Secondary battery, electronic device, and power tool

Abstract

A winding deviation for a secondary battery can be checked. A secondary battery in which an electrode winding body, a positive electrode current collector plate, and a negative electrode current collector plate are housed in a battery can, the electrode winding body being formed by laminating a strip-shaped positive electrode and a strip-shaped negative electrode with a separator interposed, the positive electrode having a positive electrode active material covered portion and a positive electrode active material uncovered portion on a strip-shaped positive electrode foil, the positive electrode active material covered portion being covered with a positive electrode active material layer, the negative electrode having a negative electrode active material covered portion, a negative electrode active material uncovered portion, and an insulating layer, the negative electrode active material covered portion being covered with a negative electrode active material layer on a strip-shaped negative electrode foil, the negative electrode active material uncovered portion extending at least in a longitudinal direction of the negative electrode foil, and the insulating layer being provided between the negative electrode active material covered portion and the negative electrode active material uncovered portion, the positive electrode active material uncovered portion being joined to the positive electrode current collector plate at one of electrode winding body end portions, the negative electrode active material uncovered portion being joined to the negative electrode current collector plate at the other of the electrode winding body end portions, and the insulating layer containing a metal or a metal compound having a higher X-ray shielding effect than a prescribed value.

Description

Technical Field

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

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

[0003] For example, Patent Document 1 describes a cylindrical battery without tabs for leading the battery's power to the outside, a so-called tabless structure. Patent Document 2 describes an inspection device that uses image processing to check the winding offset state of a wound object.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-178252

[0007] Patent Document 2: Japanese Patent Application Publication No. 11-51629 Summary of the Invention

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

[0009] Generally, in the manufacturing process of lithium-ion batteries, an inspection process is performed to check for winding misalignment. For example, in the case of tabless lithium-ion batteries, this inspection process detects a state where the positive active material covering the positive active material exceeds the area of ​​the negative active material covering the negative active material, which constitutes winding misalignment. In other words, it detects a state where the positive and negative active material coverings are not aligned. However, in the technologies described in Patent Documents 1 and 2, there is a problem that the winding misalignment inspection cannot be performed because the end of the negative active material covering cannot be detected.

[0010] Therefore, one of the objects of the present invention is to provide a secondary battery having a structure capable of performing a winding offset inspection, as well as an electronic device and a power tool having the secondary battery.

[0011] Technical solutions for solving technical problems

[0012] This invention provides a secondary battery.

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

[0014] The positive electrode has a positive active material covered portion and a positive active material uncovered portion on a strip-shaped positive electrode foil.

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

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

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

[0018] The insulating layer contains a metal or metal compound with a higher X-ray shielding effect than specified.

[0019] The effects of the invention

[0020] According to several embodiments of the present invention, a secondary battery having a structure capable of checking for winding misalignment can be realized. It should be noted that the content of the present invention should not be construed as limiting the effects illustrated in this specification. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of a lithium-ion battery according to one embodiment.

[0022] Figure 2 A and Figure 2 B is a diagram illustrating the positive electrode involved in one implementation.

[0023] Figure 3 A and Figure 3 B is a diagram illustrating the negative electrode involved in one implementation.

[0024] Figure 4 It is a diagram showing the positive electrode, negative electrode, and diaphragm before winding.

[0025] Figure 5 A is a top view of the positive current collector according to an embodiment. Figure 5 B is a top view of the negative current collector according to an embodiment.

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

[0027] Figure 7 This is a diagram used to illustrate the function of an insulating layer in one embodiment and the effect obtained by providing an insulating layer.

[0028] Figure 8 This is a diagram used to illustrate Comparative Example 1.

[0029] Figure 9 This is a diagram used to illustrate Comparative Example 1.

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

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

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

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

[0034] <One implementation method>

[0035] <Variation Example>

[0036] <Application Examples>

[0037] The embodiments described below are preferred examples of the present invention, and the content of the present invention is not limited to these embodiments. It should be noted that, for ease of understanding, sometimes a portion of the structure in each figure is enlarged or reduced, or some illustrations are simplified.

[0038] <One implementation method>

[0039] [Example of the overall structure of a lithium-ion battery]

[0040] 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 1-5 The overall structure of the lithium-ion battery (lithium-ion battery 1) involved in this 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, wherein the electrode winding body 20 is housed inside the battery can 11.

[0041] The lithium-ion battery 1 generally has a cylindrical battery can 11, inside which are a pair of insulating plates 12 and 13 and an electrode winding 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.

[0042] (Battery can)

[0043] The battery can 11 is the main component for housing the electrode winding 20. The battery can 11 is, for example, a cylindrical container with one open end and the other closed end. That is, the battery can 11 has an open end (open end 11N). The battery can 11 contains, for example, any one or more of the following metallic materials: iron, aluminum, and their alloys. The surface of the battery can 11 may be plated with, for example, any one or more of the following metallic materials: nickel.

[0044] (Insulating board)

[0045] Insulating plates 12 and 13 are aligned with the central axis of the electrode winding body 20 (passing approximately at the center of the end face of the electrode winding body 20 and parallel to the axis of the electrode winding body 20). 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 arranged, for example, to mutually clamp the electrode winding 20.

[0046] (Riveted structure)

[0047] On the open end face 11N of the battery can 11, the battery cover 14 and the safety valve mechanism 30 are riveted together via gaskets 15 to form a riveting structure 11R (curled structure). Thus, with the electrode winding body 20 and the like housed inside the battery can 11, the battery can 11 is sealed.

[0048] (Battery cover)

[0049] The battery cover 14 is a component that primarily closes the open end face 11N of the battery can 11 when the electrode winding body 20 and the like are housed inside the battery can 11. The battery cover 14, for example, is made of the same material as the battery can 11. A 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.

[0050] (washer)

[0051] The gasket 15 is a component that primarily seals the gap between the bend 11P and the battery cover 14 by being located between the battery canister 11 (bent portion 11P) and the battery cover 14. The surface of the gasket 15 may also be coated with, for example, asphalt.

[0052] The gasket 15 may contain one or more insulating materials. The type of insulating material is not particularly limited; for example, polymers such as polybutylene terephthalate (PBT) and polypropylene (PP) can be used. Among these, polybutylene terephthalate is preferred as the insulating material. This is because it can adequately seal the gap between the bent portion 11P and the battery cover 14 while simultaneously electrically separating the battery canister 11 and the battery cover 14.

[0053] (Safety valve mechanism)

[0054] The safety valve mechanism 30 is mainly used to release the internal pressure of the battery can 11 by releasing the seal of the battery can 11 as needed when the internal pressure rises. The cause of the internal pressure rise in the battery can 11 is, for example, gas generated by the decomposition reaction of the electrolyte during charging and discharging.

[0055] (Electrode winding body)

[0056] 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 spiral shape with a separator 23 in between, and stored in a battery can 11 while immersed in 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 or electrolyte to move.

[0057] Figure 2 A is a diagram showing 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 A. The positive electrode 21 has portions (represented by dots) covered by the positive active material layer 21B on one and another main surfaces of the positive electrode foil 21A, and also has a positive active material uncovered portion 21C, which is a portion not covered by the positive active material layer 21B. 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.

[0058] Figure 3 A is a diagram showing the negative electrode 22 before winding, viewed from the front. Figure 3 B is viewed from the side. Figure 3The diagram shows the negative electrode 22 of electrode A. The negative electrode 22 has portions (represented by dots) covered by the negative electrode active material layer 22B on one and another main surfaces of the negative electrode foil 22A, and also has a negative electrode active material uncovered portion 22C, which is a portion not covered by the negative electrode active material layer 22B. 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.

[0059] like Figure 3 As shown in Figure A, the non-covered portion 22C of the negative electrode active material has, for example, a first non-covered portion 221A of the negative electrode active material, along the long side direction of the negative electrode 22 ( Figure 3 The second negative electrode active material non-covered portion 221B extends along the short side direction of the negative electrode 22 on the winding start side of the negative electrode 22. Figure 3 The Y-axis direction (also appropriately referred to as the width direction) extends; and the third negative electrode active material non-covered portion 221C extends along the short side direction of the negative electrode 22 on the winding termination side of the negative electrode 22. Figure 3 It extends along the Y-axis. It should be noted that in... Figure 3 In A, the boundaries of the first non-covered portion 221A and the second non-covered portion 221B of the negative electrode active material, as well as the boundaries of the first non-covered portion 221A and the third non-covered portion 221C of the negative electrode active material, are represented by dashed lines.

[0060] The negative electrode 22 also has an insulating layer 22D ( Figure 3 (The gray portion in the image). The insulating layer 22D is disposed between the negative electrode active material covered portion 22B and the first negative electrode active material uncovered portion 221A. Details regarding the insulating layer 22D will be described later.

[0061] In the cylindrical lithium-ion battery 1 of this embodiment, the electrode winding body 20 is wound with the positive electrode active material non-covered portion 21C and the first negative electrode active material non-covered portion 221A facing opposite directions, with the separator 23 overlapping between them.

[0062] A through hole 26 is provided at the center of the electrode winding body 20. Specifically, the through hole 26 is a hole formed approximately at the center of the stack of positive electrode 21, negative electrode 22 and separator 23. In the assembly process of lithium-ion battery 1, the through hole 26 is used as a hole for inserting rod-shaped welding tools (hereinafter appropriately referred to as welding rods) and the like.

[0063] The details of the electrode winding 20 are explained below. Figure 4This illustrates an example of the structure before the stacking of the positive electrode 21, negative electrode 22, and separator 23. The positive electrode 21 also has an insulating layer 101. Figure 4 The gray area in the image), the insulating layer 101 covers the positive electrode active material covering portion 21B ( Figure 4 The boundary between the sparsely dotted portion of the insulating layer 101 and the non-covered portion 21C of the positive electrode active material. The length of the insulating layer 101 in the width direction is, for example, about 3 mm. All areas of the non-covered portion 21C of the positive electrode active material, which is opposite to the covered portion 22B of the negative electrode active material, separated by the separator 23, are covered by the insulating layer 101. The insulating layer 101 has the effect of reliably preventing internal short circuits of the lithium-ion battery 1 when foreign objects intrude between the covered portion 22B of the negative electrode active material and the non-covered portion 21C of the positive electrode active material. In addition, the insulating layer 101 absorbs the impact when the lithium-ion battery 1 is subjected to an impact, and has the effect of reliably preventing the non-covered portion 21C of the positive electrode active material from bending or short-circuiting with the negative electrode 22.

[0064] Here, as Figure 4 As shown, the length of the non-covered portion 21C of the positive electrode active material in the width direction is set to D5, and the length of the non-covered portion 221A of the first negative electrode active material in the width direction is set to D6. In one embodiment, it is preferable that D5 > D6, for example, D5 = 7 (mm) and D6 = 4 (mm). In one embodiment, 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 portions of the insulating layer 22E and the non-covered portion 221A of the first negative electrode active material protruding from the other end of the separator 23 in the width direction is set to D8, it is preferable that D7 > D8, for example, D7 = 4.5 (mm) and D8 = 3 (mm).

[0065] 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, generally speaking, the non-covered portion 21C of the positive electrode active material is softer (lower Young's modulus) than the non-covered portion 22C of the negative electrode active material. Therefore, in one embodiment, it is more preferable that D5 > D6 and D7 > D8, in which case, when the non-covered portion 21C of the positive electrode active material and the non-covered portion 22C of the negative electrode active material (in this example, the first non-covered portion 221A 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 the same for both 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 overlapped, 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 during the manufacturing process of the lithium-ion battery 1 (details will be described later). Furthermore, since the non-covered portion 221A of the first negative electrode active material is bent and moderately overlapped, the non-covered portion 221A of the first 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.

[0066] (Cold collector)

[0067] In conventional lithium-ion batteries, current extraction leads are welded to each of the positive and negative electrodes. However, this results in a high internal resistance, causing the lithium-ion battery to heat up and become very hot 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. Furthermore, 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 first non-covered portion 221A of the negative active material present on end face 42 at multiple points, the internal resistance of the lithium-ion battery 1 can be suppressed to a low level, enabling high-rate discharge.

[0068] Figure 5 A and Figure 5 B represents an example of a collector plate. 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 canister 11 (see reference). Figure 1 The positive current collector 24 is made of, for example, a metal plate made of aluminum or aluminum alloy monomers or composite materials, and the negative current collector 25 is made of, for example, a metal plate made of nickel, nickel alloys, copper or copper alloy monomers or composite materials. Figure 5As shown in Figure A, the positive current collector 24 is shaped as 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 that of the through hole 26.

[0069] Figure 5 The dotted portion A is the insulating portion 32A on the strip 32 where insulating tape is attached or coated with insulating material. The portion below the dotted portion in the attached drawing is the connecting portion 32B that connects to the sealing plate, which also serves as an external terminal. It should be noted that in a battery structure where the through-hole 26 does not have a metal center pin (not shown), the strip 32 is less likely to come into contact with the negative electrode potential, therefore the insulating portion 32A may be omitted. In this case, by increasing the width of the positive electrode 21 and the negative electrode 22 by an amount equivalent to the thickness of the insulating portion 32A, the charge / discharge capacity can be increased.

[0070] 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 portion 34 of the negative current collector plate 24 is shorter than the strip portion 32 of the positive current collector plate 24, and lacks a portion equivalent to the insulating portion 32A. Circular protrusions (protrusions) 37, indicated by multiple circular markings, are provided on the strip portion 34. During resistance welding, the current concentrates on the protrusions 37, causing them to melt, and the strip portion 34 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 on the negative current collector plate 25, the position of which corresponds to 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 lithium-ion battery 1, the electrolyte can be smoothly penetrated into the electrode winding body 20 during assembly, and the gas generated when the lithium-ion battery 1 is in an abnormally high temperature state or overcharged state can be easily released to the outside of the lithium-ion battery 1.

[0071] (positive electrode)

[0072] The positive electrode active material layer 21B includes at least a positive electrode material (positive electrode active material) capable of lithium insertion and extraction, and may also include 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.

[0073] 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.

[0074] The positive electrode conductive agent is a carbon material such as graphite, carbon black, acetylene black, or Ketjen black. Alternatively, the positive electrode conductive agent can also be a metallic material or a conductive polymer.

[0075] (negative electrode)

[0076] To improve adhesion to the negative electrode active material layer 22B, the surface of the negative electrode foil 22A constituting the negative electrode 22 is preferably roughened. The negative electrode active material layer 22B includes at least a negative electrode material (negative electrode active material) capable of lithium insertion and extraction, and may also include a negative electrode binder and a negative electrode conductive agent, etc.

[0077] Anode materials may include carbon materials. These carbon materials can be easily graphitized carbon, difficult-to-graphitize carbon, graphite, low-crystallinity carbon, or amorphous carbon. The shapes of carbon materials can be fibrous, spherical, granular, or flake-like.

[0078] Furthermore, negative electrode materials may 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).

[0079] (Diaphragm)

[0080] 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, polyethylene, etc. The separator 23 can use a porous membrane as a substrate layer and contain a resin layer on one or both sides. This is because it can improve the adhesion of the separator 23 to the positive electrode 21 and the negative electrode 22, respectively, thereby suppressing the deformation of the electrode winding 20.

[0081] The resin layer contains resins such as PVDF. When forming this resin layer, a solution containing the resin dissolved in an organic solvent is applied to the substrate layer, and then the substrate layer is dried. It should be noted that the substrate layer can also be dried after being immersed in the solution. From the viewpoint of improving heat resistance and battery safety, it is preferable 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.

[0082] (electrolyte)

[0083] 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.

[0084] 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 dilithium hexafluorosilicate (Li2SF6). These salts can also be used in combination; from the viewpoint of improving battery performance, a combination of LiPF6 and LiBF4 is preferred. The content of the electrolyte salt is not particularly limited, but it is preferably 0.3 mol / kg to 3 mol / kg relative to the solvent.

[0085] [Details of the insulation layer]

[0086] Next, details regarding the aforementioned insulating layer 22D will be provided. Insulating layer 22D may contain, for example, resins such as PVDF. Insulating layer 22D may also contain inorganic or organic particles. Examples of inorganic particles include any one or more of the following: aluminum oxide, aluminum nitride, aluminum hydroxide, magnesium hydroxide, boehmite, talc, silica, and mica.

[0087] like Figure 3 As shown in Figure B, in this embodiment, the negative electrode active material covering portion 22B and the insulating layer 22D are disposed on both sides of the negative electrode foil 22A. The insulating layer 22D exists between the first negative electrode active material non-covered portion 221A and the negative electrode active material covering portion 22D, which extend along the long side direction (X-axis direction) of the negative electrode 22. More specifically, the insulating layer 22D exists along the boundary between the first negative electrode active material non-covered portion 221A and the negative electrode active material covering portion 22D, which extend along the long side direction (X-axis direction) of the negative electrode 22. The thickness of the insulating layer 22D is less than or equal to the thickness of the negative electrode active material covering portion 22B. It should be noted that the structure may also have the negative electrode active material covering portion 22B and the insulating layer 22D disposed on only one main surface of the negative electrode foil 22A. Alternatively, the structure may have the negative electrode active material covering portion 22B disposed on both sides of the negative electrode foil 22A, while only the insulating layer 22D is disposed on one main surface of the negative electrode foil 22A.

[0088] Furthermore, the insulating layer 22D contains a metal or metal compound with an X-ray shielding effect higher than specified. Specifically, the insulating layer 22D contains a metal or metal compound whose X-ray shielding effect is higher than that of the metal constituting the negative electrode foil 22A (the main component metal), and the metal compound contains a metal with an X-ray shielding effect higher than that of the metal constituting the negative electrode foil 22A (the main component metal). More specifically, the insulating layer 22D contains particles of the aforementioned metal or particles of the aforementioned metal compound.

[0089] The metal with a higher X-ray shielding effect than the metal constituting the negative electrode foil 22A is, for example, one or more selected from the group consisting of tungsten (W), iridium (Ir), platinum (Pt), and gold (Au). The metal compound containing the metal with a higher X-ray shielding effect than the metal constituting the negative electrode foil 22A is, for example, one or more selected from the group consisting of metal oxides, metal sulfate compounds, and metal carbonate compounds. The metal oxide is, for example, one or more selected from the group consisting of yttrium oxide, hafnium oxide, tantalum pentoxide, and tungsten oxide. Furthermore, the metal sulfate compound is, for example, one or more selected from the group consisting of barium sulfate and strontium sulfate. Furthermore, the metal carbonate compound is strontium carbonate.

[0090] [Methods for manufacturing lithium-ion batteries]

[0091] Next, refer to Figure 6 A to Figure 6 F. A method for manufacturing a lithium-ion battery 1 according to one embodiment will be described. First, a positive electrode active material is coated onto the surface of a strip-shaped positive electrode foil 21A, which serves as a positive electrode active material covering portion 21B. A negative electrode active material is coated 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 (first negative electrode active material non-covered portion 221A, second negative electrode active material non-covered portion 221B, and third negative electrode active material non-covered portion 221C) is provided on the negative electrode foil 22A. Furthermore, an insulating layer 22D is provided when the negative electrode active material covering portion 22B is provided. Next, the positive electrode 21 and the negative electrode 22 are subjected to processes such as drying. Then, the positive electrode active material uncovered portion 21C and the negative electrode active material uncovered portion 22C are overlapped across the separator 23 with their directions opposite, and wound into a spiral shape to form a through hole 26 on the central axis, thus fabricating a... Figure 6 Electrode winding body 20, like A.

[0092] Next, by pressing the end of a thinner plate (e.g., 0.5 mm thick) perpendicularly to end faces 41 and 42, such as... Figure 6As shown in Figure B, grooves 43 are formed on a portion of end face 41 and a portion of end face 42. This method creates grooves 43 that extend radially from the through hole 26. For example, grooves 43 extend from the outer edges 27 and 28 of 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.

[0093] Then, as Figure 6 As shown in Figure C, the same pressure is applied simultaneously to end faces 41 and 42 from both pole sides in a substantially perpendicular direction, bending the uncovered portion 21C of the positive active material and the uncovered portion 22C of the negative active material (in this example, the first uncovered portion 221A of the negative active material) toward the central axis of the winding structure, forming end faces 41 and 42 as flat surfaces. At this time, a load is applied to the surface of the flat plate, such as a plate, so that the uncovered portion 21C of the positive active material on end face 41 and the first uncovered portion 221A of the negative active material on end face 42 coincide toward the central axis. Subsequently, the fan-shaped portion 31 of the positive current collector plate 24 is laser-welded to end face 41, and the fan-shaped portion 33 of the negative current collector plate 25 is laser-welded to end face 42, thus achieving a joint.

[0094] Next, as Figure 6 As 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 Inside the battery can 11 shown in Figure E, the negative electrode current collector 25 is welded to the bottom of the battery can 11 using welding rods. After the electrolyte is injected into the battery can 11, as... Figure 6 As shown in Figure F, the battery is sealed with gasket 15 and battery cover 14. The lithium-ion battery 1 was fabricated as described above.

[0095] It should be noted that, although not illustrated, a check for winding misalignment was performed on the manufactured lithium-ion battery 1. This check was performed, for example, by irradiating the lithium-ion battery 1 with X-rays using an X-ray irradiation device and analyzing the resulting X-ray image. Specifically, the positive and negative electrode sides of the lithium-ion battery 1 were sequentially irradiated with X-rays using the X-ray irradiation device. The presence or absence of winding misalignment was checked based on the contrast changes in the resulting X-ray image (X-ray transmission image). The presence or absence of winding misalignment refers to whether the positive electrode active material covering portion 21B exceeds the range of the negative electrode active material covering portion 22B, in other words, whether the positive electrode active material covering portion 21B is not aligned with the negative electrode active material covering portion 22B. If winding misalignment is confirmed, the lithium-ion battery 1 is treated as a defective product. It should be noted that the positive electrode side of the lithium-ion battery 1 refers to the region including the end face 41 of the two end faces of the generally cylindrical electrode winding body 20. The negative side of the electrode winding 20 refers to the region including end face 42 of the two end faces of the generally cylindrical electrode winding 20.

[0096] It should be noted that insulating plates 12 and 13 can also be insulating tapes. Furthermore, the joining method can be any method other than laser welding. Additionally, after bending the non-covered portions 21C and 22C of the positive and negative active materials, the groove 43 remains within the flat surface. The portion without the groove 43 joins with the positive current collector 24 or the negative current collector 25, but the groove 43 can also join with a portion of the positive or negative current collector 24 or the negative current collector 25.

[0097] It should be noted that the term "flat surface" in this specification refers not only to a completely flat surface, but also to a surface with some unevenness or surface roughness to the extent that a certain portion (e.g., the first negative electrode active material non-covered portion 21C) and the positive electrode current collector 24, and a certain portion (e.g., the first negative electrode active material non-covered portion 221A) and the negative electrode current collector 25 can be joined.

[0098] [Effects obtained through this implementation method]

[0099] (The function and effect of the insulating layer)

[0100] Reference Figure 7 The function of the insulating layer 22D and the effect obtained by setting the insulating layer 22D will be explained. Figure 7 It means along Figure 4 A diagram showing the cross-section of the electrode winding 20 when the cutting line XA-XA is cut off. For ease of explanation, in... Figure 7 In the diagram, one layer each is shown for the positive electrode 21, the negative electrode 22, and the separator 23. Additionally, in... Figure 7In the cross-sectional view, the contrast of the X-ray image obtained by irradiating the positive electrode side of the lithium-ion battery 1 is schematically shown in the upper left side, and the contrast of the X-ray image obtained by irradiating the negative electrode side of the lithium-ion battery 1 is schematically shown in the lower left side.

[0101] The end of the negative electrode active material covering portion 22B on the positive electrode side of the lithium-ion battery 1 (the end of the negative electrode foil 22A) is designated as boundary B1, and the end of the positive electrode active material covering portion 21B on the positive electrode side (the boundary between the positive electrode active material covering portion 21B and the insulating layer 101) is designated as boundary B2. Boundaries B1 and B2 can be determined based on the change in contrast of the X-ray image caused by X-ray irradiation. Figure 7 The part marked with reference to the attached drawing (AA) is used for detection. B1 is also the end of the negative electrode foil 22A, which is made of copper and has an X-ray shielding effect, so it can be detected based on the change in contrast caused by the X-ray shielding effect of the negative electrode foil 22A. In addition, since B2 is the end of the positive electrode active material covering part 21B, it can be detected based on the change in contrast caused by the X-ray shielding effect of lithium-containing composite oxides or the like contained in the positive electrode active material covering part 21B.

[0102] B3 is defined as the end of the positive electrode active material covering portion 21B (the end of the positive electrode foil 21A) on the negative electrode side of the lithium-ion battery 1, and B4 is defined as the end of the negative electrode active material covering portion 22B (the boundary between the negative electrode active material covering portion 22B and the insulating layer 22D). Boundaries B3 and B4 can be determined based on the change in contrast of the X-ray image caused by X-ray irradiation. Figure 7 The part marked BB in the attached drawing is used for detection. Since boundary B3 is the end of the positive electrode active material covering portion 21B, it can be detected based on the change in contrast caused by the X-ray shielding effect of lithium-containing composite oxides contained in the positive electrode active material covering portion 21B. Since boundary B4 is also the end of the insulating layer 22D which has an X-ray shielding effect, it can be detected based on the change in contrast caused by the X-ray shielding effect of the insulating layer 22D. Based on these changes in contrast, boundaries B1 to B4 can be detected.

[0103] To detect whether there is any winding misalignment in the tabless structure of the lithium-ion battery 1, it is necessary to detect the aforementioned boundaries B1 to B4. In the prior art (e.g., the technology described in Patent Documents 1 and 2), since the insulating layer with X-ray shielding effect is not at the end of the negative electrode active material covering portion 22B (the boundary between the negative electrode active material covering portion 22B and the insulating layer 22D), boundary B4 cannot be detected, and the winding misalignment cannot be checked. Specifically, when the main component of the negative electrode active material covering portion 22B is graphite (C), for example, the boundary between the first negative electrode active material non-covered portion 221A and the negative electrode active material covering portion 22B, i.e., the end of the negative electrode active material covering portion 22B, cannot be detected by X-ray image. The reason is that when X-rays of the intensity that pass through the negative electrode foil 22A, whose main component is copper (Cu), are irradiated, the X-ray shielding effect of graphite, which is the main component of the negative electrode active material covering part 22B, is smaller than that of the negative electrode foil 22A. Therefore, the aforementioned boundary will not manifest as a change in contrast in the X-ray image.

[0104] Thus, winding misalignment could not previously be inspected using X-rays. On the other hand, ensuring the quality of the lithium-ion battery is crucial. Therefore, to reliably align the positive electrode active material cover 21B and the negative electrode active material cover 22B, it is necessary to reduce the length of the positive electrode active material cover 21B in the width direction. Specifically, this is achieved by reducing the distance D10 between the ends of the positive electrode active material cover 21B and the negative electrode active material cover 22B (refer to...). Figure 4 as well as Figure 7 This structure has a relatively large margin, thus creating a lithium-ion battery structure that minimizes winding misalignment. However, due to the limitation of the reduced length of the positive electrode active material covering portion 21B in the width direction, there is a problem that the battery capacity cannot be increased.

[0105] According to this embodiment, as described above, the positional relationship of each structure becomes clear, and boundaries B1 to B4 can be detected, thus enabling the inspection of winding misalignment. This ensures the quality of the lithium-ion battery 1 and improves safety. Furthermore, since winding misalignment can be detected, it is not necessary to set the length of the positive electrode active material covering portion 21B in the width direction to be relatively small with a margin; compared to the prior art, the length of the positive electrode active material covering portion 21B in the width direction can be increased. This increases the battery capacity of the lithium-ion battery 1.

[0106] It should be noted that in this embodiment, the main component of the negative electrode foil 22A is copper. Therefore, as the insulating layer 22D, a layer containing a metal (elemental monomer) or metal compound with a sufficiently large atomic weight (great X-ray shielding effect) compared to copper is formed in contact with the end (coating end) of the negative electrode active material covering portion 22B. Therefore, the end of the negative electrode active material covering portion 22B can be detected by the change in contrast caused by X-ray shielding.

[0107] For example, since copper has an atomic weight of 63.55, an insulating layer 22D is formed by mixing particles of yttrium oxide (Y₂O₃), an oxide of yttrium (Y) with an atomic weight of 88.91, into a coating containing polyvinylidene fluoride (PVDF) and NMP, applying the coating in contact with the end of the negative electrode active material covering portion 22B, and then drying it. As a result, the end of the negative electrode active material covering portion 22B can be detected by the contrast of an X-ray transmission image.

[0108] It should be noted that barium sulfate (BaSO4) containing barium (Ba) with an atomic weight of 137.3 can also be used instead of yttrium oxide. Alternatively, tungsten (W) monomer with an atomic weight of 183.8 can also be used instead of yttrium oxide. Alternatively, strontium carbonate (SrCO3) containing strontium (Sr) with an atomic weight of 87.62 can also be used instead of yttrium oxide.

[0109] (Other effects)

[0110] During the manufacturing of lithium-ion battery 1, when the end of a thinner flat plate (e.g., 0.5 mm thick) is pressed perpendicularly relative to end faces 41 and 42, (the process is as follows): Figure 6 During the process shown in 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. This peeling can be considered to be caused by the stress generated when pressing the end face 42. The peeled negative electrode active material penetrates into the interior of the electrode winding body 20, which may cause an internal short circuit. In this embodiment, since 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 the occurrence of an internal short circuit. 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.

[0111] On the winding termination side of the electrode winding 20, the negative electrode 22 can have a region of non-covered negative electrode active material 22C on the main surface of the side not facing the positive electrode active material covering portion 21B. This is because it can be considered that even if there is a negative electrode active material covering portion 22B on the main surface not facing the positive electrode active material covering portion 21B, its contribution to charging and discharging is relatively low. The region of non-covered negative electrode active material 22C is preferably more than 3 / 4 turns and less than 5 / 4 turns of the electrode winding 20. At this time, since there is no negative electrode active material covering portion 22B that contributes less to charging and discharging, the initial capacity can be increased relative to the same volume of the electrode winding 20.

[0112] In this embodiment, the electrode winding body 20 is wound with the positive active material uncovered portion 21C and the negative active material uncovered portion 22C facing opposite directions. Therefore, the positive active material uncovered portion 21C is concentrated on end face 41, and the negative active material uncovered portion 22C is concentrated on end face 42 of the electrode winding body 20. The positive active material uncovered portion 21C and the first negative active material uncovered portion 221A are bent, making end faces 41 and 42 flat. The bending direction is from the outer edges 27 and 28 of each end face 41 and 42 toward the through hole 26, and adjacent peripheral active material uncovered portions overlap and bend during the winding state. Because end face 41 is flat, good contact between the positive active material uncovered portion 21C and the positive current collector plate 24 is possible, and good contact between the first negative active material uncovered portion 221A and the negative current collector plate 25 is also possible. Furthermore, by bending the end faces 41 and 42 to make them flat, the resistance of the lithium-ion battery 1 can be reduced.

[0113] Furthermore, by bending the uncovered portion 21C of the positive electrode active material and the uncovered portion 221A of the first negative electrode active material, it may appear at first glance that the end faces 41 and 42 are flat. However, if no processing is performed before bending, wrinkles or gaps (voids, spaces) will be generated on the end faces 41 and 42 during bending, and the end faces 41 and 42 may not become flat. Here, "wrinkles" or "gaps" refer to deviations in the bent uncovered portion 21C of the positive electrode active material or the uncovered portion 221A of the first negative electrode active material, resulting in the end faces 41 and 42 not becoming flat. In this embodiment, grooves 43 are pre-formed radially from the through hole 26 on the end faces 41 and 42 respectively. By forming grooves 43, the generation of wrinkles or gaps can be suppressed, and the end faces 41 and 42 can be made flatter. It should be noted that although either the non-covered portion 21C of the positive electrode active material or the non-covered portion 221A of the first negative electrode active material can be bent, it is preferable that both the non-covered portion 21C of the positive electrode active material and the non-covered portion 221A of the first negative electrode active material are bent.

[0114] Example

[0115] The present invention will now be specifically described using a lithium-ion battery 1 manufactured as described above, and using examples and comparative examples in which the discharge capacity of the lithium-ion battery 1 was evaluated. It should be noted that the present invention is not limited to the examples described below.

[0116] In all the following embodiments and comparative examples, the battery size is set to 21700 (diameter: 21 mm, height: 70 mm), the length of the long side of the positive electrode active material covering portion 21B is set to 1320 mm, the length of the long side of the negative electrode active material covering portion 22B is set to 1400 mm, the length of the width of the negative electrode active material covering portion 22B is set to 63 mm, and the length of the width of the separator 23 is set to 64 mm. The separator 23 is overlapped to cover the entire area of ​​the positive electrode active material covering portion 21B and the negative electrode active material covering portion 22B. Furthermore, the number of grooves 43 is set to 8, and they are arranged at approximately equal angular intervals.

[0117] Figure 3 This is a diagram corresponding to Example 1. Figure 8 as well as Figure 9 This is the figure corresponding to Comparative Example 1.

[0118] [Example 1]

[0119] The lithium-ion battery 1 was manufactured through the above-described process. At this point, as... Figure 3 As shown, by providing a negative electrode active material covered portion 22B and a negative electrode active material uncovered portion 22C on both sides of the negative electrode foil 22A, and cutting the negative electrode foil 22A at the location of the negative electrode active material uncovered portion 22C, a first negative electrode active material uncovered portion 221A, a second negative electrode active material uncovered portion 221B, and a third negative electrode active material uncovered portion 221C are formed. Furthermore, an insulating layer 22D is provided between the negative electrode active material covered portion 22B and the first negative electrode active material uncovered portion 221A. The insulating layer 22D has a length of 3 (mm) in the width direction. The insulating layer 22D is formed by coating a film containing PVDF, barium sulfate particles, and NMP, and then drying the coating.

[0120] [Comparative Example 1]

[0121] like Figure 8As shown in Figure A, a negative electrode active material covered portion 22B and a negative electrode active material uncovered portion 22C are provided on both sides of the negative electrode foil 22A. The negative electrode foil 22A is cut at the location of the negative electrode active material uncovered portion 22C, thereby forming a first negative electrode active material uncovered portion 221A, a second negative electrode active material uncovered portion 221B, and a third negative electrode active material uncovered portion 221C. Furthermore, an insulating layer 22E is provided between the negative electrode active material covered portion 22B and the first negative electrode active material uncovered portion 221A. The length of the insulating layer 22E in the width direction is 3 (mm). The insulating layer 22E is formed using a coating that does not contain metals or metal oxides with X-ray shielding effects. Otherwise, a lithium-ion battery 1 was manufactured in the same manner as in Example 1.

[0122] [evaluate]

[0123] The discharge capacity was determined as follows. A constant voltage-constant current charge of 2000mA for 3.5 hours was performed at 4.20V as the termination voltage under an atmosphere of 23℃±2℃. Subsequently, the discharge capacity was recorded when discharged under the same atmosphere at a termination voltage of 0.2ItA (800mA) and 2.0V. The results are shown in Table 1.

[0124] [Table 1]

[0125]

[0126] In Example 1, since winding misalignment can be detected, the distance D10 between the end of the positive electrode active material covering portion 21B and the end of the negative electrode active material covering portion 22B can be reduced. On the other hand, in Comparative Example 1, since the insulating layer 22E does not contain metals or the like that have X-ray shielding effects, therefore... Figure 9 As schematically shown by reference numeral CC in the accompanying drawings, no change in contrast is observed in the X-ray image, and boundary B4 cannot be detected. Therefore, a roll-off check cannot be performed, and the distance D10 between the end of the positive active material covering portion 21B and the end of the negative active material covering portion 22B needs to be relatively large with a margin. As a result, in Example 1, the length of the positive active material covering portion 21B in the width direction can be 2 mm larger than that in Comparative Example 1. Since the length of the positive active material covering portion 21B in the width direction can be increased, in Example 1, the discharge capacity is 4304 mAh, which is about 3% higher than the discharge capacity (4166 mAh) of Comparative Example 1.

[0127] Based on the above, it can be said that the structure corresponding to Example 1 is the preferred structure of lithium-ion battery 1.

[0128] <Variation Example>

[0129] 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.

[0130] This invention can also be applied to batteries with tabless structures where the positive electrode active material uncovered portion 21C and the first negative electrode active material uncovered portion 221A are not bent. Furthermore, a structure with a second negative electrode active material uncovered portion 221B and a third negative electrode active material uncovered portion 221C is preferred, but this invention can also be applied to lithium-ion batteries without these components.

[0131] In the embodiments and comparative examples, the number of slots 43 is 8, but it can also be any other number. The battery size is set to 21700 (diameter 21mm, height 70mm), but it can also be 18650 (diameter 18mm, height 65mm) or other sizes.

[0132] The shapes of the fan-shaped parts 31 and 33 can also be shapes other than fan-shaped.

[0133] As long as it does not depart from the spirit of the invention, the present invention can also be applied to other batteries besides lithium-ion batteries, and batteries other than cylindrical shapes (e.g., laminated batteries, prismatic batteries, coin-shaped batteries, button batteries). In this case, the shape of the "end face of the electrode winding" can be not only cylindrical, but also elliptical or flat, etc.

[0134] <Application Examples>

[0135] (1) Battery pack

[0136] Figure 10 This is a block diagram illustrating a circuit structure example when the secondary battery according to an embodiment or example of the present invention is applied to a battery pack 300. The battery pack 300 includes a battery assembly 301, a switch unit 304 including a charging control switch 302a and a discharging control switch 303a, a current sensing resistor 307, a temperature sensing element 308, and a control unit 310. The control unit 310 controls each device, thereby enabling charging and discharging control in case of abnormal heat generation, or calculating and correcting the remaining capacity of the battery pack 300. The positive terminal 321 and negative terminal 322 of the battery pack 300 are connected to a charger or electronic device for charging and discharging.

[0137] The battery pack 301 is constructed by connecting multiple secondary batteries 301a in series and / or parallel. Figure 10 The diagram illustrates, as an example, a configuration where six secondary batteries 301a are connected in a 2-parallel, 3-series (2P3S) configuration. The secondary battery of this invention can be applied to secondary battery 301a.

[0138] Temperature detection unit 318 is connected to temperature detection element 308 (e.g., thermistor) to measure the temperature of battery pack 301 or battery stack 300, and provides the measured temperature to control unit 310. Voltage detection unit 311 measures the voltage of battery pack 301 and each secondary battery 301a constituting battery pack 301, performs A / D conversion on the measured voltage, and provides it to control unit 310. Current detection unit 313 measures the current using current detection resistor 307, and provides the measured current to control unit 310.

[0139] The switch control unit 314 controls the charging control switch 302a and the discharging control switch 303a of the switch unit 304 based on the voltage and current input from the voltage detection unit 311 and the current measurement unit 313. When the secondary battery 301a reaches an overcharge detection voltage (e.g., 4.20V ± 0.05V) or an over-discharge detection voltage (2.4V ± 0.1V) or below, the switch control unit 314 sends a shut-off control signal to the switch unit 304, thereby preventing overcharging or over-discharging.

[0140] After the charging control switch 302a or the discharging control switch 303a is turned off, charging or discharging can be performed solely through diode 302b or diode 303b. These charging and discharging switches can use semiconductor switches such as MOSFETs. It should be noted that... Figure 10 In the middle, the switch part 304 is provided on the + side, but it can also be provided on the - side.

[0141] The memory 317 is composed of RAM or ROM, and can store and rewrite the values ​​of battery characteristics, full charge capacity, remaining capacity, etc. calculated by the control unit 310.

[0142] (2) Electronic devices

[0143] The secondary batteries described in the above-described 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.

[0144] 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 electric unmanned aerial vehicles (UAVs) described later can also be broadly included in the category of electronic devices.

[0145] 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 or electric unmanned aerial vehicles (UAVs) for transportation are also included. The secondary battery involved in this invention can be used not only as a power source for driving these devices, but also as an auxiliary power source, a power source for energy regeneration, etc.

[0146] As energy storage devices, examples include commercial or residential energy storage modules, and power storage devices for use in buildings such as residences, buildings, and offices, or for power generation equipment.

[0147] (3) Power tools

[0148] Reference Figure 11 A brief description will be given of an electric screwdriver as an example of an electric tool to which the present invention can be applied. The electric screwdriver 431 is equipped with a motor 433 that transmits rotational power to a shaft 434 and a user-operated trigger switch 432. A battery pack 430 and a motor control unit 435 are housed within the lower housing of the handle of the electric screwdriver 431. The battery pack 430 is either built into the electric screwdriver 431 or can be freely installed and removed. The rechargeable battery of the present invention can be used in the battery constituting the battery pack 430.

[0149] The battery pack 430 and the motor control unit 435 each have a microcomputer (not shown), and the charging and discharging information of the battery pack 430 can 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.

[0150] (4) Energy storage system for electric vehicles

[0151] As an example of applying the present invention to an energy storage system for electric vehicles, Figure 12 The diagram schematically illustrates a structural example of a hybrid vehicle (HV) employing a series hybrid system. A series hybrid system is a vehicle that uses electricity generated by a generator that powers an engine, or electricity temporarily stored in a battery, to drive a vehicle via an electric drive conversion device.

[0152] 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.

[0153] The motor 603 operates using electricity from the battery 608, and the rotational force of the motor 603 is transmitted to the drive wheels 604a and 604b. The electricity generated by the generator 602 from the rotational force produced by the engine 601 is stored in the battery 608. Various sensors 610 control the engine speed or the opening of a throttle valve (not shown) via the vehicle control unit 609.

[0154] When the hybrid vehicle 600 is decelerated by a braking mechanism (not shown), the resistance during deceleration is applied as a rotational force to the motor 603, and the regenerative electricity generated by this rotational force is stored in the battery 608. Furthermore, the battery 608 can be charged by connecting to an external power source via the charging port 611 of the hybrid vehicle 600. Such an HV vehicle is called a plug-in hybrid electric vehicle (PHV or PHEV).

[0155] 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.

[0156] 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 operate solely on a drive motor without an engine.

[0157] Explanation of reference numerals in the attached figures

[0158] 1: Lithium-ion battery; 12: Insulating plate; 21: Positive electrode; 21A: Positive electrode foil; 21B: Positive electrode active material layer; 21C: Positive electrode active material uncovered portion; 22: Negative electrode; 22A: Negative electrode foil; 22B: Negative electrode active material layer; 22C: Negative electrode active material uncovered portion; 23: Separator; 22D: Insulating layer; 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 uncovered portion; 221B: Second negative electrode active material uncovered portion; 221C: Third negative electrode active material uncovered portion.

Claims

1. A secondary battery, The battery canister contains an electrode winding, a positive current collector, and a negative current collector. The electrode winding is formed by stacking strip-shaped positive and strip-shaped negative electrodes with a separator in between. 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 electrode active material covering portion, on which a layer of negative electrode active material is covered on a strip-shaped negative electrode foil; a negative electrode active material non-covering portion, extending at least along the long side of the negative electrode foil; and an insulating layer disposed between the negative electrode active material covering portion and the negative electrode active material non-covering portion. The non-covered portion of the positive electrode active material is bonded to the positive electrode current collector on one side of the 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 insulating layer contains a metal or a metal compound, wherein the metal has a higher X-ray shielding effect than the metal constituting the negative electrode foil, and the metal compound contains a metal with a higher X-ray shielding effect than the metal constituting the negative electrode foil.

2. The secondary battery according to claim 1, wherein, The metal is selected from one or more of the group consisting of tungsten (W), iridium (Ir), platinum (Pt), and gold (Au). The metal compound is selected from one or more of the group consisting of metal oxides, metal sulfate compounds, and metal carbonate compounds.

3. The secondary battery according to claim 2, wherein, The metal oxide is selected from one or more of the group consisting of yttrium oxide, hafnium oxide, tantalum pentoxide, and tungsten oxide. The metal sulfate compound is selected from one or more compounds grouped together with barium sulfate and strontium sulfate. The metal carbonate compound is strontium carbonate.

4. The secondary battery according to claim 2 or 3, wherein, The metal constituting the negative electrode foil is copper.

5. The secondary battery according to any one of claims 1 to 3, wherein, The electrode winding has a flat surface and a groove formed on the flat surface. The flat surface is formed by bending and coinciding with the central axis of the winding structure of either or both of the uncovered portions of the positive electrode active material and the uncovered portions of the negative electrode active material.

6. The secondary battery according to any one of claims 1 to 3, wherein, The negative electrode also has a portion of the negative electrode active material not covered at each end of the winding start side and the winding end side in the long side direction.

7. An electronic device, A secondary battery having any one of claims 1 to 6.

8. A power tool, A secondary battery having any one of claims 1 to 6.

Images