Secondary battery, electronic device and electric tool

Abstract

A secondary battery, wherein the positive electrode has a covering portion covered by a positive electrode active material layer and a positive electrode active material non-covering portion on a strip-shaped positive electrode foil, and the negative electrode has a covering portion covered by a negative electrode active material layer and a negative electrode active material non-covering portion on a strip-shaped negative electrode foil, the positive electrode active material non-covering portion is joined to the positive electrode collector plate at one end of an electrode winding body, and the negative electrode active material non-covering portion is joined to the negative electrode collector plate at the other end of the electrode winding body, the secondary battery comprising: a flat surface formed by bending and overlapping the central axis of a structure wound in either or both directions of the positive electrode active material non-covering portion and the negative electrode active material non-covering portion; and a groove formed on the flat surface, a welding point group exists at a position of the positive electrode collector plate or a position of the negative electrode collector plate corresponding to a position without a groove in the flat surface, and the shape of the welding point group is concentric or spiral.

Description

Technical Field

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

[0002] Lithium-ion batteries are also being developed for applications that require high output, such as power tools and automobiles. One method of achieving high output is high-rate discharge, where a relatively large current flows through the battery. During high-rate discharge, the internal resistance of the battery becomes a problem because a large current flows.

[0003] For example, Patent Document 1 describes a battery with high current collection efficiency, in which the positive electrode and the negative electrode are wound with their overlapping positions shifted in the width direction, the ends are bent to form a flat surface, and a current collector is joined to the flat surface by laser welding.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2000-294222 Summary of the invention

[0007] Patent document 1 describes a battery with high current collection efficiency, in which a collector plate is joined to a collector protruding from one side of a plate group wound with a positive plate and a negative plate stacked with a separator by laser welding. However, since laser welding is performed in a radial direction, the intervals between the joints between the plate group and the collector plate, i.e., the welding points, are uneven. In particular, the intervals between the welding points on the periphery of the plate group are large, so there is a problem of high internal resistance of the battery.

[0008] In addition, the collector plate is joined to the flat portion of the end portion of the electrode group pressed along the winding axis direction. However, when pressing in this way, wrinkles or gaps (gaps or spaces) cannot be avoided in the flat portion. When wrinkles or gaps exist, welding with the collector plate may be poor.

[0009] Therefore, one of the objects of the present invention is to provide a battery having a low internal resistance value and capable of stably welding a current collector plate and a flat surface at an end portion.

[0010] In order to solve the above problems, the present invention provides a secondary battery, which contains an electrode winding body, a positive electrode collector plate and a negative electrode collector plate in a battery can, wherein the electrode winding body has a structure in which a strip-shaped positive electrode and a strip-shaped negative electrode are stacked and wound with a separator interposed therebetween.

[0011] The positive electrode has a strip-shaped positive electrode foil having a covered portion covered with a positive electrode active material layer and a positive electrode active material non-covered portion.

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

[0013] 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.

[0014] 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.

[0015] The secondary battery has:

[0016] A flat surface formed by bending and overlapping the central axes of the structure in which one or both of the positive electrode active material non-covered portion and the negative electrode active material non-covered portion are wound in the same direction; and

[0017] Grooves formed on a flat surface,

[0018] There are welding point groups at the positions of the positive electrode collector plate or the negative electrode collector plate corresponding to the positions without grooves on the flat surface.

[0019] The shape of the welding point group is concentric circles or spirals.

[0020] According to at least one embodiment of the present invention, the collector plate and the flat surface of the end can be reliably welded, the internal resistance of the battery can be reduced, or a high-output battery can be realized. 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

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

[0022] 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.

[0023] 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.

[0024] Figure 4 A to Figure 4 F is a diagram for explaining an assembly process of a battery according to an embodiment.

[0025] Figure 5 A and Figure 5 B is a diagram for explaining embodiments 1, 3, 5, and 7.

[0026] Figure 6 A and Figure 6 B is a diagram for explaining embodiments 2, 4, 6, and 8.

[0027] Figure 7 A and Figure 7 B is a diagram for explaining Comparative Example 1.

[0028] Figure 8 A and Figure 8 B is a diagram illustrating Comparative Example 2.

[0029] Fig. 9 A and Fig. 9 B is a diagram illustrating Comparative Example 3.

[0030] Fig.10 It is a connection diagram for explaining a battery pack as an application example of the present invention.

[0031] Fig.11 It is a connection diagram for explaining an electric power tool as an application example of the present invention.

[0032] Fig.12 It is a connection diagram for explaining an electric vehicle as an application example of the present invention. DETAILED DESCRIPTION

[0033] 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.

[0034] <1. One embodiment>

[0035] <2. Modifications>

[0036] <3. Application examples>

[0037] 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.

[0038] In the embodiment of the present invention, a cylindrical lithium ion battery is described as an example of a secondary battery.

[0039] <1. One embodiment>

[0040] 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 .

[0041] Specifically, 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. The lithium ion battery 1 may also include, for example, a thermistor (PTC) element and a reinforcing member inside the battery can 11, or two or more thereof.

[0042] [Battery can]

[0043] The battery can 11 is a component that mainly accommodates 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.

[0044] [Insulation board]

[0045] 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.

[0046] [Riveted structure]

[0047] 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 (crimped structure). Thus, the battery can 11 is sealed with the electrode winding 20 and the like accommodated therein.

[0048] [Battery cover]

[0049] 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.

[0050] [washer]

[0051] 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.

[0052] The gasket 15, for example, includes any one or more of insulating materials. The type of insulating material is not particularly limited, and may be 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.

[0053] [Safety valve mechanism]

[0054] 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.

[0055] [Electrode winding body]

[0056] 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 21B 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 22B 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 thin film that allows the movement of substances such as ions and electrolyte while electrically insulating the positive electrode 21 and the negative electrode 22.

[0057] The positive electrode active material layer 21B and the negative electrode active material layer 22B cover most of the positive electrode foil 21A and the negative electrode foil 22A, respectively, but neither of them intentionally covers the periphery of one end in the short axis direction of the strip. Hereinafter, the portion not covered by the active material layer 21B, 22B is appropriately referred to as the active material non-covered portion, and the portion covered by the active material layer 21B, 22B is appropriately referred to as the active material covered portion. In a cylindrical battery, the electrode winding body 20 is overlapped and wound with the separator 23 interposed therebetween in such a way that the active material non-covered portion 21C of the positive electrode and the active material non-covered portion 22C of the negative electrode face in opposite directions.

[0058] 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 dotted 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 dot 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).

[0059] 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 low) than the non-covered active material portion 22C of the negative electrode. Therefore, in one embodiment, A>B and C>D are more preferably, in which 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 measured from the front end of the diaphragm 23 of the bent portion 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 joining by laser welding, but the joining method is not limited to laser welding.

[0060] In the portion of the positive electrode active material non-covered portion 21C facing the negative electrode 22 via the separator 23, for example, the insulating layer 101 ( Figure 2 gray part). Figure 2 As shown in FIG. 1 , the lithium ion battery 1 is designed so that the width of the positive electrode active material layer 21B is smaller than the width of the negative electrode active material layer 22B. Therefore, without the insulating layer 101, Li metal or the like may be precipitated in the portion of the positive electrode active material non-covered portion 21C that faces the negative electrode active material layer 22B during charge and discharge, or when an impact is applied to the battery 1, the impact may not be absorbed at all, and the positive electrode active material non-covered portion 21C may be bent and contact the negative electrode 22 to cause a short circuit. The insulating layer 101 is configured to avoid these situations.

[0061] A through hole 26 is opened 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. The electrode winding body 20 is overlapped and wound in such a way that the active material non-covered portion 21C of the positive electrode and the active material non-covered portion 22C of the negative electrode face opposite directions, so that the active material non-covered portion 21C of the positive electrode is concentrated on one end face (end face 41) of the electrode winding body, and the active material non-covered portion 22C of the negative electrode is concentrated on the other end face (end face 42) 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 edge portions 27 and 28 of the end faces 41 and 42 toward the through hole 26, and the active material non-covered portions of the adjacent circumferences overlap each other and are bent in the wound state. 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.

[0062] By bending the active material non-covered portions 21C and 22C so that they overlap, it may be considered at first glance that the end faces 41 and 42 can be made flat. However, if no processing is performed 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 the portions of the active material non-covered portions 21C and 22C that are offset when bent, 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 edge portions 27 and 28 of the end faces 41 and 42 to the through hole 26. There is a through hole 26 in the center of the electrode winding body 20, and the through hole 26 is used as a hole for inserting welding tools 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 starts. 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.

[0063] 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.

[0064] [Current collector]

[0065] In a conventional lithium-ion battery, for example, leads for extracting current are welded to the positive electrode and the negative electrode, respectively. However, the internal resistance of the battery is large, and the lithium-ion battery generates heat and reaches a high temperature during discharge, so it is not suitable for high-rate discharge. Therefore, in a lithium-ion battery of one embodiment, the internal resistance of the battery is suppressed to a low level by arranging a positive electrode collector plate 24 and a negative electrode collector plate 25 on the end faces 41 and 42, and welding them to the active material non-covered parts 21C and 22C of the positive or negative electrode on the end faces 41 and 42 at multiple points. Bending the end faces 41 and 42 to form a flat surface also contributes to low resistance.

[0066] Figure 3 A and Figure 3 B shows an example of a current collector plate. Figure 3 A is a positive electrode collector plate 24, Figure 3 B 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 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 sector 31 with a rectangular strip 32 . A hole 35 is formed near the center of the sector 31 , and the position of the hole 35 corresponds to the position of the through hole 26 .

[0067] Figure 3 The dotted portion of A 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 dotted portion 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.

[0068] 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. Figure 3The strip portion 34 of the negative electrode collector plate of B is shorter than the strip portion 32 of the positive electrode collector plate, and does not have a portion corresponding to the insulating portion 32A. The strip 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 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 fan-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 fan-shaped portion 31 of the positive electrode collector plate 24 and the fan-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 is in an abnormally high temperature state or an overcharged state to be easily discharged to the outside of the battery.

[0069] [positive electrode]

[0070] 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.

[0071] 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.

[0072] 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.

[0073] [negative electrode]

[0074] The surface of the negative electrode current collector 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 extracting lithium, and may also contain a negative electrode binder and a negative electrode conductor.

[0075] 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.

[0076] 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), Zr (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).

[0077] [Diaphragm]

[0078] 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.

[0079] 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.

[0080] [Electrolyte]

[0081] 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.

[0082] 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.

[0083] [Method for manufacturing lithium-ion battery]

[0084] 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 coated on the surface of a strip-shaped positive electrode foil 21A, which is used as the coating portion of the positive electrode 21, and a negative electrode active material is coated on the surface of a strip-shaped negative electrode foil 22A, which is used as the coating portion of the negative electrode 22. At this time, active material non-covered portions 21C and 22C that are not coated with the positive electrode active material and the negative electrode active material 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 active material non-covered portion 21C of the positive electrode and the active material non-covered portion 22C of the negative electrode are overlapped with the separator 23 in opposite directions, and are wound into a spiral shape so that a through hole 26 is formed on the central axis, and the made incision is arranged near the central axis, thereby manufacturing Figure 4 A is an electrode wound body 20.

[0085] Then, if Figure 4 As shown in FIG. 2B , the ends of a thin plate (for example, 0.5 mm thick) are pressed perpendicularly to the end faces 41 and 42 to partially bend the end faces 41 and 42 to form the groove 43. This method forms the groove 43 extending radially from the through hole 26 toward the central axis. Figure 4 The number and arrangement of the grooves 43 shown in B are only examples. Figure 4 As shown in FIG. 3 , the same pressure is applied from both sides in a direction substantially perpendicular to the end faces 41 and 42 to bend the non-active material covered portion 21C of the positive electrode and the non-active material covered portion 22C of the negative electrode so that the end faces 41 and 42 become flat surfaces. At this time, a load is applied to the plate surface of the flat plate, etc., in such a manner that the non-active material covered portions located at the end faces 41 and 42 overlap and bend toward the through hole 26. Then, the fan-shaped portion 31 of the positive electrode collector plate 24 is laser welded to the end face 41, and the fan-shaped portion 33 of the negative electrode collector plate 25 is laser welded to the end face 42.

[0086] Then, if Figure 4 As shown in D, the strip portions 32, 34 of the current collector plates 24, 25 are bent, the insulating plates 12, 13 (or insulating tapes) are attached to the positive current collector plates 24 and the negative current collector plates 25, and the electrode winding body 20 assembled as described above is inserted into the Figure 4 In the battery can 11 shown in FIG. E, the bottom of the battery can 11 is welded. 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.

[0087] Example

[0088] Hereinafter, the present invention will be specifically described based on examples in which the welding failure rate and the resistance value are compared 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.

[0089] In all the following embodiments and comparative examples, the battery size is 21700, the width of the active material covering portion 21B of the positive electrode is 59 mm, the width of the active material covering portion 22B of the negative electrode is 62 mm, and the width of the separator 23 is 64 mm. The separator 23 is overlapped in a manner covering the entire range of the active material covering portion 21B of the positive electrode and the active material covering portion 22B of the negative electrode, and the width of the active material non-covered portion of the positive electrode is 7 mm, and the width of the active material non-covered portion of the negative electrode is 4 mm. In Examples 1 to 8 and Comparative Example 1, the number of grooves 43 is set to 8, and they are arranged at approximately equal angles. In Comparative Examples 2 and 3, no grooves 43 are formed. The material of the positive electrode foil and the exposed portion of the positive collector is Al, and the material of the negative electrode foil and the exposed portion of the negative collector is Cu.

[0090] The number of windings k of the positive electrode 21 in the electrode winding body 20 is 40, and the number of windings m of the negative electrode 22 in the electrode winding body 20 is 41. Hereinafter, the portion where the positive electrode end face 41 and the positive electrode collector plate 24 are welded is referred to as the positive electrode welding point 51, and the portion where the negative electrode end face 42 and the negative electrode collector plate 25 are welded is referred to as the negative electrode welding point 52. In addition, the collection of the positive electrode welding points 51 is referred to as the positive electrode welding point group, and the collection of the negative electrode welding points 52 is referred to as the negative electrode welding point group. In the end portions 41, 42 (flat surface), welding points 51, 52 (welding point group) are formed at the position of the positive electrode collector plate 24 or the position of the negative electrode collector plate 25 corresponding to the position without the groove 43. When the shape of the welding point group is concentric or spiral, the number of times the welding point group is wound around the collector plates 24, 25 is referred to as the number of windings l of the positive electrode welding point or the number of windings n of the negative electrode welding point.

[0091] In all the examples and comparative examples except for Comparative Example 1, the number of welding points per positive electrode current collector plate 24 or per negative electrode current collector plate 25 was about 250 points. Figure 5 A to Fig. 9 A is a diagram showing a state in which the current collector plates 24 and 25 are joined by welding on the end faces 41 and 42 as viewed from the Z-axis direction, and black circles indicate welding points. Figure 5 B to Fig. 9 B is a schematic diagram of the positive electrode 21 or negative electrode 22 before winding, corresponding to A in each figure, and schematically illustrates which position of the positive electrode 21 or negative electrode 22 before winding the welding points 51 and 52 on the end faces 41 and 42 of the electrode winding body 20 correspond to. Figure 5 B to Fig. 9 The black circled or black filled areas of B represent welding points 51 , 52 or continuous welding points 51 , 52 . Figure 5 B to Fig. 9 The left side of B is the winding start side, and the right side is the winding end side.

[0092] [Example 1]

[0093] like Figure 5 As shown in A, the shape of the positive electrode welding point group is concentric, and the number of turns l of the positive electrode welding point is 7, so that k / l is 5.7. Figure 5 As shown in A, the shape of the negative electrode welding point group is made into a concentric circle shape, and the number of turns n of the negative electrode welding points is made 7, so that m / n is 5.9.

[0094] [Example 2]

[0095] like Figure 6 As shown in A, the shape of the positive electrode welding point group is made spiral, and the number of turns l of the positive electrode welding points is made 7, so that k / l is 5.7. Figure 6 As shown in A, the shape of the negative electrode welding point group is made spiral, and the winding number n of the negative electrode welding points is made 7, so that m / n is 5.9.

[0096] [Example 3]

[0097] like Figure 5 As shown in A, the shape of the positive electrode welding point group is concentric, and the number of turns l of the positive electrode welding point is 6, so that k / l is 6.7. Figure 5 As shown in A, the shape of the negative electrode welding point group is made into a concentric circle shape, and the number of turns n of the negative electrode welding points is made 6, so that m / n is 6.8.

[0098] [Example 4]

[0099] like Figure 6 As shown in A, the shape of the positive electrode welding point group is made spiral, and the number of turns l of the positive electrode welding point is made 5, so that k / l is 8.0. Figure 6 As shown in A, the shape of the negative electrode welding point group is made spiral, and the winding number n of the negative electrode welding points is made 5, so that m / n is 8.2.

[0100] [Example 5]

[0101] like Figure 5 As shown in A, the shape of the positive electrode welding point group is concentric, and the number of turns l of the positive electrode welding point is 10, so that k / l is 4.0. Figure 5As shown in A, the shape of the negative electrode welding point group is made into a concentric circle shape, and the number of turns n of the negative electrode welding points is made 10, so that m / n is 4.1.

[0102] [Example 6]

[0103] like Figure 6 As shown in A, the shape of the positive electrode welding point group is made spiral, and the number of turns l of the positive electrode welding points is set to 10, so that k / l is 4.0. Figure 6 As shown in A, the shape of the welding point group of the negative electrode is made spiral, and the winding number n of the welding points of the negative electrode is set to 10, so that m / n is 4.1.

[0104] [Example 7]

[0105] like Figure 5 As shown in A, the shape of the positive electrode welding point group is concentric, and the number of turns l of the positive electrode welding point is 11, so that k / l is 3.6. Figure 5 As shown in A, the shape of the negative electrode welding point group is made into a concentric circle shape, and the winding number n of the negative electrode welding points is made 11, so that m / n is 3.7.

[0106] [Example 8]

[0107] like Figure 6 As shown in A, the shape of the positive electrode welding point group is made spiral, and the number of turns l of the positive electrode welding points is made 11, so that k / l is 3.6. Figure 6 As shown in A, the shape of the negative electrode welding point group is made spiral, and the winding number n of the negative electrode welding points is made 11, so that m / n is 3.7.

[0108] [Comparative Example 1]

[0109] Make the shape of the positive electrode welding point group as Figure 7 A shows a radial shape, so that the shape of the negative electrode welding point group is as follows Figure 7 A shows radial shape.

[0110] [Comparative Example 2]

[0111] like Figure 8 As shown in A, the shape of the positive electrode welding point group is concentric, and the number of turns l of the positive electrode welding point is 7, so that k / l is 5.7. Figure 8 As shown in A, the shape of the negative electrode welding point group is made into a concentric circle shape, and the number of turns n of the negative electrode welding points is made 7, so that m / n is 5.9.

[0112] [Comparative Example 3]

[0113] like Fig. 9As shown in A, the shape of the positive electrode welding point group is made spiral, and the number of turns l of the positive electrode welding points is made 7, so that k / l is 5.7. Fig. 9 As shown in A, the shape of the negative electrode welding point group is made spiral, and the winding number n of the negative electrode welding points is made 7, so that m / n is 5.9.

[0114] [evaluate]

[0115] Regarding the above examples, a battery 1 was made for each example and evaluated. Laser welding of the end face 41 of the positive electrode and the positive electrode collector plate 24 was performed, and the number of points where openings or sputtering or other poor welding occurred on the collector plate 24 was visually counted after welding, and the ratio was used as the poor welding rate of the positive electrode. The negative electrode side was also counted in the same way as the poor welding rate of the negative electrode. In addition, the internal resistance (DC resistance DCR and AC resistance ACR) of the battery 1 was measured. The DC resistance DCR is obtained by calculating the slope of the voltage when the discharge current rises from 0 (A) to 100 (A) within 5 seconds. The AC resistance ACR is obtained by measuring at 1kHz. The results are shown in Table 1.

[0116] [Table 1]

[0117]

[0118] In Examples 1 to 8, the welding defect rate of the positive electrode is 1.0% or less, the welding defect rate of the negative electrode is 2.0% or less, the resistance value ACR is 4.1 mΩ or less, and the resistance value DCR is 8.2 mΩ or less. In contrast, in Comparative Examples 1 to 3, the values ​​are higher than the upper limit values ​​of Examples 1 to 8. In Examples 1 to 8, Figure 5 B and Figure 6 As shown in FIG. 2B , in the active material non-covered portion 21C of the positive electrode and the active material non-covered portion 22C of the negative electrode, the welding points 51 and 52 exist in substantially the entire area, so that welding can be performed uniformly. In contrast, in Comparative Example 1, as shown in FIG. Figure 7 As shown in B, the interval between the welding points 51 and 52 gradually increases toward the winding end side, and the arrangement of the welding points 51 and 52 is uneven. Figure 8 B and Fig. 9As shown in Figure 1, the intervals between the welding points 51 and 52 are roughly random, and the arrangement of the welding points 51 and 52 is uneven. Therefore, when there are grooves 43 on the end faces 41 and 42, when the shape of the welding point group is concentric or spiral, the value of the internal resistance of the battery is low, and it can be judged that the collector plates 24 and 25 and the end faces 41 and 42 can be stably welded. In addition, it can be seen from Table 1 that in Examples 1 to 8, 3.6≤k / l≤8.0 and 3.7≤m / n≤8.2, so the value of the internal resistance is low at this time, and it can be judged that the collector plate and the end face can be stably welded.

[0119] <2. Modifications>

[0120] 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.

[0121] In the embodiment and the comparative example, the number of the grooves 43 is 8, but it may be any other number. The battery size is 21700, but it may be 18650 or any other size.

[0122] The positive electrode current collecting plate 24 and the negative electrode current collecting plate 25 include the fan-shaped fan-shaped portions 31 and 33 , but may have other shapes.

[0123] As long as it does not deviate from the main purpose of the present invention, the present invention can also be applied to other batteries other than lithium-ion batteries, and batteries other than cylindrical ones (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.

[0124] <3. Application examples>

[0125] (1) Battery pack

[0126] Fig.10 This is a block diagram showing an example of a circuit structure when a 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 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 perform charge and discharge control in the event of abnormal heating, or 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 for charging and discharging.

[0127] The battery pack 301 is formed by connecting a plurality of secondary batteries 301a in series and / or in parallel. Figure 4, 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.

[0128] The temperature detection unit 318 is connected to the temperature detection element 308 (e.g., thermistor), measures the temperature of the battery pack 301 or the battery pack 300, and supplies 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 supplies it to the control unit 310. The current measurement unit 313 measures the current using the current detection resistor 307, and supplies the measured current to the control unit 310.

[0129] 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 close the switch unit 304, thereby preventing overcharging or overdischarging.

[0130] 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. Figure 4 In the embodiment, the switch section 304 is provided on the + side, but may be provided on the - side.

[0131] 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 .

[0132] (2) Electronic equipment

[0133] The secondary battery 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.

[0134] Examples of electronic devices include notebook personal computers, smart phones, tablet terminals, PDAs (portable information terminals), mobile phones, wearable terminals, digital 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 can also be included in the electronic devices in a broad sense.

[0135] As electric transport equipment, electric vehicles (including hybrid vehicles), electric motorcycles, electric power-assisted bicycles, electric buses, electric carts, unmanned guided vehicles (AGVs), railway vehicles, etc. can be listed. In addition, electric passenger aircraft and electric unmanned aircraft 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.

[0136] 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.

[0137] (3) Power tools

[0138] Reference Fig.11 , an example of an electric screwdriver as an electric tool to which the present invention can be applied 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 according to the present invention are housed in a frame below the handle of the electric screwdriver 431. The battery pack 430 is built into the electric screwdriver 431 or can be freely attached and detached.

[0139] The battery pack 430 and the motor control unit 435 each include 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 cut off the power supply to the motor 433 in the event of an abnormality such as overdischarge.

[0140] (4) Power storage systems for electric vehicles

[0141] 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. The 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 power driving force conversion device.

[0142] 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 secondary batteries of the present invention can be applied.

[0143] 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 can be stored in the battery 608 by the rotational force generated by the engine 601. Various sensors 610 control the engine speed via the vehicle control device 609, or control the opening of the throttle valve (not shown).

[0144] 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. 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).

[0145] It should be noted that the secondary battery according to 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 wheels 604 and 605 .

[0146] The above description is based on 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. In addition, 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.

[0147] Explanation of symbols

[0148] 1…lithium-ion battery, 12…insulating plate, 21…positive electrode, 21A…positive electrode foil, 21B…positive electrode active material layer, 21C…active material non-covered portion of the positive electrode, 22…negative electrode, 22A…negative electrode foil, 22B…negative electrode active material layer, 22C…active material non-covered portion of the negative electrode, 23…separator, 24…positive electrode current collector plate, 25…negative electrode current collector plate, 26…through hole, 27, 28…outer edge portion, 41, 42…end surface, 43…groove, 51…positive electrode welding point, 52…negative electrode welding point.

Claims

1. A secondary battery, The secondary battery contains an electrode winding body, a positive electrode collector plate, and a negative electrode collector plate in a battery can. The electrode winding body has a structure in which a strip-shaped positive electrode and a strip-shaped negative electrode are stacked and wound with a separator interposed therebetween. The positive electrode has a 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. The negative electrode has a 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. 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. 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. The secondary battery has: A flat surface formed by bending and overlapping 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 A groove is formed in the flat surface, A group of welding points exists at a position of the positive electrode current collector plate or a position of the negative electrode current collector plate corresponding to a position without the groove in the flat surface, The shape of the welding point group is spiral, not radial.

2. An electronic device, A secondary battery according to claim 1.

3. An electric tool, A secondary battery according to claim 1.

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