Secondary battery, electronic device, and power tool

Abstract

Insertion of a welding rod is inhibited from being poor, and the like. A secondary battery in which an electrode roll body in which a strip-shaped positive electrode and a strip-shaped negative electrode are stacked with a separator interposed, a positive electrode current collecting plate, and a negative electrode current collecting plate are housed in a battery can, the electrode roll body has a flat surface and a groove formed in the flat surface, the flat surface is formed by bending either one or both of a positive active material non-covered portion and a negative active material non-covered portion toward a central axis of a structure after winding and overlapping each other, in the case of observing in cross section with a cross section obtained by cutting with a plane passing through the central axis, a hole portion formed at a portion obtained by bending has a first diameter and a second diameter which are substantially parallel to a stacking direction, the first diameter is located at a position closer to an inside of the electrode roll body than the second diameter, and the diameter substantially continuously increases from the first diameter to the second diameter.

Description

Technical Field

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

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

[0003] Furthermore, lithium-ion batteries with wound electrode structures typically have a through-hole at the center of the wound electrode body. For example, Patent Document 1 describes a non-aqueous secondary battery in which the central through-hole is enlarged. Patent Document 2 describes an electrochemical element (battery) in which the exposed portion of the current collector is bent toward the central through-hole.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2008-218133

[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 diaphragm is enlarged. There is a concern that the diaphragm may peel off when its diameter is enlarged. In addition, in the technology described in Patent Document 2, the through hole is blocked by the exposed portion of the bent current collector, or the diameter of the central through hole is unnecessarily reduced, raising concerns that it may be impossible to insert the welding rod into the through hole.

[0010] Therefore, one of the objects of the present invention is to provide a novel and useful secondary battery that solves the above-mentioned defects, an electronic device using the secondary battery, and a power tool.

[0011] Technical solutions for solving technical problems

[0012] This invention relates to a secondary battery in which an electrode winding body, a positive electrode current collector, and a negative electrode current collector are housed in a battery can. Within the electrode winding body, strip-shaped positive and strip-shaped negative electrodes are stacked separated by a separator.

[0013] The positive electrode has a positive active material covered portion and a positive active material uncovered portion on a strip-shaped positive electrode foil.

[0014] The negative electrode has a negative active material covered portion covered with a negative active material layer on a strip-shaped negative electrode foil, and a negative active material uncovered portion extending at least along the long side direction of the negative electrode foil.

[0015] The non-covered 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.

[0016] The non-covered portion of the negative electrode active material is joined to the negative electrode current collector on the other side of the end of the electrode winding body.

[0017] The electrode winding has a flat surface and a groove formed on the flat surface. The flat surface is formed by bending one or both of the uncovered portions of the positive electrode active material and the uncovered portions of the negative electrode active material toward the central axis of the wound structure and overlapping them.

[0018] When observing a cross-section obtained by cutting with a plane passing through the central axis,

[0019] The hole formed in the portion obtained by bending has a first diameter and a second diameter that are approximately parallel to the direction of stacking.

[0020] The first diameter is located on the inner side of the electrode winding body, which is closer to the second diameter.

[0021] From the first diameter to the second diameter, the diameter increases roughly continuously.

[0022] Invention Effects

[0023] According to at least one embodiment of the present invention, it is possible to prevent defects such as peeling of the diaphragm or other components located on the periphery of the through hole of the electrode winding body, or the inability to insert the welding rod into the through hole. It should be noted that the effects illustrated in this specification are not intended to limit the scope of the present invention. Attached Figure Description

[0024] Figure 1 This is a cross-sectional view of a lithium-ion battery according to one embodiment.

[0025] Figure 2 A and Figure 2 B is a diagram used to illustrate the positive electrode involved in one embodiment.

[0026] Figure 3 A and Figure 3 B is a diagram used to illustrate the negative electrode involved in one embodiment.

[0027] Figure 4 This is a diagram showing the positive electrode, negative electrode, and diaphragm before winding.

[0028] Figure 5 A is a top view of the positive current collector according to one embodiment. Figure 5B is a top view of the negative current collector according to one embodiment.

[0029] Figure 6 A to Figure 6 F is a diagram illustrating the assembly process of a lithium-ion battery according to one embodiment.

[0030] Figure 7 A and Figure 7 Figure B is a diagram illustrating an example of the configuration of a slot-forming fixture according to one embodiment.

[0031] Figure 8 This is a partially enlarged view of a slot-forming fixture according to one embodiment.

[0032] Figure 9 A and Figure 9 Figure B is a diagram illustrating an example of the configuration of a flat surface forming fixture according to one embodiment.

[0033] Figure 10 This is a partially enlarged cross-sectional view of a lithium-ion battery according to one embodiment.

[0034] Figure 11 It is a diagram used to illustrate density.

[0035] Figure 12 This is a diagram used to illustrate Comparative Example 1.

[0036] Figure 13 This is a diagram used to illustrate Comparative Example 2.

[0037] Figure 14 This is a connection diagram illustrating a battery pack as an application example of the present invention.

[0038] Figure 15 This is a connection diagram illustrating an application example of the present invention using an electric tool.

[0039] Figure 16 This is a connection diagram used to illustrate an electric vehicle as an application example of the present invention. Detailed Implementation

[0040] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the descriptions will be presented in the following order.

[0041] <One Implementation Method>

[0042] <Variation Example>

[0043] <Application Examples>

[0044] 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, some components in the figures may sometimes be enlarged, emphasized, or reduced, or some illustrations may be simplified.

[0045] <One Implementation Method>

[0046] [Example of lithium-ion battery structure]

[0047] In one embodiment of the present invention, a cylindrical lithium-ion battery will be used as an example of a secondary battery. (Refer to...) Figures 1 to 5 An example of the configuration of a lithium-ion battery (lithium-ion battery 1) according to one embodiment will be described. Figure 1 This is a schematic cross-sectional view of lithium-ion battery 1. For example, as shown... Figure 1 As shown, the lithium-ion battery 1 is a cylindrical lithium-ion battery 1 in which the electrode winding body 20 is housed inside the battery can 11. It should be noted that, in the following description, unless otherwise specified, the orientation will be appropriately referred to as... Figure 1 The horizontal direction when the paper is in contact with the surface is called the X-axis, the depth direction is called the Y-axis, and the vertical direction (the central axis of lithium-ion battery 1, also appropriately called the winding axis) is called the vertical direction. Figure 1 The direction of extension of the axis (shown by a single-dot dashed line) is called the Z-axis direction.

[0048] The lithium-ion battery 1 generally has a cylindrical battery can 11, and inside the battery can 11 are a pair of insulating plates 12, 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.

[0049] (Battery can)

[0050] The battery can 11 is primarily a component for housing the electrode winding 20. The battery can 11 is, for example, a cylindrical container with one end open and the other end blocked. That is, the battery can 11 has an open end (open end 11N). The battery can 11 may contain, for example, any one or more of the following metallic materials: iron, aluminum, and their alloys. The surface of the battery can 11 may also be plated with, for example, any one or more of the following metallic materials: nickel.

[0051] (Insulating board)

[0052] Insulating plates 12 and 13 have a central axis relative to the electrode winding body 20 (passing approximately at the center of the end face of the electrode winding body 20 and perpendicular to the axis of the central axis). Figure 1 A circular plate with a surface approximately perpendicular to the Z-axis (parallel to the direction of the Z-axis). Additionally, insulating plates 12 and 13 are configured, for example, to sandwich the electrode winding 20 between each other.

[0053] (Riveted structure)

[0054] At the open end face 11N of the battery can 11, a battery cover 14 and a safety valve mechanism 30 are riveted together with a gasket 15, forming a riveting structure 11R (curled structure). Thus, the battery can 11 is sealed with the electrode winding body 20 and the like housed inside the battery can 11.

[0055] (Battery cover)

[0056] The battery cover 14 is primarily a component that blocks 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.

[0057] (washer)

[0058] The gasket 15 is a component that seals the gap between the bent portion 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 may be applied to the surface of the gasket 15.

[0059] 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 particularly preferred as the insulating material. This is because it allows for the simultaneous electrical separation of the battery canister 11 and the battery cover 14 while simultaneously ensuring a thorough seal between the bent portion 11P and the battery cover 14.

[0060] (Safety valve mechanism)

[0061] The safety valve mechanism 30 primarily releases the internal pressure of the battery can 11 by releasing the sealed state of the battery can 11 as needed when the internal pressure rises. The increase in internal pressure of the battery can 11 may be caused by gases generated during the decomposition reaction of the electrolyte during charging and discharging.

[0062] (Electrode winding body)

[0063] 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 separated by a separator 23, and housed in a battery can 11 while being permeated with electrolyte. The positive electrode 21 is formed by forming a positive electrode active material layer 21B 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 formed by forming a negative electrode active material layer 22B 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 and electrolyte to move.

[0064] Figure 2 Figure A is a diagram of the positive electrode 21 before winding, viewed from the front. Figure 2 B is viewed from the side. Figure 2 The diagram shows the positive electrode 21 of electrode A. The positive electrode 21 has portions (marked with dots) covered by the positive active material layer 21B on one main surface and the other main surface of the positive electrode foil 21A, and portions not covered by the positive active material layer 21B, namely, the positive active material uncovered portion 21C. It should be noted that in the following description, the portion covered by the positive active material layer 21B is appropriately referred to as the positive active material covered portion 21B. Alternatively, the positive active material covered portion 21B may be provided on one main surface of the positive electrode foil 21A.

[0065] Figure 3 Figure A is a diagram of the negative electrode 22 before winding, viewed from the front. Figure 3 B is viewed from the side. Figure 3 The diagram shows the negative electrode 22 of electrode A. The negative electrode 22 has portions (marked with dots) covered by the negative electrode active material layer 22B on one main surface and the other main surface of the negative electrode foil 22A, and portions not covered by the negative electrode active material layer 22B, namely, the negative electrode active material uncovered portion 22C. It should be noted that, in the following description, the portion covered by the negative electrode active material layer 22B is appropriately referred to as the negative electrode active material covered portion 22B. Alternatively, the negative electrode active material covered portion 22B may be provided on one main surface of the negative electrode foil 22A.

[0066] like Figure 3 As shown in A, the non-covered portion 22C of the negative electrode active material has, for example, a portion along the long side direction of the negative electrode 22 ( Figure 3 The first non-covered portion 221A of the negative electrode active material extends along the X-axis direction of the negative electrode 22, and is located on the short side direction of the negative electrode 22 at the beginning of the winding of the negative electrode 22. Figure 3The second negative electrode active material non-covered portion 221B extends along the Y-axis direction (also appropriately referred to as the width direction) and along the short side direction of the negative electrode 22 at the winding termination side of the negative electrode 22. Figure 3 The third negative electrode active material uncovered portion 221C extends along the Y-axis direction. It should be noted that... Figure 3 In A, dashed lines are marked at 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 between the first negative electrode active material non-covered portion 221A and the third negative electrode active material non-covered portion 221C.

[0067] In the cylindrical lithium-ion battery 1 of this embodiment, the electrode winding body 20 is formed by overlapping and winding the positive electrode 21 and the negative electrode 22 with the separator 23 in such a way that the positive electrode active material non-covered portion 21C and the first negative electrode active material non-covered portion 221A are facing opposite directions to each other.

[0068] A through hole 26 is provided in the region including the central axis of the electrode winding body 20. Specifically, the through hole 26 is a hole formed approximately at the center of the stack formed by the positive electrode 21, the negative electrode 22, and the separator 23. The through hole 26 is used as a hole for inserting rod-shaped welding tools (hereinafter appropriately referred to as welding rods) during the assembly process of the lithium-ion battery 1.

[0069] The details of the electrode winding 20 are explained below. Figure 4 The diagram shows an example of the structure before winding of the positive electrode 21, negative electrode 22, and separator 23. The positive electrode 21 also has a positive electrode active material covering portion 21B. Figure 4 The insulating layer 101 (sparsely marked with dots) is the boundary between the non-covered portion 21C of the positive electrode active material and the part marked with dots. Figure 4 (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 positive electrode active material non-covered portion 21C, which faces the negative electrode active material covered portion 22B across the separator 23, is covered by the insulating layer 101. The insulating layer 101 reliably prevents internal short circuits in the lithium-ion battery 1 when foreign objects enter between the negative electrode active material covered portion 22B and the positive electrode active material non-covered portion 21C. In addition, the insulating layer 101 has the following effect: it absorbs the impact when the lithium-ion battery 1 is subjected to an impact, and reliably prevents the positive electrode active material non-covered portion 21C from bending and short-circuiting with the negative electrode 22.

[0070] Here, as Figure 4As shown, the length in the width direction of the non-covered portion 21C of the positive electrode active material is set to D5, and the length in the width direction of the non-covered portion 221A of the first negative electrode active material is 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 length of the portion of 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 is set to D8, in one embodiment, D7 > D8 is preferred; for example, D7 = 4.5 (mm) and D8 = 3 (mm).

[0071] 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 this 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 of the bent portion measured from the front end of the separator 23 is sometimes substantially the same between 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 each other, in the manufacturing process of the lithium-ion battery 1 (details will be described later), the non-covered portion 21C of the positive electrode active material can be easily joined to the positive electrode current collector 24 by laser welding. Furthermore, since the non-covered portion 22C of the negative electrode active material is bent and overlapped appropriately, the non-covered portion 22C of the negative electrode active material can be easily joined to the negative electrode current collector 25 by laser welding during the manufacturing process of the lithium-ion battery 1.

[0072] (Cold collector)

[0073] In conventional lithium-ion batteries, for example, leads for extracting current are welded at both the positive and negative electrodes. This results in high internal resistance, causing the lithium-ion battery to heat up 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 end face 41, which is one end face of the electrode winding body 20, and a negative current collector 25 is disposed on end face 42, which is the other end face of the electrode winding body 20. Then, by welding the positive current collector 24 to the non-covered portion 21C of the positive active material present on end face 41 at multiple points, and by welding the negative current collector 25 to the non-covered portion 22C of the negative active material present on end face 42 (specifically, the first non-covered portion 221A of the negative active material) at multiple points, the internal resistance of the lithium-ion battery 1 is suppressed to a low level, enabling high-rate discharge.

[0074] Figure 5 A and Figure 5 Example of a current collector is shown in B. Figure 5 A is the positive current collector 24. Figure 5 B is the negative current collector 25. The positive current collector 24 and the negative current collector 25 are housed in the battery container 11 (see reference). Figure 1 The positive electrode current collector 24 is made of, for example, a metal plate made of aluminum, aluminum alloy monomers, or composite materials, while the negative electrode 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 5 As shown in Figure A, the positive current collector 24 has a shape consisting of a flat, fan-shaped portion 31 with a rectangular strip 32. A hole 35 is provided near the center of the fan-shaped portion 31, and the position of the hole 35 corresponds to the position of the through hole 26 and the hole portion (hole portion 73) described later.

[0075] Figure 5 The part indicated by point A is the insulating part 32A on the strip 32, where insulating tape is pasted or coated with insulating material. Figure 5 The portion below point A is the connecting part 32B, which connects to the sealing plate that also serves as an external terminal. It should be noted that in a battery structure without a metal center pin (not shown) in the through hole 26, the strip portion 32 is less likely to come into contact with the negative electrode potential, and therefore the insulating portion 32A may be omitted. In this case, 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 can increase the charge / discharge capacity.

[0076] 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 5 The strip-shaped portion 34 of the negative current collector plate 24 is shorter than the strip-shaped portion 32 of the positive current collector plate 24, and lacks a portion equivalent to the insulating portion 32A. Multiple circular projections 37, indicated by circles, are provided on the strip-shaped portion 34. During resistance welding, the current concentrates on the projections 37, causing them to melt, and the strip-shaped portion 34 is 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 of the negative current collector plate 25, and the position of the hole 36 corresponds to the position of the through hole 26. Because 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 cover a portion of the end faces 41 and 42. By not covering the entire battery, the electrolyte can be smoothly impregnated into the electrode winding 20 during the assembly of the lithium-ion battery 1, 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.

[0077] (positive electrode)

[0078] The positive electrode active material layer 21B at least comprises a positive electrode material (positive electrode active material) capable of lithium insertion and extraction, and may further 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.

[0079] 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.

[0080] The positive electrode conductive agent is a carbon material such as graphite, carbon black, acetylene black, or Ketjen black. However, the positive electrode conductive agent can also be a metallic material or a conductive polymer.

[0081] (negative electrode)

[0082] To improve adhesion to the negative electrode active material layer 22B, it is preferable to roughen the surface of the negative electrode foil 22A constituting the negative electrode 22. 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 further include a negative electrode binder and a negative electrode conductive agent, etc.

[0083] Anode materials include, for example, 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.

[0084] In addition, negative electrode materials include, for example, metallic materials. Examples of metallic materials include Li (lithium), Si (silicon), Sn (tin), Al (aluminum), Zr (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).

[0085] (Diaphragm)

[0086] 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. The separator 23 can also use a porous membrane as a substrate layer and include a resin layer on one or both sides. This is because the deformation of the electrode winding 20 is suppressed due to the improved adhesion between the separator 23 and the positive electrode 21 and the negative electrode 22.

[0087] The resin layer contains resins such as PVdF. When forming this resin layer, a solution obtained by dissolving the resin 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 immersed in the solution and then dried. From the perspective of improving heat resistance and battery safety, it is preferable that the resin layer contains inorganic or organic particles. 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.

[0088] (electrolyte)

[0089] 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.

[0090] Representative examples of electrolyte salts are lithium salts, but other salts may also be included. Lithium salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium hexafluorosilicate (Li2SF6). These salts can also be mixed, and from the perspective of improving battery performance, a mixture of LiPF6 and LiBF4 is particularly 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.

[0091] It should be noted that in this specification, the descriptions of the positive and negative electrodes may sometimes be omitted when both are considered. For example, when simply referred to as the non-covered active material portion, it could refer to either the positive electrode non-covered active material portion 21C or the first negative electrode non-covered active material portion 221A. Similarly, when simply referred to as a current collector, it could refer to either the positive electrode current collector 24 or the negative electrode current collector 25 (however, this is interpreted as the positive electrode side configuration corresponding to the negative electrode side configuration).

[0092] [Methods for manufacturing lithium-ion batteries]

[0093] Next, refer to Figure 6 A to Figure 6F. A method for manufacturing a lithium-ion battery 1 according to one embodiment will be described. First, a positive electrode active material is coated onto the surface of a strip-shaped positive electrode foil 21A, which serves as a positive electrode active material covering portion 21B, and a negative electrode active material is coated onto 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 is provided on the negative electrode foil 22A (a first negative electrode active material non-covered portion 221A, a second negative electrode active material non-covered portion 221B, and a third negative electrode active material non-covered portion 221C). Next, the positive electrode 21 and the negative electrode 22 are subjected to drying and other processes. Then, with the positive electrode 21 and negative electrode 22 overlapping each other across the separator 23 in opposite directions (positive electrode active material uncovered portion 21C and negative electrode active material uncovered portion 22C), they are wound into a vortex shape to form a through hole 26 at the central axis, thus producing a... Figure 6 Electrode winding body 20, like A.

[0094] Next, using a groove forming fixture (groove forming fixture 51 described later), such as... Figure 6 As shown in B, a groove 43 is formed. Specifically, a groove 43 is formed locally on end faces 41 and 42 by pressing the end face (end face 53 described later) of the groove forming jig 51 perpendicularly against end faces 41 and 42. This method creates a groove 43 that extends radially from the through hole 26. The groove 43 extends, for example, from the outer edge of each of the end faces 41 and 42 to the through hole 26. It should be noted that... Figure 6 The number and configuration of slots 43 shown in B are just one example and are not limited to the example shown in the figure.

[0095] Then, using a flat surface forming fixture (flat surface forming fixture 61 described later), such as... Figure 6 As shown in C, a flat surface is formed. Specifically, the flat surface is formed by pressing the end face of the clamp 61 (end face 63 described later) against the end faces 41 and 42 in a substantially vertical direction with the same pressure from both poles. As a result, the non-covered portion 21C of the positive active material and the non-covered portion 22C of the negative active material (more specifically, the first non-covered portion 221A of the negative active material) are bent toward the central axis of the winding structure and overlap each other, thereby making the end faces 41 and 42 flat surfaces. Then, the fan-shaped portion 31 of the positive current collector plate 24 is laser-welded to the end face 41, and the fan-shaped portion 33 of the negative current collector plate 25 is laser-welded to the end face 42 to perform bonding.

[0096] 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 The battery can 11 is shown in Figure E. Then, the negative current collector 25 is welded to the bottom of the battery can 11 by pressing on a welding rod (not shown). After injecting electrolyte into the battery can 11, as shown... Figure 6 As shown in Figure F, a seal is achieved using gasket 15 and battery cover 14. The lithium-ion battery 1 is manufactured as described above.

[0097] It should be noted that insulating plate 12 and insulating plate 13 can also be insulating tape. Furthermore, the joining method can be other than laser welding. Additionally, after bending the non-covered portion 21C of the positive electrode active material and the non-covered portion 221A of the first negative electrode active material, the groove 43 remains within the flat surface. The portion without the groove 43 joins with the positive electrode current collector 24 or the negative electrode current collector 25, but the groove 43 can also be partially joined with the positive electrode current collector 24 or the negative electrode current collector 25.

[0098] 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 roughness to the extent that the non-covered portion 21C of the positive electrode active material and the positive electrode current collector 24, and the non-covered portion 221A of the first negative electrode active material and the negative electrode current collector 25 can be joined.

[0099] [Jigs for forming grooves and jigs for forming flat surfaces]

[0100] When manufacturing the lithium-ion battery 1 using the above method, a welding rod needs to be inserted into the through hole 26 in order to weld the negative electrode current collector 25 to the bottom of the battery can 11. Therefore, the through hole 26 must not be blocked in the steps preceding the welding rod insertion step. Thus, to improve the ease of positioning during the groove forming step of forming the groove 43 and to prevent blockage of the through hole 26, a rod-shaped pin for inserting into the through hole 26 is provided near the center of the end face of the groove forming fixture 51. Similarly, a rod-shaped pin for inserting into the through hole 26 is also provided near the center of the end face of the flat surface forming fixture 61 to prevent the through hole 26 from being blocked by the bent positive electrode active material non-covered portion 21C and the first negative electrode active material non-covered portion 221A during the flat surface forming step.

[0101] In this configuration, the diameter of the pin needs to be appropriate. If the pin diameter is too large, there is a risk that the separator located on the innermost circumference, i.e., the circumferential surface forming the through-hole 26, may peel off or be damaged by the pin. Alternatively, there is a risk that the negative electrode active material covering portion or the like may be exposed on the circumferential surface, resulting in a defective lithium-ion battery 1. Conversely, if the pin diameter is too small, there is a risk that the pin may be held by the bent positive electrode active material non-covered portion 21C or the first negative electrode active material non-covered portion 221A, making it difficult to pull out. Alternatively, there is a risk that the welding rod may not be able to enter the through-hole 26 in subsequent processes. In this embodiment, considering these points, the groove forming fixture and the flat surface forming fixture are designed with appropriate shapes.

[0102] Figure 7 A, Figure 7 B and Figure 8 This is a diagram illustrating an example of the configuration of the slot-forming fixture 51. Specifically, Figure 7 A is the front view of the slot forming fixture 51. Figure 7 Figure B is a diagram showing an example of the configuration of one end face 53 of the slot forming fixture 51.

[0103] like Figure 7 As shown in Figure A, the slot forming fixture 51 has a main body 52 that is generally cylindrical in shape. Figure 7 As shown in B, the main body 52 has an end face 53. The pin 54 protrudes from approximately the center of the end face 53. In addition, a thin plate-shaped portion 55 is formed on the end face 53. In this embodiment, the plate-shaped portion 55 is formed by eight plate-shaped portions extending radially from the pin 54.

[0104] Figure 8 This is a magnified view of pin 54. It should be noted that... Figure 8 The plate-shaped portion 55 is omitted from the illustration. The pin 54 has a generally triangular pyramidal pointed portion 54A with a sharp front end (the side opposite to the main body portion 52). From the circular bottom surface of the pointed portion 54A, a generally cylindrical intermediate portion 54B with a generally fixed diameter is provided. At one end of the intermediate portion 54B (the side opposite to the pointed portion 54A), a generally frustum-shaped conical portion 54C with a diameter increasing toward the main body portion 52 is provided. The circular bottom surface of the pointed portion 54A and the intermediate portion 54B have diameters slightly smaller than the diameter of the through hole 26. The pointed portion 54A, the intermediate portion 54B, and the conical portion 54C are integrally formed, for example, from resin or metal, but they can also be obtained by bonding separate parts together.

[0105] Figure 9 This is a diagram illustrating an example of the configuration of the clamp 61 for forming a flat surface. Specifically, Figure 9 A is the front view of the fixture 61 for forming a flat surface. Figure 9Figure B is a diagram showing an example of the configuration of one end face 63 of the clamp 61 for forming a flat surface.

[0106] like Figure 9 As shown in Figure A, the flat surface forming fixture 61 has a main body 62 in a generally cylindrical shape. The main body 62 has an end face 63. Figure 9 As shown in B, pin 64 protrudes approximately from the center of end face 63. The portion of end face 63 other than pin 64 is flat. Pin 64 has a shape substantially the same as pin 54. That is, pin 64 has a pointed portion 64A, a middle portion 64B, and a tapered portion 64C. The approximately circular bottom surface of the pointed portion 64A and the middle portion 64B have a diameter slightly smaller than the diameter of the through hole 26. The pointed portion 64A, the middle portion 64B, and the tapered portion 64C are integrally formed, for example, from resin or metal, but can also be obtained by bonding separate parts together.

[0107] The functions of the groove forming fixture 51 and the flat surface forming fixture 61 are explained. The groove forming fixture 51 is used in the groove forming process of forming groove 43 (see...). Figure 6 In B), the slot forming jig 51 is used. For example, the slot forming jig 51 is positioned near the hole 26 on the end face 41 side, which is formed by the non-covered portion 21C of the positive active material before bending and the non-covered portion 221A of the first negative active material before bending. By pressing the slot forming jig 51 toward the inside of the electrode winding body 20 in the positioned state, the slot forming jig 51 forms eight slots 43 on the end face 41. The same process is performed on the end face 42. The slot forming process can also be performed on the end face 41 and the end face 42 simultaneously. Since the pin 54 is inserted into the through hole 26 when pressing, it is possible to prevent the through hole 26 from being blocked when forming the slots 43.

[0108] The flat surface forming fixture 61 is used in the flat surface forming process (see reference). Figure 6In C), for example, the flat surface forming jig 61 is positioned by inserting the pin 64 of the flat surface forming jig 61 near the top of the through hole 26 on the end face 41 side. By pressing the flat surface forming jig 61 toward the inside of the electrode winding body 20 in the positioned state, the flat surface forming jig 61 bends the non-covered portion 21C of the positive active material, making the end face 41 flat, thereby forming a flat surface. The same process is performed on the end face 42. The flat surface forming process can also be performed on the end face 41 and the end face 42 simultaneously. Since the pin 64 is inserted into the through hole 26 when pressing, the through hole 26 can be prevented from being blocked by the bent non-covered portion 21C of the positive active material and the non-covered portion 221A of the first negative active material when forming a flat surface. It should be noted that the above-described groove forming process and flat surface forming process can be performed manually or automatically by a specified device.

[0109] Figure 10 This is a cross-sectional view of a lithium-ion battery 1 manufactured by cutting along a plane through the central axis (a cross-section of the end faces 41 and 42 of the electrode winding 20 without grooves 43). It should be noted that... Figure 10 The diagram shows the positive electrode 21 side, but the following explanation can also be applied to the negative electrode 22 side. Additionally, in Figure 10 The illustrations of the safety valve mechanism 30, etc., have been appropriately omitted.

[0110] The peripheral surface of the through hole 26 is, for example, a diaphragm 23, and the inner peripheral side of the electrode winding 20 is formed along the stacking direction ( Figure 10 The electrode is composed of four layers of separator 23 stacked in the X-axis direction. Furthermore, the non-covered portion 21C of the positive electrode active material is bent through a flat surface forming process to form a bent portion 71, the outer surface of which becomes a flat surface 72. The positive electrode current collector 24 is welded to the flat surface 72.

[0111] In the trench forming process and the flat surface forming process, a portion of pin 54 and a portion of pin 64 are inserted into the through hole 26, and a portion of pin 54 and a portion of pin 64 are located directly above the through hole 26. As a result, the through hole 26 will not be blocked in each process, and a hole 73 is formed at the bending portion 71, where the non-covered portion 21C of the positive electrode active material is bent. The through hole 26 communicates with the hole 73, and the hole 73 communicates with the hole 35 of the positive electrode current collector plate 24.

[0112] Specifically, when pin 54 is inserted, the pointed portion 54A of pin 54 is located in the through hole 26, the middle portion 54B is located across the through hole 26 and the hole portion 73, and the tapered portion 54C is located on the upper side of the hole portion 73. Similarly, when pin 64 is inserted, the pointed portion 64A of pin 64 is located in the through hole 26, the middle portion 64B is located across the through hole 26 and the hole portion 73, and the tapered portion 64C is located on the upper side of the hole portion 73. Thus, in... Figure 10 When the lithium-ion battery 1 is viewed in cross-section, the hole 73 has a shape corresponding to the tapered portion 54C and the tapered portion 64C, that is, the width increases from the inside to the outside.

[0113] Here, in such Figure 10 In the cross-sectional view shown, the hole 73 has a first diameter DA that is substantially parallel to the stacking direction (X-axis direction) and a second diameter DB located at a predetermined distance from the first diameter DA. The first diameter DA is located on the inner side of the electrode winding 20, which is closer to the second diameter DB. As described above, since the hole 73 is tapered, the diameter increases substantially continuously from the first diameter DA to the second diameter DB. Here, "substantially continuously" means that from the first diameter DA to the second diameter DB, a portion of the non-covered portion 21C of the positive electrode active material is allowed to protrude toward the central axis, causing the diameter to locally narrow.

[0114] Here, as Figure 10 As shown, the straight line connecting the bottom surface of the positive electrode current collector 24, which is joined to the bent portion 71, is designated as the reference line DC. The first diameter DA is the smallest diameter in the range of 0.5 to 1.5 mm from the reference line DC toward the inside of the electrode winding body 20 (the range near the open end of the through hole 26 in the lithium-ion battery 1 according to this embodiment). The second diameter DB is the smallest diameter in the range of 0 to 0.2 mm from the reference line DC toward the inside of the electrode winding body 20. It should be noted that in the case of 0 mm, the second diameter DB coincides with the reference line DC. The bent portion 71 is not obtained by uniformly stacking the non-covered portion 21C of the positive electrode active material, thus resulting in slight errors. However, the first diameter DA is approximately the same size as the maximum diameter of the sharp portions 54A and 64A (or the diameter of the intermediate portions 54B and 64B), and the second diameter DB is approximately the same size as the maximum diameter of the tapered portions 54C and 64C.

[0115] It should be noted that the size of the portion in the reference line DC corresponding to the hole 35 of the positive electrode current collector 24, i.e., the size corresponding to the diameter of the hole 35, is preferably larger than the first diameter DA and the second diameter DB. Therefore, even if the bent positive electrode active material non-covered portion 21C is slightly misaligned, the positive electrode current collector 24 can reliably contact the flat surface 72, preventing poor welding.

[0116] [Regarding density]

[0117] It should be noted that, in the cross-sectional observation described above, the density of the non-covered portion of active material in the region adjacent to the inner periphery of the current collector plate of the lithium-ion battery 1 involved in this embodiment is greater than the density of the non-covered portion of active material in the region adjacent to the outer periphery of the current collector plate.

[0118] For example, such as Figure 11 As shown, region AR1 is defined as the region adjacent to the inner periphery (inner periphery 24A) of the positive current collector 24. Region AR2 is defined as the region adjacent to the outer periphery (outer periphery 24B) of the positive current collector 24. Region AR1, for example, corresponds to a square (1mm × 1mm) with its vertex CN1 at the center side of the bottom surface of the positive current collector 24 and in contact with the bottom surface. Region AR2, for example, corresponds to a square (1mm × 1mm) with its vertex CN2 at the outer side of the bottom surface of the positive current collector 24 and in contact with the bottom surface.

[0119] The density is defined by the ratio of the area occupied by the non-covered part 21C of the positive electrode active material to the area of ​​the whole region, that is, (area occupied by the non-covered part 21C of the positive electrode active material) / (area of ​​the whole region).

[0120] In this embodiment, the density in region AR1 is greater than the density in region AR2.

[0121] An example of a method for measuring density will be described. First, a lithium-ion battery 1 manufactured by the above method is cut into a circular slice at approximately half its height and embedded in resin. Next, a section containing the central axis of the lithium-ion battery 1 is cut, and the section is observed under a microscope. Based on the observation, color images corresponding to regions AR1 and AR2 are acquired by an image data acquisition device. Then, each color image is binarized using prescribed image processing software, separating it into the non-covered portion 21C of the positive electrode active material and the portion excluding it. The density is calculated based on the separation result. It should be noted that the description up to this point has used the structure of the positive electrode 21 side as an example, but the structure of the negative electrode 22 side can be described in the same way.

[0122] [Effects obtained through this implementation method]

[0123] According to this embodiment, the following effects can be obtained, for example.

[0124] In the lithium-ion battery 1, the diameter of the hole formed by the bent active material non-covered portion can be appropriately sized. That is, by increasing the diameter of the opening portion of the hole 73 communicating with the through hole 26, welding rods for welding the negative electrode current collector 25 to the bottom of the battery can 11 can be easily inserted. In addition, by increasing the diameter of the opening portion of the hole 73 communicating with the through hole 26, it is possible to prevent the welding rod from scraping the positive electrode active material non-covered portion 21C and causing the separator 23 to be rolled in during welding.

[0125] Furthermore, by using the groove forming jig 51 with a diameter smaller than that of the base and the flat surface forming jig 61, damage or peeling of the diaphragm 23 forming the through hole 26 due to the jig can be prevented during the groove forming and flat surface forming processes, thus preventing exposure of the negative electrode active material covering portion 22B. Additionally, the intermediate portions 54B and 64B ensure that the diameter (e.g., the first diameter DA) near the open end of the through hole 26 is approximately the same size. This allows the non-covered portion 21C of the positive electrode active material to be reliably positioned on the upper part of the diaphragm 23 located on the inner peripheral side, preventing exposure of the short-side end face of the diaphragm 23 and thus preventing contact between the welding electrode and this area. Furthermore, the intermediate portions 54B and 64B allow the diaphragm 23 forming the through hole 26 to be shaped in a state where it does not block the through hole 26.

[0126] When manufacturing lithium-ion batteries, the end of a thin flat plate (e.g., 0.5 mm thick) is pressed vertically against end faces 41 and 42 (during which...). Figure 6 During the process shown in step B), at the winding start side of the electrode winding body 20 (the end side of the positive or negative electrode along the long side of 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. The reason for this peeling is considered to be the stress generated when pressed against the end face 42. The peeled negative electrode active material penetrates into the interior of the electrode winding body 20, raising concerns about internal short circuits. In this embodiment, since both the second negative electrode active material non-covering portion 221B and the third negative electrode active material non-covering portion 221C are provided, peeling of the negative electrode active material can be prevented, thus preventing internal short circuits. This effect can also be achieved 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 providing both is more preferable.

[0127] 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 opposite to the positive active material covered portion 21B. This is because it is considered that even if there is a negative active material covered portion 22B on the main surface not opposite to the positive active material covered 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 the negative active material covered portion 22B with low contribution to charging and discharging is not provided, the initial capacity can be improved relative to the same volume of the electrode winding 20.

[0128] In this embodiment, since the electrode winding body 20 is formed by overlapping and winding the positive electrode 21 and the negative electrode 22 with the positive electrode active material uncovered portion 21C and the first negative electrode active material uncovered portion 221A facing opposite directions, the positive electrode active material uncovered portion 21C is concentrated on the end face 41, and the first negative electrode active material uncovered portion 221A is concentrated on the end face 42 of the electrode winding body 20. The positive electrode active material uncovered portion 21C and the first negative electrode active material uncovered portion 221A are bent, and the end faces 41 and 42 become flat surfaces. The bending direction is from the outer edge of the end faces 41 and 42 towards the through hole 26, and the adjacent circumferential active material uncovered portions are bent and overlapped in the winding state. By making the end face 41 a flat surface, the positive electrode active material uncovered portion 21C can make good contact with the positive electrode current collector 24, and the first negative electrode active material uncovered portion 221A can make good contact with the negative electrode current collector 25. In addition, by making the end faces 41 and 42 flat, the resistance of the lithium-ion battery 1 can be reduced.

[0129] Furthermore, while bending the non-covered portion 21C of the positive active material and the non-covered portion 221A of the first negative active material may appear to flatten end faces 41 and 42, without any prior processing, wrinkles and gaps (voids, spaces) may form on end faces 41 and 42 during bending, potentially preventing them from becoming flat. Here, "wrinkles" and "voids" refer to the portion of the bent non-covered portion 21C of the positive active material and the non-covered portion 221A of the first negative active material that deviates from its flatness. In this embodiment, grooves 43 are pre-formed radially from the through hole 26 on both end faces 41 and 42. By forming grooves 43, the formation of wrinkles and voids can be suppressed, resulting in flatter end faces 41 and 42. It should be noted that either the non-covered portion 21C of the positive active material or the non-covered portion 221A of the first negative active material can be bent, but it is preferable to bend both.

[0130] Example

[0131] 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 molding defect rate and solder insertion defect rate of the uncovered portion 21C of the positive electrode active material and the uncovered portion 22C of the negative electrode active material were evaluated while the size relationship between the first diameter DA and the second diameter DB were changed. It should be noted that the present invention is not limited to the examples described below.

[0132] In all the following embodiments and comparative examples, the battery size is set to 21700 (diameter 21mm, height 70mm), the width length of the negative electrode active material covering portion 22B is set to 62mm, and the width length of the separator 23 is set to 64mm. The separator 23 overlaps to cover the entire area of ​​both the positive electrode active material covering portion 21B and the negative electrode active material covering portion 22B, and the width length of the non-covered positive electrode active material portion 21C is set to 7mm. Furthermore, the number of grooves 43 is set to 8, and they are arranged at approximately equal angular intervals.

[0133] The cross-sectional observation of lithium-ion battery 1 is described below.

[0134] The lithium-ion battery 1 manufactured by the above method is cut into circular pieces at approximately half its height and embedded in resin. Next, the cross-section is cut along the plane containing the central axis of the lithium-ion battery 1, and the cross-section is observed under a microscope.

[0135] As described above, the straight line connecting the bottom surface of the current collector was designated as the reference line DC, and the smallest diameter within a range of 0.5 to 1.5 mm from the reference line DC toward the inner side of the electrode winding body 20 was measured as the first diameter DA (rounded to the nearest 1 / 100). Furthermore, the smallest diameter within a range of 0 to 0.2 mm from the reference line DC toward the inner side of the electrode winding body 20 was measured as the second diameter DB (rounded to the nearest 1 / 100).

[0136] Figure 10 , Figure 12 , Figure 13 The figures are respectively the figures corresponding to Example 1, Comparative Example 1, and Comparative Example 2.

[0137] [Example 1]

[0138] Lithium-ion battery 1 is manufactured through the above processes. At this point, pins 54 and 64 are used to shape the uncovered portions of the active material for each of the positive and negative electrodes, so that... Figure 10 As shown, during cross-sectional observation, both the positive and negative electrodes have a first diameter DA of 2.8 mm and a second diameter DB of 3.2 mm.

[0139] [Comparative Example 1]

[0140] Instead of pins 54 and 64, a cylindrical shape with a diameter of 3.0 mm is adopted. Furthermore, the non-covered portion of the active material is molded for both the positive and negative electrodes to achieve... Figure 12 As shown, during cross-sectional observation, both the positive and negative electrodes have the same first diameter DA of 3.0 mm and a second diameter DB of 3.0 mm. Otherwise, a lithium-ion battery 1 was fabricated in the same manner as in Example 1.

[0141] [Comparative Example 2]

[0142] Instead of pins 54 and 64, a cylindrical shape with a diameter of 2.4 mm is adopted. Furthermore, the non-covered portion of the active material is molded for both the positive and negative electrodes to achieve... Figure 13 As shown, during cross-sectional observation, both the positive and negative electrodes have a first diameter DA of 2.8 mm and a second diameter DB of 2.4 mm. Otherwise, a lithium-ion battery 1 was fabricated in the same manner as in Example 1.

[0143] [Evaluate]

[0144] Batteries with deformed innermost separators and exposed innermost negative electrode active material in cross-sections after the flat surface is formed are judged as defective. The ratio of the number of defective cells to the total number of samples produced is defined as the non-covered part forming defect rate of active material.

[0145] A 2.2mm diameter chrome-copper welding rod is inserted from the positive electrode side into the through hole 26 to weld the bottom of the battery can 11 to the negative electrode current collector 25. Batteries that cannot have the welding rod inserted due to the small diameter of the hole 73, or batteries with deformed separator 23 and exposed negative electrode active material covering 22B, are judged as defective. The welding rod insertion defect rate is defined as the ratio of the number of defective batteries to the total number manufactured.

[0146] One hundred lithium-ion batteries of each configuration from Example 1 and Comparative Examples 1 and 2 were manufactured and evaluated. The results are shown in Table 1.

[0147] [Table 1]

[0148]

[0149] In Example 1, the failure rate of the non-covered portion of the active material and the failure rate of electrode insertion were both 0%. This is believed to be because the tips of pins 54 and 64 are slightly smaller than the diameter of the through hole 26, thus pins 54 and 64 do not pull on the diaphragm 23. Additionally, this is believed to be because the opening (second diameter DB) for electrode insertion is wide, making electrode insertion easy, and the electrode does not contact the non-covered portion 21C of the positive electrode active material. Alternatively, it is believed that the electrode does not deform the diaphragm 23.

[0150] In Comparative Example 1, the electrode insertion defect rate was 0%, but the active material non-coverage forming defect rate was high in both the positive and negative electrodes (5% for the positive electrode and 8% for the negative electrode). This is believed to be because the diameter of the second diameter DB is small, so in the groove forming process and the flat surface forming process, the inner circumferential diaphragm 23 is rolled in, exposing the negative electrode active material covering portion 22B.

[0151] In Comparative Example 2, the failure rate of the non-covered active material forming was 0% at both the positive and negative electrodes, but the electrode insertion failure rate was as high as 4%. The reason for this is believed to be that the second opening diameter of the hole 73 is too small relative to the diameter of the electrode, thus making it impossible to insert the electrode into the through hole 26.

[0152] In summary, the configuration shown in Example 1 can be considered a preferred configuration of the lithium-ion battery 1.

[0153] <Variation Example>

[0154] 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.

[0155] The shapes of pins 54 and 64 can be modified appropriately. For example, they can also be pins without the middle part 54B or 64B.

[0156] The size of regions AR1 and AR2 can also be larger than 1mm×1mm.

[0157] In the embodiments and comparative examples, the number of slots 43 is set to 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.

[0158] 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.

[0159] Without departing from the spirit of the invention, this invention can also be applied to batteries other than 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 rectangular, elliptical, flat, etc. Furthermore, this invention can also be implemented as a battery manufacturing method.

[0160] <Application Examples>

[0161] (1) Battery pack

[0162] Figure 14This is a block diagram illustrating a circuit configuration 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 and electronic devices for charging and discharging.

[0163] The battery pack 301 is constructed by connecting multiple secondary batteries 301a in series and / or parallel. Figure 14 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.

[0164] Temperature detection unit 318 is connected to temperature detection element 308 (e.g., thermistor), measures 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 measurement unit 313 measures the current using current detection resistor 307 and provides the measured current to control unit 310.

[0165] 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 an OFF control signal to the switch unit 304 to prevent overcharging or over-discharging.

[0166] After the charging control switch 302a or the discharging control switch 303a is turned off, charging or discharging can only be performed through diode 302b or diode 303b. These charging and discharging switches can use semiconductor switches such as MOSFETs. It should be noted that in Figure 10 In the middle, the switch part 304 is provided on the + side, but it can also be provided on the - side.

[0167] The memory 317 consists of RAM and ROM, which stores the values ​​of battery characteristics, full charge capacity, remaining capacity, etc. calculated by the control unit 310, and can be rewritten.

[0168] (2) Electronic devices

[0169] The secondary batteries described in the above embodiments or examples of the present invention can be installed in electronic devices, electric conveying equipment, energy storage devices, and other equipment to supply power.

[0170] 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, electrically powered transmission equipment, energy storage devices, power tools, and electrically powered drones, which are described later, can also be broadly included in the category of electronic devices.

[0171] Examples of electric conveying 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 and 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.

[0172] Examples of energy storage devices include commercial or residential energy storage modules, and power storage devices for use in buildings such as residences, high-rises, and offices, or for power generation equipment.

[0173] (3) Power tools

[0174] Reference Figure 15 As an example of an electric tool to which the present invention can be applied, an electric screwdriver will be briefly described. 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 in the lower frame of the handle of the electric screwdriver 431. The battery pack 430 is 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.

[0175] Alternatively, the battery pack 430 and the motor control unit 435 may each have a microcomputer (not shown), enabling the charging and discharging information of the battery pack 430 to communicate with each other. 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.

[0176] (4) Energy storage system for electric vehicles

[0177] As an example of applying the present invention to an energy storage system for electric vehicles, Figure 16The diagram schematically illustrates a configuration example of a hybrid vehicle (HV) employing a series hybrid system. A series hybrid system is a vehicle that uses an electric drive conversion device to operate on electricity generated by a generator that powers the engine, or electricity temporarily stored in a battery.

[0178] 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.

[0179] 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 battery 608 stores the electricity generated by the generator 602 using the rotational force produced by the engine 601. Various sensors 610 control the engine speed or the opening of a throttle valve (not shown) via the vehicle control unit 609.

[0180] 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 power 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).

[0181] 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.

[0182] The above explanation uses a series hybrid vehicle as an example, but the present 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 present invention can also be applied to electric vehicles (EVs or BEVs) and fuel cell vehicles (FCVs) that do not use an engine but only rely on a drive motor for propulsion.

[0183] Explanation of reference numerals in the attached figures

[0184] 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 non-covered portion, 22…Negative electrode, 22A…Negative electrode foil, 22B…Negative electrode active material layer, 22C…Negative electrode active material non-covered portion, 23…Separator, 24…Positive electrode current collector, 25…Negative electrode current collector, 26…Through hole, 41, 42…End face, 43…Groove, 221A…First negative electrode active material non-covered portion, 221B…Second negative electrode active material non-covered portion, 221C…Third negative electrode active material non-covered portion, DA…First diameter, DB…Second diameter, DC…Reference line, AR1, AR2…Region.

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 strip-shaped positive electrodes and strip-shaped negative electrodes are stacked in the electrode winding body, separated by a separator. The positive electrode has a positive active material covered portion and a positive active material uncovered portion on a strip-shaped positive electrode foil. The negative electrode has a negative active material covered portion covered with a negative active material layer on a strip-shaped negative electrode foil, and a negative active material uncovered portion extending at least along the long side of the negative electrode foil. 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 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 has a flat surface and a groove formed on the flat surface. The flat surface is formed by bending and overlapping one or both of the uncovered portions of the positive electrode active material and the uncovered portions of the negative electrode active material toward the central axis of the wound structure. When viewed in cross-section using a plane passing through the central axis, The hole formed in the portion obtained by the bending has a first diameter and a second diameter that are substantially parallel to the direction of the stacking. The first diameter is located further inside the electrode winding than the second diameter. From the first diameter to the second diameter, the diameter increases approximately continuously.

2. The secondary battery according to claim 1, wherein, In the cross-sectional view, the straight line connecting the bottom surface of the current collector plate, which is joined to the portion obtained by the bending, is taken as the reference line. The first diameter is the smallest diameter in the range of 0.5 to 1.5 mm from the reference line toward the inside of the electrode winding. The second diameter is the smallest diameter in the range of 0 to 0.2 mm from the reference line toward the inside of the electrode winding.

3. The secondary battery according to claim 2, wherein, The portion of the baseline corresponding to the hole in the current collector is larger than the first diameter and the second diameter.

4. The secondary battery according to claim 2 or 3, wherein, In the cross-sectional observation, the density of the non-covered active material in the region adjacent to the inner periphery of the current collector is greater than the density of the non-covered active material in the region adjacent to the outer periphery of the current collector.

5. The secondary battery according to any one of claims 1 to 4, wherein, The negative electrode also has a portion of the negative electrode active material not covered at the ends of the winding start side and winding end side in the long side direction.

6. An electronic device comprising a secondary battery according to any one of claims 1 to 5.

7. An electric tool having a secondary battery according to any one of claims 1 to 5.

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