Secondary battery

Abstract

The secondary battery is characterized by comprising an electrode body formed by winding a positive electrode and a negative electrode with a separator therebetween, a battery case for accommodating the electrode body, and an electrode lead (30) for conducting the positive electrode or the negative electrode and the battery case. The electrode lead (30) is an insert coating material which has a first metal material (32) and a second metal material (34) having a higher electrical resistivity than the first metal material (32), and which is obtained by embedding the second metal material (34) on the surface of the first metal material (32) along the longitudinal direction of the electrode lead (30). The second metal material (34) is bonded to the positive electrode or the negative electrode on one end side in the longitudinal direction of the electrode lead (30), and the second metal material (34) is bonded to the battery case on the other end side in the longitudinal direction of the electrode lead (30).

Description

Technical Field

[0001] The present invention relates to a secondary battery. Background Art

[0002] For example, a secondary battery such as a non-aqueous electrolyte secondary battery is configured such that an electrode body formed by winding a positive electrode and a negative electrode with a separator interposed therebetween is housed in a battery case, and electrode leads (a positive electrode lead and a negative electrode lead) electrically connect the electrodes (positive electrode and negative electrode) to the battery case.

[0003] For example, Patent Document 1 discloses that a negative electrode lead is composed of a two-layer composite material on the negative electrode side and the battery case side, and each layer is made of a material having a greater bonding property to the facing negative electrode or battery case than the other layer.

[0004] In addition, for example, Patent Document 2 discloses that a negative electrode lead has a multilayer structure including a first layer containing copper or a copper alloy and a second layer of nickel or a nickel alloy.

[0005] In addition, for example, Patent Document 3 discloses that in an electrode lead connected to an electrode body, the tip portion on the side opposite to the electrode body is metal-clad.

[0006] In addition, for example, Patent Document 4 discloses a negative electrode lead in which nickel is coated on both sides of copper.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Laid-Open No. 10-154490

[0010] Patent Document 2: Japanese Patent Laid-Open No. 2003-100278

[0011] Patent Document 3: Japanese Patent Laid-Open No. 2003-123733

[0012] Patent Document 4: Japanese Patent Laid-Open No. 2001-176491 Summary of the Invention

[0013] However, when welding an electrode lead to an electrode or a battery case, it is desirable to suppress a decrease in the bonding property to the electrode or battery case. In addition, it is also desirable to improve the current collection efficiency by reducing the resistance of the electrode lead.

[0014] An object of the present invention is to reduce the resistance while maintaining the bonding property to an electrode and a battery case in an electrode lead provided in a secondary battery.

[0015] The secondary battery of the present invention is characterized in that it includes an electrode body formed by winding a positive electrode and a negative electrode with a separator therebetween, a battery case housing the electrode body, and an electrode lead wire that electrically connects the positive electrode or the negative electrode to the battery case. The electrode lead wire is a clad material having a first metal material and a second metal material with a resistivity higher than that of the first metal material, and the second metal material is embedded along the length direction of the electrode lead wire on the surface of the first metal material. On one end side in the length direction of the electrode lead wire, the second metal material is joined to the positive electrode or the negative electrode, and on the other end side in the length direction of the electrode lead wire, the second metal material is joined to the battery case.

[0016] According to the present invention, in the electrode lead wire provided in the secondary battery, it is possible to reduce the resistance while maintaining the joinability to the electrode and the battery case. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic cross-sectional view of a secondary battery as an example of an embodiment.

[0018] Figure 2 is a schematic perspective view showing an example of the electrode lead wire of the present embodiment.

[0019] Figure 3 is a schematic perspective view showing another example of the electrode lead wire of the present embodiment.

[0020] Figure 4 is a schematic perspective view showing another example of the electrode lead wire of the present embodiment.

[0021] Figure 5 is a schematic perspective view showing another example of the electrode lead wire of the present embodiment.

[0022] Figure 6 is showing Figure 2 a schematic cross-sectional view of the joining state of the shown electrode lead wire to the electrode or the battery case.

[0023] Figure 7 is showing Figure 3 a schematic cross-sectional view of the joining state of the shown electrode lead wire to the electrode or the battery case.

[0024] Figure 8 is showing Figure 4 a schematic cross-sectional view of the joining state of the shown electrode lead wire to the battery case.

[0025] Figure 9 is showing Figure 4 a schematic cross-sectional view of the joining state of the shown electrode lead wire to the electrode.

[0026] Figure 10It is a schematic cross-sectional view showing Figure 5 the joined state of the electrode lead and the battery case shown.

[0027] Figure 11 It is a schematic cross-sectional view showing Figure 5 the joined state of the electrode lead and the electrode shown. Detailed Embodiment

[0028] Hereinafter, an example of an embodiment of the secondary battery of the present invention will be described.

[0029] Figure 1 It is a schematic cross-sectional view of a secondary battery as an example of an embodiment. Figure 1 The secondary battery 10 shown includes a wound electrode body 14 in which a positive electrode 11 and a negative electrode 12 are wound with a separator 13 interposed therebetween, an electrolyte, insulating plates 18 and 19 disposed above and below the electrode body 14, a positive electrode lead 20, a negative electrode lead 21, and a battery case 15 that houses the above components. The battery case 15 is composed of a bottomed cylindrical case body 16 and a sealing body 17 that seals the opening of the case body 16. As the battery case 15, examples include metal cases such as cylindrical and square cases, and resin cases (so-called laminated types) formed by laminating resin sheets.

[0030] The electrolyte has ion conductivity (e.g., lithium ion conductivity) for example. The electrolyte can be a liquid electrolyte (electrolyte solution) or a solid electrolyte.

[0031] The liquid electrolyte (electrolyte solution) contains, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. As the non-aqueous solvent, esters, ethers, nitriles, amides, and mixed solvents of two or more thereof are used, for example. As an example of the non-aqueous solvent, ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents thereof can be cited. The non-aqueous solvent may also contain a halogen substitute (e.g., fluoroethylene carbonate) in which at least a part of the hydrogen of these solvents is substituted with a halogen atom such as fluorine. As the electrolyte salt, lithium salts such as LiPF6 are used, for example.

[0032] In addition, as the solid electrolyte, for example, a solid or gel polymer electrolyte, an inorganic solid electrolyte, etc. can be used. The polymer electrolyte contains, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt, and a matrix polymer. As the matrix polymer, for example, a polymer material that gels after absorbing a non-aqueous solvent is used. Examples of the polymer material include fluororesin, acrylic resin, polyether resin, etc. As the inorganic solid electrolyte, known materials in all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, etc.) can be used. It should be noted that although the electrolytes exemplified above are non-aqueous electrolytes, the electrolyte is not limited to non-aqueous electrolytes and can also be an aqueous electrolyte.

[0033] The housing main body 16 is, for example, a metal container having a bottomed cylindrical shape. A gasket 28 is provided between the housing main body 16 and the sealing body 17 to ensure the airtightness inside the battery. The housing main body 16 has, for example, a bulging portion 22 that bulges inwardly at a part of the side surface and supports the sealing body 17. The bulging portion 22 is preferably formed in a ring shape along the circumferential direction of the housing main body 16, and the sealing body 17 is supported by its upper surface.

[0034] The sealing body 17 has a structure in which a filter 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are laminated in order from the electrode body 14 side. Each member constituting the sealing body 17 has, for example, a disc shape or a ring shape, and the members other than the insulating member 25 are electrically connected to each other. The lower valve body 24 and the upper valve body 26 are connected to each other at their central portions, and the insulating member 25 is sandwiched between their peripheral portions. When the internal pressure of the secondary battery 10 rises due to heat generation caused by internal short circuit or the like, for example, the lower valve body 24 deforms and breaks in a manner of pushing the upper valve body 26 toward the cap 27 side, blocking the current path between the lower valve body 24 and the upper valve body 26. When the internal pressure further rises, the upper valve body 26 breaks, and gas is discharged from the opening of the cap 27.

[0035] One end of the positive electrode lead 20 is joined to the positive electrode 11, and the other end of the positive electrode lead 20 passes through the through hole of the insulating plate 18 and is joined to the lower surface of the filter 23, which is the bottom plate of the sealing body 17. In this way, the positive electrode 11 and the sealing body 17 are electrically connected via the positive electrode lead 20, and the cap 27, which is the top plate of the sealing body 17, becomes the positive terminal. In addition, one end of the negative electrode lead 21 is joined to the negative electrode 12, and the other end of the negative electrode lead 21 passes outside the insulating plate 19 and is joined to the inner surface of the bottom of the housing main body 16. In this way, the negative electrode 12 and the housing main body 16 are electrically connected via the negative electrode lead 21, and the housing main body 16 becomes the negative terminal.

[0036] At least any one of the positive electrode lead 20 and the negative electrode lead 21 is the electrode lead of the present embodiment described below.

[0037] Figures 2 - 5 It is a schematic perspective view showing an example of the electrode lead of the present embodiment. The electrode lead 30 of the present embodiment has a first metal material 32 and a second metal material 34 having a resistivity (Ω·m) higher than that of the first metal material 32, and the second metal material 34 is embedded along the length direction of the electrode lead 30 on the surface of the first metal material 32 to form an inlaid coating material. Therefore, on the surface of the electrode lead 30, the first metal material 32 and the second metal material 34 are alternately arranged along the width direction. The second metal material 34 is provided from one end in the length direction of the first metal material 32 to the other end. The second metal material 34 is embedded in a groove formed on the surface of the first metal material 32, and the first metal material 32 and the second metal material 34 are joined together.

[0038] As Figure 2 and 3 shown, the second metal material 34 embedded in the surface of the first metal material 32 can be provided only on one surface side of the first metal material 32, or as Figure 4 and 5 shown, it can be provided on one surface side and the other surface side opposite to one surface of the first metal material 32. Moreover, the second metal material 34 can be as Figure 2 shown, provided at the central portion on one surface side of the first metal material 32, or as Figure 3 shown, provided at the end portion on one surface side of the first metal material 32. Here, the central portion and the end portion where the second metal material 34 is provided respectively refer to the central portion and the end portion in the width direction of the metal lead 30. It should be noted that Figure 3 in, the second metal material 34 is provided only at one end in the width direction of the electrode lead 30 on one surface of the first metal material 32, but it can also be provided at both ends in the width direction of the electrode lead 30. In addition, the second metal material 34 can be as Figure 4 shown, provided at the central portion on one surface side and the central portion on the other surface side of the first metal material 32, or as Figure 5 shown, provided at the central portion on one surface side of the first metal material 32 and at the end portion on the other surface side of the first metal material 32. It should be noted that Figure 5 in, the second metal material 34 is provided at both ends in the width direction on the other surface of the first metal material 32, but it can also be provided only at one end in the width direction.

[0039] Figure 6 It is a schematic cross-sectional view showing the joining state of the electrode lead shown in Figure 2 with an electrode or a battery case. Figure 7 It is a representation of Figure 3Schematic cross-sectional view of the joined state of the electrode lead with the electrode or battery case. The dashed box shown in the figure indicates the joined portion of the electrode lead with the electrode or battery case. As Figure 6 and Figure 7 shown, in the case of the electrode lead 30 where the second metal material 34 is provided on one surface side of the first metal material 32, at one end side in the length direction, the second metal material 34 provided on one surface side of the first metal material 32 is joined to the electrode (positive electrode 11 or negative electrode 12), and at the other end side in the length direction, the second metal material 34 provided on one surface of the first metal material 32 is joined to the battery case 15 (case main body 16 or sealing body 17).

[0040] Figure 8 is a schematic cross-sectional view showing Figure 4 the joined state of the electrode lead with the battery case, Figure 9 is a schematic cross-sectional view showing Figure 4 the joined state of the electrode lead with the electrode. Figure 10 is a schematic cross-sectional view showing Figure 5 the joined state of the electrode lead with the battery case, Figure 11 is a schematic cross-sectional view showing Figure 5 the joined state of the electrode lead with the electrode. The dashed box shown in the figure indicates the joined portion of the electrode lead with the electrode or battery case. In the case of the electrode lead 30 where the second metal material 34 is provided on one surface side and the other surface side of the first metal material 32, as Figure 8 and Figure 10 shown, at one end side in the length direction, the second metal material 34 provided on one surface side of the first metal material 32 is joined to the battery case 15 (case main body 16 or sealing body 17), and as Figure 9 and Figure 11 shown, at the other end side in the length direction, the second metal material 34 provided on the other surface side of the first metal material 32 is joined to the electrode (positive electrode 11 or negative electrode 12).

[0041] As a method for joining the second metal material 34 with the electrode and the battery case, for example, ultrasonic joining, resistance welding, laser welding, etc. are used. It should be noted that the joined portion of the electrode is preferably provided on the current collector (positive current collector or negative current collector) described later.

[0042] It can be considered that, by using, as the electrode lead 30, an inlaid clad material having a first metal material 32 and a second metal material 34 with a resistivity higher than that of the first metal material 32 and in which the second metal material 34 is embedded along the length direction on the surface of the first metal material 32, as in the present embodiment, compared with a conventional electrode lead (so-called Overlay Clad material) in which a second metal material 34 with a high resistivity is disposed on the surface of the first metal material 32, the ratio of the first metal material 32 with a low resistivity can be increased, and thus a reduction in the resistance of the electrode lead 30 can be achieved. In addition, it can be considered that, as in the present embodiment, by joining the second metal material 34 to the electrode (positive electrode 11 or negative electrode 12) and the battery case 15 (case main body 16 or sealing body 17) on one end side and the other end side of the electrode lead 30, oxidation of the surface of the first metal material 32 can be suppressed, and thus the joinability to the electrode and the battery case 15 can be maintained.

[0043] The width (length in the width direction) of the second metal material 34 is, for example, preferably in the range of 50 to 70% with respect to the width of the electrode lead 30. In addition, the thickness of the second metal material 34 is, for example, preferably in the range of 15 to 35% with respect to the thickness of the electrode lead 30.

[0044] The electrode lead 30 of the present embodiment can be applied to both the negative electrode lead 21 and the positive electrode lead 20, and is preferably applied to at least the negative electrode lead 21. The battery case 15 generally uses a metal material obtained by nickel-plating iron, and for the negative electrode current collector which is the joining portion on the negative electrode 12 side, copper foil is generally used. From the aspect of improving the joinability to such a battery case 15 and the negative electrode 12, the first metal material 32 constituting the negative electrode lead 21 preferably contains copper as the main component, and the second metal material 34 preferably contains nickel as the main component. When the electrode lead 30 of the present embodiment is applied to the positive electrode lead 20, the first metal material 32 preferably contains aluminum as the main component, and the second metal material 34 preferably contains nickel as the main component. The so-called main component means the component having the highest content among the contained metal components.

[0045] An example of the manufacturing method of the electrode lead 30 of the present embodiment will be described. A square column-shaped groove is formed along the length direction on the surface of the first metal material 32. Then, the second metal material 34 is embedded in the groove and cold-worked to obtain an inlaid clad material. Heat treatment of the inlaid clad material is preferably performed. Thereby, diffusion bonding at the boundary portion between the first metal material 32 and the second metal material 34 can be promoted. The heat treatment conditions can be appropriately set as long as they are respectively set to the optimum conditions according to the combination of the first metal material 32 and the second metal material 34. In this way, the electrode lead of the present embodiment can be manufactured.

[0046] Hereinafter, the positive electrode 11, the negative electrode 12, and the spacer 13 of the electrode body 14 will be described.

[0047] The positive electrode 11 has a positive electrode current collector and a positive electrode mixture layer formed on the positive electrode current collector. The positive electrode mixture layer is preferably formed on both sides of the positive electrode current collector. As the positive electrode current collector, a foil of a metal such as aluminum that is stable in the potential range of the positive electrode 11, a film having the metal disposed on the surface layer, or the like can be used. The positive electrode mixture layer contains, for example, a positive electrode active material, a binder, a conductive agent, and the like. For example, a positive electrode mixture paste containing a positive electrode active material, a binder, a conductive agent, and the like is applied to the positive electrode current collector, and after the coating film is dried, it is rolled to form a positive electrode mixture layer on the positive electrode current collector, whereby the positive electrode 11 can be manufactured.

[0048] Examples of the positive electrode active material contained in the positive electrode mixture layer include transition metal oxides containing transition metal elements such as Co, Mn, and Ni. The transition metal oxide is, for example, Li x CoO2, Li x NiO2, Li x MnO2, Li x Co y Ni 1-y O2, Li x Co y M 1-y O z 、Li x Ni 1-y M y O z 、Li x Mn2O4, Li x Mn 2-y M y O4, LiMPO4, Li2MPO4F (M: at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, B; 0 < x ≤ 1.2; 0 < y ≤ 0.9; 2.0 ≤ z ≤ 2.3). They can be used alone or in combination of multiple kinds. From the viewpoint of enabling high capacity of the secondary battery, the positive electrode active material preferably contains Li x NiO2, Li x Co y Ni 1-y O2, Li x Ni 1-y M y O zLithium nickel composite oxides such as (M: at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, B, 0 < x ≤ 1.2, 0 < y ≤ 0.9, 2.0 ≤ z ≤ 2.3), etc. On the particle surface of the lithium transition metal oxide, inorganic particles such as tungsten oxide, aluminum oxide, and compounds containing lanthanide elements can be fixed.

[0049] Examples of the conductive agent contained in the positive electrode binder layer include carbon materials such as carbon black (CB), acetylene black (AB), Ketjen black, carbon nanotubes (CNT), graphene, and graphite. They can be used alone or in combination of two or more.

[0050] Examples of the binder contained in the positive electrode binder layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, carboxymethyl cellulose (CMC) or its salts, and poly(ethylene oxide) (PEO). They can be used alone or in combination of two or more.

[0051] The negative electrode 12 has a negative electrode current collector and a negative electrode binder layer formed on the negative electrode current collector. The negative electrode binder layer is preferably formed on both sides of the negative electrode current collector. As the negative electrode current collector, foils of metals such as copper and copper alloys that are stable in the potential range of the negative electrode, films having such metals disposed on the surface layer, etc. can be used. The negative electrode binder layer contains, for example, a negative electrode active material, a binder, etc. For example, a negative electrode binder slurry containing a negative electrode active material, a binder, etc. is coated on the negative electrode current collector, and after the coating film is dried, it is calendered to form a negative electrode binder layer on the negative electrode current collector, whereby the negative electrode 12 can be manufactured.

[0052] The negative electrode active material contained in the negative electrode binder layer is not particularly limited as long as it can reversibly occlude and release lithium ions, and carbon-based active materials such as graphite are usually used. The graphite can be any of natural graphite such as flake graphite, massive graphite, and earthy graphite, massive artificial graphite, graphitized mesophase carbon microspheres, etc. artificial graphite. In addition, metals that alloy with Li such as Si and Sn, metal compounds containing Si, Sn, etc., and lithium titanium composite oxides can also be used as the negative electrode active material. As the negative electrode active material other than the carbon-based active material, a silicon-based active material is preferred. As the silicon-based active material, for example, a Si-containing compound represented by SiO x (0.5 ≤ x ≤ 1.6), or Li 2y SiO （2＋y）A Si-containing compound in which Si is dispersed in a lithium silicate phase, represented by (0 < y < 2). The content of the silicon-based active material in the negative electrode mixture layer is preferably, for example, 1% by mass to 15% by mass, more preferably 5% by mass to 10% by mass, relative to the total mass of the negative electrode active material.

[0053] Examples of the binder contained in the negative electrode mixture layer include the same binders as those in the positive electrode 11. In addition, a conductive agent may also be included in the negative electrode mixture layer. Examples of the conductive agent include the same conductive agents as those in the positive electrode 11.

[0054] The spacer 13 is, for example, a porous sheet having ion permeability and insulation properties. Specific examples of the porous sheet include microporous films, woven fabrics, non-woven fabrics, etc. As the material of the spacer, olefin-based resins such as polyethylene and polypropylene, cellulose, etc. are suitable. The spacer 13 may also be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin-based resin. In addition, it may be a multi-layer spacer including a polyethylene layer and a polypropylene layer, or a spacer in which a material such as an aromatic polyamide-based resin or ceramic is coated on the surface of the spacer 13.

[0055] Explanation of reference numerals

[0056] 10 Secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Spacer, 14 Electrode body, 15 Battery case, 16 Case main body, 17 Sealing body, 18, 19 Insulating plates, 20 Positive electrode lead, 21 Negative electrode lead, 22 Bulging portion, 23 Filter, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Electrode lead, 32 First metal material, 34 Second metal material.

Claims

1. A secondary battery, comprising an electrode body formed by winding a positive electrode and a negative electrode with a separator interposed therebetween, a battery case accommodating the electrode body, and an electrode lead that electrically connects the positive electrode or the negative electrode to the battery case. The electrode lead is an inlaid coating material having a first metal material and a second metal material having a resistivity higher than that of the first metal material, and the second metal material is embedded along the length direction of the electrode lead on the surface of the first metal material. On one end side in the length direction of the electrode lead, the second metal material is joined to the positive electrode or the negative electrode, and on the other end side in the length direction of the electrode lead, the second metal material is joined to the battery case.

2. The secondary battery according to claim 1, wherein the second metal material is provided only on one surface side of the first metal material.

3. The secondary battery according to claim 2, wherein in the width direction of the electrode lead, the second metal material is provided at the central portion on one surface side of the first metal material or at the end portion on one surface side of the first metal material.

4. The secondary battery according to claim 1, wherein the second metal material is provided on one surface side of the first metal material and on the other surface side opposite to the one surface side, on one end side of the electrode lead, the second metal material provided on one surface side of the first metal material is joined to the positive electrode or the negative electrode, and on the other end side of the first electrode lead, the second metal material provided on the other surface side of the first metal material is joined to the battery case.

5. The secondary battery according to claim 4, wherein in the width direction of the electrode lead, the second metal material is provided at the central portion on one surface side of the first metal material and at the central portion on the other surface side of the first metal material.

6. The secondary battery according to claim 4, wherein in the width direction of the electrode lead, the second metal material is provided at the end portion on one surface side of the first metal material and at the central portion on the other surface side of the first metal material.

7. The secondary battery according to any one of claims 1 to 6, wherein the electrode lead is a negative electrode lead.

8. The secondary battery according to claim 7, wherein the first metal material contains copper as a main component, and the second metal material contains nickel as a main component.

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