Secondary batteries, battery packs, electronic devices, power tools, electric aircraft, and electric vehicles

Abstract

This secondary battery comprises an electrode winding body, a first electrode current collector, a second electrode current collector, an electrolyte, and a battery container. The first electrode current collector faces a first end surface of the electrode winding body, and the second electrode current collector faces a second end surface of the electrode winding body. The electrode winding body has a portion where second electrodes face one another, the outermost portion of a second electrode and the inner periphery portion of the second electrode positioned inside the outermost portion of the second electrode facing each other without a first electrode being interposed therebetween. The second electrode current collector has a notched portion in a part of the circumference direction surrounding the central axis. The notched portion overlaps, in a first direction, at least a part of the portion where second electrodes face one another.

Description

[Technical Field]

[0001] The present disclosure relates to a secondary battery, a battery pack including the secondary battery, an electronic device, a power tool, an electric aircraft, and an electric vehicle. [Background technology]

[0002] Due to the widespread use of various electronic devices such as mobile phones, secondary batteries have been developed as power sources that are small, lightweight, and capable of achieving high energy density. These secondary batteries include a positive electrode, a negative electrode, and an electrolyte housed inside an exterior member, and various studies have been conducted on the configuration of these secondary batteries (see, for example, Patent Document 1).

[0003] Patent Document 1 proposes a secondary battery that employs a so-called tabless structure to reduce internal resistance and enable charging and discharging at a relatively large current. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2021 / 020237 Summary of the Invention

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

[0006] Therefore, there is a demand for secondary batteries with higher reliability.

[0007] A secondary battery according to an embodiment of the present disclosure includes an electrode winding, a first electrode current collector, a second electrode current collector, an electrolyte, and a battery can. The electrode winding is formed by winding a laminate structure in which a first electrode and a second electrode are stacked with a separator interposed therebetween around a central axis extending in a first direction. The first electrode current collector is disposed so as to face a first end face of the electrode winding in the first direction. The second electrode current collector is disposed so as to face a second end face of the electrode winding opposite the first end face in the first direction. The battery can accommodates the electrode winding, the first electrode current collector, the second electrode current collector, and the electrolyte. The first electrode has a first electrode covering portion in which the first electrode current collector is covered with a first electrode active material layer, and a first electrode exposed portion in which the first electrode current collector is exposed and not covered by the first electrode active material layer and joined to the first electrode current collector. The second electrode has a second electrode covered portion in which the second electrode current collector is covered with a second electrode active material layer, and a second electrode exposed portion in which the second electrode current collector is exposed and not covered with the second electrode active material layer and joined to the second electrode current collector. The electrode winding has an opposing portion of the second electrodes in which the outermost peripheral portion of the second electrode and an inner peripheral portion of the second electrode located inside the outermost peripheral portion of the second electrode face each other without the first electrode interposed therebetween. The second electrode current collector has a notched portion in a part of the circumferential direction surrounding the central axis. The notched portion overlaps in a first direction with at least a part of the opposing portion of the second electrodes.

[0008] In a secondary battery according to an embodiment of the present disclosure, the notched portion of the second electrode current collector overlaps in the first direction with at least a portion of the opposing portion of the second electrodes. That is, most of the opposing portion between the outermost peripheral portion of the first electrode and the outermost peripheral portion of the second electrode in the electrode winding overlaps in the first direction with a portion of the second electrode current collector. Therefore, the opposing portion between the outermost peripheral portion of the first electrode and the outermost peripheral portion of the second electrode is protected by the second electrode current collector. Therefore, even if an impact is applied to the electrode winding due to a drop or the like, an internal short circuit between the outermost peripheral portion of the first electrode and the outermost peripheral portion of the second electrode can be avoided. This results in higher reliability.

[0009] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view illustrating a configuration of a secondary battery according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing an example of a laminate structure including the positive electrode, negative electrode, and separator shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view showing an example of the cross-sectional structure of the electrode winding body shown in FIG. [Figure 4A] FIG. 4A is a development view of the positive electrode shown in FIG. [Figure 4B] FIG. 4B is a cross-sectional view of the positive electrode shown in FIG. [Figure 5A] FIG. 5A is a development view of the negative electrode shown in FIG. [Figure 5B] FIG. 5B is a cross-sectional view of the negative electrode shown in FIG. [Figure 6A] FIG. 6A is a plan view of the positive electrode current collector plate shown in FIG. [Figure 6B] FIG. 6B is a plan view of the negative electrode current collector plate shown in FIG. [Figure 6C] FIG. 6C is an explanatory diagram illustrating a cutout portion of the negative electrode current collector plate shown in FIG. 6B. [Figure 7] FIG. 7 is a perspective view illustrating a manufacturing process of the secondary battery shown in FIG. [Figure 8] FIG. 8 is a block diagram showing a circuit configuration of a battery pack to which the secondary battery according to an embodiment of the present disclosure is applied. [Figure 9] FIG. 9 is a schematic diagram illustrating the configuration of a power tool to which the secondary battery according to an embodiment of the present disclosure can be applied. [Figure 10] FIG. 10 is a schematic diagram illustrating the configuration of an unmanned aerial vehicle to which a secondary battery according to an embodiment of the present disclosure can be applied. [Figure 11]FIG. 11 is a schematic diagram illustrating the configuration of a power storage system for an electrically powered vehicle to which a secondary battery according to an embodiment of the present disclosure is applied. [Figure 12] FIG. 12 is a cross-sectional view showing one example of the cross-sectional structure of the electrode winding body of Comparative Example 1-1. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The description will be made in the following order. 1. Secondary battery 1-1.Configuration 1-2.Operation 1-3. Manufacturing method 1-4. Action and effects 2. Application Examples

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

[0013] In this embodiment, a cylindrical lithium-ion secondary battery having a cylindrical external shape will be described as an example. 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 external shape other than a cylindrical shape, or may be a battery using an electrode reactant other than lithium.

[0014] The charge / discharge principle of a secondary battery is not particularly limited, but the following description focuses on a case where battery capacity is obtained by utilizing the absorption / desorption of an electrode reactant. This secondary battery includes a positive electrode, a negative electrode, and an electrolyte. In this secondary battery, the charge capacity of the negative electrode is larger than the discharge capacity of the positive electrode to prevent deposition of the electrode reactant on the surface of the negative electrode during charging. In other words, 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 electrode reactant is not particularly limited as described above, but specifically includes light metals such as alkali metals and alkaline earth metals. Alkali metals include lithium, sodium, and potassium, and alkaline earth metals include beryllium, magnesium, and calcium.

[0016] In the following, we will take the case where the electrode reactant is lithium as an example. A secondary battery that obtains battery capacity by utilizing the absorption and desorption of lithium is called a lithium ion secondary battery. In this lithium ion secondary battery, lithium is absorbed and desorbed in the ionic state.

[0017] [1-1.Configuration] (Lithium-ion secondary battery 1) 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, a cylindrical outer can 11 houses an electrode winding body 20 as a battery element.

[0018] Specifically, the secondary battery 1 includes, for example, a pair of insulating plates 12, 13 and an electrode winding body 20 inside an outer can 11. The electrode winding body 20 is a structure in which, for example, a positive electrode 21 and a negative electrode 22 are stacked and wound with a separator 23 interposed therebetween. The electrode winding body 20 is impregnated with an electrolytic solution, which is a liquid electrolyte. The secondary battery 1 may further include, inside the outer can 11, one or more of a thermosensitive resistor (PTC) element and a reinforcing member.

[0019] (Outer can 11) The outer can 11 has, for example, a hollow cylindrical structure with a closed lower end in the Z-axis direction (height direction) and an open upper end. Therefore, the upper end of the outer can 11 is an open end 11N. The outer can 11 is made of a material containing, for example, a metal material such as iron. However, the surface of the outer can 11 may be plated with a metal material such as nickel. The insulating plates 12 and 13 are disposed, for example, facing each other in the Z-axis direction with the electrode winding body 20 sandwiched between them. In this specification, the open end 11N and its vicinity in the Z-axis direction may be referred to as the upper part of the secondary battery 1, and the closed portion of the outer can 11 and its vicinity may be referred to as the lower part of the secondary battery 1.

[0020] (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, i.e., a surface perpendicular to the Z axis in Fig. 1. The insulating plates 12 and 13 are arranged so as to sandwich the electrode winding body 20 therebetween.

[0021] (Crimped 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 a gasket 15, i.e., a crimped structure 11R, is formed. The outer can 11 is sealed by the battery lid 14 with the electrode wound body 20 and the like housed inside the outer can 11. The crimped structure 11R is a so-called crimped structure and has a bent portion 11P as a so-called crimp portion.

[0022] (Battery cover 14) The battery lid 14 is mainly a closing member that closes the open end 11N when the electrode winding body 20 and the like are housed inside the exterior can 11. The battery lid 14 contains, for example, the same material as the material from which the exterior can 11 is formed. For example, the central region of the battery lid 14 protrudes upward (in the +Z direction). As a result, the peripheral region of the battery lid 14 other than the central region is in contact with, for example, the safety valve mechanism 30.

[0023] (Gasket 15) The gasket 15 is a sealing member interposed mainly between the folded portion 11P of the outer can 11 and the battery lid 14. The gasket 15 seals the gap between the folded portion 11P and the battery lid 14. However, the surface of the gasket 15 may be coated with, for example, asphalt. The gasket 15 contains, for example, one or more types of insulating materials. The type of insulating material is not particularly limited, but examples include polymer materials such as polybutylene terephthalate (PBT) and polypropylene (PP). Among these, polybutylene terephthalate is preferable as the insulating material. This is because the gap between the folded portion 11P and the battery lid 14 is sufficiently sealed while electrically isolating the outer can 11 and the battery lid 14 from each other.

[0024] (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 pressure inside the outer can 11 (internal pressure) increases. The internal pressure of the outer can 11 increases, for example, due to gas generated by a decomposition reaction of the electrolyte during charging and discharging. The internal pressure of the outer can 11 may also increase due to external heating.

[0025] (Electrode winding body 20) The electrode winding body 20 is a power generating element that promotes charge / discharge reactions, 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 electrolytic solution that is a liquid electrolyte.

[0026] FIG. 2 is a developed view of the electrode winding body 20, and schematically illustrates a portion of a laminate structure S20 including a positive electrode 21, a negative electrode 22, and a separator 23. In the electrode winding body 20, the positive electrode 21 and the negative electrode 22 are laminated with the separator 23 interposed therebetween. The separator 23 has, for example, two base materials, namely, a first separator member 23A and a second separator member 23B. Therefore, the electrode winding body 20 has a four-layer laminate 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 with the W-axis direction as the short side direction and the L-axis direction as the long side direction. As shown in FIG. 3, the electrode winding body 20 is formed by winding the laminate structure S20 around a central axis CL (see FIG. 1) extending in the Z-axis direction so as to form a spiral shape in a horizontal cross section perpendicular to the Z-axis direction. The laminate structure S20 is wound in such a manner that the W-axis direction roughly coincides with the Z-axis direction. Note that FIG. 3 shows an example of the configuration of the electrode winding body 20 along a horizontal cross section perpendicular to the Z-axis direction. However, in FIG. 3, the separator 23 is omitted from illustration to ensure 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 in which they face each other with the separator 23 interposed therebetween. A through-hole 26 is formed at the center of the electrode winding body 20 as an internal space. The through-hole 26 is a hole for inserting a winding core for assembling the electrode winding body 20 and an electrode rod for welding.

[0027] The positive electrode 21, the negative electrode 22, and the separator 23 are wound such that the separator 23 is disposed at the outermost and innermost peripheries of the electrode winding body 20. 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. 3 , the positive electrode outermost periphery portion 21out, which is located at the outermost periphery of the positive electrode 21 included in the electrode winding body 20, is disposed inside the negative electrode outermost periphery portion 22out, which is located at the outermost periphery of the negative electrode 22 included in the electrode winding body 20. Here, the positive electrode outermost periphery portion 21out refers to the outermost portion of the positive electrode 21 in the electrode winding body 20, which corresponds to one circumference. The negative electrode outermost periphery portion 22out refers to the outermost portion of the negative electrode 22 in the electrode winding body 20, which corresponds to one circumference. Meanwhile, it is preferable that the negative electrode 22 is disposed inside the positive electrode 21 in the innermost periphery of the electrode winding body 20. That is, the negative electrode innermost circumferential portion located at the innermost periphery of the negative electrode 22 included in the electrode winding body 20 may be located more inward than the positive electrode innermost circumferential portion located at the innermost periphery of the positive electrode 21 included in the electrode winding body 20. Here, the positive electrode innermost circumferential portion refers to the innermost one-circumferential portion of the positive electrode 21 in the electrode winding body 20. The negative electrode innermost circumferential portion refers to the innermost one-circumferential portion of the negative electrode 22 in the electrode winding body 20. The number of windings of each of the positive electrode 21, negative electrode 22, and separator 23 is not particularly limited and can be set as desired.

[0028] FIG. 4A is a developed view of the positive electrode 21, and schematically illustrates the state before winding. FIG. 4B illustrates a cross-sectional configuration of the positive electrode 21. Note that FIG. 4B illustrates a cross section taken along line IVB-IVB in FIG. 4A as viewed from the arrow direction. The positive electrode 21 includes, for example, a positive electrode current collector 21A and a positive electrode active material layer 21B provided on the positive electrode current collector 21A. The positive electrode active material layer 21B may be provided on only one side of the positive electrode current collector 21A, or on both sides of the positive electrode current collector 21A. FIG. 4B illustrates a case in which the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A.

[0029] The positive electrode 21 has a positive electrode covering portion 211 in which a positive electrode active material layer 21B is covering a 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. 4A , the positive electrode covering portion 211 and the positive electrode exposed portion 212 each extend along the L-axis direction, which is the longitudinal direction, from the outer peripheral edge 21E1 to the inner peripheral edge 21E2 of the electrode wound body 20. Here, the L-axis direction corresponds to the winding direction of the electrode wound body 20. That is, in the positive electrode 21, the positive electrode active material layer 21B covers the positive electrode current collector 21A from the outer peripheral edge 21E1 of the positive electrode 21 to the inner peripheral edge 21E2 of the positive electrode 21 in the winding direction of the electrode wound body 20. The positive electrode covering portion 211 and the positive electrode exposed portion 212 are adjacent to each other in the W-axis direction, which is the short side direction. The positive electrode exposed portion 212 is connected to the positive electrode current collector 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. Similar to the positive electrode covering portion 211 and the positive electrode exposed portion 212, the insulating layer 101 may extend from the innermost end to the outermost end of the electrode wound body 20. The insulating layer 101 may be bonded to at least one of the first separator member 23A and the second separator member 23B. This is because misalignment between the positive electrode 21 and the separator 23 can be prevented. The insulating layer 101 may contain a resin containing polyvinylidene fluoride (PVDF). This is because, when insulating layer 101 contains PVDF, insulating layer 101 swells due to, for example, a solvent contained in the electrolyte solution, and can be well bonded to separator 23. The detailed configuration of positive electrode 21 will be described later.

[0030] FIG. 5A is a developed view of the negative electrode 22, and schematically illustrates the state before winding. FIG. 5B illustrates a cross-sectional configuration of the negative electrode 22. Note that FIG. 5B illustrates a cross section taken along line VB-VB in FIG. 5A. The negative electrode 22 includes, for example, a negative electrode current collector 22A and a negative electrode active material layer 22B provided on the negative electrode current collector 22A. The negative electrode active material layer 22B may be provided on only one side of the negative electrode current collector 22A, or on both sides of the negative electrode current collector 22A. FIG. 5B illustrates a case where the negative electrode active material layer 22B is provided on both sides of the negative electrode current collector 22A.

[0031] The negative electrode 22 has a negative electrode covering portion 221 in which the negative electrode current collector 22A is covered with the negative electrode active material layer 22B, and a negative electrode exposed portion 222 in which the negative electrode current collector 22A is exposed without being covered with the negative electrode active material layer 22B. As shown in FIG. 5A , the negative electrode covering portion 221 and the negative electrode exposed portion 222 each extend along the L-axis direction, which is the longitudinal direction. The negative electrode exposed portion 222 extends from the innermost circumferential end to the outermost circumferential end of the electrode wound body 20. In contrast, the negative electrode covering portion 221 is not provided at the innermost circumferential end or the outermost circumferential end of the electrode wound body 20. As shown in FIG. 5A , parts of the negative electrode exposed portion 222 are formed 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 cover 221 in the W-axis direction and extends in the L-axis direction from the innermost end to the outermost end of the electrode winding 20. The second portion 222B and the third portion 222C are provided so as to sandwich the negative electrode cover 221 in the L-axis direction. The second portion 222B is located, for example, near the innermost end of the electrode winding 20, and the third portion 222C is located near the outermost end of the electrode winding 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.

[0032] In the secondary battery 1, the stack structure S21 of the electrode wound body 20 is formed by stacking the positive electrode 21 and the negative electrode 22 with the separator 23 interposed between them so that the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 face opposite each other along the W-axis direction, which is the width direction. The electrode wound body 20 has the end of the separator 23 fixed by attaching a fixing tape 46 to a side surface portion 45 thereof, thereby preventing loosening of the winding.

[0033] In the secondary battery 1, as shown in FIG. 2 , 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). Furthermore, when the width of the portion of the positive electrode exposed portion 212 that protrudes from the outer edge of the separator 23 in the width direction is C and the length of the first portion 222A of the negative electrode exposed portion 222 that protrudes from the outer edge on the opposite side in the width direction of the separator 23 is D, it is preferable that C>D. For example, when the width C=4.5 (mm), the width D=3 (mm).

[0034] As shown in FIG. 1 , at the upper part of the secondary battery 1, of the positive electrode exposed portion 212 wound around the central axis CL, multiple first edges 212E adjacent in the radial direction (R direction) of the electrode winding body 20 are bent toward the central axis CL so as to overlap with each other. Similarly, at the lower part of the secondary battery 1, of the negative electrode exposed portion 222 wound around the central axis CL, multiple second edges 222E adjacent in the radial direction (R direction) are bent toward the central axis CL so as to overlap with each other. Therefore, the multiple first edges 212E of the positive electrode exposed portion 212 are gathered at the end surface 41 of the upper part of the electrode winding body 20, and the multiple second edges 222E of the negative electrode exposed portion 222 are gathered at the end surface 42 of the lower part of the electrode winding body 20. To improve contact between the positive electrode current collector plate 24 and the first edges 212E for extracting current, the multiple first edges 212E bent toward the central axis CL are flat. Similarly, in order to improve contact between the negative electrode current collector plate 25 and the second edge portion 222E for extracting current, the plurality of second edge portions 222E bent toward the central axis CL are flat. Note that the flat surface here does not only mean a completely flat surface, but also means a surface having some unevenness or surface roughness to the extent that the positive electrode exposed portion 212 and the negative electrode exposed portion 222 can be joined to the positive electrode current collector plate 24 and the negative electrode current collector plate 25, respectively. This also includes surfaces having

[0035] The positive electrode current collector 21A is made of, for example, aluminum foil, as described below. On the other hand, the negative electrode current collector 22A is made of, for example, copper foil, as described below. 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. Therefore, in one embodiment, A>B and C>D are more preferable. In this case, when the positive electrode exposed portion 212 and the negative electrode exposed portion 222 are folded simultaneously from both electrode sides with the same pressure, the heights of the folded portions measured from the tip of the separator 23 on the positive electrode 21 and the negative electrode 22 may be approximately the same. At this time, the multiple first edge portions 212E (FIG. 1) of the positive electrode exposed portion 212 are folded and overlap each other appropriately. This facilitates joining of the positive electrode exposed portion 212 and the positive electrode current collector 24. Similarly, the multiple second edge portions 222E (FIG. 1) of the negative electrode exposed portion 222 are folded and overlap each other to an appropriate degree. This facilitates joining of the negative electrode exposed portion 222 and the negative electrode current collector plate 25. The joining here means joining by, for example, laser welding, but the joining method is not limited to laser welding.

[0036] As shown in FIG. 2 , the portion of the positive electrode exposed portion 212 of the positive electrode 21 that faces the negative electrode 22 across the separator 23 is covered with an insulating layer 101. The insulating layer 101 has a width of, for example, 3 mm in the W-axis direction. The insulating layer 101 covers the entire region of the positive electrode exposed portion 212 of the positive electrode 21 that faces the negative electrode covering portion 221 of the negative electrode 22 with the separator 23 interposed therebetween. The insulating layer 101 can effectively prevent an internal short circuit in the secondary battery 1, for example, when a foreign object enters between the negative electrode covering portion 221 and the positive electrode exposed portion 212. Furthermore, when an impact is applied to the secondary battery 1, the insulating layer 101 absorbs the impact and can effectively prevent bending of the positive electrode exposed portion 212 and a short circuit between the positive electrode exposed portion 212 and the negative electrode 22.

[0037] (Insulating tape 53, 54) The secondary battery 1 may further include insulating tapes 53, 54 in the gap between the outer can 11 and the electrode winding body 20. The positive electrode exposed portion 212 and the negative electrode exposed portion 222, which are gathered on the end faces 41, 42, are conductors such as bare metal foil. Therefore, if the positive electrode exposed portion 212 and the negative electrode exposed portion 222 are close to the outer can 11, a short circuit may occur between the positive electrode 21 and the negative electrode 22 through the outer can 11. Furthermore, if the positive electrode current collector plate 24 on the end face 41 comes close to the outer can 11, a short circuit may also occur. For this reason, it is preferable to provide insulating tapes 53, 54 as insulating members. The insulating tapes 53, 54 are, for example, adhesive tapes whose base layer is made of polypropylene, polyethylene terephthalate, or polyimide and whose base layer has an adhesive layer on one surface. In order to prevent the installation of the insulating tapes 53, 54 from reducing the volume of the electrode winding body 20, the insulating tapes 53, 54 are positioned so as not to overlap with the fixing tape 46 attached to the side portion 45, and the thickness of the insulating tapes 53, 54 is set to be equal to or less than the thickness of the fixing tape 46.

[0038] (Positive electrode current collector 24 and negative electrode current collector 25) In a typical lithium-ion secondary battery, for example, a lead for current extraction is welded to each of the positive and negative electrodes. However, this increases the internal resistance of the lithium-ion secondary battery and causes the lithium-ion secondary battery to heat up and reach high temperatures during discharge, making it unsuitable for high-rate discharge. Therefore, in the secondary battery 1 of this embodiment, the positive current collector 24 is positioned opposite the end face 41, and the negative current collector 25 is positioned opposite the end face 42. The positive electrode exposed portion 212 at the end face 41 is welded to the positive electrode current collector 24 at multiple points, and the negative electrode exposed portion 222 at the end face 42 is welded to the negative electrode current collector 25 at multiple points. This reduces the internal resistance of the secondary battery 1. The flat surfaces of the end faces 41 and 42, as described above, also contribute to the low resistance. The positive electrode current collector 24 is electrically connected to the battery cover 14, for example, via a safety valve mechanism 30. The negative electrode current collector 25 is electrically connected to the outer can 11, for example. Fig. 6A is a schematic diagram showing an example of the configuration of the positive electrode current collector 24. Fig. 6B is a schematic diagram showing an example of the configuration of the negative electrode current collector 25. The positive electrode current collector 24 is a metal plate made of, for example, aluminum or an aluminum alloy, or a composite material thereof. The negative electrode current collector 25 is a metal plate made of, for example, nickel, a nickel alloy, copper, or a copper alloy, or a composite material of two or more of these.

[0039] As shown in FIG. 6A , the positive electrode current collector 24 has a shape in which a substantially rectangular strip-shaped portion 32 is connected to a substantially sector-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 the through-hole 26 in the Z-axis direction. The hatched portion in FIG. 6A is an insulating portion 32A of the strip-shaped portion 32. The insulating portion 32A is a portion of the strip-shaped portion 32 to which insulating tape is attached or an insulating material is applied. The portion of the strip-shaped portion 32 below the insulating portion 32A is a connecting portion 32B to the sealing plate, which also serves as an external terminal. Note that, as shown in FIG. 1 , if the secondary battery 1 has a battery structure in which the through-hole 26 does not have a metal center pin, the strip-shaped portion 32 is unlikely to come into contact with a portion of the negative electrode potential. Therefore, the positive electrode current collector 24 does not need to have the insulating portion 32A. When the positive electrode current collector 24 does not have the insulating portion 32A, the charge / discharge capacity can be increased by widening the width between the positive electrode 21 and the negative electrode 22 by an amount corresponding to the thickness of the insulating portion 32A.

[0040] The shape of the negative current collector plate 25 shown in FIG. 6B is almost the same as the shape of the positive current collector plate 24 shown in FIG. 6A. That is, it has a shape in which a substantially rectangular band-shaped portion 34 is connected to a substantially fan-shaped sector portion 33. As shown in FIG. 6C, the outer shape of the sector portion 33 of the negative current collector plate 25 is surrounded by a contour portion 33R that describes an approximately arc and a contour portion 33S that extends in a substantially straight line. That is, as shown in FIG. 6C, the outer shape of the sector portion 33 has a shape in which a portion of a substantially circular disk is missing. Here, the missing portion (arch-shaped portion) of the substantially circular disk indicated by the dashed line is the notch portion 25K. Furthermore, the band-shaped portion 34 of the negative current collector plate 25 is different from the band-shaped portion 32 of the positive current collector plate 24. The strip portion 34 of the negative current collector plate 25 is shorter than the strip portion 32 of the positive current collector plate 24, and does not have a portion corresponding to the insulating portion 32A of the positive current collector plate 24. The strip portion 34 has a round protrusion 37 indicated by a plurality of circles. During resistance welding, current concentrates on the protrusion 37, melting the protrusion 37 and welding the strip portion 34 to the bottom of the outer casing 11. Like the positive current collector plate 24, the negative current collector plate 25 has a through hole 36 formed near the center of the sector portion 33. In the secondary battery 1, the negative current collector plate 25 is provided so that the through hole 36 overlaps with the through hole 26 in the Z-axis direction.

[0041] Due to its planar shape, the sectorial portion 31 of the positive current collector plate 24 covers only a portion of the end face 41. Similarly, due to its planar shape, the sectorial portion 33 of the negative current collector plate 25 covers only a portion of the end face 42. There are two reasons why the sectorial portions 31 and 33 do not cover the entire end face 41 and the end face 42, respectively. First, this is to allow the electrolyte to smoothly penetrate into the electrode winding body 20 when assembling the secondary battery 1, for example. Second, this is to facilitate the release of gas generated when the lithium-ion secondary battery is subjected to an abnormally high temperature or is overcharged.

[0042] (Positive electrode current collector 21A) The positive electrode current collector 21A contains a conductive material such as aluminum, etc. The positive electrode current collector 21A is, for example, a metal foil made of aluminum or an aluminum alloy.

[0043] (Positive electrode active material layer 21B) The positive electrode active material layer 21B contains, as a positive electrode active material, one or more types of positive electrode materials capable of absorbing and releasing lithium. However, the positive electrode active material layer 21B may further contain one or more types of other materials, such as a positive electrode binder and a positive electrode conductor. The positive electrode material is preferably a lithium-containing compound, more specifically, a lithium-containing composite oxide or a lithium-containing phosphate compound. The lithium-containing composite oxide is an oxide containing lithium and one or more other elements, i.e., elements other than lithium, as constituent elements. The lithium-containing composite oxide has, for example, a layered rock salt type or a spinel type crystal structure. The lithium-containing phosphate compound is a phosphate compound containing lithium and one or more other elements as constituent elements, and has, for example, an olivine type crystal structure. The positive electrode active material layer 21B preferably contains, as a positive electrode active material, at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. The positive electrode binder contains, for example, one or more of synthetic rubber and polymer compounds. Examples of synthetic rubber include styrene-butadiene rubber, fluorine-based rubber, and ethylene propylene diene. Examples of polymer compounds include polyvinylidene fluoride and polyimide. The positive electrode conductive agent contains, for example, one or more of carbon materials. Examples of carbon materials include graphite, carbon black, acetylene black, and ketjen black. However, the positive electrode conductive agent may also be a metal material or a conductive polymer, as long as it is a conductive material.

[0044] The positive electrode active material layer 21B may also contain a fluorine compound and a nitrogen compound. In particular, a positive electrode coating containing a fluorine compound and a nitrogen compound may be formed on the surface of the positive electrode active material layer 21B. Furthermore, the weight ratio F / N of the fluorine content to the nitrogen content in the positive electrode coating of the positive electrode active material layer 21B may be 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 coating of the positive electrode active material layer 21B may be 15 or more and 35 or less. The weight ratio F / N of the fluorine content to the nitrogen content in the positive electrode coating of the positive electrode active material layer 21B may be calculated based on, for example, the spectral peak areas of the 1s orbital of nitrogen atoms and the 1s orbital of fluorine atoms measured by X-ray photoelectron spectroscopy.

[0045] In addition, the area density of the positive electrode active material layer 21B is 21.5 mg / cm 2 More than 23.5mg / cm 2 It is preferable that the thickness T2 of the positive electrode covering portion 211 to the thickness T1 of the positive electrode current collector 21A be equal to or less than 5.0 and equal to or less than 6.5. This is because the temperature rise of the secondary battery 1 during high-load rate charging can be suppressed. Furthermore, as shown in FIG. 3B, the ratio T2 / T1 of the thickness T2 of the positive electrode covering portion 211 to the thickness T1 of the positive electrode current collector 21A, i.e., the ratio of the total thickness T2 of the positive electrode current collector 21A and the positive electrode active material layer 21B, is equal to or greater than 5.0 and equal to or less than 6.5. Here, the thickness T2 of the positive electrode covering portion 211 of the positive electrode 21 is, for example, equal to or greater than 60 μm and equal to or less than 90 μm. Furthermore, the thickness T1 of the positive electrode current collector 21A is, for example, equal to or greater than 6 μm and equal to or less than 15 μm.

[0046] (Negative electrode current collector 22A) The negative electrode current collector 22A contains a conductive material such as copper. The negative electrode current collector 22A is a metal foil made of, for example, nickel, a nickel alloy, copper, or a copper alloy. The surface of the negative electrode current collector 22A is preferably roughened. This is because the so-called anchor effect improves the adhesion of the negative electrode active material layer 22B to the negative electrode current collector 22A. 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 roughening method may be, for example, a method of forming fine particles using an electrolytic process. In the electrolytic process, fine particles are formed on the surface of the negative electrode current collector 22A by electrolysis in an electrolytic bath, resulting in an uneven surface of the negative electrode current collector 22A. Copper foil produced by an electrolytic process is generally called electrolytic copper foil.

[0047] (Negative electrode active material layer 22B) The negative electrode active material layer 22B contains, as the negative electrode active material, one or more types of negative electrode materials capable of absorbing and releasing lithium. However, the negative electrode active material layer 22B may further contain one or more types of other materials, such as a negative electrode binder and a negative electrode conductor. The negative electrode material is, for example, a carbon material. This is because a high energy density can be stably obtained because the crystal structure changes very little during lithium absorption and release. In addition, the carbon material also functions as a negative electrode conductor, thereby improving the conductivity of the negative electrode active material layer 22B. Examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite. However, the interplanar spacing of the (002) plane of non-graphitizable carbon is preferably 0.37 nm or more. The interplanar spacing of the (002) plane of graphite is preferably 0.34 nm or less. More specifically, carbon materials include, for example, pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound calcined bodies, activated carbon, and carbon blacks. Examples of cokes include pitch coke, needle coke, and petroleum coke. Organic polymer compound calcined bodies are obtained by calcining (carbonizing) polymer compounds such as phenolic resins and furan resins at an appropriate temperature. Alternatively, the carbon material may be low-crystalline carbon heat-treated at temperatures below approximately 1000°C, or amorphous carbon. The carbon material may be fibrous, spherical, granular, or flake-shaped. In the secondary battery 1, when the open-circuit voltage at full charge, i.e., the battery voltage, is 4.25 V or higher, the amount of lithium released per unit mass is greater than 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 positive and negative electrode active materials are adjusted accordingly. This results in a high energy density.

[0048] Further, the negative electrode active material layer 22B may contain, as a negative electrode active material, a silicon-containing material containing at least one of silicon, silicon oxide, carbon-silicon compound, and silicon alloy. The silicon-containing material is a general term for materials containing silicon as a constituent element. However, the silicon-containing material may contain only silicon as a constituent element. Note that the type of the silicon-containing material may be only one type or two or more types. The silicon-containing material can form an alloy with lithium, and may be a simple substance of silicon, an alloy of silicon, a compound of silicon, a mixture of two or more of them, or a material containing one or two or more phases of them. 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 the series of constituent elements described for the alloy of silicon as a constituent element other than silicon. Specifically, the alloy of silicon and the compound of silicon are, for example, SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, and SiO v (0 < v ≤ 2) and the like. However, the range of v can be arbitrarily set, for example, 0.2 < v < 1.4 may also be possible.

[0049] (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 current short-circuiting due to contact between the positive electrode 21 and the negative electrode 22. The separator 23 is made of, for example, one or more types of porous membranes, such as synthetic resins and ceramics, or may be a laminated membrane of two or more types of porous membranes. Examples of synthetic resins include polytetrafluoroethylene, polypropylene, and polyethylene. However, the separator 23 preferably has a substrate made of a single-layer polyolefin porous membrane containing polyethylene. This is because better high-output characteristics can be obtained compared to laminated membranes. When the first separator member 23A and the second separator member constituting the separator 23 are each 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-circuiting can be sufficiently avoided. If the thickness of the single-layer porous film made of polyolefin is 15 μm or less, better discharge capacity characteristics can be obtained. In addition, the surface density of the porous film is, for example, 6.3 g / m 2 More than 8.3g / m 2 The surface density of the single-layer porous film made of polyolefin is preferably 6.3 g / m or less. 2 If the surface density of the single-layer porous film made of polyolefin is 8.3 g / m or more, internal short circuits can be sufficiently avoided. 2 If the content is less than this, better discharge capacity characteristics can be obtained.

[0050] In particular, the separator 23 may include, for example, the porous membrane as the substrate described above and a polymer compound layer provided on one or both sides of the substrate layer. This is because the separator 23 improves adhesion to each of the positive electrode 21 and the negative electrode 22, thereby suppressing distortion of the electrode winding body 20. This suppresses decomposition reactions of the electrolyte and also suppresses leakage of the electrolyte impregnated in the substrate layer, thereby making it difficult for resistance to increase even with repeated charge and discharge, and suppressing battery swelling. The polymer compound layer includes, for example, a polymer compound such as polyvinylidene fluoride. This is because it has excellent physical strength and is electrochemically stable. However, the polymer compound may be other than polyvinylidene fluoride. To form 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 substrate layer, and the substrate layer is then dried. Alternatively, the substrate layer may be immersed in the solution and then dried. The polymer compound layer may contain one or more types of insulating particles such as inorganic particles, for example, aluminum oxide and aluminum nitride.

[0051] (electrolyte) The electrolyte solution contains a solvent and an electrolyte salt. However, the electrolyte solution may further contain one or more other materials such as additives. The solvent contains one or more non-aqueous solvents such as organic solvents. An electrolyte solution containing a non-aqueous solvent is a so-called non-aqueous electrolyte solution. The non-aqueous solvent contains, for example, a fluorine compound and a dinitrile compound. The fluorine compound includes, for example, at least one of fluorinated ethylene carbonate, trifluorocarbonate, trifluoroethyl methyl carbonate, fluorinated carboxylic acid ester, and fluorinated ether. The non-aqueous solvent may further contain a nitrile compound other than the dinitrile compound, such as at least one of a mononitrile compound and a trinitrile compound. As the dinitrile compound, succinonitrile (SN) is preferable. However, the dinitrile compound is not limited to succinonitrile, and may be other dinitrile compounds such as adiponitrile.

[0052] The electrolyte salt includes, for example, one or more salts such as lithium salts. However, the electrolyte salt may include, for example, salts other than lithium salts. The salts other than lithium include, for example, salts of light metals other than lithium. Examples of lithium salts include lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), dilithium hexafluorosilicate (Li2SF6), lithium chloride (LiCl), and lithium bromide (LiBr). Among these, one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate are preferred, with lithium hexafluorophosphate being more preferred. The content of the electrolyte salt is not particularly limited, but is preferably 0.3 mol / kg to 3 mol / kg relative to the solvent. When the electrolyte solution contains LiPF6 as the electrolyte salt, the LiPF6 concentration in the electrolyte solution is preferably 1.25 mol / kg to 1.45 mol / kg. This is because cycle deterioration due to salt consumption (decomposition) during high-load rate charging can be prevented, thereby improving high-load cycle performance. When the electrolyte solution further contains LiBF4 in addition to LiPF6, the LiBF4 concentration in the electrolyte solution is preferably 0.001 (wt%) to 0.1 (wt%). This is because cycle deterioration due to salt consumption (decomposition) during high-load rate charging can be more effectively prevented, thereby further improving high-load cycle performance.

[0053] Next, a relationship between the electrode winding body 20 and the negative electrode current collector plate 25 along a horizontal plane perpendicular to the Z-axis direction will be described in detail with reference to Fig. 3. In Fig. 3, only the outline of the negative electrode current collector plate 25 is depicted by a solid line.

[0054] 3, the secondary battery 1 has an opposing portion FA1 between the outermost positive electrode portion 21out and the outermost negative electrode portion 22out in the electrode winding body 20, and an opposing portion FA2 between the negative electrodes 22. The opposing portion FA2 is a portion where the outermost negative electrode portion 22out of the negative electrode 22 faces the innermost negative electrode portion 22in of the negative electrode 22, which is located inside the outermost negative electrode portion 22out, without the positive electrode 21 interposed therebetween. In the secondary battery 1, the cutout portion 25K of the negative electrode current collector 25 overlaps with at least a portion of the opposing portion FA2 in the Z-axis direction. Therefore, most of the opposing portion FA1 between the outermost positive electrode portion 21out and the outermost negative electrode portion 22out in the electrode winding body 20 overlaps with a portion of the negative electrode current collector 25 in the Z-axis direction.

[0055] The secondary battery 1 may satisfy, for example, the following conditional formula (1): where θ1 denotes a first central angle of an opposing portion FA2 of the negative electrodes 22 in the electrode winding body 20, θ2 denotes a second central angle of a portion of the negative electrode current collector 25 where the notched portion 25K is provided, and θ3 denotes an overlapping angle of the first central angle θ1 and the second central angle θ2. Note that when θ0 denotes a central angle occupied by the sector-shaped portion 33 of the negative electrode current collector 25, the second central angle θ2 can be expressed as θ2 = 360° - θ0. 0.37≦θ3 / θ2≦1 ……(1)

[0056] The first central angle θ1 is, for example, not less than 35° and not more than 360°.

[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 are absorbed into the negative electrode 22 via the electrolyte. In addition, in the secondary battery 1, for example, during discharging, lithium ions are released from the negative electrode 22 and are absorbed into the positive electrode 21 via the electrolyte.

[0058] [1-3. Manufacturing method] 1 to 5B, and also with reference to Fig. 7, a method for manufacturing the secondary battery 1 will be described. Fig. 7 is a perspective view illustrating the manufacturing process of the secondary battery shown in Fig. 1.

[0059] First, a positive electrode current collector 21A is prepared, and a positive electrode active material layer 21B is selectively formed on the surface of the positive electrode current collector 21A to form a positive electrode 21 having a positive electrode covering portion 211 and a positive electrode exposed portion 212. Next, a negative electrode current collector 22A is prepared, and a negative electrode active material layer 22B is selectively formed on the surface of the negative electrode current collector 22A to form a negative electrode 22 having a negative electrode covering portion 221 and a negative electrode exposed portion 222. A drying process may be performed on the positive electrode 21 and the negative electrode 22. Next, a stacked structure S20 is produced by stacking the positive electrode 21 and the negative electrode 22 with the first separator member 23A and the second separator member 23B interposed between them such that the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 are opposite each other in the W-axis direction. When fabricating the laminated structure S20, the inner peripheral end 23A1 of the first separator member 23A and the inner peripheral end 23B1 of the second separator member are folded back so that the inner peripheral end 23A1 and the inner peripheral end 23B1 are sandwiched between the inner peripheral edge 21E2 of the positive electrode 21 and the negative electrode 22. The laminated structure S20 is then spirally wound so as to form through-holes 26. Furthermore, a fixing tape 46 is attached to the outermost periphery of the spirally wound laminated structure S20. As a result, the electrode roll 20 is obtained as shown in FIG. 7A.

[0060] Next, as shown in Fig. 7B, the end faces 41, 42 are locally bent by pressing the edge of a flat plate, for example, 0.5 mm thick, perpendicularly against the end faces 41, 42 of the electrode winding body 20, i.e., in the Z-axis direction. As a result, grooves 43 are formed that extend radially from the through-holes 26 in the radial direction (R direction). Note that the number and arrangement of grooves 43 shown in Fig. 7B are merely examples and the present disclosure is not limited thereto.

[0061] Next, as shown in FIG. 7C , substantially the same pressure is applied to the end faces 41 and 42 from above and below the electrode winding body 20 substantially simultaneously in a direction approximately perpendicular to the end faces 41 and 42. At this time, for example, a rod-shaped jig is inserted into the through hole 26. By doing so, the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 are bent, respectively, so that the end faces 41 and 42 become flat surfaces. At this time, the first edge portion 212E of the positive electrode exposed portion 212 and the second edge portion 222E of the negative electrode exposed portion 222 at the end faces 41 and 42 are bent while overlapping toward the through hole 26. Thereafter, the sector-shaped portion 31 of the positive electrode current collector 24 is joined to the end face 41 by laser welding or the like, and the sector-shaped portion 33 of the negative electrode current collector 25 is joined to the end face 42 by laser welding or the like.

[0062] Next, insulating tapes 53 and 54 are attached to predetermined positions of the electrode winding body 20. Thereafter, as shown in Fig. 7(D), the strip portion 32 of the positive current collector plate 24 is bent and inserted into the hole 12H of the insulating plate 12. In addition, the strip portion 34 of the negative current collector plate 25 is bent and inserted into the hole 13H of the insulating plate 13.

[0063] Next, the electrode winding body 20 assembled as described above is inserted into the outer can 11 shown in Figure 7(E), and then the bottom of the outer can 11 is welded to the negative electrode current collector plate 25. After that, a constricted portion 11S is formed near the open end 11N of the outer can 11. Furthermore, after the electrolyte is poured into the outer can 11, the strip portion 32 of the positive electrode current collector plate 24 is welded to the safety valve mechanism 30.

[0064] Next, as shown in FIG. 7(F), the gasket 15, the safety valve mechanism 30, and the battery lid 14 are sealed using the constricted portion 11S.

[0065] Through the above steps, the secondary battery 1 of this embodiment is completed.

[0066] [1-4. Actions and Effects] As described above, in the secondary battery 1 of this embodiment, the notched portion 25K of the negative electrode current collector 25 overlaps in the Z-axis direction with at least a portion of the opposing portion FA2 between the negative electrodes 22. That is, most of the opposing portion FA1 between the outermost positive electrode portion 21out of the positive electrode 21 and the outermost negative electrode portion 22out of the negative electrode 22 in the electrode winding body 20 overlaps in the Z-axis direction with a portion of the negative electrode current collector 25, specifically, with the sector-shaped portion 33, for example. Therefore, the opposing portion FA1 between the outermost positive electrode portion 21out and the outermost negative electrode portion 22out is protected by the sector-shaped portion 33 of the negative electrode current collector 25. Therefore, even if an impact is applied to the electrode winding body 20 due to a drop or the like, an internal short circuit between the outermost positive electrode portion 21out and the outermost negative electrode portion 22out can be avoided. This provides higher impact resistance and higher reliability.

[0067] In the secondary battery 1 of this embodiment, if the conditional formula (1) is satisfied in particular, it will have even higher impact resistance and will be able to obtain even higher reliability.

[0068] 4A , in the secondary battery 1 of the present embodiment, the positive electrode current collector 21A is covered with the positive electrode active material layer 21B from the outer peripheral edge 21E1 to the inner peripheral edge 21E2 of the electrode winding body 20. Therefore, compared to a case where the positive electrode current collector 21A has an exposed region near the inner peripheral edge 21E2 in the L-axis direction, for example, it is possible to eliminate the opposing portion between the positive electrode current collector 21A and the negative electrode active material layer 22B, thereby ensuring high safety.

[0069] The secondary battery 1 of this embodiment employs a so-called tabless structure. In this tabless structure, as shown in FIGS. 1 and 7(B), the electrode winding body 20 has a second edge 222E formed by folding the first portion 222A of the negative electrode exposed portion 222 toward the through-hole 26. Therefore, when the secondary battery 1 is dropped and the bottom end of the outer can 11 strikes a floor or other surface, the impact resistance of the secondary battery 1 is superior to that of a conventional secondary battery with a tab structure. The first reason for this is that the negative electrode 22 has the second edge 222E, which provides the second edge 222E with high mechanical strength. The second reason is that the strong second edge 222E between the outer can 11 and the facing portion FA1 maintains a certain distance between the outer can 11 and the facing portion FA1, making it difficult for external impacts applied to the outer can 11 to be transmitted to the facing portion FA1.

[0070] <2. Application Examples> The lithium ion secondary battery 1 according to the embodiment of the present disclosure can be used, for example, as described below.

[0071] [2-1. Battery pack] 8 is a block diagram showing an example of a circuit configuration when a battery according to an embodiment of the present invention (hereinafter referred to as a secondary battery) is applied to a battery pack 330. The battery pack 300 includes a battery pack 301, an exterior, a switch unit 304 including a charge control switch 302a and a discharge control switch 303a, a current detection resistor 307, a temperature detection element 308, and a control unit 310.

[0072] The battery pack 300 includes a positive terminal 321 and a negative terminal 322. When charging, the positive terminal 321 and the negative terminal 322 are connected to the positive terminal and the negative terminal of a charger, respectively, for charging. When using an electronic device, the positive terminal 321 and the negative terminal 322 are connected to the positive terminal and the negative terminal of the electronic device, respectively, for discharging.

[0073] The battery pack 301 is made up of a plurality of secondary batteries 301a connected in series or parallel. The secondary batteries 301a can be the above-described secondary battery 1. Note that, although Fig. 8 shows an example in which six secondary batteries 301a are connected in 2-parallel-3-series (2P3S) configuration, any other connection method may be used, such as n-parallel-m-series (n and m are integers).

[0074] Switch unit 304 includes charge control switch 302a and diode 302b, as well as discharge control switch 303a and diode 303b, and is controlled by control unit 310. Diode 302b has a polarity opposite to the charge current flowing from positive terminal 321 to battery pack 301 and a polarity forward to the discharge current flowing from positive terminal 322 to battery pack 301. Diode 303b has a polarity forward to the charge current and a polarity opposite to the discharge current. Although switch unit 304 is provided on the + side in FIG. 9, it may also be provided on the - side.

[0075] The charge control switch 302a is controlled by the charge / discharge control unit so that it is turned off when the battery voltage reaches the overcharge detection voltage and so that no charging current flows in the current path of the battery pack 301. After the charge control switch 302a is turned off, only discharging is possible via the diode 302b. Furthermore, the control unit 310 controls the switch so that it is turned off when a large current flows during charging and so that the charging current flows in the current path of the battery pack 301. The discharge control switch 303a is controlled by the control unit 310 so that it is turned off when the battery voltage reaches the overdischarge detection voltage and so that no discharging current flows in the current path of the battery pack 301. After the discharge control switch 303a is turned off, only charging is possible via the diode 303b. Furthermore, the control unit 310 controls the switch so that it is turned off when a large current flows during discharging and so that the discharging current flows in the current path of the battery pack 301.

[0076] Temperature detection element 308 is, for example, a thermistor that is provided near battery pack 301 and measures the temperature of battery pack 301, supplying the measured temperature to control unit 310. Voltage detection unit 311 measures the voltage of battery pack 301 and each secondary battery 301a that constitutes it, A / D converts the measured voltage, and supplies the result to control unit 310. Current measurement unit 313 measures the current using current detection resistor 307 and supplies the measured current to control unit 310. Switch control unit 314 controls charge control switch 302a and discharge control switch 303a of switch unit 304 based on the voltage and current input from voltage detection unit 311 and current measurement unit 313.

[0077] When the voltage of any of the multiple secondary batteries 301a falls below 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 charging / discharging. Here, for example, if the secondary battery is a lithium-ion secondary battery, the overcharge detection voltage is set to, for example, 4.20V±0.05V, and the overdischarge detection voltage is set to, for example, 2.4V±0.1V.

[0078] The charge / discharge switches can be semiconductor switches such as MOSFETs. In this case, the parasitic diodes of the MOSFETs function as diodes 302b and 303b. When P-channel FETs are used as the charge / discharge switches, switch control unit 314 supplies control signals DO and CO to the gates of charge control switch 302a and discharge control switch 303a, respectively. When charge control switch 302a and discharge control switch 303a are P-channel, they are turned on by a gate potential that is lower than the source potential by a predetermined value or more. That is, in normal charge and discharge operations, control signals CO and DO are set to low level, and charge control switch 302a and discharge control switch 303a are turned on.

[0079] For example, in the event of overcharging or overdischarging, the control signals CO and DO are set to high level, and the charge control switch 302a and the discharge control switch 303a are set to the OFF state.

[0080] The memory 317 is made up of RAM and ROM, such as non-volatile memory such as EPROM (Erasable Programmable Read Only Memory). The memory 317 stores in advance values calculated by the control unit 310 and the internal resistance value of each secondary battery 301a in its initial state measured during the manufacturing process, and can be rewritten as needed. Furthermore, by storing the full charge capacity of the secondary battery 301a, it is possible to calculate, for example, the remaining capacity together with the control unit 310.

[0081] The temperature detection unit 318 measures the temperature using the temperature detection element 308, and controls charging and discharging when abnormal heat is generated, and corrects the calculation of the remaining capacity.

[0082] [2-2. Energy storage system] The secondary battery according to the embodiment of the present disclosure described above can be mounted on devices such as electronic devices, electric vehicles, electric aircraft, and power storage devices, or can be used to supply power.

[0083] Examples of electronic devices include notebook computers, smartphones, tablet devices, PDAs (personal digital assistants), mobile phones, wearable devices, cordless phone handsets, video movie players, digital still cameras, e-books, electronic dictionaries, music players, radios, headphones, game consoles, navigation systems, memory cards, pacemakers, hearing aids, power tools, electric shavers, refrigerators, air conditioners, televisions, stereos, water heaters, microwave ovens, dishwashers, washing machines, dryers, lighting equipment, toys, medical equipment, robots, road conditioners, and traffic lights.

[0084] Examples of electric vehicles include railcars, golf carts, electric carts, electric cars (including hybrid cars), and the like, and the device is used as a driving power source or auxiliary power source for these. Examples of power storage devices include power storage power sources for buildings such as homes, or for power generation facilities.

[0085] Among the above-mentioned application examples, a specific example of a power storage system using a power storage device to which the above-mentioned secondary battery 1 of the present disclosure is applied will be described below.

[0086] (power tools) An example of an electric screwdriver as a power tool to which the secondary battery of the present disclosure can be applied will be outlined with reference to Figure 9. An electric screwdriver 431 has a motor 433, such as a DC motor, housed in its main body. Rotation of the motor 433 is transmitted to a shaft 434, which drives a screw into an object. The electric screwdriver 431 is provided with a trigger switch 432 that is operated by the user.

[0087] The battery pack 430 and the motor control unit 435 are housed in a housing below the handle of the electric screwdriver 431. The battery pack 300 can be used as the battery pack 430. The motor control unit 435 controls the motor 433. Each unit of the electric screwdriver 431 other than the motor 433 may be controlled by the motor control unit 435. The battery pack 430 and the electric screwdriver 431 are engaged with each other by engaging members provided thereon. As will be described later, the battery pack 430 and the motor control unit 435 each include a microcomputer. Battery power is supplied from the battery pack 430 to the motor control unit 435, and information about the battery pack 430 is communicated between the microcomputers of the two units.

[0088] The battery pack 430 is, for example, detachable from the electric screwdriver 431. The battery pack 430 may be built into the electric screwdriver 431. The battery pack 430 is attached to a charging device when charging. When the battery pack 430 is attached to the electric screwdriver 431, a part of the battery pack 430 may be exposed to the outside of the electric screwdriver 431 so that the exposed part can be seen by the user. For example, an LED may be provided on the exposed part of the battery pack 430 so that the user can check whether the LED is on or off.

[0089] The motor control unit 435 controls, for example, the rotation and stopping of the motor 433, as well as the direction of rotation. Furthermore, it cuts off the power supply to the load during over-discharge. The trigger switch 432 is inserted, for example, between the motor 433 and the motor control unit 435. When the user presses the trigger switch 432, power is supplied to the motor 433, causing the motor 433 to rotate. When the user releases the trigger switch 432, the rotation of the motor 433 stops.

[0090] (Unmanned aerial vehicle) An example in which the secondary battery of the present disclosure is applied as a power source for an electric aircraft will be described with reference to FIG. 10. The secondary battery of the present disclosure can be used as a power source for unmanned aircraft such as drones. FIG. 10 is a plan view of the unmanned aircraft. The base of the unmanned aircraft is composed of a cylindrical or rectangular tubular body portion as the center, and support shafts 442a-442f fixed to the upper part of the body portion. In FIG. 9, the body portion has a hexagonal tubular shape, and six support shafts 442a-442f are configured to extend radially at equiangular intervals from the center of the body portion. The body portion and support shafts 442a-442f are composed of lightweight, high-strength materials.

[0091] Motors 443a to 443f are attached to the tips of support shafts 442a to 442f, respectively, as drive sources for the rotors. Rotor blades 444a to 444f are attached to the rotation shafts of motors 443a to 443f. Circuit unit 445, which includes motor control circuits for controlling each motor, is attached to the center (top of the body) where support shafts 442a to 442f intersect.

[0092] Furthermore, a battery unit serving as a power source is disposed below the body. The battery unit has three battery packs to supply power to pairs of motors and rotors spaced 180 degrees apart. Each battery pack includes, for example, a lithium-ion secondary battery and a battery control circuit that controls charging and discharging. Battery pack 300 can be used as the battery pack. Motor 443a and rotor 444a form a pair, and motor 443d and rotor 444d form a pair. Similarly, motor 443b and rotor 444b form a pair, and motor 443e and rotor 444e form a pair, and motor 443c and rotor 444c form a pair, and motor 443f and rotor 444f form a pair. There are an equal number of these pairs and battery packs.

[0093] (Vehicle energy storage system) An example in which the secondary battery of the present disclosure is applied to a power storage system for an electric vehicle will be described with reference to Fig. 11. Fig. 11 shows a schematic diagram of 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 on a power / driving force conversion device using electric power generated by a generator driven by an engine or electric power temporarily stored in a battery.

[0094] Hybrid vehicle 600 is equipped with an engine 601, a generator 602, an electric power driving force conversion device 603, drive wheels 604a, 604b, wheels 605a, 605b, a battery 608, a vehicle control device 609, various sensors 610, and a charging port 611. Battery pack 300 of the present disclosure described above can be applied to battery 608.

[0095] The hybrid vehicle 600 runs using an electric power driving force conversion device 603 as a power source. An example of the electric power driving force conversion device 603 is a motor. The electric power driving force conversion device 603 is operated by power from a battery 608, and the rotational force of the electric power driving force conversion device 603 is transmitted to driving wheels 604a, 604b. Note that by using direct current-alternating current (DC-AC) or inverse conversion (AC-DC conversion) where necessary, the electric power driving force conversion device 603 can be either an AC motor or a DC motor. Various sensors 610 control the engine speed via a vehicle control device 609 and the opening degree of a throttle valve (not shown) (throttle opening degree). The various sensors 610 include a speed sensor, an acceleration sensor, an engine speed sensor, etc.

[0096] The rotational force of the engine 601 is transmitted to the generator 602, and the electric power generated by the generator 602 by the rotational force can be stored in the battery 608. When the hybrid vehicle 600 is decelerated by a braking mechanism (not shown), the resistance force at the time of deceleration is transmitted to the electric power driving force conversion device. The torque is applied to the drive power converter 603 as a rotational force, and the regenerative power generated by the drive power converter 603 is stored in the battery 608.

[0097] When battery 608 is connected to a power source external to hybrid vehicle 600, it can receive power from the external power source via charging port 611 as an input port and store the received power.

[0098] Furthermore, the vehicle may be equipped with an information processing device that processes information related to vehicle control based on information about the secondary battery. Such an information processing device may, for example, display the remaining battery capacity based on information about the remaining capacity of the secondary battery.

[0099] The above description has been given with reference to a series hybrid vehicle that runs on a motor using power generated by a generator driven by an engine or power temporarily stored in a battery. However, the secondary battery of the present disclosure can also be effectively applied to a parallel hybrid vehicle that uses both the engine and motor outputs as drive sources and switches between three modes as appropriate: running on the engine alone, running on the motor alone, or running on both the engine and the motor. Furthermore, the secondary battery of the present disclosure can also be effectively applied to so-called electric vehicles that run on only the drive motor without using an engine. [Example]

[0100] An embodiment of the present disclosure will be described.

[0101] <1. Check for internal short circuits during drop testing> (Examples 1-1 to 1-5) As described below, a cylindrical secondary battery 1 shown in Fig. 1 was fabricated, and then its battery characteristics were evaluated. Here, a secondary battery 1 having dimensions of 21 mm in diameter and 70 mm in length was fabricated.

[0102] [Production method] First, a 12 μm-thick aluminum foil was prepared as the positive electrode current collector 21A. Next, a layered lithium oxide having a Ni ratio of 85% or more in lithium nickel cobalt aluminum oxide (NCA) was used as the positive electrode active material. A positive electrode binder made of polyvinylidene fluoride was mixed with a conductive additive containing carbon black, acetylene black, and ketjen black to obtain a positive electrode mixture. The mixture ratio of the positive electrode active material, positive electrode binder, and conductive additive was 96.4:2:1.6. Next, the positive electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone) and stirred to prepare a paste-like positive electrode mixture slurry. Next, the positive electrode mixture slurry was applied to predetermined areas on both sides of the positive electrode current collector 21A using a coating device, and the positive electrode mixture slurry was then dried to form the positive electrode active material layer 21B. Furthermore, a coating material containing polyvinylidene fluoride (PVDF) was applied to a surface of the positive electrode exposed portion 212 adjacent to the positive electrode covering portion 211, and the coating material was dried to form an insulating layer 101 having a width of 3 mm and a thickness of 8 μm. After that, a roll press was used to compression-mold the positive electrode active material layer 21B. In this manner, a positive electrode 21 having a positive electrode covering portion 211 and a positive electrode exposed portion 212 was obtained. The width of the positive electrode covering portion 211 in the W-axis direction was 60 mm, and the width of the positive electrode exposed portion 212 in the W-axis direction was 7 mm. The length of the positive electrode 21 in the L-axis direction was 1700 mm. In the obtained positive electrode 21, the area density of the positive electrode active material layer 21B was 22.0 mg / cm. 2 The volume density of the positive electrode active material layer 21B is 3.55 g / cm 3 The thickness T1 of the positive electrode covering portion 211 was 74.3 μm.

[0103] Additionally, an 8 μm-thick copper foil was prepared as the negative electrode current collector 22A. Next, a negative electrode active material, which was a mixture of a carbon material made of graphite and SiO, a negative electrode binder made of polyvinylidene fluoride, and a conductive additive, which was a mixture of carbon black, acetylene black, and ketjen black, was mixed to obtain a negative electrode mixture. The mixing ratio of the negative electrode active material, the negative electrode binder, and the conductive additive was 96.1:2.9:1.0. The mixing ratio of graphite to SiO in the negative electrode active material was 95:5. Next, the negative electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry was applied to predetermined regions on both sides of the negative electrode current collector 22A using a coating device, and the negative electrode mixture slurry was then dried to form the negative electrode active material layer 22B. Thereafter, the negative electrode active material layer 22B was compression-molded using a roll press. As a result, a negative electrode 22 having a negative electrode covering portion 221 and a negative electrode exposed portion 222 was obtained. Here, the width of the negative electrode covering portion 221 in the W-axis direction was set to 62 mm, and the width of the first portion 222A of the negative electrode exposed portion 222 in the W-axis direction was set to 4 mm. The length of the negative electrode 22 in the L-axis direction was set to 1760 mm. In the obtained negative electrode 22, the area density of the negative electrode active material layer 22B was 10.83 mg / cm 2 The volume density of the negative electrode active material layer 22B is 1.50 g / cm 3 The thickness of the negative electrode covering portion 221 was 80.2 μm.

[0104] Next, the positive electrode 21 and the negative electrode 22 were stacked with the first separator member 23A and the second separator member 23B interposed therebetween so that the positive electrode exposed portion 212 and the first portion 222A of the negative electrode exposed portion 222 were on opposite sides of each other in the W-axis direction, thereby producing a laminate structure S20. The laminate structure S20 was produced so that the positive electrode active material layer 21B did not protrude from the negative electrode active material layer 22B in the W-axis direction. Polyethylene sheets having a width of 65 mm and a thickness of 14 μm were used as the first separator member 23A and the second separator member 23B. When producing the laminate structure S20, the inner peripheral end portion 23A1 of the first separator member 23A and the inner peripheral end portion 23B1 of the second separator member were folded back so that the inner peripheral end portion 23A1 and the inner peripheral end portion 23B1 were sandwiched between the inner peripheral edge 21E2 of the positive electrode 21 and the negative electrode 22. Here, the length L20 of the overlapping portion OL20 was adjusted to 1 mm. Thereafter, the laminated structure S20 was spirally wound so as to form the through-holes 26, and a fixing tape 46 was attached to the outermost periphery of the wound laminated structure S20. In this way, the electrode wound body 20 was obtained.

[0105] Next, the edges of a 0.5 mm thick flat plate were pressed against the end faces 41 and 42 of the electrode winding 20 in the Z-axis direction to locally bend the end faces 41 and 42, creating grooves 43 extending radially from the through hole 26 in the radial direction (R direction).

[0106] Next, substantially the same pressure was applied to end face 41 and end face 42 from above and below electrode winding body 20 substantially simultaneously and in a direction approximately perpendicular to end face 41 and end face 42, thereby bending positive electrode exposed portion 212 and first portion 222A of negative electrode exposed portion 222, respectively, to make end face 41 and end face 42 flat. At this time, first edge 212E of positive electrode exposed portion 212 and second edge 222E of negative electrode exposed portion 222 at end face 41 and end face 42 were bent while overlapping toward through hole 26. Thereafter, sector-shaped portion 31 of positive electrode current collector plate 24 was joined to end face 41 by laser welding, and sector-shaped portion 33 of negative electrode current collector plate 25 was joined to end face 42 by laser welding. In this case, as shown in Table 1 below, the first central angle θ1 was set to 80°, the second central angle θ2 was set to 135°, and the angle θ3 was set to fall within the range of 80° to 10°.

[0107] Next, insulating tapes 53, 54 were attached to predetermined positions of the electrode winding body 20, and then the strip portion 32 of the positive electrode current collector 24 was bent to insert the strip portion 32 into the hole 12H of the insulating plate 12, and the strip portion 34 of the negative electrode current collector 25 was bent to insert the strip portion 34 into the hole 13H of the insulating plate 13.

[0108] Next, the electrode winding body 20 assembled as described above was inserted into the outer can 11, and the bottom of the outer can 11 and the negative electrode current collector plate 25 were welded together. After that, a constricted portion 11S was formed near the open end 11N of the outer can 11. Furthermore, an electrolyte was poured into the outer can 11, and the strip portion 32 of the positive electrode current collector plate 24 and the safety valve mechanism 30 were welded together.

[0109] The electrolyte used was a solvent containing ethylene carbonate (EC) and dimethyl carbonate (DMC) as the main solvent, to which fluoroethylene carbonate (FEC) and succinonitrile (SN) were added, and LiBF4 and LiPF6 were used as electrolyte salts. In the lithium-ion secondary battery of this example, the respective contents (by weight) of EC, DMC, FEC, SN, LiBF4, and LiPF6 in the electrolyte were 12.7:56.2:12.0:1.0:1.0:17.1.

[0110] Finally, the gasket 15, the safety valve mechanism 30, and the battery lid 14 were used to seal the necked portion 11S.

[0111] As a result, a secondary battery 1 of Example 1-1 was obtained. The number of samples (n number) was set to 3, and the median was used as the characteristic value, i.e., the number of drops until a short circuit occurred. In each of the examples and comparative examples other than Example 1-1 described below, the number of samples (n number) was also set to 3, and the median was used as each characteristic value.

[0112] [Evaluation of battery characteristics] The battery characteristics of the secondary battery 1 of Example 1-1 obtained as described above were evaluated, and the results shown in Table 1 were obtained. Specifically, a drop test was conducted under the following test conditions. The drop test was repeated until a short circuit occurred inside the secondary battery 1, and the number of drops until the short circuit occurred was counted. The results are shown in Table 1. The occurrence of a short circuit was determined by measuring the open circuit voltage (OCV) after the cycle test for 48 hours. If a voltage drop of 150 mV or more was observed from the initial voltage, it was determined that an internal short circuit had occurred. In the drop test, a sample of the secondary battery 1 was dropped vertically from a height of 2 m onto a horizontal concrete floor, causing the bottom of the outer can 11 to impact the concrete floor. The secondary battery 1 was dropped in a position such that the central axis CL was inclined 30° relative to the concrete floor, i.e., inclined 60° relative to the vertical.

[0113] [Table 1]

[0114] (Comparative Example 1-1) A secondary battery 101 was fabricated as Comparative Example 1-1. In the secondary battery 101 of Comparative Example 1-1, the angle θ3 was set to 0°, as shown in FIG. 12 . That is, the entire opposing portion FA1 between the outermost positive electrode portion 21out and the outermost negative electrode portion 22out in the electrode winding body 20 was set to overlap the cutout portion 25K in the Z-axis direction without overlapping the sector-shaped portion 33 of the negative electrode current collector plate 25. Except for this point, the secondary battery 101 of Comparative Example 1-1 had the same configuration as the secondary battery 1 of Example 1-1. The secondary battery 101 was also evaluated for battery characteristics in the same manner as the secondary battery 1. The results are shown in Table 1.

[0115] [Consideration] As shown in Table 1, in Examples 1-1 to 1-5, more drops were required before a short circuit occurred compared to Comparative Example 1-1. That is, in Examples 1-1 to 1-5, at least a portion of the facing portion FA1 overlaps with the sector-shaped portion 33 of the negative electrode current collector plate 25 in the Z-axis direction, and it was confirmed that the impact resistance was improved compared to Comparative Example 1-1. In particular, in Examples 1-1 and 1-2, the angle ratio θ3 / θ2 was 0.37 or more, and therefore it was found that higher impact resistance was obtained than in Examples 1-3 to 1-5, in which the angle ratio θ3 / θ2 was 0.30 or less.

[0116] (Examples 2-1 to 2-5) Secondary batteries 1 were fabricated as Examples 2-1 to 2-5. In the secondary batteries 1 of Examples 2-1 to 2-5, as shown in Table 2 below, the first central angle θ1 was 80°, the second central angle θ2 was 100°, and the angle θ3 was in the range of 80° to 20°. Except for this point, the configuration of the secondary batteries 1 of Examples 2-1 to 2-5 was the same as that of the secondary batteries 1 of Examples 1-1 to 1-5. The secondary batteries 1 of Examples 2-1 to 2-5 were also evaluated for battery characteristics in the same manner as the secondary batteries 1 of Examples 1-1 to 1-5. The results are shown in Table 2.

[0117] [Table 2]

[0118] (Comparative Example 2-1) A secondary battery 101 was fabricated as Comparative Example 2-1. The secondary battery 101 of Comparative Example 2-1 had the same configuration as the secondary battery 1 of Example 2-1, except that the angle θ3 was set to 0°. The secondary battery 101 of Comparative Example 2-1 was also evaluated for battery characteristics in the same manner as the secondary battery 1 of Example 2-1. The results are shown in Table 2.

[0119] [Consideration] As shown in Table 2, in Examples 2-1 to 2-5, more drops were required before a short circuit occurred compared to Comparative Example 2-1. That is, in Examples 2-1 to 2-5, at least a portion of the facing portion FA1 overlaps with the sector-shaped portion 33 of the negative electrode current collector plate 25 in the Z-axis direction, and it was confirmed that the impact resistance was improved compared to Comparative Example 2-1. In particular, in Examples 2-1 to 2-4, the angle ratio θ3 / θ2 was 0.35 or more, and therefore it was found that higher impact resistance was obtained than in Example 2-5, in which the angle ratio θ3 / θ2 was 0.20.

[0120] (Examples 3-1 to 3-4) Secondary batteries 1 were fabricated as Examples 3-1 to 3-4. In the secondary batteries 1 of Examples 3-1 to 3-4, as shown in Table 3 below, the first central angle θ1 was 80°, the second central angle θ2 was 170°, and the angle θ3 was in the range of 80° to 20°. Except for this point, the configuration of the secondary batteries 1 of Examples 3-1 to 3-4 was the same as that of the secondary batteries 1 of Examples 1-1 to 1-5. The secondary batteries 1 of Examples 3-1 to 3-4 were also evaluated for battery characteristics in the same manner as the secondary batteries 1 of Examples 1-1 to 1-5. The results are shown in Table 3.

[0121] [Table 3]

[0122] (Comparative Example 3-1) A secondary battery 101 was fabricated as Comparative Example 3-1. The secondary battery 101 of Comparative Example 3-1 had the same configuration as the secondary battery 1 of Example 3-1, except that the angle θ3 was set to 0°. The secondary battery 101 of Comparative Example 3-1 was also evaluated for battery characteristics in the same manner as the secondary battery 1 of Example 3-1. The results are shown in Table 3.

[0123] [Consideration] As shown in Table 3, in Examples 3-1 to 3-4, more drops were required before a short circuit occurred compared to Comparative Example 3-1. That is, in Examples 3-1 to 3-4, at least a portion of the facing portion FA1 overlaps with the sector-shaped portion 33 of the negative electrode current collector plate 25 in the Z-axis direction, and it was confirmed that the impact resistance was improved compared to Comparative Example 3-1. In particular, in Examples 3-1 and 3-2, the angle ratio θ3 / θ2 was 0.35 or more, and therefore it was found that higher impact resistance was obtained than in Examples 3-3 to 3-4, in which the angle ratio θ3 / θ2 was 0.24 or less.

[0124] (Examples 4-1 to 4-5) Secondary batteries 1 were fabricated as Examples 4-1 to 4-5. In the secondary batteries 1 of Examples 4-1 to 4-5, as shown in Table 4 below, the first central angle θ1 was set to 100°, the second central angle θ2 was set to 100°, and the angle θ3 was set to a range of 100° to 10°. Except for this point, the configuration of the secondary batteries 1 of Examples 4-1 to 4-5 was the same as that of the secondary batteries 1 of Examples 1-1 to 1-5. The secondary batteries 1 of Examples 4-1 to 4-5 were also evaluated for battery characteristics in the same manner as the secondary batteries 1 of Examples 1-1 to 1-5. The results are shown in Table 4.

[0125] [Table 4]

[0126] (Comparative Example 4-1) A secondary battery 101 was fabricated as Comparative Example 4-1. The secondary battery 101 of Comparative Example 4-1 had the same configuration as the secondary battery 1 of Example 4-1, except that the angle θ3 was set to 0°. The secondary battery 101 of Comparative Example 4-1 was also evaluated for battery characteristics in the same manner as the secondary battery 1 of Example 4-1. The results are shown in Table 4.

[0127] [Consideration] As shown in Table 4, in Examples 4-1 to 4-5, more drops were required before a short circuit occurred compared to Comparative Example 4-1. That is, in Examples 4-1 to 4-5, at least a portion of the facing portion FA1 overlaps with the sector-shaped portion 33 of the negative electrode current collector plate 25 in the Z-axis direction, and it was confirmed that the impact resistance was improved compared to Comparative Example 4-1. In particular, in Examples 4-1 to 4-3, the angle ratio θ3 / θ2 was 0.35 or more, and therefore it was found that higher impact resistance was obtained than in Examples 4-4 to 4-5, in which the angle ratio θ3 / θ2 was 0.20 or less.

[0128] Although the present technology has been described above with reference to an embodiment and examples, the configuration of the present technology is not limited to the configuration described in the embodiment and examples, and various modifications are possible.

[0129] Specifically, in the above embodiment and example, the electrode reactant is lithium, but the electrode reactant is not particularly limited. Therefore, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals 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 winding body formed by winding a laminate structure in which a first electrode and a second electrode are stacked with a separator interposed therebetween around a central axis extending in a first direction; a first electrode current collector plate disposed to face a first end surface of the electrode winding body in the first direction; a second electrode current collector plate disposed to face a second end surface of the electrode winding body opposite to the first end surface in the first direction; An electrolyte; a battery can containing the electrode winding body, the first electrode current collector plate, the second electrode current collector plate, and the electrolyte; Equipped with the first electrode has a first electrode covered portion in which a first electrode current collector is covered with a first electrode active material layer, and a first electrode exposed portion in which the first electrode current collector is exposed without being covered with the first electrode active material layer and joined to the first electrode current collector, the second electrode has a second electrode covered portion in which a second electrode current collector is covered with a second electrode active material layer, and a second electrode exposed portion in which the second electrode current collector is exposed without being covered with the second electrode active material layer and joined to the second electrode current collector, the electrode winding body has an opposing portion of the second electrodes, in which an outermost peripheral portion of the second electrode and an inner peripheral portion of the second electrode located inside the outermost peripheral portion of the second electrode face each other without the first electrode therebetween, the second electrode current collector plate has a notched portion in a part of a circumferential direction surrounding the central axis, The notched portion overlaps with at least a part of the opposing portions of the second electrodes in the first direction. Secondary battery.

2. a solid portion of the second electrode current collector other than the notched portion overlaps in the first direction with at least a part of an opposing portion between the outermost peripheral portion of the first electrode and the outermost peripheral portion of the second electrode; The secondary battery according to claim 1 .

3. the notched portion overlaps with the entire opposing portion of the second electrodes in the first direction. The secondary battery according to claim 1 .

4. When a first central angle of the opposing portion of the second electrodes in the electrode winding body is θ1, a second central angle of the notched portion of the second electrode current collector plate is θ2, and an angle at which the first central angle and the second central angle overlap is θ3, the following conditional formula (1) is satisfied: The secondary battery according to claim 3. 0.37≦θ3 / θ2≦1 ……(1)

5. The first central angle is equal to or greater than 35° and equal to or less than 360°. The secondary battery according to claim 4.

6. 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 collector is a positive electrode current collector, the first electrode covering portion is a positive electrode covering 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 collector is a negative electrode current collector, the second electrode covering portion is a negative electrode covering portion, and the second electrode exposed portion is a negative electrode exposed portion. The secondary battery according to claim 1 .

7. In the electrode winding body, the outermost periphery of the negative electrode is located outside the outermost periphery of the positive electrode. The secondary battery according to claim 6.

8. In the positive electrode, the positive electrode active material layer covers the positive electrode current collector from the outer peripheral edge of the positive electrode to the inner peripheral edge of the positive electrode in the winding direction of the electrode winding body. The secondary battery according to claim 6.

9. the separator includes a porous film containing polyolefin as a substrate, The thickness of the porous membrane is 10 μm or more and 15 μm or less, The surface density of the porous membrane is 6.3 g / m ２ 8.3g / m or more ２ is The secondary battery according to claim 1 .

10. A plurality of first edge portions of the first electrode exposed portion wound around the central axis, which are adjacent in the radial direction of the electrode wound body, are bent toward the central axis so as to overlap each other. The secondary battery according to claim 1 .

11. A plurality of second edge portions of the second electrode exposed portion wound around the central axis, which are adjacent in the radial direction of the electrode wound body, are bent toward the central axis so as to overlap each other. The secondary battery according to claim 1 .

12. the second electrode active material layer is a negative electrode active material layer, The negative electrode active material layer includes a negative electrode active material containing at least one of silicon, silicon oxide, a carbon silicon compound, and a silicon alloy. The secondary battery according to claim 1 .

13. the first electrode active material layer is a positive electrode active material layer, The positive electrode active material layer contains a positive electrode active material containing at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. The secondary battery according to claim 1 .

14. The secondary battery according to any one of claims 1 to 13; a control unit that controls the secondary battery; an exterior body that houses the secondary battery; A battery pack having

15. The secondary battery according to any one of claims 1 to 13; a conversion unit that converts the power supplied from the secondary battery into driving force; a drive unit that drives in response to the drive force; a control unit that controls the operation of the secondary battery; An electric vehicle equipped with

16. The battery pack according to claim 14; A plurality of rotors; a motor for rotating each of the rotors; a support shaft that supports the rotor and the motor; a motor control unit that controls the rotation of the motor; a power supply line for supplying power to the motor; The battery pack is connected to the power supply line Electric aircraft.

17. The secondary battery according to any one of claims 1 to 13; a movable part that receives power from the secondary battery; Power tools equipped with.

18. An electronic device comprising the secondary battery according to any one of claims 1 to 13 as a power supply source.

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