SECONDARY BATTERY AND BATTERY PACK

Abstract

A secondary battery (1) comprises a stack body (S20) having a positive electrode (21), a negative electrode (22), and a separator (23). The positive electrode (21) has a positive electrode active material layer (21B), a positive electrode current collector (21A), and an insulating layer (101). The positive electrode current collector (21A) has a covered positive electrode region (211) and an exposed positive electrode region (212). The exposed positive electrode region (212) is not covered by a positive electrode active material layer (21B) and extends in a lateral direction from the positive electrode active material layer (21B). The insulating layer (101) extends along a first edge (21BT1) of the positive electrode active material layer (21B). The first edge (21BT1) is located at a boundary (K) between the covered positive electrode area (211) and the exposed positive electrode area (212).The positive electrode active material layer (21B) has a first thin part (61) and a first thick part (71) which borders the first thin part (61) in the width direction.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims priority to Japanese Patent Application No. 2023-165908, filed on September 27, 2023, the entire contents of which are hereby incorporated by reference. BACKGROUND

[0002] The disclosure relates to a secondary battery and to a battery pack containing the secondary battery.

[0003] Various types of electronic devices, including mobile phones, are widely used. This widespread use has encouraged the development of a secondary battery as a power source, which is smaller and lighter and allows for higher energy density. The secondary battery comprises a battery device contained within an outer housing container. Various secondary battery configurations have been considered.

[0004] For example, International Publication No. WO 2021 / 020237 proposes a secondary battery using a so-called tableless structure. Such a secondary battery achieves reduced internal resistance and enables charging and discharging with a relatively high current. SUMMARY

[0005] A secondary battery according to one embodiment of the disclosure includes an electrode winding body and an outer casing container. The electrode winding body includes a stacked body and has a through-hole. The stacked body includes a positive electrode, a negative electrode, and a separator, and is wound along a longitudinal direction of the stacked body. The through-hole is provided through the electrode winding body in a width direction orthogonal to the longitudinal direction. The outer casing container contains the electrode winding body. The positive electrode includes a positive electrode active material layer, a positive electrode current collector, and an insulating layer. The positive electrode active material layer extends in both the longitudinal and width directions. The positive electrode current collector includes a covered positive electrode region and an exposed positive electrode region.The covered positive electrode region is covered with the positive electrode active material layer. The exposed positive electrode region is not covered with the positive electrode active material layer and extends in the width direction from the positive electrode active material layer. The insulating layer extends longitudinally along a first edge of the positive electrode active material layer. The first edge is located at a boundary between the covered positive electrode region and the exposed positive electrode region. The positive electrode active material layer has a first thin part and a first thick part. The first thick part has a greater thickness than the first thin part and is adjacent to the first thin part in the width direction.

[0006] A battery pack according to an embodiment of the disclosure includes a secondary battery, a processor, and an outer case container. The processor is configured to control the secondary battery. The outer case container includes the secondary battery. The secondary battery includes an electrode winding case and an outer case container. The electrode winding case includes a stacked body and a through-hole. The stacked body includes a positive electrode, a negative electrode, and a separator, and is wound along a longitudinal direction of the stacked body. The through-hole is provided through the wound electrode body in a width direction orthogonal to the longitudinal direction. The outer case container contains the wound electrode body. The positive electrode includes a positive electrode active material layer, a positive electrode current collector, and an insulating layer.The positive electrode active material layer extends in both the longitudinal and width directions. The positive electrode current collector has a covered positive electrode region and an exposed positive electrode region. The covered positive electrode region is covered with the positive electrode active material layer. The exposed positive electrode region is not covered with the positive electrode active material layer and extends in the width direction from the positive electrode active material layer. The insulating layer extends longitudinally along a first edge of the positive electrode active material layer. The first edge is located at a boundary between the covered positive electrode region and the exposed positive electrode region. The positive electrode active material layer has a first thin part and a first thick part.The first thick part has a thickness greater than the thickness of the first thin part and is adjacent to the first thin part in the width direction. SHORT DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments and, together with the description, serve to explain the principles of the disclosure. Fig. 1 is a sectional diagram illustrating a configuration example of a vertical sectional structure of a secondary battery according to an exemplary embodiment of the disclosure along a height direction. Fig. 2 is a schematic diagram illustrating a configuration example of a stacked body having a positive electrode, a negative electrode, and a separator as shown in Fig. 1 shown. Fig. 3 is a sectional diagram illustrating a configuration example of a horizontal sectional structure of an electrode coil body as shown in Fig. 1 shown. Fig. 4A is a developed view of the Fig. 1 shown positive electrode. Fig. 4B is a first sectional view of the Fig. 1 shown positive electrode. Fig. 4C is a second sectional view of the Fig. 1 shown positive electrode. Fig. 5A is a developed view of the Fig. 1 shown negative electrode. Fig. 5B is a sectional view of the Fig. 1 shown negative electrode. Fig. Figure 6A is a plan view of a positive electrode current collector plate used in Fig. 1 is shown. Fig. Figure 6B is a plan view of a negative electrode current collector plate used in Fig. 1 is shown. Fig. 7A to 7F are perspective diagrams showing the manufacturing process of the Fig. Describe the secondary battery shown in Figure 1. Fig. 8 is a block diagram illustrating a circuit configuration of a battery pack to which the secondary battery according to an exemplary embodiment of the disclosure is applied. Fig. 9 is a sectional view of a positive electrode according to a first modification example of an exemplary embodiment of the disclosure. Fig. 10A is a sectional diagram illustrating a first example of a positive electrode according to a second modification example of an exemplary embodiment of the disclosure. Fig. 10B is a sectional diagram illustrating a second example of the positive electrode according to the second modification example of an exemplary embodiment of the disclosure. Fig. 10C is a sectional diagram illustrating a third example of the positive electrode according to the second modification example of an exemplary embodiment of the disclosure. Fig. 11A is a developed view of a positive electrode according to a third modification example of an exemplary embodiment of the disclosure. Fig. 11B is a sectional view of the Fig. 11A shown positive electrode. Fig. 12A is a developed view of a positive electrode of Example 1-1. Fig. Figure 12B is a sectional view of the positive electrode of Example 1-1. Fig. 13A is a developed view of a positive electrode of each of Examples 1-2 to 1-5. Fig. 13B is a sectional view of the positive electrode of each of Examples 1-2 to 1-5. Fig. 14A is a developed view of a positive electrode of each of Examples 1-6 to 1-9. Fig. 14B is a sectional view of the positive electrode of each of Examples 1-6 to 1-9. Fig. 15 is a sectional view of a positive electrode of Example 3-1. DETAILED DESCRIPTION

[0008] Various considerations have been made to improve the performance of a secondary battery. However, there is still room for improvement in secondary battery reliability.

[0009] It is desirable to provide a secondary battery having higher reliability and to provide a battery pack having such a secondary battery.

[0010] In the following, some embodiments of the disclosure will be described in detail with reference to the accompanying drawings. It is noted that the following description aims at illustrative examples of the disclosure and should not be construed as limiting the disclosure. Factors including, among others, numerical values, shapes, materials, components, positions of the components, and the manner in which the components are connected to each other are for illustrative purposes only and are not to be construed as limiting the disclosure. Furthermore, elements in the following embodiments that are not recited in a most general independent claim of the disclosure are optional and can be provided if necessary. The drawings are schematic and not to scale.In this description and the drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant description. Furthermore, elements not directly related to an embodiment of the disclosure are not shown in the drawings. The description is presented in the following order. 1. Secondary battery 1-1. Configuration 1-2. Operation 1-3. Manufacturing process 1-4. Action and exemplary effects 2. Application examples 2-1. Battery pack 2-2. Energy storage system 3. Modification examples [1. Secondary battery]

[0011] First, a secondary battery according to an exemplary embodiment of the disclosure will be described.

[0012] In the present exemplary embodiment, a cylindrical lithium-ion secondary battery having an external cylindrical shape is described as an example. However, a secondary battery of one embodiment of the disclosure is not limited to the cylindrical lithium-ion secondary battery and may be a lithium-ion secondary battery having an external shape other than the cylindrical shape, or a secondary battery using an electrode reactant other than lithium.

[0013] Although the principle of charging and discharging a secondary battery is not particularly limited, the following description deals with a case where the battery capacity is achieved by inserting and extracting the electrode reactant. The secondary battery may include a positive electrode, a negative electrode, and an electrolyte. In the secondary battery, to prevent the electrode reactant from precipitating on a surface of the negative electrode during charging, the charging capacity of the negative electrode may be larger than the discharging capacity of the positive electrode. For example, the electrochemical capacity per unit area of ​​the negative electrode may be set larger than the electrochemical capacity per unit area of ​​the positive electrode.

[0014] The electrode reactant is not particularly limited to any particular type, as described above. For example, the electrode reactant can be a light metal such as an alkali metal or an alkaline earth metal. Non-limiting examples of alkali metals include lithium, sodium, and potassium. Non-limiting examples of alkaline earth metals include beryllium, magnesium, and calcium.

[0015] The following describes a case where the electrode reactant is lithium as an example. A secondary battery in which the battery capacity is achieved by the intercalation and removal of lithium can be referred to as a lithium-ion secondary battery. In a lithium-ion secondary battery, lithium can be intercalated or inserted in an ionic state and removed or removed. [1-1. Configuration][Lithium-ion secondary battery 1]

[0016] Fig. Figure 1 shows a vertical sectional configuration of a lithium-ion secondary battery 1 according to the present embodiment along a height direction. The lithium-ion secondary battery 1 according to the present embodiment is hereinafter referred to simply as "secondary battery 1." Fig. The secondary battery 1 shown in FIG. 1 includes an outer case container 11 and an electrode coil 20. The outer case container 11 may have a substantially cylindrical shape. The electrode coil 20 is disposed within the outer case container 11 and may serve as a battery device. The secondary battery 1 may further include an outer case tube 50. The outer case tube 50 may cover an outer peripheral surface of the outer case container 11. Note that here, the height direction of the secondary battery 1 corresponds to a Z-axis direction.

[0017] For example, the secondary battery 1 may include, within the outer casing container 11, a pair of insulating plates 12 and 13, the electrode coil 20, a positive electrode current collector plate 24, and a negative electrode current collector plate 25. The electrode coil 20 may, for example, be a structure in which a positive electrode 21 and a negative electrode 22 are stacked and wound with a separator 23 interposed therebetween. The electrode coil 20 may be impregnated with an electrolyte solution. The electrolyte solution may be a liquid electrolyte. In some embodiments, the secondary battery 1 may further include a heat-sensitive resistance device, a reinforcing element, or both within the outer casing container 11. Examples of the heat-sensitive resistance device may include a positive temperature coefficient (PTC) device. [Outer housing container 11]

[0018] The outer housing container 11 may include components including, but not limited to, the positive electrode current collector plate 24, the negative electrode current collector plate 25, and the electrode bobbin 20. In some embodiments, the outer housing container 11 may include a bottom portion 11B and a sidewall portion 11W. The bottom portion 11B may also serve as a negative electrode terminal connected to the negative electrode 22 via the negative electrode current collector plate 25. The outer housing container 11 may, for example, have a hollow cylindrical structure with a lower end portion and an upper end portion in the Z-axis direction. The lower end portion may be closed, and the upper end portion may be open. The upper end portion of the outer housing container 11 may thus be an open end portion 11N.The lower end part of the outer housing container 11 may be closed by the bottom part 11B, which has a substantially circular plate shape. The side wall part 11W may be provided between the open end part 11N and the bottom part 11B and surround the electrode bobbin 20. The side wall part 11W may be positioned in the height direction, that is, in the width direction of the electrode bobbin 20, and along an outer edge of the bottom part 11B so as to surround the electrode bobbin 20. The side wall part 11W may have the open end part 11N on a side opposite to the bottom part 11B. The open end part 11N may be open to allow the electrode bobbin 20 to pass therethrough. The outer housing container 11 may comprise, for example, a metal material such as iron. In some embodiments, a surface of the outer housing container 11 may be plated with a metal material such as nickel.The insulating plate 12 and the insulating plate 13 may be opposed to each other such that the electrode coil body 20 can be interposed therebetween, for example, in the Z-axis direction. Note that here, the open end portion 11N and the vicinity thereof in the Z-axis direction may be referred to as the upper part of the secondary battery 1, and a region where the outer casing container 11 is closed and the vicinity thereof in the Z-axis direction may be referred to as the lower part of the secondary battery 1. The side wall portion 11W may correspond to a specific but non-limiting example of a "wall portion" in one embodiment of the disclosure. [Outer housing tube 50]

[0019] The outer package tube 50 may surround a side surface 11WS, which is an outer surface of the side wall portion 11W of the outer package container 11. In some embodiments, the outer package tube 50 may cover a bent portion 11P positioned at the upper end portion of the outer package container 11, as shown in Fig. 1. The bent portion 11P will be described later. In some embodiments, the outer casing tube 50 may cover a portion of a bottom surface 11BS, which is an outer surface of the bottom portion 11B of the outer casing container 11. The outer casing tube 50 may, for example, comprise a thermally shrinkable insulating film comprising a material such as a polyester-based resin, a polyamide-based resin, or a thermoplastic elastomer resin. [Disc 55]

[0020] A washer 55 may be provided in a gap between the outer casing tube 50 and the bent portion 11P of the outer casing container 11. The washer 55 may be an insulating ring member having an opening 55K at a central portion in a plane orthogonal to the height direction. A protrusion provided in a central portion of a battery cover 14 may be disposed in the opening 55K. The washer 55 may comprise a material such as black-modified polyphenylene ether. [Insulation plates 12 and 13]

[0021] Each of the insulating plates 12 and 13 may, for example, be a disc-shaped plate having a surface perpendicular to a central axis CL of the electrode winding body 20, ie a surface perpendicular to a Z-axis in Fig. 1. The insulating plates 12 and 13 can be arranged so that the electrode winding body 20 can be arranged therebetween. [Crimped structure 11R]

[0022] For example, at the open end portion 11N of the outer housing container 11, a structure may be provided in which the battery cover 14 and a safety valve mechanism 30 are crimped with a gasket 15 interposed therebetween, that is, a crimped structure 11R. The outer housing container 11 may be sealed by the battery cover 14, with the electrode coil body 20 and other components contained within the outer housing container 11. The crimped structure 11R may have the bent portion 11P, which serves as a so-called crimped portion. [Battery cover 14]

[0023] The battery cover 14 may, for example, be a closure element that closes the open end part 11N when the electrode winding body 20 and other components are contained within the outer housing container 11. The battery cover 14 may, for example, be an electrical conductor comprising a material similar to the material contained in the outer housing container 11. In some embodiments, the battery cover 14 may close the open end part 11N of the outer housing container 11 and be connected to the current collector plate 24 of the positive electrode. Therefore, the battery cover 14 may also serve as a positive electrode terminal connected to the positive electrode 21 via the positive electrode current collector plate 24. The central region of the battery cover 14 may, for example, protrude upward, i.e., in a +Z direction. As a result, a surrounding region, i.e.,For example, any portion of the battery cover 14 other than the central portion may be in contact with the safety valve mechanism 30. The battery cover 14 may correspond to a specific, but non-limiting, example of a "cover part" in one embodiment of the disclosure. [Poetry 15]

[0024] The gasket 15 may, for example, be a sealing member disposed between the bent portion 11P of the outer housing container 11 and the battery cover 14. The gasket 15 may seal a gap between the bent portion 11P and the battery cover 14. In some embodiments, a surface of the gasket 15 may be coated with a material such as asphalt. The gasket 15 may, for example, comprise one or more insulating materials. The insulating material is not particularly limited to any particular type, and non-limiting examples thereof may include a polymer material such as polybutylene terephthalate (PBT) or polypropylene (PP). In some embodiments, the insulating material may be polybutylene terephthalate.One reason for this is that this helps to enable sufficient sealing of the gap between the bent part 11P and the battery cover 14, wherein the outer housing container 11 and the battery cover 14 are electrically separated from each other. [Safety valve mechanism 30]

[0025] The safety valve mechanism 30 can be adapted to release the sealed state of the outer casing container 11, thereby releasing a pressure inside the outer casing container 11, i.e., an internal pressure of the outer casing container 11, when necessary, for example, upon an increase in the internal pressure of the outer casing container 11. Non-limiting examples of a cause of the increase in the internal pressure of the outer casing container 11 may include a gas generated due to a decomposition reaction of the electrolyte solution during charging and discharging. The internal pressure of the outer casing container 11 may also increase due to external heating. [Electrode winding body 20]

[0026] The electrode coil 20 may be arranged between the positive electrode current collector plate 24 and the negative electrode current collector plate 25. In some embodiments, the electrode coil 20 may have an upper end surface 41 and a lower end surface 42. The upper end surface 41 may face the positive electrode current collector plate 24 in the height direction, i.e., the width direction of the electrode coil 20. The lower end surface 42 may face the negative electrode current collector plate 25 in the height direction. The electrode coil 20 may be a power generation device that effects charging and discharging reactions and is arranged within the outer housing container 11. The electrode coil 20 may include the positive electrode 21, the negative electrode 22, the separator 23, and the electrolytic solution, i.e., a liquid electrolyte.The upper end surface 41 may correspond to a specific, but non-limiting, example of a "first end surface" in one embodiment of the disclosure. The lower end surface 42 may correspond to a specific, but non-limiting example of a "second end surface" in one embodiment of the disclosure.

[0027] Fig. 2 is a developed view of the electrode coil former 20 and schematically shows a portion of a stacked body S20. The stacked body S20 includes the positive electrode 21, the negative electrode 22, and the separator 23. In the stacked body S20, which corresponds to the electrode coil former 20 in the developed state, the positive electrode 21 and the negative electrode 22 may be stacked one on top of the other with the separator 23 interposed therebetween. The separator 23 may, for example, have two bases, i.e., a first separator part 23A and a second separator part 23B. The electrode coil former 20 may thus include the stacked body S20 having four layers. In the four-layered stacked body S20, the positive electrode 21, the first separator part 23A, the negative electrode 22, and the second separator part 23B may be stacked in sequence.The positive electrode 21, the first separator part 23A, the negative electrode 22 and the second separator part 23B may each be a substantially band-shaped member in which a W direction corresponds to a transverse direction and an L direction corresponds to a longitudinal direction.

[0028] As in Fig. As shown in Figure 3, the electrode winding body 20 may be the stacked body S20 wound around a through-hole 26 so as to extend along the central axis CL extending in the Z-axis direction, forming a spiral shape in a horizontal region orthogonal to the Z-axis direction. Here, the stacked body S20 may be wound in an orientation in which the W direction substantially coincides with the Z-axis direction. It is noted that in Fig. 3 shows a configuration example of the electrode winding body 20 along the horizontal area orthogonal to the Z-axis direction. It is noted that in Fig. 3, the illustration of the separator 23 has been omitted for clarity. The electrode winding body 20 may have an overall external appearance of a substantially circular columnar shape. The positive electrode 21 and the negative electrode 22 may be wound while being in a state of opposing each other with the separator 23 interposed therebetween. The electrode winding body 20 may have the through-hole 26 as an internal space at its center. The through-hole 26 may be a hole into which a winding core for assembling the electrode winding body 20 and an electrode rod for welding are inserted. The through-hole 26 may extend in the Z-axis direction along the central axis CL and is provided through the electrode winding body 20. The stacked body S20 may thus be wound around the through-hole 26.

[0029] The positive electrode 21, the negative electrode 22, and the separator 23 can be wound such that the separator 23 is positioned in an outermost turn of the electrode winding body 20 and an innermost turn of the electrode winding body 20. In the outermost turn of the electrode winding body 20, the negative electrode 22 can be positioned on an outer side relative to the positive electrode 21. For example, as shown in Fig. 3, an outermost turn part 21out of the positive electrode 21, which is positioned in an outermost turn of the positive electrode 21 contained in the electrode winding body 20, is positioned on an inner side relative to an outermost turn part 22out of the negative electrode 22, which is positioned in an outermost turn of the negative electrode 22 arranged in the electrode winding body 20. Here, the outermost turn part 21out of the positive electrode 21 may be a part corresponding to the outermost turn of the positive electrode 21 in the electrode winding body 20. The outermost turn part 22out of the negative electrode 22 may be a part corresponding to the outermost turn part of the negative electrode 22 in the electrode winding body 20. In contrast, in the innermost turn part of the electrode winding body 20, the negative electrode 22 may be positioned on the inner side relative to the positive electrode 21. For example, as shown in Fig. 3, an innermost winding part 22 in the negative electrode 22 positioned in an innermost turn of the negative electrode 22 included in the electrode coil body 20 may be positioned on the inner side relative to an innermost winding part 21 in the positive electrode 21 positioned in an innermost turn of the positive electrode 21 included in the electrode coil body 20. Here, the innermost winding part 21 in the positive electrode 21 may be a part corresponding to the innermost turn of the positive electrode 21 in the electrode coil body 20. The innermost winding part 22 in the negative electrode 22 may be a part corresponding to the innermost turn of the negative electrode 22 in the electrode coil body 20. The number of turns of each of the positive electrode 21, the negative electrode 22, and the separator 23 is not particularly limited and can be selected as desired.

[0030] Fig. Fig. 4A is a developed view of the positive electrode 21 and schematically shows a state before winding. Fig. 4B and Fig. 4C each show a sectional configuration of the positive electrode 21. Note that in FIG. 4B, a portion in the arrow direction along the line IVB-IVB shown in FIG. 4A is shown. FIG. 4C shows a portion in the arrow direction along the line IVC-IVC shown in FIG. 4A. The positive electrode 21 includes a positive electrode current collector 21A, a positive electrode active material layer 21B, and an insulating layer 101. The positive electrode active material layer 21B may, for example, be simply provided on one of two opposite surfaces of the positive electrode current collector 21A or on each of the two opposite surfaces of the positive electrode current collector 21A. Fig. 4B shows an example case where the positive electrode active material layer 21B is provided on each of the two opposite surfaces of the positive electrode current collector 21A. In some embodiments, the positive electrode current collector 21A may have an inward-facing surface 21A1 facing the central axis CL and an outward-facing surface 21A2 located on a side opposite the inward-facing surface 21A1. In some embodiments, the positive electrode 21 may have an inner coil-side positive electrode active material layer 21B1 and an outer coil-side positive electrode active material layer 21B2 as the positive electrode active material layers 21B. The inner coil-side positive electrode active material layer 21B1 may cover all or part of the inner surface 21A1 of the positive electrode current collector 21A.The outer coil-side positive electrode active material layer 21B2 may cover all or part of the outer surface 21A2 of the positive electrode current collector 21A. Herein, the inner coil-side positive electrode active material layer 21B1 and the outer coil-side positive electrode active material layer 21B2 may each be generically referred to as the positive electrode active material layer 21B without distinction between them. The positive electrode active material layer 21B extends in both the L direction and the W direction orthogonal to the L direction. The L direction corresponds to a longitudinal direction of the positive electrode 21. The W direction corresponds to a width direction of the positive electrode 21. The L direction corresponds to a winding direction of the stacked body S20. The W direction substantially coincides with the central axis CL.The inner coil-side positive electrode active material layer 21B1 may correspond to a specific but non-limiting example of a "first positive electrode active material layer" in one embodiment of the disclosure. The outer coil-side positive electrode active material layer 21B2 may correspond to a specific but non-limiting example of a "second positive electrode active material layer" in one embodiment of the disclosure.

[0031] The positive electrode current collector 21A includes a covered positive electrode region 211 and an exposed positive electrode region 212. The covered positive electrode region 211 is covered with the positive electrode active material layer 21B. The exposed positive electrode region 212 is not covered with the positive electrode active material layer 21B and extends in the W direction. The insulating layer 101 extends in the L direction and along a first edge 21BT1 of the positive electrode active material layer 21B. The first edge 21BT1 is positioned at a boundary K between the covered positive electrode region 211 and the exposed positive electrode region 212. It is noted that in the positive electrode 21 of the present embodiment, the first edge 21BT1 of the positive electrode active material layer 21B may be part of an inclined surface, and the insulating layer 101 may be in contact with the first edge 21BT1, as shown in Fig. 4B. For example, the insulating layer 101 may cover the first edge 21BT1 of the positive electrode active material layer 21B and its surroundings. The positive electrode active material layer 21B includes a thin part 61 and a thick part 71. In some embodiments, the positive electrode active material layer 21B may further include thick parts 72 and 73. In the positive electrode 21 of the present embodiment, both the thin part 61 and the thick parts 71 to 73 may be provided on the inner surface 21A1 and the outer surface 21A2 of the positive electrode current collector 21A, respectively. In other words, each of the inner coil-side positive electrode active material layers 21B1 and the outer coil-side positive electrode active material layers 21B2 may include the thin part 61 and the thick parts 71 to 73, respectively.However, in some embodiments, in the positive electrode 21, at least one of the inner coil-side positive electrode active material layer 21B1 and the outer coil-side positive electrode active material layer 21B2 may include the thin part 61 and the thick parts 71 to 73. It is noted that in FIGS. Fig. 4B and Fig. 4C, for the sake of simplicity, the thin part 61 and the thick parts 71, 72, and 73 included in the inner coil-side positive electrode active material layer 21B1 are referred to as thin part 61-1 and thick parts 71-1, 72-1, and 73-1, respectively; and the thin part 61 and the thick parts 71, 72, and 73 included in the outer coil-side positive electrode active material layer 21B2 are referred to as thin part 61-2 and thick parts 71-2, 72-2, and 73-2, respectively. Furthermore, in the Fig. 4C, a position of a boundary 21B1K between the thin part 61-1 and the thick part 73-1 in the L direction may substantially correspond to a position of a boundary 21B2K between the thin part 61-2 and the thick part 73-2 in the L direction. The thin part 61 may correspond to a specific but non-limiting example of a "first thin part" in an embodiment of the disclosure. The thick part 71 may correspond to a specific but non-limiting example of a "first thick part" in an embodiment of the disclosure. The thick part 72 may correspond to a specific but non-limiting example of a "second thick part" in an embodiment of the disclosure. The thick part 73 may correspond to a specific but non-limiting example of a "third thick part" in an embodiment of the disclosure.Boundary 21B1K may correspond to a specific, but non-limiting, example of a "first boundary" in an embodiment of the disclosure. Boundary 21B2K may correspond to a specific, but non-limiting example of a "second boundary" in an embodiment of the disclosure.

[0032] The thick part 71 has a greater thickness than the thin part 61. In some embodiments, each of the thick parts 72 and 73 may have a greater thickness than the thin part 61. For example, the thickness of the thin part 61 may be about half the thickness of each of the thick parts 71 to 73. The respective thicknesses of the thick parts 71 to 73 may be the same or different. For example, as shown in each of the Fig. 4B and Fig. 4C, in the inner coil-side positive electrode active material layer 21B1, a thickness T71-1 of the thick part 71-1, a thickness T72-1 of the thick part 72-1, and a thickness T73-1 of the thick part 73-1 may each be greater than a thickness T61-1 of the thin part 61-1. It is noted that in the Fig. 4B and Fig. 4C, the thickness T71-1 of the thick part 71-1, the thickness T72-1 of the thick part 72-1, and the thickness T73-1 of the thick part 73-1 may be equal. Similarly, in the outer coil-side positive electrode active material layer 21B2, each of the thickness T71-2 of the thick part 71-2, a thickness T72-2 of the thick part 72-2, and a thickness T73-2 of the thick part 73-2 may be greater than a thickness T61-2 of the thin part 61-2. It is noted that in the embodiment shown in Fig. 4B and Fig. 4C, the thickness T71-2 of the thick part 71-2, the thickness T72-2 of the thick part 72-2, and the thickness T73-2 of the thick part 73-2 may be the same. The thickness T61-1 and the thickness T61-2 may be the same or different. The thickness T71-1 and the thickness T71-2 may be the same or different. The thickness T72-1 and the thickness T72-2 may be the same or different. The thickness T73-1 and the thickness T73-2 may be the same or different. In addition, a length of the thick part 73 may be greater than a length of each of the thick parts 71 and 72 in the width direction of the positive electrode 21.

[0033] In some embodiments, the thin part 61 may include a winding center side edge 21E1 of the positive electrode 21, that is, an edge of the positive electrode 21 on one side of the winding center in the L direction. In some embodiments, the thin part 61 may have a length in the L direction corresponding, for example, to about one turn to about five turns of the electrode winding body 20 from the winding center side edge 21E1. The thick part 71 is adjacent to the thin part 61 in the W direction. In some embodiments, the thick part 71 may be positioned between the thin part 61 and the insulating layer 101 in the W direction. In some embodiments, the thick part 71 may include the first edge 21BT1 and be in contact with the insulating layer 101. The thick part 72 may have a second edge 21BT2 arranged on a side opposite to the first edge 21BT1 in the W direction.The thick part 73 may be disposed on a side of the thin part 61 opposite the coil center side edge 21E1 in the L direction. In some embodiments, the thick parts 71 to 73 may be separated from each other. In some embodiments, all or part of the thick parts 71 to 73 may be integrated with each other. Each of the thick parts 71 and 72 may include the coil center side edge 21E1 of the positive electrode 21 in the L direction.

[0034] Fig. 4A shows that the positive electrode covered region 211 and the positive electrode exposed region 212 each extend along the L direction from the winding center side edge 21E1 of the positive electrode 21 to a winding outer side edge 21E2 of the positive electrode 21, that is, an edge of the positive electrode 21 on a winding outer side in the L direction of the positive electrode 21. In other words, in the positive electrode 21, the positive electrode current collector 21A may be covered with the positive electrode active material layer 21B from the winding center side edge 21E1 of the positive electrode 21 to the winding outer side edge 21E2 of the positive electrode 21 in the winding direction of the electrode bobbin 20. The covered positive electrode region 211 and the exposed positive electrode region 212 may be adjacent to each other in the W direction. It is noted that the Fig. 4A and Fig. 4B each schematically illustrate the positive electrode current collector 21A in a directed state along the W direction. In fact, however, as shown in Fig. 1, a positive electrode edge portion 212E of the positive electrode exposed region 212 may be bent in the direction of the central axis CL and connected to the positive electrode current collector plate 24. In some embodiments, an end portion of the positive electrode exposed region 212 in the W direction may form the upper end surface 41 and be connected to the positive electrode current collector plate 24, as shown in Fig. 1. In some embodiments, the upper end surface 41 may have the positive electrode edge portion 212E of the positive electrode exposed region 212 bent toward the through-hole 26 in a state where the stacked body S20 is wound.

[0035] In some embodiments, the insulating layer 101 may be provided in a region including the boundary K between the covered positive electrode region 211 and the exposed positive electrode region 212 and the vicinity of the boundary K. In some embodiments, the insulating layer 101 may also extend from the coil center side edge 21E1 to the coil outer side edge 21E2 in the electrode winding body 20, as in the covered positive electrode region 211 and the exposed positive electrode region 212. In some embodiments, the insulating layer 101 may adhere to the first separator part 23A, the second separator part 23B, or both. One reason for this is that this helps prevent misalignment of the positive electrode 21 and the separator 23 with each other. In some embodiments, the insulating layer 101 may comprise a resin containing polyvinylidene difluoride (PVDF).One reason for this is that the insulating layer 101, if it comprises PVDF, is swollen, for example, by a solvent contained in the electrolyte solution, whereby the insulating layer 101 can advantageously adhere to the separator 23.

[0036] Fig. 5A is a developed view of the negative electrode 22 and schematically illustrates a state before winding. Fig. Figure 5B shows a sectional configuration of the negative electrode 22. It is noted that Fig. 5B an area in the direction of the arrow along a Fig. 5A. In some embodiments, the negative electrode 22 may include, for example, a negative electrode current collector 22A and a negative electrode active material layer 22B. The negative electrode active material layer 22B may cover a portion of the negative electrode current collector 22A. In some embodiments, the negative electrode active material layer 22B may simply be provided on one of two opposite surfaces of the negative electrode current collector 22A. In some embodiments, the negative electrode active material layer 22B may be provided on each of the two opposite surfaces of the negative electrode current collector 22A. Fig. 5B shows an example case where the negative electrode active material layer 22B is provided on each of the two opposite surfaces of the negative electrode current collector 22A. For example, the negative electrode current collector 22A may have an inward-facing surface 22A1 facing the central axis CL and an outward-facing surface 22A2 located on a side opposite the inward-facing surface 22A1. The negative electrode 22 may have an inner coil-side negative electrode active material layer 22B1 and an outer coil-side negative electrode active material layer 22B2 as the negative electrode active material layers 22B. The inner coil-side negative electrode active material layer 22B1 may cover all or part of the inner surface 22A1 of the negative electrode current collector 22A.The outer coil-side negative electrode active material layer 22B2 may cover all or part of the outer surface 22A2 of the negative electrode current collector 22A. Herein, the inner coil-side negative electrode active material layer 22B1 and the outer coil-side negative electrode active material layer 22B2 may each be generically referred to as the negative electrode active material layer 22B, without distinguishing between them.

[0037] In some embodiments, the negative electrode 22 may include a covered negative electrode region 221 and an exposed negative electrode region 222. The covered negative electrode region 221 may be a region in which the negative electrode current collector 22A is covered with the negative electrode active material layer 22B. The exposed negative electrode region 222 may be a region in which the negative electrode current collector 22A is not covered with the negative electrode active material layer 22B and is exposed. As shown in Fig. 5A, the covered negative electrode region 221 and the exposed negative electrode region 222 may each extend along the L direction, that is, a longitudinal direction of the negative electrode 22. The exposed negative electrode region 222 may extend from a winding center side edge 22E1 of the negative electrode 22, that is, an edge of the negative electrode 22 on the winding center side (or winding center side), to a winding outer peripheral side edge 22E2 of the negative electrode 22, that is, an edge of the negative electrode 22 on the winding outer peripheral side (or winding outer peripheral side), in the winding direction of the wound electrode body 20. In contrast, the covered negative electrode region 221 may also be provided neither on the coil center side edge 22E1 nor on the coil outer peripheral side edge 22E2. As shown in Fig. 5A, portions of the negative electrode exposed region 222 may be provided such that the covered negative electrode region 221 may be disposed therebetween in the L direction. For example, the negative electrode exposed region 222 may include a first part 222A, a second part 222B, and a third part 222C. The negative electrode 22 may further include a lower edge 22E3 extending in the L direction on a lower side of the electrode winding body 20. The first part 222A may be adjacent to the covered negative electrode region 221 in the W direction and extend in the L direction from the winding center side edge 22E1 of the negative electrode 22 to the winding outer peripheral side edge 22E2 of the negative electrode 22. In other words, the first part 222A may be a region extending from the negative electrode active material layer 22B in the W direction.The second part 222B and the third part 222C may be provided such that the negative electrode covered region 221 can be sandwiched therebetween in the L direction. The first part 222A may be positioned in a region including the lower edge 22E3 and its vicinity in the negative electrode 22. For example, the second part 222B may be positioned in a region including the coil center side edge 22E1 and its vicinity in the negative electrode 22, and the third part 222C may be positioned in a region including the coil outer peripheral side edge 22E2 and its vicinity in the negative electrode 22. It is noted that the . Fig. 5A and Fig. 5B each schematically illustrate the negative electrode current collector 22A in the straightened state along the W direction. In fact, however, as shown in Fig. 1, a negative electrode edge portion 222E of the exposed negative electrode region 222 may be bent toward the central axis CL and connected to the negative electrode current collector plate 25. In some embodiments, an end portion of the exposed negative electrode region 222 in the W direction may form the lower end surface 42 and be connected to the negative electrode current collector plate 25, as shown in Fig. 1. In some embodiments, the lower end surface 42 may include the negative electrode edge portion 222E of the negative electrode exposed region 222 bent toward the through-hole 26 in a state where the stacked body S20 is wound.

[0038] In the stacked body S20 of the electrode coil body 20, the positive electrode 21 and the negative electrode 22 may be stacked or layered with the separator 23 interposed therebetween, such that the positive electrode exposed portion 212 and the first part 222A of the negative electrode exposed portion 222 face opposite directions along the W direction. In the electrode coil body 20, an end portion of the separator 23 may be fixed by attaching a fixing tape 46 to a side surface portion 45 of the electrode coil body 20, thereby preventing winding loosening.

[0039] In some embodiments, the secondary battery 1 may be as shown in Fig. 2, satisfy the condition A>B, where A is the width of the positive electrode exposed region 212 and B is the width of the first part 222A of the negative electrode exposed region 222. For example, when the width A is 7 (mm), the width B may be 4 (mm). In some embodiments, the secondary battery 1 may satisfy the condition C>D, where C is the width of a portion of the positive electrode exposed region 212 that protrudes from an outer edge in the width direction of the separator 23, and D is the width of a portion of the first part 222A of the negative electrode exposed region 222 that protrudes from an opposite outer edge in the width direction of the separator 23. For example, when the width C is 4.5 (mm), the width D may be 3 (mm).

[0040] As in Fig. 1, in the upper part of the secondary battery 1, a plurality of portions of the positive electrode edge part 212E of the positive electrode exposed region 212 wound around the central axis CL, which are adjacent to each other in a radial direction, i.e., an R direction, of the electrode bobbin 20, may be bent toward the central axis CL so as to overlap each other. The portions of the positive electrode edge part 212E may thus form the upper end surface 41 of the electrode bobbin 20. Similarly, in the lower part of the secondary battery 1, a plurality of portions of the negative electrode edge part 222E of the negative electrode exposed region 222 wound around the central axis CL, which are adjacent to each other in a radial direction, i.e., an R direction, may be bent toward the central axis CL so as to overlap each other. The portions of the negative electrode edge part 222E can thus form the lower end surface 42 of the electrode winding body 20.Accordingly, the portions of the positive electrode edge part 212E of the positive electrode exposed region 212 can gather at the upper end surface 41 of the electrode coil body 20, and the portions of the negative electrode edge part 222E of the negative electrode exposed region 222 can gather at the lower end surface 42 of the electrode coil body 20. To achieve better contact between the positive electrode current collector plate 24 for discharging a current and the positive electrode edge part 212E, the portions of the positive electrode edge part 212E bent toward the central axis CL can form a flat surface. Similarly, in order to achieve better contact between the negative electrode current collector plate 25 for discharging a current and the negative electrode edge part 222E, the portions of the negative electrode edge part 222E bent toward the central axis CL may form a flat surface.It is noted that the term “flat surface” used herein may mean not only a completely flat surface, but also a surface having some unevenness or surface roughness to such an extent that connection of the positive electrode exposed portion 212 to the positive electrode current collector plate 24 and connection of the negative electrode exposed portion 222 to the negative electrode current collector plate 25 are possible.

[0041] The positive electrode current collector 21A may include an electrically conductive foil, such as aluminum foil, as described later. The negative electrode current collector 22A may include an electrically conductive foil, such as copper foil, as described later. In this case, the positive electrode current collector 21A may be softer than the negative electrode current collector 22A. For example, the positive electrode exposed region 212 may have a Young's modulus lower than the Young's modulus of the negative electrode exposed region 222. Accordingly, in some embodiments, the secondary battery 1 may satisfy both A>B and C>D with respect to the widths A to D.In such a case, when the positive electrode exposed region 212 and the negative electrode exposed region 222 are bent substantially simultaneously with substantially equal pressures from both electrode sides, the bent portion in the positive electrode 21 and the bent portion in the negative electrode 22 may sometimes be substantially equal in height as measured from the respective ends of the separator 23. In this case, the portions of the positive electrode edge part 212E of the positive electrode exposed region 212 shown in FIG. Fig. 1, overlap each other by bending in a suitable manner. This contributes to the easy bonding of the positive electrode exposed region 212 and the positive electrode current collector plate 24. Similarly, the portions of the negative electrode edge part 222E of the negative electrode exposed region 222, as shown in Fig. 1, overlap each other accordingly by bending. This contributes to the easy bonding of the exposed negative electrode region 222 and the negative electrode current collector plate 25. As used herein, the term "bonding" may refer to coupling by, for example, laser welding; however, a bonding method is not limited to laser welding. In some embodiments, any other coupling method may be used.

[0042] As in Fig. As shown in Figure 2, a portion of the covered positive electrode region 212 of the positive electrode 21, which faces the negative electrode 22 with the separator 23 interposed therebetween, may be covered with the insulating layer 101. The insulating layer 101 may, for example, have a width of 3 mm in the W direction. The insulating layer 101 may completely cover a portion of the exposed positive electrode region 212 of the positive electrode 21, which faces the covered negative electrode region 221 of the negative electrode 22 with the separator 23 interposed therebetween. The insulating layer 101 contributes to effectively preventing an internal short circuit of the secondary battery 1 when, for example, foreign matter gets between the covered negative electrode region 221 and the exposed positive electrode region 212.In addition, the insulating layer 101 absorbs the impact when the secondary battery 1 is subjected to an impact, thus contributing to effectively preventing, for example, bending of the positive electrode exposed portion 212 or a short circuit between the positive electrode exposed portion 212 and the negative electrode 22. [Insulating tapes 53 and 54]

[0043] In some embodiments, the secondary battery 1 may further include insulating tapes 53 and 54 in a gap between the outer casing container 11 and the electrode winding body 20. The exposed positive electrode region 212 with portions on the upper facing end surface 41 and the exposed negative electrode region 222 with portions on the lower facing end surface 42 may be electrical conductors, such as metal foils, that are exposed. If the exposed positive electrode region 212 and the exposed negative electrode region 222 are in close proximity to the outer casing container 11, a short circuit may occur between the positive electrode 21 and the negative electrode 22 via the outer casing container 11. A short circuit may also occur if the positive electrode current collector plate 24 at the upper end surface 41 and the outer casing container 11 are close to each other.To remedy this, in some embodiments, insulating tapes 53 and 54 may be provided as insulating members. Each of the insulating tapes 53 and 54 may be an adhesive tape comprising a base layer and an adhesive layer provided on a surface of the base layer. The base layer may comprise, for example, polypropylene, polyethylene terephthalate, or polyimide. To prevent the provision of the insulating tapes 53 and 54 from resulting in reduced capacitance of the electrode winding body 20, the insulating tapes 53 and 54 may be arranged so as not to overlap the fixing tape 46 attached to the side surface part 45, and may each have a thickness less than or equal to the thickness of the fixing tape 46. [Positive electrode current collector plate 24 and negative electrode current collector plate 25]

[0044] For example, in an existing lithium-ion secondary battery, a terminal for current extraction is welded to one position each of a positive electrode and a negative electrode. However, such a structure increases the internal resistance of the lithium-ion secondary battery, causing the lithium-ion secondary battery to generate heat and become hot during discharge; therefore, the structure is unsuitable for high-rate discharge. To solve this, in the secondary battery 1 according to the present embodiment, the positive electrode current collector plate 24 may be arranged to face the upper end surface 41, and the negative electrode current collector plate 25 may be arranged to face the lower end surface 42.Additionally, the exposed positive electrode portion 212 forming the upper end surface 41 and the positive electrode current collector plate 24 may be welded together at multiple points; and the exposed negative electrode portion 222 forming the lower end surface 42 and the negative electrode current collector plate 25 may be welded together at multiple points. This contributes to a reduced internal resistance of the secondary battery 1. Each of the upper end surface 41 and the lower end surface 42, which has a flat surface as described above, also contributes to the reduced resistance. In some embodiments, the positive electrode current collector plate 24 may be positioned between the battery cover 14 and the upper end surface 41. The positive electrode current collector plate 24 may be electrically coupled to the battery cover 14, for example, via the safety valve mechanism 30.In some embodiments, the negative electrode current collector plate 25 may be positioned between the bottom portion 11B of the outer housing container 11 and the lower end surface 42. For example, the negative electrode current collector plate 25 may be electrically connected to an inner surface of the bottom portion 11B of the outer housing container 11. Fig. 6A is a developed view illustrating a configuration example of the positive electrode current collector plate 24. Fig. 6B is a developed view illustrating a configuration example of the negative electrode current collector 25. The positive electrode current collector plate 24 may be a metal plate including, for example, but not limited to, aluminum or an aluminum alloy as a single component, or a composite material of aluminum and the aluminum alloy. The negative electrode current collector plate 25 may be a metal plate including, for example, but not limited to, nickel, a nickel alloy, copper, or a copper alloy as a single component, or a composite material of two or more thereof.

[0045] As in Fig. 6A, the positive electrode current collector plate 24 may have a fan-shaped portion 31 and a band-shaped portion 32. The fan-shaped portion 31 may have a substantially fan-shaped shape. The band-shaped portion 32 may have a substantially rectangular shape. However, the shape of the positive electrode current collector plate 24 is not limited to the shape shown in Fig. 6A and can be selected as desired. It is noted that in the secondary battery 1, the positive electrode current collector plate 24 is arranged within the outer casing container 11 as shown in Fig. 1, in a state in which the band-shaped part 32 is bent with respect to the fan-shaped part 31. Fig. 6A shows the positive electrode current collector plate 24 in an unbent state. The fan-shaped portion 31 may be a facing portion facing and connected to the upper end surface 41. The fan-shaped portion 31 may have an outer edge, for example, including a linear portion and a curved portion. The fan-shaped portion 31 may have an opening 35 near its center. Fig. 6A shows an example case where the opening 35 has a circular plan shape in a horizontal plane orthogonal to the Z-axis direction. The band-shaped part 32 may, for example, be connected to the linear part of the outer edge of the fan-shaped part 31. The band-shaped part 32 may extend in a direction that intersects the linear part of the fan-shaped part 31. As shown in Fig. As shown in Figure 1, in the secondary battery 1, the positive electrode current collector plate 24 may be provided such that the opening 35 may overlap the through-hole 26 in the Z-axis direction. For example, the opening 35 may be positioned such that it overlaps a portion of the upper end surface 41 on the winding center side in the Z-axis direction.

[0046] A hatched section in Fig. 6A illustrates an insulating part 32A of the band-shaped part 32. The insulating part 32A may be a portion of the band-shaped part 32 and may have an insulating tape or an insulating material applied thereto. A portion of the band-shaped part 32 below the insulating part 32A may be a coupling part 32B, which is coupled to a sealing plate that also serves as an external terminal. The sealing plate may be electrically continuously connected to the battery cover 14. It is noted that when the secondary battery 1 has a battery structure without a metallic center pin in the through-hole 26, as shown in Fig. 1, the probability that the band-shaped part 32 comes into contact with a region of negative electrode potential is low. In such a case, the positive electrode current collector plate 24 does not need to include the insulating part 32A. If the positive electrode current collector plate 24 does not include the insulating part 32A, the charging and discharging capacity can be increased by increasing the width of the positive electrode 21 and the negative electrode 22 by an amount corresponding to the thickness of the insulating part 32A.

[0047] The Fig. The negative electrode current collector plate 25 shown in Fig. 6B may have a similar shape to that shown in Fig. 6A. The negative electrode current collector plate 25 may have a fan-shaped part 33 and a band-shaped part 34. The fan-shaped part 33 may have a substantially fan-shaped configuration. The band-shaped part 34 may have a substantially rectangular configuration. However, the shape of the negative electrode current collector plate 25 is not limited to the configuration shown in Fig. 6B and can be chosen arbitrarily. It is noted that in the secondary battery 1, the negative electrode current collector plate 25 is arranged within the outer casing container 11 as shown in Fig. 1, in a state in which the band-shaped part 34 is bent with respect to the fan-shaped part 33. Fig. 6B illustrates the negative electrode current collector plate 25 in an unbent state. The fan-shaped part 33 may be a facing part facing and connected to the lower end surface 42. The fan-shaped part 33 may have an outer edge including, for example, a linear part and a curved part. The band-shaped part 34 may be connected, for example, to the linear part of the outer edge of the fan-shaped part 33. The band-shaped part 34 may extend in a direction intersecting the linear part of the fan-shaped part 33. The band-shaped part 34 of the negative electrode current collector plate 25 may be shorter than the band-shaped part 32 of the positive electrode current collector plate 24 and may not have a portion corresponding to the insulating part 32A of the positive electrode current collector plate 24. The band-shaped part 34 may be provided with projections 37, which are shown as circles.The protrusions 37 may each be round. All or part of the protrusions 37 may be welded to the bottom part 11B of the outer casing container 11. During resistance welding, a current may be concentrated on the protrusions 37, thereby melting the protrusions 37 and welding the band-shaped part 34 to the bottom part 11B of the outer casing container 11. Like the positive electrode current collector plate 24, the negative electrode current collector plate 25 may also have an opening 36 near the center of the fan-shaped part 33. In the secondary battery 1, the negative electrode current collector plate 25 may be provided so that the opening 36 overlaps the through-hole 26 in the Z-axis direction. Fig. 6B shows an example case in which the opening 36 has a circular plan shape in a horizontal plane orthogonal to the Z-axis direction.

[0048] The fan-shaped part 31 of the positive electrode current collector plate 24 can easily cover a portion of the upper end surface 41 due to the planar shape of the fan-shaped part 31. Similarly, the fan-shaped part 33 of the negative electrode current collector plate 25 can easily cover a portion of the lower end surface 42 due to the planar shape of the fan-shaped part 33. Reasons why the fan-shaped part 31 and the fan-shaped part 33 do not cover the entire upper end surface 41 and the entire lower end surface 42, respectively, include the following exemplary reasons. One reason is that, for example, the electrolyte solution can freely penetrate into the electrode bobbin 20 during assembly of the secondary battery 1.In the secondary battery 1 according to the present embodiment, the positive electrode current collector plate 24 may be provided such that the opening 35 overlaps a portion of the upper end surface 41 on the coil center side in the Z-axis direction. Accordingly, some of the portions of the positive electrode edge part 212E constituting the upper end surface 41 may not be covered by the fan-shaped part 31 of the positive electrode current collector plate 24 and may be exposed by the opening 35. The secondary battery 1 can thus have a structure that allows faster permeation of the electrolyte solution into the electrode coil body 20. Another reason is that a gas generated when the lithium-ion secondary battery enters an abnormally hot state or an overcharged state is easily discharged to the outside. [Positive electrode current collector 21A]

[0049] The positive electrode current collector 21A may comprise an electrically conductive material such as aluminum. The positive electrode current collector 21A may be a metal foil containing a material such as aluminum or an aluminum alloy. [Positive electrode active material layer 21B]

[0050] The positive electrode active material layer 21B may include, as the positive electrode active material, one or more of the positive electrode materials into which lithium is intercalatable / insertable and from which lithium is intercalatable / extractable. It is noted that in some embodiments, the positive electrode active material layer 21B may further include one or more other materials, including, but not limited to, a positive electrode binder and a positive electrode conductor. In some embodiments, the positive electrode material may be a lithium-containing compound. In some embodiments, the lithium-containing compound may be, for example, a lithium-containing composite oxide or a lithium-containing phosphoric acid compound. The lithium-containing composite oxide may be an oxide containing lithium and one or more other elements, that is, one or more elements other than lithium, as constituents.The lithium-containing composite oxide may have any crystal structure, including, but not limited to, a layered rock salt crystal structure and a spinel crystal structure. The lithium-containing phosphoric acid compound may be a phosphoric acid compound containing lithium and one or more other elements as constituents. The lithium-containing phosphoric acid compound may have a crystal structure such as an olivine crystal structure. In some embodiments, the positive electrode active material layer 21B may include, as the positive electrode active material, at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt silicate. The positive electrode binder may include, for example, one or more of materials including, but not limited to, a synthetic rubber and a polymer compound.Non-limiting examples of synthetic rubber may include, but are not limited to, styrene-butadiene-based rubber, fluorine-based rubber, and ethylene-propylene-diene rubber. Non-limiting examples of polymer compounds may include, but are not limited to, polyvinylidene difluoride and polyimide. For example, the positive electrode conductor may comprise one or more materials, including, but not limited to, a carbon material. Non-limiting examples of the carbon material may include graphite, carbon black, acetylene black, and Ketjen black. It is noted that in some embodiments, the positive electrode may be made of any electrically conductive material and may, for example, be a metallic material or an electrically conductive polymer. [Negative electrode current collector 22A]

[0051] The negative electrode current collector 22A may comprise an electrically conductive material such as copper. The negative electrode current collector 22A may be a metal foil comprising a material such as nickel, a nickel alloy, copper, or a copper alloy. In some embodiments, a surface of the negative electrode current collector 22A may be roughened. One reason for this is that this contributes to improving the adhesion of the negative electrode active material layer 22B to the negative electrode current collector 22A due to a so-called anchor effect. In this case, in some embodiments, the surface of the negative electrode current collector 22A may be roughened at least in a region facing the negative electrode active material layer 22B. Non-limiting examples of a roughening method may include a method in which microparticles are formed by an electrolytic treatment.During electrolytic treatment, the microparticles can be formed on the surface of the negative electrode current collector 22A by an electrolytic process in an electrolyzer. This can provide the surface of the negative electrode current collector 22A with unevenness. A copper foil produced by the electrolytic process can be generally referred to as an electrolytic copper foil. [Negative electrode active material layer 22B]

[0052] The negative electrode active material layer 22B may include, as the negative electrode active material, one or more negative electrode materials into which lithium can be incorporated / inserted and from which lithium can be extracted / removed. Note that in some embodiments, the negative electrode active material layer 22B may further include one or more other materials, including, but not limited to, a negative electrode binder and a negative electrode conductor. The negative electrode material may be an electrically conductive material such as a carbon material. One reason for this is that the carbon material exhibits very little change in crystal structure at the time of lithium insertion / inclusion and extraction / extraction, which contributes to stably maintaining a high energy density.Another reason is that the carbon material also serves as a negative electrode conductor, which contributes to improving the electrically conductive property of the negative electrode active material layer 22B. The carbon material may be, for example, but not limited to, graphitizable carbon, non-graphitizable carbon, or graphite. In some embodiments, the pitch of a (002) plane of the non-graphitizable carbon may be 0.37 nm or greater. In some embodiments, the pitch of a (002) plane of the graphite may be 0.34 nm or less. Non-limiting examples of the carbon material may include pyrolytic carbons, coke, glassy carbon fibers, a fired body of an organic polymer compound, activated carbon, and carbon black. Non-limiting examples of the coke may include pitch coke, needle coke, and petroleum coke.The fired body of an organic polymer compound can be formed by firing or carbonizing a polymer compound such as a phenolic resin or a furan resin at an appropriate temperature. Apart from the above, the carbon material may be low-crystalline carbon heat-treated at a temperature of about 1000°C or less, or it may be, for example, amorphous carbon. It should be noted that the carbon material may have a fibrous shape, a spherical shape, a granular shape, or a flaky shape. In the secondary battery 1, when the open-circuit voltage in the fully charged state, that is, the battery voltage, is 4.25 V or higher, the amount of extracted lithium per unit mass may increase compared to an open-circuit voltage in the fully charged state of 4.20 V, even if the positive electrode active material of the positive electrode remains the same.The amount of positive electrode active material and the amount of negative electrode active material can therefore be adjusted accordingly. This contributes to achieving a high energy density.

[0053] In some embodiments, the negative electrode active material layer 22B may include, as the negative electrode active material, a silicon-containing material containing at least one of silicon, a silicon oxide, a carbon-silicon compound, or a silicon alloy. The term "silicon-containing material" may be a generic term for a material that includes silicon as a constituent. Note that the silicon-containing material may include only silicon as a constituent. Only one type of silicon-containing material may be used, or two or more types of silicon-containing materials may be used. The silicon-containing material may be capable of forming an alloy with lithium and may be a simple substance of silicon, a silicon alloy, a silicon compound, a mixture of two or more thereof, or a material having one or more phases thereof.Furthermore, the silicon-containing material may be crystalline or amorphous, or may have both a crystalline and an amorphous part. It should be noted that the pure substance described here refers only to a pure substance in the general sense. The pure substance may therefore contain a small amount of impurities. In other words, the purity of the pure substance is not limited to 100%. The silicon alloy may contain, as one or more components, one or more elements in addition to silicon, including, for example, tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium. The silicon compound may contain, as one or more components, one or more of the elements, including but not limited to carbon and oxygen, in addition to silicon.It is noted that the silicon compound may include, as one or more constituent elements other than silicon, one or more of the constituent elements described above with respect to the silicon alloy. Examples of the silicon alloy and the silicon compound may include, without limitation, 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). Note that the range of v can be chosen arbitrarily and can be, for example, 0.2 < v < 1.4. [Separator 23]

[0054] The separator 23 may be disposed between the positive electrode 21 and the negative electrode 22. The separator 23 can allow lithium ions to pass through and prevent a current from short-circuiting due to contact between the positive electrode 21 and the negative electrode 22. The separator 23 may comprise, for example, one or more types of porous films, each comprising, for example, but not limited to, a synthetic resin or a ceramic. In some embodiments, the separator 23 may be a stacked film comprising two or more types of porous films. Examples of the synthetic resin may include polytetrafluoroethylene, polypropylene, and polyethylene. In some embodiments, the separator 23 may have a base comprising a single-layer porous polyolefin film including polyethylene. One reason for this is that this contributes to a favorable high output characteristic compared to a stacked film.In some embodiments, when each of the first separator part 23A and the second separator part 23B included in the separator 23 is a single-layer porous film comprising polyolefin, the single-layer porous film comprising polyolefin may have a thickness of, for example, greater than or equal to 10 μm and less than or equal to 15 μm. When the single-layer porous film comprising polyolefin has a thickness greater than or equal to 10 μm, an internal short circuit can be sufficiently avoided. When the single-layer porous film comprising polyolefin has a thickness less than or equal to 15 μm, a more favorable discharge capacity characteristic can be achieved. In some embodiments, the single-layer porous film comprising polyolefin may have a surface density of, for example, greater than or equal to 6.3 g / m. 2 and less than or equal to 8.3 g / m 2If the single-layer porous film comprising polyolefin has a surface density greater than or equal to 6.3 g / m 2 internal short circuit can be sufficiently avoided. If the single-layer porous film containing polyolefin has a surface density of less than or equal to 8.3 g / m 2 more favorable discharge capacity characteristics can be achieved.

[0055] In some embodiments, the separator 23 may comprise a porous film as the base described above and a polymer compound layer provided on one or each of two opposite surfaces of the base. One reason for this is to improve the adhesion of the separator 23 to the positive electrode 21 and the negative electrode 22, thereby suppressing deformation of the electrode coil body 20. This suppresses a decomposition reaction of the electrolytic solution and also suppresses leakage of the electrolytic solution impregnated into the base. This contributes to preventing a slight increase in resistance even upon repeated charging and discharging and also suppressing swelling of the secondary battery. The polymer compound layer may comprise a polymer compound such as polyvinylidene difluoride.One reason for this is that the polymer compound, such as polyvinylidene difluoride, has superior physical strength and is electrochemically stable. It should be noted that in some embodiments, the polymer compound may be other than polyvinylidene difluoride. To form the polymer compound layer, for example, a solution in which the polymer compound is dissolved in a solvent, such as an organic solvent, may be applied to the base, after which the base may be dried. In some embodiments, the base may be immersed in the solution and then dried. In some embodiments, the polymer compound layer may include one or more types of insulating particles, such as inorganic particles. Examples of the type of inorganic particles may include aluminum oxide and aluminum nitride. [Electrolytic solution]

[0056] The electrolyte solution may include a solvent and an electrolyte salt. In some embodiments, the electrolyte solution may further include one or more other materials. Non-limiting examples of the other materials may include an additive. The solvent may include one or more non-aqueous solvents, including, but not limited to, an organic solvent. An electrolyte solution including a non-aqueous solvent may be a so-called non-aqueous electrolyte solution. The non-aqueous solvent may include, for example, a fluorine compound and a dinitrile compound. The fluorine compound may include, for example, at least one of fluorinated ethylene carbonate, trifluorocarbonate, trifluoroethyl methyl carbonate, a fluorinated carboxylic acid ester, or a fluoroether.In some embodiments, the non-aqueous solvent may further comprise one or more nitrile compounds other than the dinitrile compound. Non-limiting examples of nitrile compounds other than the dinitrile compound may include a mononitrile compound and a trinitrile compound. In some embodiments, the dinitrile compound may comprise succinonitrile (SN). It is noted that the dinitrile compound is not limited to succinonitrile and may be any other dinitrile compound, such as adiponitrile.

[0057] For example, the electrolyte salt may comprise one or more salts, including, but not limited to, a lithium salt. In some embodiments, the electrolyte salt may comprise a salt other than the lithium salt. Non-limiting examples of the non-lithium salt may be a salt of a light metal other than lithium. Examples of the lithium salt may 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 (Li2SiF6), lithium chloride (LiCl), and lithium bromide (LiBr). In some embodiments, the lithium salt may comprise one or more of LiPF6, LiBF4, LiClO4, or LiAsF6. In some embodiments, the lithium salt may be LiPF6.The content of the electrolyte salt is not particularly limited. In some embodiments, the content of the electrolyte salt may be in a range of 0.3 mol / kg to 3 mol / kg, inclusive, with respect to the solvent. In some embodiments, when the electrolyte solution includes LiPF6 as the electrolyte salt, a concentration of LiPF6 in the electrolyte solution may be in a range of 1.25 mol / kg to 1.45 mol / kg, inclusive. One reason for this is that this contributes to preventing cycle deterioration caused by consumption or decomposition of the salt at the time of high-load charging, and thus contributes to improving high-load cyclability. In some embodiments, when the electrolyte solution includes LiBF4 in addition to LiPF6 as the electrolyte salt, a concentration of LiBF4 in the electrolyte solution may be in a range of 0.001 wt% to 0.1 wt%.-%, both inclusive. One reason for this is that this helps more effectively prevent cycle deterioration caused by salt consumption or decomposition during high-load charging, thus contributing to further improving high-load cyclability. [1-2. Operation]

[0058] In the secondary battery 1 according to the present embodiment, for example, during charging, lithium ions can be extracted from the positive electrode 21, and the extracted lithium ions can be introduced into the negative electrode 22 via the electrolyte solution. In the secondary battery 1, for example, during discharging, lithium ions can be extracted from the negative electrode 22, and the extracted lithium ions can be introduced into the positive electrode 21 via the electrolyte solution. [1-3. Manufacturing process]

[0059] A method for manufacturing the secondary battery 1 will be described with reference to Fig. 7A to 7F and the Fig. 1 to 6B. The Fig. 7A to 7F are perspective diagrams showing a manufacturing process of the Fig. Describe the secondary battery 1 shown in Figure 1.

[0060] First, the positive electrode current collector 21A may be prepared, and the positive electrode active material layer 21B may be selectively formed on the surface of the positive electrode current collector 21A. Next, the insulating layer 101 may be formed on the surface of the positive electrode current collector 21A along the first edge 21BT1 of the positive electrode active material layer 21B. After that, a portion of the positive electrode active material layer 21B may be removed by a method such as laser ablation, thereby forming the thin part 61. The positive electrode 21 can thus be obtained by the process described above.Thereafter, the negative electrode current collector 22A may be manufactured, and the negative electrode active material layer 22B may be selectively formed on the surface of the negative electrode current collector 22A, thereby forming the negative electrode 22 having the covered negative electrode region 221 and the exposed negative electrode region 222. In some embodiments, the positive electrode 21 and the negative electrode 22 may be subjected to a drying process. Thereafter, the positive electrode 21 and the negative electrode 22 may be stacked, with the first separator part 23A and the second separator part 23B located on the positive electrode 21 and the negative electrode 22, respectively, to cause the exposed positive electrode region 212 and the first part 222A of the exposed negative electrode region 222 to be on opposite sides of each other in the W direction. The stack body S20 can thus be manufactured.Thereafter, the stacked body S20 can be spirally wound to form the through-hole 26. When winding the stacked body S20, for example, a circular columnar winding core can be used as a jig, and the stacked body S20 can be wound around the circular columnar winding core. Additionally, the fixing tape 46 can be attached to an outermost turn of the spirally wound stacked body S20, after which the winding core can be removed. Thus, the electrode winding body 20 can be formed as shown in FIG. Fig. 7A can be obtained.

[0061] Afterwards, as in Fig. 7B, a portion of the upper end surface 41 and a portion of the lower end surface 42 of the electrode winding body 20 are each locally bent by pressing one end of, for example, a 0.5 millimeter thick flat plate perpendicularly, ie, in the Z-axis direction, against the upper end surface 41 and the lower end surface 42. This allows the formation of grooves 43 that radiate in radial directions (R directions) from the through-hole 26. It is noted that the number and arrangement of the grooves 43 shown in Fig. 7B are merely an example, and an embodiment of the disclosure is not limited thereto. In some embodiments, the number of grooves 43 may be any other number, and the grooves 43 may be arranged in any other manner.

[0062] Afterwards, as in Fig. 7C, substantially equal pressures are applied to the upper end surface 41 and the lower end surface 42 in substantially perpendicular directions from above and below the electrode wound body 20 at substantially the same time. At this time, for example, a rod-shaped jig may be inserted into the through-hole 26 in advance. Through this process, the positive electrode exposed portion 212 and the first part 222A of the negative electrode exposed portion 222 may be bent to convert the upper end surface 41 and the lower end surface 42, respectively, into flat surfaces. In some embodiments, at this time, the portions of the positive electrode edge part 212E of the positive electrode exposed portion 212 at the upper end surface 41, which are adjacent to each other in the radial direction of the wound electrode body 20, may be bent toward the through-hole 26 so as to overlap each other.Similarly, in some embodiments, the portions of the negative electrode edge part 222E of the negative electrode exposed region 222 at the lower end surface 42 that are adjacent to each other in the radial direction of the electrode coil body 20 may be bent toward the through-hole 26 so as to overlap each other. Thereafter, the fan-shaped part 31 of the positive electrode current collector plate 24 may be joined to the upper end surface 41 by a method such as laser welding, and the fan-shaped part 33 of the negative electrode current collector plate 25 may be joined to the lower end surface 42 by a method such as laser welding.

[0063] Thereafter, the insulating tapes 53 and 54 can be applied to predetermined respective locations on the electrode winding body 20. Thereafter, as in Fig. 7D, the band-shaped part 32 of the positive electrode current collector plate 24 may be bent and passed through a hole 12H of the insulating plate 12. Furthermore, the band-shaped part 34 of the negative electrode current collector plate 25 may be bent and passed through a hole 13H of the insulating plate 13.

[0064] Thereafter, the electrode winding body 20, which has been assembled in the manner described above, can be inserted into the outer housing container 11, which is in Fig. 7E, after which the bottom portion 11B of the outer casing container 11 and the negative electrode current collector plate 25 can be welded together. Next, a narrow portion can be formed near the open end portion 11N of the outer casing container 11. Further, the electrolytic solution can be injected into the outer casing container 11, after which the band-shaped portion 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 can be welded together.

[0065] After that, as in Fig. 7F, the outer housing container 11 can be sealed with the gasket 15, the safety valve mechanism 30, and the battery cover 14 using the narrow part. Thereafter, the outer housing container 11, with the disk 55 attached to the battery cover 14, can be covered with the outer housing tube 50, after which the outer housing tube 50 can be heated, for example, by applying hot air. The outer housing tube 50 can thus be contracted and tightly fitted to the outer surface of the outer housing container 11.

[0066] The secondary battery 1 according to the present embodiment can thus be completed. [1-4. Effects and example effects]

[0067] In the secondary battery 1 according to the present embodiment, the thin part 61 and the thick part 71 are provided so as to be adjacent to each other in the W direction in the positive electrode active material layer 21B, as described above. The W direction is the direction orthogonal to the winding direction, that is, the L direction. Thus, the provision of the thin part 61 with the small thickness in a portion of the positive electrode active material layer 21B contributes to suppressing the concentration of stress within the electrode winding body 20 contained in the outer casing container 11. For example, this helps prevent excessive deformation, such as buckling or bending, of the negative electrode current collector 21A when the negative electrode 22 within the electrode winding body 20 swells during charging and discharging. One reason for this is that by providing the thin part 61, the amount of the electrode reactant, such as the ion exchanger, can be reduced.Lithium ions are reduced by the amount of ion supplied to a portion of the negative electrode active material layer 22B opposite the thin part 61, thereby suppressing the expansion and contraction of the portion of the negative electrode active material layer 22B opposite the thin part 61. This also reduces the stress acting on the separator 23 separating the positive electrode 21 and the negative electrode 22, which helps prevent breakage of the separator 23 and thereby prevent a short circuit between the positive electrode 21 and the negative electrode 22, even when the separator 23 has a reduced thickness. In other words, it helps enable a reduction in the thickness of the separator 23. Reducing the thickness of the separator 23 enables a reduction in the distance between the positive electrode 21 and the negative electrode 22, thereby reducing the internal resistance of the electrode coil body 20.This contributes, for example, to improving the rate characteristics during charging and discharging and increasing the capacity of the secondary battery 1. Furthermore, the positive electrode active material layer 21B, which has the thick part 71 at the position adjacent to the thin part 61 in the W direction, contributes to firmly holding the separator 23 disposed between the positive electrode active material layer 21B and the negative electrode active material layer 22B. This helps prevent the easy occurrence of winding displacement of the electrode bobbin 20 upon expansion and contraction of the electrode bobbin 20, and thus helps prevent the separator 23 from being displaced from a predetermined position. This helps prevent a short circuit between the positive electrode 21 and the negative electrode 22.Accordingly, the secondary battery 1 according to the present embodiment contributes to achieving superior reliability.

[0068] In some embodiments, the thin part 61 may be provided along the winding center side edge 21E1 of the positive electrode 21 in the L direction. For example, the thin part 61 may be provided at a position closest to the winding center in the positive electrode active material layer 21B. This contributes to effectively suppressing stress concentration at and near the winding center of the electrode winding body 20 in the region inside the electrode winding body 20, where stress concentration tends to occur significantly more easily.

[0069] In some embodiments, the thick part 71 may be provided between the thin part 61 and the insulating layer 101. This allows the insulating layer 101 to have a sufficient thickness, thus improving the insulating performance of the insulating layer 101. In some embodiments, the thick part 71 may be in contact with the insulating layer 101. This helps prevent the insulating layer 101 from easily peeling off from the positive electrode current collector 21A and the positive electrode active material layer 21B.

[0070] In some embodiments, the positive electrode active material layer 21B may further include the thick portion 72 having the second edge 21BT2 located on the opposite side of the first edge 21BT1 in the W direction. This contributes to more firmly holding the separator 23 disposed between the positive electrode active material layer 21B and the negative electrode active material layer 22B.

[0071] In some embodiments, the positive electrode active material layer 21B may further include the thick part 73 provided on the opposite side of the thin part 61 from the winding center edge side 21E1 in the L direction. This contributes to maintaining a predetermined battery capacity while suppressing the stress concentration at and near the winding center of the electrode bobbin 20.

[0072] In some embodiments, each of the inner coil-side positive electrode active material layer 21B1 and the outer coil-side positive electrode active material layer 21B2 may include the thin portion 61 and the thick portions 71 to 73. This contributes to further effectively suppressing stress concentration at and near the winding center of the electrode coil body 20. In some embodiments, the thin portion 61 may be provided in a region including the center of the positive electrode 21 in the W direction, that is, in the width direction of the positive electrode 21. This contributes to effectively suppressing stress concentration within the electrode coil body 20.

[0073] In some embodiments, the secondary battery 1 may comprise a lithium-ion secondary battery. This contributes to the ability to stably maintain sufficient battery capacity by inserting / storing and removing / removing lithium. This contributes to achieving higher operational reliability. [2. Application examples]

[0074] Non-limiting examples of applications of the secondary battery 1 according to the embodiment of the disclosure example may be as described below. [2-1. Battery pack]

[0075] Fig. 8 is a block diagram illustrating an example of a circuit configuration in which the secondary battery 1 according to the embodiment of the disclosure is applied to a battery pack 300. The battery pack 300 may include an assembled battery 301, a switch 304, an outer casing body 305, a current detection resistor 307, a temperature detection device 308, and a processor 310. The switch 304 may include a charge control switch 302a and a discharge control switch 303a. The outer casing 305 may include the assembled battery 301.

[0076] The battery pack 300 may include a positive electrode terminal 321 and a negative electrode terminal 322. During charging, the positive electrode terminal 321 and the negative electrode terminal 322 may each be connected to a positive electrode terminal and a negative electrode terminal of a charger to perform the charging process. When used with electronic devices, the positive electrode terminal 321 and the negative electrode terminal 322 may each be connected to a positive electrode terminal and a negative electrode terminal of the electronic device to perform a discharge.

[0077] The assembled battery 301 may include secondary batteries 301a connected in series or parallel. The secondary battery 1 described above is applicable to each of the secondary batteries 301a. Fig. 8 shows an example case in which six secondary batteries 301a are coupled in a configuration with two parallel couplings and three series couplings (2P3S); however, the secondary batteries 301a may also be coupled in any other way, for example, in a configuration with n parallel couplings and m series couplings, where n and m are each an integer.

[0078] The switch 304 may include the charge control switch 302a, a diode 302b, the discharge control switch 303a, and a diode 303b, and may be controlled by the processor 310. The diode 302b may have a polarity that is reverse-biased with respect to a charging current flowing in a direction from the positive electrode terminal 321 to the assembled battery 301, and a polarity that is forward-biased with respect to a discharging current flowing in a direction from the negative electrode terminal 322 to the assembled battery 301. The diode 303b may have a polarity that is forward-biased with respect to the charging current and reverse-biased with respect to the discharging current. Fig. 8, the switch 304 may be provided on a positive side; however, in some embodiments, the switch 304 may be provided on a negative side.

[0079] The charge control switch 302a can be controlled by a charge and discharge control processor to turn off the charge control switch 302a when the battery voltage reaches an overcharge detection voltage, thereby preventing the charging current from flowing through a current path of the assembled battery 301. After the charge control switch 302a is turned off, simple discharging can be enabled via the diode 302b. Furthermore, the charge control switch 302a can be controlled by the processor 310 to turn off the charge control switch 302a when a large current flows during charging, thereby blocking the charging current from flowing through the current path of the assembled battery 301.The discharge control switch 303a can be controlled by the processor 310 to turn off the discharge control switch 303a when the battery voltage reaches an over-discharge detection voltage, thereby preventing the discharge current from flowing through the current path of the assembled battery 301. After the discharge control switch 303a is turned off, simple charging via the diode 303b can be enabled. Furthermore, the discharge control switch 303a can be controlled by the processor 310 to turn off the discharge control switch 303a when a large current flows during discharging, thereby blocking the discharge current from flowing through the current path of the assembled battery 301.

[0080] The temperature detection device 308 may be a thermistor, for example. The temperature detection device 308 may be provided near the assembled battery 301. The temperature detection device 308 may measure a temperature of the assembled battery 301 and provide data regarding the measured temperature to the processor 310. A voltage detector 311 may measure a voltage of the assembled battery 301 and a voltage of each of the secondary batteries 301a it includes, perform A / D conversion of the measured voltages, and provide data regarding the converted voltages to the processor 310. An ammeter 313 may measure a current using the current detection resistor 307 and provide data regarding the measured current to the processor 310.A switch control processor 314 may control the charge control switch 302a and the discharge control switch 303a of the switch 304 based on data regarding the voltages supplied from the voltage detector 311 and data regarding the current supplied from the ammeter 313.

[0081] When the voltage of one of the secondary batteries 301a reaches the overcharge detection voltage or below, or the overdischarge detection voltage or below, or when a large current suddenly flows, the switch control processor 314 can send a control signal to the switch 304 to prevent overcharging and overdischarging, as well as overcurrent charging and discharging. For example, if the secondary battery is a lithium-ion secondary battery, the overcharge detection voltage can be set to 4.20 V ± 0.05 V, and the overdischarge detection voltage can be set to 2.4 V ± 0.1 V.

[0082] For example, semiconductor switches such as metal-oxide-semiconductor field-effect transistors (MOSFETs) can be used as charge control switch 302a and discharge control switch 303a. In this case, parasitic diodes of the MOSFETs can serve as diodes 302b and 303b. When P-channel FETs are used as charge control switch 302a and discharge control switch 303a, switch control processor 314 can supply control signals DO and CO to a gate of charge control switch 302a and a gate of discharge control switch 303a, respectively. When the charge control switch 302a and the discharge control switch 303a are of the P-channel type, the charge control switch 302a and the discharge control switch 303a can each be turned on by a gate potential that is lower than a source potential by a predetermined value or more.For example, during normal charging and discharging operations, the control signals CO and DO may be set to a low level to turn on the charging control switch 302a and the discharging control switch 303a.

[0083] For example, in the event of overcharging or overdischarging, the control signals CO and DO may be set to a high level to turn off the charge control switch 302a and the discharge control switch 303a.

[0084] A memory 317 may include random access memory (RAM) and read-only memory (ROM). For example, the memory 317 may include non-volatile memory, such as an erasable programmable read-only memory (EPROM). Values, including but not limited to numerical values ​​calculated by the processor 310 and an internal resistance value of each secondary battery 301a in an initial state measured during the manufacturing phase, may be stored in advance in the memory 317 and overwritten as needed. Furthermore, storing data regarding a full charge capacity of the secondary battery 301a in the memory 317 allows the processor 310 to calculate a remaining capacity, for example.

[0085] A temperature detector 318 can measure a temperature using the temperature detecting device 308, perform charge and discharge control upon abnormal heat generation, and perform correction when calculating the remaining capacity. [2-2. Energy storage system]

[0086] The above-described secondary battery 1 according to the embodiment of the disclosure can be attached to, or used to supply electric power to, for example, any equipment including, but not limited to, electronic equipment, an electric vehicle, an electric aircraft, and a power storage device.

[0087] Non-limiting examples of electronic devices may include laptop PCs, smartphones, tablet PCs, PDAs (Personal Digital Assistants) as mobile information terminals, cellular phones, portable connectors, cordless telephone handsets, portable video recording and playback devices, digital cameras, e-books, electronic dictionaries, music players, radios, headphones, game consoles, navigation systems, memory cards, pacemakers, hearing aids, power tools, electric razors, refrigerators, air conditioners, televisions, stereos, water heaters, microwave ovens, dishwashers, washing machines, dryers, lighting devices, toys, medical devices, robots, road resurfacers, traffic signals, and any other electronic devices to which an embodiment of the disclosure is applicable.

[0088] Non-limiting examples of the electric vehicle may include railway vehicles, golf carts, electric carts, electric cars, including hybrid electric cars, and any other electric vehicle to which an embodiment of the disclosure is applicable. The secondary battery 1 may be used as a motive or auxiliary power source for any of these electric vehicles. Examples of energy storage devices may include an energy storage source for architectural structures, including residential buildings, or for power generation facilities, and any other energy storage device to which an embodiment of the disclosure is applicable. [3. Modification examples][First modification example]

[0089] Next, a positive electrode 21-1 according to a first modification example will be described. The positive electrode 21-1 can be attached to the secondary battery 1 according to the above-described embodiment. Fig. 9 shows a sectional configuration in the area of ​​the positive electrode 21-1 and corresponds Fig. 4C, which shows the positive electrode 21 according to the embodiment described above.

[0090] As in Fig. 9, in the positive electrode 21-1 according to the first modification example, the position of the boundary 21B1K in the L direction and the position of the boundary 21B2K in the L direction may be different from each other. In some embodiments, a length L1 from the winding cement side edge 21E1 to the position of the boundary 21B1K and a length L2 from the winding center side edge 21E1 to the position of the boundary 21B2K may be different from each other. Except for the points described above, the positive electrode 21-1 may have a configuration substantially the same as the configuration of the positive electrode 21 according to the above-described embodiment. The length L1 may correspond to a specific but non-limiting example of a "first length" in an embodiment of the disclosure. The length L2 may correspond to a specific but non-limiting example of a "second length" in an embodiment of the disclosure.

[0091] As described above, in the positive electrode 21-1, the position of the boundary 21B1K in the L direction and the position of the boundary 21B2K in the L direction may be different from each other. For example, a position where there is a height difference in the inner coil-side positive electrode active material layer 21B1 and a position where there is a height difference in the outer coil-side positive electrode active material layer 21B2 may be different from each other in the L direction. This allows a position where the stress concentrates in the inward surface 21A1 of the positive electrode current collector 21A due to the swelling of the negative electrode 22 and a position where the stress concentrates in the outward surface 21A2 of the positive electrode current collector 21A due to the swelling of the negative electrode 22 to not coincide.Accordingly, the stress applied to the positive electrode current collector 21A is dispersed. Thus, the secondary battery 1 having the electrode coil 20 including the positive electrode 21-1 according to the first modification example contributes to further suppressing the stress concentration within the electrode coil 20 due to expansion and contraction than when the secondary battery 1 has the positive electrode 21 according to the above-described embodiment. [Second modification example]

[0092] Next, a positive electrode 21-2, that is, each of the positive electrodes 21-2A to 21-2C, according to a second modification example will be described. The positive electrode 21-2, that is, each of the positive electrodes 21-2A to 21-2C, can be attached to the secondary battery 1 according to the above-described embodiment. Fig. 10A to 10C are sectional diagrams illustrating the positive electrodes 21-2A to 21-2C and corresponding to the Fig. 4C, which illustrates the positive electrode 21 according to the embodiment described above.

[0093] As in the Fig. 10A to 10C, in each of the positive electrodes 21-2A to 21-2C according to the second modification example, the inner coil-side positive electrode active material layer 21B1 may further include a grooved part U1, and the outer coil-side positive electrode active material layer 21B2 may further include a grooved part U2. The grooved part U1 may be positioned between the thick part 73-1 and the thin part 61-1. The grooved part U2 may be positioned between the thick part 73-2 and the thin part 61-2. The grooved parts U1 and U2 may each extend in the W direction. The grooved part U1 may have a thickness even smaller than the thickness T61-1 of the thin part 61-1 in the inner coil-side positive electrode active material layer 21B1.Likewise, the grooved part U2 may have a thickness even smaller than the thickness T61-2 of the thin part 61-2 in the outer coil-side positive electrode active material layer 21B2. Note that the grooved parts U1 and U2 of the positive electrode 21-2A in . Fig. 10A each have a cross-sectional shape that is substantially rectangular. The grooved parts U1 and U2 of the positive electrode 21-2B in Fig. 10B may each have a cross-sectional shape that is substantially V-shaped. The grooved parts U1 and U2 of the positive electrode 21-2C in Fig. 10C may each have a substantially U-shaped cross-sectional shape. However, the cross-sectional shape of each of the grooved parts U1 and U2 is not limited to the shape shown in the respective Fig. 10A to 10C and can be selected as desired.

[0094] In each of the positive electrodes 21-2A to 21-2C, a width of the grooved part U1 and a width of the grooved part U2 in the L direction may be the same, or the width of the grooved part U1 and the width of the grooved part U2 may be different in the L direction. The width of the grooved part U1 may refer to a length in the L direction from a position of a boundary 73U1 between the thick part 73-1 and the grooved part U1 to a position of a boundary 61U1 between the thin part 61-1 and the grooved part U1. The width of the grooved part U2 may refer to a length in the L direction from a position of a boundary 73U2 between the thick part 73-2 and the grooved part U2 to a position of a boundary 61U2 between the thin part 61-2 and the grooved part U2. The width of the grooved part U1 and the width of the grooved part U2 may each be, for example, approximately 150 µm.

[0095] In each of the configuration examples of the positive electrodes 21-2A to 21-2C shown in the Fig. 10A to 10C, respectively, the position of the boundary 73U1 in the L direction and the position of the boundary 73U2 in the L direction may be different from each other, and the position of the boundary 61U1 in the L direction and the position of the boundary 61U2 in the L direction may also be different from each other. However, in some embodiments of the disclosure, the position of the boundary 73U1 in the L direction and the position of the boundary 73U2 in the L direction may coincide with each other. In some embodiments, the position of the boundary 61U1 in the L direction and the position of the boundary 61U2 in the L direction may coincide with each other. In some embodiments, the position of the boundary 73U1 in the L direction and the position of the boundary 73U2 in the L direction may coincide with each other, and in addition, the position of the boundary 61U1 in the L direction and the position of the boundary 61U2 in the L direction may coincide with each other.

[0096] In each of the configuration examples of the positive electrodes 21-2A to 21-2C shown in the Fig. 10A to 10C, the inner coil-side positive electrode active material layer 21B1 may include the grooved portion U1, and the outer coil-side positive electrode active material layer 21B2 may include the grooved portion U2. However, in some embodiments, either the grooved portion U1 or the grooved portion U2 may simply be provided. In some embodiments, each of the positive electrodes 21-2A to 21-2C may simply include either the inner coil-side positive electrode active material layer 21B1 or the outer coil-side positive electrode active material layer 21B2.

[0097] As described above, each of the positive electrodes 21-2A to 21-2C according to the second modification example may include the grooved part U1, the grooved part U2, or both. When the secondary battery 1 includes one of the positive electrodes 21-2A to 21-2C, this contributes to the separator 23 being more firmly held between the corresponding one of the positive electrodes 21-2A to 21-2C and the negative electrode 22. One reason for this is that the separator 23 is partially disposed in the grooved part U1, the grooved part U2, or both, thereby preventing the separator 23, which is located between the corresponding positive electrode 21-2A to 21-2C and the negative electrode 22, from being easily displaced or detached from the predetermined position.Consequently, the secondary battery 1 having one of the positive electrodes 21-2A to 21-2C contributes to effectively preventing a short circuit between the corresponding one of the positive electrodes 21-2A to 21-2C and the negative electrode 22. This contributes to achieving even higher reliability. [Third modification example]

[0098] Next, with reference to the Fig. 11A and Fig. 11B, a description will be given of a positive electrode 21-3 according to a third modification example. The positive electrode 21-3 can be attached to the secondary battery 1 according to the above-described embodiment. Fig. 11A is a view of the positive electrode 21-3 and corresponds Fig. 4A, which illustrates the positive electrode 21 according to the embodiment described above. Fig. 11B is a sectional view of the positive electrode 21-3 and corresponds Fig. 4C, which illustrates the positive electrode 21 according to the embodiment described above. It is noted that Fig. 11B illustrates a region extending in an arrow direction along a Fig. 11A, line XIB-XIB is considered.

[0099] As in the Fig. 11A and Fig. 11B, in some embodiments, the positive electrode active material layer 21B of the positive electrode 21-3 may further include a thin part 62. The thin part 62 may be located on a side of the thick part 73 opposite the thin part 61. The thin part 62 may have a smaller thickness than the thick part 73. The thin part 62 may include a coil outer peripheral side edge 21E2 of the positive electrode 21-3, that is, an edge of the positive electrode 21-3 on the coil outer peripheral side in the L direction. In some embodiments, the thin part 62 may have a length in the L direction corresponding, for example, to about half a turn or less of the electrode bobbin 20 from the coil outer peripheral side edge 21E2. The positive electrode active material layer 21B may further have a thick part 74 adjacent to the thin part 62 in the W direction.For example, the thick part 74 may be positioned between the thin part 62 and the insulating layer 101 in the W direction. In some embodiments, the thick part 74 may include the first edge 21BT1 and be in contact with the insulating layer 101. The positive electrode active material layer 21B may further include a thick part 75. The thick part 75 may include the second edge 21BT2. The thin part 62 may correspond to a specific but non-limiting example of a "second thin part" in an embodiment of the disclosure.

[0100] In the positive electrode 21-3 according to the third modification example, the thin part 62 may be provided on each of the inner surface 21A1 of the positive electrode current collector 21A and the outer surface 21A2 of the positive electrode current collector 21A. In other words, each of the inner coil-side positive electrode active material layers 21B1 and the outer coil-side positive electrode active material layers 21B2 may include the thin part 62. However, in some embodiments, at least one of the inner coil-side positive electrode active material layer 21B1 of the positive electrode 21-3 and the outer coil-side positive electrode active material layer 21B2 of the positive electrode 21-3 may include the thin part 62. It is noted that the thin part 62 in the inner coil-side positive electrode active material layer 21B1 in Fig. 11B is referred to as thin part 62-1 for the sake of simplicity; and the thin part 62 in the outer coil-side positive electrode active material layer 21B2 is referred to as thin part 62-2. Furthermore, in the Fig. 11B, a position of a boundary 21B1K1 between the thin part 61-1 and the thick part 73-1 in the L direction substantially coincides with a position of a boundary 21B2K1 between the thin part 61-2 and the thick part 73-2 in the L direction. In the modification example shown in Fig. 11B, a position of a boundary 21B1K2 between the thin part 62-1 and the thick part 73-1 in the L direction may substantially coincide with a position of a boundary 21B2K2 between the thin part 62-2 and the thick part 73-2 in the L direction.

[0101] In the positive electrode 21-3 according to the third modification example, in addition to the thin part 61, the thin part 62 may be provided on the winding outer peripheral side of the electrode bobbin 20. This contributes to reducing a height difference between a portion where the positive electrode 21 is present and a portion where no positive electrode 21 is present on the winding outer peripheral side of the electrode bobbin 20, compared with the case where the positive electrode 21 is provided without the thin part 62. This contributes to suppressing the concentration of stress at a position of the separator 23 that overlaps the edge 21E2 of the outer peripheral side of the winding. By suppressing the stress concentration, breakage of the separator 23 is avoided even when the separator 23 has a small thickness, and a short circuit between the positive electrode 21 and the negative electrode 22 is prevented.In other words, the thickness of the separator 23 can be reduced. By reducing the thickness of the separator 23, the distance between the positive electrode 21 and the negative electrode 22 can be reduced, thereby reducing the internal resistance of the electrode winding body 20. This contributes, for example, to improving the charging and discharging rate and increasing the capacity of the secondary battery 1. [Examples]

[0102] A description is given of examples of an exemplary embodiment of the disclosure. [Manufacturing process][Example 1-1]

[0103] As described below, the Fig. 1, etc., was manufactured. A lithium-ion secondary battery with nominal dimensions of 21 mm in diameter and 70 mm in length was manufactured here.

[0104] First, a 12 µm-thick aluminum foil was prepared as a 21A positive electrode current collector. Then, a layered lithium oxide as the positive electrode active material was mixed with a positive electrode binder and a conductive additive to obtain a positive electrode mixture. The layered lithium oxide comprised lithium nickel cobalt alumina (NCA) with a Ni content of 85% or more. The positive electrode binder comprised polyvinylidene difluoride. The conductive additive comprised a mixture of carbon black, acetylene black, and Ketjen black. The mixing ratio of the positive electrode active material, the positive electrode binder, and the conductive additive was set to 96.4:2:1.6.Subsequently, the positive electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), after which the organic solvent was stirred to prepare a paste-like slurry of the positive electrode mixture. Then, the slurry of the positive electrode mixture was coated onto the respective predetermined areas of the two opposite surfaces of the positive electrode current collector 21A using a coating device, and the coated slurry of the positive electrode mixture was dried to thereby form the positive electrode active material layers 21B. Furthermore, a coating material comprising polyvinylidene difluoride (PVDF) was coated onto two opposite surfaces in the exposed positive electrode region 212, in respective areas adjacent to the covered positive electrode region 211.The applied coating material was dried to form the insulating layers 101, each having a width of 3 mm and a thickness of 8 μm. Thereafter, the positive electrode active material layers 21B were compression-molded using a roll press. Further, a portion of each of the positive electrode active material layers 21B was removed by laser ablation to thereby form the thin part 61 having the coil center side edge 21E1. At this time, as shown in FIGS. Fig. 12A and Fig. 12B, the thick part 71 (i.e., each of the thick parts 71-1 and 71-2) was formed by leaving each of the positive electrode active material layers 21B partially unremoved, simply at a portion having the inclined surface (i.e., a surface including the first edge 21BT1) covered with the insulating layer 101. Further, the thin part 61 was formed without forming the thick parts 72 (i.e., each of the thick parts 72-1 and 72-2). Fig. 12A is a development view of the positive electrode 21 of Example 1-1 and Fig. 12B is a sectional view of the positive electrode 21 of Example 1-1. Note that, in Example 1-1, the positions, dimensions, and shapes of the thin part 61-1 and the thick part 71-1 of the positive electrode active material layer 21B1 substantially match the positions, dimensions, and shapes of the thin part 61-2 and the thick part 71-2 of the outer coil-side positive electrode active material layer 21B2. Here, the length of the thin part 61 in the L direction, that is, the length from the coil center side edge 21E1 to each of the boundaries 21B1K and 21B2K, was 30 mm. Thus, the positive electrode 21 having the covered positive electrode region 211 and the exposed positive electrode region 212 was obtained.Thereafter, the positive electrode 21 was subjected to shearing to set a width of the covered positive electrode region 211 in the W direction to 60 mm and a width of the exposed positive electrode region 212 in the W direction to 7 mm. Furthermore, a length of the positive electrode 21 in the L direction was set to 1700 mm.

[0105] Further, a copper foil with a thickness of 8 μm was prepared as a 22A negative electrode current collector. Then, the negative electrode active material was mixed with a negative electrode and a conductive additive to obtain a negative electrode mixture. The negative electrode active material comprised a mixture of a carbon material including graphite and SiO. The negative electrode binder comprised polyvinylidene difluoride. 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 SiO in the negative electrode active material was set to 95:5.Subsequently, the negative electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), after which the organic solvent was stirred to prepare a paste-like slurry of the negative electrode mixture. Next, the negative electrode mixture slurry was applied to predetermined areas of two opposite surfaces of the negative electrode current collector 22A using a coating device, and the applied negative electrode mixture slurry was dried to thereby form the negative electrode active material layers 22B. Thereafter, the negative electrode active material layers 22B were compression-molded using a roll press machine. The negative electrode 22, which had the covered negative electrode area 221 and the exposed negative electrode area 222, was thus obtained.Thereafter, the negative electrode 22 was subjected to shearing to adjust the width of the covered negative electrode region 221 in the W direction to 62 mm and the width of the first part 222A of the exposed negative electrode region 222 in the W direction to 4 mm. Furthermore, the length of the negative electrode 22 in the L direction was adjusted to 1760 mm.

[0106] Next, the positive electrode 21 and the negative electrode 22 were stacked one on top of the other, with the first separator part 23A and the second separator part 23B positioned on the positive electrode 21 and the negative electrode 22, respectively, so that the positive electrode exposed region 212 and the first part 222A of the negative electrode exposed region 222 were located on opposite sides in the W direction. The stacked body S20 was thus manufactured. At this time, the stacked body S20 was manufactured such that the positive electrode active material layers 21B did not protrude beyond the negative electrode active material layers 22B in the W direction. Polyethylene films with a width of 65 mm and a thickness of 5 μm were used as the first separator part 23A and the second separator part 23B, respectively.Thereafter, the stacked body S20 was spirally wound to form the through-hole 26, and the fixing tape 46 was attached to the outermost turn of the thus wound stacked body S20.

[0107] Thereafter, the upper end surface 41 and the lower end surface 42 of the wound electrode body 20 were each locally bent by pressing one end of a 0.5 millimeter thick flat plate against each of the upper end surface 41 and the lower end surface 42 in the Z-axis direction, to thereby form the grooves 43 radiating in the radial directions (ie, the R directions) from the through-hole 26.

[0108] Thereafter, substantially equal pressure was applied to the upper end surface 41 and the lower end surface 42 in substantially perpendicular directions from above and below the electrode winding body 20 at substantially the same time. Through this process, the positive electrode exposed portion 212 and the first part 222A of the negative electrode exposed portion 222 were bent to make the upper end surface 41 and the lower end surface 42 flat surfaces, respectively. At this time, portions of the positive electrode edge part 212E of the positive electrode exposed portion 212 at the upper end surface 41 were bent toward the through-hole 26 so as to overlap each other; and portions of the negative electrode edge part 222E of the negative electrode exposed portion 222 at the lower end surface 42 were bent toward the through-hole 26 so as to overlap each other.Thereafter, the fan-shaped part 31 of the positive electrode current collector plate 24 was joined to the upper end surface 41 by laser welding, and the fan-shaped part 33 of the negative electrode current collector plate 25 was joined to the lower end surface 42 by laser welding. The positive electrode current collector plate 24 was used, which has the fan-shaped part 31 provided with the opening 35 with an inner diameter D35 of 4.0 mm.

[0109] Next, the insulating tapes 53 and 54 were applied to the predetermined positions on the electrode winding body 20, respectively. Next, the tape-shaped portion 32 of the positive electrode current collector plate 24 was bent and passed through the hole 12H of the insulating plate 12. Furthermore, the tape-shaped portion 34 of the negative electrode current collector plate 25 was bent and passed through the hole 13H of the insulating plate 13.

[0110] Next, the electrode coil body 20 assembled as described above was inserted into the outer casing container 11, and then the bottom portion 11B of the outer casing container 11 and the negative electrode current collector plate 25 were welded together. Note that the outer casing container 11 had an inner diameter D11 of 20.80 mm ± 0.05 mm.

[0111] Thereafter, the narrow part near the open end portion 11N of the outer casing container 11 was formed. Further, the electrolytic solution was injected into the outer casing container 11, after which the band-shaped portion 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 were welded together.

[0112] As the electrolytic solution, a solution comprising a solvent in which fluoroethylene carbonate (FEC) and succinonitrile (SN) were added to a main solvent, that is, ethylene carbonate (EC) and dimethyl carbonate (DMC), was used; and LiBF4 and LiPF6 were used as electrolytic salts. In the lithium-ion secondary battery of Example 1-1, the content ratio (wt%) of EC, DMC, FEC, SN, LiBF4, and LiPF6 in the electrolytic solution was set to 12.7:56.2:12.0:1.0:1.0:17.1.

[0113] Next, the outer casing container 11 was sealed with the gasket 15, the safety valve mechanism 30, and the battery cover 14 using the narrow part. Next, the outer casing container 11, with the disc 55 mounted on the battery cover 14, was covered with the outer casing tube 50. The outer casing tube 50 was then heated by supplying hot air. The outer casing tube 50 was thereby contracted and tightly fitted to the outer surface of the outer casing container 11.

[0114] The secondary battery of Example 1-1 was thus obtained. [Examples 1-2 to 1-5]

[0115] When forming the thin part 61 by laser ablation, as shown in the Fig. 13A and Fig. 13B, the thick part 71 (ie, each of the thick parts 71-1 and 71-2) was formed by partially covering each of the positive electrode active material layers 21B not only at a portion having the inclined surface (ie, the surface having the first edge 21BT1) covered with the insulating layer 101, but also at a portion not covered with the insulating layer 101. Fig. 13A is a development of the positive electrode 21 of each of Examples 1-2 to 1-5 and Fig. 13B is a sectional view of the positive electrode 21 of each of Examples 1-2 to 1-5. Except for the above-described point, the secondary batteries of Examples 1-2 to 1-5 were each manufactured in a similar manner to Example 1-1. Note that in Example 1-2, a width of the thick part 71 in the W direction was set to 6 mm, which corresponded to 10% of the total width of 60 mm of the positive electrode covered region 211 in the W direction. Similarly, in Example 1-3, the width of the thick part 71 in the W direction was set to 12 mm, which corresponded to 20% of the total width of 60 mm of the positive electrode covered region 211 in the W direction. In Example 1-4, the width of the thick part 71 in the W direction was set to 20 mm, which was 33% of the total width of 60 mm of the covered positive electrode region 211 in the W direction.In Example 1-5, the width of the thick part 71 in the W direction was set to 30 mm, which was 50% of the total width of 60 mm of the covered positive electrode region 211 in the W direction. [Examples 1-6 to 1-9]

[0116] When forming the thin part 61 by laser ablation, as shown in the Fig. 14A and Fig. 14B, the thick part 71 (i.e., each of the thick parts 71-1 and 71-2) and the thick part 72 (i.e., each of the thick parts 72-1 and 72-2) were formed by partially not removing each of the positive electrode active material layers 21B at a portion having the inclined surface (i.e., the surface having the first edge 21BT1) covered with the insulating layer 101 and also at a portion not covered with the insulating layer 101. Fig. 14A is a development of the positive electrode 21 of each of Examples 1-6 to 1-9 and Fig. 14B is a sectional view of the positive electrode 21 of each of Examples 1-6 to 1-9. Except for the above-described point, the secondary batteries of Examples 1-6 to 1-9 were each manufactured in a similar manner to Example 1-1. Note that in Example 1-6, a width of the thick part 72 in the W direction was set to 6 mm, which corresponded to 10% of the total width of 60 mm of the positive electrode covered region 211 in the W direction. Similarly, in Example 1-7, the width of the thick part 72 in the W direction was set to 12 mm, which corresponded to 20% of the total width of 60 mm of the positive electrode covered region 211 in the W direction. In Example 1-8, the width of the thick part 72 in the W direction was set to 20 mm, which was 33% of the total width of 60 mm of the covered positive electrode region 211 in the W direction.In Example 1-9, the width of the thick part 72 in the W direction was set to 30 mm, which was 50% of the total width of 60 mm of the covered positive electrode region 211 in the W direction. [Examples 1-10 to 1-15]

[0117] When forming the thin part 61 by laser ablation, as shown in the Fig. 4A and Fig. 4B, the thick part 71 (i.e., each of the thick parts 71-1 and 71-2) and the thick part 72 (i.e., each of the thick parts 72-1 and 72-2) were formed by partially leaving each of the positive electrode active material layers 21B unremoved at a portion having the inclined surface (i.e., the surface having the first edge 21BT1) covered with the insulating layer 101, and also at a portion not covered with the insulating layer 101. Except for the point described above, the secondary batteries of Examples 1-6 to 1-9 were each manufactured in a similar manner to Example 1-1. It is noted that in Example 1-6, the width of each of the thick parts 71 and 72 in the W direction was set to 3 mm, which was 5% of the total width of 60 mm of the positive electrode covered region 211 in the W direction.Similarly, in Example 1-11, the widths of the thick parts 71 and 72 in the W direction were set to 6 mm, which corresponded to 10% of the total width of 60 mm of the covered positive electrode region 211 in the W direction. In Example 1-12, the widths of the thick parts 71 and 72 in the W direction were set to 9 mm, which corresponded to 15% of the total width of 60 mm of the covered positive electrode region 211 in the W direction. In Example 1-13, the widths of the thick parts 71 and 72 in the W direction were set to 15 mm, which corresponded to 25% of the total width of 60 mm of the covered positive electrode region 211 in the W direction. In Example 1-14, the widths of the thick parts 71 and 72 in the W direction were set to 20 mm, which was 33% of the total width of 60 mm of the covered positive electrode region 211 in the W direction.In Example 1-15, the widths of the thick parts 71 and 72 in the W direction were set to 24 mm, which was 40% of the total width of 60 mm of the covered positive electrode region 211 in the W direction. [Example 2-1]

[0118] The secondary battery of Example 2-1 was prepared in a similar manner to Example 1-1, except that the Fig. 9 was used instead of the positive electrode 21. When a portion of the positive electrode active material layer 21B was removed by laser ablation to thereby form the thin part 61 having the coil center side edge 21E1, the position of the boundary 21B1K in the positive electrode active material layer 21B1 in the L direction and the position of the boundary 21B2K in the inner coil side positive electrode active material layer 21B1 in the L direction were set to be different from each other. Furthermore, in the formation of the thin part 61, as shown in FIGS. Fig. 12A and Fig. 12B, the thick part 71 (ie, each of the thick parts 71-1 and 71-2) was formed by simply leaving a portion of each of the positive electrode active material layers 21B unremoved at a portion having the inclined surface (ie, the surface having the first edge 21BT1) covered with the insulating layer 101, but no thick part 72 (ie, none of the thick parts 72-1 and 72-2) was formed. [Example 2-2]

[0119] When forming the thin part 61 by laser ablation, as shown in the Fig. 13A and Fig. As shown in Fig. 13B, the thick part 71 (i.e., each of the thick parts 71-1 and 71-2) was formed by partially leaving each of the positive electrode active material layers 21B unremoved not only at a portion including the inclined surface (i.e., the surface including the first edge 21BT1) covered with the insulating layer 101, but also at a portion not covered with the insulating layer 101. Except for the point described above, the secondary battery of Example 2-2 was manufactured in a similar manner to Example 2-1. Note that in Example 2-2, the width of the thick part 71 in the W direction was set to 6 mm, which was 10% of the total width of 60 mm of the covered positive electrode region 211 in the W direction. [Example 2-3]

[0120] When forming the thin part 61 by laser ablation, as shown in the Fig. 14A and Fig. As shown in Fig. 14B, the thick part 71 (i.e., each of the thick parts 71-1 and 71-2) and the thick part 72 (i.e., each of the thick parts 72-1 and 72-2) were formed by leaving each of the positive electrode active material layers 21B partially unremoved at a portion having the inclined surface (i.e., the surface having the first edge 21BT1) covered with the insulating layer 101, and also at a portion not covered with the insulating layer 101. Except for the point described above, the secondary battery of Example 2-3 was manufactured in a similar manner to Example 2-1. Note that in Example 2-3, the width of the thick part 72 in the W direction was set to 6 mm, which is 10% of the total width of 60 mm of the covered positive electrode region 211 in the W direction. [Example 2-4]

[0121] When forming the thin part 61 by laser ablation, as shown in the Fig. 4A and Fig. As shown in Fig. 4B, the thick part 71 (i.e., each of the thick parts 71-1 and 71-2) and the thick part 72 (i.e., each of the thick parts 72-1 and 72-2) were formed by permanently bleaching each of the positive electrode active material layers 21B at a portion having the inclined surface (i.e., the surface having the first edge 1BT1) covered with the insulating layer 101, and also at a portion not covered with the insulating layer 101. Except for the point described above, the secondary battery of Example 2-4 was manufactured in a similar manner to Example 2-1. Note that in Example 2-4, the width of each of the thick parts 71 and 72 in the W direction was set to 6 mm, which was 10% of the total width of 60 mm of the covered positive electrode region 211 in the W direction. [Example 3-1]

[0122] The secondary battery of Example 3-1 was prepared in a similar manner to Example 1-1, except that a Fig. 15 was used instead of the positive electrode 21. For example, when forming the thin part 61 having the coil center side edge 21E1, by removing a portion of each of the positive electrode active material layers 21B by laser ablation, each of the grooved parts U1 and U2 was formed between the thin part 61 and the thick part 73: the grooved part U1 was formed between the thin part 61-1 and the thick part 73-1, and the grooved part U2 was formed between the thin part 61-2 and the thick part 73-2. At this time, the position of the groove U1 in the L direction and the position of the groove U2 in the L direction coincided. [Example 3-2]

[0123] When forming the thin part 61 by laser ablation, the thick part 71 (i.e., each of the thick parts 71-1 and 71-2) was formed by partially leaving each of the positive electrode active material layers 21B unremoved, not only at a portion having the inclined surface (i.e., the surface having the first edge 21BT1) and covered with the insulating layer 101, but also at a portion not covered with the insulating layer 101. Except for the point described above, the secondary battery of Example 3-2 was manufactured in a similar manner to Example 3-1. Note that in Example 3-2, the width of the thick part 71 in the W direction was set to 6 mm, which was 10% of the total width of 60 mm of the covered positive electrode region 211 in the W direction. [Example 3-3]

[0124] When forming the thin part 61 by laser ablation, the thick part 71 (i.e., each of the thick parts 71-1 and 71-2) and the thick part 72 (i.e., each of the thick parts 72-1 and 72-2) were formed by partially not removing each of the positive electrode active material layers 21B at a portion including the inclined surface (i.e., the surface including the first edge 21BT1) covered with the insulating layer 101, and also at a portion not covered with the insulating layer 101. Except for the above-described point, the secondary battery of Example 3-3 was manufactured in a similar manner to Example 3-1. Note that in Example 3-3, the width of the thick part 72 in the W direction was set to 6 mm, which was 10% of the total width of 60 mm of the covered positive electrode region 211 in the W direction. [Example 3-4]

[0125] When forming the thin part 61 by laser ablation, the thick part 71 (i.e., each of the thick parts 71-1 and 71-2) and the thick part 72 (i.e., each of the thick parts 72-1 and 72-2) were formed by partially not removing each of the positive electrode active material layers 21B, at a portion having the inclined surface (i.e., the surface having the first edge 21BT1) covered with the insulating layer 101, and also at a portion not covered with the insulating layer 101. Except for the point described above, the secondary battery of Example 3-4 was manufactured in a similar manner to Example 3-1. It is noted that in Example 3-4, the width of each of the thick parts 71 and 72 in the W direction was set to 6 mm, which was 10% of the total width of 60 mm of the positive electrode covered region 211 in the W direction. [Example 4-1]

[0126] The secondary battery of Example 4-1 was prepared in a similar manner to Example 1-1, except that the Fig. 10C was used instead of the positive electrode 21. When forming the thin part 61 having the coil center side edge 21E1 by removing a portion of the positive electrode active material layer 21B by laser ablation, each of the grooved parts U1 and U2 was formed between the thin part 61 and the thick part 73: the grooved part U1 was formed between the thin part 61-1 and the thick part 73-1, and the grooved part U2 was formed between the thin part 61-2 and the thick part 73-2. At this time, the position of the grooved part U1 in the L direction and the position of the grooved part U2 in the L direction were set to be different from each other. [Example 4-2]

[0127] When forming the thin part 61 by laser ablation, the thick part 71 (i.e., each of the thick parts 71-1 and 71-2) was formed by partially not removing each of the positive electrode active material layers 21B, not only at a portion having the inclined surface (i.e., the surface having the first edge 21BT1) covered with the insulating layer 101, but also at a portion not covered with the insulating layer 101. Except for the point described above, the secondary battery of Example 4-2 was manufactured in a similar manner to Example 4-1. Note that in Example 4-2, the width of the thick part 71 in the W direction was set to 6 mm, which is 10% of the total width of 60 mm of the covered positive electrode region 211 in the W direction. [Example 4-3]

[0128] When forming the thin part 61 by laser ablation, the thick part 71 (i.e., each of the thick parts 71-1 and 71-2) and the thick part 72 (i.e., each of the thick parts 72-1 and 72-2) were formed by partially not removing each of the positive electrode active material layers 21B, at a portion having the inclined surface (i.e., the surface having the first edge 21BT1) covered with the insulating layer 101, and also at a portion not covered with the insulating layer 101. Except for the point described above, the secondary battery of Example 4-3 was manufactured in a similar manner to Example 4-1. It is noted that in Example 4-3, the width of the thick part 72 in the W direction was set to 6 mm, which corresponds to 10% of the total width of 60 mm of the positive electrode covered region 211 in the W direction. [Example 4-4]

[0129] When forming the thin part 61 by laser ablation, the thick part 71 (i.e., each of the thick parts 71-1 and 71-2) and the thick part 72 (i.e., each of the thick parts 72-1 and 72-2) were formed by partially not removing each of the positive electrode active material layers 21B, at a portion having the inclined surface (i.e., the surface having the first edge 21BT1) covered with the insulating layer 101, and also at a portion not covered with the insulating layer 101. Except for the point described above, the secondary battery of Example 4-4 was manufactured in a similar manner to Example 4-1. It is noted that in Example 4-4, the width of each of the thick parts 71 and 72 in the W direction was set to 6 mm, which was 10% of the total width of 60 mm of the positive electrode covered region 211 in the W direction. [Example 5-1]

[0130] Of the inner coil-side positive electrode active material layer 21B1 and the outer coil-side positive electrode active material layer 21B2 each provided on the positive electrode current collector 21A, the thin part 61 was simply provided in the inner coil-side positive electrode active material layer 21B1 provided on the inner surface 21A1 of the positive electrode current collector 21A. For example, in Example 5-1, the thin part 61 was not formed in the outer coil-side positive electrode active material layer 21B2 provided on the outer surface 21A2 of the positive electrode current collector 21A, and the outer coil-side positive electrode active material layer 21B2 had a uniform thickness throughout. Except for the point described above, the secondary battery of Example 5-1 was manufactured in a similar manner to Example 1-1. [Example 5-2]

[0131] Of the inner coil-side positive electrode active material layer 21B1 and the outer coil-side positive electrode active material layer 21B2 each provided on the positive electrode current collector 21A, the thin part 61 was simply provided in the inner coil-side positive electrode active material layer 21B1 provided on the inner surface 21A1 of the positive electrode current collector 21A. In Example 5-2, the thin part 61 was not formed in the outer coil-side positive electrode active material layer 21B2 provided on the outer surface 21A2 of the positive electrode current collector 21A, and the outer coil-side positive electrode active material layer 21B2 had a uniform thickness throughout. Except for the point described above, the secondary battery of Example 5-2 was manufactured in a manner similar to Example 1-11. [Example 5-3]

[0132] Of the inner coil-side positive electrode active material layer 21B1 and the outer coil-side positive electrode active material layer 21B2, each provided on the positive electrode current collector 21A, the thin part 61 and the grooved part U1 were simply formed in the inner coil-side positive electrode active material layer 21B1 provided on the inner surface of the positive electrode current collector 21A. In Example 5-2, neither the thin part 61 nor the grooved part U2 were formed in the outer coil-side positive electrode active material layer 21B2 provided on the outer surface 21A2 of the positive electrode current collector 21A, and the outer coil-side positive electrode active material layer 21B2 had a uniform thickness throughout. Except for the point described above, the secondary battery of Example 5-3 was manufactured in a similar manner to Example 3-4. [Example 6-1]

[0133] The secondary battery of Example 6-1 was prepared in a similar manner to Example 1-11, except that the Fig. 11A and Fig. 11B was used instead of the positive electrode 21. The thin part 61 and the thin part 62 were formed, respectively, on the inner coil-side positive electrode active material layer 21B1 and on the outer coil-side positive electrode active material layer 21B2, which were each provided on the positive electrode current collector 21A by selective laser ablation. Note that in Example 6-1, the width of each of the thick parts 71, 72, 74, and 75 in the W direction was set to 6 mm, which was 10% of the total width of 60 mm of the positive electrode covered area 211 in the W direction. [Comparison example 1]

[0134] The thin part 61 was not formed in either the inner coil-side positive electrode active material layer 21B1 or the outer coil-side positive electrode active material layer 21B2 provided on the positive electrode current collector 21A, and the inner coil-side positive electrode active material layer 21B1 and the outer coil-side positive electrode active material layer 21B2 each had a uniform thickness throughout. Except for the above-described point, the secondary battery of Comparative Example 1 was manufactured in a manner similar to Example 1-1. [Comparison example 2]

[0135] The thin portion 61 was formed on each of the inner coil-side positive electrode active material layer 21B1 and the outer coil-side positive electrode active material layer 21B2, each provided on the positive electrode current collector 21A. The thin portion 61 extended over the entire covered positive electrode region 211 in the W direction. In other words, none of the thick portions 71 and 72 were provided. Except for the above-described point, the secondary battery of Comparative Example 2 was manufactured in a manner similar to Example 1-1. [Evaluation of battery properties]

[0136] Each of the secondary batteries of Examples 1-1 to 1-15, 2-1 to 2-4, 3-1 to 3-4, 4-1 to 4-4, and 5-1 to 5-3, as well as Comparative Examples 1 and 2 obtained as described above, was tested for the presence or absence of a defective winding, the short-circuit rate after the first charge-discharge cycle, the degree of deformation of the positive electrode after the charge-discharge cycle, and the short-circuit rate after the charge-discharge cycle. The results are shown in Tables 1 to 4. [Table 1] Breite des dicken Teils der Positivelektrode (erster dicker Teil:zweiter dicker Teil: Gesamtbreite ) fehlerhafte Wicklung [ppm] Nach erstem Lade- und Entladezyklus Nach Lade- und Entladezyklus Kurzschlussrate [ppm] Ausmaß Verformung der PositivElektrode (Mittelteil / Wicklungsmitte-Seiten -rand) [µm] Kurzschluss -rate [%] Beispiel 1-1 Only in places covered with insulation layer 0 0 47 / 24 0 Example 1-2 10%:0%:100% 0 0 45 / 24 0 Examples 1-3 20%:0%:100% 0 0 45 / 25 0 Examples 1-4 33%:0%:100% 0 0 48 / 48 0 Examples 1-5 50%:0%:100% 0 0 65 / 75 0 Examples 1-6 0%:10%:100% 0 0 45 / 24 0 Examples 1-7 0%:20%:100% 0 0 45 / 24 0 Examples 1-8 0%:33%:100% 0 0 48 / 48 0 Examples 1-9 0%:50%:100% 0 0 65 / 76 0 Example 1-10 5%:5%:100% 0 0 42 / 24 0 Example 1-11 10%:10%:100% 0 0 43 / 24 0 Example 1-12 15%:15%:100% 0 0 43 / 25 0 Example 1-13 25%:25%:100% 0 0 45 / 25 0 Example 1-14 33%:33%:100% 0 0 49 / 50 0 Example 1-15 40%:40%:100% 0 0 68 / 80 0 Comparison example 1 No thin part 0 0 - / 300 4 Comparison example 2 0%:0%:100% 0 300 95 / 98 2 [Table 2] Example Width of the thick part of the positive electrode (first thick part:second thick part:total width) Difference in border position faulty winding [ppm] After the first charge and discharge cycle After charging and discharging cycle Short circuit occurrence rate [ppm] Extent of deformation of the positive electrode (middle part / winding center-side edge) [µm] Short circuit rate [%] Example 1-1 Only in position covered with insulation layer No difference 0 0 47 / 24 0 Example 1-2 10%:0%:100% No difference 0 0 45 / 24 0 Examples 1-6 0%: 10%: 100% No difference 0 0 45 / 24 0 Example 1-11 10%:10%:100% No difference 0 0 43 / 24 0 Example 2-1 Only position covered with insulation layer Difference 0 0 23 / 12 0 Example 2-2 10%:0%:100% Difference 0 0 22 / 11 0 Example 2-3 0%:10%:100% Difference 0 0 21 / 11 0 Example 2-4 10%:10%:100% Difference 0 0 20 / 11 0 [Table 3] Width of the thick part of the positive electrode (first thick part: second thick part: total width) Difference in border position grooved part faulty winding [ppm] After the first charge and discharge cycle After charging and discharging cycle Short circuit rate [ppm] Extent of deformation of the positive electrode (middle part / winding center-side edge) [µm] Short circuit rate [%] Example 1-1 Only area covered with insulation layer No difference Not foreseen 0 0 47 / 24 0 Example 1-2 10%:0%:100% No difference Not provided 0 0 45 / 24 0 Examples 1-6 0%:10%:100% No difference Not provided 0 0 45 / 24 0 Example 1-11 10%:10%:100% No difference Not provided 0 0 43 / 24 0 Example 3-1 Only area covered with insulation layer No difference Planned 0 0 24 / 12 0 Example 3-2 10%:0%:100% No difference Planned 0 0 22 / 11 0 Example 3-3 0%:10%:100% No difference Planned 0 0 22 / 11 0 Example 3-4 10%:10%:100% No difference Planned 0 0 18 / 10 0 Example 4-1 Only area covered with insulation layer Difference Planned 0 0 10 / 8 0 Example 4-2 10%:0%:100% Difference Provided 1 0 0 7 / 4 0 Example 4-3 0%:10%:100% Difference Provided 1 0 0 7 / 4 0 Example 4-4 10%:10%:100% Difference Planned 0 0 3 / 4 0 [Table 4] Width of the thick part of the positive electrode (first thick part: second thick part: total width) thin part grooved part faulty winding [ppm] After the first charge and discharge cycle After charging and discharging cycle Short circuit rate [ppm] Extent of deformation of the positive electrode (central part / winding centre-side edge) [µm] Short circuit rate [%] Example 1-1 Only covered with insulating layer in place both sides not provided 0 0 47 / 24 0 Example 1-11 10%:10%:100% both sides not provided 0 0 43 / 24 0 Example 3-4 10%:10%:100% both sides presented 0 0 18 / 10 0 Example 5-1 Only and position covered with insulation layer one page not provided 0 0 40 / 23 0 Example 5-2 10%:10%:100% one page not provided 0 0 30 / 18 0 Example 5-3 10%:10%:100% one page intended 0 0 22 / 12 0

[0137] In addition, each of the secondary batteries of Examples 1-11 and 6-1 was tested for the short-circuit rate after storage at high temperatures. The results are shown in Table 5. Note that the secondary battery of Example 6-1 was also tested for the presence or absence of a faulty winding and the short-circuit rate after the charge and discharge cycle. [Table 5] Width of the thick part of the positive electrode (first thick part: second thick part: total width) Thin part grooved part faulty winding [ppm] After charging and discharging cycle After storage at high temperature inner end part outer end part Short circuit rate [ppm] Short circuit rate [%] (number of samples: 20) Example 1-11 10%:10%:100% intended not provided not provided 0 0 10 Example 6-1 10%:10%:100% intended intended not 0 0 0 [Presence or absence of a defective or faulty winding]

[0138] The electrode coil 20 of each of the secondary batteries was examined to determine whether a physical short circuit occurred in a state where the electrolyte solution was not injected into the electrode coil 20. For the evaluation, the electrode coil 20 of each of the secondary batteries was subjected to a high-voltage test (HPT). When conducting the HPT, a reference value for the insulation resistance was set at 0.2 kV. The number of samples was 10,000. [Short circuit rate after the first charge and discharge cycle]

[0139] The presence or absence of a short circuit, caused, for example, by the mixing of electrically conductive powder such as metal, was determined based on the presence or absence of heat generation after the first charge and discharge cycle. The number of samples was 10,000. [Extent of deformation of the positive electrode after the charge and discharge cycle]

[0140] Based on a computed tomography (CT) image, the projection size of the positive electrode in the radial direction of the electrode coil body 20 was measured, which was caused in a central part of the electrode coil body 20, that is, in a region including the boundaries 21B1K and 21B2K between the thin part 61 and the thick part 73 and the surrounding area, and in a region of the electrode coil body 20 including the coil center side edge 21E1 and the surrounding area. The number of samples was 100. For example, the cycle test was performed under the following test conditions. [Cycle test conditions] (1) Ambient temperature at which the test was conducted: 23 °C. (2) Charging conditions: Constant current and constant voltage (CC-CV) charging was performed. Charging was carried out at a constant current of 10 A up to a voltage of 4.2 V, followed by charging at a constant voltage of 4.2 V. A cut-off current was set to 1 A. (3) Rest time after charging: 60 minutes. (4) Discharge conditions: Constant current (CC) discharge was performed with a constant current of 50 A. A cut-off voltage was set to 2 V, or the discharge was stopped when a temperature of 85 °C was reached. (5) Rest period after discharge: A rest period was observed until the surface temperature of the battery fell below 50 °C. (6) Number of cycles: 100 cycles. [Short circuit rate after charge and discharge cycle]

[0141] Each of the secondary batteries was subjected to a cycle test under the test conditions described above. Afterward, each secondary battery was stored for one week in an environment at 25°C. If a voltage drop of 4.1 V or more was observed after storage, it was determined that a short circuit had occurred. [Short circuit rate after storage at high temperatures]

[0142] Each of the secondary batteries was fully charged. Each of the secondary batteries was charged at a constant current of 0.2 C until a voltage of 4.2 V was reached, and then at a constant voltage of 4.2 V. A cutoff current was set to 15 mA. Afterward, each of the secondary batteries was stored in a thermostatic chamber at 60 °C for 60 days. Afterward, the voltage of each secondary battery was measured. If the voltage was found to have dropped below 4 V, a short circuit was determined. The number of samples was 20.

[0143] As shown in Tables 1 to 4, in each of the secondary batteries of Examples 1-1 to 1-15, 2-1 to 2-4, 3-1 to 3-4, 4-1 to 4-4, and 5-1 to 5-3, none of the defective windings, the short circuit after the initial or first charge and discharge cycle, and the short circuit after the charge and discharge cycle occurred. In comparison, in Comparative Example 1, the short circuit after the charge and discharge cycle occurred at a rate of 4%, that is, four out of 100 samples. Furthermore, in Comparative Example 2, the short circuit after the first charge and discharge cycle occurred at a rate of 300 ppm, and the short circuit after the charge and discharge cycle occurred at a rate of 2%, that is, two out of 100 samples.

[0144] As shown in Table 5, the short circuit after high-temperature storage in Example 1-11 occurred at a rate of 10%, i.e., in two out of 20 samples. In contrast, the short circuit did not occur after high-temperature storage in Example 6-1, i.e., in zero out of 20 samples.

[0145] The results described above showed that the secondary battery of the exemplary embodiment of the disclosure example made it possible to achieve further superior reliability. Furthermore, it was found that it was possible to further improve safety by providing both the thin part near the winding center side edge of the electrode bobbin and the thin part near the winding outer peripheral side edge of the electrode bobbin.

[0146] Although the disclosure has been described above with reference to some embodiments and modification examples, a configuration of any embodiment of the disclosure is not limited to the configurations described with reference to the embodiments and modification examples and can therefore be modified in various ways. For example, in the above embodiment, the thin part 61 serving as a "first thin part" may be positioned to contact the coil center side edge 21E1 of the positive electrode 21. However, an embodiment of the disclosure is not limited to the configuration described above. In some embodiments, the first thin part, e.g., the thin part 61, may be provided at a location in the positive electrode 21 that is distant from the coil center side edge 21E1.Likewise, the thin part 62 serving as the "second thin part" does not necessarily have to be brought into contact with the coil outer peripheral side edge 21E2 of the positive electrode 21. In some embodiments, the second thin part, e.g., the thin part 62, may be provided at a location in the positive electrode 21 remote from the coil outer peripheral side edge 21E2.

[0147] For example, in the above exemplary embodiments and modification examples, the case where the electrode reactant is lithium was described; however, the electrode reactant is not particularly limited. In some embodiments, the electrode reactant may be another alkali metal such as sodium or potassium. In some embodiments, the electrode reactant may be an alkaline earth metal such as beryllium, magnesium, or calcium, as described above. In some embodiments, the electrode reactant may be another light metal such as aluminum.

[0148] The effects described herein are merely examples, and the effects of an embodiment of the disclosure are therefore not limited to those described herein. Accordingly, an embodiment of the disclosure may achieve any other effect.

[0149] Furthermore, the disclosure encompasses any possible combination of some or all of the various embodiments and modification examples described and included herein. At least the following configurations can be achieved from the above-described embodiments of the disclosure. (1) Secondary battery (1), comprising: an electrode winding body having a stacked body and a through-hole, the stacked body having a positive electrode, a negative electrode, and a separator and wound along a longitudinal direction of the stacked body, the through-hole being provided through the electrode winding body in a width direction orthogonal to the longitudinal direction; and an outer housing container containing the electrode winding body, wherein the positive electrode a positive electrode active material layer extending in both the longitudinal and width directions, a positive electrode current collector having a covered positive electrode region and an exposed positive electrode region, wherein the covered positive electrode region is covered with the positive electrode active material layer, wherein the exposed positive electrode region is not covered with the positive electrode active material layer and extends in the width direction from the positive electrode active material layer, and an insulating layer extending longitudinally along a first edge of the positive electrode active material layer, the first edge being arranged at a boundary between the covered positive electrode region and the exposed positive electrode region, and the positive electrode active material layer has a first thin part and a first thick part, wherein the first thick part has a thickness greater than the thickness of the first thin part and is adjacent to the first thin part in the width direction. (2) The secondary battery according to (1), in which the first thin part has a winding center side edge of the positive electrode in the longitudinal direction. (3) The secondary battery according to (1) or (2), in which the first thick part is arranged between the first thin part and the insulating layer. (4) The secondary battery according to any one of (1) to (3), in which the first thick part is in contact with the insulating layer. (5) The secondary battery according to any one of (1) to (4), in which the positive electrode active material layer further has a second thick part arranged on a side opposite to the first thick part in the width direction, and the second thick part has a thickness that is greater than the thickness of the first thin part. (6) The secondary battery according to any one of (1) to (5), in which the positive electrode active material layer further comprises a third thick part arranged on a side of the first thin part opposite the winding center side edge in the longitudinal direction, and the third thick part has a thickness that is greater than the thickness of the first thin part. (7) The secondary battery according to any one of (1) to (6), in which the positive electrode current collector has an inwardly facing surface and an outwardly facing surface, wherein the inwardly facing surface faces a winding center side of the electrode winding body, the outwardly facing surface faces an outer side opposite the winding center side of the electrode winding body, and both the first thick part and the first thin part are provided on the inward-facing surface and the outward-facing surface of the positive electrode current collector, respectively. (8) The secondary battery according to any one of (1) to (7), in which the positive electrode current collector has an inwardly facing surface and an outwardly facing surface, wherein the inwardly facing surface faces a winding center side of the electrode winding body, the outwardly facing surface faces an outer side opposite the winding center side of the electrode winding body, the positive electrode active material layer comprises a first positive electrode active material layer and a second positive electrode active material layer, wherein the first positive electrode active material layer is provided on the inward-facing surface of the positive electrode current collector, wherein the second positive electrode active material layer is provided on the outward-facing surface of the positive electrode current collector, both the first positive electrode active material layer and the second positive electrode active material layer have the first thin part, the first thick part and the third thick part, and a first length and a second length are different from each other, wherein the first length is a length from the coil center side edge of the positive electrode in the longitudinal direction to a position of a first boundary between the first thin part of the first positive electrode active material layer and the third thick part of the first positive electrode active material layer, wherein the second length is a length from the coil center side edge of the positive electrode in the longitudinal direction to a position of a second boundary between the first thin part of the second positive electrode active material layer and the third thick part of the second positive electrode active material layer. (9) The secondary battery according to any one of (1) to (8), wherein the positive electrode active material layer further has a grooved part between the third thick part and the first thin part. (10) The secondary battery according to any one of (1) to (9), in which the positive electrode active material layer further has a second thin part on a side of the third thick part opposite to the first thin part, and the second thin part has a smaller thickness than the thickness of the third thick part. (11) The secondary battery according to any one of (1) to (10), further comprising a positive electrode current collector plate and a negative electrode current collector plate which are opposed to each other, wherein the electrode coil body is arranged between the positive electrode current collector plate and the negative electrode current collector plate in the width direction, wherein the electrode winding body has a first end face and a second end face, wherein the first end face faces the positive electrode current collector plate in the width direction and the second end face faces the negative electrode current collector plate in the width direction. (12) The secondary battery according to (11), in which the first end surface has an edge part of the positive electrode exposed region bent toward the through-hole, wherein the electrode bobbin is wound. (13) The secondary battery according to any one of (11) or (12), in which all or a part of the positive electrode exposed region is included in the first end face and is connected to the positive electrode current collector plate. (14) The secondary battery according to any one of (11) to (13), in which the negative electrode a negative electrode active material layer extending in both the longitudinal and width directions, and a negative electrode current collector having a covered negative electrode region and an exposed negative electrode region, wherein the covered negative electrode region is covered with the negative electrode active material layer, wherein the exposed negative electrode region is not covered with a negative electrode active material layer and extends in the width direction from the negative electrode active material layer, and the second end surface has an edge part of the negative electrode exposed region bent toward the through-hole, wherein the wound electrode body is wound. (15) The secondary battery according to (14), in which all or part of the exposed negative electrode region is contained in the second end face and is connected to the negative electrode current collector plate. (16) The secondary battery according to any one of (1) to (15), further comprising a cover member connected to the positive electrode current collector plate, wherein the outer housing container has a bottom part and a wall part, wherein the wall part extends in the width direction along an outer edge of the bottom part, the wall part surrounds the electrode winding body, wherein the wall part has an open end part through which the electrode winding body can be passed, wherein the open end part is located on a side opposite the bottom part, and the cover part closes the open end part of the outer housing container. (17) The secondary battery according to (16), in which the positive electrode current collector plate is positioned between the cover part and the first end surface and the negative electrode current collector plate is positioned between the bottom part of the outer casing container and the second end surface. (18) Battery pack comprising: a secondary battery according to any one of (1) to (17); a processor configured to control the secondary battery; and an outer housing container containing the secondary battery.

[0150] According to a secondary battery of at least one embodiment of the disclosure and a battery pack including the secondary battery of at least one embodiment of the disclosure, a positive electrode active material layer has a first thin portion. This helps suppress stress concentration within an outer casing container that may occur due to swelling of a negative electrode. Furthermore, the positive electrode active material layer has a first thick portion adjacent to the first thin portion. This can effectively prevent displacement of a separator disposed between the positive electrode and the negative electrode. This contributes to preventing a short circuit between the positive electrode and the negative electrode, thereby achieving higher reliability.

[0151] It is noted that the effects of an embodiment of the disclosure are not necessarily limited to the example effects described above and may include any series of effects described herein with respect to the example embodiments of the disclosure and their modification examples.

[0152] Although the disclosure has been described above with reference to the exemplary embodiment and the modification examples, the disclosure is not limited thereto. It should be appreciated that those skilled in the art are able to make variations to the described exemplary embodiment and the modification examples without departing from the scope of the disclosure as defined by the following claims.

[0153] The limitations in the claims are to be interpreted broadly based on the language used in the claims and are not limited to the examples described in this specification or during prosecution of the application, and the examples are to be construed as non-exclusive.

[0154] As used in this specification and the appended claims, the singular forms "a", "an" and "the" are to be construed to cover both the singular and the plural, particularly in the context of the claims, unless otherwise stated herein or clearly contradicted by the context.

[0155] In this specification and the appended claims, the terms "comprise," "include," "have," and their variations are to be construed to cover the inclusion of a specified element, integer, or step, but not the exclusion of any other unspecified element, integer, or step, unless the context requires otherwise.

[0156] The use of the terms “first,” “second,” etc., does not indicate order or importance, but rather serves to distinguish one element from another.

[0157] The terms “substantially,” “approximately,” “about,” and their variants of similar meaning are defined as largely, but not necessarily completely, what would be expected to be known by one of ordinary skill in the art.

[0158] The term “arranged on / provided on / formed on” and its variants with similar meaning, as used here, refer to elements that are in contact with each other directly or indirectly through intervening structures. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] JP 2023-165908

[0001] WO 2021 / 020237

[0004]

Claims

[1] Secondary battery (1), comprising: an electrode winding body (20) comprising a stacked body (S20) and a through-hole (26), wherein the stacked body (S20) comprises a positive electrode (21), a negative electrode (22) and a separator (23) and is wound along a longitudinal direction of the stacked body (S20), wherein the through-hole (26) is provided through the electrode winding body (20) in a width direction orthogonal to the longitudinal direction; and an outer housing container (11) containing the electrode winding body (20), wherein the positive electrode (21) a positive electrode active material layer (21B) extending in both the longitudinal and width directions, a positive electrode current collector (21A) having a covered positive electrode region (211) and an exposed positive electrode region (212), wherein the covered positive electrode region (211) is covered with the positive electrode active material layer (21B), wherein the exposed positive electrode region (212) is not covered with the positive electrode active material layer (21B) and extends in the width direction from the positive electrode active material layer (21B), and an insulating layer (101) extending longitudinally along a first edge (21BT1) of the positive electrode active material layer (21B), the first edge (21BT1) being arranged at a boundary (K) between the covered positive electrode region (211) and the exposed positive electrode region (212), and the positive electrode active material layer (21B) has a first thin part (61) and a first thick part (71), wherein the first thick part (71) has a thickness greater than the thickness of the first thin part (61) and is adjacent to the first thin part (61) in the width direction. [2] The secondary battery (1) according to claim 1, wherein the first thin part (61) has a winding center side edge (21E1) of the positive electrode (21) in the longitudinal direction. [3] The secondary battery (1) according to claim 1 or 2, wherein the first thick part (71) is arranged between the first thin part (61) and the insulating layer (101). [4] A secondary battery (1) according to any one of claims 1 to 3, wherein the first thick part (71) is in contact with the insulating layer (101). [5] Secondary battery (1) according to one of claims 1 to 4, wherein the positive electrode active material layer (21B) further comprises a second thick part (72) arranged on a side opposite to the first thick part (71) in the width direction, and the second thick part (72) has a thickness which is greater than the thickness of the first thin part (61). [6] Secondary battery (1) according to one of claims 1 to 5, wherein the positive electrode active material layer (21B) further comprises a third thick part (73) arranged on a side of the first thin part (61) opposite the coil center side edge (21E1) in the longitudinal direction, and the third thick part (73) has a thickness which is greater than the thickness of the first thin part (61). [7] Secondary battery (1) according to one of claims 1 to 6, wherein the positive electrode current collector (21A) has an inwardly directed surface (21A1) and an outwardly directed surface (21A2), wherein the inwardly directed surface (21A1) faces a winding center side of the electrode winding body (20), the outwardly directed surface (21A2) faces an outer side opposite the winding center side of the electrode winding body (20), and both the first thick part (71) and the first thin part (61) are provided on the inward-facing surface (21A1) and the outward-facing surface (21A2) of the positive electrode current collector (21A), respectively. [8] Secondary battery (1) according to one of claims 1 to 7, wherein the positive electrode current collector (21A) has an inwardly directed surface (21A1) and an outwardly directed surface (21A2), wherein the inwardly directed surface (21A1) faces a winding center side of the electrode winding body (20), the outwardly directed surface (21A2) faces an outer side opposite the winding center side of the electrode winding body (20), the positive electrode active material layer (21B) comprises a first positive electrode active material layer (21B1) and a second positive electrode active material layer (21B2), wherein the first positive electrode active material layer (21B1) is provided on the inward-facing surface (21A1) of the positive electrode current collector (21A), wherein the second positive electrode active material layer (21B2) is provided on the outward-facing surface (21A2) of the positive electrode current collector (21A), both the first positive electrode active material layer (21B1) and the second positive electrode active material layer (21B2) have the first thin part (61), the first thick part (71) and the third thick part (73), and a first length (L1) and a second length (L2) are different from each other, wherein the first length (L1) is a length from the winding center side edge of the positive electrode (21) in the longitudinal direction to a position of a first boundary (21B1K) between the first thin part (61) of the first positive electrode active material layer (21B1) and the third thick part (73) of the first positive electrode active material layer (21B1), wherein the second length (L2) is a length from the winding center side edge of the positive electrode (21) in the longitudinal direction to a position of a second boundary (21B2K) between the first thin part (61) of the second positive electrode active material layer (21B2) and the third thick part (73) of the second positive electrode active material layer (21B2). [9] The secondary battery (1) according to any one of claims 1 to 8, wherein the positive electrode active material layer (21B) further has a grooved part (U1) between the third thick part (73) and the first thin part (61). [10] Secondary battery (1) according to one of claims 1 to 9, wherein the positive electrode active material layer (21B) further comprises a second thin part (62) on a side of the third thick part (73) opposite to the first thin part (61), and the second thin part (62) has a smaller thickness than the thickness of the third thick part (73). [11] The secondary battery (1) according to any one of claims 1 to 10, further comprising a positive electrode current collector plate (24) and a negative electrode current collector plate (25) facing each other, wherein the electrode winding body (20) is disposed between the positive electrode current collector plate (24) and the negative electrode current collector plate (25) in the width direction, the electrode winding body (20) having a first end surface (41) and a second end surface (42), the first end surface (41) facing the positive electrode current collector plate (24) in the width direction and the second end surface (42) facing the negative electrode current collector plate (25) in the width direction. [12] The secondary battery (1) according to claim 11, wherein the first end surface (41) has an edge part (212E) of the positive electrode exposed region (212) bent toward the through hole (26) with the electrode winding body (20) wound. [13] The secondary battery (1) according to claim 11 or 12, wherein all or part of the positive electrode exposed portion (212) is included in the first end face (41) and is connected to the positive electrode current collector plate (24). [14] Secondary battery (1) according to one of claims 11 to 13, wherein the negative electrode (22) a negative electrode active material layer (22B) extending in both the longitudinal and width directions, and a negative electrode current collector (22A) having a covered negative electrode region (221) and an exposed negative electrode region (222), wherein the covered negative electrode region (221) is covered with the negative electrode active material layer (21B), wherein the exposed negative electrode region (222) is not covered with a negative electrode active material layer and extends in the width direction from the negative electrode active material layer (21B), and the second end surface (42) has an edge part (222E) of the negative electrode exposed region which is bent toward the through-hole (26), wherein the wound electrode body (20) is wound. [15] The secondary battery (1) according to claim 14, wherein all or part of the negative electrode exposed portion (222) is included in the second end face (42) and is connected to the negative electrode current collector plate (25). [16] A secondary battery (1) according to any one of claims 1 to 15, further comprising a cover member (14) connected to the positive electrode current collector plate (24), wherein the outer housing container (11) has a bottom part (11B) and a wall part (11W), wherein the wall part (11W) is located in the width direction along an outer edge of the bottom part (11B), the wall part (11W) surrounds the electrode winding body (20), wherein the wall part (11W) has an open end part (11N) through which the electrode winding body (20) can be passed, wherein the open end part (11N) is located on a side opposite the bottom part (11B), and the cover part (14) closes the open end part (11N) of the outer housing container (11). [17] Secondary battery (1) according to claim 16, wherein the positive electrode current collector plate (24) is positioned between the cover part (14) and the first end surface (41) and the negative electrode current collector plate (25) is positioned between the bottom part (11B) of the outer housing container (11) and the second end surface (42). [18] Battery pack comprising: a secondary battery (1); a processor (310) configured to control the secondary battery (1); and an outer housing container (305) containing the secondary battery (1), wherein the secondary battery (1) an electrode winding body (20) with a stack body (S20) and a through hole (26), wherein the stack body (S20) has a positive electrode (21), a negative electrode (22) and a separator (23) and is wound along a longitudinal direction of the stack body (S20), wherein the through hole (26) is provided through the electrode winding body (20) in a width direction orthogonal to the longitudinal direction, and an outer housing container (11) having the electrode winding body (20), wherein the positive electrode (21) a positive electrode active material layer (21B) extending in both the longitudinal direction and the width direction, a positive electrode current collector (21A) having a covered positive electrode region (211) and an exposed positive electrode region (212), wherein the covered positive electrode region (211) is covered with the positive electrode active material layer (21B), the exposed positive electrode region (212) is not covered with a positive electrode active material layer and extends in the width direction from the positive electrode active material layer (21B), and an insulating layer (101) extending longitudinally along a first edge (21BT1) of the positive electrode active material layer (21B), the first edge (21BT1) being arranged at a boundary (K) between the covered positive electrode region (211) and the exposed positive electrode region (212), wherein the positive electrode active material layer (21B) has a first thin part (61) and a first thick part (71), wherein the first thick part (71) has a thickness greater than a thickness of the first thin part (61) and is adjacent to the first thin part (61) in the width direction.

Images