Secondary battery, electronic device, and power tool

Abstract

A problem is to improve current collection efficiency.　Provided is a secondary battery in which a positive electrode current collector plate and a negative electrode current collector plate each have a group of welded portions formed radially, a positive electrode active material uncoated portion includes a first welded portion closest to the winding end portion of a positive electrode foil and a second welded portion close to the winding end portion next to the first welded portion, a negative electrode active material uncoated portion includes a third welded portion closest to the winding end portion of a negative electrode foil and a fourth welded portion close to the winding end portion next to the third welded portion, and where the distance from the winding end portion of the positive electrode foil to the first welded portion is LC1 (mm), the distance from the first welded portion to the second welded portion is LC2 (mm), the distance from the winding end portion of the negative electrode foil to the third welded portion is LA1 (mm), and the distance from the third welded portion to the fourth welded portion is LA2 (mm), the following formulas (1) and (2) are satisfied. Formula (1): 0≤LC1≤LC2, Formula (2): 0≤LA1≤LA2

Description

Technical Field

[0001] The present invention relates to secondary batteries, electronic devices, and power tools.

Background Art

[0002] One type of secondary battery, the lithium-ion battery, has come to be developed for applications requiring high output, such as power tools and automobiles. One method of achieving high output is high-rate discharge, in which a relatively large current is passed through the battery. In high-rate discharge, since a large current is passed, it is desirable to lower the internal resistance of the battery. For example, Patent Document 1 below describes a secondary battery having a structure in which a notch is provided on the outer periphery of the negative electrode current collector, and the position of the end portion at the end of winding of the negative electrode current collector plate is aligned with the notch.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Applying the technique described in Patent Document 1 to a lithium-ion battery having a tabless structure (a structure without tabs for leading out the output of the battery) may reduce the reaction area of the electrodes, thus possibly degrading the battery performance. Further, in the secondary battery of Patent Document 1, viewpoints such as the relationship between the end portion at the end of winding of the current collector and the joining portion (specifically, the welding portion) and improvement of the current collection efficiency based on such relationship were lacking.

[0005] Therefore, an object of the present invention is to provide a secondary battery with improved current collection efficiency, an electronic device using the secondary battery, and a power tool.

Means for Solving the Problems

[0006] The present invention relates to a secondary battery in which a strip-shaped positive electrode and a strip-shaped negative electrode are laminated via a separator, and a positive electrode current collector plate and a negative electrode current collector plate are housed in a battery can, The positive electrode has a positive electrode active material coated portion coated with a positive electrode active material layer and a positive electrode active material non-coated portion on a strip-shaped positive electrode foil, The negative electrode has a negative electrode active material coated portion coated with a negative electrode active material layer and a negative electrode active material non-coated portion extending in the longitudinal direction of the negative electrode foil on a strip-shaped negative electrode foil, The positive electrode active material non-coated portion is welded to the positive electrode current collector plate on one end face of the electrode wound body, The negative electrode active material non-coated portion is welded to the negative electrode current collector plate on the other end face of the electrode wound body, The positive electrode current collector plate and the negative electrode current collector plate each have a group of welded portions formed radially, At least one of the positive electrode current collector plate and the negative electrode current collector plate Based on a predetermined welding part located at the outermost periphery of the electrode winding body in a predetermined group of welding parts, the interval from the predetermined welding part to an adjacent welding part along the winding direction of the electrode winding body and the interval from the predetermined welding part to an adjacent welding part along the direction opposite to the winding direction are different. For the predetermined group of welding parts has a portion where the intervals of the two groups of welded portions each are different, The positive electrode active material non-coated portion has a first welded portion closest to the end portion where winding of the positive electrode foil ends, and a second welded portion next to the first welded portion and close to the end portion where winding ends, The negative electrode active material non-coated portion has a third welded portion closest to the end portion where winding of the negative electrode foil ends, and a fourth welded portion next to the third welded portion and close to the end portion where winding ends, When the distance from the end portion where winding of the positive electrode foil ends to the first welded portion is LC1 (mm), and the distance from the first welded portion to the second welded portion is LC2 (mm), When the distance from the end portion where winding of the negative electrode foil ends to the third welded portion is LA1 (mm), and the distance from the third welded portion to the fourth welded portion is LA2 (mm), it is a secondary battery that satisfies the following formulas (1) and (2). 0 ≦ LC1 ≦ LC2 ··· (1) 0 ≦ LA1 ≦ LA2 ··· (2)

Advantages of the Invention

[0007] According to at least one embodiment of the present invention, the current collection efficiency of a secondary battery can be improved. Note that the content of the present invention is not limited to the effects exemplified in this specification.

Brief Description of the Drawings

[0008]

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Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The description will be made in the following order. <One Embodiment> <Modification Example> <Application Example> The embodiments and the like described below are preferred specific examples of the present invention, and the content of the present invention is not limited to these embodiments and the like. Note that, in order to facilitate understanding of the description, in some of the drawings, a part of the configuration may be enlarged, emphasized, or reduced, or some of the illustrations may be simplified.

[0010] <One Embodiment> [Configuration Example of Lithium-Ion Battery] In an embodiment of the present invention, a cylindrical lithium-ion battery will be described as an example of the secondary battery. With reference to FIGS. 1 to 9, a configuration example of a lithium-ion battery (lithium-ion battery 1) according to an embodiment will be described. FIG. 1 is a schematic cross-sectional view of the lithium-ion battery 1. The lithium-ion battery 1 is, for example, a cylindrical lithium-ion battery 1 in which an electrode wound body 20 is housed inside a battery can 11 as shown in FIG. 1. In the following description, unless otherwise specified, the horizontal direction toward the paper surface of FIG. 1 is the X-axis direction, the depth direction is the Y-axis direction, and the vertical direction (the extending direction of the central axis of the lithium-ion battery 1 (also appropriately referred to as the winding axis, the axis indicated by the dashed line in FIG. 1)) is appropriately referred to as the Z-axis direction.

[0011] The lithium-ion battery 1 generally has a cylindrical battery can 11, and includes a pair of insulating plates 12 and 13 and an electrode wound body 20 inside the battery can 11. The lithium-ion battery 1 may further include, for example, any one or two or more of a thermal sensing resistor (PTC) element and a reinforcing member inside the battery can 11.

[0012] (Battery can) The battery can 11 is mainly a member for housing the electrode wound 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 of metal materials such as iron, aluminum, and their alloys. The surface of the battery can 11 may be plated with any one or two or more of metal materials such as nickel.

[0013] (Insulating plate) The insulating plates 12 and 13 are disk-shaped plates having a surface substantially perpendicular to the central axis of the electrode wound body 20 (the direction parallel to the Z-axis in FIG. 1 passing through the approximate center of the end face of the electrode wound body 20). Further, the insulating plates 12 and 13 are arranged, for example, so as to sandwich the electrode wound body 20 with each other.

[0014] (Crimping structure) On the open end face 11N of the battery can 11, a battery lid 14 and a safety valve mechanism 30 are caulked via a gasket 15, and a caulking structure 11R (crimp structure) is formed. Thereby, in a state where an electrode winding body 20 etc. are housed inside the battery can 11, the battery can 11 is sealed.

[0015] (Battery lid) The battery lid 14 is mainly a member that closes the open end face 11N of the battery can 11 in a state where an electrode winding body 20 etc. are housed inside the battery can 11. This battery lid 14 contains, for example, the same material as the forming material of the battery can 11. The central region of the battery lid 14 protrudes, for example, in the +Z direction. Thereby, regions other than the central region (peripheral regions) of the battery lid 14 are in contact with, for example, the safety valve mechanism 30.

[0016] (Gasket) The gasket 15 is mainly a member that seals the gap between the bent portion 11P of the battery can 11 and the battery lid 14 by being interposed therebetween. For example, asphalt etc. may be applied to the surface of the gasket 15.

[0017] The gasket 15 contains, for example, any one type or two or more types of insulating materials. The type of insulating material is not particularly limited, but for example, polymer materials such as polybutylene terephthalate (PBT) and polypropylene (PP) can be used. Among them, as the insulating material, polybutylene terephthalate is preferable. This is because the gap between the bent portion 11P and the battery lid 14 can be sufficiently sealed while electrically separating the battery can 11 and the battery lid 14 from each other.

[0018] (Safety valve mechanism) The safety valve mechanism 30 mainly releases the internal pressure of the battery can 11 by releasing the sealed state of the battery can 11 as needed when the internal pressure (inner pressure) of the battery can 11 rises. The cause of the increase in the internal pressure of the battery can 11 is, for example, gas generated due to the decomposition reaction of the electrolytic solution during charge and discharge.

[0019] (Electrode wound body) In the cylindrical lithium-ion battery 1, the strip-shaped positive electrode 21 and the strip-shaped negative electrode 22 are laminated with the separator 23 interposed therebetween, and are wound in a spiral shape and impregnated with the electrolytic solution, and are housed in the battery can 11. The positive electrode 21 is formed by forming a positive electrode active material layer 21B on one or both sides of the positive electrode foil 21A. 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 the negative electrode foil 22A. The material of the negative electrode foil 22A is, for example, a metal foil made of nickel, a nickel alloy, copper, or a copper alloy. The separator 23 is a porous and insulating film, which enables the movement of substances such as ions and electrolytic solution while electrically insulating the positive electrode 21 and the negative electrode 22.

[0020] FIG. 2A is a front view of the positive electrode 21 before winding, and FIG. 2B is a side view of the positive electrode 21 in FIG. 2A. The positive electrode 21 has a portion (the portion marked with dots) covered with the positive electrode active material layer 21B on one main surface and the other main surface of the positive electrode foil 21A, and also has a positive electrode active material non-covered portion 21C which is a portion not covered with the positive electrode active material layer 21B. In the following description, the portion covered with the positive electrode active material layer 21B is appropriately referred to as the positive electrode active material covered portion 21B. Also, a configuration in which the positive electrode active material covered portion 21B is provided on one main surface of the positive electrode foil 21A may be adopted. Further, in the present embodiment, an insulating layer 101 (the portion shown in gray in FIGS. 2A and 2B) is provided between the positive electrode active material covered portion 21B and the positive electrode active material non-covered portion 21C.

[0021] FIG. 3A is a front view of the negative electrode 22 before winding, and FIG. 3B is a side view of the negative electrode 22 of FIG. 3A. The negative electrode 22 has a portion (the dotted portion) coated with the negative electrode active material layer 22B on one main surface and the other main surface of the negative electrode foil 22A, and also has a negative electrode active material non-coated portion 22C which is a portion not coated with the negative electrode active material layer 22B. In the following description, the portion coated with the negative electrode active material layer 22B is appropriately referred to as the negative electrode active material coated portion 22B. Also, the negative electrode active material coated portion 22B may be provided on one main surface of the negative electrode foil 22A.

[0022] As shown in FIG. 3A, the negative electrode active material non-coated portion 22C has, for example, a first negative electrode active material non-coated portion 221A extending in the longitudinal direction (X-axis direction in FIG. 3) of the negative electrode 22, a second negative electrode active material non-coated portion 221B extending in the short-side direction (Y-axis direction in FIG. 3; also appropriately referred to as the width direction) of the negative electrode 22 on the winding start side of the negative electrode 22, and a third negative electrode active material non-coated portion 221C extending in the short-side direction (Y-axis direction in FIG. 3) of the negative electrode 22 on the winding end side of the negative electrode 22. In FIG. 3A, dotted lines are attached to each of the boundary between the first negative electrode active material non-coated portion 221A and the second negative electrode active material non-coated portion 221B, and the boundary between the first negative electrode active material non-coated portion 221A and the third negative electrode active material non-coated portion 221C.

[0023] In the cylindrical lithium-ion battery 1 according to the present embodiment, the electrode wound body 20 is wound with the positive electrode active material non-coated portion 21C and the first negative electrode active material non-coated portion 221A facing each other in opposite directions with the separator 23 interposed therebetween.

[0024] A through hole 26 is provided at the center of the electrode wound body 20. Specifically, the through hole 26 is a hole formed substantially at the center of the laminate in which the positive electrode 21, the negative electrode 22, and the separator 23 are laminated. The through hole 26 is used as a hole for inserting a rod-shaped welding tool (hereinafter, appropriately referred to as a welding rod) or the like in the assembling process of the lithium-ion battery 1.

[0025] Details of the electrode winding body 20 will be described. FIG. 4 shows an example of the structure before winding in which the positive electrode 21, the negative electrode 22, and the separator 23 are laminated. The positive electrode 21 further has an insulating layer 101 (the gray region portion in FIG. 4) that covers the boundary between the positive electrode active material coated portion 21B (the portion with sparse dots in FIG. 4) and the positive electrode active material non-coated portion 21C. The length of the insulating layer 101 in the width direction is, for example, about 3 mm. All regions of the positive electrode active material non-coated portion 21C facing the negative electrode active material coated portion 22B via the separator 23 are covered with the insulating layer 101. The insulating layer 101 has the effect of reliably preventing an internal short circuit of the lithium ion battery 1 when foreign matter enters between the negative electrode active material coated portion 22B and the positive electrode active material non-coated portion 21C. Further, the insulating layer 101 has the effect of absorbing an impact when an impact is applied to the lithium ion battery 1, reliably preventing the positive electrode active material non-coated portion 21C from being bent or short-circuiting with the negative electrode 22.

[0026] Here, as shown in FIG. 4, let the length of the positive electrode active material non-coated portion 21C in the width direction be D5, and the length of the first negative electrode active material non-coated portion 221A in the width direction be D6. In one embodiment, it is preferable that D5 > D6. For example, D5 = 7 (mm) and D6 = 4 (mm). When the length of the portion where the positive electrode active material non-coated portion 21C protrudes from one end in the width direction of the separator 23 is D7, and the length of the portion where the first negative electrode active material non-coated portion 221A protrudes from the other end in the width direction of the separator 23 is D8, in one embodiment, it is preferable that D7 > D8. For example, D7 = 4.5 (mm) and D8 = 3 (mm).

[0027] The positive electrode foil 21A and the non-coated portion 21C of the positive electrode active material are made of, for example, aluminum, and the negative electrode foil 22A and the non-coated portion 22C of the negative electrode active material are made of, for example, copper. Thus, generally, the non-coated portion 21C of the positive electrode active material is softer (has a lower Young's modulus) than the non-coated portion 22C of the negative electrode active material. Therefore, in one embodiment, it is more preferable that D5 > D6 and D7 > D8. In this case, when the non-coated portion 21C of the positive electrode active material and the non-coated portion 22C of the negative electrode active material are bent simultaneously from both electrode sides with the same pressure, the height measured from the tip of the separator 23 at the bent portion may be approximately the same for the positive electrode 21 and the negative electrode 22. At this time, since the non-coated portion 21C of the positive electrode active material is bent and overlaps appropriately, in the manufacturing process of the lithium-ion battery 1 (details will be described later), the joining by laser welding between the non-coated portion 21C of the positive electrode active material and the positive electrode current collector 24 can be easily performed. Also, since the non-coated portion 22C of the negative electrode active material is bent and overlaps appropriately, in the manufacturing process of the lithium-ion battery 1, the joining by laser welding between the non-coated portion 22C of the negative electrode active material and the negative electrode current collector 25 can be easily performed.

[0028] (Current collector) In a normal lithium-ion battery, for example, current extraction leads are welded one by one to the positive electrode and the negative electrode. However, in this case, the internal resistance of the battery is large, and the lithium-ion battery generates heat and becomes hot during discharge, so it is not suitable for high-rate discharge. Therefore, in the lithium-ion battery 1 of this embodiment, the positive electrode current collector 24 is disposed on the end face 41 which is one end face of the electrode winding body 20, and the negative electrode current collector 25 is disposed on the end face 42 which is the other end face of the electrode winding body 20. Then, by welding the positive electrode current collector 24 and the non-coated portion 21C of the positive electrode active material existing on the end face 41 at multiple points, and also welding the negative electrode current collector 25 and the non-coated portion 22C of the negative electrode active material (specifically, the first non-coated portion 221A of the negative electrode active material) existing on the end face 42 at multiple points, the internal resistance of the lithium-ion battery 1 is kept low, enabling high-rate discharge.

[0029] Figures 5A and 5B show an example of a current collector plate. Figure 5A is the positive electrode current collector plate 24, and Figure 5B is the negative electrode current collector plate 25. The positive electrode current collector plate 24 and the negative electrode current collector plate 25 are housed in the battery can 11 (see Figure 1). The material of the positive electrode current collector plate 24 is, for example, a metal plate made of a single or composite material of aluminum or an aluminum alloy, and the material of the negative electrode current collector plate 25 is, for example, a metal plate made of a single or composite material of nickel, a nickel alloy, copper, or a copper alloy. As shown in Figure 5A, the shape of the positive electrode current collector plate 24 is a shape with a flat fan-shaped portion 31 (an example of a positive electrode side fan-shaped portion) and a rectangular strip portion 32 (an example of a positive electrode side strip portion) attached to the upper part. There is a hole 35 near the center of the fan-shaped portion 31, and the position of the hole 35 corresponds to the position of the through hole 26.

[0030] The portion indicated by the dots in Figure 5A is an insulating portion 32A where an insulating tape is attached or an insulating material is applied to the strip portion 32, and the portion below the dot portion in the drawing is a connection portion 32B to a sealing plate that also serves as an external terminal. In the case of a battery structure that does not have a metal center pin (not shown) in the through hole 26, since the strip portion 32 is less likely to come into contact with the negative potential portion, the insulating portion 32A may not be necessary. In that case, the width of the positive electrode 21 and the negative electrode 22 can be increased by an amount corresponding to the thickness of the insulating portion 32A to increase the charge and discharge capacity.

[0031] The shape of the negative electrode current collector plate 25 is almost the same as that of the positive electrode current collector plate 24, but the shape of the strip portion is different. The strip portion 34 (an example of a negative electrode side strip portion) of the negative electrode current collector plate in Fig. 5B is shorter than the strip portion 32 of the positive electrode current collector plate 24, and there is no portion corresponding to the insulating portion 32A. The strip portion 34 is provided with round protrusions (projections) 37 indicated by a plurality of circles. During resistance welding, the current concentrates on the protrusions 37, the protrusions 37 melt, and the strip portion 34 is welded to the bottom of the battery can 11. Similar to the positive electrode current collector plate 24, the negative electrode current collector plate 25 has a hole 36 near the center of the fan-shaped portion 33 (an example of a negative electrode side fan-shaped portion), and the position of the hole 36 corresponds to the position of the through hole 26. Since the fan-shaped portions 31 of the positive electrode current collector plate 24 and 33 of the negative electrode current collector plate 25 are fan-shaped, they cover a part of the end faces 41, 42. By not covering all of them, when assembling the lithium-ion battery 1, the electrolytic solution can smoothly penetrate into the electrode winding body 20, and when the lithium-ion battery 1 is in an abnormal high-temperature state or overcharged state, the gas generated can be easily released outside the lithium-ion battery 1.

[0032] (Positive electrode) The positive electrode active material layer 21B contains at least a positive electrode material (positive electrode active material) capable of occluding and releasing lithium, and may further contain a positive electrode binder, a positive electrode conductive agent, and the like. 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 spinel type crystal structure. The lithium-containing phosphate compound has, for example, an olivine type crystal structure.

[0033] The positive electrode binder contains a synthetic rubber or a polymer compound. The synthetic rubber is styrene-butadiene rubber, fluorine rubber, ethylene propylene diene, etc. The polymer compound is polyvinylidene fluoride (PVdF), polyimide, etc.

[0034] The positive electrode conductive agent is a carbon material such as graphite, carbon black, acetylene black, or ketjen black. However, the positive electrode conductive agent may also be a metal material or a conductive polymer.

[0035] (Negative electrode) The surface of the negative electrode foil 22A constituting the negative electrode 22 is preferably roughened to improve the adhesion with the negative electrode active material layer 22B. The negative electrode active material layer 22B contains at least a negative electrode material (negative electrode active material) capable of occluding and releasing lithium, and may further contain a negative electrode binder, a negative electrode conductive agent, and the like.

[0036] 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 shape of the carbon material has a fibrous, spherical, granular, or flaky shape.

[0037] In addition, the negative electrode material includes, for example, a metal-based material. Examples of the metal-based material include Li (lithium), Si (silicon), Sn (tin), Al (aluminum), Zr (zinc), Ti (titanium). The metal-based element forms a compound, mixture, or alloy 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).

[0038] (Separator) The separator 23 is a porous film containing a resin, and may be a laminated film of two or more types of porous films. The resin is polypropylene, polyethylene, and the like. The separator 23 may contain a resin layer on one or both sides thereof with the porous film as a base layer. This is because the adhesion of the separator 23 to each of the positive electrode 21 and the negative electrode 22 is improved, suppressing the distortion of the electrode winding body 20.

[0039] The resin layer contains a resin such as PVdF. When forming this resin layer, a solution in which the resin is dissolved in an organic solvent is applied to the base material layer, and then the base material layer is dried. Alternatively, the base material layer may be immersed in the solution and then dried. It is preferable from the viewpoints of heat resistance and improvement of battery safety that the resin layer contains inorganic particles or organic particles. Examples of the inorganic particles include aluminum oxide, aluminum nitride, aluminum hydroxide, magnesium hydroxide, boehmite, talc, silica, mica, and the like. Further, instead of the resin layer, a surface layer mainly composed of inorganic particles formed by a sputtering method, an ALD (atomic layer deposition) method, or the like may be used.

[0040] (Electrolyte solution) The electrolyte solution contains a solvent and an electrolyte salt, and may further contain additives or the like as necessary. The solvent is a non-aqueous solvent such as an organic solvent or water. An electrolyte solution containing a non-aqueous solvent is called a non-aqueous electrolyte solution. Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, lactones, chain carboxylic acid esters, or nitriles (mononitriles).

[0041] Typical examples of the electrolyte salt are lithium salts, but salts other than lithium salts may also be included. Examples of the lithium salts include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium methanesulfonate (LiCH 3 SO 3 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), dilithium hexafluorosilicate (Li 2 SF 6 ), and the like. These salts can also be used in combination. Among them, it is preferable from the viewpoint of improving battery characteristics to use a mixture of LiPF 6 and LiBF 4 . The content of the electrolyte salt is not particularly limited, but is preferably 0.3 mol / kg to 3 mol / kg with respect to the solvent.

[0042] (Welding structure) Next, an example of the welding structure in the lithium-ion battery 1 having the above-described configuration will be described. In the lithium-ion battery 1, the positive electrode active material non-coated portion 21C is exposed on the end face 41 of the electrode winding body 20 having a substantially cylindrical shape, and the first negative electrode active material non-coated portion 221A is exposed on the end face 42. The side where the positive electrode active material non-coated portion 21C is exposed on the end face 41 is appropriately referred to as the positive electrode side of the electrode winding body 20. The side where the first negative electrode active material non-coated portion 221A is exposed on the end face 42 is referred to as the negative electrode side of the electrode winding body 20.

[0043] In the manufacturing process of the lithium-ion battery 1, the positive electrode active material non-coated portion 21C exposed on the end face 41 is bent. FIG. 6 is a partially enlarged cross-sectional view of the positive electrode side of the electrode winding body 20. As shown in FIG. 6, by bending the positive electrode active material non-coated portion 21C so as to overlap in layers, a flat surface 71 (an example of a positive electrode side flat surface), which is a substantially flat surface, is formed. The positive electrode current collector plate 24 is joined to the flat surface 71 by laser welding or the like. For example, while the output of the laser beam Lbm is kept constant, the flat surface 71 and the positive electrode current collector plate 24 are welded by irradiating the other main surface 24A with the laser beam Lbm in a state where one main surface of the fan-shaped portion 31 of the positive electrode current collector plate 24 faces and contacts the flat surface 71.

[0044] FIG. 7 is a view showing the positive electrode current collector plate 24 after laser welding. Specifically, the fan-shaped portion 31 of the positive electrode current collector plate 24 is irradiated with the laser beam Lbm. The laser welding is performed, for example, by continuous irradiation in which the irradiation position is changed from the vicinity of the periphery of the hole 35 toward the outside while keeping the output of the laser beam Lbm constant. As a result, a welding portion group 81 including a plurality of welding portions is formed. Here, the welding portion means a portion where the flat surface 71 and the positive electrode current collector plate 24 are welded, and is schematically indicated by ○ in FIGS. 7, 9, etc. The positive electrode current collector plate 24 according to the present embodiment has a welding portion group 81 formed radially. Radially means a mode extending in all directions from the starting point (in this example, the center of the hole 35), and is shown by a line passing through the centers of the holes 35 and 36 in FIGS. 7, 9, etc. For example, as shown in FIG. 7, the positive electrode current collector plate 24 has six welding portion groups 81.

[0045] Also, in the manufacturing process of the lithium-ion battery 1, the first non-coated portion 221A of the negative electrode active material exposed on the end face 41 is bent. FIG. 8 is an enlarged partial cross-sectional view of the negative electrode side of the electrode winding body 20. As shown in FIG. 8, by bending the first non-coated portion 221A of the negative electrode active material so that they overlap in layers, a flat surface 72 (an example of a negative electrode side flat surface), which is a substantially flat surface, is formed. The negative electrode current collector plate 25 is joined to the flat surface 72 by laser welding or the like. For example, while the output of the laser beam Lbm is kept constant, the flat surface 72 and the negative electrode current collector plate 25 are welded by irradiating the other main surface 25A with the laser beam Lbm in a state where one main surface of the fan-shaped portion 33 of the negative electrode current collector plate 25 faces and contacts the flat surface 72.

[0046] FIG. 9 is a view showing the negative electrode current collector plate 25 after laser welding. Specifically, the fan-shaped portion 33 of the negative electrode current collector plate 25 is irradiated with the laser beam Lbm. The laser welding is performed, for example, by continuous irradiation in which the irradiation position is changed from the vicinity of the periphery of the hole 36 toward the outside while keeping the output of the laser beam Lbm constant. As a result, a weld portion group 82 including a plurality of weld portions is formed. The negative electrode current collector plate 25 according to the present embodiment has a weld portion group 82 formed radially. For example, as shown in FIG. 9, the negative electrode current collector plate 25 has six weld portion groups 82.

[0047] Note that the "flat surface" in this specification means not only a completely flat surface but also a surface having some irregularities and surface roughness to such an extent that the non-coated portion 21C of the positive electrode active material and the positive electrode current collector plate 24, and the first non-coated portion 221A of the negative electrode active material and the negative electrode current collector plate 25 can be joined.

[0048] Incidentally, in order to efficiently charge and discharge the lithium-ion battery 1, it is important to arrange more current collecting points, that is, welding parts, through which electrons can enter and exit from the positive electrode active material coating part 21B, and to arrange the welding parts evenly with respect to the electrode reaction area, thereby reducing the resistance when electrons move. However, the structure of the lithium-ion battery 1 according to the present embodiment has a structure in which the strip-shaped positive electrode 21 and the strip-shaped negative electrode 22 are wound in a spiral shape. Therefore, in order to arrange the welding parts evenly, the welding parts must be arranged randomly. Random arrangement of the welding parts will significantly increase the welding time, deteriorate productivity, etc., and lead to cost increase. Therefore, it is desirable that the welding parts be arranged in a continuous line shape including a straight line or an R part. Further, the positive electrode current collector plate 24 is provided with a strip-shaped part 32 that is electrically connected to the sealing body, and has a shape in which the weldable area is limited. Similarly, the negative electrode current collector plate 25 also has a strip-shaped part 34 that is electrically connected to the bottom of the battery can 11, and has a shape in which the weldable area is limited, similar to the positive electrode 21. Such a point also needs to be considered.

[0049] Based on the above points, the position of the welding part with good current collection efficiency was considered. As a result, it was found that if the position of the welding part near the end of winding is not defined, the even balance of current collection will be greatly disrupted, which will cause deterioration of characteristics. In the present embodiment, by defining the positional relationship between the end of winding and the welding part, the current collection efficiency is improved, enabling a high-output secondary battery with a small internal resistance. The following will specifically describe it.

[0050] FIG. 10A is a view of the non-coated positive electrode active material part 21C exposed on the end face 41 as viewed from the -Z direction. FIG. 10B is a view showing the positive electrode current collector plate 24 laser-welded to the non-coated positive electrode active material part 21C shown in FIG. 10A superimposed thereon. As shown in FIG. 10A, the wound positive electrode 21 has a start end S1 of winding and an end end F1 of winding. FIGS. 11A and 11B are the same as FIGS. 10A and 10B except that the positions of the start end S1 of winding and the end end F1 of winding are different, and the illustrated contents are the same.

[0051] Here, when viewed along the direction opposite to the winding direction (the direction indicated by the arrow in FIG. 10A) starting from the end portion F1 of the winding end, the welding portion closest to the end portion F1 of the winding end is appropriately referred to as the first welding portion 81A, and the welding portion next closest to the end portion F1 of the winding end after the welding portion 81A is appropriately referred to as the second welding portion 81B. FIGS. 10A and 10B show an example where the first welding portion 81A is far from the end portion F1 of the winding end. Specifically, it is an example where the distance from the end portion F1 of the winding end to the first welding portion 81A (hereinafter, this distance is appropriately referred to as LC1 (unit: mm)) is larger than the distance from the first welding portion 81A to the second welding portion 81B (hereinafter, this distance is appropriately referred to as LC2 (unit: mm)). FIGS. 11A and 11B show an example where the first welding portion 81A is close to the end portion F1 of the winding end, specifically, an example where LC1 < LC2.

[0052] FIG. 12 is a diagram in which the positive electrode 21 after laser welding is virtually developed, and is a diagram corresponding to FIGS. 10A and 10B. Further, FIG. 13 is a diagram in which the positive electrode 21 after laser welding is virtually developed, and is a diagram corresponding to FIGS. 11A and 11B. As schematically shown in FIG. 12, since the first welding portion 81A is far from the end portion F1 of the winding end, the distance (the distance indicated by the arrow) for extracting the electron EL becomes large and the current collection efficiency decreases. On the other hand, if the first welding portion 81A can be provided at a position close to the end portion F1 of the winding end, as schematically shown in FIG. 13, since the first welding portion 81A is close to the end portion F1 of the winding end, the distance (the distance indicated by the arrow) for extracting the electron EL becomes small and the current collection efficiency improves.

[0053] Note that, as described above, the first welding portion 81A and the second welding portion 81B are formed on the flat surface 71. In the description of FIGS. 10 to 13, for the sake of easy understanding, the state before the flat surface 71 is formed is used for the description. Among the welding portions formed on the flat surface 71, when viewed along the direction opposite to the winding direction, the welding portion closest to the end portion F1 of the winding end corresponds to the first welding portion 81A, and the welding portion next closest to the end portion F1 of the winding end after the welding portion 81A corresponds to the second welding portion 81B.

[0054] The same can be said for the negative electrode 22. That is, as shown in FIG. 14, the starting end of the winding of the negative electrode 22 is designated as S2, and the ending end of the winding of the negative electrode 22 is designated as F2. When viewed along the direction opposite to the winding direction starting from the ending end F2, the welding part closest to the ending end F2 is appropriately referred to as the third welding part 82A, and the welding part next closest to the ending end F2 after the welding part 82A is appropriately referred to as the fourth welding part 82B. Also in this case, similar to the positive electrode 21, by bringing the position of the third welding part 82A closer to the ending end F2 within the weldable range, the current collection efficiency of the lithium ion battery 1 can be improved.

[0055] In the following description, the distance from the ending end F2 to the third welding part 82A is appropriately referred to as LA1 (unit: mm). Also, the distance from the third welding part 82A to the fourth welding part 82B is appropriately referred to as LA2 (unit: mm).

[0056] The lithium ion battery 1 according to the present embodiment is a secondary battery that satisfies the following formulas (1) and (2). 0 ≦ LC1 ≦ LC2 ··· (1) 0 ≦ LA1 ≦ LA2 ··· (2)

[0057] When the diameter (outer shape) of the lithium ion battery 1 is D (mm), it is preferable that the upper limit values of LC1 and LA1 are 0.38D, and the upper limit values of LC2 and LA2 are 0.75D. The diameter of the lithium ion battery 1 is, for example, the diameter of the bottom surface (the surface of the negative electrode terminal) of the battery can 11. The length 0.38D corresponds to approximately 1 / 8 of the length of the circumferential surface of the electrode winding body 20. When LC1 and LA1 are 0.38D or less, the current collection efficiency becomes relatively high, so a lithium ion battery 1 with low resistance can be realized. Also, the length 0.75D corresponds to approximately 1 / 4 of the length of the circumferential surface of the electrode winding body 20. When LC2 and LA2 are 0.75D or less, the current collection efficiency becomes relatively high, so a lithium ion battery 1 with low resistance can be realized.

[0058] [Method for manufacturing a lithium ion battery] Next, with reference to FIGS. 15A to 15F, a method for manufacturing the lithium-ion battery 1 according to the present embodiment will be described. First, a positive electrode active material is applied to the surface of the strip-shaped positive electrode foil 21A to form a positive electrode active material coated portion 21B, and a negative electrode active material is applied to the surface of the strip-shaped negative electrode foil 22A to form a negative electrode active material coated portion 22B. At this time, a positive electrode active material non-coated portion 21C where the positive electrode active material is not applied is provided on one end side in the width direction of the positive electrode foil 21A, and a negative electrode active material non-coated portion 22C (a first negative electrode active material non-coated portion 221A, a second negative electrode active material non-coated portion 221B, and a third negative electrode active material non-coated portion 221C) where the negative electrode active material is not applied is provided on the negative electrode foil 22A. Next, processes such as drying are performed on the positive electrode 21 and the negative electrode 22. Then, they are stacked via the separator 23 so that the positive electrode active material non-coated portion 21C and the negative electrode active material non-coated portion 22C are in opposite directions, and wound in a spiral shape so as to form a through hole 26 in the central axis, thereby manufacturing an electrode wound body 20 as shown in FIG. 15A.

[0059] Next, using a groove forming jig (not shown) provided with a flat plate or the like on the end surface, as shown in FIG. 15B, a groove 43 was formed (manufactured). Specifically, by pressing the flat plate or the like of the groove forming jig perpendicular to the end surfaces 41 and 42, a groove 43 was formed in a part of the end surface 41 and a part of the end surface 42. By this method, a groove 43 extending radially from the through hole 26 was formed. The groove 43 extends, for example, from the outer edge portions 27 and 28 of the end surfaces 41 and 42 to the through hole 26. Note that the number and arrangement of the grooves 43 shown in FIG. 15B are merely examples and are not limited to the illustrated examples.

[0060] Then, using a flat surface forming jig (not shown), flat surfaces 71 and 72 were formed as shown in FIG. 15C (flat surface forming step). Specifically, a pressing load was applied to end faces 41 and 42 in a direction substantially perpendicular thereto from both electrode sides simultaneously with the same pressure by the flat end face of the flat surface forming jig. As a result, each of the positive electrode active material non-coated portion 21C and the negative electrode active material non-coated portion 22C (more specifically, the first negative electrode active material non-coated portion 221A) overlapped toward the central axis, so that the end faces 41 and 42 became the flat surfaces 71 and 72. The flat surfaces 71 and 72 each have a groove 43 formed in the groove forming step. Then, the fan-shaped portion 31 of the positive electrode current collector 24 was laser-welded to the flat surface 71, and the fan-shaped portion 33 of the negative electrode current collector 25 was laser-welded to the flat surface 72 and joined.

[0061] Subsequently, as shown in FIG. 15D, the strip-shaped portion 32 of the positive electrode current collector 24 and the strip-shaped portion 34 of the negative electrode current collector 25 were bent, an insulating plate 12 was attached to the positive electrode current collector 24, and an insulating plate 13 was attached to the negative electrode current collector 25. The electrode winding body 20 assembled as described above was inserted into the battery can 11 shown in FIG. 15E. Then, by pressing a welding rod (not shown), the negative electrode current collector 25 was welded to the bottom of the battery can 11. After injecting the electrolytic solution into the battery can 11, sealing was performed with the gasket 15 and the battery lid 14 as shown in FIG. 15F. Thus, the lithium ion battery 1 was manufactured.

[0062] Note that the insulating plates 12 and 13 may be insulating tapes. Also, the joining method may be other than laser welding. Further, the groove 43 remains in the flat surface even after the positive electrode active material non-coated portion 21C and the first negative electrode active material non-coated portion 221A are bent, and the portion without the groove 43 is joined to the positive electrode current collector 24 or the negative electrode current collector 25, but the groove 43 may be joined to a part of the positive electrode current collector 24 or the negative electrode current collector 25.

[0063] [Effects Obtained by this Embodiment] According to this embodiment, for example, the following effects can be obtained. By providing welding portions at locations close to the end portions F1 of the winding ends of the positive electrode 21 and the end portions F1 of the winding ends of the negative electrode 22 respectively, the current collection efficiency can be improved. Therefore, a lithium-ion battery with a small internal resistance and excellent high-output characteristics can be provided.

[0064] During the production of a lithium-ion battery, when pressing the end of a thin flat plate (for example, with a thickness of 0.5 mm) in a direction perpendicular to the end faces 41 and 42 (when performing the process shown in FIG. 15B), at the winding start side of the electrode winding body 20 (the end side in the longitudinal direction of the negative electrode at the innermost circumference of the electrode winding body 20), the negative electrode active material may peel off from the negative electrode active material coating portion 22B. This peeling is considered to be caused by the stress generated when pressing the flat plate against the end face 42. The peeled negative electrode active material may enter the inside of the electrode winding body 20, which may cause an internal short circuit in the lithium-ion battery 1. In this embodiment, since the second negative electrode active material non-coating portion 221B is provided, peeling of the negative electrode active material can be prevented, and the occurrence of an internal short circuit can be prevented.

[0065] At the winding termination side of the electrode winding body 20, the negative electrode 22 can have a region of the negative electrode active material non-coating portion 22C on the main surface on the side not facing the positive electrode active material coating portion 21B. This is because even if the negative electrode active material coating portion 22B is provided on the main surface not facing the positive electrode active material coating portion 21B, its contribution to charge and discharge is considered to be low. The region of the negative electrode active material non-coating portion 22C is preferably 3 / 4 to 5 / 4 turns of the electrode winding body 20. At this time, since the negative electrode active material coating portion 22B with a low contribution to charge and discharge is not provided, the initial capacity can be increased with respect to the volume of the same electrode winding body 20.

[0066] In this embodiment, since the electrode winding body 20 is wound by overlapping the non-coated portion 21C of the positive electrode active material and the first non-coated portion 221A of the negative electrode active material so that they face in opposite directions, the non-coated portion 21C of the positive electrode active material gathers on the end face 41, and the first non-coated portion 221A of the negative electrode active material gathers on the end face 42 of the electrode winding body 20. Such non-coated portion 21C of the positive electrode active material and the first non-coated portion 221A of the negative electrode active material are bent, and the end faces 41 and 42 are flat surfaces 71 and 72. The bending direction is the direction from the outer edge portions 27 and 28 of the end faces 41 and 42 toward the central axis, and the non-coated portions of the active material of adjacent circumferences overlap each other in the wound state. Since the end face 41 becomes the flat surface 71, the contact between the non-coated portion 21C of the positive electrode active material and the positive electrode current collector 24 is improved. Since the end face 42 becomes the flat surface 72, the contact between the first non-coated portion 221A of the negative electrode active material and the negative electrode current collector 25 is improved. Further, since the end faces 41 and 42 are flat surfaces 71 and 72, the low resistance of the lithium ion battery 1 can be realized.

[0067] Also, by bending the non-coated portion 21C of the positive electrode active material and the first non-coated portion 221A of the negative electrode active material, it seems possible to make the end faces 41 and 42 flat surfaces. However, if there is no processing before bending, wrinkles and voids (gaps, spaces) may occur on the end faces 41 and 42, and there is a possibility that the end faces 41 and 42 may not become flat surfaces. Here, "wrinkles" and "voids" mean portions where the bent non-coated portion 21C of the positive electrode active material or the first non-coated portion 221A of the negative electrode active material is biased and the end faces 41 and 42 do not become flat surfaces. In this embodiment, grooves 43 are formed in advance in the radial direction from the through holes 26 on each of the end face 41 and the end face 42 side. By forming the grooves 43, the generation of these wrinkles and voids can be suppressed, and the end faces 41 and 42 can be made flatter. Note that either one of the non-coated portion 21C of the positive electrode active material and the first non-coated portion 221A of the negative electrode active material may be bent, but preferably both are bent.

Example

[0068] Hereinafter, using the lithium-ion battery manufactured as described above, while changing the sizes of LC1, LC2, LA1, and LA2, the AC resistance ACR (mΩ), DC resistance DCR (mΩ), and load discharge rate (%) were measured. The present invention will be specifically described using examples and comparative examples. Note that the present invention is not limited to the examples described below.

[0069] In all of the following examples and comparative examples, the battery size was 186500 (diameter 18 mm, height 65 mm), and the shape was cylindrical. The material of the positive current collector 24 was an Al alloy, and the material of the negative current collector 25 was a Cu alloy. The length D5 in the width direction of the positive electrode active material non-coated portion 21C = 7 (mm), the length D6 in the width direction of the first negative electrode active material non-coated portion 221A = 4 (mm), the length D7 in the width direction of the portion where the positive electrode active material non-coated portion 21C protruded from the separator 23 = 4.5 (mm), and the length D8 in the width direction of the portion where the first negative electrode active material non-coated portion 221A protruded from the separator 23 = 3 (mm). The separator 23 was overlapped so as to cover the entire range of the positive electrode active material coated portion 21B and the negative electrode active material coated portion 22B. Also, the number of grooves 43 was set to 8 and arranged at substantially equal angular intervals.

[0070] [Example 1] The lithium-ion battery 1 was manufactured by the above-described process. At this time, the first welding portion 81A and the second welding portion 81B were provided so as to satisfy 0 ≦ LC1 ≦ LC2, and the third welding portion 82A and the fourth welding portion 82B were provided so as to satisfy 0 ≦ LA1 ≦ LA2.

[0071] [Comparative Example 1] The first welding portion 81A and the second welding portion 81B were provided such that the relationship between LC1 and LC2 was LC2 < LC1, and the third welding portion 82A and the fourth welding portion 82B were provided such that the relationship between LA1 and LA2 was LA2 < LA1. Otherwise, a lithium-ion battery was manufactured in the same manner as in Example 1.

[0072] [Comparative Example 2] In Comparative Example 2, the first welding portion 81A and the second welding portion 81B were provided so as to satisfy 0 ≦ LC1 ≦ LC2, and the third welding portion 82A and the fourth welding portion 82B were provided so as not to satisfy 0 ≦ LA1 ≦ LA2. In other words, LA2 < LA1. A lithium ion battery was fabricated in the same manner as in Example 1 except for this.

[0073] [Comparative Example 3] In Comparative Example 3, the first welding portion 81A and the second welding portion 81B were provided so as not to satisfy 0 ≦ LC1 ≦ LC2. In other words, LC2 < LC1. The third welding portion 82A and the fourth welding portion 82B were provided so as to satisfy 0 ≦ LA1 ≦ LA2. A lithium ion battery was fabricated in the same manner as in Example 1 except for this.

[0074] [Evaluation] For the batteries of Example 1 and Comparative Examples 1 to 3, the alternating current resistance ACR (mΩ), the direct current resistance DCR (mΩ), and the load discharge rate (%) were measured. The alternating current resistance ACR was the resistance value (mΩ) at an alternating current of 1 kHz. The direct current resistance DCR (mΩ) was obtained by calculating the slope of the voltage when the discharge current was increased from 0 (A) to 100 (A) in 5 seconds. Regarding the load discharge rate (%), after charging at a constant current of 2 (A) for 3.5 (h), discharging was performed at a current value of 40 (A), a cut-off voltage of 2.0 (V), and an environmental temperature of 23°C until the surface temperature of the battery reached 75°C, and the discharge capacity (mAh) was divided by the charge capacity (mAh). In each measurement, the average value was calculated from the measurement values of 10 lithium ion batteries. The results are shown in Table 1.

[0075] [Table 1]

[0076] The AC resistance (ACR) was 4 mΩ for both Example 1 and Comparative Examples 1 to 3. The DC resistance (DCR) was 10.5 (mΩ) for Example 1, 11.3 (mΩ) for Comparative Example 1, 10.9 (mΩ) for Comparative Example 2, and 11.1 (mΩ) for Comparative Example 3. Example 1 had the lowest value. Regarding the load discharge rate, it was 80 (%) for Example 1, 76 (%) for Comparative Example 1, 78 (%) for Comparative Example 2, and 77 (%) for Comparative Example 3. Example 1 had the highest value. From the results in Table 1 above, it was found that Example 1 satisfying the above-described formulas (1) and (2) can achieve a battery with improved current collection efficiency, lower internal resistance, and excellent high-rate characteristics.

[0077] <Modification Example> As described above, one embodiment of the present invention has been specifically described. However, the content of the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible.

[0078] The shapes of the positive current collector plate 24 and the negative current collector plate 25 can be appropriately changed, and the number of the welded part groups 81 and 82 may also vary according to their shapes. For example, as shown in FIG. 16A, the positive current collector plate 24 may be the positive current collector plate 51. The positive current collector plate 51 has a substantially circular base 51A having a hole 51B at the center and a belt-like portion 51C extending outward from a part of the outer edge of the base 51A. When the shape of the positive current collector plate is the positive current collector plate 51, for example, as shown in FIG. 16B, eight welded part groups 81 are formed radially. Further, for example, as shown in FIG. 17A, the positive current collector plate 24 may be the positive current collector plate 52. The positive current collector plate 52 has a substantially circular base 52A having a hole 52B at the center and a belt-like portion 52C extending outward from a part of the outer edge of the base 52A. Notches 52D and 52E directed inward are formed at two locations between the base 52A and the belt-like portion 52C. When the shape of the positive current collector plate is the positive current collector plate 52, for example, as shown in FIG. 17B, six welded part groups 81 are formed radially. The above modification examples are also applicable to the negative current collector plate 25.

[0079] Laser welding may be performed by intermittently irradiating laser light. The shape of the welding portion group, the number of welding portions constituting the welding portion group, etc. can be appropriately changed. In the above-described embodiment, a configuration in which the second negative electrode active material non-coated portion 221B and the third negative electrode active material non-coated portion 221C are provided is preferable, but the present invention can also be applied to a lithium ion battery without these. In the above-described examples and comparative examples, the number of the grooves 43 was set to 8, but other numbers may be used. A configuration in which the grooves 43 are provided is preferable, but the present invention is also applicable to a battery without the grooves 43. The battery size may be other than 21700 (diameter 21 mm, height 70 mm) and 18650 (diameter 18 mm, height 65 mm). The shapes of the fan-shaped portions 31 and 33 according to the above-described embodiment may be shapes other than the fan shape.

[0080] Unless departing from the gist of the present invention, the present invention can also be applied to batteries other than lithium ion batteries and batteries having a shape other than a cylindrical shape (for example, a laminated battery, a prismatic battery, a coin battery, a button battery). In this case, the shape of the "end face of the electrode winding body" can be not only a cylindrical shape but also a rectangular shape, an elliptical shape, a flat shape, etc. Further, the present invention can also be realized as a method for manufacturing a battery.

[0081] <Application Example> (1) Battery Pack FIG. 18 is a block diagram showing a circuit configuration example when the secondary battery according to the embodiment or example of the present invention is applied to a battery pack 300. The battery pack 300 includes a battery assembly 301, a charging control switch 302a, a switch unit 304 including a discharging control switch 303a, a current detection resistor 307, a temperature detection element 308, and a control unit 310. The control unit 310 controls each device, and can further perform charge and discharge control during abnormal heat generation, calculate and correct the remaining capacity of the battery pack 300. The positive electrode terminal 321 and the negative electrode terminal 322 of the battery pack 300 are connected to a charger or an electronic device, and charge and discharge are performed.

[0082] The assembled battery 301 is formed by connecting a plurality of secondary batteries 301a in series and / or in parallel. In FIG. 18, a case where six secondary batteries 301a are connected in 2 parallel and 3 series (2P3S) is shown as an example. The secondary battery of the present invention can be applied to the secondary battery 301a.

[0083] The temperature detection unit 318 is connected to a temperature detection element 308 (e.g., a thermistor), measures the temperature of the assembled battery 301 or the battery pack 300, and supplies the measured temperature to the control unit 310. The voltage detection unit 311 measures the voltages of the assembled battery 301 and each secondary battery 301a constituting the same, A / D-converts 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.

[0084] 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. The switch control unit 314 sends an OFF control signal to the switch unit 304 when the secondary battery 301a reaches an overcharge detection voltage (e.g., 4.20 V ± 0.05 V) or higher or an overdischarge detection voltage (2.4 V ± 0.1 V) or lower, thereby preventing overcharge or overdischarge.

[0085] After the charge control switch 302a or the discharge control switch 303a is turned OFF, charging or discharging is possible only through the diode 302b or the diode 303b. These charge and discharge switches can use semiconductor switches such as MOSFETs. In FIG. 18, the switch unit 304 is provided on the + side, but it may be provided on the - side.

[0086] The memory 317 consists of a RAM and a ROM, stores and can rewrite values of battery characteristics calculated by the control unit 310, full charge capacity, remaining capacity, etc.

[0087] (2) Electronic device The secondary battery according to the above-described embodiment or example of the present invention can be mounted on devices such as electronic devices, electric transportation devices, and power storage devices, and can be used to supply power.

[0088] Examples of electronic devices include notebook personal computers, smartphones, tablet terminals, PDAs (personal digital assistants), mobile phones, wearable terminals, digital still cameras, e-books, music players, game machines, hearing aids, power tools, televisions, lighting devices, toys, medical devices, and robots. In addition, electric transportation devices, power storage devices, power tools, electric unmanned aerial vehicles, etc., which will be described later, can also be included in electronic devices in a broad sense.

[0089] Examples of electric transportation devices include electric vehicles (including hybrid vehicles), electric motorcycles, electric assist bicycles, electric buses, electric carts, automated guided vehicles (AGVs), railway vehicles, etc. In addition, electric passenger aircraft and electric unmanned aerial vehicles for transportation are also included. The secondary battery according to the present invention can be used not only as a driving power source for these but also as an auxiliary power source, an energy regeneration power source, etc.

[0090] Examples of power storage devices include commercial or household power storage modules, and power storage power sources for buildings such as houses, buildings, offices, or for power generation facilities.

[0091] (3) Power Tools With reference to FIG. 19, an example of an electric driver as a power tool to which the present invention is applicable will be schematically described. The electric driver 431 is provided with a motor 433 that transmits rotational power to a shaft 434 and a trigger switch 432 that is operated by a user. A battery pack 430 and a motor control unit 435 are housed in a lower housing of the handle of the electric driver 431. The battery pack 430 is built in or detachable from the electric driver 431. The secondary battery of the present invention can be applied to the battery constituting the battery pack 430.

[0092] Each of the battery pack 430 and the motor control unit 435 is provided with a microcomputer (not shown), and the charge and discharge information of the battery pack 430 may be capable of communicating with each other. The motor control unit 435 controls the operation of the motor 433 and can cut off the power supply to the motor 433 in case of an abnormality such as over-discharge.

[0093] (4) Electric vehicle power storage system As an example of applying the present invention to an electric vehicle power storage system, FIG. 20 schematically shows a configuration example of a hybrid vehicle (HV) adopting a series hybrid system. The series hybrid system is a vehicle that runs with a power drive force conversion device using the electric power generated by a generator powered by an engine or the electric power once stored in a battery.

[0094] This hybrid vehicle 600 is equipped with an engine 601, a generator 602, a power drive force conversion device (a DC motor or an AC motor. Hereinafter simply referred to as "motor 603"), drive wheels 604a, 604b, wheels 605a, 605b, a battery 608, a vehicle control device 609, various sensors 610, and a charging port 611. As the battery 608, the secondary battery of the present invention or a power storage module equipped with a plurality of secondary batteries of the present invention can be applied.

[0095] 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. It is possible to store the electric power generated by the generator 602 in the battery 608 by the rotational force generated by the engine 601. The various sensors 610 control the engine speed or the opening degree of a throttle valve (not shown) via the vehicle control device 609.

[0096] When the hybrid vehicle 600 decelerates by a braking mechanism (not shown), the resistance force during deceleration is applied to the motor 603 as a rotational force, and the regenerative power generated by this rotational force is stored in the battery 608. Also, the battery 608 can be charged by being connected 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 vehicle (PHV or PHEV).

[0097] In addition, by applying the secondary battery according to the present invention to a miniaturized primary battery, it is also possible to use it as a power source for a tire pressure monitoring system (TPMS) built into the wheels 604 and 605.

[0098] In the above, the series hybrid vehicle has been described as an example, but the present invention is also applicable to a parallel hybrid vehicle that combines an engine and a motor, or a hybrid vehicle that combines a series system and a parallel system. Furthermore, the present invention is also applicable to an electric vehicle (EV or BEV) that runs only on a drive motor without using an engine, and a fuel cell vehicle (FCV).

Explanation of reference numerals

[0099] 1... Lithium-ion battery, 12, 13... Insulating plates, 21... Positive electrode, 21A... Positive electrode foil, 21B... Positive electrode active material layer, 21C... Positive electrode active material non-coated portion, 22... Negative electrode, 22A... Negative electrode foil, 22B... Negative electrode active material layer, 22C... Negative electrode active material non-coated portion, 23... Separator, 24... Positive electrode current collector plate, 25... Negative electrode current collector plate, 26... Through hole, 31, 33... Fan-shaped portions, 32, 34... Belt-shaped portions, 41, 42... End faces, 43... Groove, 71, 72... Flat surfaces, 81, 82... Welded portion groups, 81A... First welded portion, 81B... Second welded portion, 82A... Third welded portion, 82B... Fourth welded portion, 221A... First negative electrode active material non-coated portion

Claims

1. A secondary battery in which a strip-shaped positive electrode and a strip-shaped negative electrode are laminated via a separator, and a positive electrode current collector and a negative electrode current collector are housed in a battery can, wherein the positive electrode has a positive electrode active material coated portion coated with a positive electrode active material layer and a positive electrode active material non-coated portion on a strip-shaped positive electrode foil, the negative electrode has a negative electrode active material coated portion coated with a negative electrode active material layer and a negative electrode active material non-coated portion extending in the longitudinal direction of the negative electrode foil, the positive electrode active material non-coated portion is welded to the positive electrode current collector at one end face of the electrode wound body, the negative electrode active material non-coated portion is welded to the negative electrode current collector at the other end face of the electrode wound body, the positive electrode current collector and the negative electrode current collector each have a group of welding portions formed radially, at least one of the positive electrode current collector and the negative electrode current collector has a portion where the intervals between the two groups of welding portions with respect to the predetermined group of welding portions are different, based on a predetermined welding portion located at the outermost circumference of the electrode wound body in the predetermined group of welding portions, such that the interval from the predetermined welding portion to an adjacent welding portion along the winding direction of the electrode wound body is different from the interval from the predetermined welding portion to an adjacent welding portion along the direction opposite to the winding direction, the positive electrode active material non-coated portion has a first welding portion closest to the end of the positive electrode foil where winding ends, and a second welding portion closer to the end of the positive electrode foil where winding ends next to the first welding portion, the negative electrode active material non-coated portion has a third welding portion closest to the end of the negative electrode foil where winding ends, and a fourth welding portion closer to the end of the negative electrode foil where winding ends next to the third welding portion, when the distance from the end of the positive electrode foil where winding ends to the first welding portion is LC1 (mm) and the distance from the first welding portion to the second welding portion is LC2 (mm), when the distance from the end of the negative electrode foil where winding ends to the third welding portion is LA1 (mm) and the distance from the third welding portion to the fourth welding portion is LA2 (mm), a secondary battery satisfying the following formulas (1) and (2). 0 ≦ LC1 ≦ LC2... (1) 0 ≦ LA1 ≦ LA2... (2)

2. when the diameter of the secondary battery is D (mm), the upper limit values of LC1 and LA1 are 0.38D, and the upper limit values of LC2 and LA2 are 0.75D The secondary battery according to Claim 1.

3. The non-coated portion of the positive electrode active material is bent to form a flat surface on the positive electrode side, and the flat surface on the positive electrode side and the positive electrode current collector are welded together. The non-coated portion of the negative electrode active material is bent to form a flat surface on the negative electrode side, and the flat surface on the negative electrode side and the negative electrode current collector are welded together. The secondary battery according to claim 1 or 2.

4. The positive electrode current collector has a fan-shaped portion on the positive electrode side and a strip-shaped portion on the positive electrode side, and the fan-shaped portion on the positive electrode side and the flat surface on the positive electrode side are welded together. The negative electrode current collector has a fan-shaped portion on the negative electrode side and a strip-shaped portion on the negative electrode side, and the fan-shaped portion on the negative electrode side and the flat surface on the negative electrode side are welded together. The secondary battery according to claim 3.

5. Each of the flat surface on the positive electrode side and the flat surface on the negative electrode side has a groove. The secondary battery according to claim 3 or 4.

6. Among the intervals set for each of the two welding portion groups with respect to the predetermined welding portion group, the interval from the predetermined welding portion to the adjacent welding portion along the winding direction of the electrode winding body is the first interval, and the interval from the predetermined welding portion to the adjacent welding portion along the direction opposite to the winding direction is the second interval smaller than the first interval. The end portion of the winding is disposed at the second interval. The secondary battery according to any one of claims 1 to 5.

7. Among the intervals set for each of the two welding portion groups with respect to the predetermined welding portion group, the interval from the predetermined welding portion to the adjacent welding portion along the winding direction of the electrode winding body is the first interval, and the interval from the predetermined welding portion to the adjacent welding portion along the direction opposite to the winding direction is the second interval smaller than the first interval. At least one strip-shaped portion of the positive electrode current collector and the negative electrode current collector is disposed at the first interval. The secondary battery according to any one of claims 1 to 3.

8. Each of the positive electrode current collector and the negative electrode current collector has a fan-shaped portion and a strip-shaped portion integrally formed with the fan-shaped portion. The secondary battery according to any one of claims 1 to 3.

9. An electronic device having the secondary battery according to any one of claims 1 to 8.

10. A power tool having the secondary battery according to any one of claims 1 to 8.

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