closed by a bottom. The upper end is positioned on one side opposite the lower end in the vertical direction and has an opening through which the electrode winding body can pass. The cover closes the opening of the container.If a flattening of the electrode winding body is a ratio of a maximum diameter of the electrode winding body to a minimum diameter of the electrode winding body, then the flattening of an upper part of the electrode winding body is greater than the flattening of a lower part of the electrode winding body.

[0008] According to the secondary battery of one embodiment of the disclosure, the flattening of the upper part of the electrode winding body is greater than the flattening of the lower part of the electrode winding body. A relatively small flattening of the lower part of the electrode winding body facilitates insertion of the electrode winding body into the battery housing during assembly of the secondary battery. Furthermore, a large flattening of the upper part of the electrode winding body helps to prevent easy movement of the electrode winding body within the battery housing, even when the secondary battery is subjected to vibrations. This can, for example, prevent damage to the electrode winding body itself, as well as damage to a coupling element between a positive electrode current collector plate connected to the electrode winding body and an external terminal or a cover element.

[0009] The secondary battery according to one embodiment of the disclosure thus makes it possible to achieve superior vibration resistance without impairing manufacturability.

[0010] It should be noted that the effects of the revelation are not necessarily limited to those described above and may include any number of effects, which will be described below in connection with the revelation. Brief description of the drawings [ Fig. 1] Fig. Figure 1 is a sectional view illustrating a configuration of a secondary battery according to one embodiment of the disclosure. [ Fig. 2] Fig. Figure 2 is a schematic representation showing a configuration example of a stacked body including a positive electrode, a negative electrode, and a separator, as shown in Fig. 1 shown. [ Fig. 3] Fig.3 is a vertical section view, which is a configuration example of a vertical section structure of the in Fig. Figure 1 shows the electrode winding body. [ Fig. 4A] Fig. 4A is a flattened view of the in Fig. 1 positive electrode shown. [ Fig. 4B] Fig. 4B is a sectional view of the Fig. 1 positive electrode shown. [ Fig. 5A] Fig. 5A is a flattened view of the in Fig. 1 negative electrode shown. [ Fig. 5B] Fig. 5B is a sectional view of the Fig. 1 negative electrode shown. [ Fig. 6A] Fig. 6A is a top view of a Fig. 1. Positive electrode current collector plate shown. [ Fig. 6B] Fig. 6B is a top view of a Fig. 1. Negative electrode current collector plate shown. [ Fig. 7A] Fig. 7A is a horizontal sectional view that schematically depicts a horizontal sectional structure of an upper part of the in Fig. 1 illustrated electrode winding body. [ Fig. 7B] Fig. 7B is a horizontal sectional view that schematically depicts a horizontal sectional structure of a lower part of the in Fig. 1 illustrated electrode winding body. [ Fig. 8] Fig. 8 is a perspective view depicting a manufacturing process of the in Fig. 1 describes the secondary battery shown. [ Fig. 9] Fig. Figure 9 is a block diagram showing a circuit configuration of a battery pack in which the secondary battery is used according to an embodiment of the disclosure. Methods for carrying out the invention

[0011] Some embodiments of the disclosure are described in detail below with reference to the drawings. The description follows this order. 1. Secondary battery 1-1. Configuration 1-2. Operation 1-3. Manufacturing processes 1-4. Effects and impacts 2. Application examples 2-1. Battery pack 2-2. Electrical Power Storage System [1. Secondary battery]

[0012] First, a secondary battery according to one embodiment of the disclosure is described.

[0013] In the present embodiment, a cylindrical lithium-ion secondary battery with a cylindrical external appearance is described as an example. However, the secondary battery of the disclosure is not limited to the cylindrical lithium-ion secondary battery, but can also be a lithium-ion secondary battery with an external appearance in a shape other than cylindrical, or a battery in which an electrode reactant other than lithium is used.

[0014] Although the charging and discharging principle of a secondary battery is not particularly restricted, the following discussion focuses on a case where battery capacity is achieved through the storage and removal of the electrode reactant. The secondary battery comprises a positive electrode, a negative electrode, and an electrolyte. To prevent the electrode reactant from precipitating on the surface of the negative electrode during charging, the charging capacity of the negative electrode is greater than the discharging capacity of the positive electrode. In other words, the electrochemical capacity per unit area of ​​the negative electrode is set higher than the electrochemical capacity per unit area of ​​the positive electrode.

[0015] As described above, the type of electrode reactant is not particularly restricted, but it is primarily a light metal such as an alkali metal or an alkaline earth metal. Examples of alkali metals are lithium, sodium, and potassium. Examples of alkaline earth metals are beryllium, magnesium, and calcium.

[0016] The following example describes a case where the electrode reactant is lithium. A secondary battery in which the battery capacity is achieved by the storage and removal of lithium is called a lithium-ion secondary battery. In the lithium-ion secondary battery, lithium is stored and removed in an ionic state. [1-1. Configuration][Lithium-ion secondary battery 1]

[0017] Fig.Figure 1 illustrates a sectional configuration of a lithium-ion secondary battery 1 (hereinafter simply referred to as secondary battery 1) according to the present embodiment along a vertical direction. The in Fig. The secondary battery 1 shown in Figure 1 comprises an outer casing 11 and an electrode winding body 20. The outer casing 11 serves as the battery housing and has a cylindrical outer shape. The electrode winding body 20 serves as the battery assembly and is contained within the outer casing 11. The term "cylindrical" as used in this disclosure is not limited to a shape in which a cross-section perpendicular to the vertical direction is circular, but also includes a shape in which a cross-section perpendicular to the vertical direction is elliptical. The secondary battery 1 further comprises an outer casing tube 50 that covers an outer circumferential surface of the outer casing 11.

[0018] Specifically, the secondary battery 1, for example, comprises within the outer casing 11 a pair of insulating plates 12 and 13, the electrode winding body 20, a positive electrode current collector plate 24, and a negative electrode current collector plate 25. The electrode winding body 20 is, for example, a structure in which a positive electrode 21 and a negative electrode 22 are stacked and wound with a separator 23 positioned between them. The electrode winding body 20 is impregnated with an electrolyte solution. The electrolyte solution is a liquid electrolyte. It should be noted that the secondary battery 1 may further comprise a heat-sensitive resistor (PTC), a gain element, or both within the outer casing 11. [Outdoor housing box 11]

[0019] The outer housing 11, for example, has a hollow cylindrical structure with a lower end and an upper end in the Z-axis direction. The Z-axis direction is the vertical direction. The lower end is closed, and the upper end is open. Accordingly, the upper end of the outer housing 11 is an open end 11N, and the lower end of the outer housing 11 is closed by a bottom part 11B with a substantially disc-shaped form. A side wall part 11W is provided between the open end 11N and the bottom part 11B, which surrounds the electrode winding body 20. The outer housing 11, for example, has a metallic material such as iron as a component. It should be noted that a surface of the outer housing 11 may, for example, be plated with a metallic material such as nickel.Insulating plates 12 and 13 are arranged opposite each other, for example, so that the electrode winding body 20 is positioned between them in the Z-axis direction. It should be noted that, for the purposes of this description, the open end section 11N and its surroundings can be referred to as the upper part of the secondary battery 1 in the Z-axis direction, and the area where the outer housing 11 is closed, as well as its surroundings, can be referred to as the lower part of the secondary battery 1 in the Z-axis direction. The open end section 11N of the outer housing 11 is closed by a battery cover 14. The battery cover 14 will be described later. [Outer casing tube 50]

[0020] The outer casing tube 50 surrounds a side surface 11WS1, which is an outer surface of the side wall part 11W of the outer casing box 11. However, the outer casing tube 50 can also cover a bent part 11P provided at the upper end part of the outer casing box 11, as shown in Fig. Figure 1 shows the bent section 11P, which is described later. Furthermore, the outer casing tube 50 can cover a section of a base surface 11BS, which is an outer surface of the base part 11B of the outer casing box 11. The outer casing tube 50 has, for example, a heat-shrinkable insulating film containing a material such as a polyester resin, a polyamide resin, or a thermoplastic elastomer resin. [Washer 55]

[0021] A washer 55 is provided in a gap between the outer casing tube 50 and the bent part 11P of the outer casing box 11. The washer 55 is an annular insulating element having an opening 55K in a central region in a plane perpendicular to the vertical direction. A projecting part 14T is arranged in the opening 55K, which is provided in a central region of the battery cover 14. The washer 55 can, for example, contain modified polyphenylene ether in black as a component. [Insulating panels 12 and 13]

[0022] Each of the insulating plates 12 and 13, for example, is a bowl-shaped plate with a surface perpendicular to a central axis CL of the electrode winding body 20, i.e., a surface perpendicular to the Z-axis in Fig. 1. The insulating plates 12 and 13 are arranged such that the electrode winding body 20 is positioned between them. [Crimp structure 11R]

[0023] For example, a structure in which the battery cover 14 and a safety valve mechanism 30 are crimped with an intermediate seal 15, i.e., a crimp structure 11R, is provided on the open end part 11N of the outer housing 11. The outer housing 11 is closed by the battery cover 14, with the electrode winding body 20 and other components contained inside the outer housing 11. The crimp structure 11R is a so-called crimp structure and has the bent part 11P, which serves as the crimp part. [Battery cover 14]

[0024] The battery cover 14 is a closure element that primarily closes the open end 11N of the outer housing 11 in a state where the electrode winding body 20 and other components are contained within the outer housing 11. The battery cover 14 is made of a similar material to that of the outer housing 11. A projection 14T is provided in a central area of ​​the battery cover 14, extending upwards, i.e., in the +Z direction. This means that an edge area, i.e., an area outside the central area, of the battery cover 14 is in contact with, for example, the safety valve mechanism 30. [Seal 15]

[0025] The seal 15 is a sealing element primarily located between the bent section 11P of the outer housing junction box 11 and the battery cover 14. The seal 15 seals a gap between the bent section 11P and the battery cover 14. It should be noted that one surface of the seal 15 may be coated with asphalt, for example. The seal 15 may, for example, have one or more insulating materials. The type of insulating material is not particularly restricted, and examples include a polymer material such as polybutylene terephthalate (PBT) or polypropylene (PP). In particular, polybutylene terephthalate is preferred as the insulating material. One reason for this is that it allows the gap between the bent section 11P and the battery cover 14 to be adequately sealed, while electrically isolating the outer housing junction box 11 and the battery cover 14. [Safety valve mechanism 30]

[0026] The safety valve mechanism 30 is designed to release the sealed state of the outer casing 11, thereby releasing internal pressure within the outer casing 11 as needed, particularly in the event of an increase in internal pressure. Examples of causes for a pressure increase in the outer casing 11 include gas generated as a result of a decomposition reaction of the electrolyte solution during charging and discharging. The internal pressure of the outer casing 11 can also increase due to external heating. [Electrode winding body 20]

[0027] The electrode winding body 20 is a power generation device that performs charging and discharging reactions and is contained inside the outer housing 11. The electrode winding body 20 comprises the positive electrode 21, the negative electrode 22, the separator 23, and the electrolyte solution as a liquid electrolyte.

[0028] Fig.Figure 2 is an unfolded view of the electrode winding body 20 and schematically illustrates a section of a stacked body S20 comprising the positive electrode 21, the negative electrode 22, and the separator 23. In the stacked body S20, which corresponds to the electrode winding body 20 in its unwound state, the positive electrode 21 and the negative electrode are stacked on top of each other with the separator 23 positioned between them. The separator 23 has, for example, two base layers, namely a first separator element 23A and a second separator element 23B. Accordingly, the electrode winding body 20 comprises the four-layered stacked body S20. In the four-layered stacked body S20, the positive electrode 21, the first separator element 23A, the negative electrode 22, and the second separator element 23B are stacked in that order.Each of the positive electrode 21, the first separator element 23A, the negative electrode 22 and the second separator element 23B is an essentially ribbon-shaped element in which a W-axis direction corresponds to a transverse direction and an L-axis direction to a longitudinal direction.

[0029] As in Fig. As shown in Figure 3, the electrode winding body 20 can be wound around a central axis CL extending in the Z-axis direction such that a spiral shape results in a cross-section perpendicular to the Z-axis direction. Here, the stack body S20 is wound in an orientation in which the W-axis direction essentially coincides with the Z-axis direction. It should be noted that Fig. Figure 3 shows a configuration example of the electrode winding body 20 in a horizontal cross-section perpendicular to the Z-axis direction. For better visibility, the separator 23 is shown in Fig.Figure 3 is not shown. The electrode winding body 20 has an overall external appearance of an essentially cylindrical shape. The positive electrode 21 and the negative electrode are wound while maintaining their opposite orientation with a separator 23 positioned between them. The electrode winding body 20 has a through-hole 26 in its center, forming an internal space. The through-hole 26 is a hole into which a winding core for assembling the electrode winding body and an electrode rod for welding are inserted.

[0030] The positive electrode 21, the negative electrode 22, and the separator 23 are wound such that the separator 23 is located in both an outermost and an innermost winding of the electrode coil body 20. Furthermore, in the outermost winding of the electrode coil body 20, the negative electrode 22 is arranged on an outer side relative to the positive electrode 21. In other words, as in Fig.Figure 3 shows an outermost positive electrode winding section 21out, located in the outermost winding of the positive electrode 21 of the electrode winding body 20, arranged on an inner side relative to an outermost negative electrode winding section 22out, located in the outermost winding of the negative electrode 22 of the electrode winding body 20. Here, the outermost positive electrode winding section 21out is a section corresponding to the outermost winding of the positive electrode 21 in the electrode winding body 20. The outermost negative electrode winding section 22out is a section corresponding to the outermost winding of the negative electrode 22 in the electrode winding body 20. In contrast, in the innermost winding of the electrode winding body 20, the negative electrode 22 is arranged on the inner side relative to the positive electrode 21. In other words, as shown in Figure 3, the outermost positive electrode winding section 21out is located in the outermost winding of the electrode winding body 20. Fig.Figure 3 shows an innermost negative electrode winding section 22in, located in the innermost winding of the negative electrode 22 of the electrode coil body 20, arranged on the inside relative to an innermost positive electrode winding section 21in, located in the innermost winding of the positive electrode 21 of the electrode coil body 20. Here, the innermost positive electrode winding section 21in corresponds to the innermost winding of the positive electrode 21 in the electrode coil body 20. The innermost negative electrode winding section 22in corresponds to the innermost winding of the negative electrode 22 in the electrode coil body 20. The number of windings of the respective positive electrode 21, negative electrode 22, and separator 23 is not particularly restricted and can be chosen as desired.

[0031] Fig.Figure 4A is an unwound view of the positive electrode 21 and schematically illustrates a state before winding. Fig. Figure 4B shows a cross-sectional view of the positive electrode 21. It should be noted that Fig. 4B a section of the positive electrode 21 in the direction of the arrow along the in Fig. The line IVB-IVB shown in Figure 4A illustrates this. The positive electrode 21, for example, has a positive electrode current collector 21A and a positive electrode active material layer 21B provided on the positive electrode current collector 21A. For example, the positive electrode active material layer 21B can be provided on only one of the two opposing surfaces of the positive electrode current collector 21A or on both opposing surfaces. Fig.Figure 4B shows a case in which the positive electrode active material layer 21B is provided on both opposite surfaces of the positive electrode current collector 21A. More precisely, the positive electrode current collector 21A has an inwardly facing positive electrode current collector surface 21A1, which is directed towards a winding central side of the electrode winding body 20, i.e., towards the central axis CL, and an outwardly facing positive electrode current collector surface 21A2, which is located on one side opposite the winding central side of the electrode winding body 20, i.e., opposite the inwardly facing surface 21A1.The positive electrode 21 comprises, as positive electrode active material layers 21B, a positive electrode active material layer 21B1 located on the inside of the winding, which completely or partially covers the inwardly facing positive electrode current collector surface 21A1, and a positive electrode active material layer 21B2 located on the outside of the winding, which completely or partially covers the outwardly facing positive electrode current collector surface 21A2. It should be noted that, within the scope of this description, the positive electrode active material layer 21B1 located on the inside of the winding and the positive electrode active material layer 21B2 located on the outside of the winding can be referred to collectively as positive electrode active material layer 21B, without distinguishing between them.

[0032] The positive electrode 21 has a positive electrode cover region 211 in which the positive electrode current collector 21A is covered with the positive electrode active material layer 21B, and a positive electrode exposure region 212 in which the positive electrode current collector 21A is exposed without being covered with the positive electrode active material layer 21B. As shown in Fig.As shown in Figure 4A, the positive electrode cover area 211 and the positive electrode exposure area 212 each extend from a central winding edge 21E1 of the positive electrode 21 to an outer winding edge 21E2 of the positive electrode 21 along the L-axis direction, i.e., the longitudinal direction of the positive electrode 21. Here, the L-axis direction corresponds to the winding direction of the electrode core 20. In other words, in the positive electrode 21, the positive electrode current collector 21A is covered with the positive electrode active material layer 21B from the central winding edge 21E1 to the outer winding edge 21E2 in the winding direction of the electrode core 20. The positive electrode cover area 211 and the positive electrode exposure area 212 border each other in the W-axis direction, i.e., the transverse direction of the positive electrode 21. The W-axis direction essentially coincides with the central axis CL. Furthermore, as in Fig. Figure 2 shows that in the electrode winding body 20, the central winding side edge 21E1 of the innermost positive electrode winding section 21in is arranged offset inwards relative to the central winding side edge 22E1 of the innermost negative electrode winding section 22in. The positive electrode 21 also has a lower edge 21E3 that extends in the L-axis direction on a lower side of the electrode winding body 20.

[0033] An insulating layer 101 is preferably provided in a region that includes a boundary between the positive electrode cover region 211 and the positive electrode exposure region 212, as well as its surroundings. Like the positive electrode cover region 211 and the positive electrode exposure region 212, the insulating layer 101 preferably extends from the central winding side edge 21E1 to the outer winding side edge 21E2 in the electrode winding body 20. Furthermore, the insulating layer 101 preferably adheres to the first separator element 23A, the second separator element 23B, or both. One reason for this is to prevent the positive electrode 21 and the separator 23 from slipping relative to each other. The insulating layer 101 preferably comprises a resin containing polyvinylidene fluoride (PVDF).One reason for this is that the insulating layer 101, if it contains PVDF, swells due to, for example, a solvent present in the electrolyte solution, which allows the insulating layer 101 to adhere well to the separator 23. A detailed configuration of the positive electrode 21 will be described later.

[0034] Fig. Figure 5A is an unwound view of the negative electrode 22 and schematically illustrates a state before winding. Fig. Figure 5B shows a cross-sectional view of the negative electrode 22. It should be noted that Fig. 5B a section of the negative electrode 22 in the direction of the arrow along the in Fig.The line VB-VB shown in Figure 5A is shown. The negative electrode 22, for example, has 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 can, for example, be provided on only one of the two opposite surfaces of the negative electrode current collector 22A or on both opposite surfaces. Fig.Figure 5B shows a case in which the negative electrode active material layer 22B is provided on both opposite surfaces of the negative electrode current collector 22A. More precisely, the negative electrode current collector 22A has an inwardly facing negative electrode current collector surface 22A1, which is directed towards the central winding side of the electrode winding body 20, i.e., towards the central axis CL, and an outwardly facing negative electrode current collector surface 22A2, which is located on one side opposite the central winding side of the electrode winding body 20, i.e., opposite the inwardly facing surface 22A1.The negative electrode 22 comprises, as negative electrode active material layers 22B, a negative electrode active material layer 22B1 located on the inside of the winding, which covers all or part of the inwardly facing negative electrode current collector surface 22A1, and a negative electrode active material layer 22B2 located on the outside of the winding, which covers all or part of the outwardly facing negative electrode current collector surface 22A2. It should be noted that, within the scope of this description, the negative electrode active material layer 22B1 located on the inside of the winding and the negative electrode active material layer 22B2 located on the outside of the winding can be referred to collectively as negative electrode active material layer 22B, without distinguishing between them.

[0035] The negative electrode 22 has a negative electrode cover area 221 in which the negative electrode current collector 22A is covered with the negative electrode active material layer 22B, and a negative electrode exposure area 222 in which the negative electrode current collector 22A is exposed without being covered with the negative electrode active material layer 22B. As shown in Fig.As shown in Figure 5A, the negative electrode cover area 221 and the negative electrode exposure area 222 each extend along the L-axis direction, i.e., the longitudinal direction of the negative electrode 22. The negative electrode exposure area 222 extends from the central winding edge 22E1 of the negative electrode 22 to the outer winding edge 22E2 of the negative electrode 22 in the winding direction of the electrode core 20. In contrast, the negative electrode cover area 221 is not provided at either the central winding edge 22E1 or the outer winding edge 22E2 of the negative electrode 22. As shown in Fig.As shown in Figure 5A, sections of the negative electrode exposure area 222 are arranged such that the negative electrode cover area 221 is positioned between them in the L-axis direction, i.e., in the longitudinal direction of the negative electrode 22. Specifically, the negative electrode exposure area 222 has a first section 222A, a second section 222B, and a third section 222C. The negative electrode 22 also has a lower edge 22E3 that extends in the L-axis direction along the underside of the electrode winding body 20. The first section 222A is located adjacent to the negative electrode cover area 221 in the W-axis direction and extends from the central winding side edge 22E1 to the outer winding side edge 22E2 of the negative electrode 22 in the L-axis direction. Sections 222B and 222C are arranged such that the negative electrode cover area 221 lies between them in the L-axis direction.The first section 222A is located in a region including the lower edge 22E3 of the negative electrode 22 and its surroundings. The second section 222B, for example, is located in a region including the central winding side edge 22E1 of the negative electrode 22 and its surroundings. The third section 222C is located in a region including the outer winding side edge 22E2 of the negative electrode 22 and its surroundings. It should be noted that... Fig. 5A and Fig. Figure 5B schematically shows the negative electrode current collector 22A in a state where it is straightened along the W-axis direction. In reality, however, as shown in Fig. Figure 1 shows the negative electrode edge sections 222E of the negative electrode exposure area 222 bent towards the central axis CL and connected to the negative electrode current collector plate 25. A detailed configuration of the negative electrode 22 is described later.

[0036] In the stacking body S20 of the electrode winding body 20, the positive electrode 21 and the negative electrode 22 with the separator 23 arranged between them are stacked such that the positive electrode exposure area 212 and the first section 222A of the negative electrode exposure area 222 face opposite directions along the W-axis direction, i.e., a width direction. In the electrode winding body 20, an end section of the separator 23 is fixed by attaching a fastening band 46 to a side surface section 45 of the electrode winding body 20, thus preventing the winding from loosening.

[0037] In secondary battery 1, as in Fig.Figure 2 is shown, preferably A > B is satisfied, where A is a width of the positive electrode exposure area 212 and B is a width of the first section 222A of the negative electrode exposure area 222. For example, if the width A is 7 mm, the width B is 4 mm. Furthermore, preferably C > D is satisfied, where C is a width of a section of the positive electrode exposure area 212 projecting from an outer edge in the width direction of the separator 23, and D is a projection length of the first section 222A of the negative electrode exposure area 222 from an opposite outer edge in the width direction of the separator 23. For example, if the width C is 4.5 mm, the width D is 3 mm.

[0038] As in Fig.As shown in Figure 1, in the upper part of the secondary battery 1, several positive electrode edge sections 212E of the positive electrode exposure area 212 wound around the central axis CL, which adjoin each other in a radial direction (R-direction) of the electrode winding body 20, are bent towards the central axis CL and overlap each other, so that an upper end surface 41 of the electrode winding body 20 is formed. Similarly, in the lower part of the secondary battery 1, several negative electrode edge sections 222E of the negative electrode exposure area 222 wound around the central axis CL, which adjoin each other in the radial direction (R-direction), are bent towards the central axis CL and overlap each other, so that a lower end surface 42 of the electrode winding body 20 is formed.Accordingly, the multiple positive electrode edge sections 212E of the positive electrode exposure area 212 converge at the upper end face 41 of the electrode winding body 20, and the multiple negative electrode edge sections 222E of the negative electrode exposure area 222 converge at the lower end face 42 of the electrode winding body 20. To achieve better contact between the positive electrode current collector plate 24, which is intended for current collection, and the multiple positive electrode edge sections 212E, the multiple positive electrode edge sections 212E are bent towards the central axis CL and form a flat surface. Likewise, the multiple negative electrode edge sections 222E are bent towards the central axis CL and form a flat surface to enable better contact with the negative electrode current collector plate 25, which is intended for current collection.It should be noted that the term "flat surface" in the context of this description includes not only a completely flat surface, but also a surface with certain unevenness or surface roughness, insofar as it is possible to connect the positive electrode exposure area 212 with the positive electrode current collector plate 24 and to connect the negative electrode exposure area 222 with the negative electrode current collector plate 25.

[0039] The positive electrode current collector 21A, for example, has an aluminum foil, as will be described later. In contrast, the negative electrode current collector 22A, for example, has a 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. In other words, the positive electrode exposure area 212 has a lower modulus of elasticity than the negative electrode exposure area 222. Accordingly, in one embodiment, it is particularly preferred that the widths A to D satisfy a relationship A > B and C > D.In such a case, if the positive electrode exposure area 212 and the negative electrode exposure area 222 are bent simultaneously with equal pressure from their respective electrode sides, the bending areas in the positive electrode 21 and in the negative electrode 22 can have approximately the same heights relative to the respective ends of the separator 23. In this case, the multiple positive electrode edge sections 212E ( ) overlap. Fig. 1) of the positive electrode exposure area 212 by bending in a suitable manner. This allows for easy connection of the positive electrode exposure area 212 to the positive electrode current collector plate 24. Accordingly, the several negative electrode edge sections 222E overlap ( Fig.1) of the negative electrode exposure area 222 by bending in a suitable manner, thereby enabling easy connection of the negative electrode exposure area 222 to the negative electrode current collector plate 25. The term "connection" in the sense of this description refers, for example, to coupling by means of laser welding; however, the method of connection is not limited to laser welding.

[0040] As in Fig.As shown in Figure 2, a section of the positive electrode exposure area 212 of the positive electrode 21, facing the negative electrode 22 with the separator 23 arranged between them, is covered with the insulating layer 101. The insulating layer 101 has, for example, a width of 3 mm in the W-axis direction. The insulating layer 101 completely covers the section of the positive electrode exposure area 212 of the positive electrode 21 that faces the negative electrode cover area 221 of the negative electrode 22 with the separator 23 in between. The insulating layer 101 effectively prevents an internal short circuit of the secondary battery 1 if, for example, foreign matter gets between the negative electrode cover area 221 and the positive electrode exposure area 212.Furthermore, in the event of an impact on the secondary battery 1, the insulating layer 101 absorbs the impact and thus effectively prevents bending of the positive electrode exposure area 212 as well as a short circuit between the positive electrode exposure area 212 and the negative electrode 22. [Insulating tapes 53 and 54]

[0041] The secondary battery 1 may further comprise insulating tapes 53 and 54 in a gap between the outer housing 11 and the electrode winding body 20. The positive electrode exposure area 212, where the sections converge at the upper end face 41, and the negative electrode exposure area 222, where the sections converge at the lower end face 42, are exposed electrical conductors, such as metal foils. Therefore, if the positive electrode exposure area 212 and the negative electrode exposure area 222 are located near the outer housing 11, a short circuit between the positive electrode 21 and the negative electrode 22 can occur via the outer housing 11. A short circuit can also occur if the positive electrode current collector plate 24 at the upper end face 41 and the outer housing 11 approach each other. Therefore, the insulating tapes 53 and 54 are preferably provided as insulating elements.Each of the insulating tapes 53 and 54, for example, is an adhesive tape comprising a base layer and an adhesive layer provided on a surface of the base layer. The base layer consists, for example, of one of the following materials: polypropylene, polyethylene terephthalate, or polyimide. To prevent the capacitance of the electrode winding body 20 from being reduced by the application of the insulating tapes 53 and 54, the insulating tapes 53 and 54 are arranged so that they do not overlap with the fastening tape 46 attached to the side surface section 45, and the thickness of each of the insulating tapes 53 and 54 is set to a value less than or equal to the thickness of the fastening tape 46. [Positive electrode current collector plate 24 and negative electrode current collector plate 25]

[0042] In a typical lithium-ion secondary battery, for example, a current-discharge tab is welded to both the positive and negative electrodes at one point. However, such a structure increases the internal resistance of the lithium-ion secondary battery and causes it to heat up during discharge; therefore, this structure is unsuitable for high-current discharge. To counteract this, in the secondary battery 1 according to the present embodiment, the positive electrode current collector plate 24 is arranged so that it faces the upper end face 41, and the negative electrode current collector plate 25 is arranged so that it faces the lower end face 42.Furthermore, the positive electrode cover area 211 located on the upper end face 41 and the positive electrode current collector plate 24 are welded together at several points, and the negative electrode cover area 221 located on the lower end face 42 and the negative electrode current collector plate 25 are also welded together at several points. This results in a reduced internal resistance of the secondary battery 1. Each of the upper end faces 41 and the lower end face 42 is, as described above, a flat surface, which also contributes to the reduction in resistance. The positive electrode current collector plate 24 is, for example, electrically connected to the battery cover 14 via the safety valve mechanism 30. The negative electrode current collector plate 25 is, for example, electrically connected to the outer casing junction box 11. Fig.Figure 6A is a schematic representation of a configuration example of the positive electrode current collector plate 24. Fig. Figure 6B is a schematic representation of a configuration example of the negative electrode current collector plate 25. The positive electrode current collector plate 24 is a metal plate comprising, for example, aluminum or an aluminum alloy as a single component or a composite material of aluminum and an aluminum alloy. The negative electrode current collector plate 25 is a metal plate comprising, for example, nickel, a nickel alloy, copper, or a copper alloy as a single component or a composite material of two or more of these materials.

[0043] As in Fig.As shown in Figure 6A, the positive electrode current collector plate 24 has a shape in which a ribbon-shaped section 32, having a substantially rectangular shape, is connected to a fan-shaped section 31, also having a substantially fan-shaped shape. The fan-shaped section 31 has a through-hole 35 near a central region. In the secondary battery 1, the positive electrode current collector plate 24 is arranged such that the through-hole 35 overlaps the through-hole 26 in the Z-axis direction. The hatched area in Fig.6A represents an insulating section 32A of the ribbon-shaped section 32. The insulating section 32A is a section of the ribbon-shaped section 32 and has an insulating tape or applied insulating material attached to it. A section of the ribbon-shaped section 32 below the insulating section 32A is a coupling section 32B, which is connected to a sealing plate that also serves as an external connection. It should be noted that in a battery design of the secondary battery 1 without a metallic center pin in the through-hole 26, as in Fig.As shown in Figure 1, the probability of the ribbon-shaped section 32 coming into contact with an area at a negative electrode potential is low. In such a case, the positive electrode current collector plate 24 need not have the insulating section 32A. If the positive electrode current collector plate 24 does not have the insulating section 32A, it is possible to increase the width of the positive electrode 21 and the negative electrode 22 each by an amount corresponding to the thickness of the insulating section 32A, thereby increasing the charging and discharging capacity.

[0044] The in Fig. The negative electrode current collector plate 25 shown in Figure 6B has a similar shape to the one in Figure 6B. Fig.Figure 6A shows the positive electrode current collector plate 24. It should be noted that the negative electrode current collector plate 25 has a ribbon-shaped section 34, which differs from the ribbon-shaped section 32 of the positive electrode current collector plate 24. The ribbon-shaped section 34 of the negative electrode current collector plate 25 is shorter than the ribbon-shaped section 32 of the positive electrode current collector plate 24 and does not have a section corresponding to the insulating section 32A of the positive electrode current collector plate 24. The ribbon-shaped section 34 has projections 37, each of which is round and is shown as several circles. During resistance welding, the current concentrates on the projections 37, causing them to melt and the ribbon-shaped section 34 to be welded to a base of the outer casing box 11.Like the positive electrode current collector plate 24, the negative electrode current collector plate 25 also has a through-hole 36 near a central region of a fan-shaped section 33. In the secondary battery 1, the negative electrode current collector plate 25 is arranged such that the through-hole 36 overlaps with the through-hole 26 in the Z-axis direction.

[0045] The fan-shaped section 31 of the positive electrode current collector plate 24 covers only a portion of the upper end surface 41 due to its top-view shape. Similarly, the fan-shaped section 33 of the negative electrode current collector plate 25 covers only a portion of the lower end surface 42 due to its top-view shape. There are two reasons why the fan-shaped section 31 does not cover the entire upper end surface 41 and the fan-shaped section 33 does not cover the entire lower end surface 42: Firstly, to allow the electrolyte solution to penetrate the electrode winding body 20 uniformly during assembly of the secondary battery 1. Secondly, to facilitate the escape of gas that forms when the lithium-ion secondary battery is in an abnormally hot or overcharged state. [Positive electrode current collector 21A]

[0046] The positive electrode current collector 21A, for example, has an electrically conductive material such as aluminum. The positive electrode current collector 21A is a metal foil containing, for example, aluminum or an aluminum alloy. [Positive electrode active material layer 21B]

[0047] The positive electrode active material layer 21B comprises one or more positive electrode materials into which lithium can be deposited and from which lithium can be extracted. It should be noted that the positive electrode active material layer 21B may also comprise one or more other materials. Examples of the other materials include a positive electrode binder and a positive electrode conductor. Preferably, the positive electrode material is a lithium-containing compound, in particular a lithium-containing composite oxide or a lithium-containing phosphoric acid compound. The lithium-containing composite oxide is an oxide that contains lithium and one or more other elements as constituents, i.e., one or more elements other than lithium. The lithium-containing composite oxide can have any crystal structure, for example, without limitation, a layered rock salt crystal structure or a spinel crystal structure.The lithium-containing phosphoric acid compound is a compound that includes lithium and one or more other elements as components and, for example, has an olivine crystal structure. The positive electrode active material layer 21B preferably comprises, as the positive electrode active material, at least one of the following materials: lithium cobalt oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide. The positive electrode binder comprises, for example, one or more materials such as synthetic rubber or a polymer material. Examples of synthetic rubber include styrene-butadiene rubber, fluororubber, and ethylene propylene diene monomer rubber. Examples of polymer materials include polyvinylidene fluoride (PVDF) and polyimide. The positive electrode conductor comprises, for example, one or more carbon-based materials.Examples of carbon materials include graphite, carbon black, acetylene black, and Ketjen black. It should be noted that the positive electrode conductor can be any electrically conductive material, such as a metal or a conductive polymer. [Negative electrode current collector 22A]

[0048] The negative electrode current collector 22A, for example, comprises an electrically conductive material such as copper. The negative electrode current collector 22A is a metal foil containing, for example, nickel, a nickel alloy, copper, or a copper alloy. A surface of the negative electrode current collector 22A is preferably roughened. One reason for this is that it improves the adhesion of the negative electrode active material layer 22B to the negative electrode current collector 22A through the so-called anchoring effect. In this case, the surface of the negative electrode current collector 22A must be roughened at least in an area facing the negative electrode active material layer 22B. Examples of a roughening method include a process in which microparticles are formed by electrolytic treatment.In the electrolytic treatment, the microparticles are generated on the surface of the negative electrode current collector 22A using an electrolytic process in an electrolyzer. This results in the surface of the negative electrode current collector 22A being provided with irregularities. [Negative electrode active material layer 22B]

[0049] The negative electrode active material layer 22B comprises one or more negative electrode materials into which lithium can be deposited and from which lithium can be extracted. It should be noted that the negative electrode active material layer 22B may also comprise one or more other materials. Examples of these other materials include a negative electrode binder and a negative electrode conductor. The negative electrode material is, for example, a carbon material. One reason for this is that carbon materials exhibit only very minor changes in their crystal structure during the deposition and extraction of lithium, thus enabling a stable high energy density. Another reason is that carbon materials can also serve as negative electrode conductors, thereby improving the electrical conductivity of the negative electrode active material layer 22B.Examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite. The lattice plane spacing of the (002) plane of non-graphitizable carbon is preferably 0.37 nm or more, while for graphite it is preferably 0.34 nm or less. Specifically, examples of carbon materials include pyrolytic carbons, coke, glassy carbon fibers, a solid formed by burning an organic polymer, activated carbon, and carbon black. Examples of coke include pitch coke, needle coke, and petroleum coke. The solid formed by burning or carbonizing a polymer material such as phenolic resin or furan resin is called an organic polymer compound incandescent body. Furthermore, the carbon material can also be low-crystalline carbon that has been heat-treated at about 1000 °C or below, or amorphous carbon.The carbon material can have a fibrous, spherical, granular, or platelet-like form. In secondary battery 1, at an open-circuit voltage in the fully charged state (i.e., at battery voltage) of 4.25 V or more, the amount of deposited lithium per unit mass increases compared to an open-circuit voltage of 4.20 V, even when using the same positive electrode active material. Therefore, the amounts of the positive electrode active material and the negative electrode active material are adjusted accordingly. This allows a high energy density to be achieved.

[0050] The negative electrode active material layer 22B can also comprise a silicon-containing material as the negative electrode active material, which includes at least one component of silicon, silicon oxide, a carbon-silicon compound, or a silicon alloy. The term "silicon-containing material" is a collective term for materials that contain silicon as a constituent element. The silicon-containing material can consist solely of silicon, or two or more silicon-containing materials can be used together. The silicon-containing material can form an alloy with lithium and can be, for example, a single silicon component, a silicon alloy, a silicon compound, a mixture thereof, or a material with one or more phases thereof. Furthermore, the silicon-containing material can be crystalline or amorphous, or contain both crystalline and amorphous components.It should be noted that the term "single substance" is used here in a general sense and therefore may also contain a small amount of impurities – that is, purity is not limited to 100%. In addition to silicon, the silicon alloy may contain one or more elements such as tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, or chromium. The silicon compound may contain carbon and oxygen, for example, as additional elements besides silicon. It should be noted that the silicon compound may also contain one or more of the elements described above for the silicon alloy. Specific examples of silicon alloys and silicon compounds include: SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O and SiO. v(where 0 < v ≤ 2). It should be noted that v can be chosen within a desired range, for example in the range 0.2 < v < 1.4. [Separator 23]

[0051] The separator 23 is arranged between the positive electrode 21 and the negative electrode 22. The separator 23 allows lithium ions to pass through and prevents a short-circuit current caused by contact between the positive electrode 21 and the negative electrode 22. The separator 23 comprises, for example, one or more types of porous films, each containing, for example, a synthetic material or a ceramic, and can include a stacked film made of two or more types of porous films. Examples of synthetic materials include polytetrafluoroethylene, polypropylene, and polyethylene. Preferably, the separator 23 has base layers, each containing a single-layer polyolefin porous film made of polyethylene. One reason for this is that it allows for more favorable high-performance output characteristics compared to a stacked film.If the first separator element 23A and the second separator element of separator 23 each contain a single-layer porous polyolefin film, the thickness of this film is preferably at least 10 µm and at most 15 µm. An internal short circuit is sufficiently avoided if the thickness of the single-layer polyolefin film is at least 10 µm. Improved discharge capacity is achieved if the thickness is 15 µm or less. Furthermore, the porous film preferably has a basis weight of at least 6.3 g / m². 2 and at most 8.3 g / m² 2 An internal short circuit is sufficiently avoidable if the surface mass is at least 6.3 g / m². 2 The value is [value missing]. A better discharge capacity is achieved if the areal mass is at most 8.3 g / m². 2 amounts.

[0052] In particular, the separator 23 can, for example, comprise the porous film as any of the base layers described above and a polymer layer provided on one or both opposite surfaces of the respective base layer. One reason for this is to improve the adhesion of the separator 23 to the respective positive electrode 21 and negative electrode 22, thereby suppressing deformation of the electrode winding body 20. As a result, decomposition of the electrolyte solution is suppressed, and leakage of the electrolyte solution with which the base layers are impregnated is also suppressed. This prevents the resistance from increasing slightly during repeated charging and discharging and simultaneously suppresses battery swelling. The polymer layer contains, for example, a polymer material such as polyvinylidene fluoride.One reason for this is that such a polymer material exhibits excellent mechanical strength and electrochemical stability. It should be noted that polymer materials other than polyvinylidene fluoride can also be used. To form the polymer layer, for example, a solution in which the polymer material is dissolved in a solvent such as an organic solvent can be applied to the base layer and then dried. Alternatively, the base layer can be immersed in the solution and then dried. The polymer layer can contain one or more types of insulating particles, such as inorganic particles. Examples of inorganic particles include aluminum oxide and aluminum nitride. [Electrolyte solution]

[0053] The electrolyte solution comprises a solvent and an electrolyte salt. It should be noted that the electrolyte solution may also contain one or more other materials. Examples of such additional materials include additives. The solvent comprises one or more non-aqueous solvents, particularly organic solvents. An electrolyte solution containing a non-aqueous solvent is referred to as a non-aqueous electrolyte solution. The non-aqueous solvent may, for example, comprise a fluorine compound and a dinitrile compound. The fluorine compound may, for example, comprise at least one of the following: fluorinated ethylene carbonate, trifluorocarbonate, trifluoroethyl methyl carbonate, a fluorinated carboxylic acid ester, or a fluorine ether. The non-aqueous solvent may also contain at least one nitrile compound that is not a dinitrile compound. Examples of such compounds are mononitrile compounds and trinitrile compounds.For example, succinic dinitrile (SN) is a preferred dinitrile compound. It should be noted that the dinitrile compound is not limited to succinic dinitrile, but can also be another dinitrile compound such as adipodonitrile.

[0054] The electrolyte salt comprises, for example, one or more salts that contain, without limitation, a lithium salt. It should be noted that the electrolyte salt may also contain a salt other than the lithium salt. Examples of a salt other than the lithium salt include a salt of a light metal other than lithium. Examples of lithium salts include: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), dilithium hexafluorosilicate (Li2SF6), lithium chloride (LiCl), and lithium bromide (LiBr). In particular, the lithium sulfate preferably consists of one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, or lithium hexafluoroarsenate, and especially preferably lithium hexafluorophosphate.Although not particularly restricted, the electrolyte salt concentration is preferably in the range of 0.3 mol / kg to 3 mol / kg based on the solvent. If the electrolyte solution contains LiPF6 as the electrolyte salt, the concentration of LiPF6 in the electrolyte solution is preferably between 1.25 mol / kg and 1.45 mol / kg. One reason for this is that it prevents cycle degradation due to consumption or decomposition of the salt during high-load charging, thereby improving the high-load cycle stability. If the electrolyte solution also contains LiBF4 as an electrolyte salt, the concentration of LiBF4 in the electrolyte solution is preferably between 0.001 wt% and 0.1 wt%. One reason for this is that it even more effectively prevents cycle degradation due to consumption or decomposition of the salt during high-load charging, leading to a further improvement in the high-load cycle stability. [Horizontal cross-sectional shape of the secondary battery]

[0055] Fig. 7A and Fig. Figures 7B each schematically illustrate a structure in a horizontal cross-section perpendicular to the central axis CL of secondary battery 1. It should be noted that Fig. 7A and Fig. Figure 7B shows only the electrode winding body 20 and the outer housing box 11, and other components are not shown. Furthermore, they illustrate Fig. 7A and Fig. 7B each illustrates the electrode winding body 20 not with a detailed configuration, but to an extent that allows an understanding of the external shape of the electrode winding body 20. In particular, it illustrates Fig. 7A a horizontal cross-section of an upper part of the electrode winding body 20 in the vertical direction Z, and Fig.Figure 7B illustrates a horizontal cross-section of a lower part of the electrode winding body 20 in the vertical direction Z. Here, the upper part of the electrode winding body 20 in the vertical direction Z refers to any location in a section of the electrode winding body 20 above a center point CP ( Fig. 1) in the vertical direction Z. The lower part of the electrode winding body 20 in the vertical direction Z refers to any location in a section of the electrode winding body 20 below the center point CP ( Fig. 1) in the vertical direction Z. Specifically illustrated Fig. 7A the horizontal cross-section at a height position Lv1, which is indicated by an arrow in Fig. 1 is indicated, and Fig. 7B illustrates the horizontal cross-section at a height position Lv2, indicated by an arrow pointing in Fig.1 is specified. Here, the height position Lv1 corresponds to a height position of an upper edge of the electrode winding body 20 in the height direction Z, and the height position Lv2 corresponds to a height position of a lower edge of the electrode winding body 20 in the height direction Z.

[0056] In the secondary battery 1, the outer casing box 11, as shown in Fig. 7A and Fig. Figure 7B shows a substantially circular cross-sectional shape. Accordingly, the outer casing 11 has a substantially constant inner diameter D11. In contrast, the electrode winding body 20 in the upper part of the secondary battery 1, as shown in Figure 7B, has a substantially circular cross-sectional shape. Fig. Figure 7A shows a substantially elliptical cross-sectional shape. Here, a first radial direction, in which the outer diameter of the electrode winding body 20 is maximized in cross-section, is designated as radial direction R1. Fig.7A, the radial direction R1 corresponds to an up-down direction of the image plane. The electrode winding body 20 has a maximum diameter D20max1 along the radial direction R1 at the height position Lv1. Furthermore, the electrode winding body 20 has a minimum diameter D20min1 along a radial direction R2 at the height position Lv1. The radial direction R2 is perpendicular to the radial direction R1 and corresponds to a right-left direction of the image plane. (D20max1 - D20min1) / D20max1 is referred to as the flattening FT1 of the electrode winding body 20 at the height position Lv1.

[0057] As in Fig.As shown in Figure 7B, the horizontal cross-sectional shape of the electrode winding body 20 is also essentially elliptical in the lower part of the secondary battery 1. However, the flattening FT2 of the horizontal cross-sectional shape of the electrode winding body 20 at height position Lv2 is smaller than the flattening FT1 of the horizontal cross-sectional shape of the electrode winding body 20 at height position Lv1. In other words, the flattening FT1 of the horizontal cross-sectional shape of the electrode winding body 20 at height position Lv1 is larger than the flattening FT2 of the horizontal cross-sectional shape of the electrode winding body 20 at height position Lv2 (FT1 > FT2). The electrode winding body 20 has a maximum diameter D20max2 along the radial direction R1 at height position Lv2. The maximum diameter D20max2 at height position Lv2 is smaller than the maximum diameter D20max1 at height position Lv1.Furthermore, the electrode winding body 20 has a minimum diameter D20min2 along the radial direction R2 at height position Lv2. The flatness FT2 of the electrode winding body 20 at height position Lv2 is given by (D20max2 - D20min2) / D20max2. Additionally, the maximum diameter of the electrode winding body 20 at the midpoint CP in the height direction Z is smaller than the maximum diameter D20max1 at the upper edge of the electrode winding body 20 in the height direction Z and larger than the maximum diameter D20max2 at the lower edge of the electrode winding body in the height direction Z.

[0058] At height position Lv1, a section of an outer circumferential surface 20S of the electrode winding body 20 is preferably in contact with an inner surface 11WS2 of the side wall part 11W of the outer housing box 11, as shown in Fig.Figure 7A shows that in this case, the maximum diameter D20max1 of the electrode winding body 20 is essentially equal to the inner diameter D11 of the outer housing box 11. In contrast, at height position Lv2, the outer circumferential area 20S of the electrode winding body 20 is, as shown in Fig. Figure 7B shows the distance from the inner surface 11WS2 of the side wall part 11W of the outer housing box 11. That is, the maximum diameter D20max2 of the electrode winding body 20 is smaller than the inner diameter D11 of the outer housing box 11. [1-2. Operation]

[0059] In the secondary battery 1 according to the present embodiment, for example, during charging, lithium ions are released from the positive electrode 21, and the released lithium ions are incorporated into the negative electrode 22 via the electrolyte solution. In the secondary battery 1, for example, during discharging, lithium ions are released from the negative electrode 22, and the released lithium ions are incorporated into the positive electrode 21 via the electrolyte solution. [1-3. Manufacturing processes]

[0060] A method for manufacturing the secondary battery 1 is described with reference to Fig. 8 as well as Fig. 1 to 7B described. Fig. 8 is a perspective view depicting a manufacturing process of the in Fig. 1 describes the secondary battery shown.

[0061] First, the positive electrode current collector 21A is provided, and the positive electrode active material layer 21B is selectively formed on the surface of the positive electrode current collector 21A, forming the positive electrode 21 with the positive electrode cover area 211 and the positive electrode exposure area 212. Next, the negative electrode current collector 22A is provided, and the negative electrode active material layer 22B is selectively formed on the surface of the negative electrode current collector 22A, forming the negative electrode 22 with the negative electrode cover area 221 and the negative electrode exposure area 222. The positive electrode 21 and the negative electrode 22 can be subjected to a drying process. Subsequently, the positive electrode 21 and the negative electrode 22 are stacked, with the first separator element 23A and the second separator element 23B, respectively, on the positive electrode 21 and the negative electrode 22, respectively.The negative electrode 22 is arranged such that the positive electrode exposure area 212 and the first section 222A of the negative electrode exposure area 222 are opposite each other in the W-axis direction. This forms the stacking body S20. The stacking body S20 is then wound spirally to form the through-hole 26. For example, a cylindrical core is used for winding the stacking body S20, the cross-section of which gradually transitions from elliptical to circular along the height direction, with the stacking body S20 being wound around the cylindrical core. The fastening strap 46 is then attached to an outermost turn of the spirally wound stacking body S20, after which the core is removed. The electrode winding body 20 is obtained as shown in part (A) of . Fig.Figure 8 illustrates this. Alternatively, the stack body S20 can be wound around a cylindrical core with a circular cross-sectional shape, and the core can then be removed. Subsequently, slight vertical pressure can be applied to a section of the wound stack body S20 using a tool such as a clamp to create the electrode coil body 20 with the specified flats FT1 and FT2.

[0062] Then, as in Part (B) of Fig.As shown in Figure 8, a section of the upper end surface 41 and a section of the lower end surface 42 of the electrode winding body 20 are each locally bent, for example by pressing one end of a 0.5 mm thick flat plate perpendicularly, i.e. in the Z-axis direction, against the upper end surface 41 and against the lower end surface 42. This forms grooves 43 that extend radially (in the R directions) from the through-hole 26. It should be noted that the number and arrangement of the grooves shown in part (B) of Fig. The grooves shown in 8 (43) are merely an example and the disclosure is not limited to them.

[0063] Then, as in Part (C) of Fig.As shown in Figure 8, essentially uniform pressures in a substantially perpendicular direction are exerted on the upper end surface 41 and the lower end surface 42 of the electrode winding body 20 essentially simultaneously from above and below. At this point, for example, a rod-shaped tool is inserted into the through-hole 26 beforehand. This process bends the positive electrode exposure area 212 and the first section 222A of the negative electrode exposure area 222, so that the upper end surface 41 and the lower end surface 42 are each formed into surfaces.The positive electrode edge sections 212E of the positive electrode exposure area 212, arranged on the upper end face 41, are bent towards the through-hole 26, overlapping each other, and the negative electrode edge sections 222E of the negative electrode exposure area 222, arranged on the lower end face 42, are bent towards the through-hole 26, also overlapping each other. Subsequently, the fan-shaped section 31 of the positive electrode current collector plate 24 is joined to the upper end face 41 by a process such as laser welding, and the fan-shaped section 33 of the negative electrode current collector plate 25 is joined to the lower end face 42 by a process such as laser welding.

[0064] The insulating tapes 53 and 54 are then attached to their respective designated positions on the electrode winding body 20. Afterwards, as described in part (D) of Fig.Figure 8 shows that the ribbon-shaped section 32 of the positive electrode current collector plate 24 is bent and inserted through a hole 12H in the insulating plate 12. Furthermore, the ribbon-shaped section 34 of the negative electrode current collector plate 25 is bent and inserted through a hole 13H in the insulating plate 13.

[0065] The electrode winding body 20, assembled as described above, is then inserted into the part (E) of Fig. The outer housing box 11 shown in Figure 8 is inserted, whereupon a bottom section of the outer housing box 11 and the negative electrode current collector plate 25 are welded together. A narrow section 11S is then formed near the open end part 11N of the outer housing box 11. The electrolyte solution is then injected into the outer housing box 11, whereupon the ribbon-shaped section 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 are welded together.

[0066] Then, as in part (F) of Fig. As shown in Figure 8, the outer casing 11 is sealed using the narrow section 11S with the seal 15, the safety valve mechanism 30, and the battery cover 14. Finally, the outer casing 11 is encased with the outer casing tube 50, with the washer 55 attached to the battery cover 14. The outer casing tube 50 is then heated, for example, by blowing hot air through it. This causes the outer casing tube 50 to shrink and fit tightly against the outer surface of the outer casing 11.

[0067] The secondary battery 1 according to the present embodiment is completed in the manner described above. [1-4. Effects and impact]

[0068] As described above, in the secondary battery 1 of the present embodiment, the flattened area FT1 of the horizontal cross-sectional shape of the upper part of the electrode winding body 20 is larger than the flattened area FT2 of the horizontal cross-sectional shape of the lower part of the electrode winding body 20 (FT1 > FT2). Because the flattened area FT2 of the lower part of the electrode winding body 20 is smaller than the flattened area FT1 of the upper part of the electrode winding body 20, the electrode winding body 20 can be more easily inserted into the outer casing 11 during assembly of the secondary battery 1.This means that by reducing the flattening FT2 of the lower part of the electrode winding body 20, and thus by approximating the cross-sectional shape of the lower part of the electrode winding body 20 to a perfect circle, the electrode winding body 20 can be easily inserted into the outer housing 11 without the outer circumferential surface 20S of the electrode winding body 20 interfering with the upper end part of the outer housing 11. At the same time, since the flattening FT1 of the upper part of the electrode winding body 20 is larger than the flattening FT2 of the lower part of the electrode winding body 20, the outer circumferential surface 20S of the upper part of the electrode winding body 20 contained in the outer housing 11 is able to make contact with the inner surface 11WS2 of the outer housing 11.This helps to prevent the electrode winding body 20 from moving slightly within the outer casing 11, even if the secondary battery 1 is subjected to vibrations or impacts, for example. This prevents damage to the electrode winding body 20 itself, as well as damage to a coupling section between the positive electrode current collector plate 24, which is connected to the electrode winding body 20, and the battery cover 14. The secondary battery 1 thus offers superior vibration resistance without compromising manufacturability.

[0069] In particular, the secondary battery 1 has a so-called tabless structure, in which the electrode winding body 20 does not have an electrode welding flap extending in the vertical direction Z. This allows the electrode winding body 20 to be soft and malleable, and its flattening can be easily adjusted. This is advantageous for realizing an electrode winding body 20 in which the horizontal cross-sectional shape of the upper part in the vertical direction Z differs from that of the lower part in the same direction. Furthermore, instead of a winding core, the electrode winding body 20 has a through-hole 26 in a central area. This is also advantageous for realizing an electrode winding body 20 in which the horizontal cross-sectional shape of the upper part in the vertical direction Z differs from that of the lower part in the same direction. [2. Application examples]

[0070] Examples of applications of the secondary battery 1 according to the foregoing embodiment of the disclosure are as described below. [2-1. Battery pack]

[0071] Fig. Figure 9 is a block diagram illustrating a circuit configuration example in which a battery according to an embodiment of the invention is applied to a battery pack 300. Hereinafter, the battery according to the embodiment may optionally be referred to as the "secondary battery". The battery pack 300 comprises a composite battery 301, an outer casing, a switch 304, a current sensing resistor 307, a temperature sensor 308, and a controller 310. The switch 304 comprises a charging switch 302a and a discharging switch 303a.

[0072] The battery pack 300 has a positive electrode terminal 321 and a negative electrode terminal 322. During charging, the positive electrode terminal 321 and the negative electrode terminal 322 are each connected to a positive electrode terminal and a negative electrode terminal, respectively, of a charger to perform the charging process. When using an electronic device, the positive electrode terminal 321 and the negative electrode terminal 322 are each connected to a positive electrode terminal and a negative electrode terminal, respectively, of the electronic device to perform the discharging process.

[0073] The composite battery 301 comprises several secondary batteries 301a connected in series or parallel. The secondary battery 1 described above is applicable to each of the secondary batteries 301a. It should be noted that Fig.Figure 9 shows an example case in which six secondary batteries 301a are configured in a two-parallel and three-series (2P3S) circuit; however, the secondary batteries 301a can also be connected in any other way, for example in any n-parallel and m-series (where n and m are integers).

[0074] The switch 304 comprises the charging switch 302a, a diode 302b, the discharging switch 303a, and a diode 303b, and is controlled by the controller 310. The diode 302b has a reverse polarity with respect to a charging current extending from the positive electrode terminal 321 to the composite battery 301, and a forward polarity with respect to a discharging current extending from the negative electrode terminal 322 to the composite battery 301. The diode 303b has a forward polarity with respect to the charging current and a reverse polarity with respect to the discharging current. Fig. 9 The switch 304 can be provided on the positive side; however, in some embodiments the switch 304 can be provided on the negative side.

[0075] The charging switch 302a is controlled by a charging and discharging controller such that, if the battery voltage reaches an overcharge voltage, the charging switch 302a is switched off to prevent the charging current from flowing through a current path of the composite battery 301. After the charging switch 302a is switched off, only discharging via the diode 302b is possible. Furthermore, the charging switch 302a is controlled by the controller 310 such that, if a large current flows during charging, the charging switch 302a is switched off to block the charging current flowing through the current path of the composite battery 301. The discharge switch 303a is controlled by the controller 310 such that, if the battery voltage reaches a deep discharge voltage, the discharge switch 303a is switched off to prevent the discharge current from flowing through the current path of the composite battery 301.After the discharge switch 303a is switched off, charging is only possible via the diode 303b. Furthermore, the discharge switch 303a is controlled by the controller 310 such that, if a large current flows during discharge, the discharge switch 303a is switched off in order to block the discharge current flowing through the current path of the composite battery 301.

[0076] The temperature sensor 308, for example, is a thermistor. The temperature sensor 308 is located near the battery assembly 301, measures the temperature of the battery assembly 301, and transmits the measured temperature to the controller 310. A voltmeter 311 measures the voltage of the battery assembly 301 and the voltage of each of the secondary batteries 301a contained in the battery assembly 301, performs an analog-to-digital conversion of the measured voltages, and transmits the converted voltages to the controller 310. An ammeter 313 measures the current using the current sensing resistor 307 and transmits the measured current to the controller 310. A switching control unit 314 controls the charging switch 302a and the discharging switch 303a of the switch 304 based on the voltages input from the voltmeter 311 and the current input from the ammeter 313.

[0077] If the voltage of one of the multiple secondary batteries 301a reaches or falls below the overcharge voltage, reaches or falls below the deep discharge voltage, or if a large current suddenly flows, the switching controller 314 transmits a control signal to the switch 304 to prevent overcharging, deep discharge, and overcurrent charging and discharging. For example, if the secondary battery is a lithium-ion battery, the overcharge voltage is set to 4.20 V ± 0.05 V and the deep discharge voltage to 2.4 V ± 0.1 V.

[0078] Semiconductor switches such as MOSFETs can be used as charge and discharge switches. In this case, the parasitic diodes of the MOSFETs serve as diodes 302b and 303b. When P-channel FETs are used as charge and discharge switches, the switching controller 314 transmits the control signals DO and CO to a gate of the charge switch 302a and a gate of the discharge switch 303a, respectively. If the charge switch 302a and the discharge switch 303a are of the P-channel type, they are switched on by a gate potential that is lowered relative to the source potential by a predetermined amount or more. That is, in normal charge and discharge operation, the control signals CO and DO are set to a low level to switch on the charge switch 302a and the discharge switch 303a.

[0079] In the event of overcharging or deep discharging, the control signals CO and DO are set to a high level, for example, to switch off the charging switch 302a and the discharging switch 303a.

[0080] Memory 317 comprises RAM and ROM. Memory 317 includes, for example, a resettable, programmable read-only memory device (EPROM) as non-volatile memory. Values ​​such as numerical values ​​calculated by the controller 310 and the initial internal resistance of each of the secondary batteries 301a, measured during manufacturing, are pre-stored in memory 317 and can be overwritten as needed. Furthermore, by storing the full charge capacity of the secondary battery 301a, it is possible to calculate, for example, a remaining capacity using the controller 310.

[0081] A temperature sensor 318 measures a temperature using the temperature sensor device 308, performs charge and discharge control in case of abnormal heat generation and makes a correction in the calculation of the remaining capacity. [2-2. Electrical Power Storage System]

[0082] The secondary battery according to the foregoing embodiment of the disclosure can, for example, be installed in or used for power supply in any device, including, but not limited to, electronic devices, an electric vehicle, an electric aircraft or an electrical power storage device.

[0083] Examples of electronic devices include portable personal computers, smartphones, tablet terminals, PDAs (i.e., mobile information terminals), mobile phones, portable devices, portable video recording and playback devices, digital cameras, e-books, electronic dictionaries, music players, radios, headphones, gaming devices, navigation systems, memory cards, pacemakers, hearing aids, power tools, electric razors, refrigerators, air conditioners, televisions, stereo systems, water heaters, microwave ovens, dishwashers, washing machines, dryers, lighting equipment, toys, medical devices, robots, street air conditioners, and traffic light systems.

[0084] Examples of electric vehicles include rail vehicles, golf carts, electric trolleys, and electric cars, including hybrid electric cars. The secondary battery can be used as a drive energy source or auxiliary energy source for any of these electric vehicles. Examples of electrical power storage devices include an electrical power source for buildings, including residential buildings, or for power generation facilities. Examples

[0085] Examples of revelation are described. [Examples 1-1 to 1-4 and comparison examples 1-1 to 1-4]

[0086] As described below, cylindrical secondary batteries were manufactured, such as those found, for example, in Fig.Figure 1 shows the dimensions of each of the manufactured secondary batteries, after which the dimensions of each were measured. Each of the manufactured lithium-ion secondary batteries had nominal dimensions of 21 mm in diameter and 70 mm in length. [Manufacturing process]

[0087] First, a 12 µm thick aluminum foil was provided as a positive electrode current collector 21A. Subsequently, a positive electrode composite material was prepared by mixing a layered lithium oxide as the positive electrode active material with a positive electrode binder and a conductive additive. The layered lithium oxide comprised lithium nickel cobalt aluminum oxide (NCA) with a nickel content of 85% or more. The positive electrode binder comprised polyvinylidene fluoride. The conductive additive comprised a mixture of carbon black, acetylene black, and Ketjen black. The mixing ratio between the positive electrode active material, the positive electrode binder, and the conductive additive was adjusted to 96.4 : 2 : 1.6.The positive electrode mixture material was then introduced into an organic solvent (N-methyl-2-pyrrolidone), and the solvent was stirred to produce a paste-like slurry of the positive electrode mixture material. This slurry was then applied to predetermined areas on the two opposing surfaces of the positive electrode current collector 21A using a coating device. The applied slurry was dried to form the positive electrode active material layers 21B. A coating material comprising polyvinylidene fluoride (PVDF) was then applied to the surfaces of the positive electrode exposure area 212 in areas adjacent to the positive electrode cover area 211.The applied coating material was dried to form insulating layers 101, each 3 mm wide and 8 µm thick. The positive electrode active material layers 21B were then compacted using a roller press. This resulted in the positive electrode 21 with the positive electrode cover area 211 and the positive electrode exposure area 212. The positive electrode 21 was then cut to size, with the positive electrode cover area 211 having a width of 60 mm in the W-axis direction and the positive electrode exposure area 212 having a width of 7 mm in the W-axis direction. The length of the positive electrode 21 in the L-axis direction was set to 1700 mm.

[0088] Furthermore, a copper foil with a thickness of 8 µm was provided as a 22 A negative electrode current collector. Subsequently, a negative electrode composite material was prepared by mixing the negative electrode active material with a negative electrode binder and a conductive additive. The negative electrode active material comprised a mixture of a carbon material and SiO₂. The carbon material comprised graphite. The negative electrode binder comprised polyvinylidene fluoride. The conductive additive comprised a mixture of carbon black, acetylene black, and Ketjen black. The mixing ratio between the negative electrode active material, the negative electrode binder, and the conductive additive was set to 96.1 : 2.9 : 1.0. The mixing ratio between graphite and SiO₂ in the negative electrode active material was set to 95 : 5.The negative electrode mixture material was then introduced into an organic solvent (N-methyl-2-pyrrolidone), and the solvent was stirred to produce a paste-like negative electrode mixture slurry. This slurry was then applied to predetermined areas of the two opposing surfaces of the negative electrode current collector 22A using a coating device. The applied slurry was dried to form the negative electrode active material layers 22B. These layers were then compacted using a roller press, resulting in the negative electrode 22 with the negative electrode cover area 221 and the negative electrode exposure area 222.The negative electrode 22 was then cut to size so that the negative electrode cover area 221 had a width of 62 mm in the W-axis direction and the first section 222A of the negative electrode exposure area 222 had a width of 4 mm in the W-axis direction. The length of the negative electrode 22 in the L-axis direction was set to 1760 mm.

[0089] Subsequently, the positive electrode 21 and the negative electrode 22 were stacked, with the first separator element 23A and the second separator element 23B, respectively, positioned on the positive electrode 21 and the negative electrode 22, respectively, such that the positive electrode exposure area 212 and the first section 222A of the negative electrode exposure area 222 were aligned along the W-axis. This formed the stack body S20. At this stage, the stack body S20 was manufactured such that the positive electrode active material layers 21B did not extend beyond the negative electrode active material layers 22B along the W-axis. It should be noted that, as described later in Table 1, the stack body S20 was manufactured to have a first distance L1 of 3 mm and a second distance L2 of 3 mm.A polyethylene film with a width of 65 mm and a thickness of 14 µm was used as the first separator element 23A and the second separator element 23B, respectively. The stacking body S20 was then wound spirally to form the through-hole 26, and the fastening strip 46 was attached to the outermost winding of the wound stacking body S20. This formed the electrode winding body 20. Pressure was applied to end regions of the resulting electrode winding body 20 in a lateral direction from the outer circumferential surface of the electrode winding body 20 towards a winding center of the electrode winding body 20 in order to adjust the flats FT1 and FT2 to predetermined values.

[0090] Subsequently, the upper end surface 41 and the lower end surface 42 of the electrode winding body 20 were each locally bent by pressing one end of a 0.5 mm thick flat plate against the upper end surface 41 and the lower end surface 42, respectively, in the Z-axis direction. This formed the grooves 43, which extend radially in the radial directions (the R directions) from the through hole 26.

[0091] Subsequently, essentially uniform pressures were applied to the upper end surface 41 and the lower end surface 42, in a substantially perpendicular direction from above and below, on the electrode winding body 20. This caused the positive electrode exposure area 212 and the first section 222A of the negative electrode exposure area 222 to bend, so that the upper end surface 41 and the lower end surface 42 were each formed into surfaces. The positive electrode edge sections 212E of the positive electrode exposure area 212 located on the upper end surface 41 were bent towards the through-hole 26, overlapping each other, and the negative electrode edge sections 222E of the negative electrode exposure area 222 located on the lower end surface 42 were also bent towards the through-hole 26, likewise overlapping each other.Subsequently, the fan-shaped section 31 of the positive electrode current collector plate 24 was connected to the upper end surface 41 by laser welding, and the fan-shaped section 33 of the negative electrode current collector plate 25 was connected to the lower end surface 42 by laser welding.

[0092] Subsequently, the insulating tapes 53 and 54 were attached to their respective designated positions on the electrode winding body 20, whereupon the ribbon-shaped section 32 of the positive electrode current collector plate 24 was bent and inserted through the hole 12H of the insulating plate 12, and the ribbon-shaped section 34 of the negative electrode current collector plate 25 was bent and inserted through the hole 13H of the insulating plate 13.

[0093] The electrode winding body 20, assembled as described above, was then inserted into the outer housing 11, whereupon a bottom section of the outer housing 11 and the negative electrode current collector plate 25 were welded together. It should be noted that the outer housing 11 had an inner diameter D11 of 20.80 mm ± 0.05 mm. Next, the narrow section 11S near the open end section 11N of the outer housing 11 was formed. Furthermore, the electrolyte solution was injected into the outer housing 11, whereupon the ribbon-shaped section 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 were welded together.

[0094] The electrolyte solution used consisted of a solvent prepared by adding fluoroethylene carbonate (FEC) and succinonitrile (SN) to a main solvent, namely ethylene carbonate (EC) and dimethyl carbonate (DMC), and containing LiBF4 and LiPF6 as the electrolyte salt. In the lithium-ion secondary battery of the present embodiment, the ratio (weight percent) of EC, DMC, FEC, SN, LiBF4, and LiPF6 in the electrolyte solution was adjusted to 12.7:56.2:12.0:1.0:1.0:17.1.

[0095] Subsequently, a seal was formed using the gasket 15, the safety valve mechanism 30, and the battery cover 14, employing the tight section 11S. Finally, the outer casing 11, with the washer 55 attached to the battery cover 14, was covered with the outer casing sleeve 50, after which the outer casing sleeve 50 was heated by applying hot air. This caused the outer casing sleeve 50 to shrink and adhere tightly to the outer surface of the outer casing 11.

[0096] The secondary batteries of embodiments 1-1 to 1-4 and of comparison examples 1-1 to 1-4 were thus obtained. [Battery performance evaluation]

[0097] The secondary batteries described above, in embodiments 1-1 to 1-4 and in comparative examples 1-1 to 1-4, were each subjected to measurements of the respective outer diameters of the upper and lower sections of the electrode winding body 20, an evaluation of the ease of inserting the electrode winding body 20 into the outer casing 11, and an evaluation of its vibration resistance. The results are summarized in Table 1. [Table 1] Table 1 D11[mm] Upper part of the electrode winding body Lower part of the electrode winding body FT1 / FT2 Ease of use Drum test [min] D20max1[mm] D20min1[mm] FT1[%] D20max1[mm] D20min1[mm] FT2[%] Example 1-1 20,8 20,821 20,553 1,29 20,687 20,585 0,49 2,61 P 100 Example 1-2 20,8 20,663 20,400 1,27 20,483 20,320 0,80 1,60 P 100 Examples 1-3 20,8 20,950 20,740 1,00 20,824 20,708 0,56 1,79 P 2120 Examples 1-4 20,8 20,661 20,400 1,26 20,652 20,400 1,22 1,04 P 100 Comparison example 1-1 20,8 20,895 20,882 0,06 20,892 20,879 0,06 1,00 F 100 Comparison example 1-2 20,8 20,410 20,380 0,15 20,590 20,340 1,21 0,12 P 75 Comparison example 1-3 20,8 20,892 20,884 0,04 20,955 20,742 1,02 0,04 F - Comparison example 1-4 20,8 20,401 20,400 0,00 20,399 20,398 0,00 1,00 P 60 [Measurement of outer diameters]

[0098] The maximum diameter D20max1 of the upper section of the electrode winding body 20, the minimum diameter D20min1 of the upper section of the electrode winding body 20, the maximum diameter D20max2 of the lower section of the electrode winding body 20, and the minimum diameter D20min2 of the lower section of the electrode winding body 20 were measured. Specifically, when the electrode winding body 20 was rotated about its central axis as the axis of rotation, the outer diameter of a two-dimensional projection image of the electrode winding body 20 was measured using a two-dimensional projection outer diameter measuring device. The maximum and minimum diameters in the cross-section of the electrode winding body 20 were measured at the height position Lv1, which is located in Fig.Figure 1 is used as the maximum diameter D20max1 and the minimum diameter D20min1, respectively. Furthermore, the maximum and minimum diameters in the cross-section of the electrode winding body 20 at the height position Lv2, which is shown in Figure 1, were determined. Fig. Figure 1 is used as the maximum diameter D20max2 and the minimum diameter D20min2, respectively. In each of the embodiments 1-1 to 1-4, as well as the comparative examples 1-2 and 1-4, the secondary battery was disassembled and the outer diameters of the removed electrode winding body 20 were measured. It should be noted that in embodiment 1-3, the maximum diameter D20max1 of the upper section was larger than the inner diameter D11 of the outer casing 11. This was due to the expansion of the negative electrode active material layers 22B as a result of charging and discharging. The maximum value of the inner diameter D11 of the outer casing 11 in embodiment 1-3 increased accordingly. [Assessment of the ease of inserting the electrode coil body]

[0099] When assessing the ease of inserting the outer housing box 11 into the electrode winding body 20, the case where it was not possible to insert the electrode winding body 20 into the outer housing box 11, for example due to contact between the outer circumferential surface 20S of the electrode winding body 20 and the open end section 11N, was rated as "fail," indicated by "F" in Table 1. Conversely, a case where it was possible to insert the electrode winding body 20 into the outer housing box 11 was rated as "pass," indicated by "P" in Table 1.It should be noted that in each of the comparison examples 1-1 and 1-3, in which it was not possible to insert the electrode winding body 20 into the outer housing box 11, the maximum diameter D20max1 of the upper section of the electrode winding body 20, the minimum diameter D20min1 of the upper section of the electrode winding body 20, the maximum diameter D20max2 of the lower section of the electrode winding body 20 and the minimum diameter D20min2 of the lower section of the electrode winding body 20 were each measured before the electrode winding body 20 was inserted into the outer housing box 11. [Assessment of vibration resistance]

[0100] In each of the examples and comparison examples, six secondary batteries (n = 6) were manufactured, and the manufactured secondary batteries were subjected to the vibration resistance assessment described below. A drum test was performed to measure any change in impedance. Specifically, the following experiment was carried out. That is, the secondary batteries were each set to have an output voltage of 4.2 V and placed in a hexagonal iron drum of a rotating drum tester. The hexagonal iron drum had an inscribed circle with a diameter φ of 190 mm and a length of 200 mm. The hexagonal drum was rotated at an angular velocity of 60 rpm (2π rad / s) to impart mechanical vibrations to the secondary batteries. Afterward, each of the secondary batteries was removed, and the open-circuit voltage (OCV) and impedance were measured.The vibration test was repeated until each secondary battery was deemed "failed" based on the significantly increased impedance value after vibration compared to the initial value. Generally, the application of vibration leads to the gradual detachment of the lid and the bonded positive electrode current collector plate, which in turn increases the impedance. Therefore, the secondary battery in which the vibration duration required to increase the impedance was longer was rated as having higher vibration resistance.

[0101] As shown in Table 1, in each of examples 1-1 to 1-4, the ease of insertion assessment resulted in a "pass" because the flattening FT1 was greater than the flattening FT2, in other words, because (FT1 / FT2) > 1 was satisfied; and the drum test showed that resistance to at least 100 minutes of vibration was achieved. In contrast, in the comparison examples 1-1 and 1-3, where the flattening FT1 was less than the flattening FT2, in other words, where (FT1 / FT2) ≤ 1 was satisfied, the ease of insertion assessment resulted in a "fail," making further measurement difficult. In comparison examples 1-2 and 1-4, although insertion was "passed," sufficient vibration resistance was not achieved.

[0102] The results described above showed that it was possible to achieve excellent vibration resistance using the secondary battery according to the disclosure, without affecting manufacturability.

[0103] Although the disclosure has been described above with reference to some embodiments and examples, the configuration of the disclosure is not limited to the configuration described in the embodiments and examples above and is therefore modifiable in many ways. For example, a secondary battery with a so-called tabless structure was described in the embodiments and examples above; however, the secondary battery according to the disclosure is not limited to this and is also applicable to a secondary battery with a so-called tab structure.

[0104] For example, the embodiments and examples above described the case in which the electrode reaction agent is lithium; however, the electrode reaction agent is not particularly limited. Accordingly, the electrode reaction agent can also be another alkali metal such as sodium or potassium, or an alkaline earth metal such as beryllium, magnesium, or calcium, as described above. Furthermore, the electrode reaction agent can also be another light metal such as aluminum.

[0105] The effects described herein are merely examples, and the effects of revelation are not limited to those described here. Accordingly, revelation may also produce other effects.

[0106] The disclosure may include the following embodiments. (1) comprising a secondary battery: an electrode winding body comprising a positive electrode and a negative electrode stacked on top of each other with a separator in between and wound around a central axis, and a battery box having a cylindrical outer shape in which a vertical direction corresponds to a direction along the central axis, wherein the battery box houses the electrode winding body, wherein the battery box a container with a lower end part and an upper end part, wherein the lower end part is closed by a bottom part, the upper end part is arranged in a direction opposite to the lower end part in the vertical direction and has an opening through which the electrode winding body can be passed, and a cover part that closes the opening of the container, and If a flattening of the electrode winding body is a ratio of a maximum diameter of the electrode winding body to a minimum diameter of the electrode winding body, then the flattening of at least one section of an upper part of the electrode winding body is greater than the flattening of at least one section of a lower part of the electrode winding body. (2) Secondary battery after <1> , wherein the flattening at an upper edge of the electrode winding body in the vertical direction is greater than the flattening at a lower edge of the electrode winding body in the vertical direction. (3) Secondary battery after <1> or <2> , where the maximum diameter of the electrode winding body is essentially equal to the inner diameter of the battery box. (4) Secondary battery after a <1> until <3> , wherein a maximum diameter at a center point of the electrode winding body in the vertical direction is smaller than a maximum diameter at an upper edge of the electrode winding body in the vertical direction and larger than a maximum diameter at a lower edge of the electrode winding body in the vertical direction. (5) Secondary battery after a <1> until <4> , wherein the electrode winding body has a through-hole in a central part of the electrode winding body. (6) Secondary battery after a <1> until <5> , wherein a section of the upper part of the electrode winding body is in contact with an inner surface of the container. (7) Secondary battery after a <1> until <6> , wherein a maximum diameter of the upper part of the electrode winding body is larger than a maximum diameter of the lower part of the electrode winding body. (8) Secondary battery after a <1> until <7> , furthermore showing: a positive electrode current collector plate, which faces a first end surface of the electrode winding body in the vertical direction, and a negative electrode current collector plate which faces a second end face of the electrode winding body in the vertical direction, wherein the second end face is arranged on one side opposite to the first end face in the vertical direction, wherein the positive electrode has a positive electrode cover area in which a positive electrode current collector is covered with a positive electrode active material layer, and a positive electrode exposure area in which the positive electrode current collector is exposed without being covered with the positive electrode active material layer and is connected to the positive electrode current collector plate, the negative electrode has a negative electrode cover area in which a negative electrode current collector is covered with a negative electrode active material layer, and a negative electrode exposure area in which the negative electrode current collector is exposed without being covered with the negative electrode active material layer and is connected to the negative electrode current collector plate, and the positive electrode exposure area wound around the central axis has several first edge sections adjacent to each other in a radial direction of the electrode winding body, and the negative electrode exposure area wound around the central axis has several second edge sections adjacent to each other in the radial direction, wherein the several first edge sections, the several second edge sections or both in the direction. (9) Battery pack comprising: the secondary battery according to any one of claims 1 to 8, a controller that controls the secondary battery, and an outer casing that houses the secondary battery. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2021 / 020235

[0004]

Claims

[1] Having a secondary battery: an electrode winding body comprising a positive electrode and a negative electrode stacked on top of each other with a separator in between and wound around a central axis, and a battery box having a cylindrical outer shape in which a vertical direction corresponds to a direction along the central axis, wherein the battery box houses the electrode winding body, wherein the battery box a container with a lower end part and an upper end part, wherein the lower end part is closed by a bottom part, the upper end part is arranged in a direction opposite to the lower end part in the vertical direction and has an opening through which the electrode winding body can be passed, and a cover part that closes the opening of the container, and If a flattening of the electrode winding body is a ratio of a maximum diameter of the electrode winding body to a minimum diameter of the electrode winding body, then the flattening of at least one section of an upper part of the electrode winding body is greater than the flattening of at least one section of a lower part of the electrode winding body. [2] Secondary battery according to claim 1, wherein the flattening at an upper edge of the electrode winding body in the vertical direction is greater than the flattening at a lower edge of the electrode winding body in the vertical direction. [3] Secondary battery according to claim 1 or 2, wherein the maximum diameter of the electrode winding body is substantially equal to an inner diameter of the battery box. [4] Secondary battery according to any one of claims 1 to 3, wherein a maximum diameter at a center point of the electrode winding body in the vertical direction is smaller than a maximum diameter at an upper edge of the electrode winding body in the vertical direction and is larger than a maximum diameter at a lower edge of the electrode winding body in the vertical direction. [5] Secondary battery according to any one of claims 1 to 4, wherein the electrode winding body has a through hole in a central part of the electrode winding body. [6] Secondary battery according to any one of claims 1 to 5, wherein a section of the upper part of the electrode winding body is in contact with an inner surface of the container. [7] Secondary battery according to any one of claims 1 to 6, wherein a maximum diameter of the upper part of the electrode winding body is larger than a maximum diameter of the lower part of the electrode winding body. [8] Secondary battery according to any one of claims 1 to 7, further comprising: a positive electrode current collector plate, which faces a first end surface of the electrode winding body in the vertical direction, and a negative electrode current collector plate which faces a second end face of the electrode winding body in the vertical direction, wherein the second end face is arranged on one side opposite to the first end face in the vertical direction, wherein the positive electrode has a positive electrode cover area in which a positive electrode current collector is covered with a positive electrode active material layer, and a positive electrode exposure area in which the positive electrode current collector is exposed without being covered with the positive electrode active material layer and is connected to the positive electrode current collector plate, the negative electrode has a negative electrode cover area in which a negative electrode current collector is covered with a negative electrode active material layer, and a negative electrode exposure area in which the negative electrode current collector is exposed without being covered with the negative electrode active material layer and is connected to the negative electrode current collector plate, and the positive electrode exposure area wound around the central axis has several first edge sections that adjoin each other in a radial direction of the electrode winding body, and the negative electrode exposure area wound around the central axis has several second edge sections that adjoin each other in the radial direction, wherein the several first edge sections, the several second edge sections, or both point in the direction of [9] Including battery pack: the secondary battery according to any one of claims 1 to 8, a controller that controls the secondary battery, and an outer casing that houses the secondary battery.

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