Secondary battery, electronic device, and power tool

Abstract

Provided is a battery for high-rate discharge that does not cause internal short-circuiting while further improving battery capacity. A secondary battery has a negative electrode with a negative electrode active material covered portion in which a negative electrode active material layer is covered on a negative electrode foil in a strip shape, a first negative electrode active material non-covered portion that extends in a long side direction of the negative electrode foil, a second negative electrode active material non-covered portion that is provided at an end portion on a winding start side in the long side direction, and an insulating resin portion that is provided between the negative electrode active material covered portion and the first negative electrode active material non-covered portion. The positive electrode active material non-covered portion is joined to a positive electrode current collector plate on one side of an end portion of an electrode winding body, and the first negative electrode active material non-covered portion is joined to a negative electrode current collector plate on the other side of the end portion of the electrode winding body. The electrode winding body has a flat surface that is formed by bending and overlapping either one or both of the positive electrode active material non-covered portion and the first negative electrode active material non-covered portion toward a central axis of a structure of the winding, and a groove that is formed in the flat surface.

Description

Technical Field

[0001] This invention relates to secondary batteries, electronic devices, and power tools. Background Technology

[0002] Lithium-ion batteries have also been developed for applications requiring high output, such as power tools and automobiles. One method to achieve high output is high-rate discharge, which involves a large current flowing from the battery. During high-rate discharge, due to the large current flowing out, it is desirable to reduce the battery's internal resistance.

[0003] For example, Patent Document 1 describes a secondary battery in which an active material mixture layer is formed in the width direction of the negative electrode plate. Patent Document 2 describes a secondary battery formed by cutting the negative electrode plate at both the starting and ending points where the active material mixture layer is formed.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-216403

[0007] Patent Document 2: Japanese Patent Application Publication No. 2006-32112 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] In the technology described in Patent Document 1, the dimensional deviation of the active material mixture layer in the width direction of the negative electrode is not considered. Therefore, the area of ​​the active material mixture layer of the positive electrode needs to be adjusted so that the active material mixture layer of the positive electrode and the active material mixture layer of the negative electrode are reliably aligned. As a result, there is a problem that the area of ​​the active material mixture layer of the positive electrode becomes smaller, resulting in a decrease in battery capacity. In addition, in the battery described in Patent Document 2, when the current collector is pressed at the end of the electrode winding body, there is a problem that the active material of the negative electrode peels off and falls off from the active material covering portion of the negative electrode, causing an internal short circuit due to the fallen active material.

[0010] Therefore, one of the objectives of this invention is to provide a battery for high-rate discharge that increases battery capacity without causing internal short circuits.

[0011] Technical solutions for solving technical problems

[0012] This invention provides a secondary battery.

[0013] The battery canister contains an electrode winding, a positive current collector, and a negative current collector. The electrode winding is formed by stacking strip-shaped positive and strip-shaped negative electrodes with a separator in between.

[0014] The positive electrode has: a positive electrode active material covered portion, wherein a layer of positive electrode active material is coated on a strip-shaped positive electrode foil; and a positive electrode active material uncovered portion.

[0015] The negative electrode comprises: a negative electrode active material covering portion, on which a layer of negative electrode active material is covered on a strip-shaped negative electrode foil; a first negative electrode active material non-covering portion, extending along the long side direction of the negative electrode foil; a second negative electrode active material non-covering portion, disposed at the end on the winding start side along the long side direction; and an insulating resin portion, disposed between the negative electrode active material covering portion and the first negative electrode active material non-covering portion.

[0016] The uncovered portion of the positive electrode active material is bonded to the positive electrode current collector on one side of the end of the electrode winding body.

[0017] The non-covered portion of the first negative electrode active material is joined to the negative electrode current collector on the other side of the end of the electrode winding body.

[0018] The electrode winding body has: a flat surface formed by bending and coinciding with the central axis of the winding structure of either or both of the non-covered portion of the positive electrode active material and the non-covered portion of the first negative electrode active material; and a groove formed on the flat surface.

[0019] The effects of the invention

[0020] At least according to embodiments of the present invention, a battery for high-rate discharge can be realized without causing internal short circuits. It should be noted that the content of the present invention should not be construed as limiting the effects illustrated in this specification. Attached Figure Description

[0021] Figure 1 A and Figure 1 Figure B is the figure referred to when explaining the issues that should be considered in this invention.

[0022] Figure 2 This is a cross-sectional view of a lithium-ion battery according to one embodiment.

[0023] Figure 3 A is a top view of the positive current collector according to an embodiment. Figure 3 B is a top view of the negative current collector according to an embodiment.

[0024] Figure 4 A and Figure 4 Figure B is a diagram referred to when illustrating the negative electrode involved in one implementation.

[0025] Figure 5 It is a diagram showing the positive electrode, negative electrode, and diaphragm before winding.

[0026] Figure 6 A to Figure 6F is a diagram illustrating the assembly process of a lithium-ion battery according to one embodiment.

[0027] Figure 7 A and Figure 7 Figure B is used to illustrate Comparative Example 1.

[0028] Figure 8 A and Figure 8 Figure B is used to illustrate Comparative Example 2.

[0029] Figure 9 A and Figure 9 Figure B is used to illustrate comparative example 3.

[0030] Figure 10 This is a connection diagram illustrating a battery pack as an application example of the present invention.

[0031] Figure 11 This is a connection diagram illustrating an application example of the present invention using an electric tool.

[0032] Figure 12 This is a connection diagram used to illustrate an electric vehicle as an application example of the present invention. Detailed Implementation

[0033] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the descriptions will proceed in the following order.

[0034] <Issues to be considered in one implementation>

[0035] <One implementation method>

[0036] <Variation Example>

[0037] <Application Examples>

[0038] The embodiments described below are preferred examples of the present invention, and the content of the present invention is not limited to these embodiments. It should be noted that, for ease of understanding, sometimes a portion of the structure in each figure is enlarged or reduced, or some illustrations are simplified.

[0039] <Issues to be considered in one implementation>

[0040] First, to facilitate understanding of the present invention, while referring to... Figure 1 A and Figure 1 B, on the one hand, describes one of the issues that should be considered in one implementation method. Figure 1 A and Figure 1In Figure B, reference numeral 110 indicates the negative electrode foil, reference numeral 111 indicates the negative electrode active material, i.e., the negative electrode active material covered portion, disposed on the negative electrode foil 110, and reference numeral 112 indicates the non-covered portion of the negative electrode active material in the negative electrode foil 110. It should be noted that in the descriptions of the positive and negative electrodes before winding, the winding direction (positive or negative electrode direction) is sometimes referred to as... Figure 1 A and Figure 1 The direction of the X-axis in B is called the long side direction, and the direction orthogonal to the long side direction is called the long side direction. Figure 1 A and Figure 1 The Y-axis direction in B is called the width direction, and the Z-axis direction is called the thickness direction.

[0041] Typically, the negative electrode active material is applied using a method known as intermittent coating. This method involves temporarily stopping the spraying process after each application of the negative electrode active material, followed by another spraying and coating. To increase the pressure during the spraying of the negative electrode active material, such as... Figure 1 As shown by reference numeral 113 in the accompanying drawings, sometimes the end of the negative electrode active material covering 111 is partially extended. Furthermore, since the negative electrode active material is typically fluid, therefore... Figure 1 As shown by reference numeral 114 in Figure B, unevenness sometimes occurs at the end of the negative electrode active material covering portion 111. This problem also occurs when the negative electrode active material covering portion 111 is formed by continuous coating. Thus, due to the expansion, necking, and unevenness at the end of the negative electrode active material covering portion 111, the length D1 in the width direction of the negative electrode active material covering portion 111 deviates. Considering this deviation in length D1, in order to reliably align the positive electrode active material covering portion (not shown) with the negative electrode active material covering portion 111, it is necessary to reduce the length D2 in the width direction of the positive electrode active material covering portion. Therefore, there is a problem of a smaller positive electrode active material covering area and a reduced battery capacity. Based on the above points, an embodiment of the present invention will be described in detail.

[0042] <One implementation method>

[0043] In one embodiment of the present invention, a cylindrical lithium-ion battery will be used as an example of a secondary battery. First, the overall structure of the lithium-ion battery will be described. Figure 2 This is a schematic cross-sectional view of lithium-ion battery 1. Lithium-ion battery 1 is, for example, as shown below. Figure 2 The image shows a cylindrical lithium-ion battery 1 in which the electrode winding body 20 is housed inside the battery canister 11.

[0044] The lithium-ion battery 1 has a generally cylindrical battery can 11, and inside the battery can 11 are a pair of insulating plates 12 and 13 and an electrode winding body 20. It should be noted that the lithium-ion battery 1 may also include, for example, any one or more of the following inside the battery can 11: a thermistor (PTC) element and reinforcing components.

[0045] [Battery can]

[0046] The battery can 11 is the main component for housing the electrode winding 20. The battery can 11 is, for example, a cylindrical container with one open end and the other closed. That is, the battery can 11 has an open end (open end 11N). The battery can 11 may contain one or more of the following metallic materials: iron, aluminum, and their alloys. The surface of the battery can 11 may be plated with one or more of the following metallic materials: nickel, for example.

[0047] [Insulating board]

[0048] Insulating plates 12 and 13 are positioned relative to the winding axis of electrode winding body 20 (passing approximately at the center of the end face of electrode winding body 20 and parallel to the winding axis of electrode winding body 20). Figure 2 A disc-shaped plate that is approximately perpendicular to a plane (parallel to the Z-axis). Additionally, insulating plates 12 and 13 are configured, for example, to clamp the electrode winding 20 between each other.

[0049] [Riveting Structure]

[0050] On the open end face 11N of the battery can 11, the battery cover 14 and the safety valve mechanism 30 are riveted together via gaskets 15 to form a riveting structure 11R (curled structure). Thus, with the electrode winding body 20 and the like housed inside the battery can 11, the battery can 11 is sealed.

[0051] [Battery cover]

[0052] The battery cover 14 is a component that primarily closes the open end face 11N of the battery can 11 when the electrode winding body 20 and the like are housed inside the battery can 11. The battery cover 14, for example, is made of the same material as the battery can 11. The central region of the battery cover 14 protrudes, for example, in the +Z direction. Therefore, the area outside the central region of the battery cover 14 (the peripheral region) comes into contact with, for example, the safety valve mechanism 30.

[0053] [washer]

[0054] The gasket 15 is a component that mainly seals the gap between the bend 11P and the battery cover 14 by being located between the battery can 11 (bent portion 11P) and the battery cover 14. For example, asphalt or similar materials may be coated on the surface of the gasket 15.

[0055] The gasket 15 may contain one or more insulating materials. The type of insulating material is not particularly limited; for example, polymers such as polybutylene terephthalate (PBT) and polypropylene (PP) can be used. Among these, polybutylene terephthalate is preferred as the insulating material. This is because it can adequately seal the gap between the bent portion 11P and the battery cover 14 while simultaneously electrically separating the battery canister 11 and the battery cover 14.

[0056] [Safety Valve Mechanism]

[0057] The safety valve mechanism 30 is mainly used to release the internal pressure of the battery can 11 by releasing the seal of the battery can 11 as needed when the internal pressure rises. The cause of the internal pressure rise in the battery can 11 is, for example, gas generated by the decomposition reaction of the electrolyte during charging and discharging.

[0058] [Electrode winding]

[0059] In a cylindrical lithium-ion battery 1, a strip-shaped positive electrode 21 and a strip-shaped negative electrode 22 are stacked and wound into a vortex shape, sandwiching a separator 23, and housed in a battery can 11 while immersed in electrolyte. The positive electrode 21 is a component in which a positive electrode active material layer 21B is formed on one or both sides of a positive electrode foil 21A, the material of which is, for example, a metal foil made of aluminum or an aluminum alloy. The negative electrode 22 is a component in which a negative electrode active material layer 22B is formed on one or both sides of a negative electrode foil 22A, the material of which is, for example, a metal foil made of nickel, a nickel alloy, copper, or a copper alloy. The separator 23 is a porous and insulating membrane that electrically insulates the positive electrode 21 and the negative electrode 22 while allowing substances such as ions or electrolyte to move.

[0060] The positive electrode 21 has portions on one and the other main surfaces of the positive electrode foil 21A covered by the positive electrode active material layer 21B, and portions not covered by the positive electrode active material layer 21B. The negative electrode 22 has portions on one and the other main surfaces of the negative electrode foil 22A covered by the negative electrode active material layer 22B, and portions not covered by the negative electrode active material layer 22B. In this specification, the portions not covered by the positive electrode active material layer 21B and the negative electrode active material layer 22B are appropriately referred to as positive electrode active material uncovered portion 21C and negative electrode active material uncovered portion 22C, respectively, and the portions covered by the positive electrode active material layer 21B and the negative electrode active material layer 22B are appropriately referred to as positive electrode active material covered portion 21B and negative electrode active material covered portion 22B, respectively. In the cylindrical battery, the electrode winding body 20 is wound with the positive electrode active material uncovered portion 21C and the negative electrode active material uncovered portion 22C facing opposite directions, overlapping with the separator 23.

[0061] A through hole 26 is provided in the region including the central axis of the electrode winding body 20. The through hole 26 is used as a hole for inserting welding tools, etc., during the assembly process of the lithium-ion battery 1.

[0062] [Cold Collector]

[0063] In conventional lithium-ion batteries, current-extraction leads are welded to one location each at the positive and negative electrodes. However, this results in a high internal resistance, causing the lithium-ion battery to heat up and reach high temperatures during discharge, making it unsuitable for high-rate discharge. Therefore, in the lithium-ion battery 1 of this embodiment, a positive current collector 24 is disposed on one end face 41 of the electrode winding body 20, and a negative current collector 25 is disposed on the other end face 42 of the electrode winding body 20. Furthermore, by welding the positive current collector 24 and the uncovered portion 21C of the positive active material present on the end face 41 at multiple points, and by welding the negative current collector 25 and the uncovered portion 22C of the negative active material present on the end face 42 at multiple points, the internal resistance of the lithium-ion battery 1 is suppressed to a low level, enabling high-rate discharge.

[0064] Figure 3 A and Figure 3 B represents an example of a collector plate. Figure 3 A is the positive current collector 24. Figure 3 B is the negative current collector 25. The positive current collector 24 and the negative current collector 25 are housed in the battery canister 11 (see reference). Figure 2 The positive current collector 24 is made of, for example, a metal plate made of aluminum or aluminum alloy monomers or composite materials, and the negative current collector 25 is made of, for example, a metal plate made of nickel, nickel alloys, copper or copper alloy monomers or composite materials. Figure 3 As shown in Figure A, the positive current collector 24 is shaped as a rectangular strip 32 on a flat, fan-shaped portion 31. A hole 35 is provided near the center of the fan-shaped portion 31, and the position of the hole 35 corresponds to that of the through hole 26.

[0065] Figure 3 The dotted portion A is the insulating portion 32A on the strip 32 where insulating tape is attached or coated with insulating material. The portion lower than the dotted portion in the attached drawing is the connecting portion 32B that connects to the sealing plate, which also serves as an external terminal. It should be noted that in a battery structure where the through-hole 26 does not have a metal center pin (not shown), the strip 32 is less likely to come into contact with the negative electrode potential, therefore the insulating portion 32A may be omitted. In this case, by increasing the width of the positive electrode 21 and the negative electrode 22 by an amount equivalent to the thickness of the insulating portion 32A, the charge / discharge capacity can be increased.

[0066] The negative current collector 25 has a shape that is almost identical to that of the positive current collector 24, but the shape of the strip section is different. Figure 3 The strip portion 34 of the negative current collector plate 24 is shorter than the strip portion 32 of the positive current collector plate and lacks a portion equivalent to the insulating portion 32A. Circular protrusions (projections) 37, indicated by multiple circular markings, are provided on the strip portion 34. During resistance welding, the current concentrates on the protrusions 37, causing them to melt and the strip portion 34 to be welded to the bottom of the battery can 11. Similar to the positive current collector plate 24, a hole 36 is provided near the center of the fan-shaped portion 33 on the negative current collector plate 25, the position of which corresponds to the through hole 26. Since the fan-shaped portions 31 of the positive current collector plate 24 and 33 of the negative current collector plate 25 are fan-shaped, they become part of the covering end faces 41 and 42. By not covering the entire lithium-ion battery 1, the electrolyte can be smoothly penetrated into the electrode winding body 20 during assembly, and the gas generated when the lithium-ion battery 1 is in an abnormally high temperature state or overcharged state can be easily released to the outside of the lithium-ion battery 1.

[0067] [positive electrode]

[0068] The positive electrode active material layer 21B comprises at least a positive electrode material (positive electrode active material) capable of lithium insertion and extraction, and may also comprise a positive electrode binder and a positive electrode conductive agent. The positive electrode material is preferably a lithium-containing composite oxide or a lithium-containing phosphate compound. The lithium-containing composite oxide, for example, has a layered rock salt type or spinel type crystal structure. The lithium-containing phosphate compound, for example, has an olivine type crystal structure.

[0069] The positive electrode binder contains synthetic rubber or polymeric compounds. Synthetic rubbers include styrene-butadiene rubber, fluorinated rubber, and ethylene propylene diene monomer (EPDM) rubber, etc. Polymeric compounds include polyvinylidene fluoride (PVdF) and polyimide, etc.

[0070] The positive electrode conductive agent is a carbon material such as graphite, carbon black, acetylene black, or Ketjen black. Alternatively, the positive electrode conductive agent can also be a metallic material or a conductive polymer.

[0071] [negative electrode]

[0072] To improve adhesion to the negative electrode active material layer 22B, the surface of the negative electrode foil 22A constituting the negative electrode 22 is preferably roughened. The negative electrode active material layer 22B includes at least a negative electrode material (negative electrode active material) capable of lithium insertion and extraction, and may also include a negative electrode binder and a negative electrode conductive agent, etc.

[0073] Anode materials may include carbon materials. These carbon materials can be easily graphitized carbon, difficult-to-graphitize carbon, graphite, low-crystallinity carbon, or amorphous carbon. The shapes of carbon materials can be fibrous, spherical, granular, or flake-like.

[0074] Furthermore, negative electrode materials may include, for example, metallic materials. Examples of metallic materials include Li (lithium), Si (silicon), Sn (tin), Al (aluminum), Zn (zinc), and Ti (titanium). Metallic elements form compounds, mixtures, or alloys with other elements; examples include silicon oxide (SiO₂). x (0<x≤2)), silicon carbide (SiC) or an alloy of carbon and silicon, lithium titanate (LTO).

[0075] [Septum]

[0076] The separator 23 is a porous membrane containing resin, or it can be a laminate of two or more porous membranes. The resin is polypropylene or polyethylene, etc. Alternatively, the separator 23 can have a porous membrane as the substrate layer, with a resin layer on one or both sides. This is because it can improve the adhesion of the separator 23 to the positive electrode 21 and the negative electrode 22, respectively, thereby suppressing the deformation of the electrode winding 20.

[0077] The resin layer contains resins such as PVdF. When forming this resin layer, a solution containing the resin dissolved in an organic solvent is applied to the substrate layer, and then the substrate layer is dried. It should be noted that the substrate layer can also be dried after being immersed in the solution. From the viewpoint of improving heat resistance and battery safety, it is preferable to include inorganic or organic particles in the resin layer. Types of inorganic particles include alumina, aluminum nitride, aluminum hydroxide, magnesium hydroxide, boehmite, talc, silica, mica, etc. Alternatively, a surface layer mainly composed of inorganic particles formed by sputtering, ALD (atomic layer deposition), or similar methods can be used instead of the resin layer.

[0078] Electrolyte

[0079] Electrolytes contain solvents and electrolyte salts, and may also contain additives as needed. Solvents can be non-aqueous solvents such as organic solvents or water. Electrolytes containing non-aqueous solvents are called non-aqueous electrolytes. Non-aqueous solvents include cyclic carbonates, chain carbonates, lactones, chain carboxylic esters, or nitrile (mononitrile), etc.

[0080] Representative examples of electrolyte salts are lithium salts, but salts other than lithium salts may also be included. Lithium salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), and dilithium hexafluorosilicate (Li2SF6). These salts can also be used in combination; from the viewpoint of improving battery performance, a combination of LiPF6 and LiBF4 is preferred. The content of the electrolyte salt is not particularly limited, but it is preferably 0.3 mol / kg to 3 mol / kg relative to the solvent.

[0081] [Details of the electrode winding and the negative electrode]

[0082] Next, the details of the electrode winding body 20 and the negative electrode 22 will be further explained. Figure 4 Figure A is a diagram of the negative electrode 22 before winding, viewed from the front. Figure 4 Figure B is a side view of the negative electrode 22 before winding.

[0083] like Figure 4 As shown in Figure A, the negative electrode 22 of this embodiment has a negative electrode active material covering portion 22B provided on a strip-shaped negative electrode foil 22A. Dots (dot pattern) are attached to the negative electrode active material covering portion 22B. Additionally, the negative electrode 22 has a negative electrode active material non-covering portion 22C. The negative electrode active material non-covering portion 22C includes, for example: a first negative electrode active material non-covering portion 221A extending in the long side direction (X-axis direction) of the negative electrode foil 22A; a second negative electrode active material non-covering portion 221B provided at the end on the winding start side in the long side direction, extending in the width direction (Y-axis direction) of the negative electrode foil 22A; and a third negative electrode active material non-covering portion 221C provided at the end on the winding end side in the long side direction, extending in the width direction (Y-axis direction) of the negative electrode foil 22A. It should be noted that... Figure 4 In A, dashed lines are marked the boundaries between the first negative electrode active material non-covered portion 221A and the second negative electrode active material non-covered portion 221B, and the boundary between the first negative electrode active material non-covered portion 221A and the third negative electrode active material non-covered portion 221C.

[0084] Furthermore, an insulating resin portion 22D is provided between the negative electrode active material covered portion 22B and the first negative electrode active material uncovered portion 221A. The insulating resin portion 22D may include, for example, a resin such as PVdF. The insulating resin portion 22D may also contain inorganic or organic particles. Examples of inorganic particles include any one or more of alumina, aluminum nitride, aluminum hydroxide, magnesium hydroxide, boehmite, talc, silica, and mica.

[0085] like Figure 4 As shown in Figure B, in this embodiment, a negative electrode active material covering portion 22B and an insulating resin portion 22D are provided on both sides of the negative electrode foil 22A. The thickness of the insulating resin portion 22D is less than or equal to the thickness of the negative electrode active material covering portion 22B. It should be noted that the negative electrode active material covering portion 22B and the insulating resin portion 22D may also be provided on one main surface of the negative electrode foil 22A.

[0086] Figure 5 This illustrates an example of the structure before winding of a stacked positive electrode 21, negative electrode 22, and separator 23. The positive electrode 21 has a covering portion 21B that covers the positive electrode active material. Figure 5The insulating layer 101 at the boundary between the sparse portion at the midpoint and the non-covered portion 21C of the positive electrode active material. Figure 5 (The gray area in the image). The length of the insulating layer 101 in the width direction is, for example, about 3 mm. The entire area of ​​the non-covered portion 21C of the positive electrode active material, which is opposite to the negative electrode active material covered portion 22B via the separator 23, is covered by the insulating layer 101. The insulating layer 101 has the effect of reliably preventing internal short circuits in the lithium-ion battery 1 when foreign objects enter between the negative electrode active material covered portion 22B and the non-covered portion 21C of the positive electrode active material. In addition, the insulating layer 101 absorbs the impact when the lithium-ion battery 1 is subjected to an impact, and has the effect of reliably preventing the non-covered portion 21C of the positive electrode active material from bending or short-circuiting with the negative electrode 22.

[0087] Here, as Figure 5 As shown, the length of the non-covered portion 21C of the positive electrode active material in the width direction is set to D5, and the lengths of the non-covered portion 221A of the first negative electrode active material and the insulating resin portion 22D in the width direction are set to D6. In one embodiment, D5 > D6 is preferred, for example, D5 = 7 (mm) and D6 = 4 (mm). When the length of the portion of the non-covered portion 21C of the positive electrode active material protruding from one end of the separator 23 in the width direction is set to D7, and the lengths of the portions of the insulating resin portion 22D and the non-covered portion 221A of the first negative electrode active material protruding from the other end of the separator 23 in the width direction are set to D8, in one embodiment, D7 > D8 is preferred, for example, D7 = 4.5 (mm) and D8 = 3 (mm).

[0088] The positive electrode foil 21A and the non-covered portion 21C of the positive electrode active material are made of, for example, aluminum, while the negative electrode foil 22A and the non-covered portion 22C of the negative electrode active material are made of, for example, copper. Thus, the non-covered portion 21C of the positive electrode active material is generally softer (lower Young's modulus) than the non-covered portion 22C of the negative electrode active material. Therefore, in one embodiment, it is more preferable that D5 > D6 and D7 > D8, in which case, when the non-covered portion 21C of the positive electrode active material and the non-covered portion 22C of the negative electrode active material are bent simultaneously from both electrode sides with the same pressure, the height measured from the front end of the diaphragm 23 of the bent portion sometimes becomes approximately the same in the positive electrode 21 and the negative electrode 22. At this time, since the non-covered portion 21C of the positive electrode active material is bent and moderately overlaps, the bonding of the non-covered portion 21C of the positive electrode active material and the positive electrode current collector 24 by laser welding can be easily performed in the manufacturing process of the lithium-ion battery 1 (details will be described later). Furthermore, since the non-covered portion 22C of the negative electrode active material is bent and moderately overlapped, the non-covered portion 22C of the negative electrode active material and the negative electrode current collector 25 can be easily joined by laser welding during the manufacturing process of the lithium-ion battery 1.

[0089] [Methods for manufacturing lithium-ion batteries]

[0090] Next, refer to Figure 6 A to Figure 6 F. A method for manufacturing a lithium-ion battery 1 according to one embodiment will be described. First, a positive electrode active material is coated on the surface of a strip-shaped positive electrode foil 21A, which serves as a positive electrode active material covering portion 21B. A negative electrode active material is coated on the surface of a strip-shaped negative electrode foil 22A, which serves as a negative electrode active material covering portion 22B. At this time, a positive electrode active material non-covered portion 21C without positive electrode active material coating is provided at one end of the positive electrode foil 21A in the width direction, and a negative electrode active material non-covered portion 22C without negative electrode active material coating (first negative electrode active material non-covered portion 221A, second negative electrode active material non-covered portion 221B, and third negative electrode active material non-covered portion 221C) without negative electrode active material coating is provided on the negative electrode foil 22A. In addition, when providing the negative electrode active material covering portion 22B, an insulating resin portion 22D is provided by coating with resin. Furthermore, slits were made in a portion of both the non-covered portion 21C of the positive electrode active material and the non-covered portion 22C of the negative electrode active material, corresponding to the starting point of winding. Next, the positive electrode 21 and the negative electrode 22 underwent drying processes. Then, the non-covered portions 21C and 22C of the positive electrode active material were overlapped across the separator 23 with their orientations opposite, and wound into a vortex shape such that a through-hole 26 could be formed at the central axis, and the slits were positioned near the central axis, thus creating a vortex. Figure 6 Electrode winding body 20, like A.

[0091] Next, as Figure 6 As shown in B, a groove 43 is formed on a portion of end faces 41 and 42 by pressing the end of a thin plate (e.g., 0.5 mm thick) perpendicularly relative to end faces 41 and 42. The groove 43 extends radially from the through hole 26 by this method. Figure 6 The number and configuration of slots 43 shown in B are just one example. Then, as Figure 6 As shown in Figure C, the same pressure is applied simultaneously from both poles in a direction approximately perpendicular to end faces 41 and 42, bending the uncovered portions 21C and 22C of the positive and negative active materials, thus forming flat surfaces 41 and 42. At this time, a load is applied to the surface of a flat plate or similar material by bending the uncovered portions of the active materials on end faces 41 and 42 towards the central axis. Subsequently, the fan-shaped portion 31 of the positive current collector plate 24 is laser-welded to end face 41, and the fan-shaped portion 33 of the negative current collector plate 25 is laser-welded to end face 42, thus achieving a joint.

[0092] Next, as Figure 6As shown in Figure D, the strip portion 32 of the positive electrode current collector 24 and the strip portion 34 of the negative electrode current collector 25 are bent, an insulating plate 12 is attached to the positive electrode current collector 24, and an insulating plate 13 is attached to the negative electrode current collector 25. The electrode winding body 20 assembled as described above is then inserted. Figure 6 As shown in Figure E, the bottom of battery can 11 is welded. After the electrolyte is injected into battery can 11, as... Figure 6 As shown in Figure F, the battery is sealed with gasket 15 and battery cover 14. The lithium-ion battery 1 was manufactured as described above.

[0093] It should be noted that insulating plates 12 and 13 can also be insulating tapes. Furthermore, the joining method can be any method other than laser welding. Additionally, after bending the non-covered portions 21C and 22C of the positive and negative active materials, the groove 43 remains within the flat surface. The portion without the groove 43 joins with the positive current collector 24 or the negative current collector 25, but the groove 43 can also join with a portion of the positive or negative current collector 24 or the negative current collector 25.

[0094] It should be noted that the term "flat surface" in this specification includes not only a completely flat surface, but also a surface with some unevenness or surface roughness to the extent that a specified portion (e.g., the first negative electrode active material non-covered portion 21C) and the positive electrode current collector 24, and a specified portion (e.g., the first negative electrode active material non-covered portion 221A) and the negative electrode current collector 25 can be joined.

[0095] [Effects achievable through this implementation method]

[0096] The following effects can be obtained through this embodiment, for example.

[0097] In this embodiment, an insulating resin portion 22D is provided on the negative electrode foil 22A. As a result, the negative electrode active material covering portion 22B interacts (extrudes) with the insulating resin portion 22D, thereby increasing the boundary between the negative electrode active material covering portion 22B and the insulating resin portion 22D. Figure 5 The linear progression of the boundary 22E in the long side direction.

[0098] As described above, the straight-line advancement of the boundary 22E could not be guaranteed due to necking or unevenness of the boundary 22E. Therefore, in order to reliably align the positive electrode active material covering portion 21B and the negative electrode active material covering portion 22B, the distance D10 between the end of the positive electrode active material covering portion 21B and the end of the negative electrode active material covering portion 22B needs to be (refer to...) Figure 5The margin is set large. As a result, the area of ​​the positive electrode active material covering portion 21B is reduced, and the battery capacity may decrease. However, in this embodiment, since the linearity of the boundary 22E can be improved, the distance D10 can be minimized. As a result, the area of ​​the positive electrode active material covering portion 21B can be increased, and thus the battery capacity of the lithium-ion battery 1 can be increased.

[0099] During the manufacturing of lithium-ion batteries, when the end of a thin flat plate (e.g., 0.5 mm thick) is pressed perpendicularly relative to end faces 41 and 42, (the process involves...) Figure 6 During the process shown in step B), at the winding start side of the electrode winding body 20 (the end side in the long side direction of the positive or negative electrode at the innermost circumference of the electrode winding body 20), the negative electrode active material sometimes peels off from the negative electrode active material covering portion 22B. This peeling can be considered to be caused by the stress generated when pressing the end face 42. The peeled negative electrode active material penetrates into the interior of the electrode winding body 20, which may cause an internal short circuit. In this embodiment, since the second negative electrode active material non-covering portion 221B and the third negative electrode active material non-covering portion 221C are provided, the peeling of the negative electrode active material can be prevented, and the occurrence of an internal short circuit can be prevented. This effect can also be obtained by providing only one of the second negative electrode active material non-covering portion 221B and the third negative electrode active material non-covering portion 221C, but it is more preferable to provide both.

[0100] On the winding termination side of the electrode winding 20, the negative electrode 22 may have a region of negative active material non-covered portion 22C on the main surface of the side not facing the positive active material covering portion 21B. This is because it can be considered that even if there is a negative active material covering portion 22B on the main surface not facing the positive active material covering portion 21B, its contribution to charging and discharging is low. The region of negative active material non-covered portion 22C is preferably more than 3 / 4 turn and less than 5 / 4 turn of the electrode winding 20. At this time, since there is no negative active material covering portion 22B that has a low contribution to charging and discharging, the initial capacity can be improved relative to the same volume of the electrode winding 20.

[0101] In this embodiment, the electrode winding body 20 is wound with the positive active material uncovered portion 21C and the negative active material uncovered portion 22C facing opposite directions. Therefore, the positive active material uncovered portion 21C is concentrated on end face 41, and the negative active material uncovered portion 22C is concentrated on end face 42 of the electrode winding body 20. The positive and negative active material uncovered portions 21C and 22C are bent, making end faces 41 and 42 flat. The bending direction is from the outer edges 27 and 28 of end faces 41 and 42 toward the through hole 26, and adjacent peripheral active material uncovered portions overlap and bend during the winding process. Because end face 41 is flat, good contact between the positive active material uncovered portion 21C and the positive current collector 24 is ensured, and good contact between the negative active material uncovered portion 22C and the negative current collector 25 is also ensured. In addition, by bending the end faces 41 and 42 to make them flat, the resistance of the lithium-ion battery 1 can be reduced.

[0102] Furthermore, although it is believed that bending the non-covered portions 21C and 22C of the positive and negative active materials can make the end faces 41 and 42 appear flat at first glance, if no processing is performed before bending, wrinkles or gaps (voids, spaces) will be generated on the end faces 41 and 42 during bending, and the end faces 41 and 42 may not become flat. Here, "wrinkles" or "gaps" refer to deviations in the bent non-covered portions 21C and 22C of the positive and negative active materials, resulting in portions of the end faces 41 and 42 that are not flat. In this embodiment, grooves 43 are pre-formed along the radial direction from the through hole 26 on the end faces 41 and 42 respectively. By forming grooves 43, the generation of wrinkles or gaps can be suppressed, and the end faces 41 and 42 can be made flatter. It should be noted that either the non-covered portion 21C of the positive active material or the non-covered portion 22C of the negative active material can be bent, but it is preferable to bend both.

[0103] In this embodiment, cuts are provided on the non-covered portion 21C of the positive electrode active material at the beginning of the winding of the positive electrode 21 and the non-covered portion 22C of the negative electrode active material at the beginning of the winding of the negative electrode 22, located near the through hole 26. This prevents the through hole 26 from being blocked when the non-covered portions 21C and 22C of the positive and negative electrode active materials bend toward it.

[0104] Example

[0105] The present invention will now be specifically described using examples and comparative examples. In these examples and comparative examples, a lithium-ion battery 1 manufactured as described above was used, and the occurrence rate of internal short circuits caused by the shedding of negative electrode active material, the deviation in the length of the negative electrode active material covering portion 22B in the width direction, the length in the width direction of the positive electrode active material covering portion 21B opposite to the negative electrode active material covering portion 22B, and the rated capacity of the lithium-ion battery 1 were evaluated. It should be noted that the present invention is not limited to the examples described below.

[0106] In all the following embodiments and comparative examples, the battery size is set to 21700 (diameter 21 mm, height 70 mm), the length of the negative electrode active material covering portion 22B in the width direction is set to 62 mm, and the length of the separator 23 in the width direction is set to 64 mm. The separator 23 is overlapped to cover the entire range of the positive electrode active material covering portion 21B and the negative electrode active material covering portion 22B, and the length of the positive electrode active material uncovered portion 21C in the width direction is set to 7 mm. In addition, the number of slots 43 is set to 8, and they are arranged in a substantially equiangularly spaced manner.

[0107] Figure 4 , Figures 7-9 These are diagrams showing the negative electrode 22 corresponding to Example 1 and Comparative Examples 1 to 3.

[0108] [Example 1]

[0109] The lithium-ion battery 1 was manufactured through the above-described process. At this point, as... Figure 4 As shown, a negative electrode active material covered portion 22B and a negative electrode active material uncovered portion 22C are provided on both sides of the negative electrode foil 22A. By cutting the negative electrode foil 22A at the portion of the negative electrode active material uncovered portion 22C, a first negative electrode active material uncovered portion 221A, a second negative electrode active material uncovered portion 221B, and a third negative electrode active material uncovered portion 221C are formed. Furthermore, an insulating resin portion 22D is provided between the negative electrode active material covered portion 22B and the first negative electrode active material uncovered portion 221A. The length of the insulating resin portion 22D in the width direction is 3 (mm).

[0110] [Comparative Example 1]

[0111] like Figure 7 As shown, a negative electrode active material covered portion 22B and a first negative electrode active material uncovered portion 221A are provided on both sides of the negative electrode foil 22A. The second negative electrode active material uncovered portion 221B, the third negative electrode active material uncovered portion 221C, and the insulating resin portion 22D are not provided. Otherwise, a lithium-ion battery 1 was manufactured in the same manner as in Example 1.

[0112] [Comparative Example 2]

[0113] like Figure 8 As shown, by providing a negative electrode active material covered portion 22B and a negative electrode active material uncovered portion 22C on both sides of the negative electrode foil 22A, and cutting the negative electrode foil 22A at the portion of the negative electrode active material uncovered portion 22C, a first negative electrode active material uncovered portion 221A, a second negative electrode active material uncovered portion 221B, and a third negative electrode active material uncovered portion 221C are formed. The insulating resin portion 22D is not provided. Otherwise, the lithium-ion battery 1 is manufactured in the same manner as in Example 1.

[0114] [Comparative Example 3]

[0115] like Figure 9 As shown, a negative electrode active material covering portion 22B, a first negative electrode active material uncovered portion 221A, and an insulating resin portion 22D are provided on both sides of the negative electrode foil 22A. The second negative electrode active material uncovered portion 221B and the third negative electrode active material uncovered portion 221C are not provided. Otherwise, a lithium-ion battery 1 was manufactured in the same manner as in Example 1. The insulating resin portion 22D has a length of 3 (mm) in the width direction.

[0116] [evaluate]

[0117] The lithium-ion batteries 1 in the above examples were assembled and charged to 4.20V. After being stored at 25±3℃ for 5 days, the voltage of the stored lithium-ion batteries 1 was measured. The number of batteries whose voltage dropped by more than 50mV (voltage below 4.15V) was counted, and this proportion was taken as the internal short circuit rate.

[0118] In addition, the rated capacity (mAh) of lithium-ion battery 1 was measured.

[0119] Regarding the deviation in the length of the negative electrode active material covering portion 22B in the width direction, 200 measurement points are set every 100 mm on a main surface from one side to the other in the long side direction of the negative electrode foil 22A. The length of the negative electrode active material covering portion 22B in the width direction at each measurement point is calculated, and the deviation σ is calculated based on the result. Here, σ refers to the standard deviation.

[0120] The length of the positive electrode active material covering portion 21B in the width direction is set such that, after confirming the deviation σ of the negative electrode active material covering portion 22B, the width of the positive electrode active material covering portion can be maintained at a width greater than the width of the positive electrode active material covering portion.

[0121] One hundred lithium-ion batteries 1 with the structures of Example 1 and Comparative Examples 1 to 3 were fabricated and evaluated. The results are shown in Table 1.

[0122] [Table 1]

[0123]

[0124] In Examples 1 and 3, the deviation σ of the width dimension of the negative electrode active material covering portion 22B was 0.07. In contrast, in Comparative Examples 1 and 2, the deviation σ of the width dimension of the negative electrode active material covering portion 22B increased to 0.19 to 0.21. This can be attributed to the fact that by providing the insulating resin portion 22D, the negative electrode active material covering portion 22B and the insulating resin portion 22D interact, improving the straight-line advancement of the end of the negative electrode active material covering portion 22B, thereby reducing the deviation σ. Furthermore, in Examples 1 and 3, by reducing the deviation σ, the length of the positive electrode active material covering portion 21B in the width direction can be increased by 0.4 mm compared to Comparative Examples 1 and 2, resulting in an increase in battery capacity of 25 mAh.

[0125] Furthermore, the internal short-circuit incidence rate was 0% in Examples 1 and 2, while it was 4-6% in Comparative Examples 1 and 3, which is considered high. This can be attributed to the fact that in the lithium-ion batteries 1 of Comparative Examples 1 and 3, the second negative electrode active material non-covered portion 221B and the third negative electrode active material non-covered portion 221C were not provided at the winding start-end and winding end-end of the negative electrode foil 22A. Therefore, the negative electrode active material peeled off and detached from the portion where the negative electrode foil 22A was cut, and the detached negative electrode active material penetrated into the electrode winding body 20, causing an internal short circuit. In contrast, in Examples 1 and 2, which were provided with the second negative electrode active material non-covered portion 221B and the third negative electrode active material non-covered portion 221C, no peeling or detachment of the negative electrode active material occurred, and no internal short circuit occurred.

[0126] In summary, the structure corresponding to Example 1 can be considered the preferred structure of lithium-ion battery 1.

[0127] <Variation Example>

[0128] The above describes one embodiment of the present invention in detail, but the content of the present invention is not limited to the above embodiment, and various modifications can be made based on the technical concept of the present invention.

[0129] In the embodiments and comparative examples, the number of slots 43 is 8, but it can also be any other number. The battery size is set to 21700 (diameter 21mm, height 70mm), but it can also be 18650 (diameter 18mm, height 65mm) or other sizes.

[0130] The positive current collector 24 and the negative current collector 25 have fan-shaped portions 31 and 33, but they can also be other shapes.

[0131] As long as it does not depart from the spirit of the invention, the present invention can also be applied to other batteries besides lithium-ion batteries, and batteries other than cylindrical shapes (e.g., laminated batteries, prismatic batteries, coin-shaped batteries, button batteries). In this case, the shape of the "end face of the electrode winding" can be not only cylindrical, but also elliptical or flat, etc.

[0132] <Application Examples>

[0133] (1) Battery pack

[0134] Figure 10 This is a block diagram illustrating a circuit structure example when the secondary battery according to an embodiment or example of the present invention is applied to a battery pack 300. The battery pack 300 includes a battery assembly 301, a switch unit 304 including a charging control switch 302a and a discharging control switch 303a, a current sensing resistor 307, a temperature sensing element 308, and a control unit 310. The control unit 310 controls each device, thereby enabling charging and discharging control in case of abnormal heat generation, or calculating and correcting the remaining capacity of the battery pack 300. The positive terminal 321 and negative terminal 322 of the battery pack 300 are connected to a charger or electronic device for charging and discharging.

[0135] The battery pack 301 is constructed by connecting multiple secondary batteries 301a in series and / or parallel. Figure 10 The diagram illustrates, as an example, a configuration where six secondary batteries 301a are connected in a 2-parallel, 3-series (2P3S) configuration. The secondary battery of this invention can be applied to secondary battery 301a.

[0136] Temperature detection unit 318 is connected to temperature detection element 308 (e.g., thermistor) to measure the temperature of battery pack 301 or battery stack 300, and provides the measured temperature to control unit 310. Voltage detection unit 311 measures the voltage of battery pack 301 and each secondary battery 301a constituting battery pack 301, performs A / D conversion on the measured voltage, and provides it to control unit 310. Current detection unit 313 measures the current using current detection resistor 307, and provides the measured current to control unit 310.

[0137] The switch control unit 314 controls the charging control switch 302a and the discharging control switch 303a of the switch unit 304 based on the voltage and current input from the voltage detection unit 311 and the current measurement unit 313. When the secondary battery 301a reaches an overcharge detection voltage (e.g., 4.20V ± 0.05V) or an over-discharge detection voltage (2.4V ± 0.1V) or below, the switch control unit 314 sends a shut-off control signal to the switch unit 304, thereby preventing overcharging or over-discharging.

[0138] After the charging control switch 302a or the discharging control switch 303a is turned off, charging or discharging can be performed solely through diode 302b or diode 303b. These charging and discharging switches can use semiconductor switches such as MOSFETs. It should be noted that... Figure 10 In the middle, the switch part 304 is provided on the + side, but it can also be provided on the - side.

[0139] The memory 317 is composed of RAM or ROM, and can store and rewrite the values ​​of battery characteristics, full charge capacity, remaining capacity, etc. calculated by the control unit 310.

[0140] (2) Electronic devices

[0141] The secondary batteries described in the above-described embodiments or examples of the present invention can be installed in electronic devices, electric transportation equipment, energy storage devices, and other equipment to supply power.

[0142] Examples of electronic devices include laptops, smartphones, tablets, PDAs (portable information terminals), mobile phones, wearable devices, digital still cameras, e-books, music players, game consoles, hearing aids, power tools, televisions, lighting equipment, toys, medical devices, and robots. Additionally, electric transportation equipment, energy storage devices, power tools, and electric unmanned aerial vehicles (UAVs) described later can also be broadly included in the category of electronic devices.

[0143] Examples of electric transportation equipment include electric vehicles (including hybrid vehicles), electric motorcycles, electric-assisted bicycles, electric buses, electric trolleys, automated guided vehicles (AGVs), and railway vehicles. Additionally, electric passenger aircraft or electric unmanned aerial vehicles (UAVs) for transportation are also included. The secondary battery involved in this invention can be used not only as a power source for driving these devices, but also as an auxiliary power source, a power source for energy regeneration, etc.

[0144] As energy storage devices, examples include commercial or residential energy storage modules, and power storage devices for use in buildings such as residences, buildings, and offices, or for power generation equipment.

[0145] (3) Power tools

[0146] Reference Figure 11 A brief description will be given of an electric screwdriver as an example of an electric tool to which the present invention can be applied. The electric screwdriver 431 is equipped with a motor 433 that transmits rotational power to a shaft 434 and a user-operated trigger switch 432. A battery pack 430 and a motor control unit 435 are housed within the lower housing of the handle of the electric screwdriver 431. The battery pack 430 is either built into the electric screwdriver 431 or can be freely installed and removed. The rechargeable battery of the present invention can be used in the battery constituting the battery pack 430.

[0147] The battery pack 430 and the motor control unit 435 may each be equipped with a microcomputer (not shown), which can communicate with each other regarding the charging and discharging information of the battery pack 430. The motor control unit 435 can control the operation of the motor 433 and cut off the power supply to the motor 433 in case of abnormalities such as over-discharge.

[0148] (4) Energy storage system for electric vehicles

[0149] As an example of applying the present invention to an energy storage system for electric vehicles, Figure 12 The diagram schematically illustrates a structural example of a hybrid vehicle (HV) employing a series hybrid system. A series hybrid system is a vehicle that uses electricity generated by a generator that powers an engine, or electricity temporarily stored in a battery, to drive via an electric drive conversion device.

[0150] The hybrid vehicle 600 includes an engine 601, a generator 602, an electric drive power conversion device (DC motor or AC motor, hereinafter referred to as "motor 603"), drive wheels 604a and 604b, wheels 605a and 605b, a battery 608, a vehicle control device 609, various sensors 610, and a charging port 611. The battery 608 can be a secondary battery of the present invention or an energy storage module equipped with multiple secondary batteries of the present invention.

[0151] The motor 603 operates using electricity from the battery 608, and the rotational force of the motor 603 is transmitted to the drive wheels 604a and 604b. The electricity generated by the generator 602 from the rotational force produced by the engine 601 is stored in the battery 608. Various sensors 610 control the engine speed or the opening of a throttle valve (not shown) via the vehicle control unit 609.

[0152] When the hybrid vehicle 600 is decelerated by a braking mechanism (not shown), the resistance during deceleration is applied as a rotational force to the motor 603, and the regenerative electricity generated by this rotational force is stored in the battery 608. Furthermore, the battery 608 can be charged by connecting to an external power source via the charging port 611 of the hybrid vehicle 600. Such an HV vehicle is called a plug-in hybrid electric vehicle (PHV or PHEV).

[0153] It should be noted that the secondary battery involved in this invention can also be applied to miniaturized primary batteries and used as a power source for tire pressure monitoring systems (TPMS) built into wheels 604 and 605.

[0154] The above explanation uses a series hybrid vehicle as an example, but the invention can also be applied to hybrid vehicles that use a parallel connection of the engine and motor, or a combination of series and parallel connections. Furthermore, the invention can also be applied to electric vehicles (EVs or BEVs) and fuel cell vehicles (FCVs) that operate solely on a drive motor without an engine.

[0155] Explanation of reference numerals in the attached figures

[0156] 1: Lithium-ion battery; 12: Insulating plate; 21: Positive electrode; 21A: Positive electrode foil; 21B: Positive electrode active material layer; 21C: Positive electrode active material uncovered portion; 22: Negative electrode; 22A: Negative electrode foil; 22B: Negative electrode active material layer; 22C: Negative electrode active material uncovered portion; 23: Separator; 22D: Insulating resin portion; 24: Positive electrode current collector; 25: Negative electrode current collector; 26: Through hole; 27, 28: Outer edge portion; 41, 42: End face; 43: Groove; 221A: First negative electrode active material uncovered portion; 221B: Second negative electrode active material uncovered portion; 221C: Third negative electrode active material uncovered portion.

Claims

1. A secondary battery, comprising an electrode winding body, a positive electrode current collector, and a negative electrode current collector housed in a battery can, wherein the electrode winding body is formed by stacking strip-shaped positive and strip-shaped negative electrodes with a separator in between. The positive electrode has: a positive electrode active material covered portion, wherein a layer of positive electrode active material is covered on a strip-shaped positive electrode foil; and a positive electrode active material uncovered portion. The negative electrode comprises: a negative electrode active material covering portion, wherein a layer of negative electrode active material is covered on a strip-shaped negative electrode foil; a first negative electrode active material non-covering portion, extending in the long side direction of the negative electrode foil; a second negative electrode active material non-covering portion, disposed at the end on the winding start side in the long side direction; and an insulating resin portion, disposed between the negative electrode active material covering portion and the first negative electrode active material non-covering portion. The non-covered portion of the positive electrode active material is bonded to the positive electrode current collector at one end of the electrode winding body. The non-covered portion of the first negative electrode active material is joined to the negative electrode current collector on the other side of the end of the electrode winding body. The electrode winding body has: a flat surface formed by bending and coinciding with the central axis of the electrode winding body, consisting of either or both of the uncovered portion of the positive electrode active material and the uncovered portion of the first negative electrode active material; and a groove formed on the flat surface. The negative electrode also has a third negative electrode active material non-covered portion at the end on the winding termination side in the long side direction.

2. The secondary battery according to claim 1, wherein, The thickness of the insulating resin portion is less than or equal to the thickness of the negative electrode active material covering portion.

3. An electronic device having the secondary battery as described in claim 1 or 2.

4. An electric tool having a secondary battery as described in claim 1 or 2.

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