Secondary batteries, electronic devices and power tools

Abstract

A secondary battery, wherein a positive electrode active material non-covered portion (21B) of the secondary battery is joined to a positive electrode collector plate (24) at one end of an electrode winding body, and a negative electrode active material non-covered portion (22C) is joined to a negative electrode collector plate (25) at the other end of the electrode winding body, the positive electrode collector plate has a positive electrode weld bead on the surface, and the negative electrode collector plate has a negative electrode weld bead on the surface, the width of the positive electrode weld bead is greater than 0.05 mm and less than 0.18 mm, and the width of the negative electrode weld bead is greater than 0.03 mm and less than 0. .12mm or less, the thickness of the positive electrode collector plate is 0.07mm or more and 0.20mm or less, the thickness of the negative electrode collector plate is 0.05mm or more and 0.15mm or less, the thickness of the non-covered portion of the positive active material is 5μm or more and 20μm or less, the thickness of the non-covered portion of the negative active material is 6μm or more and 20μm or less, the number of overlapping sheets of the non-covered portion of the positive active material on the positive electrode side is 2 or more, and the number of overlapping sheets of the non-covered portion of the negative active material on the negative electrode side is 2 or more.

Description

Technical Field

[0001] The invention relates to a secondary battery, an electronic device and an electric tool. Background Art

[0002] The development of lithium-ion batteries is also expanding to applications that require high output, such as power tools and electric vehicles. One method of achieving high output is high-rate discharge that causes a relatively large current to flow from the battery.

[0003] For example, Patent Document 1 below states that in order to produce a battery with low internal resistance, the active material non-covered portion at the end of an electrode winding is bent, and the surface of a current collector plate arranged at the end is irradiated with laser to join the active material non-covered portion and the current collector plate.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-129328. Summary of the invention

[0007] Technical problem to be solved by the invention

[0008] The technology of Patent Document 1 has a problem that welding failure occurs and the internal resistance of the battery cannot be sufficiently reduced.

[0009] Therefore, one of the objects of the present invention is to provide a battery with low internal resistance suitable for high rate discharge.

[0010] Solutions for solving technical problems

[0011] In order to solve the above technical problems, the present invention provides a secondary battery, wherein an electrode winding body, a positive electrode collector plate and a negative electrode collector plate are contained in a battery can, and the electrode winding body has a structure in which a strip-shaped positive electrode and a strip-shaped negative electrode are stacked with a separator and wound around a central axis.

[0012] The positive electrode has a positive electrode active material covered portion covered with a positive electrode active material layer and a positive electrode active material non-covered portion on a strip-shaped positive electrode foil.

[0013] The negative electrode has a negative electrode active material covered portion covered with a negative electrode active material layer and a negative electrode active material non-covered portion on a strip-shaped negative electrode foil.

[0014] The positive electrode active material non-covered portion is joined to the positive electrode current collector plate at one end of the electrode winding body.

[0015] The negative electrode active material non-covered portion is joined to the negative electrode current collector plate at the other end of the electrode winding body.

[0016] The electrode winding body has a flat surface and a groove formed in the flat surface, wherein the flat surface is formed by bending one or both of the positive electrode active material non-covered portion and the negative electrode active material non-covered portion toward the central axis of the wound structure and overlapping each other,

[0017] The positive electrode collector plate has a positive electrode weld bead on the surface, and the negative electrode collector plate has a negative electrode weld bead on the surface.

[0018] The width of the positive electrode weld bead is 0.05 mm or more and 0.18 mm or less, and the width of the negative electrode weld bead is 0.03 mm or more and 0.12 mm or less,

[0019] The thickness of the positive electrode collector plate is 0.07 mm or more and 0.20 mm or less, and the thickness of the negative electrode collector plate is 0.05 mm or more and 0.15 mm or less.

[0020] The thickness of the positive electrode active material non-covered portion is 5 μm or more and 20 μm or less, and the thickness of the negative electrode active material non-covered portion is 6 μm or more and 20 μm or less,

[0021] The number of overlapping positive electrode active material non-covered portions on the positive electrode side is 2 or more, and the number of overlapping negative electrode active material non-covered portions on the negative electrode side is 2 or more.

[0022] Effects of the Invention

[0023] According to at least one embodiment of the present invention, a battery with low internal resistance suitable for high rate discharge can be provided. It should be noted that the content of the present invention should not be interpreted as being limited to the effects exemplified in this specification. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0025] Figure 2 This is a diagram for explaining an example of the arrangement relationship among the positive electrode, the negative electrode, and the separator in the electrode wound body.

[0026] Figure 3 A is a top view of the positive electrode collector plate. Figure 3 B is a top view of the negative electrode collector plate.

[0027] Figure 4 A, B, C, D, E, and F are diagrams for explaining an assembly process of a battery according to one embodiment.

[0028] Figure 5 It is a figure for demonstrating the position of the laser welding mark.

[0029] Figure 6 It is a diagram for explaining the number of overlapping sheets of the active material non-covered portion.

[0030] Figure 7 This is a diagram for explaining Comparative Example 1.

[0031] Figure 8 It is a figure for demonstrating comparative example 2 to comparative example 6.

[0032] Fig. 9 It is a diagram for explaining a modified example.

[0033] Fig.10 It is a connection diagram for explaining a battery pack as an application example of the present invention.

[0034] Fig.11 It is a connection diagram for explaining an electric power tool as an application example of the present invention.

[0035] Fig.12 It is a connection diagram for explaining an electric vehicle as an application example of the present invention. DETAILED DESCRIPTION

[0036] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the description will be given in the following order.

[0037] <1. One embodiment> <2. Modifications> <3. Application examples>

[0038] The embodiments and the like described below are preferred specific examples of the present invention, and the contents of the present invention are not limited to these embodiments and the like.

[0039] In the embodiment of the present invention, a cylindrical lithium ion battery is described as an example of a secondary battery.

[0040] <1. One embodiment>

[0041] First, the overall structure of a lithium-ion battery will be described. Figure 1 is a schematic cross-sectional view of a lithium-ion battery 1. For example, Figure 1 As shown, the lithium ion battery 1 is a cylindrical lithium ion battery 1 in which an electrode winding body 20 is accommodated in a battery can 11 .

[0042] Specifically, for example, the lithium ion battery 1 includes a pair of insulating plates 12 and 13 and an electrode winding 20 inside a cylindrical battery can 11. In addition, the lithium ion battery 1 may also include any one or more of a thermistor (PTC) element and a reinforcing member inside the battery can 11, for example.

[0043] [Battery can]

[0044] The battery can 11 is mainly a component for storing the electrode winding body 20. The battery can 11 is, for example, a cylindrical container with one end face open and the other end face closed. That is, the battery can 11 has an open end face (open end face 11N). The battery can 11 contains, for example, any one or two or more metal materials such as iron, aluminum, and alloys thereof. In addition, the surface of the battery can 11 may be plated with, for example, any one or two or more metal materials such as nickel.

[0045] [Insulation board]

[0046] The insulating plates 12 and 13 have a winding axis ( Figure 1 The insulating plates 12 and 13 are arranged, for example, to sandwich the electrode wound body 20 between them.

[0047] [Riveted structure]

[0048] The battery cover 14 and the safety valve mechanism 30 are caulked to the open end surface 11N of the battery can 11 via the gasket 15 to form a caulked structure 11R (press-fit connection structure). Thus, the battery can 11 is sealed with the electrode winding body 20 and the like accommodated therein.

[0049] [Battery cover]

[0050] The battery cover 14 is a member that mainly closes the open end surface 11N of the battery can 11 when the electrode winding body 20 and the like are housed in the battery can 11. The battery cover 14 is made of, for example, the same material as the material of the battery can 11. The central region of the battery cover 14 protrudes, for example, in the +Z direction. As a result, the region (peripheral region) other than the central region of the battery cover 14 contacts, for example, the safety valve mechanism 30.

[0051] [washer]

[0052] The gasket 15 is mainly a member that seals the gap between the battery can 11 (bent portion 11P) and the battery cover 14 by being interposed between the battery can 11 and the battery cover 14. The surface of the gasket 15 may be coated with asphalt or the like, for example.

[0053] The gasket 15 includes, for example, any one or more of insulating materials. The type of insulating material is not particularly limited, and may be, for example, a polymer material such as polybutylene terephthalate (PBT) and polypropylene (PP). Among them, the insulating material is preferably polybutylene terephthalate. This is because the gap between the bent portion 11P and the battery cover 14 can be fully sealed while the battery can 11 and the battery cover 14 are electrically separated from each other.

[0054] [Safety valve mechanism]

[0055] When the pressure (internal pressure) inside the battery can 11 increases, the safety valve mechanism 30 releases the internal pressure by releasing the sealing state of the battery can 11 as needed. The internal pressure of the battery can 11 increases due to, for example, gas generated by decomposition reaction of the electrolyte during charge and discharge.

[0056] [Electrode winding body]

[0057] In a cylindrical lithium-ion battery, a strip-shaped positive electrode 21 and a strip-shaped negative electrode 22 are wound into a spiral shape with a separator 23 interposed therebetween, and are housed in a battery can 11 while being immersed in an electrolyte. The positive electrode 21 is formed by forming a positive electrode active material layer on one or both sides of a positive electrode foil 21A, and the material of the positive electrode foil 21A 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 on one or both sides of a negative electrode foil 22A, and the material of the negative electrode foil 22A 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 film that allows ions, electrolytes and other substances to move while electrically insulating the positive electrode 21 and the negative electrode 22.

[0058] The positive electrode active material layer and the negative electrode active material layer cover most of the positive electrode foil 21A and the negative electrode foil 22A, respectively, but intentionally do not cover the periphery of one end in the short side direction of the strip. Hereinafter, the portion not covered by the active material layer is appropriately referred to as the active material non-covered portion 21C, 22C, and the portion covered by the active material layer is appropriately referred to as the active material covered portion 21B, 22B. In a cylindrical battery, the electrode winding body 20 is overlapped and wound with the separator 23 interposed therebetween so that the positive electrode active material non-covered portion 21C and the negative electrode active material non-covered portion 22C face in opposite directions.

[0059] Figure 2 FIG. 2 shows an example of a structure before winding in which a positive electrode 21, a negative electrode 22, and a separator 23 are stacked together. Figure 2 The width of the oblique line portion on the upper side of the negative electrode is A, and the negative electrode active material non-covered portion 22C ( Figure 2 The width of the oblique line portion on the lower side) is B. In one embodiment, preferably A>B, for example, A=7(mm), B=4(mm). The length of the portion of the non-covered portion 21C of the positive electrode active material protruding from one end in the width direction of the separator 23 is C, and the length of the portion of the non-covered portion 22C of the negative electrode active material protruding from the other end in the width direction of the separator 23 is D. In one embodiment, preferably C>D, for example, C=4.5(mm), D=3(mm).

[0060] The non-covered active material portion 21C of the positive electrode is composed of, for example, aluminum, and the non-covered active material portion 22C of the negative electrode is composed of, for example, copper, and therefore, generally speaking, the non-covered active material portion 21C of the positive electrode is softer (Young's modulus is lower) than the non-covered active material portion 22C of the negative electrode. Therefore, in one embodiment, A>B and C>D are more preferred. In this case, when the non-covered active material portion 21C of the positive electrode and the non-covered active material portion 22C of the negative electrode are bent at the same pressure from both sides, the height of the bent portion measured from the front end of the separator 23 is the same in the positive electrode 21 and the negative electrode 22. At this time, since the non-covered active material portions 21C and 22C are bent and overlap appropriately, the non-covered active material portions 21C and 22C can be easily joined to the collector plates 24 and 25 by laser welding. The joining in one embodiment refers to electrical connection, but the joining method is not limited to laser welding.

[0061] In the positive electrode 21, a 3 mm wide section including the boundary between the active material non-covered section 21C and the active material covered section 21B is surrounded by the insulating layer 101 ( Figure 2 The insulating layer 101 covers the entire area of ​​the active material non-covered portion 21C of the positive electrode that is opposite to the active material covered portion 22B of the negative electrode via the separator. The insulating layer 101 has the effect of reliably preventing the internal short circuit of the lithium ion battery 1 when foreign matter invades between the active material covered portion 22B of the negative electrode and the active material non-covered portion 21C of the positive electrode. In addition, the insulating layer 101 has the effect of absorbing the impact when an impact is applied to the lithium ion battery 1, and reliably preventing the active material non-covered portion 21C of the positive electrode from bending and short-circuiting with the negative electrode 22.

[0062] A through hole 26 is formed on the central axis of the electrode winding body 20. The through hole 26 is a hole for inserting the winding core for assembling the electrode winding body 20 and the electrode rod for welding. In the electrode winding body 20, the active material non-covered portion 21C of the positive electrode and the active material non-covered portion 22C of the negative electrode are overlapped and wound in opposite directions, so that the active material non-covered portion 21C of the positive electrode is concentrated on one side (end face 41) of the end face of the electrode winding body, and the active material non-covered portion 22C of the negative electrode is concentrated on the other side (end face 42) of the end face of the electrode winding body 20. In order to make good contact with the collector plates 24 and 25 for extracting current, the active material non-covered portions 21C and 22C are bent, and the end faces 41 and 42 become flat surfaces. The bending direction is from the outer peripheral edge portions 27 and 28 of the end faces 41 and 42 toward the through hole 26, and the adjacent active material non-covered portions of the winding state overlap each other and bend. It should be noted that in this specification, the term “flat surface” includes not only a completely flat surface but also a surface having some irregularities or surface roughness to the extent that the active material non-covered portion and the current collector plate can be bonded.

[0063] By bending the active material non-covered portions 21C and 22C so that they overlap, it would seem that the end faces 41 and 42 can be made flat at first glance. However, if no processing is done before bending, wrinkles or gaps (gaps, spaces) will be generated on the end faces 41 and 42 during bending, and the end faces 41 and 42 will not become flat. Here, "wrinkles" and "gaps" refer to portions of the active material non-covered portions 21C and 22C that are biased in the bent active material non-covered portions 21C and 22C, and the end faces 41 and 42 will not become flat. In order to prevent the generation of wrinkles or gaps, grooves 43 are pre-formed in the radial direction from the through hole 26 (for example, see Figure 4 B). The groove 43 extends from the outer peripheral edge portions 27 and 28 of the end faces 41 and 42 to the through hole 26. A through hole 26 is provided at the center of the electrode winding body 20, and the through hole 26 is used as a hole for inserting a welding tool in the assembly process of the lithium ion battery 1. There are cutouts in the active material non-covered portions 21C and 22C located near the through hole 26, where the winding of the positive electrode 21 and the negative electrode 22 begins. This is to prevent the through hole 26 from being blocked when bending toward the through hole 26. The groove 43 remains in the flat surface even after the active material non-covered portions 21C and 22C are bent, and the portion without the groove 43 is joined (welded, etc.) to the positive electrode collector plate 24 or the negative electrode collector plate 25. It should be noted that not only the flat surface but also the groove 43 can be joined to a portion of the collector plates 24 and 25.

[0064] The detailed structure of the electrode wound body 20 , that is, the detailed structures of the positive electrode 21 , the negative electrode 22 , the separator 23 , and the electrolyte solution will be described later.

[0065] [Current collector]

[0066] In a conventional lithium-ion battery, for example, a lead for extracting current is welded at one point on each of the positive and negative electrodes, but the internal resistance of the battery is large, and the lithium-ion battery generates heat and becomes high temperature during discharge, so it is not suitable for high-rate discharge. Therefore, in a lithium-ion battery of one embodiment, by configuring a positive electrode collector plate 24 and a negative electrode collector plate 25 on the end faces 41 and 42, and multi-point welding with the active material non-covering parts 21C and 22C of the positive or negative electrode present on the end faces 41 and 42, the internal resistance of the battery is suppressed to a low level. Bending the end faces 41 and 42 to form a flat surface also helps to reduce resistance.

[0067] Figure 3 A and Figure 3 B shows an example of a current collector plate. Figure 3 A is the positive electrode collector plate 24, Figure 3B is a negative electrode collector plate 25. The material of the positive electrode collector plate 24 is, for example, a metal plate made of a single body or a composite material of aluminum or aluminum alloy, and the material of the negative electrode collector plate 25 is, for example, a metal plate made of a single body or a composite material (cladding material) of nickel, nickel alloy, copper or copper alloy. Figure 3 As shown in FIG. 1A , the positive electrode current collector plate 24 has a flat sector-shaped plate portion 31 with a rectangular strip portion 32 . A hole 35 is formed near the center of the plate portion 31 , and the position of the hole 35 corresponds to the position of the through hole 26 .

[0068] Figure 3 The portion of A indicated by the oblique lines is an insulating portion 32A on which an insulating tape or an insulating material is pasted on the strip portion 32, and the portion below the oblique lines in the figure is a connecting portion 32B connected to the sealing plate that also serves as an external terminal. It should be noted that in the case of a battery structure in which the through hole 26 does not have a metal center pin (not shown), the possibility of the strip portion 32 contacting the portion of the negative electrode potential is low, so the insulating portion 32A may not be present. In this case, the charge and discharge capacity can be increased by increasing the width of the positive electrode 21 and the negative electrode 22 by an amount corresponding to the thickness of the insulating portion 32A.

[0069] The shape of the negative electrode current collector plate 25 is substantially the same as that of the positive electrode current collector plate 24 , but the strip-shaped portion is different.

[0070] Figure 3 The strip-shaped portion 34 of the negative electrode collector plate of B is shorter than the strip-shaped portion 32 of the positive electrode collector plate, and does not have a portion corresponding to the insulating portion 32A. The strip-shaped portion 34 has a circular protrusion (protrusion) 37 represented by a plurality of circular marks. During resistance welding, the current is concentrated on the protrusion, the protrusion melts, and the strip-shaped portion 34 is welded to the bottom of the battery can 11. Similar to the positive electrode collector plate 24, a hole 36 is opened near the center of the plate-shaped portion 33 on the negative electrode collector plate 25, and the position of the hole 36 is a position corresponding to the through hole 26. Since the plate-shaped portion 31 of the positive electrode collector plate 24 and the plate-shaped portion 33 of the negative electrode collector plate 25 are fan-shaped, part of the end faces 41 and 42 are covered. The reason for not covering the entirety is to allow the electrolyte to penetrate smoothly into the electrode winding body when assembling the battery, or to allow the gas generated when the battery becomes abnormally high temperature or overcharged to be easily discharged to the outside of the battery.

[0071] [positive electrode]

[0072] The positive electrode active material layer contains at least a positive electrode material (positive electrode active material) capable of inserting and extracting lithium, and may also contain a positive electrode binder and a positive electrode conductor, etc. The positive electrode material is preferably a lithium-containing composite oxide or a lithium-containing phosphate compound. The lithium-containing composite oxide has, for example, a layered rock salt type or a spinel type crystal structure. The lithium-containing phosphate compound has, for example, an olivine type crystal structure.

[0073] The positive electrode binder includes synthetic rubber or polymer compounds. Synthetic rubber includes styrene-butadiene rubber, fluorine rubber, EPDM rubber, etc. The polymer compounds include polyvinylidene fluoride (PVdF) and polyimide, etc.

[0074] The positive electrode conductive agent is a carbon material such as graphite, carbon black, acetylene black or Ketjen black. In addition, the positive electrode conductive agent may also be a metal material or a conductive polymer.

[0075] The thickness of the positive electrode foil 21A is preferably 5 μm or more and 20 μm or less. This is because, by setting the thickness of the positive electrode foil 21A to 5 μm or more, the positive electrode 21 can be manufactured without breaking when the positive electrode 21, the negative electrode 22, and the separator 23 are overlapped and wound. This is because, by setting the thickness of the positive electrode foil 21A to 20 μm or less, the relative area of ​​the positive electrode 21 and the negative electrode 22 can be increased while preventing the reduction of the energy density of the lithium ion battery 1, and a lithium ion battery 1 with a larger output can be manufactured.

[0076] [negative electrode]

[0077] The surface of the negative electrode foil 22A is preferably roughened to improve adhesion with the negative electrode active material layer. The negative electrode active material layer contains at least a negative electrode material (negative electrode active material) capable of inserting and releasing lithium, and may also contain a negative electrode binder and a negative electrode conductor.

[0078] The negative electrode material includes, for example, a carbon material. The carbon material is graphitizable carbon, non-graphitizable carbon, graphite, low-crystalline carbon, or amorphous carbon. The carbon material has a fibrous, spherical, granular, or flaky shape.

[0079] In addition, the negative electrode material includes, for example, a metal material. Examples of metal materials include Li (lithium), Si (silicon), Sn (tin), Al (aluminum), Zn (zinc), and Ti (titanium). Metal elements form compounds, mixtures, or alloys with other elements, and examples thereof include silicon oxide (SiO x (0<x≤2)), silicon carbide (SiC) or an alloy of carbon and silicon, lithium titanate (LTO).

[0080] The thickness of the negative electrode foil 22A is preferably 5 μm or more and 20 μm or less. This is because, by setting the thickness of the negative electrode foil 22A to 5 μm or more, the positive electrode 21, the negative electrode 22, and the separator 23 can be manufactured without breaking the negative electrode 22 when they are overlapped and wound. This is because, by setting the thickness of the negative electrode foil 22A to 20 μm or less, the relative area of ​​the positive electrode 21 and the negative electrode 22 can be increased while preventing the reduction of the energy density of the lithium ion battery 1, and a lithium ion battery 1 with a larger output can be manufactured.

[0081] [Diaphragm]

[0082] The separator 23 is a porous film containing a resin, or a laminated film of two or more porous films. The resin is polypropylene and polyethylene, etc. The separator 23 can use a porous film as a substrate layer, and contain a resin layer on one or both sides of the substrate layer. This is because the adhesion of the separator 23 to the positive electrode 21 and the negative electrode 22 can be improved, thereby preventing the electrode winding body 20 from deforming.

[0083] The resin layer contains resins such as PVdF. When forming the resin layer, after a solution in which a resin is dissolved in an organic solvent is applied to the substrate layer, the substrate layer is dried. It should be noted that the substrate layer may also be dried after being immersed in the solution. From the viewpoint of improving heat resistance and battery safety, it is preferred that the resin layer contain inorganic particles or organic particles. The types of inorganic particles are aluminum oxide, aluminum nitride, aluminum hydroxide, magnesium hydroxide, boehmite, talc, silicon dioxide, mica, etc. In addition, a surface layer with inorganic particles as the main component formed by sputtering, ALD (atomic layer deposition) method, etc. may be used instead of the resin layer.

[0084] The thickness of the separator 23 is preferably 4 μm or more and 30 μm or less. By setting the thickness of the separator to 4 μm or more, an internal short circuit caused by the contact between the positive electrode 21 and the negative electrode 22 relative to each other through the separator 23 can be prevented. By setting the thickness of the separator 23 to 30 μm or less, lithium ions or electrolyte can easily pass through the separator 23, and in addition, the electrode density of the positive electrode 21 and the negative electrode 22 can be increased when winding.

[0085] [Electrolyte]

[0086] The electrolyte comprises a solvent and an electrolyte salt, and may further comprise an additive as required. The solvent is a non-aqueous solvent such as an organic solvent or water. The electrolyte containing a non-aqueous solvent is referred to as a non-aqueous electrolyte. The non-aqueous solvent is a cyclic carbonate, a chain carbonate, a lactone, a chain carboxylic acid ester or a nitrile (mononitrile) etc.

[0087] A representative example of an electrolyte salt is a lithium salt, but it may also contain salts other than lithium salts. Lithium salts are lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), dilithium hexafluorosilicate (Li2SF6), etc. These salts may also be used in combination, and from the viewpoint of improving battery characteristics, it is preferred to use LiPF6 and LiBF4 in combination. The content of the electrolyte salt is not particularly limited, but is preferably 0.3 mol / kg to 3 mol / kg relative to the solvent.

[0088] [Method for manufacturing lithium-ion battery]

[0089] Reference Figure 4 A to Figure 4 F, a method for manufacturing a lithium ion battery 1 according to an embodiment is described. First, a positive electrode active material is applied and attached to the surface of a strip-shaped positive electrode foil 21A, which is used as a covering portion of the positive electrode 21, and a negative electrode active material is applied and attached to the surface of a strip-shaped negative electrode foil 22A, which is used as a covering portion of the negative electrode 22. At this time, active material non-covered portions 21C and 22C where the positive electrode active material and the negative electrode active material are not applied and attached are made at one end of the short side direction of the positive electrode 21 and one end of the short side direction of the negative electrode 22. An incision is made in a portion of the active material non-covered portions 21C and 22C, that is, a portion corresponding to the start of winding during winding. The positive electrode 21 and the negative electrode 22 are subjected to processes such as drying. Then, the positive electrode active material non-covered portion 21C and the negative electrode active material non-covered portion 22C are overlapped with the separator 23 in opposite directions, and are wound into a spiral shape in a manner such that the through hole 26 is formed on the central axis and the cutout is arranged near the central axis, thereby producing Figure 4 An electrode wound body 20 like A.

[0090] Then, if Figure 4 As shown in FIG. 1B , grooves 43 are formed in a portion of end faces 41 and 42 by pressing the ends of a thin flat plate (eg, 0.5 mm thick) perpendicularly to end faces 41 and 42. Grooves 43 extending radially from through-hole 26 are formed by this method. Figure 4 The number and arrangement of the slots 43 shown in B are only an example. Figure 4 As shown in C, the same pressure is applied from both sides in a direction substantially perpendicular to the end faces 41, 42 to bend the non-covered active material portion 21C of the positive electrode and the non-covered active material portion 22C of the negative electrode so that the end faces 41, 42 become flat surfaces. At this time, a load is applied by the plate surface of a flat plate, etc., in such a manner that the non-covered active material portions located at the end faces 41, 42 are bent toward the central axis and overlapped. Then, the plate-like portion 31 of the positive electrode collector plate 24 is laser welded on the end face 41, and the plate-like portion 33 of the negative electrode collector plate 25 is laser welded on the end face 42 to perform joining.

[0091] Then, if Figure 4 As shown in D, the strip portions 32 and 34 of the collector plates 24 and 25 are bent, the insulating plates 12 and 13 (or insulating tapes) are pasted on the positive collector plates 24 and the negative collector plates 25, and the electrode winding body 20 assembled as described above is inserted into the Figure 4 The bottom of the battery can 11 is welded in the battery can 11 shown in FIG. 1. After the electrolyte is injected into the battery can 11, as shown in FIG. Figure 4 As shown in F, the gasket 15 and the battery cover 14 are used for sealing.

[0092] Example

[0093] The present invention will be described in detail below based on examples comparing the open area ratio and the internal resistance of the battery using the lithium ion battery 1 produced as described above. It should be noted that the present invention is not limited to the examples described below.

[0094] In all the following embodiments and comparative examples, the battery size is set to 21700 (diameter 21 mm, height 70 mm), the number of grooves 43 is set to 8, and the grooves 43 are arranged at substantially equal angle intervals. In the bonding between the positive electrode collector plate 24 and the positive electrode active material non-covered portion 21C and the bonding between the negative electrode collector plate 25 and the negative electrode active material non-covered portion 22C, Figure 5 The configuration shown was laser welded. Figure 5 This is a schematic diagram showing the end face and the groove of the wound body through the current collector plate in order to explain the position of the laser welding mark. Figure 5 The portion indicated by the thick black solid line is the laser welding mark 51. The laser welding marks 51 are arranged in a linear shape at approximately equal angle intervals from the vicinity of the holes 35 and 36 to the outer periphery, with one laser welding mark 51 between each adjacent groove 43. Figure 5 As shown, six laser welding marks 51 are arranged in the portion covered by the current collector plates 24 and 25 , and the length of each laser welding mark 51 is 6 mm.

[0095] Hereinafter, the width of the laser weld mark 51 located on the surface of the positive electrode collector plate 24 that is not opposite to the electrode winding body is referred to as the positive electrode weld width, and the width of the laser weld mark 51 located on the surface of the negative electrode collector plate 25 that is not opposite to the electrode winding body is referred to as the negative electrode weld width. When the positive electrode weld width and the negative electrode weld width are not distinguished, they are referred to as the weld width. The weld width is obtained by observing the laser weld mark 51 located on the surface of the positive electrode collector plate 24 or the negative electrode collector plate 25 using an optical microscope. Laser welding is performed using a fiber laser (wavelength 1070±10nm). Compared with a general YAG laser, a fiber laser can reduce the diameter of the focus, so it is suitable for reliably welding metal foils such as the non-covered part of the active material of the positive electrode or the covered part of the active material of the negative electrode. When performing laser welding, the weld width is adjusted by changing welding conditions such as welding output value, scanning speed, and focal distance.

[0096] Figure 6 The cross-sectional state of the laser welding mark 51 of the positive electrode active material non-covered portion 21C and the positive electrode current collector plate 24 is schematically shown. On the end surface 41, the laser 52 is irradiated within a predetermined range from a point at a distance a from the side surface of the electrode winding body 20, thereby performing welding. The number of overlapping sheets m of the active material non-covered portion on the positive electrode side is Figure 6The number of welded sheets of the non-covered active material portion 21C (positive electrode foil) directly below the location at a distance a. The location at a distance a refers to the location farthest from the center axis in the trajectory formed by the laser 52. By cutting the battery on a plane parallel to the center axis and observing the weld, the number of overlapping sheets of the non-covered active material portion can be confirmed. The figure of the laser welding state of the non-covered active material portion 22C of the negative electrode and the negative electrode collector plate 25 is omitted. The number n of overlapping sheets of the non-covered active material portion on the negative electrode side is the number of welded sheets of the non-covered active material portion 22C (negative electrode foil) directly below the location at a distance a. By changing Figure 2 The length C of the portion of the non-covered portion 21C of the positive electrode active material protruding from one end in the width direction of the diaphragm 23, the length D of the portion of the non-covered portion 22C of the negative electrode active material protruding from the other end in the width direction of the diaphragm 23, and the number m and n of overlapping sheets of the non-covered portion of the active material are adjusted by changing the welding conditions.

[0097] [Example 1]

[0098] The weld width of the positive electrode is set to 0.10 mm, the thickness of the positive electrode collector plate 24 is set to 0.15 mm, the thickness of the non-covered portion 21C of the active material of the positive electrode is set to 10 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 3, the weld width of the negative electrode is set to 0.06 mm, the thickness of the negative electrode collector plate is set to 0.08 mm, the thickness of the non-covered portion of the active material of the negative electrode is set to 10 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 2.

[0099] [Example 2]

[0100] The weld width of the positive electrode is set to 0.05 mm, the thickness of the positive electrode collector plate 24 is set to 0.15 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 10 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 2, the weld width of the negative electrode is set to 0.03 mm, the thickness of the negative electrode collector plate 25 is set to 0.08 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 10 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 2.

[0101] [Example 3]

[0102] The weld width of the positive electrode is set to 0.18 mm, the thickness of the positive electrode collector plate 24 is set to 0.15 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 10 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 2, the weld width of the negative electrode is set to 0.12 mm, the thickness of the negative electrode collector plate 25 is set to 0.08 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 10 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 2.

[0103] [Example 4]

[0104] The weld width of the positive electrode is set to 0.10 mm, the thickness of the positive electrode collector plate 24 is set to 0.07 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 10 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 2, the weld width of the negative electrode is set to 0.06 mm, the thickness of the negative electrode collector plate 25 is set to 0.05 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 10 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 2.

[0105] [Example 5]

[0106] The weld width of the positive electrode is set to 0.10 mm, the thickness of the positive electrode collector plate 24 is set to 0.20 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 10 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 2, the weld width of the negative electrode is set to 0.06 mm, the thickness of the negative electrode collector plate 25 is set to 0.15 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 10 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 2.

[0107] [Example 6]

[0108] The weld width of the positive electrode is set to 0.10 mm, the thickness of the positive electrode collector plate 24 is set to 0.15 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 5 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 2, the weld width of the negative electrode is set to 0.06 mm, the thickness of the negative electrode collector plate 25 is set to 0.08 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 6 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 2.

[0109] [Example 7]

[0110] The weld width of the positive electrode is set to 0.10 mm, the thickness of the positive electrode collector plate 24 is set to 0.15 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 20 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 2, the weld width of the negative electrode is set to 0.06 mm, the thickness of the negative electrode collector plate 25 is set to 0.08 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 20 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 2.

[0111] [Example 8]

[0112] The weld width of the positive electrode is set to 0.18 mm, the thickness of the positive electrode collector plate 24 is set to 0.12 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 15 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 2, the weld width of the negative electrode is set to 0.10 mm, the thickness of the negative electrode collector plate 25 is set to 0.07 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 12 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 3.

[0113] [Example 9]

[0114] The weld width of the positive electrode is set to 0.05 mm, the thickness of the positive electrode collector plate 24 is set to 0.07 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 12 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 2, the weld width of the negative electrode is set to 0.03 mm, the thickness of the negative electrode collector plate 25 is set to 0.05 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 8 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 3.

[0115] [Comparative Example 1]

[0116] The weld width of the positive electrode is set to 0.10 mm, the thickness of the positive electrode collector plate 24 is set to 0.15 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 10 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 1, the weld width of the negative electrode is set to 0.10 mm, the thickness of the negative electrode collector plate 25 is set to 0.08 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 10 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 1.

[0117] [Comparative Example 2]

[0118] The weld width of the positive electrode is set to 0.25 mm, the thickness of the positive electrode collector plate 24 is set to 0.15 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 10 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 2, the weld width of the negative electrode is set to 0.21 mm, the thickness of the negative electrode collector plate 25 is set to 0.08 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 10 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 3.

[0119] [Comparative Example 3]

[0120] The weld width of the positive electrode is set to 0.46 mm, the thickness of the positive electrode collector plate 24 is set to 0.15 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 10 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 3, the weld width of the negative electrode is set to 0.41 mm, the thickness of the negative electrode collector plate 25 is set to 0.08 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 10 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 2.

[0121] [Comparative Example 4]

[0122] The weld width of the positive electrode is set to 0.69 mm, the thickness of the positive electrode collector plate 24 is set to 0.15 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 10 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 2, the weld width of the negative electrode is set to 0.63 mm, the thickness of the negative electrode collector plate 25 is set to 0.08 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 10 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 3.

[0123] [Comparative Example 5]

[0124] The weld width of the positive electrode is set to 1.20 mm, the thickness of the positive electrode collector plate 24 is set to 0.15 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 10 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 2, the weld width of the negative electrode is set to 0.80 mm, the thickness of the negative electrode collector plate 25 is set to 0.08 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 10 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 2.

[0125] [Comparative Example 6]

[0126] The weld width of the positive electrode is set to 0.40 mm, the thickness of the positive electrode collector plate 24 is set to 0.25 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 10 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 2, the weld width of the negative electrode is set to 0.38 mm, the thickness of the negative electrode collector plate 25 is set to 0.20 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 10 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 2.

[0127] [Comparative Example 7]

[0128] The weld width of the positive electrode is set to 0.10 mm, the thickness of the positive electrode collector plate 24 is set to 0.15 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 30 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 3, the weld width of the negative electrode is set to 0.06 mm, the thickness of the negative electrode collector plate 25 is set to 0.08 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 30 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 2.

[0129] [Comparative Example 8]

[0130] The weld width of the positive electrode is set to 0.10 mm, the thickness of the positive electrode collector plate 24 is set to 0.05 mm, the thickness of the non-covered portion 21C of the positive electrode active material is set to 10 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 2, the weld width of the negative electrode is set to 0.06 mm, the thickness of the negative electrode collector plate 25 is set to 0.03 mm, the thickness of the non-covered portion 22C of the negative electrode active material is set to 10 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 2.

[0131] [Comparative Example 9]

[0132] The weld width of the positive electrode is set to 0.02 mm, the thickness of the positive electrode collector plate 24 is set to 0.15 mm, the thickness of the non-covered portion 21C of the active material of the positive electrode is set to 10 μm, the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side is set to 0, the weld width of the negative electrode is set to 0.02 mm, the thickness of the negative electrode collector plate 25 is set to 0.08 mm, the thickness of the non-covered portion 22C of the active material of the negative electrode is set to 10 μm, and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side is set to 0.

[0133] [evaluate]

[0134] For the above-mentioned embodiments and comparative examples, the opening area ratio, the internal resistance of the battery, and the number of overlapping sheets of the non-covered portion of the active material are calculated. After laser welding, the collector plate is observed using a microscope (laser microscope VK-X series manufactured by KEYENCE) to calculate the overall area of ​​the laser weld mark 51 (i.e., the product of the weld width, the weld length 6 mm, and the number of welds 6, including the opening area). Next, the area of ​​all parts that are considered to have through holes is summed up as the opening area, and the ratio (%) relative to the overall area of ​​the laser weld mark 51 is calculated. The opening area ratio obtained by laser welding the positive electrode collector plate 24 and the non-covered portion 21C of the active material of the positive electrode is called the opening area ratio of the positive electrode, and the opening area ratio obtained by laser welding the negative electrode collector plate 25 and the non-covered portion 22C of the active material of the negative electrode is called the opening area ratio of the negative electrode.

[0135] The internal resistance of the battery is the value of the direct current resistance (DCR), which is the value calculated by calculating the slope of the voltage value when the discharge current increases from 0A to 100A within 5 seconds. The battery with an internal resistance of 10.5mΩ or less is judged as OK, and the battery with an internal resistance of more than 10.5mΩ is judged as NG. The results are shown in Table 1.

[0136] [Table 1]

[0137]

[0138] In Examples 1 to 9, the positive electrode opening area ratio and the negative electrode opening area ratio were 0%, and the internal resistance of the battery was 10.5 mΩ or less (determined as OK), whereas in Comparative Examples 1 to 7, the positive electrode opening area ratio and the negative electrode opening area ratio were not 0%, and the internal resistance of the battery was greater than 10.5 mΩ (determined as NG). In Comparative Examples 8 and 9, the opening area ratio was 0%, but the internal resistance of the battery was greater than 10.5 mΩ (determined as NG).

[0139] In Comparative Example 1, Figure 7 As shown in FIG. 1 , the number of overlapping sheets of the active material non-covering portion is 1, and there is a gap between the bent active material non-covering portions 21C and 22C, so it can be considered that a hole or sputtering has occurred. Figure 8 As shown, an opening 53 is created. Figure 8 This is a schematic diagram showing the end face and the groove of the wound body through the current collector plate in order to explain the position of the laser welding mark. Figure 8 The portion indicated by the thick black solid line is the laser welding mark 51, and the white portion is the portion of the opening 53 formed by laser welding. This is considered to be due to excessive welding energy. In Comparative Example 7, the result of laser welding is the generation of opening 53. This is considered to be because the thickness of the active material non-covered portion 21C, 22C is too large. In Comparative Example 8, the opening area ratio of the positive electrode and the opening area ratio of the negative electrode are 0%, but the internal resistance of the battery is greater than 10.5 mΩ. This is considered to be because the thickness of the collector plates 24, 25 is relatively small. In Comparative Example 9, laser welding was attempted, but the welding was unsuccessful. This is considered to be because the welding energy is relatively small.

[0140] In Examples 1 to 9, laser welding was successful. The weld width of the positive electrode of Examples 1 to 9 was 0.05 mm or more and 0.18 mm or less, the thickness of the positive electrode collector plate 24 was 0.07 mm or more and 0.20 mm or less, the weld width of the negative electrode was 0.03 mm or more and 0.12 mm or less, the thickness of the negative electrode collector plate 25 was 0.05 mm or more and 0.15 mm or less, and the number of overlapping sheets m of the non-covered portion of the active material on the positive electrode side and the number of overlapping sheets n of the non-covered portion of the active material on the negative electrode side were both 2 or more. The thickness of the non-covered portion 21C of the active material of the positive electrode of Examples 1 to 9 was 5 μm or more and 20 μm or less, and the thickness of the non-covered portion 22C of the active material of the negative electrode was 6 μm or more and 20 μm or less. At this time, the internal resistance of the lithium ion battery 1 was all 10.5 mΩ or less.

[0141] <2. Modifications>

[0142] As mentioned above, although one embodiment of the present invention has been specifically described, the content of the present invention is not limited to the above-mentioned embodiment, and various modifications can be made based on the technical idea of ​​the present invention.

[0143] In one embodiment, if Figure 5 As shown, a laser welding mark is arranged between each adjacent groove 43, but it can also be as shown in FIG. Fig. 9 As shown, a plurality of laser welding marks are arranged between each adjacent groove 43 . Fig. 9 This is a schematic diagram showing the end face and the groove of the wound body through the current collector plate in order to explain the position of the laser welding mark. Fig. 9 The portion indicated by the thick black solid line is the laser welding mark 51. In this case, since the area of ​​the laser welding mark is further increased, the internal resistance of the battery is further reduced.

[0144] In the embodiment and the comparative example, the number of the grooves 43 is 8, but the number may be other than this.

[0145] The battery size is 21700 (21mm diameter, 70mm height), but it can also be 18650 (18mm diameter, 65mm height) or sizes other than these.

[0146] The positive electrode current collecting plate 24 and the negative electrode current collecting plate 25 include the fan-shaped plate portions 31 and 33 , but may have other shapes.

[0147] As long as it does not deviate from the main purpose of the present invention, the present invention can also be applied to batteries other than lithium-ion batteries and batteries other than cylindrical shapes (such as laminated batteries, square batteries, coin batteries, button batteries). In this case, the shape of the "end face of the electrode winding body" can be not only cylindrical, but also elliptical or flat.

[0148] <3. Application examples>

[0149] (1) Battery pack

[0150] Fig.10 1 is a block diagram showing an example of a circuit configuration when the lithium ion battery 1 according to an embodiment or example of the present invention is applied to a battery pack 300. The battery pack 300 includes a battery group 301, a switch unit 304 including a charge control switch 302a and a discharge control switch 303a, a current detection resistor 307, a temperature detection element 308, and a control unit 310. The control unit 310 controls each device and can further perform charge and discharge control in the event of abnormal heating, and calculate and correct the remaining capacity of the battery pack 300. The positive terminal 321 and the negative terminal 322 of the battery pack 300 are connected to a charger or an electronic device to perform charging and discharging.

[0151] The battery pack 301 is formed by connecting a plurality of secondary batteries 301a in series and / or in parallel. Fig.10 , a case where six secondary batteries 301 a are connected in a 2-in-parallel and 3-in-series (2P3S) manner is shown as an example.

[0152] The temperature detection unit 318 is connected to the temperature detection element 308 (e.g., a thermistor), measures the temperature of the battery pack 301 or the battery pack 300, and provides the measured temperature to the control unit 310. The voltage detection unit 311 measures the voltage of the battery pack 301 and each secondary battery 301a constituting the battery pack 301, performs A / D conversion on the measured voltage, and provides it to the control unit 310. The current measurement unit 313 measures the current using the current detection resistor 307, and provides the measured current to the control unit 310.

[0153] The switch control unit 314 controls the charge control switch 302a and the discharge control switch 303a of the switch unit 304 based on the voltage and current input from the voltage detection unit 311 and the current measurement unit 313. When the secondary battery 301a becomes higher than the overcharge detection voltage (for example, 4.20V±0.05V) or lower than the overdischarge detection voltage (2.4V±0.1V), the switch control unit 314 sends a control signal to turn off the switch unit 304, thereby preventing overcharging or overdischarging.

[0154] After the charge control switch 302a or the discharge control switch 303a is turned off, charging or discharging can be performed only through the diode 302b or the diode 303b. These charge and discharge switches can use semiconductor switches such as MOSFET. Fig.10 In the embodiment, the switch section 304 is provided on the + side, but may be provided on the - side.

[0155] The memory 317 is composed of a RAM and a ROM, and stores and rewrites the values ​​of battery characteristics, full charge capacity, remaining capacity, etc. calculated by the control unit 310 .

[0156] (2) Electronic equipment

[0157] The lithium ion battery 1 according to the above-described embodiment or example of the present invention can be mounted in an electronic device, an electric transportation device, a power storage device, or other device to supply electric power.

[0158] Examples of electronic devices include laptop computers, smart phones, tablet terminals, PDAs (portable information terminals), mobile phones, wearable terminals, digital still cameras, electronic books, music players, game consoles, hearing aids, power tools, televisions, lighting equipment, toys, medical equipment, and robots. In addition, the electric transport equipment, power storage devices, power tools, and electric drones described later may also be included in the electronic devices in a broad sense.

[0159] As electric transport equipment, electric vehicles (including hybrid vehicles), electric motorcycles, electric power-assisted bicycles, electric buses, electric scooters, unmanned guided vehicles (AGVs), railway vehicles, etc. can be listed. In addition, electric passenger aircraft and electric drones for transportation are also included. The secondary battery involved in the present invention can be used not only as a driving power source for these devices, but also as an auxiliary power source, a power source for energy regeneration, etc.

[0160] Examples of the power storage device include power storage modules for commercial or domestic use, power sources for storing electric power for buildings such as houses, buildings, and offices, and power generation facilities.

[0161] (3) Power tools

[0162] Reference Fig.11 As an electric tool to which the present invention can be applied, an example of an electric screwdriver is briefly described. An electric screwdriver 431 is provided with a motor 433 that transmits rotational power to a shaft 434 and a trigger switch 432 operated by a user. A battery pack 430 and a motor control unit 435 involved in the present invention are housed in a 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 disassembled. The lithium ion battery 1 of the present invention can be applied to the battery constituting the battery pack 430.

[0163] The battery pack 430 and the motor control unit 435 each have a microcomputer (not shown), and can communicate the charge and discharge information of the battery pack 430. The motor control unit 435 can control the operation of the motor 433 and block the power supply to the motor 433 in the event of an abnormality such as over-discharge.

[0164] (4) Power storage systems for electric vehicles

[0165] As an example of applying the present invention to a power storage system for an electric vehicle, Fig.12 1 schematically shows a configuration example of a hybrid vehicle (HV) using a series hybrid system. A series hybrid system is a vehicle that runs by using electric power generated by a generator using an engine as power, or electric power temporarily stored in a battery, through an electric driving force conversion device.

[0166] The hybrid vehicle 600 is equipped with an engine 601, a generator 602, an electric driving force conversion device 603 (a DC motor or an AC motor, hereinafter referred to as "motor 603"), a driving wheel 604a, a driving wheel 604b, a wheel 605a, a wheel 605b, a battery 608, a vehicle control device 609, various sensors 610, and a charging port 611. As the battery 608, the battery pack 300 of the present invention or a storage module equipped with a plurality of lithium-ion batteries 1 of the present invention can be applied.

[0167] The motor 603 is operated by the power of the battery 608, and the rotational force of the motor 603 is transmitted to the drive wheels 604a and 604b. The power generated by the generator 602 by the rotational force generated by the engine 601 can be stored in the battery 608. Various sensors 610 control the engine speed and the opening of the throttle valve (not shown) via the vehicle control device 609.

[0168] When the hybrid vehicle 600 is decelerated by a brake mechanism (not shown), the resistance during deceleration is applied to the motor 603 as a rotational force, and the regenerative power generated by the rotational force is stored in the battery 608. In addition, the battery 608 can be charged by connecting to an external power source via a charging port 611 of the hybrid vehicle 600. Such an HV vehicle is called a plug-in hybrid vehicle (PHV or PHEV).

[0169] It should be noted that the secondary battery involved in the present invention can also be applied to a miniaturized primary battery and used as a power source for an air pressure sensor system (TPMS: Tire Pressure Monitoring system) built into the drive wheel 604a, the drive wheel 604b, the wheel 605a, and the wheel 605b.

[0170] The above description uses a series hybrid vehicle as an example, but the present invention can also be applied to a hybrid vehicle that uses a parallel method of an engine and a motor, or a combination of a series method and a parallel method. Furthermore, the present invention can also be applied to an electric vehicle (EV or BEV) or a fuel cell vehicle (FCV) that travels only by driving a motor without using an engine.

[0171] Explanation of symbols

[0172] 1. Lithium-ion battery; 12. Insulating plate; 21. Positive electrode; 21A. Positive electrode foil; 21B. Positive electrode active material covering portion; 21C. Positive electrode active material non-covering portion; 22. Negative electrode; 22A. Negative electrode foil; 22B. Negative electrode active material covering portion; 22C. Negative electrode active material non-covering portion; 23. Diaphragm; 24. Positive electrode collector plate; 25. Negative electrode collector plate; 26. Through hole; 27, 28. Peripheral edge portion; 41, 42. End face; 43. Groove; 51. Laser welding mark.

Claims

1. A secondary battery, The battery can contains an electrode wound body, a positive electrode collector plate, and a negative electrode collector plate. The electrode wound body has a structure in which a positive electrode foil and a negative electrode foil are stacked with a separator interposed therebetween. The positive electrode foil is joined to the positive electrode collector plate at the first end surface of the electrode winding body. The negative electrode foil is joined to the negative electrode collector plate at the second end surface of the electrode winding body. The positive electrode collector plate has a positive electrode weld bead on the surface, and the negative electrode collector plate has a negative electrode weld bead on the surface. The width of the positive electrode weld is not less than 0.05 mm and not more than 0.18 mm, The width of the negative electrode weld is not less than 0.03 mm and not more than 0.12 mm, The thickness of the positive electrode collector plate is not less than 0.07 mm and not more than 0.20 mm. The thickness of the negative electrode collector plate is greater than or equal to 0.05 mm and less than or equal to 0.15 mm. The thickness of the positive electrode foil is 5 μm or more and 20 μm or less. The thickness of the negative electrode foil is 6 μm or more and 20 μm or less. The positive electrode foils of adjacent circles overlap each other at the first end surface. The electrode winding body has a flat surface and a groove formed in the flat surface, wherein the flat surface is formed by bending one or both of the positive electrode active material non-covered portion and the negative electrode active material non-covered portion toward the central axis of the wound structure and overlapping each other, The number of overlapping sheets of the negative electrode active material non-covered portion on the negative electrode side is 2 or more.

2. The secondary battery according to claim 1, wherein The positive electrode collector plate is made of aluminum or aluminum alloy.

3. The secondary battery according to claim 1 or 2, wherein: The negative electrode collector plate is made of a single body or composite material of nickel, nickel alloy, copper or copper alloy.

4. The secondary battery according to claim 3, wherein The composite material is a cladding material.

5. The secondary battery according to claim 1 or 2, wherein: The positive electrode foils are gathered at the first end surface and bent from the outer peripheral edge of the first end surface toward the through hole of the electrode winding body, and the positive electrode foils of adjacent circles overlap each other at the first end surface.

6. The secondary battery according to claim 1 or 2, wherein: The negative electrode foils are gathered at the second end surface and bent from the outer peripheral edge portion of the second end surface toward the through hole of the electrode winding body, and the negative electrode foils of adjacent circles overlap each other at the second end surface.

7. The secondary battery according to claim 1 or 2, wherein: The first end surface has a groove, The positive electrode weld bead is disposed between adjacent grooves.

8. The secondary battery according to claim 1 or 2, wherein: The first end surface has a groove, A plurality of the positive electrode weld beads are arranged between each of the adjacent grooves.

9. The secondary battery according to claim 1 or 2, wherein: The positive electrode weld is linear.

10. The secondary battery according to claim 1 or 2, wherein: The positive electrode collector plate has a hole, The positive electrode weld bead extends from the hole to the outer peripheral portion of the positive electrode current collector plate.

11. The secondary battery according to claim 1 or 2, wherein: The positive electrode weld beads are arranged at equal angle intervals.

12. The secondary battery according to claim 8, wherein The plurality of positive electrode weld beads include weld beads of equal length.

13. An electronic device, A secondary battery according to any one of claims 1 to 12.

14. An electric tool, A secondary battery according to any one of claims 1 to 12.

Images