Battery and method for manufacturing battery

Abstract

To provide a battery in which the thickness of a band-shaped electrode in a wound electrode body can be homogenized easily and the deterioration in capacity can be suppressed easily.SOLUTION: A cylindrical battery 10 includes a wound electrode body in which a positive electrode 11 and a negative electrode are wound through a separator, and a positive electrode lead 20. The positive electrode 11 includes a band-shaped positive electrode current collector 36 including lead bonding parts 37a and 38a in which the positive electrode lead 20 is bonded. The positive electrode 11 includes a positive electrode mixture layer 45 including a one-side first part 41a provided continuously and integrally so as to extend in a longitudinal direction on at least one side in the thickness direction of the positive electrode current collector 36, and provided on the positive electrode lead 20 existing on the one side, and a one-side second part 41b provided on one side surface 37 in the thickness direction of the positive electrode current collector 36.SELECTED DRAWING: Figure 3b

Description

[Technical field]

[0001] The present disclosure relates to a battery including a wound electrode assembly. The present disclosure also relates to a method for manufacturing a battery including a wound electrode assembly. [Background technology]

[0002] Conventionally, a cylindrical battery described in Patent Document 1 is an example of a battery equipped with a wound electrode body. This cylindrical battery includes a wound electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, an electrolyte, a bottomed cylindrical outer can for accommodating the wound electrode body and the electrolyte, and a sealing body for sealing the opening of the outer can. The positive electrode has a strip-shaped positive electrode current collector and a positive electrode mixture layer provided on both sides thereof. The positive electrode mixture layer is provided on the positive electrode current collector by intermittently applying a paste-like positive electrode mixture slurry to the positive electrode current collector and then compressing it. On one side of the positive electrode, a non-coated portion in which the positive electrode mixture layer does not exist is provided in the center in the longitudinal direction. A positive electrode lead is joined to the non-coated portion. An insulating tape is attached to the end of the positive electrode lead on the positive electrode side to cover the positive electrode lead to prevent short circuiting. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-311282 A Summary of the Invention [Problem to be solved by the invention]

[0004] Not only in the cylindrical battery described above, but also in batteries in which electrodes are provided with non-coated portions where no composite layer is provided and leads are joined to the non-coated portions, the thickness of the area around the non-coated portion where the leads are joined or where insulating tape is applied to cover the leads tends to be thicker than other areas, and the areas where the leads or insulating tape are placed are compressed more than other areas by that thickness. Therefore, local distortion occurs after long-term cycles, which can cause battery swelling and capacity deterioration.

[0005] In particular, in the case of a cylindrical battery, if the thickness of the electrodes becomes non-uniform and the shape of the wound electrode body in a plan view deviates significantly from a perfect circle, it becomes difficult to smoothly insert the wound electrode body into the outer can. Furthermore, if the thickness of the electrodes becomes non-uniform and tension is not applied uniformly to the wound electrode body, the reaction of the positive and negative electrodes due to charging and discharging after the battery is completed becomes more non-uniform, and capacity deterioration is more likely to progress.

[0006] Therefore, an object of the present disclosure is to provide a battery in which the thickness of the band-shaped electrodes in the wound electrode body can be easily made uniform and capacity degradation can be easily suppressed, and a manufacturing method for producing such a battery. [Means for solving the problem]

[0007] In order to solve the above problems, the battery disclosed herein includes a wound electrode body in which a first electrode and a second electrode are wound with a separator interposed therebetween, and a first electrode lead, wherein the first electrode has a band-shaped first electrode current collector including a lead joint portion to which the first electrode lead is joined, and a first electrode mixture layer that is continuously and integrally provided on at least one side in a thickness direction of the first electrode current collector so as to extend in the longitudinal direction, and includes a first portion provided on the first electrode lead located on that one side, and a second portion provided on one side surface in the thickness direction of the first electrode current collector.

[0008] In addition, the manufacturing method for a battery according to the present disclosure includes joining a first electrode lead to at least one side surface of a band-shaped first electrode current collector, and then continuously and integrally applying a paste-like first electrode mixture slurry to one side in the thickness direction of the first electrode current collector, so that the paste-like first electrode mixture slurry includes a first portion provided on the first electrode lead and a second portion provided on the one side surface, and extends in the longitudinal direction. Effect of the Invention

[0009] According to the battery of the present disclosure, the thickness of the strip-shaped electrodes in the wound electrode body can be easily made uniform, and capacity deterioration can be easily suppressed. Also, according to the manufacturing method of the battery of the present disclosure, it is possible to manufacture a battery in which the thickness of the strip-shaped electrodes in the wound electrode body can be easily made uniform, and capacity deterioration can be easily suppressed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is an axial cross-sectional view of a cylindrical battery according to one embodiment of the present disclosure. [Diagram 2] FIG. 2 is a perspective view of a wound electrode body of the cylindrical battery. [Figure 3a] FIG. 2 is a plan view of a band-shaped positive electrode to which a positive electrode lead is joined, as viewed from one side in the thickness direction. [Figure 3b] 2 is a cross-sectional view of a band-shaped positive electrode to which a positive electrode lead is joined, cut along a plane that passes through the positive electrode lead and includes the thickness direction and the longitudinal direction. FIG. [Figure 4a] FIG. 2 is a plan view of a band-shaped negative electrode to which a negative electrode lead is joined, as viewed from one side in the thickness direction. [Figure 4b] 2 is a cross-sectional view of a band-shaped negative electrode to which a negative electrode lead is joined, cut along a plane that passes through the negative electrode lead and includes the thickness direction and the longitudinal direction. FIG. [Diagram 5] FIG. 4 is a side view of a positive electrode to which a positive electrode lead is joined, in the process of being manufactured, as viewed from one side in the thickness direction. [Figure 6] FIG. 2 is a plan view of a positive electrode to which a positive electrode lead is joined during manufacture, as viewed from one side in the width direction. [Figure 7] FIG. 4 is a diagram illustrating slit positions when separating the positive electrode current collector. [Figure 8] FIG. 2 is a diagram showing a state in which a protective tape is wrapped around a positive electrode lead joined to a positive electrode. [Figure 9] 3 is a cross-sectional view of a manufactured positive electrode to which a positive electrode lead is joined, cut along a plane that passes through the positive electrode lead and includes the thickness direction and the longitudinal direction. FIG. [Figure 10a] FIG. 2 is a side view of a positive electrode of a comparative example as viewed from one side in the thickness direction. [Figure 10b] FIG. 2 is a plan view of a positive electrode of a comparative example as viewed from one side in the width direction. [Figure 11] FIG. 4B is a cross-sectional view of a negative electrode according to a modified example, the cross-sectional view corresponding to FIG. 4B. [Figure 12] FIG. 3B is an end view of a modified positive electrode, corresponding to FIG. 3B. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the battery according to the present disclosure will be described in detail with reference to the drawings. The battery according to the present disclosure may be any battery having a wound electrode body (wound electrode body) in which a first electrode and a second electrode are wound with a separator interposed therebetween. The battery according to the present disclosure may be a primary battery or a secondary battery. The battery according to the present disclosure may be a cylindrical battery, a prismatic battery, or a pouch-shaped battery. The battery according to the present disclosure may be a battery using an aqueous electrolyte or a battery using a nonaqueous electrolyte. In the following, a nonaqueous electrolyte secondary battery (lithium ion battery) using a nonaqueous electrolyte is exemplified as a cylindrical battery 10 according to one embodiment, but the cylindrical battery according to the present disclosure is not limited thereto.

[0012] When multiple embodiments and modified examples are included below, it is assumed from the beginning that new embodiments will be constructed by appropriately combining the characteristic parts of those. In the following embodiments, the same components are given the same reference numerals in the drawings, and duplicated explanations are omitted. In addition, multiple drawings include schematic diagrams, and the dimensional ratios of the length, width, height, etc. of each member between different drawings do not necessarily match. In this specification, for convenience of explanation, the sealing body 17 side in the axial direction (height direction) of the battery case 15 is referred to as "upper", and the bottom side of the exterior can 16 in the axial direction is referred to as "lower". Among the components described below, components that are not described in the independent claims showing the highest concept are optional components and are not essential components.

[0013] FIG. 1 is an axial cross-sectional view of a cylindrical battery 10 according to an embodiment of the present disclosure, and FIG. 2 is a perspective view of a wound electrode body 14 of the cylindrical battery 10. As shown in FIG. 1, the cylindrical battery 10 includes a wound electrode body (wound electrode body) 14, a non-aqueous electrolyte (not shown), and a battery case 15 that accommodates the wound electrode body 14 and the non-aqueous electrolyte. The wound electrode body 14 includes a positive electrode 11 as an example of a first electrode, a negative electrode 12 as an example of a second electrode, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween. The battery case 15 is composed of a bottomed cylindrical outer can 16 and a sealing body 17 that closes the opening of the outer can 16. In addition, the cylindrical battery 10 includes a resin gasket 28 that is arranged between the outer can 16 and the sealing body 17.

[0014] The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. For example, esters, ethers, nitriles, amides, and mixed solvents of two or more of these may be used as the non-aqueous solvent. The non-aqueous solvent may contain a halogen-substituted body in which at least a part of the hydrogen atoms of these solvents is replaced with a halogen atom such as fluorine. The non-aqueous electrolyte is not limited to a liquid electrolyte, and may be a solid electrolyte using a gel polymer or the like. A lithium salt such as LiPF6 is used as the electrolyte salt.

[0015] As shown in Fig. 2, the wound electrode body 14 has a long positive electrode 11, a long negative electrode 12, and two long separators 13. The wound electrode body 14 also has a positive electrode lead 20 as an example of a first electrode lead joined to the positive electrode 11, and a negative electrode lead 21 joined to the negative electrode 12. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to suppress lithium deposition, and is formed to be longer than the positive electrode 11 in the longitudinal direction and width direction (short direction). The two separators 13 are formed to be at least slightly larger than the positive electrode 11, and are arranged to sandwich the positive electrode 11, for example.

[0016] The positive electrode 11 has a positive electrode current collector as an example of a first electrode current collector, and a positive electrode mixture layer as an example of a first electrode mixture layer formed on both sides of the positive electrode current collector. For the positive electrode current collector, a foil of a metal stable in the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal disposed on the surface layer can be used. The positive electrode mixture layer contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be produced, for example, by applying a positive electrode mixture slurry as an example of a first electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode current collector, drying the coating, and then compressing it to form a positive electrode mixture layer on both sides of the current collector.

[0017] The positive electrode active material is mainly composed of a lithium-containing metal composite oxide. Metal elements contained in the lithium-containing metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. An example of a preferred lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al.

[0018] Examples of the conductive agent contained in the positive electrode mixture layer include carbon materials such as carbon black, acetylene black, ketjen black, and graphite. Examples of the binder contained in the positive electrode mixture layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. These resins may be used in combination with cellulose derivatives such as carboxymethylcellulose (CMC) or its salts, and polyethylene oxide (PEO).

[0019] The negative electrode 12 has a negative electrode current collector and a negative electrode mixture layer formed on both sides of the current collector. For the negative electrode current collector, a foil of a metal stable in the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with the metal disposed on the surface layer can be used. The negative electrode mixture layer contains a negative electrode active material and a binder. The negative electrode 12 can be produced, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder, etc., onto the negative electrode current collector, drying the coating, and then compressing it to form a negative electrode mixture layer on both sides of the current collector.

[0020] The negative electrode active material generally uses a carbon material that reversibly absorbs and releases lithium ions. Preferred carbon materials are graphites such as natural graphites such as flake graphite, lump graphite, and earthy graphite, and artificial graphites such as lump artificial graphite and graphitized mesophase carbon microbeads. The negative electrode mixture layer may contain a Si material containing silicon (Si) as the negative electrode active material. In addition, the negative electrode active material may use a metal that alloys with lithium other than Si, an alloy containing the metal, a compound containing the metal, or the like.

[0021] The binder contained in the negative electrode mixture layer may be fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like, as in the case of the positive electrode 11, but is preferably styrene-butadiene rubber (SBR) or a modified product thereof. The negative electrode mixture layer may contain, in addition to SBR, for example, CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, or the like.

[0022] The separator 13 is a porous sheet having ion permeability and insulation. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. The material of the separator 13 is preferably a polyolefin resin such as polyethylene or polypropylene, or cellulose. The separator 13 may have either a single-layer structure or a laminated structure. A heat-resistant layer or the like may be formed on the surface of the separator 13. The negative electrode 12 may constitute the winding start end of the wound electrode body 14, but generally the separator 13 extends beyond the winding start end of the negative electrode 12, and the winding start end of the separator 13 becomes the winding start end of the wound electrode body 14.

[0023] In the example shown in FIG. 1 and FIG. 2, the positive electrode lead 20 is electrically connected to an intermediate portion such as a central portion in the winding direction of the positive electrode current collector, and the negative electrode lead 21 is electrically connected to the end of the winding direction of the negative electrode current collector. However, the negative electrode lead may be electrically connected to the start of the winding direction of the negative electrode current collector. Alternatively, the wound electrode body may have two negative electrode leads, one of which is electrically connected to the start of the winding direction of the negative electrode current collector, and the other negative electrode lead is electrically connected to the end of the winding direction of the negative electrode current collector. Alternatively, the end of the winding direction of the negative electrode current collector on the end side may be abutted against the inner surface of the outer can to electrically connect the negative electrode and the outer can.

[0024] As shown in FIG. 1, the cylindrical battery 10 further includes an insulating plate 18 disposed on the upper side of the wound electrode body 14, and an insulating plate 19 disposed on the lower side of the wound electrode body 14. In the example shown in FIG. 1, a positive electrode lead 20 attached to the positive electrode 11 passes through a through hole of the insulating plate 18 and extends to the sealing body 17 side, and a negative electrode lead 21 attached to the negative electrode 12 passes outside the insulating plate 19 and extends to the bottom 68 side of the outer can 16. The positive electrode lead 20 is connected to the lower surface of a terminal plate 23, which is the bottom plate of the sealing body 17, by welding or the like, and a sealing plate 27, which is the top plate of the sealing body 17 and is electrically connected to the terminal plate 23, serves as a positive electrode terminal. The negative electrode lead 21 is connected to the inner surface of the bottom 68 of the outer can 16 by welding or the like, and the outer can 16 serves as a negative electrode terminal.

[0025] The outer can 16 is a metal container having a cylindrical portion with a bottom. The space between the outer can 16 and the sealing body 17 is sealed with an annular gasket 28, thereby hermetically sealing the internal space of the battery case 15. The gasket 28 also includes a clamping portion 32 that is clamped between the outer can 16 and the sealing body 17, and insulates the sealing body 17 from the outer can 16. In other words, the gasket 28 serves as a seal material for maintaining airtightness inside the battery, and as an insulating material for preventing a short circuit between the outer can 16 and the sealing body 17.

[0026] The outer can 16 has an annular grooved portion 35 in a part of the height direction of the cylindrical outer circumferential surface. The grooved portion 35 can be formed, for example, by spinning a part of the cylindrical outer circumferential surface radially inward to recess it radially inward. The outer can 16 has a bottomed tubular portion 30 including the grooved portion 35, and an annular shoulder portion 33. The bottomed tubular portion 30 accommodates the wound electrode body 14 and the non-aqueous electrolyte, and the shoulder portion 33 is bent radially inward from the end of the opening side of the bottomed tubular portion 30 to extend inward. The shoulder portion 33 is formed when the upper end portion of the outer can 16 is bent inward and crimped to the peripheral portion 31 of the sealing body 17. The sealing body 17 is clamped between the shoulder portion 33 and the grooved portion 35 via the gasket 28 by the crimping, and is fixed to the outer can 16.

[0027] Fig. 3a is a plan view of a strip-shaped positive electrode 11 to which a positive electrode lead 20 is joined, as viewed from one side in the thickness direction, and Fig. 3b is a cross-sectional view of the strip-shaped positive electrode 11 to which a positive electrode lead 20 is joined, cut along a plane that passes through the positive electrode lead 20 and includes the thickness direction and the longitudinal direction. In Fig. 3a and Fig. 3b, the left side of the paper surface is the winding start side. In Fig. 3a, the region indicated by diagonal lines is the region in which a positive electrode mixture layer 45 is formed.

[0028] As shown in FIG. 3a, the positive electrode lead 20 extends from the positive electrode 11 in the width direction of the positive electrode 11. As shown in FIG. 3b, the portion of the positive electrode lead 20 on the positive electrode 11 side is bifurcated into a first end 20a and a second end 20b. The first end 20a is joined to a lead joint 37a on one side 37 of the positive electrode current collector 36 by spot welding or the like, and the second end 20b is joined to a lead joint 38a on the other side 38 of the positive electrode current collector 36 by spot welding or the like. The positive electrode lead 20 is joined to a portion of the positive electrode current collector 36 other than both ends in the longitudinal direction.

[0029] As shown in Fig. 3a, an insulating material is applied to the protruding portion protruding from the positive electrode 11 at the first end 20a and the protruding portion protruding from the positive electrode 11 at the second end 20b, or the two protruding portions are butted together and an insulating protective tape 39 is wrapped around the entire circumference to bring the two protruding portions into close contact with each other. The insulating material or protective tape 39 mainly prevents the positive electrode lead 20 from being electrically connected to the exterior can 16 (see Fig. 1).

[0030] As shown in FIG. 3b, the positive electrode 11 has a one-side positive electrode mixture layer 41 provided continuously and integrally on one side in the thickness direction of the positive electrode collector 36 so as to extend in the longitudinal direction, and an other-side positive electrode mixture layer 42 provided continuously and integrally on the other side in the thickness direction of the positive electrode collector 36 so as to extend in the longitudinal direction. The one-side positive electrode mixture layer 41 and the other-side positive electrode mixture layer 42 constitute a positive electrode mixture layer 45. The one-side positive electrode mixture layer 41 includes a one-side first portion 41a provided on the first end portion 20a of the positive electrode lead 20 and a one-side second portion 41b provided on one side surface 37 in the thickness direction of the positive electrode collector 36. The other-side positive electrode mixture layer 42 includes a other-side first portion 42a provided on the second end portion 20b of the positive electrode lead 20 and a other-side second portion 42b provided on the other side surface 38 in the thickness direction of the positive electrode collector 36. The one-side first portion 41a and the other-side first portion 42a form a first portion 47, and the one-side second portion 41b and the other-side second portion 42b form a second portion .

[0031] The thickness of the one-side positive electrode mixture layer 41 is thicker than the thickness of the first end 20a of the positive electrode lead 20. The density of the one-side first portion 41a of the one-side positive electrode mixture layer 41 is approximately equal to the density of the one-side second portion 41b. The sum of the thickness of the one-side first portion 41a and the thickness of the first end 20a of the positive electrode lead 20 is approximately equal to the thickness of the one-side second portion 41b. In other words, the thickness of the positive electrode mixture layer 45 is thicker than the thickness of the positive electrode lead 20 in the portion located on one side in the thickness direction of the positive electrode current collector 36. The density of the first portion 47 is approximately equal to the density of the second portion 48 in the portion located on one side in the thickness direction of the positive electrode current collector 36. The sum of the thickness of the first portion 47 and the thickness of the positive electrode lead 20 in the portion located on one side in the thickness direction of the positive electrode current collector 36 is approximately equal to the thickness of the second portion 48.

[0032] Similarly, the thickness of the other-side positive electrode mixture layer 42 is thicker than the thickness of the second end 20b of the positive electrode lead 20. The density of the other-side first portion 42a of the other-side positive electrode mixture layer 42 is approximately equal to the density of the other-side second portion 42b. The sum of the thickness of the other-side first portion 42a and the thickness of the second end 20b of the positive electrode lead 20 is approximately equal to the thickness of the other-side second portion 42b. In other words, the thickness of the positive electrode mixture layer 45 is thicker than the thickness of the positive electrode lead 20 in the portion located on the other side in the thickness direction of the positive electrode current collector 36. The density of the first portion 47 is approximately equal to the density of the second portion 48 in the portion located on the other side in the thickness direction of the positive electrode current collector 36. The sum of the thickness of the first portion 47 and the thickness of the positive electrode lead 20 in the portion located on the other side in the thickness direction of the positive electrode current collector 36 is approximately equal to the thickness of the second portion 48.

[0033] Fig. 4a is a plan view of the band-shaped negative electrode 12 to which the negative electrode lead 21 is joined, as viewed from one side in the thickness direction, and Fig. 4b is a cross-sectional view of the band-shaped negative electrode 12 to which the negative electrode lead 21 is joined, cut along a plane that passes through the negative electrode lead 21 and includes the thickness direction and the longitudinal direction. In Fig. 4a and Fig. 4b, the left side of the paper surface is the winding start side.

[0034] As shown in Figures 4a and 4b, the negative electrode 12 has a long negative electrode current collector 51 and a negative electrode mixture layer 52 partially and selectively provided on both sides of the negative electrode current collector 51 in the longitudinal direction. The negative electrode 50 has non-coated portions 57 on both one side surface 46 and the other side surface in the thickness direction, where the negative electrode mixture layer 52 is not coated at the end on the winding end side in the longitudinal direction and the negative electrode current collector 51 is exposed over the entire width direction. The negative electrode lead 21 is joined to the non-coated portion 57 on the one side surface 46 by spot welding or the like. The negative electrode lead 21 extends in the width direction of the negative electrode current collector 51.

[0035] Next, a manufacturing method of the positive electrode 11 to which the positive electrode lead 20 is joined will be described with reference to Figs. 5 to 9. Fig. 5 is a side view of the positive electrode 11 to which the positive electrode lead 20 is joined during the manufacturing process, as viewed from one side in the thickness direction, and Fig. 6 is a plan view of the positive electrode 11 to which the positive electrode lead 20 is joined during the manufacturing process, as viewed from one side in the longitudinal direction. Fig. 7 is a view for explaining the slit position when dividing the positive electrode 11, and Fig. 8 is a view showing a state in which a protective tape 39 is wrapped around the positive electrode lead 20 joined to the positive electrode 11. Fig. 9 is a cross-sectional view of the manufactured positive electrode 11 to which the positive electrode lead 20 is joined, cut in a plane that passes through the positive electrode lead 20 and includes the thickness direction and the longitudinal direction.

[0036] 5 and 6, the positive electrode lead 20 is welded to the positive electrode collector 36 before slitting. Two positive electrode leads 20 having the bifurcated shape described above are used, and the first and second ends 20a, 20b of one positive electrode lead 20 and the first and second ends 20a, 20b of the other positive electrode lead 20 are welded to the top, bottom, front and back of the positive electrode collector 36. The one positive electrode lead 20 and the other positive electrode lead 20 face each other in the width direction of the positive electrode collector 36 with a gap therebetween.

[0037] Next, a positive electrode mixture layer is formed so as to have a uniform thickness on both sides in the thickness direction of the positive electrode current collector 36. In detail, the long positive electrode current collector 36 is unwound by a driving roll (not shown) and transported at a constant speed to one side in the longitudinal direction under a discharge part (for example, composed of a discharge nozzle) of a positive electrode mixture slurry discharge device. In this state, the positive electrode mixture slurry is discharged from the discharge part toward the positive electrode current collector 36.

[0038] Here, the amount of the positive electrode mixture slurry per unit time when it is discharged onto one side surface 37 (the other side surface) of the positive electrode current collector 36 is made larger than the amount of the positive electrode mixture slurry per unit time when it is discharged onto the positive electrode lead 20. In this manner, the thickness of the positive electrode 11 after the positive electrode mixture layer 45 (see FIG. 7) is formed on the positive electrode current collector 36 is made to be substantially the same at a longitudinal position where the positive electrode lead 20 is present and at a longitudinal position where the positive electrode lead 20 is not present. This application of the positive electrode mixture slurry is performed on both one side and the other side of the positive electrode current collector 36.

[0039] Thereafter, the positive electrode mixture slurry is dried and compressed, and then slit along the longitudinal direction at the position shown by the dotted line in Fig. 7, i.e., the center in the width direction of the positive electrode current collector 36. Next, as shown in Fig. 8, a protective tape 39 or an insulating material is placed on the portion of the positive electrode lead 20 that protrudes from the positive electrode 11, thereby manufacturing the positive electrode 11 to which the positive electrode lead 20 is joined, as shown in Fig. 9.

[0040] Briefly, the positive electrode 11 is manufactured as follows. First, the positive electrode lead 20 is joined to at least one side surface 37 of the strip-shaped positive electrode current collector 36. Then, a paste-like positive electrode mixture slurry is continuously and integrally applied to one side in the thickness direction of the positive electrode current collector 36, including the one-side first portion 41a provided on the positive electrode lead 20 and the one-side second portion 41b provided on the one side surface 37, and extending in the longitudinal direction. When the positive electrode lead 20 has a bifurcated shape, this operation is performed on the other side of the positive electrode current collector 36 as well as on one side.

[0041] 5 to 9, first, two positive electrode leads 20 are prepared. Then, before applying the positive electrode mixture slurry, the two positive electrode leads 20 are joined to one side surface 37 in a state in which the two positive electrode leads 20 face each other at an interval in the width direction of the one side surface 37. When the positive electrode lead 20 has a bifurcated shape, the two positive electrode leads 20 are joined to the other side surface 38 as well as to the one side surface 37.

[0042] Thereafter, the positive electrode mixture slurry is continuously and integrally applied to both sides in the thickness direction of the positive electrode current collector 36 so as to extend in the longitudinal direction. After the application, the one-side first portion 41a includes a part of the positive electrode mixture slurry provided on one of the two positive electrode leads 20 and another part of the positive electrode mixture slurry provided on the other of the two positive electrode leads 20. In the case where the positive electrode lead 20 has a bifurcated shape, the other-side first portion 42a similarly includes a part of the positive electrode mixture slurry provided on one of the two positive electrode leads 20 and another part of the positive electrode mixture slurry provided on the other of the two positive electrode leads 20. After the positive electrode mixture slurry is applied, the positive electrode current collector 36 to which the positive electrode mixture slurry has been applied is slit approximately parallel to the longitudinal direction between the two positive electrode leads 20 in the width direction so as to separate the two positive electrode leads 20.

[0043] [Circularity measurement and charge / discharge cycle characteristic measurement] The inventors measured the circularity of the wound electrode body and the charge / discharge cycle characteristics of the cylindrical battery of the comparative example and the cylindrical battery of the example. The measurements were performed on five samples of both the cylindrical battery of the comparative example and the cylindrical battery of the example.

[0044] <Electrode of Comparative Example> Positive and negative electrode plates were prepared by intermittently coating the positive and negative electrode current collectors with a mixture layer, and a current collector lead was welded to the non-coated portion. The negative electrode of the comparative example was one in which the non-coated portion described with reference to Figures 4a and 4b was formed at the end of the winding, and the negative electrode lead was joined to the non-coated portion. The positive electrode of the comparative example was the positive electrode shown in Figures 10a and 10b.

[0045] FIG. 10a is a side view of the positive electrode 211 of the comparative example seen from one side in the thickness direction, and FIG. 10b is a plan view of the positive electrode 211 of the comparative example seen from one side in the width direction. As shown in FIG. 10a and FIG. 10b, the positive electrode 211 of the comparative example was provided with non-coated portions 288 on both sides in the thickness direction, except for both ends in the longitudinal direction. Then, the positive electrode lead 220 was joined only to the non-coated portion 288 on one side surface 237. Then, protective tapes 277, 278 were attached on the positive electrode lead 220 and the non-coated portions 288 on both sides. In addition, the positive electrode mixture layer 245 was formed using LiCoO2 (lithium cobalt oxide):AB (acetylene black):PVDF=100:1:1 to which an appropriate amount of NMP (N-methyl-2-pyrrolidone) was added. As the negative electrode of the comparative example, the negative electrode shown in FIG. 4a and FIG. 4b was used. The negative electrode mixture layer was formed using a mixture of natural graphite: SBR (styrene butadiene rubber): CMC (carboxymethyl cellulose) = 100:1:1 to which an appropriate amount of water was added.

[0046] <Electrodes of the Example> The negative electrode of the embodiment was the same as the negative electrode of the comparative example. The positive electrode of the embodiment was the positive electrode described with reference to Figs. 3a and 3b. The positive electrode was manufactured by the procedure described with reference to Figs. 5 to 9. The material of the positive electrode mixture layer and the material of the negative electrode mixture layer were the same as those of the positive and negative electrodes of the comparative example. In both the negative electrode of the comparative example and the negative electrode of the embodiment, a non-coated portion was provided at the end of the winding end side of the negative electrode current collector, and the negative electrode lead was joined to the non-coated portion. This is because the negative electrode portion to which the negative electrode lead is joined in the wound electrode body is located at the outermost periphery, and therefore has almost no effect on the roundness of the wound electrode body.

[0047] <Cylindrical battery of comparative example> The prepared positive and negative electrodes of the comparative example and a polyethylene separator were spirally wound to prepare a wound electrode body. Insulating plates were placed on the top and bottom of the prepared wound electrode body, respectively, and the wound electrode body was housed in an outer casing, and then the negative electrode lead was welded to the bottom of the outer casing. A groove was formed in the opening of the outer casing by pressing, a gasket was housed in the upper part of the groove, a sealing body was welded to the positive electrode lead, and a heat treatment was performed for 150 minutes in a 110°C environment, and a nonaqueous electrolyte was injected into the inside of the outer casing. The nonaqueous electrolyte was prepared by adding LiPF6 to a mixed solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of EC:EMC:DMC=3:3:4, to give a concentration of 1 mol / L. Thereafter, the opening of the outer casing was sealed by crimping the sealing body via a gasket to prepare a cylindrical nonaqueous electrolyte secondary battery.

[0048] <Cylindrical battery of the embodiment> A cylindrical nonaqueous electrolyte secondary battery was fabricated, with the only difference being that the positive and negative electrodes of the comparative example were replaced with the positive and negative electrodes of the example.

[0049] [Measurement method] <Measurement of roundness of wound electrode body> For the cylindrical batteries of the comparative example and the cylindrical batteries of the example, the maximum and minimum diameters of the completed wound electrode bodies were measured using an indicator.

[0050] <Charge / discharge cycle characteristic measurement> The cylindrical batteries of the comparative example and the cylindrical batteries of the embodiment were subjected to charge and discharge cycles using a device consisting of a power source and an electronic load. The charge and discharge conditions were as follows. The test was performed by measuring the number of cycles until the capacity of each battery deteriorated to 60% of the initial capacity. Charging: CC-CV; 0.5C-4.2V(1 / 50Ccut) Discharge: CC; 1.0C to 2.5Vcut

[0051] [Measurement results] The results of the measurement of the roundness of the wound electrode body are shown in Table 1. The units in Table 1 are mm. [Table 1]

[0052] In addition, the results of the charge / discharge cycle characteristics measurement are shown in Table 2 below. [Table 2]

[0053] In Table 1, the maximum-minimum item indicates the difference between the maximum diameter and the minimum diameter, and σ indicates the standard deviation. As shown in Table 1, the average difference between the maximum diameter and the minimum diameter in the wound electrode body of the comparative example is 0.4 mm, while the average difference between the maximum diameter and the minimum diameter in the wound electrode body of the embodiment is 0.1 mm, and it was confirmed that the wound electrode body of the embodiment has a much higher roundness than the wound electrode body of the comparative example. Also, as shown in Table 2, the average number of cycles of the battery of the comparative example is 1020, while the average number of cycles of the battery of the embodiment is 1500. From this, it was confirmed that if the battery of the embodiment is produced, the life can be significantly extended by 1.5 times or more compared to the battery of the comparative example. The inventor infers that the reason for this is that in the battery of the embodiment, the roundness of the wound electrode body is high, so that a uniform tension is easily applied in the wound electrode body regardless of the location in the wound electrode body, and local non-uniformity of the reaction of the positive and negative electrodes due to charging and discharging after the battery is completed can be suppressed.

[0054] [Essential configurations of the cylindrical battery of the present disclosure and their effects] As described above, the cylindrical battery 10 of the present disclosure includes a wound electrode body 14 in which a positive electrode (first electrode) 11 and a negative electrode 12 (second electrode) are wound with a separator 13 interposed therebetween, and a positive electrode lead (first electrode lead) 20. The positive electrode 11 also includes a strip-shaped positive electrode current collector 36 including lead joints 37a, 38a to which the positive electrode lead 20 is joined. The positive electrode 11 also includes a positive electrode mixture layer 45 (one-side positive electrode mixture layer 41 and the other-side positive electrode mixture layer 42) that is provided continuously and integrally on at least one side in the thickness direction of the positive electrode current collector 36 so as to extend in the longitudinal direction, and that includes a one-side first portion 41a provided on the positive electrode lead 20 located on the one side and a one-side second portion 41b provided on one side surface 37 in the thickness direction of the positive electrode current collector 36.

[0055] When a non-coated portion where no mixture layer is provided is provided on the first electrode and the first electrode lead is joined to the non-coated portion, an insulating tape must be placed on the first electrode lead joined to the non-coated portion to prevent a short circuit, as shown in Figures 10a and 10b. Therefore, in the longitudinal direction of the first electrode, the thickness at the location where the first electrode lead is located tends to be thicker than the thickness at the location where the first electrode lead is not located, making it difficult to make the thickness of the strip-shaped first electrode uniform regardless of the longitudinal position.

[0056] In contrast, according to the present disclosure, the positive electrode mixture layer 45 extends in the longitudinal direction and is provided continuously and integrally so as to include a portion provided on the positive electrode lead 20 on at least one side, so that the thickness of the band-shaped positive electrode 11 can be easily made uniform regardless of its longitudinal position. Therefore, local distortion is unlikely to occur in the wound electrode body 14, and non-uniformity in local reactions of the positive electrode 11 and the negative electrode 12 due to charging and discharging after the battery is completed can be suppressed, and capacity deterioration can be suppressed. In addition, power generation can be performed using the one-side first portion 41a of the positive electrode mixture layer 45 provided on the positive electrode lead 20, so the battery capacity can be increased.

[0057] Furthermore, in the manufacturing method for a battery disclosed herein, the positive electrode lead 20 is joined to at least one side surface 37 of a strip-shaped positive electrode current collector (first electrode current collector) 36, and then a paste-like positive electrode slurry (first electrode mixture slurry) is continuously and integrally applied to one side in the thickness direction of the positive electrode current collector 36, including the one-side first portion 41a provided on the positive electrode lead 20 and the one-side second portion 41b provided on the one side surface 37, and extending in the longitudinal direction.

[0058] According to the present disclosure, it is possible to manufacture a cylindrical battery 10 that can suppress non-uniformity in local reactions in the positive electrode 11 and the negative electrode 12 and thus suppress capacity degradation.

[0059] [Preferable cylindrical battery configuration and its effects] The cylindrical battery 10 may also include a bottomed, tubular exterior can 16 that houses the wound electrode body 14, and a sealing body 17 that closes the opening of the exterior can 16. The positive electrode lead 20 may also be joined to one side surface 37 at a location other than both longitudinal ends.

[0060] In the case of a cylindrical battery, if the thickness of the electrodes becomes non-uniform and the shape of the wound electrode body in a plan view deviates significantly from a perfect circle, it becomes difficult to smoothly insert the wound electrode body into the outer can. Also, if the thickness of the electrodes becomes non-uniform and tension is not uniformly applied to the wound electrode body, non-uniformity in the reactions of the positive and negative electrodes due to charging and discharging after the battery is completed becomes particularly noticeable, and capacity deterioration is likely to progress.

[0061] In contrast, with the cylindrical battery 10 configured as described above, it is easy to make the thickness of the positive electrode 11 constant regardless of the position in the longitudinal direction, and it is easy to make the wound electrode body 14 into a perfect circle. Therefore, it is easy to smoothly insert the wound electrode body 14 into the outer can 16, and capacity degradation due to charging and discharging can be greatly suppressed.

[0062] Furthermore, with respect to the portion located on the one side of the positive electrode current collector 36, the thickness of the positive electrode mixture layer 45 may be thicker than the thickness of the positive electrode lead 20, and the density of the one-side first portion 41a may be approximately equal to the density of the one-side second portion 41b. And, with respect to the portion located on the one side of the positive electrode current collector 36, the sum of the thickness of the one-side first portion 41a and the thickness of the positive electrode lead 20 may be approximately equal to the thickness of the one-side second portion 41b.

[0063] According to the above configuration, the thickness of the positive electrode 11 is approximately constant regardless of its longitudinal position. Therefore, the wound electrode body 14 of the cylindrical battery 10 can be more easily brought closer to a perfect circle, which makes it easier to insert the wound electrode body 14 into the outer casing 16 and significantly suppresses capacity degradation due to charging and discharging.

[0064] Furthermore, a portion of the positive electrode lead 20 on the positive electrode 11 side may be bifurcated into a first end 20a and a second end 20b, with the first end 20a being joined to one side surface 37 of the positive electrode current collector 36 and the second end 20b being joined to the other side surface 38 in the thickness direction of the positive electrode current collector 36. Furthermore, the positive electrode mixture layer 45 may have a one-side positive electrode mixture layer 41 provided on one side of the positive electrode current collector 36 and an other-side positive electrode mixture layer 42 provided on the other side of the positive electrode current collector 36 in the thickness direction.

[0065] In the case of the battery of the present disclosure, due to the structure in which the mixture layer is formed on the first electrode lead, it is preferable to make the thickness of the first electrode lead thinner than the thickness of the second portion of the mixture layer provided on the first electrode current collector, since this makes it easier to make the thickness of the first electrode closer to a constant thickness. Therefore, the thickness of the first electrode lead is likely to be thin, and the rigidity of the first electrode lead is likely to be low.

[0066] In contrast, according to the above configuration, the positive electrode mixture layer 45 is provided on both sides of the positive electrode current collector 36 in the thickness direction. In addition, the portion of the positive electrode lead 20 on the positive electrode 11 side is bifurcated into a first end 20a and a second end 20b, and the first end 20a is joined to one side surface 37 of the positive electrode current collector 36, and the second end 20b is joined to the other side surface 38. Therefore, not only can the capacity of the cylindrical battery 10 be increased, but also a decrease in internal resistance can be suppressed by maintaining a certain amount of volume as the positive electrode lead 20 while using a positive electrode lead 20 that is thinner than the positive electrode mixture layer 45. In addition, the rigidity of the positive electrode lead 20 on the positive electrode 11 side can be increased, so that damage to the positive electrode lead 20 can be suppressed.

[0067] In addition, in the manufacturing method of the battery of the present disclosure, two positive electrode leads 20 may be prepared. In addition, before applying the positive electrode mixture slurry, the two positive electrode leads 20 may be joined to one side surface 37 in a state in which the two positive electrode leads 20 face each other at an interval in the width direction of the one side surface 37. In addition, the one-side first portion 41a may include a part of the positive electrode mixture slurry provided on one positive electrode lead 20 of the two positive electrode leads and another part of the positive electrode mixture slurry provided on the other positive electrode lead of the two positive electrode leads 20. In addition, after applying the positive electrode mixture slurry, the positive electrode current collector 36 to which the positive electrode mixture slurry has been applied may be slit approximately parallel to the longitudinal direction between the two positive electrode leads 20 in the width direction so as to separate the two positive electrode leads 20.

[0068] According to the above configuration, it is possible to produce twice as many positive electrodes 11 as compared with a method in which one positive electrode lead is joined to a positive electrode current collector and then a positive electrode mixture layer is applied, thereby improving the mass productivity of the cylindrical battery 10.

[0069] The present disclosure is not limited to the above-described embodiment and its modified examples, and various improvements and modifications are possible within the scope of the claims of the present application and their equivalents.

[0070] For example, in the above embodiment, the first electrode is a positive electrode 11. However, the first electrode may be a negative electrode. Also, the battery is a cylindrical battery 10. However, the battery may be a prismatic battery having a flat wound electrode body, or a pouch-shaped battery having a flat wound electrode body.

[0071] Also, a case has been described in which the first electrode is the positive electrode 11, and a part of the positive electrode mixture layer 45 is provided on the positive electrode lead 20, while the negative electrode mixture layer 52 is not provided on the negative electrode lead 21. However, as shown in Fig. 11, that is, a cross-sectional view corresponding to Fig. 4b of a modified negative electrode 112, a configuration in which the negative electrode mixture layer 152 is present on the negative electrode lead 121 may be used, and both the positive electrode 11 and the negative electrode 112 may be configured such that the positive electrode mixture layer 45 and parts of the negative electrode mixture layer 152 are present on the positive electrode lead 20 and the negative electrode lead 121.

[0072] In addition, when a mixture layer is formed on at least one of the positive electrode lead and the negative electrode lead, at least one of the positive electrode lead and the negative electrode lead may be joined to a location other than both ends in the longitudinal direction of the electrode, or may be joined to an end in the longitudinal direction of the electrode. As shown in FIG. 12, that is, a cross-sectional view corresponding to FIG. 3b of the modified positive electrode 111, the positive electrode lead (which may be a negative electrode lead) 120 does not need to have a bifurcated structure, and may be joined only to one side surface 137 of the positive electrode current collector (which may be a negative electrode current collector) 145. In the present disclosure, the mixture layer may be formed only on one side in the thickness direction of the electrode. [Explanation of symbols]

[0073] 10 cylindrical battery, 11,111 positive electrode, 12,112 negative electrode, 13 separator, 14 wound electrode body, 15 battery case, 16 outer can, 17 sealing body, 20 positive electrode lead, 20a first end, 20b second end, 21,121 negative electrode lead, 36 positive electrode current collector, 37,137 one side, 37a,38a lead joint, 38 other side, 39 protective tape, 41 one side positive electrode mixture layer, 41a one side first portion, 41b one side second portion, 42 other side positive electrode mixture layer, 42a other side first portion, 42b other side second portion, 45 positive electrode mixture layer, 47 first portion, 48 second portion, 50 negative electrode, 51 Negative electrode current collector, 52,152 negative electrode mixture layer.

Claims

1. a wound electrode body in which a first electrode and a second electrode are wound with a separator interposed therebetween; A first pole lead, the first electrode comprises a strip-shaped first electrode current collector including a lead joint portion to which the first electrode lead is joined, and a first electrode mixture layer which is continuously and integrally provided on at least one side in a thickness direction of the first electrode current collector so as to extend in a longitudinal direction, the first electrode mixture layer including a one-side first portion provided on the first electrode lead located on the one side and a one-side second portion provided on one side surface in the thickness direction of the first electrode current collector, a portion of the first electrode lead on the first electrode side is bifurcated into a first end and a second end, the first end being joined to the one side surface of the first electrode current collector and the second end being joined to the other side surface in the thickness direction of the first electrode current collector, the first electrode mixture layer has a one-side mixture layer provided on the one side of the first electrode current collector, and a other-side mixture layer provided on the other side of the first electrode current collector in the thickness direction.

2. a bottomed cylindrical exterior can that accommodates the wound electrode body; a sealing body that closes an opening of the outer can, The battery according to claim 1 , wherein the first electrode lead is joined to a location on the one side surface other than both ends in the longitudinal direction.

3. With respect to the portion of the first electrode current collector located on the one side, The thickness of the first electrode mixture layer is greater than the thickness of the first electrode lead, The density of the one-side first portion is substantially equal to the density of the one-side second portion, 3. The battery according to claim 1, wherein a thickness of the one-side first portion plus a thickness of the first electrode lead is approximately equal to a thickness of the one-side second portion.

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