Secondary battery, battery pack, electronic device, power tool, electric aircraft, and electric vehicle

Abstract

Provided is a secondary battery having higher reliability. This secondary battery comprises an electrode winding body, a first electrode current collector plate, a second electrode current collector plate, an electrolyte, and a battery container. The first electrode current collector plate faces a first end face of the electrode winding body, and the second electrode current collector plate faces a second end face of the electrode winding body. In the electrode winding body, an outermost peripheral portion of a second electrode is positioned on the outside of an outermost peripheral portion of a first electrode. A side wall of the battery container includes a thick portion and a thick portion that protrudes toward the inside of the battery container along the radial direction. The thick portion is at a position, of a first electrode covered section, that overlaps, in the radial direction, an end on the first end face side in a first direction.

Description

Technical Field

[0001] The present disclosure relates to secondary batteries, as well as battery packs, electronic devices, power tools, electric aircraft, and electric vehicles equipped with secondary batteries.

Background Art

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

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

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

[0006] Therefore, a secondary battery with high safety is desired.

[0007] A secondary battery according to an embodiment of the present disclosure includes an electrode winding body, a first electrode current collector plate, a second electrode current collector plate, an electrolyte, and a battery can. The electrode winding body is formed by winding a laminated structure in which a first electrode and a second electrode are laminated via a separator around a central axis extending in a first direction. The first electrode current collector plate is disposed so as to face a first end face in the first direction of the electrode winding body. The second electrode current collector plate is disposed so as to face a second end face opposite to the first end face in the first direction of the electrode winding body. The battery can has a bottom portion facing the second end face via the second electrode current collector plate and a side wall portion standing on the bottom portion so as to surround the electrode winding body, and houses the electrode winding body, the first electrode current collector plate, the second electrode current collector plate, and the electrolyte. The first electrode has a first electrode covering portion in which a first electrode active material layer covers a first electrode current collector, and a first electrode exposed portion in which the first electrode current collector is exposed without being covered by the first electrode active material layer and is joined to the first electrode current collector plate. The second electrode has a second electrode covering portion in which a second electrode active material layer covers a second electrode current collector, and a second electrode exposed portion in which the second electrode current collector is exposed without being covered by the second electrode active material layer and is joined to the second electrode current collector plate. In the electrode winding body, the outermost peripheral portion of the second electrode is located outside the outermost peripheral portion of the first electrode. The side wall portion of the battery can includes a thin portion and a thick portion protruding inward of the battery can along the radial direction of the electrode winding body orthogonal to the first direction. The thick portion is at a position overlapping in the radial direction with an end portion on the first end face side in the first direction of the first electrode covering portion.

[0008] According to the secondary battery of an embodiment of the present disclosure, the thick portion of the battery can and the end portion of the first electrode covering portion on the first end face side are in a positional relationship of overlapping each other in the radial direction. For this reason, by the thick portion, the vicinity of the first end face of the electrode winding body is urged toward the central axis along the radial direction. As a result, it is possible to suppress the spread of the distance between the end portion of the outermost peripheral portion of the first electrode and the end portion of the outermost peripheral portion of the second electrode. Therefore, high safety can be obtained.

[0009] Note that the effects of the present disclosure are not necessarily limited to the effects described here, and may be any of a series of effects related to the present disclosure described later.

Brief Description of the Drawings

[0010]

Figure 1

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Mode for Carrying Out the Invention

[0011] Hereinafter, with reference to the drawings, a detailed description will be given of an embodiment of the present technology. The order of description is as follows. 1. Secondary battery 1-1. Configuration 1-2. Operation 1-3. Manufacturing method 1-4. Function and effect 2. Application examples

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

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

[0014] The charge and discharge principle of the secondary battery is not particularly limited. Hereinafter, a case where the battery capacity is obtained by utilizing the occlusion and release of the electrode reactant will be described. This secondary battery includes an electrolyte together with a positive electrode and a negative electrode. In this secondary battery, in order to prevent the electrode reactant from depositing on the surface of the negative electrode during charging, the charging capacity of the negative electrode is larger than the discharging capacity of the positive electrode. That is, the electrochemical capacity per unit area of the negative electrode is set to be larger than the electrochemical capacity per unit area of the positive electrode.

[0015] The type of the electrode reactant is not particularly limited as described above. Specifically, it is a light metal such as an alkali metal and an alkaline earth metal. The alkali metals include lithium, sodium, potassium, etc., and the alkaline earth metals include beryllium, magnesium, calcium, etc.

[0016] Hereinafter, the case where the electrode reactant is lithium will be taken as an example. A secondary battery that obtains battery capacity by utilizing the insertion and extraction of lithium is a so-called lithium-ion secondary battery. In this lithium-ion secondary battery, lithium is inserted and extracted in an ionic state.

[0017] [1-1. Configuration] (Lithium-ion secondary battery 1) FIG. 1 shows a cross-sectional configuration along the height direction of a lithium-ion secondary battery 1 (hereinafter simply referred to as secondary battery 1) according to the present embodiment. In the secondary battery 1 shown in FIG. 1, an electrode winding body 20 as a battery element is housed inside a cylindrical exterior can 11. FIG. 2 is an enlarged cross-sectional view showing the upper part of the secondary battery 1.

[0018] Specifically, the secondary battery 1 includes, for example, a pair of insulating plates 12 and 13 and an electrode winding body 20 inside the exterior can 11. The electrode winding body 20 is, for example, a structure in which a positive electrode 21 and a negative electrode 22 are laminated and wound via a separator 23. The electrode winding body 20 has an end face 41 at its upper part and an end face 42 at its lower part. The electrode winding body 20 is impregnated with an electrolytic solution that is a liquid electrolyte. Note that the secondary battery 1 may further include one or more of a thermal sensing resistor (PTC) element and a reinforcing member inside the exterior can 11.

[0019] (Exterior can 11) The exterior can 11 is a container that houses the electrode winding body 20, the positive current collector plate 24, the negative current collector plate 25, and the electrolytic solution. The exterior can 11 has, for example, a hollow cylindrical structure with the lower end in the Z-axis direction (the height direction) closed and the upper end open. Specifically, the exterior can 11 has a bottom portion 11B facing the end face 42 via the negative current collector plate 25 (described later), and a side wall portion 11S standing on the bottom portion 11B so as to surround the electrode winding body 20. The bottom portion 11B is, for example, a plate-shaped member with a substantially circular planar shape. The side wall portion 11S is, for example, a substantially cylindrical member having an outer diameter substantially matching the outer diameter of the bottom portion 11B. The upper end portion of the exterior can 11 in the Z-axis direction is the open end portion 11N. In this specification, in the Z-axis direction, the open end portion 11N and its vicinity are sometimes referred to as the upper part of the secondary battery 1, and the portion where the exterior can 11 is closed and its vicinity are sometimes referred to as the lower part of the secondary battery 1. The side wall portion 11S of the exterior can 11 includes a thin-wall portion 11S1 and a thick-wall portion 11S2. The thick-wall portion 11S2 is provided at the upper end portion of the exterior can 11 in the Z-axis direction of the side wall portion 11S.

[0020] As shown in FIG. 2, the thickness T2 in the radial direction (R direction) of the thick-wall portion 11S2 is thicker than the thickness T1 of the thin-wall portion 11S1 (T2>T1). The thickness T2 of the thick-wall portion 11S2 is preferably, for example, 110% or more and 180% or less of the thickness T1 of the thin-wall portion 11S1. The thick-wall portion 11S2 protrudes toward the inside of the exterior can 11 more than the thin-wall portion 11S1 in a cross section along the Z-axis direction. Therefore, the inner diameter IR2 of the thick-wall portion 11S2 is smaller than the inner diameter IR1 of the thin-wall portion 11S1 (IR1>IR2). The inner diameter IR1 of the thin-wall portion 11S1 is preferably, for example, 100.19% or more and 100.87% or less of the inner diameter IR2 of the thick-wall portion 11S2. As shown in FIG. 2, the outer diameter OR1 of the thin-wall portion 11S1 and the outer diameter OR2 of the thick-wall portion 11S2 are preferably substantially the same (OR1≒OR2). That is, the outer peripheral surface of the thin-wall portion 11S1 and the outer peripheral surface of the thick-wall portion 11S2 preferably constitute a common curved surface, for example, a common cylindrical outer peripheral surface.

[0021] The constituent material of the outer can 11 includes, for example, a metallic material such as iron. However, the surface of the outer can 11 may be plated with a metallic material such as nickel. The insulating plates 12 and 13 are arranged to face each other so as to sandwich the electrode winding body 20 therebetween in the Z-axis direction, for example.

[0022] (Insulating plates 12, 13) Each of the insulating plates 12 and 13 is, for example, a dish-shaped plate having a surface perpendicular to the winding axis of the electrode winding body 20, that is, a surface perpendicular to the Z-axis in FIG. 1. Also, the insulating plates 12 and 13 are arranged so as to sandwich the electrode winding body 20.

[0023] (Crimp structure 11R) At the open end 11N of the outer can 11, for example, a structure in which the battery lid 14 and the safety valve mechanism 30 are crimped via the gasket 15, that is, a crimp structure 11R is formed. The outer can 11 is sealed with the electrode winding body 20 and the like stored inside by the battery lid 14. The crimp structure 11R is a so-called crimp structure and has a bent portion 11P as a so-called crimp portion.

[0024] (Battery lid 14) The battery lid 14 is mainly a closing member that closes the open end 11N in a state where the electrode winding body 20 and the like are stored inside the outer can 11. The battery lid 14 includes, for example, the same material as the forming material of the outer can 11. The central region of the battery lid 14 protrudes upward (+Z direction), for example. As a result, the peripheral region, which is the region other than the central region of the battery lid 14, is in contact with the safety valve mechanism 30, for example.

[0025] (Gasket 15) The gasket 15 is mainly a sealing member interposed between the bent portion 11P of the outer can 11 and the battery lid 14. The gasket 15 seals the gap between the bent portion 11P and the battery lid 14. However, for example, asphalt or the like may be applied to the surface of the gasket 15. The gasket 15 contains, for example, any one or two or more of insulating materials. The type of the insulating material is not particularly limited, but is, for example, a polymer material such as polybutylene terephthalate (PBT) and polypropylene (PP). Among them, the insulating material is preferably polybutylene terephthalate. This is because the gap between the bent portion 11P and the battery lid 14 is sufficiently sealed while electrically separating the outer can 11 and the battery lid 14 from each other.

[0026] (Safety valve mechanism 30) The safety valve mechanism 30 is mainly configured to release the internal pressure of the outer can 11 by releasing the sealed state of the outer can 11 as necessary when the internal pressure (internal pressure) of the outer can 11 rises. The cause of the increase in the internal pressure of the outer can 11 is, for example, gas generated due to the decomposition reaction of the electrolyte during charge and discharge. In addition, the internal pressure of the outer can 11 may increase due to external heating.

[0027] (Electrode winding body 20) The electrode winding body 20 is a power generation element that allows the charge and discharge reaction to proceed and is housed inside the outer can 11. The electrode winding body 20 includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte which is a liquid electrolyte.

[0028] FIG. 3 is a developed view of the electrode winding body 20, schematically showing a part of the laminated structure S20 including the positive electrode 21, the negative electrode 22, and the separator 23. In the electrode winding body 20, the positive electrode 21 and the negative electrode 22 are laminated on each other with the separator 23 interposed therebetween. The separator 23 has, for example, two base materials, that is, a first separator member 23A and a second separator member 23B. Therefore, the electrode winding body 20 has a four-layer laminated structure S20 in which the positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are laminated in this order. The positive electrode 21, the first separator member 23A, the negative electrode 22, and the second separator member 23B are all substantially strip-shaped members having the short side direction in the W-axis direction and the long side direction in the L-axis direction. As shown in FIG. 4, the electrode winding body 20 is wound around a central axis CL (see FIG. 1) extending in the Z-axis direction so that the laminated structure S20 forms a spiral shape in a horizontal cross section orthogonal to the Z-axis direction. At this time, the laminated structure S20 is wound in a posture where the W-axis direction substantially coincides with the Z-axis direction. Note that FIG. 4 shows one configuration example along a horizontal cross section orthogonal to the Z-axis direction in the electrode winding body 20. However, in FIG. 4, the illustration of the separator 23 is omitted for ensuring visibility. The electrode winding body 20 has an overall substantially cylindrical appearance. The positive electrode 21 and the negative electrode 22 are wound while maintaining a state of facing each other with the separator 23 interposed therebetween. A through hole 26 as an internal space is formed at the center of the electrode winding body 20. The through hole 26 is a hole for inserting a winding core for assembling the electrode winding body 20 and an electrode bar for welding.

[0029] The positive electrode 21, the negative electrode 22, and the separator 23 are wound such that the separator 23 is disposed at each of the outermost periphery and the innermost periphery of the electrode winding body 20. Also, at the outermost periphery of the electrode winding body 20, the negative electrode 22 is disposed outside the positive electrode 21. That is, as shown in FIG. 4, the outermost peripheral portion 21out of the positive electrode 21 included in the electrode winding body 20 is located inside the outermost peripheral portion 22out of the negative electrode 22 included in the electrode winding body 20. Here, the outermost peripheral portion 21out of the positive electrode is the portion corresponding to one outermost turn of the positive electrode 21 in the electrode winding body 20. The outermost peripheral portion 22out of the negative electrode is the portion corresponding to one outermost turn of the negative electrode 22 in the electrode winding body 20. As shown in FIG. 4, in the electrode winding body 20, there are a facing portion FA1 between the outermost peripheral portion 21out of the positive electrode and the outermost peripheral portion 22out of the negative electrode, and a facing portion FA2 between the negative electrodes 22. The facing portion FA2 is a portion where the outermost peripheral portion 22out of the negative electrode and the inner peripheral portion 22in of the negative electrode located inside the outermost peripheral portion 22out face each other without passing through the positive electrode 21. On the other hand, at the innermost periphery of the electrode winding body 20, it is preferable that the negative electrode 22 is disposed inside the positive electrode 21. That is, it is preferable that the innermost peripheral portion of the negative electrode 22 included in the electrode winding body 20 is located inside the innermost peripheral portion of the positive electrode 21 included in the electrode winding body 20. Here, the innermost peripheral portion of the positive electrode is the portion corresponding to one innermost turn of the positive electrode 21 in the electrode winding body 20. The innermost peripheral portion of the negative electrode is the portion corresponding to one innermost turn of the negative electrode 22 in the electrode winding 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 arbitrarily set.

[0030] FIG. 5A is a developed view of the positive electrode 21, schematically showing the state before winding. FIG. 5B shows the cross-sectional configuration of the positive electrode 21. Note that FIG. 5B represents a cross-section in the arrow viewing direction along the VB-VB line shown in FIG. 5A. The positive electrode 21 includes, for example, a positive electrode current collector 21A and a positive electrode active material layer 21B provided on the positive electrode current collector 21A. The positive electrode active material layer 21B may be provided, for example, only on one side of the positive electrode current collector 21A, or may be provided on both sides of the positive electrode current collector 21A. FIG. 5B shows the case where the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A.

[0031] The positive electrode 21 has a positive electrode covering portion 211 in which the positive electrode active material layer 21B covers the positive electrode current collector 21A, and a positive electrode exposed portion 212 in which the positive electrode current collector 21A is exposed without being covered by the positive electrode active material layer 21B. As shown in FIG. 5A, the positive electrode covering portion 211 and the positive electrode exposed portion 212 each extend from the outer peripheral side edge 21E1 to the inner peripheral side edge 21E2 of the electrode wound body 20 along the L-axis direction, which is the longitudinal direction. Here, the L-axis direction corresponds to the winding direction of the electrode wound body 20. That is, in the positive electrode 21, in the winding direction of the electrode wound body 20, the positive electrode active material layer 21B covers the positive electrode current collector 21A from the outer peripheral side edge 21E1 to the inner peripheral side edge 21E2 of the positive electrode 21. The positive electrode covering portion 211 and the positive electrode exposed portion 212 are adjacent to each other in the W-axis direction, which is the short hand direction. Note that the positive electrode exposed portion 212 is connected to the positive electrode current collecting plate 24 as shown in FIG. 1. An insulating layer 101 may be provided near the boundary between the positive electrode covering portion 211 and the positive electrode exposed portion 212. The insulating layer 101 also extends from the innermost peripheral side end portion to the outermost periphery of the electrode wound body 20, similar to the positive electrode covering portion 211 and the positive electrode exposed portion 212. sideIt is preferably extended to the end. Further, the insulating layer 101 may be adhered to at least one of the first separator member 23A and the second separator member 23B. This is because it can prevent the displacement between the positive electrode 21 and the separator 23. Further, the insulating layer 101 may preferably contain a resin containing polyvinylidene fluoride (PVDF). When the insulating layer 101 contains PVDF, for example, the insulating layer 101 can swell due to a solvent contained in the electrolytic solution and can be well adhered to the separator 23. The detailed configuration of the positive electrode 21 will be described later.

[0032] FIG. 6A is a developed view of the negative electrode 22, schematically showing the state before winding. FIG. 6B shows the cross-sectional configuration of the negative electrode 22. Note that FIG. 6B shows a cross-section in the arrow viewing direction along the VIB-VIB line shown in FIG. 6A. The negative electrode 22 includes, for example, a negative electrode current collector 22A and a negative electrode active material layer 22B provided on the negative electrode current collector 22A. The negative electrode active material layer 22B may be provided, for example, only on one side of the negative electrode current collector 22A or on both sides of the negative electrode current collector 22A. FIG. 6B shows the case where the negative electrode active material layer 22B is provided on both sides of the negative electrode current collector 22A.

[0033] The negative electrode 22 has a negative electrode covering portion 221 in which the negative electrode active material layer 22B covers the negative electrode current collector 22A, and a negative electrode exposed portion 222 in which the negative electrode current collector 22A is exposed without being covered by the negative electrode active material layer 22B. As shown in FIG. 6A, the negative electrode covering portion 221 and the negative electrode exposed portion 222 each extend along the L-axis direction which is the longitudinal direction. The negative electrode exposed portion 222 extends from the innermost peripheral side end portion to the outermost peripheral side end portion of the electrode wound body 20. In contrast, the negative electrode covering portion 221 is located at the innermost peripheral side end portion and the outermost periphery of the electrode wound body 20 sideIt is not provided at the end. As shown in FIG. 6A, a part of the negative electrode exposed portion 222 is formed so as to sandwich the negative electrode covering portion 221 in the L-axis direction which is the longitudinal direction. Specifically, the negative electrode exposed portion 222 includes a first portion 222A, a second portion 222B, and a third portion 222C. The first portion 222A is provided adjacent to the negative electrode covering portion 221 in the W-axis direction, and extends in the L-axis direction from the innermost peripheral side end portion to the outermost peripheral side end portion of the electrode winding body 20. The second portion 222B and the third portion 222C are provided so as to sandwich the negative electrode covering portion 221 in the L-axis direction. The second portion 222B is located, for example, in the vicinity of the innermost peripheral side end portion of the electrode winding body 20, and the third portion 222C is located in the vicinity of the outermost peripheral side end portion of the electrode winding body 20. As shown in FIG. 1, the first portion 222A of the negative electrode exposed portion 222 is connected to the negative electrode current collector plate 25. The detailed configuration of the negative electrode 22 will be described later.

[0034] In the secondary battery 1, the laminated structure of the electrode winding body 20 S20 is such that the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 are opposed to each other along the W-axis direction which is the width direction, and the positive electrode 21 and the negative electrode 22 are laminated via the separator 23. The end portion of the separator 23 is fixed by attaching a fixing tape 46 to the side surface portion 45 of the electrode winding body 20 so that no unwinding occurs.

[0035] In the secondary battery 1, as shown in FIG. 3, when the width of the positive electrode exposed portion 212 is A and the width of the first portion 222A of the negative electrode exposed portion 222 is B, it is preferable that A > B. For example, when the width A = 7 (mm), the width B = 4 (mm). Also, among the positive electrode exposed portion 212, the width of the portion protruding from the outer edge in the width direction of the separator 23 is C, and among the first portion 222A of the negative electrode exposed portion 222, the outer edge on the opposite side of the width direction of the separator 23 partial When the protruding width is D, it is preferable that C > D. For example, when the width C = 4.5 (mm), the width D = 3 (mm).

[0036] As shown in FIG. 1, at the upper part of the secondary battery 1, a plurality of first edges 212E adjacent to each other in the radial direction (R direction) of the electrode winding body 20 of the positive electrode exposed part 212 wound around the central axis CL are bent toward the central axis CL so as to overlap each other. Similarly, at the lower part of the secondary battery 1, a plurality of second edges 222E adjacent to each other in the radial direction (R direction) of the negative electrode exposed part 222 wound around the central axis CL are bent toward the central axis CL so as to overlap each other. Therefore, a plurality of first edges 212E of the positive electrode exposed part 212 gather on the upper end face 41 of the electrode winding body 20, and a plurality of second edges 222E of the negative electrode exposed part 222 gather on the lower end face 42 of the electrode winding body 20. In order to improve the contact between the positive electrode current collector plate 24 for extracting current and the first edge 212E, the plurality of first edges 212E bent toward the central axis CL are flat surfaces. Similarly, in order to improve the contact between the negative electrode current collector plate 25 for extracting current and the second edge 222E, the plurality of second edges 222E bent toward the central axis CL are flat surfaces. Here, the flat surface referred to here includes not only a completely flat surface but also a surface having some irregularities and surface roughness to such an extent that the positive electrode exposed part 212 and the negative electrode exposed part 222 can be joined to the positive electrode current collector plate 24 and the negative electrode current collector plate 25, respectively.

[0037] The positive electrode current collector 21A is made of, for example, aluminum foil as will be described later. On the other hand, the negative electrode current collector 22A is made of, for example, copper foil as will be described later. In this case, the positive electrode current collector 21A is softer than the negative electrode current collector 22A. That is, the Young's modulus of the positive electrode exposed portion 212 is lower than that of the negative electrode exposed portion 222. For this reason, in one embodiment, it is more preferable that A > B and C > D. In that case, when the positive electrode exposed portion 212 and the negative electrode exposed portion 222 are bent simultaneously from both electrode sides with the same pressure, the height measured from the tip of the separator 23 at the bent portion may be about the same for the positive electrode 21 and the negative electrode 22. At this time, the plurality of first edge portions 212E (FIG. 1) of the positive electrode exposed portion 212 are each bent and appropriately overlap each other. Therefore, the joining of the positive electrode exposed portion 212 and the positive electrode current collecting plate 24 can be easily performed. Similarly, the plurality of second edge portions 222E (FIG. 1) of the negative electrode exposed portion 222 are each bent and appropriately overlap each other. Therefore, the joining of the negative electrode exposed portion 222 and the negative electrode current collecting plate 25 can be easily performed. The joining mentioned here means, for example, being joined together by laser welding, but the joining method is not limited to laser welding.

[0038] Also, as shown in FIGS. 1 and 2, the thick portion 11S2 is located at a position overlapping in the radial direction (R direction) with the end portion on the end face 41 side in the Z direction of the positive electrode active material layer 21B. That is, the secondary battery 1 has an overlapping portion LAP between the thick portion 11S2 and a part of the positive electrode active material layer 21B. The width W-LAP of the overlapping portion LAP between the thick portion 11S2 and the positive electrode active material layer 21B in the Z axis direction is preferably, for example, 0.5 mm or more and 5.0 mm or less. Also, the ratio W-LAP / W-21B of the width W-LAP of the overlapping portion LAP in the Z axis direction to the width W-21B (FIG. 5A) of the positive electrode active material layer 21B in the Z axis direction is preferably, for example, 0.8% or more and 8.5% or less.

[0039] As shown in FIG. 3, among the positive electrode exposed portions 212 of the positive electrode 21, the portion facing the negative electrode 22 with the separator 23 interposed therebetween is covered with the insulating layer 101. The insulating layer 101 has a width of, for example, 3 mm in the W-axis direction. The insulating layer 101 covers all regions of the positive electrode exposed portion 212 of the positive electrode 21 that face the negative electrode covering portion 221 of the negative electrode 22 via the separator 23. The insulating layer 101 can effectively prevent an internal short circuit of the secondary battery 1, for example, when foreign matter intrudes between the negative electrode covering portion 221 and the positive electrode exposed portion 212. Further, when an impact is applied to the secondary battery 1, the insulating layer 101 can absorb the impact and effectively prevent the occurrence of bending of the positive electrode exposed portion 212 and the occurrence of a short circuit between the positive electrode exposed portion 212 and the negative electrode 22.

[0040] (Insulating tapes 53, 54) The secondary battery 1 may further include insulating tapes 53, 54 in the gap between the exterior can 11 and the electrode winding body 20. The positive electrode exposed portions 212 and the negative electrode exposed portions 222 gathered on the end faces 41, 42 are conductors such as bare metal foils. Therefore, if the positive electrode exposed portion 212 and the negative electrode exposed portion 222 are close to the exterior can 11, there is a possibility of a short circuit between the positive electrode 21 and the negative electrode 22 via the exterior can 11. Also, there is a possibility of a short circuit when the positive electrode current collector plate 24 on the end face 41 is close to the exterior can 11. Therefore, it is preferable to provide the insulating tapes 53, 54 as insulating members. The insulating tapes 53, 54 are, for example, adhesive tapes in which the material of the base material layer is composed of any one of polypropylene, polyethylene terephthalate, and polyimide, and which have an adhesive layer on one side of the base material layer. In order not to reduce the volume of the electrode winding body 20 by the installation of the insulating tapes 53, 54, the insulating tapes 53, 54 are arranged so as not to overlap with the fixing tape 46 attached to the side surface portion 45, and the thickness of the insulating tapes 53, 54 is set to be equal to or less than the thickness of the fixing tape 46.

[0041] (Positive electrode current collector plate 24 and negative electrode current collector plate 25) In a normal lithium-ion secondary battery, for example, current-collecting leads for current extraction are welded one by one to the positive electrode and the negative electrode. However, this results in a large internal resistance of the lithium-ion secondary battery, and the lithium-ion secondary battery generates heat and becomes hot during discharge, so it is not suitable for high-rate discharge. Therefore, in the secondary battery 1 of the present embodiment, the positive current collector plate 24 is arranged so as to face the end face 41, and the negative current collector plate 25 is arranged so as to face the end face 42. The positive electrode exposed portion 212 existing on the end face 41 and the positive current collector plate 24 are welded at multiple points, and the negative electrode exposed portion 222 existing on the end face 42 and the negative current collector plate 25 are welded at multiple points. By doing so, the internal resistance of the secondary battery 1 is reduced. The fact that the end faces 41 and 42 are flat surfaces as described above also contributes to reducing the resistance. The positive current collector plate 24 is electrically connected to the battery lid 14 via, for example, the safety valve mechanism 30. The negative current collector plate 25 is electrically connected to the outer can 11, for example. FIG. 7A is a schematic diagram showing a configuration example of the positive current collector plate 24. FIG. 7B is a schematic diagram showing a configuration example of the negative current collector plate 25. The positive current collector plate 24 is a metal plate made of, for example, a single body of aluminum or an aluminum alloy, or a composite material thereof. The negative current collector plate 25 is a metal plate made of, for example, a single body of nickel, a nickel alloy, copper, or a copper alloy, or a composite material of two or more of them.

[0042] As shown in FIG. 7A, the positive electrode current collector 24 has a shape in which a substantially rectangular strip portion 32 is connected to a substantially fan-shaped fan-shaped portion 31. A through hole 35 is formed near the center of the fan-shaped portion 31. In the secondary battery 1, the positive electrode current collector 24 is provided such that the through hole 35 overlaps with the through hole 26 in the Z-axis direction. The portion indicated by the diagonal lines in FIG. 7A is the insulating portion 32A of the strip portion 32. The insulating portion 32A is a part of the strip portion 32 where an insulating tape is attached or an insulating material is applied. Among the strip portion 32, the portion below the insulating portion 32A is the connection portion 32B to the sealing plate that also serves as an external terminal. As shown in FIG. 1, when the secondary battery 1 has a battery structure without a metal center pin in the through hole 26, the strip portion 32 has a low possibility of coming into contact with the negative potential portion. Therefore, the positive electrode current collector 24 may not have the insulating portion 32A. When the positive electrode current collector 24 does not have the insulating portion 32A, the charge and discharge capacity can be increased by widening the widths of the positive electrode 21 and the negative electrode 22 by an amount corresponding to the thickness of the insulating portion 32A.

[0043] The shape of the negative electrode current collector 25 shown in FIG. 7B is almost the same as the shape of the positive electrode current collector 24 shown in FIG. 7A. That is, it has a shape in which a substantially rectangular strip portion 34 is connected to a substantially fan-shaped fan-shaped portion 33. The outer shape of the fan-shaped portion 33 of the negative electrode current collector 25 has a shape surrounded by a contour portion that roughly describes an arc and a contour portion that extends substantially linearly. The strip portion 34 of the negative electrode current collector 25 is different from the strip portion 32 of the positive electrode current collector 24. The strip portion 34 of the negative electrode current collector 25 is shorter than the strip portion 32 of the positive electrode current collector 24, and there is no portion corresponding to the insulating portion 32A of the positive electrode current collector 24. The strip portion 34 is provided with round protrusions 37 indicated by a plurality of circles. During resistance welding, the current concentrates on the protrusions 37, the protrusions 37 melt, and the strip portion 34 is welded to the bottom of the outer can 11. Similar to the positive electrode current collector 24, a through hole 36 is formed near the center of the fan-shaped portion 33 of the negative electrode current collector 25. In the secondary battery 1, the negative electrode current collector 25 is provided such that the through hole 36 overlaps with the through hole 26 in the Z-axis direction.

[0044] Due to its planar shape, the fan-shaped portion 31 of the positive current collector plate 24 is configured to cover only a part of the end face 41. Similarly, due to its planar shape, the fan-shaped portion 33 of the negative current collector plate 25 is configured to cover only a part of the end face 42. There are, for example, two reasons why the fan-shaped portion 31 and the fan-shaped portion 33 do not cover the entire end face 41 and the end face 42. First, for example, it is to smoothly penetrate the electrolyte into the electrode winding body 20 when assembling the secondary battery 1. Second, it is to facilitate the release of gas generated when the lithium-ion secondary battery is in an abnormal high-temperature state or an overcharged state to the outside.

[0045] (Positive current collector 21A) The positive current collector 21A contains a conductive material such as aluminum, for example. The positive current collector 21A is a metal foil made of, for example, aluminum or an aluminum alloy.

[0046] (Positive electrode active material layer 21B) The positive electrode active material layer 21B contains, as the positive electrode active material, any one or two or more kinds of positive electrode materials capable of occluding and releasing lithium. However, the positive electrode active material layer 21B may further contain any one or two or more kinds of other materials such as a positive electrode binder and a positive electrode conductive agent. The positive electrode material is preferably a lithium-containing compound, and more specifically, preferably a lithium-containing composite oxide, a lithium-containing phosphate compound, or the like. The lithium-containing composite oxide is an oxide containing lithium and one or two or more other elements, that is, elements other than lithium, as constituent elements. The lithium-containing composite oxide has, for example, any one of crystal structures such as a layered rock salt type and a spinel type. The lithium-containing phosphate compound is a phosphate compound containing lithium and one or two or more other elements as constituent elements, and has, for example, a crystal structure such as an olivine type. The positive electrode active material layer 21B particularly preferably contains at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide as the positive electrode active material. The positive electrode binder contains, for example, any one or two or more kinds of synthetic rubbers and polymer compounds. The synthetic rubber is, for example, styrene-butadiene rubber, fluorine rubber, ethylene propylene diene, or the like. The polymer compound is, for example, polyvinylidene fluoride, polyimide, or the like. The positive electrode conductive agent contains, for example, any one or two or more kinds of carbon materials. The carbon material is, for example, graphite, carbon black, acetylene black, ketjen black, or the like. However, the positive electrode conductive agent may be a metal material, a conductive polymer, or the like as long as it is a material having conductivity.

[0047] Further, the positive electrode active material layer 21B may contain a fluorine compound and a nitrogen compound. In particular, a positive electrode film containing a fluorine compound and a nitrogen compound may be formed on the surface layer of the positive electrode active material layer 21B. Further, the weight ratio F / N of the fluorine content to the nitrogen content in the positive electrode film of the positive electrode active material layer 21B is preferably 3 or more and 50 or less. In particular, the weight ratio F / N of the fluorine content to the nitrogen content in the positive electrode film of the positive electrode active material layer 21B is preferably 15 or more and 35 or less. Note that the weight ratio F / N of the fluorine content to the nitrogen content in the positive electrode film of the positive electrode active material layer 21B is calculated based on, for example, the spectral peak area of the 1s orbital of nitrogen atoms and the spectral peak area of the 1s orbital of fluorine atoms measured by X-ray photoelectron spectroscopy.

[0048] Further, the areal density of the positive electrode active material layer 21B is 2 21.5 mg / cm or more and 2 23.5 mg / cm or less. This is because the temperature rise of the secondary battery 1 during high-rate charging can be suppressed. Further, Figure 5B as shown in t1 the ratio of the thickness of the positive electrode coating portion 211 to the thickness of the positive electrode current collector 21A, t2 that is, the ratio of the total thickness of the positive electrode current collector 21A and the positive electrode active material layer 21B t2 is preferably 5.0 or more and 6.5 or less. Here, the thickness t2 / t1 of the positive electrode coating portion 211 in the positive electrode 21 is, for example, 60 μm or more and 90 μm or less. Also, the thickness t2 of the positive electrode current collector 21A is, for example, 6 μm or more and 15 μm or less. t1

[0049] (Negative electrode current collector 22A) The negative electrode current collector 22A contains a conductive material such as copper, for example. The negative electrode current collector 22A is a metal foil made of, for example, nickel, a nickel alloy, copper, or a copper alloy. The surface of the negative electrode current collector 22A is preferably roughened. This is because the adhesion of the negative electrode active material layer 22B to the negative electrode current collector 22A is improved due to the so-called anchor effect. In this case, it is sufficient that the surface of the negative electrode current collector 22A is roughened at least in the region facing the negative electrode active material layer 22B. The method of roughening is, for example, a method of forming fine particles using electrolytic treatment. In electrolytic treatment, fine particles are formed on the surface of the negative electrode current collector 22A by electrolysis in an electrolytic cell, so unevenness is provided on the surface of the negative electrode current collector 22A. A copper foil produced by electrolysis is generally called an electrolytic copper foil.

[0050] (Negative electrode active material layer 22B) The negative electrode active material layer 22B contains, as the negative electrode active material, any one or two or more types of negative electrode materials capable of occluding and releasing lithium. However, the negative electrode active material layer 22B may further contain any one or two or more types of other materials such as a negative electrode binder and a negative electrode conductive agent. The negative electrode material is, for example, a carbon material. This is because a very small change in the crystal structure occurs during the occlusion and release of lithium, so a high energy density can be stably obtained. In addition, since the carbon material also functions as a negative electrode conductive agent, the conductivity of the negative electrode active material layer 22B is improved. The carbon material is, for example, easily graphitizable carbon, hardly graphitizable carbon, and graphite. However, the interlayer spacing of the (002) plane in the hardly graphitizable carbon is preferably 0.37 nm or more. The interlayer spacing of the (002) plane in graphite is preferably 0.34 nm or less. More specifically, the carbon material is, for example, pyrolytic carbons, cokes, glassy carbon fibers, fired bodies of organic polymer compounds, activated carbon, and carbon blacks. This coke includes pitch coke, needle coke, and petroleum coke. The fired body of the organic polymer compound is obtained by firing (carbonizing) a polymer compound such as a phenol resin and a furan resin at an appropriate temperature. In addition, the carbon material may be low-crystalline carbon heat-treated at a temperature of about 1000 °C or lower, or amorphous carbon. The shape of the carbon material may be any of fibrous, spherical, granular, and flaky. In the secondary battery 1, when the open circuit voltage at full charge, that is, the battery voltage, is 4.25 V or more, the amount of lithium released per unit mass is larger than that when the open circuit voltage at full charge is 4.20 V, even when the same positive electrode active material is used. Therefore, the amounts of the positive electrode active material and the negative electrode active material are adjusted accordingly. Thereby, a high energy density is obtained.

[0051] Further, the negative electrode active material layer 22B may contain, as the negative electrode active material, a silicon-containing material containing at least one of silicon, silicon oxide, carbon-silicon compound, and silicon alloy. The silicon-containing material is a general term for materials containing silicon as a constituent element. However, the silicon-containing material may contain only silicon as a constituent element. Note that the type of the silicon-containing material may be only one type or two or more types. The silicon-containing material can form an alloy with lithium, and may be a simple substance of silicon, an alloy of silicon, a compound of silicon, a mixture of two or more of them, or a material containing one or two or more phases of them. Further, the silicon-containing material may be crystalline, amorphous, or may contain both a crystalline part and an amorphous part. However, since the simple substance described here means a general simple substance, it may contain a trace amount of impurities. That is, the purity of the simple substance is not necessarily limited to 100%. The alloy of silicon contains, for example, any one or two or more of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium as constituent elements other than silicon. The compound of silicon contains, for example, any one or two or more of carbon and oxygen as constituent elements other than silicon. Note that the compound of silicon may contain any one or two or more of a series of constituent elements described for the alloy of silicon as a constituent element other than silicon. Specifically, the alloy of silicon and the compound of silicon are, for example, SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, and SiO v (0 < v ≤ 2) and the like. However, the range of v can be arbitrarily set, and for example, 0.2 < v < 1.4 may also be acceptable.

[0052] The negative electrode active material layer 22B preferably contains graphite and SiO as the negative electrode active material. In that case, in the negative electrode active material, the ratio of the weight of SiO to the total weight of graphite and SiO may be 3% by weight or more and 15% by weight or less. This is because sufficient capacity can be obtained when it is 3% by weight or more. Also, when it is 15% by weight or less, expansion of the negative electrode is suppressed, and good ion conductivity is ensured by allowing the electrolyte to sufficiently penetrate the negative electrode active material. As a result, the cycle characteristics are improved.

[0053] (Separator 23) The separator 23 is interposed between the positive electrode 21 and the negative electrode 22. The separator 23 allows lithium ions to pass through while preventing a short circuit of the current caused by contact between the positive electrode 21 and the negative electrode 22. The separator 23 is, for example, any one or two or more of porous membranes such as synthetic resin and ceramic, and may be a laminated membrane of two or more porous membranes. The synthetic resin is, for example, polytetrafluoroethylene, polypropylene, polyethylene, etc. However, the separator 23 preferably has a base material made of a single-layer polyolefin porous membrane containing polyethylene. This is because better high-power characteristics can be obtained compared to a laminated membrane. The first separator member 23A and the second separator member 23B If each is a single-layer porous membrane made of polyolefin, the thickness of the porous membrane may be, for example, 10 μm or more and 15 μm or less. When the single-layer porous membrane made of polyolefin has a thickness of 10 μm or more, internal short circuit can be sufficiently avoided. If the thickness of the single-layer porous membrane made of polyolefin is 15 μm or less, better discharge capacity characteristics can be obtained. Also, the areal density of the porous membrane is, for example, 6.3 g / m 2 or more and 8.3 g / m 2 or less. When the areal density of the single-layer porous membrane made of polyolefin is 6.3 g / m 2 or more, internal short circuit can be sufficiently avoided. If the areal density of the single-layer porous membrane made of polyolefin is 8.3 g / m 2 or less, better discharge capacity characteristics can be obtained.

[0054] In particular, the separator 23 may include, for example, the porous film as the base material described above and a polymer compound layer provided on one or both sides thereof. This is because the adhesion of the separator 23 to each of the positive electrode 21 and the negative electrode 22 is improved, suppressing the distortion of the electrode winding body 20. As a result, the decomposition reaction of the electrolytic solution is suppressed, and the leakage of the electrolytic solution impregnated in the base material layer is also suppressed. Therefore, even when charge and discharge are repeated, the resistance hardly increases, and battery swelling is suppressed. The polymer compound layer contains, for example, a polymer compound such as polyvinylidene fluoride. This is because it has excellent physical strength and is electrochemically stable. However, the polymer compound may be other than polyvinylidene fluoride. When forming this polymer compound layer, for example, a solution in which a polymer compound is dissolved in an organic solvent or the like is applied to the base material layer, and then the base material layer is dried. Alternatively, the base material layer may be immersed in the solution and then dried. This polymer compound layer may contain, for example, any one or two or more of insulating particles such as inorganic particles. Examples of the types of inorganic particles are aluminum oxide and aluminum nitride. material The separator 23 may include a porous film as the base material and a polymer compound layer provided on one or both sides thereof. This improves the adhesion of the separator 23 to each of the positive electrode 21 and the negative electrode 22, suppressing the distortion of the electrode winding body 20. As a result, the decomposition reaction of the electrolytic solution is suppressed, and the leakage of the electrolytic solution impregnated in the base material layer is also suppressed. Therefore, even when charge and discharge are repeated, the resistance hardly increases, and battery swelling is suppressed. The polymer compound layer contains a polymer compound such as polyvinylidene fluoride. This is because it has excellent physical strength and is electrochemically stable. However, the polymer compound may be other than polyvinylidene fluoride. When forming this polymer compound layer, for example, a solution in which a polymer compound is dissolved in an organic solvent or the like is applied to the base material layer, and then the base material layer is dried. Alternatively, the base material layer may be immersed in the solution and then dried. This polymer compound layer may contain any one or two or more of insulating particles such as inorganic particles. Examples of the types of inorganic particles are aluminum oxide and aluminum nitride.

[0055] (Electrolytic solution) The electrolytic solution contains a solvent and an electrolyte salt. However, the electrolytic solution may further contain any one or two or more of other materials such as additives. The solvent contains any one or two or more of non-aqueous solvents such as organic solvents. The electrolytic solution containing a non-aqueous solvent is a so-called non-aqueous electrolytic solution. The non-aqueous solvent contains, for example, a fluorine compound and a dinitrile compound. The fluorine compound contains at least one of, for example, fluorinated ethylene carbonate, trifluorocarbonate, trifluoroethyl methyl carbonate, fluorinated carboxylic acid ester, and fluorine ether. Also, the non-aqueous solvent is a nitrile compound other than the dinitrile compound, such as a mononitrile compound or trinitrileIt may further contain at least one of the compounds. As the dinitrile compound, for example, succinonitrile (SN) is preferred. However, the dinitrile compound is not limited to succinonitrile, and other dinitrile compounds such as adiponitrile may also be used.

[0056] The electrolyte salt contains, for example, any one or two or more of salts such as lithium salts. However, the electrolyte salt may contain, for example, salts other than lithium salts. These salts other than lithium are, for example, salts of light metals other than lithium. The lithium salts include, for example, 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 (Li2 salt F6), lithium chloride (LiCl), lithium bromide (LiBr), and the like. Among them, any one or two or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate are preferred, and lithium hexafluorophosphate is more preferred. The content of the electrolyte salt is not particularly limited, but among them, it is preferably 0.3 mol / kg to 3 mol / kg with respect to the solvent. When the electrolytic solution contains LiPF6 as the electrolyte salt, the concentration of LiPF6 in the electrolytic solution is preferably 1.25 mol / kg or more and 1.45 mol / kg or less. This is because the cycle degradation due to the consumption (decomposition) of the salt during high-rate charging can be prevented, and the high-load cycle characteristics are improved. When the electrolyte salt further contains LiBF4 in addition to LiPF6, the concentration of LiBF4 in the electrolytic solution is preferably 0.001 (wt%) or more and 0.1 (wt%) or less. This is because the cycle degradation due to the consumption (decomposition) of the salt during high-rate charging can be more effectively prevented, and the high-load cycle characteristics are further improved. Si F6), lithium chloride (LiCl), lithium bromide (LiBr), and the like. Among them, any one or two or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate are preferred, and lithium hexafluorophosphate is more preferred. The content of the electrolyte salt is not particularly limited, but among them, it is preferably 0.3 mol / kg to 3 mol / kg with respect to the solvent. When the electrolytic solution contains LiPF6 as the electrolyte salt, the concentration of LiPF6 in the electrolytic solution is preferably 1.25 mol / kg or more and 1.45 mol / kg or less. This is because the cycle degradation due to the consumption (decomposition) of the salt during high-rate charging can be prevented, and the high-load cycle characteristics are improved. When the electrolyte salt further contains LiBF4 in addition to LiPF6, the concentration of LiBF4 in the electrolytic solution is preferably 0.001 (wt%) or more and 0.1 (wt%) or less. This is because the cycle degradation due to the consumption (decomposition) of the salt during high-rate charging can be more effectively prevented, and the high-load cycle characteristics are further improved.

[0057] [1-2. Operation] In the secondary battery 1 of the present embodiment, for example, during charging, lithium ions are released from the positive electrode 21 and the lithium ions are occluded in the negative electrode 22 through the electrolyte. Further, in the secondary battery 1, for example, during discharging, lithium ions are released from the negative electrode 22 and the lithium ions are occluded in the positive electrode 21 through the electrolyte.

[0058] [1-3. Manufacturing method] With reference to FIG. 8 in addition to FIGS. 1 to 7B, the manufacturing method of the secondary battery 1 will be described. FIG. 8 is a perspective view for explaining the manufacturing process of the secondary battery shown in FIG. 1.

[0059] First, a positive electrode current collector 21A is prepared, and by selectively forming a positive electrode active material layer 21B on the surface of the positive electrode current collector 21A, a positive electrode 21 having a positive electrode covering portion 211 and a positive electrode exposed portion 212 is formed. Next, a negative electrode current collector 22A is prepared, and by selectively forming a negative electrode active material layer 22B on the surface of the negative electrode current collector 22A, a negative electrode 22 having a negative electrode covering portion 221 and a negative electrode exposed portion 222 is formed. The positive electrode 21 and the negative electrode 22 may be subjected to a drying process. Subsequently, the positive electrode 21 and the negative electrode 22 are stacked via a first separator member 23A and a second separator member 23B such that the first portion 222A of the positive electrode exposed portion 212 and the negative electrode exposed portion 222 are on opposite sides in the W-axis direction to produce a laminated structure S20. When producing the laminated structure S20, the inner peripheral side end part and of the first separator member 23A and the inner peripheral side end of the second separator member part are folded back, and these inner peripheral side ends part and and the inner peripheral side ends part are sandwiched between the inner peripheral side edge 21E2 of the positive electrode 21 and the negative electrode 22. Thereafter, the laminated structure S20 is wound in a spiral shape so that a through hole 26 is formed. Further, a fixing tape 46 is attached to the outermost periphery of the spirally wound laminated structure S20. Thereby, as shown in FIG. 8(A), an electrode wound body 20 is obtained.

[0060] Next, as shown in FIG. 8(B), for example, by pressing the end of a flat plate with a thickness of 0.5 mm or the like perpendicular to the end faces 41 and 42 of the electrode wound body 20, that is, in the Z-axis direction, the end faces 41 and 42 are locally bent. As a result, grooves 43 extending radially in the radial direction (R direction) from the through holes 26 are formed. Note that the number and arrangement of the grooves 43 shown in FIG. 8(B) are examples, and the present disclosure is not limited thereto.

[0061] Subsequently, as shown in FIG. 8(C), substantially simultaneously from above and below the electrode wound body 20, and substantially the same pressure is applied in a direction substantially perpendicular to the end face 41 and the end face 42. At this time, for example, a rod-shaped jig is inserted into the through hole 26. By doing so, the first part 222A of the positive electrode exposed portion 212 and the negative electrode exposed portion 222 are bent respectively so that the end faces 41 and 42 become flat surfaces. At this time, the first edge portion 212E of the positive electrode exposed portion 212 and the second edge portion 222E of the negative electrode exposed portion 222 on the end faces 41 and 42 are bent so as to overlap toward the through hole 26. After that, the fan-shaped portion 31 of the positive electrode current collector plate 24 is joined to the end face 41 by laser welding or the like, and the fan-shaped portion 33 of the negative electrode current collector plate 25 is joined to the end face 42 by laser welding or the like.

[0062] Next, insulating tapes 53 and 54 are attached to a predetermined position of the electrode wound body 20. After that, as shown in FIG. 8(D), the strip-shaped portion 32 of the positive electrode current collector plate 24 is bent, and the strip-shaped portion 32 is inserted into the hole 12H of the insulating plate 12. Further, the strip-shaped portion 34 of the negative electrode current collector plate 25 is bent, and the strip-shaped portion 34 is inserted into the hole 13H of the insulating plate 13.

[0063] Next, after inserting the electrode wound body 20 assembled as described above into the exterior can 11 shown in FIG. 8(E), the bottom of the exterior can 11 and the negative electrode current collector plate 25 are welded. After that, a constricted portion is formed in the vicinity of the open end portion 11N of the exterior can 11. Further, after injecting the electrolytic solution into the exterior can 11, the strip-shaped portion 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 are welded.

[0064] Next, as shown in (F) of FIG. 8, it is sealed with the gasket 15, the safety valve mechanism 30, and the battery cover 14.

[0065] Thus, the secondary battery 1 of the present embodiment is completed.

[0066] [1-4. Action and Effect] As described above, according to the secondary battery 1 of the present embodiment, the thick portion 11S2 of the outer can 11 and the end portion on the end face 41 side of the positive electrode active material layer 21B are provided with an overlapping portion LAP that overlaps each other in the R direction. For this reason, the thick portion 11S2 protruding inside the outer can 11 biases the portion near the end face 41 of the electrode winding body 20 toward the central axis CL along the R direction. As a result, the widening of the distance between the end portion on the end face 41 side of the outermost peripheral portion 21out of the positive electrode and the end portion on the end face 41 side of the outermost peripheral portion 22out of the negative electrode can be suppressed. That is , in the overlapping portion LAP, the distance between the positive electrode 21 and the negative electrode 22 is appropriately maintained. For this reason, in the secondary battery 1, during charging, the deposition of the electrode reaction substance (lithium) on the surface of the negative electrode 22 is suppressed, and high safety is obtained.

[0067] The secondary battery 1 adopts a so-called tabless structure. Therefore, at the end face 41, as shown in FIG. 1 etc., a plurality of first edge portions 212E of the positive electrode current collector 21A are bent toward the central axis CL so as to overlap each other. Thus, at the facing portions of the positive electrode 21 and the negative electrode 22 other than the facing portion FA1 (FIG. 4) between the outermost peripheral portion 21out of the positive electrode and the outermost peripheral portion 22out of the negative electrode, the distance between the positive electrode 21 and the negative electrode 22 is likely to be appropriately maintained. On the other hand, since the positive electrode 21 does not exist on the outer peripheral side of the outermost peripheral portion 22out of the negative electrode, it is in a situation where it is likely to be separated from the outermost peripheral portion 21out of the positive electrode. If the distance between the positive electrode 21 and the negative electrode 22 widens, there is a possibility that lithium metal may precipitate on the negative electrode 22 without being charged. Therefore, in the secondary battery 1, the thick portion 11S2 is used to apply a biasing force toward the central axis CL along the R direction to the outermost peripheral portion 22out of the negative electrode. By doing so, the distance between the two can be appropriately maintained also in the facing portion FA1 between the outermost peripheral portion 21out of the positive electrode and the outermost peripheral portion 22out of the negative electrode. As a result, in the secondary battery 1, during charging, the precipitation of the electrode reactant (lithium) on the surface of the negative electrode 22 is suppressed, and high safety can be obtained.

[0068] In the secondary battery 1 of the present embodiment, in particular, by setting the thickness T2 of the thick portion 11S2 to be 110% or more of the thickness T1 of the thin portion 11S1, the widening of the distance between the positive electrode 21 and the negative electrode 22 can be suppressed. As a result, the precipitation of the electrode reactant (lithium) on the surface of the negative electrode 22 is further suppressed, and higher safety can be obtained. Further, by setting the thickness T2 of the thick portion 11S2 to be 180% or less of the thickness T1 of the thin portion 11S1, the expansion of the negative electrode 22 can be effectively suppressed. For this reason, the electrolytic solution can sufficiently reach the negative electrode active material, and better ion conductivity can be ensured. Therefore, the cycle characteristics can be further improved.

[0069] [2 - 1. Battery Pack] The use of the lithium ion secondary battery 1 as one embodiment of the present disclosure described above is as follows, for example.

[0070] [2 - 1. Battery Pack] FIG. 9 is a block diagram showing an example of a circuit configuration when a battery (hereinafter, appropriately referred to as a secondary battery) according to an embodiment of the present invention is applied to a battery pack. 300 The battery pack 300 includes an assembled battery 301, an exterior, a charging control switch 302a, and a switch unit 304 including a discharging control switch 303a, a current detection resistor 307, a temperature detection element 308, and a control unit 310.

[0071] The battery pack 300 includes a positive electrode terminal 321 and a negative electrode terminal 322. During charging, the positive electrode terminal 321 and the negative electrode terminal 322 are connected to the positive electrode terminal and the negative electrode terminal of a charger, respectively, and charging is performed. Also, when an electronic device is in use, the positive electrode terminal 321 and the negative electrode terminal 322 are connected to the positive electrode terminal and the negative electrode terminal of the electronic device, respectively, and discharging is performed.

[0072] The assembled battery 301 is formed by connecting a plurality of secondary batteries 301a in series or in parallel. As the secondary battery 301a, the above-described secondary battery 1 can be applied. In FIG. 9, a case where six secondary batteries 301a are connected in 2 parallel and 3 series (2P3S) is shown as an example, but any other connection method such as n parallel and m series (n, m are integers) may be used.

[0073] The switch unit 304 includes a charging control switch 302a and a diode 302b, and a discharging control switch 303a and a diode 303b, and is controlled by the control unit 310. The diode 302b has a polarity that is reverse to the charging current flowing from the positive electrode terminal 321 toward the assembled battery 301 and forward to the discharging current flowing from the terminal 322 toward the assembled battery 301. The diode 303b has a polarity that is forward to the charging current and reverse to the discharging current. In FIG. 9, the switch unit 304 is provided on the + side, but it may be provided on the - side. negative electrode The diode 303b has a polarity that is forward to the charging current and reverse to the discharging current. In FIG. 9, the switch unit 304 is provided on the + side, but it may be provided on the - side.

[0074] The charging control switch 302a is turned off when the battery voltage reaches the overcharge detection voltage, and is controlled by the charge and discharge control unit so that the charging current does not flow through the current path of the battery pack 301. After the charging control switch 302a is turned off, only discharging is possible through the diode 302b. Also, when a large current flows during charging, it is turned off and controlled by the control unit 310 to cut off the charging current flowing through the current path of the battery pack 301. The discharge control switch 303a is turned off when the battery voltage reaches the overdischarge detection voltage, and is controlled by the control unit 310 so that the discharge current does not flow through the current path of the battery pack 301. After the discharge control switch 303a is turned off, only charging is possible through the diode 303b. Also, when a large current flows during discharging, it is turned off and controlled by the control unit 310 to cut off the discharge current flowing through the current path of the battery pack 301.

[0075] The temperature detection element 308 is a thermistor, for example, and is provided near the battery pack 301 to measure the temperature of the battery pack 301 and supply the measured temperature to the control unit 310. The voltage detection unit 311 measures the voltages of the battery pack 301 and each secondary battery 301a constituting it, A / D-converts the measured voltages, and supplies them to the control unit 310. The current measurement unit 313 measures the current using the current detection resistor 307 and supplies the measured current to the control unit 310. The switch control unit 314 controls the charging control switch 302a and the discharge control switch 303a of the switch unit 304 based on the voltage and current input from the voltage detection unit 311 and the current measurement unit 313.

[0076] When the voltage of any one of the plurality of secondary batteries 301a becomes equal to or lower than the overcharge detection voltage or the overdischarge detection voltage, or when a large current suddenly flows, the switch control unit 314 sends a control signal to the switch unit 304 to prevent overcharging, overdischarging, and overcurrent charge and discharge. Here, for example, when the secondary battery is a lithium-ion secondary battery, the overcharge detection voltage is set to, for example, 4.20 V ± 0.05 V, and the overdischarge detection voltage is set to, for example, 2.4 V ± 0.1 V.

[0077] Charge and dischargecontrol As the switch, a semiconductor switch such as a MOSFET can be used. In this case, the parasitic diodes of the MOSFET function as diodes 302b and 303b. Charging and discharging control When a P-channel type FET is used as the switch, the switch control unit 314 supplies control signals DO and CO to the respective gates of the charge control switch 302a and the discharge control switch 303a. When the charge control switch 302a and the discharge control switch 303a are of P-channel type, they turn ON by a gate potential that is lower than the source potential by a predetermined value or more. That is, in normal charging and discharging operations, the control signals CO and DO are set to the low level, and the charge control switch 302a and the discharge control switch 303a are turned ON.

[0078] For example, in the case of overcharging or over-discharging, the control signals CO and DO are set to the high level, and the charge control switch 302a and the discharge control switch 303a are turned OFF.

[0079] The memory 317 consists of a RAM or a ROM, and for example, it consists of an EPROM (Erasable Programmable Read Only Memory) which is a non-volatile memory. In the memory 317, numerical values calculated by the control unit 310, internal resistance values of the batteries in the initial states of the respective secondary batteries 301a measured at the manufacturing process stage, etc. are stored in advance, and can also be rewritten as appropriate. Also, by storing the full charge capacity of the secondary battery 301a, the remaining capacity can be calculated together with the control unit 310, for example.

[0080] The temperature detection unit 318 measures the temperature using the temperature detection element 308, and performs charge and discharge control during abnormal heat generation, or performs correction in the calculation of the remaining capacity.

[0081] [2-2. Power storage system] The secondary battery according to the above-described embodiment of the present disclosure can be mounted on devices such as electronic devices, electric vehicles, electric aircraft, power storage devices, etc., or can be used to supply power.

[0082] Examples of electronic devices include, for example, notebook computers, smartphones, tablet terminals, PDAs (personal digital assistants), mobile phones, wearable terminals, cordless phone handsets, video movies, digital still cameras, e-books, electronic dictionaries, music players, radios, headphones, game machines, navigation systems, memory cards, pacemakers, hearing aids, power tools, electric shavers, refrigerators, air conditioners, televisions, stereos, water heaters, microwave ovens, dishwashers, washing machines, dryers, lighting devices, toys, medical devices, robots, road conditioners, traffic lights, etc.

[0083] Examples of electric vehicles include railway vehicles, golf carts, electric carts, electric automobiles (including hybrid automobiles), etc., and these are used as drive power sources or auxiliary power sources. Examples of power storage devices include power storage power sources for buildings such as houses and power generation facilities.

[0084] Hereinafter, among the above-described application examples, specific examples of a power storage system using a power storage device to which the secondary battery 1 of the present disclosure described above is applied will be described.

[0085] (Power tool) With reference to FIG. 10, an example of an electric driver as a power tool to which the secondary battery of the present disclosure is applicable will be schematically described. In the electric driver 431, a motor 433 such as a DC motor is housed inside the main body. The rotation of the motor 433 is transmitted to the shaft 434, and a screw is driven into an object by the shaft 434. The electric driver 431 is provided with a trigger switch 432 that is operated by the user.

[0086] The battery pack 430 and the motor control unit 435 are housed in the lower housing of the grip of the electric driver 431. The battery pack 300 can be used as the battery pack 430. The motor control unit 435 controls the motor 433. Each part of the electric driver 431 other than the motor 433 may be controlled by the motor control unit 435. The battery pack 430 and the electric driver 431 are engaged by engaging members provided respectively thereon. As will be described later, each of the battery pack 430 and the motor control unit 435 is provided with a microcomputer. Battery power is supplied from the battery pack 430 to the motor control unit 435, and information on the battery pack 430 is communicated between the microcomputers of both.

[0087] The battery pack 430 is, for example, detachable from the electric driver 431. The battery pack 430 may be built into the electric driver 431. The battery pack 430 is attached to a charging device during charging. Note that when the battery pack 430 is attached to the electric driver 431, a part of the battery pack 430 may be exposed outside the electric driver 431 so that the user can visually recognize the exposed portion. For example, an LED may be provided on the exposed portion of the battery pack 430 so that the user can confirm the lighting and extinguishing of the LED.

[0088] The motor control unit 435 controls, for example, the rotation and stop of the motor 433 and the rotation direction thereof. Further, the power supply to the load is cut off during over-discharge. The trigger switch 432 is inserted, for example, between the motor 433 and the motor control unit 435. When the user pushes in the trigger switch 432, power is supplied to the motor 433 and the motor 433 rotates. When the user returns the trigger switch 432, the rotation of the motor 433 stops.

[0089] (Unmanned Aerial Vehicle) An example of applying the secondary battery of the present disclosure to a power source for an electric aircraft will be described with reference to FIG. 11. The secondary battery of the present disclosure can be applied as a power source for an unmanned aircraft such as a drone. FIG. 11 is a plan view of the unmanned aircraft. The base of the unmanned aircraft includes a cylindrical or rectangular tube-shaped body part as the central part and support shafts 442a to 442f fixed to the upper part of the body part. In FIG. 11, the body part has a hexagonal tube shape, and six support shafts 442a to 442f extend radially from the center of the body part at equal angular intervals. The body part and the support shafts 442a to 442f are made of a lightweight and high-strength material.

[0090] Motors 443a to 443f as drive sources for the rotary wings are respectively attached to the tip ends of the support shafts 442a to 442f. Rotary wings 444a to 444f are attached to the rotating shafts of the motors 443a to 443f. A circuit unit 445 including a motor control circuit for controlling each motor is attached to the central part (the upper part of the body part) where the support shafts 442a to 442f intersect.

[0091] Furthermore, a battery part as a power source is arranged at a position below the body part. The battery part has three battery packs so as to supply power to pairs of motors and rotary wings having an opposing interval of 180 degrees. Each battery pack has, for example, a lithium-ion secondary battery and a battery control circuit for controlling charge and discharge. The battery pack 300 can be used as the battery pack. Motors 443a and rotary wing 444a, and motors 443d and rotary wing 444d form a pair. Similarly, motors 443b and rotary wing 444b, and motors 443e and rotary wing 444e form a pair, and motors 443c and rotary wing 444c, and motors 443f and rotary wing 444f form a pair. The number of these pairs is equal to the number of battery packs.

[0092] (Vehicle power storage system) An example of applying the secondary battery of the present disclosure to a power storage system for an electric vehicle will be described with reference to FIG. 12. FIG. 12 schematically shows an example of the configuration of a hybrid vehicle employing a series hybrid system to which the secondary battery of the present disclosure is applied. A series hybrid system is a vehicle that runs using a power drive force conversion device with electric power generated by a generator driven by an engine or electric power once stored in a battery.

[0093] The hybrid vehicle 600 is equipped with an engine 601, a generator 602, a power drive force conversion device 603, drive wheels 604a, drive wheels 604b, wheels 605a, wheels 605b, a battery 608, a vehicle control device 609, various sensors 610, and a charging port 611. For the battery 608, the battery pack 300 of the present disclosure described above can be applied.

[0094] The hybrid vehicle 600 runs using the power drive force conversion device 603 as a power source. An example of the power drive force conversion device 603 is a motor. The power drive force conversion device 603 operates by the electric power of the battery 608, and the rotational force of this power drive force conversion device 603 is transmitted to the drive wheels 604a and 604b. Note that by using DC-AC (direct current - alternating current) or inverse conversion (AC-DC conversion) at necessary locations, the power drive force conversion device 603 can be applied to either an AC motor or a DC motor. The various sensors 610 control the engine speed or the opening degree of a throttle valve (throttle opening degree) (not shown) via the vehicle control device 609. The various sensors 610 include a speed sensor, an acceleration sensor, an engine speed sensor, and the like.

[0095] The rotational force of the engine 601 is transmitted to the generator 602, and it is possible to store the electric power generated by the generator 602 by that rotational force in the battery 608. When the hybrid vehicle 600 decelerates by a braking mechanism (not shown), the resistance force during deceleration is applied as a rotational force to the power drive force conversion device 603, and the regenerative electric power generated by the power drive force conversion device 603 by this rotational force is stored in the battery 608.

[0096] The battery 608 can also be connected to an external power source of the hybrid vehicle 600, receive power supply from the external power source through the charging port 611 as an input port, and store the received power.

[0097] Furthermore, an information processing device that performs information processing related to vehicle control based on information about the secondary battery may be provided. Examples of such an information processing device include an information processing device that displays the remaining battery level based on information about the remaining amount of the secondary battery.

[0098] Note that the above has been described by taking a series hybrid vehicle that runs on a motor using the power generated by a generator driven by an engine or the power once stored in a battery as an example. However, the secondary battery of the present disclosure can also be effectively applied to a parallel hybrid vehicle in which both the outputs of the engine and the motor serve as drive sources, and the vehicle runs in three modes: only on the engine, only on the motor, and on both the engine and the motor, and the modes are appropriately switched and used. Furthermore, the secondary battery of the present disclosure can also be effectively applied to a so-called electric vehicle that runs only by a drive motor without using an engine.

Embodiment

[0099] Embodiments of the present disclosure will be described.

[0100] (Embodiment 1) As described below, after manufacturing the cylindrical secondary battery 1 shown in FIG. 1 and the like, its battery characteristics were evaluated. Here, a secondary battery 1 having dimensions of a diameter of 21.2 mm and a length of 70 mm was manufactured.

[0101] [Manufacturing method] First, an aluminum foil with a thickness of 12 μm was prepared as the positive electrode current collector 21A. Next, a positive electrode mixture was obtained by mixing a layered lithium oxide with an Ni ratio of 85% or more of lithium nickel cobalt aluminum oxide (NCA) as the positive electrode active material, a positive electrode binder made of polyvinylidene fluoride, and a conductive aid in which carbon black, acetylene black, and ketjen black were mixed. The mixing ratio of the positive electrode active material, the positive electrode binder, and the conductive aid was 96.4:2:1.6. Subsequently, after the positive electrode mixture was put into an organic solvent (N-methyl-2-pyrrolidone), the organic solvent was stirred to prepare a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was applied to a predetermined region on both sides of the positive electrode current collector 21A using a coating device, and then the positive electrode mixture slurry was dried to form the positive electrode active material layer 21B. Also, a paint containing polyvinylidene fluoride (PVDF) was applied and dried to form an insulating layer 101 with a width of 3 mm and a thickness of 8 μm at a site on the surface of the positive electrode exposed portion 212 adjacent to the positive electrode coating portion 211. Thereafter, the positive electrode active material layer 21B was compression-molded using a roll press. Thus, a positive electrode 21 having a positive electrode coating portion 211 and a positive electrode exposed portion 212 was obtained. Here, the width of the positive electrode coating portion 211 in the W-axis direction was set to 60 mm, and the width of the positive electrode exposed portion 212 in the W-axis direction was set to 7 mm. Also, the length of the positive electrode 21 in the L-axis direction was set to 1700 mm. In the obtained positive electrode 21, the areal density of the positive electrode active material layer 21B was 22.0 mg / cm 2 and the volume density of the positive electrode active material layer 21B was 3.55 g / cm 3 . Also, the thickness of the positive electrode coating portion 211 t1 was 74.2 μm.

[0102] Further, a copper foil with a thickness of 8 μm was prepared as the negative electrode current collector 22A. Next, a negative electrode active material obtained by mixing a carbon material made of natural graphite and SiO at a weight ratio of 93.75:6.25, a negative electrode binder made of polyvinylidene fluoride, and a conductive aid in which carbon black, acetylene black, and ketjen black were mixed were mixed to obtain a negative electrode mixture. The mixing ratio of the negative electrode active material, the negative electrode binder, and the conductive aid was 96.1:2.9:1.0. Also, among the negative electrode active materials, the mixing ratio of graphite and SiO was 95:5. Subsequently, after the negative electrode mixture was put into an organic solvent (N-methyl-2-pyrrolidone), the organic solvent was stirred to prepare a paste-like negative electrode mixture slurry. Subsequently, using a coating device, the negative electrode mixture slurry was applied to a predetermined region on both sides of the negative electrode current collector 22A, and then the negative electrode mixture slurry was dried to form a negative electrode active material layer 22B. Thereafter, the negative electrode active material layer 22B was compression-molded using a roll press. Thus, a negative electrode 22 having a negative electrode coated portion 221 and a negative electrode exposed portion 222 was obtained. Here, the width of the negative electrode coated portion 221 in the W-axis direction was 62 mm, and the width of the first portion 222A of the negative electrode exposed portion 222 in the W-axis direction was 4 mm. Also, the length of the negative electrode 22 in the L-axis direction was 1750 mm. In the obtained negative electrode 22, the areal density of the negative electrode active material layer 22B was 10.82 mg / cm 2 and the volume density of the negative electrode active material layer 22B was 1.50 g / cm 3 It was. Also, the thickness of the negative electrode coated portion 221 was 80.1 μm.

[0103] Subsequently, the positive electrode 21 and the negative electrode 22 are stacked via the first separator member 23A and the second separator member 23B such that the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 are on opposite sides in the W-axis direction, thereby producing a laminated structure S20. At this time, the laminated structure S20 was produced so that the positive electrode active material layer 21B does not protrude from the negative electrode active material layer 22B in the W-axis direction. As the first separator member 23A and the second separator member 23B, a polyethylene sheet having a width of 65 mm and a thickness of 14 μm was used. When producing the laminated structure S20, the inner peripheral side end 23A1 of the first separator member 23A and the inner peripheral side end 23B1 of the second separator member are folded back, and the inner peripheral side end 23A1 and the inner peripheral side end 23B1 are sandwiched between the inner peripheral side edge 21E2 of the positive electrode 21 and the negative electrode 22. then After that, the laminated structure S20 was wound in a spiral shape so that the through hole 26 is formed, and a fixing tape 46 was attached to the outermost periphery of the wound laminated structure S20. Thereby, the electrode wound body 20 was obtained. The outer diameter of the obtained electrode wound body 20 was 20.55 mm. Here, the maximum outer diameter and the minimum outer diameter of the electrode wound body 20 were measured using "Magnescale U30B-J" and "Gauge Stand DZ521" manufactured by Sony Corporation, and the average value thereof was taken as the outer diameter of the electrode wound body 20.

[0104] Next, by pressing the end of a flat plate with a thickness of 0.5 mm against the end faces 41 and 42 of the electrode wound body 20 in the Z-axis direction, the end faces 41 and 42 were locally bent to produce grooves 43 extending radially in the radial direction (R direction) from the through hole 26.

[0105] Subsequently, by applying substantially the same pressure from above and below the electrode winding body 20 simultaneously and in a direction substantially perpendicular to the end faces 41 and 42, the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 were bent respectively, and the end faces 41 and 42 were made flat surfaces. At this time, the first edge portion 212E of the positive electrode exposed portion 212 and the second edge portion 222E of the negative electrode exposed portion 222 on the end faces 41 and 42 were bent so as to overlap toward the through hole 26. Then, the fan-shaped portion 31 of the positive electrode current collector plate 24 was joined to the end face 41 by laser welding, and the fan-shaped portion 33 of the negative electrode current collector plate 25 was joined to the end face 42 by laser welding.

[0106] Next, after insulating tapes 53 and 54 were attached to a predetermined position of the electrode winding body 20, the strip portion 32 of the positive electrode current collector plate 24 was bent and the strip portion 32 was inserted into the hole 12H of the insulating plate 12, and the strip portion 34 of the negative electrode current collector plate 25 was bent and the strip portion 34 was inserted into the hole 13H of the insulating plate 13.

[0107] Next, after the electrode winding body 20 assembled as described above was inserted into the outer can 11, the bottom of the outer can 11 and the negative electrode current collector plate 25 were welded. Then, a constricted portion was formed in the vicinity of the open end portion 11N of the outer can 11. Further, after the electrolytic solution was injected into the outer can 11, the strip portion 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 were welded.

[0108] As the electrolytic solution, a solvent in which fluoroethylene carbonate (FEC) and succinonitrile (SN) were added to ethylene carbonate (EC) and dimethyl carbonate (DMC) as main solvents, and a material containing LiBF4 and LiPF6 as electrolyte salts were used. In the lithium ion secondary battery of this example, the content ratio (weight %) of each of EC, DMC, FEC, SN, LiBF4, and LiPF6 in the electrolytic solution was 12.7:56.2:12.0:1.0:1.0:17.1.

[0109] Finally, it was sealed with the gasket 15, the safety valve mechanism 30, and the battery lid 14 using the constricted portion.

[0110] As described above, the secondary battery 1 of Example 1 was obtained. Here, the ratio T2 / T1 of the thickness T2 of the thick portion 11S2 to the thickness T1 of the thin portion 11S1 was set to 145%, the ratio IR1 / IR2 of the inner diameter IR1 to the inner diameter IR2 was set to 100.87%, the width W-LAP of the overlapping portion LAP was set to 3.0 mm, and the ratio W-LAP / W-21B of the width W-LAP to the width W-21B of the positive electrode active material layer 21B was set to 5.1%. The inner diameter IR1 of the thin portion 11S1 was set to 20.80 mm, and the inner diameter IR2 of the thick portion 11S2 was set to 20.62 mm. The measurement position of the inner diameter IR1 of the thin portion 11S1 was in the range 2 ± 1 mm below the thick portion 11S2. The measurement of the inner diameters IR1 and IR2 was performed as follows. (1) A 1 Ω resistor was connected to the secondary battery and left for 24 hours, and then discharged until the open circuit voltage OCV became 0.3 V or less. (2) The discharged secondary battery was fixed with an epoxy mount resin (Refine Tech Co., Ltd. Epomount B Set). (3) The resin-fixed secondary battery was cut along the radial direction with a BUEHLER IsoMet 1000 to form a cut surface orthogonal to the height direction. (4) The cut surface was polished with a BUEHLER AutoMet 250. (5) The polished cut surface was observed using a KEYENCE VR-3200, plotted at three points, and approximated by a circle to measure the inner diameters IR1 and IR2.

[0111] [Evaluation of Battery Characteristics] When the battery characteristics of the secondary battery 1 of Example 1 obtained as described above were evaluated, the results shown in Table 1 were obtained. Specifically, confirmation of the presence or absence of lithium precipitation after the first charge and the presence or absence of uncharged portions, measurement of the initial capacity [mAh], measurement of the number of cycles [times] until the capacity decreased to 70% in the cycle test, and confirmation of the presence or absence of electrode breakage after the cycle test were performed. The implementation environmental temperature was 23 ± 1°C. The evaluation results of the battery characteristics are shown in Table 1.

[0112]

Table 1

[0113] For the initial charge, constant current constant voltage (CC-CV) charging was carried out. It was charged at a constant current of 4.0 A until the voltage reached 4.2 V, and then charged at a constant voltage of 4.2 V. The cut-off current was set to 0.05 A. After the initial charge, the secondary battery was disassembled, and the presence or absence of lithium precipitation and the presence or absence of uncharged parts were judged by visually observing the electrode surface. Lithium precipitation means a state in which lithium metal is precipitated on the surface of the negative electrode. The uncharged part means a state in which an uncharged part exists in a part of the negative electrode facing the positive electrode.

[0114] The initial capacity [mAh] was obtained as follows. First, constant current constant voltage (CC-CV) charging was carried out. Specifically, it was charged at a constant current of 4.0 A until the voltage reached 4.2 V, and then charged at a constant voltage of 4.2 V. The cut-off current was set to 0.05 A. Thereafter, constant current (CC) discharge was carried out. Specifically, it was discharged at a constant current of 0.8 A, and the cut-off voltage was set to 2.0 V.

[0115] The test conditions for the cycle test are as follows. (1) Charging conditions: Constant current constant voltage (CC-CV) charging was carried out. It was charged at a constant current of 6 A until the voltage reached 4.2 V, and then charged at a constant voltage of 4.2 V. The cut-off current was set to 1 A. (2) Rest time after charging: It was set to 30 minutes. (3) Discharge conditions: Constant current (CC) discharge was carried out at a constant current of 50 A. The cut-off voltage was set to 2.5 V. Or the discharge was stopped when the temperature reached 85°C. (4) Rest after discharge: It was rested until the battery surface temperature was less than 30°C. 。 (5) Number of cycles: It was set to the number of cycles required until the capacity decreased to 70% of the initial capacity.

[0116] Also, the presence or absence of electrode breakage after the cycle test was confirmed as follows. First, the secondary battery after the cycle test was disassembled, and the positive electrode and the negative electrode were separated. Next, each of the positive electrode and the negative electrode was visually observed from the back side with light irradiated from the front side. At that time, if leakage light was observed on the back side, it was determined that there was electrode breakage because a crack had occurred in a part of the positive electrode or a part of the negative electrode.

[0117] (Examples 2 to 8) A secondary battery was produced in the same manner as in Example 1 except that T2 / T1, IR1 / IR2, W-LAP, and W-LAP / W-21B were set as shown in Table 1, and the same evaluation as in Example 1 was performed. The results are shown in Table 1 together. In Examples 4, 5, 7, and 8, while the inner diameter IR1 of the thin portion 11S1 was 20.80 mm, the same as in Example 1, the ratio IR1 / IR2 was changed by changing the inner diameter IR2 of the thick portion 11S2.

[0118] (Examples 9 to 11) A secondary battery was fabricated in the same manner as in Example 1, except that the weight ratio of SiO contained in the negative electrode active material was set as shown in Table 1, that is, except that the energy density of the negative electrode active material was changed, and the same evaluations as in Example 1 were performed. The results are shown together in Table 1. Note that by changing the weight ratio of SiO contained in the negative electrode active material, the thickness of the negative electrode 22 will change. Therefore, if the lengths of the positive electrode 21 and the negative electrode 22 in the L-axis direction are kept the same as in Example 1, the outer diameter of the electrode wound body 20 will be different from that in Example 1. Therefore, in Examples 9 to 11, while the design conditions for the positive electrode 21 were the same as in Example 1, the lengths of the positive electrode 21 and the negative electrode 22 in the L-axis direction were adjusted respectively so as to maintain the outer diameter of the electrode wound body 20 under the same conditions as in Example 1. Specifically, in Example 9 where the weight ratio of SiO was 16%, the length of the positive electrode 21 in the L-axis direction was changed to 1915 mm, and the length of the negative electrode 22 in the L-axis direction was changed to 1975 mm. In Example 10 where the weight ratio of SiO was 3%, the length of the positive electrode 21 in the L-axis direction was changed to 1600 mm, and the length of the negative electrode 22 in the L-axis direction was changed to 1660 mm. Further, in Example 11 where the weight ratio of SiO was 2%, the length of the positive electrode 21 in the L-axis direction was changed to 1560 mm, and the length of the negative electrode 22 in the L-axis direction was changed to 1620 mm.

[0119] (Comparative Example 1) A secondary battery was fabricated in the same manner as in Example 1, except that the width W-LAP of the overlapping portion LAP was set to 0, and the same evaluations as in Example 1 were performed. The results are shown together in Table 1.

[0120] (Comparative Example 2) A secondary battery was fabricated in the same manner as in Example 1, except that an outer can without a thick portion, that is, an outer can with a constant wall thickness of the side wall portion was used, and the same evaluations as in Example 1 were performed. The results are shown together in Table 1.

[0121] [Discussion] As shown in Table 1, it was found that in Examples 1 to 11, lithium deposition on the surface of the negative electrode 22 could be suppressed. Also, in Examples 1 to 6 and 8 to 11, no uncharged portion was confirmed in the negative electrode 22. On the other hand, for example, in Comparative Examples 1 and 2, both lithium deposition and an uncharged portion were confirmed. It was confirmed that the occurrence of lithium deposition and the uncharged portion in Comparative Examples 1 and 2 was due to the widened distance between the outermost peripheral portion 21out of the positive electrode and the outermost peripheral portion 22out of the negative electrode. In contrast, in Examples 1 to 11, it is considered that the distance between the outermost peripheral portion 21out of the positive electrode and the outermost peripheral portion 22out of the negative electrode was appropriately maintained due to the presence of the overlapping portion LAP, thereby preventing lithium deposition on the surface of the negative electrode 22. Lithium metal is known to have very high reactivity and low thermal stability. If lithium metal had been deposited on the negative electrode 22, there would have been concern about a decrease in the safety of the secondary battery. However, in Examples 1 to 11, since lithium deposition on the surface of the negative electrode 22 was suppressed, it was found that high safety of the secondary battery was obtained. Also, from the comparison between Examples 1 to 8 and Comparative Examples 1 and 2, it was confirmed that if the energy density of the negative electrode active material was the same and the length of the negative electrode in the L-axis direction was also the same, substantially the same initial capacity could be obtained.

[0122] In Example 7, although no lithium deposition on the surface of the negative electrode 22 was observed, a slight uncharged portion was confirmed. This is considered to be because since T2 / T1 was as small as 105%, the force to maintain the distance between the outermost peripheral portion 21out of the positive electrode and the outermost peripheral portion 22out of the negative electrode was weaker compared to other examples.

[0123] From the results of Examples 1 to 11, it was found that the thickness T2 of the thick portion 11S2 is preferably 110% or more and 180% or less of the thickness T1 of the thin portion 11S1. Specifically, from the comparison between Example 7 and Examples 1 to 6 and 8, by setting T2 / T1 to 110% or more, the spread between the outermost peripheral portion 21out of the positive electrode and the outermost peripheral portion 22out of the negative electrode can be sufficiently suppressed, and it was found that lithium deposition on the surface of the negative electrode 22 can be more effectively eliminated. Further, from the comparison between Example 8 and Examples 1 to 7, it was found that good cycle characteristics can be obtained by setting T2 / T1 to 180% or less. It is considered that good cycle characteristics are obtained because the positive electrode 21 and the negative electrode 22 are biased with an appropriate force by the thick portion 11S2, so that the electrolyte sufficiently penetrates the negative electrode active material, ensuring good ionic conductivity.

[0124] Also, from the comparison between Example 5 and Example 8, it was found that when T2 / T1 exceeds 180%, electrode breakage occurs. This is considered to be because the inner diameter IR2 of the thick portion 11S2 becomes too small, so that the force applied to the positive electrode 21 and the negative electrode 22 increases when charging and discharging are repeated.

[0125] Also, from the comparison between Example 6 and Examples 1 to 5, the overlap partial LAP By setting the width W-LAP to 0.5 mm or more and 5.0 mm or less, that is, by setting W-LAP / W-21B to 0.8% or more and 8.5% or less, it was found that good cycle characteristics can be obtained.

[0126] Furthermore, from the comparison between Examples 1, 9 to 11, it was confirmed that when the ratio of the weight of SiO to the total weight of graphite and SiO in the negative electrode active material is 3% by weight or more and 15% by weight or less, sufficient initial capacity and good cycle characteristics can be achieved without electrode breakage.

[0127] Incidentally, as another method for suppressing the widening of the distance between the outermost peripheral portion 21out of the positive electrode and the outermost peripheral portion 22out of the negative electrode, for example, a method is conceivable in which the length of the separator 23 on the outermost peripheral side of the electrode winding body 20 is extended, and the extended portion of the separator 23 is wound around the outermost peripheral surface of the electrode winding body 20 a plurality of times. Alternatively, a method is also conceivable in which the width of the fixing tape 46 on the outermost periphery of the electrode winding body 20 is increased and the length of the fixing tape 46 is extended, and the extended portion of the fixing tape 46 is wound around the outermost peripheral surface of the electrode winding body 20 a plurality of times. However, in such a case, while extending the length of the separator 23 or the length of the fixing tape 46, it is necessary to maintain the outer diameter of the electrode winding body 20 under the same conditions as in Example 1 by adjusting the lengths of the positive electrode 21 and the negative electrode 22 in the L-axis direction, respectively. As a result, the initial capacity will decrease compared to Example 1. Further, to the extent that the extended portion of the separator 23 or the extended portion of the fixing tape 46 is wound around the outermost peripheral surface of the electrode winding body 20 a plurality of times, it is considered that the widening of the distance between the outermost peripheral portion 21out of the positive electrode and the outermost peripheral portion 22out of the negative electrode due to the expansion and contraction of the negative electrode 22 accompanying charge and discharge cannot be sufficiently suppressed, and an uncharged portion will occur.

[0128] As described above, the present technology has been described with reference to one embodiment and examples. However, the configuration of the present technology is not limited to the configuration described in one embodiment and examples, and can be variously modified.

[0129] Specifically, in the above-described one embodiment and examples, the case where the electrode reactant is lithium has been described. However, the electrode reactant is not particularly limited. For this reason, the electrode reactant may be another alkali metal such as sodium and potassium, or an alkaline earth metal such as beryllium, magnesium, and calcium, as described above. In addition, the electrode reactant may be another light metal such as aluminum.

[0130] The effects described in this specification are merely examples, and the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present technology.

Claims

1. An electrode wound body in which a laminated structure in which a first electrode and a second electrode are laminated via a separator is wound around a central axis extending in a first direction, A first electrode current collector plate disposed so as to face a first end face in the first direction of the electrode wound body, A second electrode current collector plate disposed so as to face a second end face opposite to the first end face in the first direction of the electrode wound body, An electrolytic solution, A battery can having a bottom portion facing the second end face via the second electrode current collector plate and a side wall portion standing on the bottom portion so as to surround the electrode wound body, and accommodating the electrode wound body, the first electrode current collector plate, the second electrode current collector plate, and the electrolytic solution provided with, The first electrode has a first electrode covering portion in which a first electrode active material layer is coated on a first electrode current collector, and a first electrode exposed portion in which the first electrode current collector is exposed without being covered by the first electrode active material layer and is joined to the first electrode current collector plate, The second electrode has a second electrode covering portion in which a second electrode active material layer is coated on a second electrode current collector, and a second electrode exposed portion in which the second electrode current collector is exposed without being covered by the second electrode active material layer and is joined to the second electrode current collector plate, In the electrode wound body, the outermost peripheral portion of the second electrode is located outside the outermost peripheral portion of the first electrode, The side wall portion of the battery can includes a thin portion and a thick portion protruding inward of the battery can along the radial direction of the electrode wound body orthogonal to the first direction, The thick portion is at a position overlapping in the radial direction with an end portion on the first end face side in the first direction of the first electrode covering portion A secondary battery.

2. The first electrode is a positive electrode and the second electrode is a negative electrode The secondary battery according to claim 1.

3. The thickness of the thick portion in the radial direction is thicker than the thickness of the thin portion in the radial direction The secondary battery according to claim 1 or claim 2.

4. The thickness in the radial direction of the thick portion is 110% or more and 180% or less of the thickness in the radial direction of the thin portion. The secondary battery according to claim 3.

5. The inner diameter of the thin portion is 100.19% or more and 100.87% or less of the inner diameter of the thick portion. The secondary battery according to claim 1 or claim 2.

6. The length in the first direction of the overlapping portion between the thick portion and the first electrode coating portion is 0.5 mm or more and 5.0 mm or less. The secondary battery according to claim 1 or claim 2.

7. The ratio of the length in the first direction of the overlapping portion between the thick portion and the first electrode coating portion to the length in the first direction of the first electrode coating portion is 0.8% or more and 8.5% or less. The secondary battery according to claim 1 or claim 2.

8. The second electrode is a negative electrode and the second electrode active material layer is a negative electrode active material layer. The negative electrode active material layer contains graphite and SiO as negative electrode active materials. The secondary battery according to claim 1 or claim 2.

9. In the negative electrode active material, the ratio of the weight of SiO to the total weight of graphite and SiO is 3% by weight or more and 15% by weight or less. The secondary battery according to claim 8.

10. The first electrode is a positive electrode, the first electrode current collector is a positive electrode current collector, the first electrode active material layer is a positive electrode active material layer, the first electrode current collecting plate is a positive electrode current collecting plate, the first electrode coating portion is a positive electrode coating portion, and the first electrode exposed portion is a positive electrode exposed portion. The second electrode is a negative electrode, the second electrode current collector is a negative electrode current collector, the second electrode active material layer is a negative electrode active material layer, the second electrode current collecting plate is a negative electrode current collecting plate, the second electrode coating portion is a negative electrode coating portion, and the second electrode exposed portion is a negative electrode exposed portion. The secondary battery according to claim 1 or claim 2.

11. In the positive electrode, in the winding direction of the electrode winding body, the positive electrode active material layer covers the positive electrode current collector from the outer peripheral side edge of the positive electrode to the inner peripheral side edge of the positive electrode. The secondary battery according to claim 10.

12. The separator includes a porous film containing a polyolefin as a base material. The thickness of the porous film is 10 μm or more and 15 μm or less. The areal density of the porous film is 6.3 g / m ２ or more and 8.3 g / m ２ or less. The secondary battery according to claim 1 or claim 2.

13. Among the first electrode exposed portions wound around the central axis, a plurality of first edges adjacent to each other in the radial direction of the electrode winding body are bent toward the central axis so as to overlap each other. The secondary battery according to claim 1 or claim 2.

14. Among the second electrode exposed portions wound around the central axis, a plurality of second edges adjacent to each other in the radial direction of the electrode winding body are bent toward the central axis so as to overlap each other. The secondary battery according to claim 1 or claim 2.

15. The first electrode active material layer includes a positive electrode active material containing at least one of lithium cobaltate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. The secondary battery according to claim 1 or claim 2.

16. The secondary battery according to claim 1 or claim 2, a control unit for controlling the secondary battery, and an exterior body enclosing the secondary battery to form a battery pack.

17. The secondary battery according to claim 1 or claim 2, a conversion unit that converts the power supplied from the secondary battery into driving force, a driving unit that is driven according to the driving force, and a control unit that controls the operation of the secondary battery to form an electric vehicle.

18. The battery pack according to claim 16, a plurality of rotary wings, a motor that rotates each of the rotary wings, a support shaft that supports the rotary wings and the motor respectively, a motor control unit that controls the rotation of the motor, and a power supply line that supplies power to the motor, wherein the battery pack is connected to the power supply line to form an electric aircraft.

19. The secondary battery according to claim 1 or claim 2, and a movable part supplied with power from the secondary battery to form an electric tool.

20. An electronic device comprising the secondary battery according to claim 1 or claim 2 as a power supply source.

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