Non-aqueous electrolyte secondary battery

Abstract

The present invention provides a non-aqueous electrolyte secondary battery capable of suppressing the occurrence of scratches and breakage of a core body due to an electrode tab in a charge / discharge cycle, in a configuration provided with a wound-type electrode body. The non-aqueous electrolyte secondary battery is provided with a wound-type electrode body in which a first electrode and a second electrode having different polarities from each other are wound with a separator interposed therebetween. The first electrode (for example, a positive electrode (11)) has a core body (for example, a positive electrode core body (31)) and a mixture layer (for example, a positive electrode mixture layer (30)) formed on the surface of the core body. A core body exposed part where the core body is exposed (for example, a positive electrode core body exposed part (31a)) is formed on the surface of the first electrode. An electrode tab (for example, a positive electrode tab (19)) is joined to the core body exposed part. A metal foil (42) is laminated so as to cover at least partly the portion of the electrode tab that is disposed in the core body exposed part. A protective tape (40) is bonded so as to cover the core body exposed part, at least the portion of the electrode tab that is disposed in the core body exposed part, and the metal foil (42).

Description

Nonaqueous electrolyte secondary battery

[0001] This disclosure relates to a non-aqueous electrolyte secondary battery.

[0002] Conventionally, non-aqueous electrolyte secondary batteries are known to have an electrode body and an outer casing that houses the electrode body, and the electrode body is a wound type in which the positive electrode and negative electrode are wound around a separator. The positive electrode and negative electrode each have a composite layer containing an active material and a binder formed on both sides of a core body (current collector). The non-aqueous electrolyte secondary battery includes, for example, rectangular plate-shaped electrode tabs connected to the positive electrode and negative electrode, respectively, as lead wires for electrically connecting the electrode body to external terminals.

[0003] Patent Document 1 discloses a method for manufacturing a non-aqueous electrolyte secondary battery, in which core body exposed portions are formed on both the positive and negative electrodes, electrode tabs are joined to these core body exposed portions by welding or other means, and the electrode tabs are covered with protective tape.

[0004] Japanese Patent Publication No. 2004-311282

[0005] In non-aqueous electrolyte secondary batteries, repeated charging and discharging can generate stress due to the expansion and contraction of the positive and negative electrodes. In particular, with the recent increase in the capacity of non-aqueous electrolyte secondary batteries, the volume changes due to the expansion and contraction of the positive and negative electrodes during charging and discharging have become larger. When the volume changes of the positive and negative electrodes during charging and discharging become large, stress is applied to the core, especially from the outer edge of the electrode tab bonded to the surface of the exposed core portion of the inner electrode, which may cause partial damage or cuts to the core. Damage or cuts to the core can increase the electrical resistance of the electrode, potentially leading to a deterioration in battery performance.

[0006] The object of this disclosure is to provide a non-aqueous electrolyte secondary battery that has a wound electrode body configuration and can suppress an increase in the electrical resistance of the electrode even if damage or breakage of the core body occurs due to the electrode tabs during the charge-discharge cycle.

[0007] This disclosure relates to a non-aqueous electrolyte secondary battery comprising a wound electrode body in which a first electrode and a second electrode having opposite polarities are wound around a separator, wherein the first electrode has a core body and a composite layer formed on the surface of the core body, a core body exposed portion is formed on the surface of the first electrode in which the core body is exposed, an electrode tab is bonded to the core body exposed portion, a metal foil is bonded to the electrode tab and the core body exposed portion, and a protective tape is attached so as to cover the core body exposed portion, at least the portion of the electrode tab that is positioned on the core body exposed portion, and the metal foil.

[0008] The non-aqueous electrolyte secondary battery according to this disclosure provides a non-aqueous electrolyte secondary battery that, in a configuration with a wound electrode body, can suppress an increase in the electrical resistance of the electrode even if damage or breakage of the core body occurs due to the electrode tabs during the charge-discharge cycle.

[0009] This is an axial cross-sectional view of a non-aqueous electrolyte secondary battery according to an embodiment of the present disclosure. This is a schematic plan view of an example of the longitudinal middle portion of the positive electrode when the positive electrode of Figure 1, which is the first electrode, is viewed in the thickness direction while unfolded along the planar direction. This is a cross-sectional view taken along line A-A' in Figure 2. This is a schematic plan view of the longitudinal middle portion of the positive electrode when the positive electrode, which is the first electrode in a conventional non-aqueous electrolyte secondary battery, is viewed in the thickness direction while unfolded along the planar direction. This is a schematic plan view of another example of the longitudinal middle portion of the positive electrode when the positive electrode of Figure 1, which is the first electrode, is viewed in the thickness direction while unfolded along the planar direction. This is a schematic plan view of another example of the longitudinal middle portion of the positive electrode when the positive electrode of Figure 1, which is the first electrode, is viewed in the thickness direction while unfolded along the planar direction. This is a cross-sectional view taken along line A-A' in Figure 6. This is a schematic plan view of another example of the longitudinal middle portion of the positive electrode when the positive electrode of Figure 1, which is the first electrode, is viewed in the thickness direction while unfolded along the planar direction.

[0010] Embodiments of this disclosure will be described below. These embodiments are examples of implementing this disclosure, and this disclosure is not limited to these embodiments.

[0011] Hereinafter, embodiments of the non-aqueous electrolyte secondary battery according to this disclosure will be described in detail with reference to the drawings.

[0012] It is intended from the outset that new embodiments can be constructed by appropriately combining the characteristic features of the embodiments and modifications described below. In the following embodiments, the same reference numerals are used for the same components in the drawings, and redundant explanations are omitted. In addition, multiple drawings include schematic diagrams, and the dimensional ratios such as length, width, and height of each component do not necessarily match between different drawings. Furthermore, among the components described below, components that are not described in the independent claim indicating the highest-level concept are optional components and are not essential components. Moreover, this disclosure is not limited to the embodiments and modifications described below, and various improvements and changes are possible within the scope of the claims of this application and to an equal extent.

[0013] Figure 1 is an axial cross-sectional view of a non-aqueous electrolyte secondary battery 10, which is an example of an embodiment. Figure 2 is a schematic plan view of the longitudinal middle portion of the positive electrode 11 when viewed in the thickness direction while the positive electrode 11 is unfolded along the planar direction.

[0014] As shown in Figure 1, the non-aqueous electrolyte secondary battery 10 has a strip-shaped positive electrode 11 and a negative electrode 12, and a separator 13, and comprises a wound electrode body 14 in which the positive electrode 11 and the negative electrode 12 are wound longitudinally via the separator 13. The non-aqueous electrolyte secondary battery 10 also comprises a bottomed cylindrical outer casing 15 that houses the electrode body 14, and a sealing body 16 that closes the opening of the outer casing 15. The outer casing 15 houses the electrode body 14 together with the non-aqueous electrolyte. In the example in Figure 1, the positive electrode 11 corresponds to the first electrode, and the negative electrode 12 corresponds to the second electrode.

[0015] The outer casing 15 is a bottomed cylindrical metal container, and has a cylindrical portion 15a and a bottom provided at one end of the cylindrical portion 15a in the winding axis direction α of the electrode body 14. The outer casing 15 has a grooved portion 21 formed at the open end of the outer casing 15 on the other end of the cylindrical portion 15a in the winding axis direction α. ​​The grooved portion 21 is formed in an annular shape along the circumferential direction of the outer casing 15 by pressing the cylindrical portion 15a from the outside, and supports the sealing body 16 on its upper surface. For the sake of explanation, in the following, the side of the non-aqueous electrolyte secondary battery 10 with the sealing body 16 will be referred to as the upper side, and the bottom side of the outer casing 15 will be referred to as the lower side.

[0016] Non-aqueous electrolytes have ionic conductivity (for example, lithium ion conductivity). A non-aqueous electrolyte comprises a non-aqueous solvent (also called an organic solvent) and an electrolyte salt dissolved in the non-aqueous solvent. Non-aqueous electrolytes are not limited to liquid electrolytes (non-aqueous electrolyte solutions), but may also be solid electrolytes using gel-like polymers or the like. A non-aqueous electrolyte secondary battery 10 is, for example, a lithium-ion battery.

[0017] Examples of electrolyte salts include lithium tetrafluoroborate (LiBF). ４ ), lithium hexafluorophosphate (LiPF) ６ Examples include lithium salts such as )

[0018] Examples of non-aqueous solvents include esters such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP), as well as ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may also contain halogen-substituted solvents in which at least some of the hydrogen atoms of these solvents are replaced with halogen atoms such as fluorine atoms.

[0019] Examples of halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated linear carbonates, and fluorinated linear carboxylic acid esters such as methyl fluoropropionate (FMP). In terms of suppressing the deterioration of the charge-discharge cycle characteristics of non-aqueous electrolyte secondary batteries or improving the output characteristics, the non-aqueous electrolyte preferably contains 5% by mass or more of FEC relative to the mass of the non-aqueous electrolyte, and more preferably contains 5% to 15% by mass of FEC.

[0020] Examples of solid electrolytes include solid or gel-like polymer electrolytes and inorganic solid electrolytes. Polymer electrolytes include, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. Examples of matrix polymers include polymer materials that absorb non-aqueous solvents and gel. Examples of polymer materials include fluororesins, acrylic resins and polyether resins. Examples of inorganic solid electrolytes include materials known from all-solid-state lithium-ion secondary batteries (e.g., oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.).

[0021] As described above, the electrode body 14 has a wound structure in which a positive electrode 11 and a negative electrode 12 are wound around a separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 are all elongated strip-shaped bodies, and are alternately stacked in the radial direction β of the electrode body 14 by being wound in a spiral in the longitudinal direction. The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to suppress lithium deposition. That is, the negative electrode 12 is formed to be longer than the positive electrode 11 in both the longitudinal and short-range directions of the electrode plate. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and for example, two separators are arranged so as to sandwich the positive electrode 11.

[0022] Examples of the separator 13 include porous sheets having ion permeability and insulating properties. Examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Examples of materials for the separator 13 include resins such as polyethylene and polypropylene olefin resins. The thickness of the separator 13 is, for example, 10 μm to 50 μm.

[0023] A positive electrode tab 19 and a negative electrode tab 20 are connected to the electrode assembly 14. The positive electrode tab 19 electrically connects the positive electrode 11 and the sealing body 16. The positive electrode tab 19 is located at a substantially intermediate portion of the positive electrode 11 in the longitudinal direction of the electrode plate, at a position distant from the winding start end and the winding end end of the electrode assembly 14, and is joined to the exposed portion of the positive electrode core provided at a substantially central portion in the radial direction β of the electrode assembly 14. In the example shown in FIG. 1, the positive electrode tab 19 extends toward the sealing body 16 through the opening of the upper insulating plate 17 and is joined to the lower surface of the sealing body 16, such that the sealing body 16 serves as a positive electrode terminal. The positive electrode tab 19 corresponds to an electrode tab. The positive electrode tab 19 is, for example, a rectangular plate-shaped conductive member, and has a thickness larger than the thickness of the positive electrode core described later. The thickness of the positive electrode tab 19 is, for example, 120 to 150 μm. The constituent material of the positive electrode tab is not particularly limited. The positive electrode tab 19 is made of, for example, a metal containing aluminum as a main component (e.g., 95% by mass or more of the entire material).

[0024] The negative electrode tab 20 is joined to an exposed portion of the negative electrode core provided at a winding start side end, which is one end portion in the longitudinal direction of the electrode plate of the negative electrode 12 located on the winding start side of the negative electrode 12. In the example shown in FIG. 1, the negative electrode tab 20 passes through the through-hole of the annular lower insulating plate 18, is bent along the inner surface of the bottom of the exterior body 15, and is connected to the inner surface of the bottom of the exterior body 15 by welding or the like, such that the exterior body 15 serves as a negative electrode terminal. The negative electrode tab 20 is, for example, a rectangular plate-shaped conductive member, and has a thickness larger than the thickness of the negative electrode core described later. The thickness of the negative electrode tab 20 is, for example, 80 to 100 μm. The constituent material of the negative electrode tab 20 is not particularly limited. The negative electrode tab 20 is made of, for example, a metal containing nickel or copper as a main component (e.g., 95% by mass or more of the entire material), or a metal containing both nickel and copper.

[0025] The negative electrode 12 is disposed on the outermost peripheral surface of the electrode assembly 14, and a portion where the surface of the negative electrode core constituting the negative electrode 12 is exposed is in contact with the inner peripheral surface of the exterior body 15. Thereby, together with the winding start side end of the negative electrode 12 to which the negative electrode tab 20 is connected, the winding end side end of the negative electrode 12 is electrically connected to the exterior body 15, so that good current collection performance can be ensured.

[0026] An annular gasket 27 is interposed between the outer package 15 and the sealing body 16. The sealing body 16 is caulked and fixed between the upper end of the outer package 15 and the grooved portion 21 via the gasket 27. This seals the inside of the battery.

[0027] The sealing body 16 has a structure in which an inner terminal plate 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26 are laminated in this order from the electrode body 14 side. Each member constituting the sealing body 16 has a disc shape or a ring shape, and the members except the insulating member 24 are electrically connected to each other. The cap 26 has an annular flange on the outer peripheral side, and has a hat shape in which a cylindrical portion with a closed upper end is provided at the center. The inner terminal plate 22 has a center hole penetrating vertically. The lower valve body 23 and the upper valve body 25 are connected to each other at their respective central portions, and the insulating member 24 is interposed between their respective peripheral edge portions. On the flange portion of the sealing body 16, the respective members constituting the sealing body 16 are overlapped in the axial direction.

[0028] When the internal pressure of the battery rises, the lower valve body 23 deforms so as to push the upper valve body 25 toward the cap 26 side and breaks, thereby cutting off the current path between the lower valve body 23 and the upper valve body 25. When the internal pressure further rises, the upper valve body 25 breaks, and gas is discharged from the opening 26a of the cap 26.

[0029] Fig. 2 is a schematic plan view showing an example of a longitudinal intermediate portion when the positive electrode 11 of Fig. 1, which is the first electrode, is viewed in the thickness direction in an unfolded state along the planar direction. Fig. 3 shows a cross-sectional view taken along line A-A' in Fig. 2.

[0030] The positive electrode 11 includes a strip-shaped positive electrode core 31, and positive electrode mixture layers 30 formed on both surfaces of the positive electrode core 31. In Fig. 2, only the positive electrode mixture layer 30 formed on one surface in the thickness direction of the positive electrode core 31 is shown, but as shown in Fig. 3, the positive electrode mixture layer 30 is similarly formed on the other surface in the thickness direction of the positive electrode core 31.

[0031] Examples of the positive electrode core 31 include foils of metals that are as stable as possible within the potential range of the positive electrode 11, such as aluminum and aluminum alloys, or films of resins with the metal disposed on the surface layer. The positive electrode core 31 is preferably a metal foil containing aluminum or an aluminum alloy as a main component (for example, 95% by mass or more of the total). The thickness of the positive electrode core 31 is, for example, 5 μm to 30 μm.

[0032] The positive electrode mixture layer 30 contains, for example, a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF), and is preferably formed on both surfaces of the positive electrode core. The thickness of the positive electrode mixture layer 30 is, for example, 40 μm to 100 μm.

[0033] Examples of the positive electrode active material contained in the positive electrode mixture layer 30 include lithium transition metal composite oxides containing transition metal elements such as Co, Mn, and Ni. Examples of the lithium transition metal composite oxide include Li ｘ CoO ２ , Li ｘ NiO ２ , Li ｘ MnO ２ , Li ｘ Co ｙ Ni １－ｙ O ２ , Li ｘ Co ｙ M １－ｙ O ｚ , Li ｘ Ni １－ｙ M ｙ O ｚ , Li ｘ Mn ２ O ４ , Li ｘ Mn ２－ｙ M ｙ O ４ , LiMPO ４ , Li ２ MPO ４ F (wherein M is at least one selected from the group consisting of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb and B, 0 < x ≤ 1.2, 0 < y ≤ 0.9, 2.0 ≤ z ≤ 2.3), and the like. These may be used alone, or may be used in combination of two or more.

[0034] In terms of being able to increase the capacity of the non-aqueous electrolyte secondary battery 10, it is preferable that the positive electrode active material contains a lithium nickel composite oxide. As for the lithium nickel composite oxide, Li ｘ NiO ２ Li ｘ Co ｙ Ni １－ｙ O ２ Li ｘ Ni １－ｙ M ｙ O ｚ Examples include (where M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B, with 0 < x ≤ 1.2, 0 < y ≤ 0.9, and 2.0 ≤ z ≤ 2.3). The higher the Ni content of lithium nickel composite oxide, the higher the capacity.

[0035] Examples of conductive agents included in the positive electrode mixture layer 30 include carbon black such as acetylene black and Ketjenblack, graphite, carbon nanotubes (CNTs), carbon nanofibers, graphene, metal fibers, metal powders, and conductive whiskers. These may be used individually or in combination of two or more types.

[0036] Examples of binders included in the positive electrode mixture layer 30 include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), and resins such as polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. These may be used individually or in combination of two or more types.

[0037] A positive electrode core exposed portion 31a is formed on a part of the surface of the positive electrode 11, and a positive electrode tab 19 is connected to the positive electrode core exposed portion 31a.

[0038] The positive electrode 11 can be manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc., to the surface of the positive electrode core 31, drying the coating, and then rolling the coating using a roller or the like. The exposed portion 31a of the positive electrode core is provided, for example, by intermittent coating, where the positive electrode mixture slurry is not applied to a part of the positive electrode core 31. The positive electrode tab 19 can be directly joined to the exposed portion 31a of the positive electrode core by, for example, ultrasonic welding.

[0039] The negative electrode 12 comprises a strip-shaped negative electrode core and negative electrode mixture layers formed on both sides of the negative electrode core. Examples of the negative electrode core include a metal foil that is as stable as possible within the potential range of the negative electrode 12, such as copper or a copper alloy, or a film of resin or other material with that metal arranged on its surface. The negative electrode core is preferably a metal foil with copper or a copper alloy as its main component (for example, 95% or more by mass). The thickness of the negative electrode core is, for example, 5 μm to 30 μm.

[0040] The negative electrode mixture layer preferably comprises, for example, a negative electrode active material and a binder such as styrene-butadiene rubber (SBR), and is formed on both sides of the negative electrode core. The thickness of the negative electrode mixture layer is, for example, 40 μm to 100 μm. As the negative electrode active material, a material capable of reversibly intercalating and releasing lithium ions can be used, such as carbon materials and silicon materials.

[0041] Examples of carbon materials used as negative electrode active materials include graphite. Examples of graphite include natural graphite such as flake graphite, lump graphite, and earthy graphite, as well as artificial graphite such as lump graphite and graphitized mesophase carbon microbeads.

[0042] As the negative electrode active material, metals that alloy with Li such as Si and Sn, metal compounds containing Si and Sn, silicon materials such as lithium titanium composite oxide, and tin materials may be used. For example, SiO ｘ Si-containing compounds represented by (0.5 ≤ x ≤ 1.6), Li ２ｙ SiO （２＋ｙ）A Si-containing compound in which fine Si particles are dispersed in a lithium silicate phase represented by (0 < y < 2), or a Si-containing compound in which Si is dispersed in a carbon material, may be used in combination with a carbon material such as graphite.

[0043] Examples of binders included in the negative electrode mixture layer include styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxymethylcellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts (such as PAA-Na, PAA-K, or partially neutralized salts), and polyvinyl alcohol (PVA). These may be used individually or in combination of two or more types.

[0044] The negative electrode 12 can be manufactured, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to the surface of the negative electrode core, drying the coating, and then rolling the coating using a roller or the like.

[0045] A portion of the surface of the negative electrode 12 is formed where the negative electrode core is exposed, and a negative electrode tab 20 is connected to this exposed portion. The exposed portion of the negative electrode core is formed, for example, by intermittent coating, where the negative electrode mixture slurry is not applied to a portion of the negative electrode core. The negative electrode tab 20 may be directly joined to the negative electrode core by, for example, ultrasonic welding.

[0046] As shown in Figures 2 and 3, a positive electrode core exposed portion 31a is formed on a part of the positive electrode 11 in the longitudinal direction X, for example, approximately in the middle, with a predetermined width in the longitudinal direction X and extending over a part of the short direction Y, that is, for a predetermined length from the side from which the positive electrode tab 19 extends in the short direction Y, where the surface of the metal constituting the positive electrode core 31 is exposed. The positive electrode core exposed portion 31a is formed on both sides of the positive electrode 11, facing each other with the positive electrode core 31 in between. The positive electrode core exposed portion 31a is the part to which the positive electrode tab 19 is joined, and is the part where the surface of the positive electrode core 31 is not covered by the positive electrode mixture layer 30. The longitudinal direction X of the positive electrode 11 corresponds to the winding direction of the electrode body 14, and the short direction Y of the positive electrode 11 corresponds to the axial direction α (Figure 1) of the electrode body.

[0047] In the example shown in Figure 2, the exposed positive electrode core portion 31a is in contact with only one end of the positive electrode 11 in the short-side direction Y (the side from which the positive electrode tab 19 extends, the upper end in the example of Figure 2), and does not extend to the other end of the positive electrode 11 in the short-side direction Y (the lower end in the example of Figure 2). As a result, the positive electrode mixture layer 30 exists between the other end of the positive electrode 11 in the short-side direction Y and the exposed positive electrode core portion 31a, thereby increasing the battery capacity of the non-aqueous electrolyte secondary battery 10.

[0048] The exposed portion 31a of the positive electrode core 31 may be formed at a location other than approximately the middle of the longitudinal direction X of the electrode plate, for example, it may be formed near the end of the longitudinal direction X of the electrode plate.

[0049] The positive electrode tab 19 is joined to the exposed portion 31a of the positive electrode core by welding, such as ultrasonic welding. The positive electrode tab 19 extends from one end (upper end) of the electrode plate in the short-side direction Y of the positive electrode core 31. In the example shown in Figure 3, the positive electrode tab 19 is joined to the surface that becomes the inner circumference side of the positive electrode core 31 when wound. As shown in Figure 3, the positive electrode tab 19 is formed in a strip shape with a substantially rectangular cross-section when unfolded along the planar direction of the positive electrode 11, for example. As described above, the positive electrode tab 19 has a thickness greater than the thickness of the positive electrode core 31.

[0050] Here, as shown in Figures 2 and 3, in this embodiment, the metal foil 42 is bonded to the positive electrode tab 19 and the exposed portion 31a of the positive electrode core. For example, the metal foil 42 is laminated so as to cover at least a portion of the positive electrode tab 19 that is positioned on the exposed portion 31a of the positive electrode core, and is bonded to the positive electrode tab 19 and the exposed portion 31a of the positive electrode core. Furthermore, protective tape 40 is attached so as to cover the exposed portion 31a of the positive electrode core, at least the portion of the positive electrode tab 19 that is positioned on the exposed portion 31a of the positive electrode core, and the metal foil 42. With this configuration, even if the core (e.g., positive electrode core 31) is damaged or cut by the electrode tab (e.g., positive electrode tab 19) during a charge-discharge cycle, conductivity is ensured by the metal foil 42, and an increase in the electrical resistance of the electrode can be suppressed.

[0051] In the conventional technology, as shown in Figure 4, a positive electrode tab 19 is attached to the exposed portion 31a of the positive electrode core, and a protective tape 40 is applied to cover the exposed portion 31a of the positive electrode core and at least the portion of the positive electrode tab 19 that is positioned on the exposed portion 31a of the positive electrode core. Therefore, if a cut or damage occurs to the positive electrode core 31, it is not possible to suppress the increase in the electrical resistance of the electrode as in this embodiment.

[0052] A similar phenomenon to that in the positive electrode 11 may occur in the negative electrode 12 due to the negative electrode tab 20. In this case, the first electrode can be designated as the negative electrode 12, and the metal foil 42 can be joined to the negative electrode tab 20 and the exposed portion of the negative electrode core.

[0053] The metal foil 42 can be joined to the positive electrode tab 19 and the exposed portion 31a of the positive electrode core by welding, such as ultrasonic welding. For example, as shown in Figure 8, the metal foil 42 can be joined to the positive electrode core 31 and the positive electrode tab 19 by welding at three locations along the longitudinal direction X of the electrode plate (winding direction of the electrode body 14, i.e., the positive electrode 11): between the metal foil 42 and the positive electrode core 31, between the metal foil 42 and the positive electrode tab 19, and between the metal foil 42 and the positive electrode core 31.

[0054] Examples of metal foils 42 covering the positive electrode tab 19 include aluminum, aluminum alloy, or other metal foils that are as stable as possible within the potential range of the positive electrode 11, or films such as resin with that metal arranged on the surface. When the metal foil 42 covers the positive electrode tab 19, it is preferable that the foil has the same metal as the positive electrode core 31 as its main component (for example, 95% by mass or more of the total). Therefore, it is preferable that the metal foil 42 has aluminum or aluminum alloy as its main component (for example, 95% by mass or more of the total). The thickness of the metal foil 42 may be 50% or less of the thickness of the positive electrode tab 19, or it may be 30% or less. The thickness of the metal foil 42 is, for example, 10 μm to 30 μm, and is preferably the same as the thickness of the positive electrode core 31.

[0055] Examples of metal foils 42 covering the negative electrode tab include copper, copper alloys, or other metal foils that are as stable as possible within the potential range of the negative electrode 12, or films such as resin with that metal arranged on the surface. When the metal foil 42 covers the negative electrode tab, it is preferable that the foil has the same metal as the negative electrode core as its main component (for example, 95% by mass or more of the total). Therefore, it is preferable that the metal foil 42 has copper or a copper alloy as its main component (for example, 95% by mass or more of the total). The thickness of the metal foil 42 may be 50% or less of the thickness of the negative electrode tab, or it may be 30% or less. The thickness of the metal foil 42 is, for example, 5 μm to 15 μm, and it is preferable that it is the same as the thickness of the negative electrode core.

[0056] As shown in Figure 5, the end portion of the positive electrode tab 19 extends from the end of the metal foil 42 in the short direction Y of the electrode plate and does not need to be covered by the metal foil 42.

[0057] As shown in Figures 2 and 3, the metal foil 42 should be provided within the range of the core exposed portion, such as the positive electrode core exposed portion 31a, so as to cover at least a portion of the part of the electrode tab, such as the positive electrode tab 19, that is located on the core exposed portion. In other words, the length of the metal foil 42 in the short direction Y of the electrode plate should be shorter than the length of the core exposed portion in the short direction Y of the electrode plate, and the length of the metal foil 42 in the long direction X of the electrode plate should be shorter than the length of the core exposed portion in the long direction X of the electrode plate.

[0058] The exposed positive electrode core portion 31a may be formed to extend in the short-side direction Y of the electrode plate and cover a part of the positive electrode mixture layer 30, as shown in Figure 6. That is, the length of the metal foil 42 in the short-side direction Y of the electrode plate may be longer than the length of the exposed core portion in the short-side direction Y of the electrode plate.

[0059] The ratio W2 / W1 of the length W2 of the exposed portion 31a of the positive electrode core in the short direction Y of the positive electrode 11 to the total length W1 in the short direction Y of the positive electrode 11 is, for example, 5% to 50%, and may be 5% to 30%.

[0060] As shown in Figures 2 and 3, the protective tape 40 is attached so as to cover the exposed positive electrode core portion 31a on both the inner and outer surfaces of the positive electrode 11 when it is wound. Specifically, the protective tape 40 is attached so as to cover the surface of at least the portion of the positive electrode tab 19 that is on the inner side of the positive electrode 11 when it is wound, the entire surface of the metal foil 42, and the entire surface of the exposed positive electrode core portion 31a. In addition, the protective tape 40 is attached so as to cover the entire surface of the exposed positive electrode core portion 31a that is on the outer side of the positive electrode 11 when it is wound.

[0061] As shown in Figures 2 and 3, the protective tape 40 may be attached so as to cover the positive electrode mixture layer 30 around the positive electrode core exposed portion 31a. Specifically, the protective tape 40 may be attached so as to cover at least the surface of the portion of the positive electrode tab 19 that is positioned over the positive electrode core exposed portion 31a when wound, the entire surface of the metal foil 42, the entire surface of the positive electrode core exposed portion 31a, and the portion of the positive electrode mixture layer 30 adjacent to the positive electrode core exposed portion 31a. Alternatively, the protective tape 40 may be attached so as to cover the entire surface of the positive electrode core exposed portion 31a that is on the outer circumference of the positive electrode 11 when wound, and the portion of the positive electrode mixture layer 30 adjacent to the positive electrode core exposed portion 31a.

[0062] The protective tape 40 is an insulating tape having insulating properties. The protective tape 40 is an insulating member that prevents the positive electrode tab 19 and the exposed portion 31a of the positive electrode core from short-circuiting with the negative electrode mixture layer of the opposing negative electrode 12 via the separator 13.

[0063] The protective tape 40 has, for example, a base layer and an adhesive layer formed on one surface of the base layer. A heat-resistant layer containing inorganic particles such as metal oxides may be provided between the base layer and the adhesive layer.

[0064] The base layer can be any insulating resin, such as PPS (polyphenylene sulfide), PEEK (polyether ether ketone), PI (polyimide), PP (polypropylene), PET (polyethylene terephthalate), and PBT (polybutylene terephthalate). Among these, PI, which has relatively high hardness, is preferred from the standpoint of protecting the exposed portion 31a of the positive electrode core. The thickness of the base layer is, for example, 5 μm to 50 μm.

[0065] The adhesive layer is the portion for attaching the protective tape 40 to the positive electrode 11. The adhesive layer includes, for example, at least one of a rubber-based polymer and an acrylic-based polymer. Since the rubber-based polymer and the acrylic-based polymer are adhesive, the protective tape 40 can be adhered to the surface of the positive electrode 11. The adhesive layer may further include, for example, a silicone-based polymer. The thickness of the adhesive layer is, for example, 1 μm to 30 μm.

[0066] As described above, the non-aqueous electrolyte secondary battery of this disclosure, in a configuration with a wound electrode body, can suppress deterioration of battery performance due to increased electrical resistance of the electrodes even if damage or breakage of the core body occurs due to the electrode tabs during the charge-discharge cycle.

[0067] 10 Non-aqueous electrolyte secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Outer casing, 15a Cylindrical part, 16 Sealing body, 17 Upper insulating plate, 18 Lower insulating plate, 19 Positive electrode tab, 20 Negative electrode tab, 21 Grooved part, 22 Internal terminal plate, 23 Lower valve body, 24 Insulating member, 25 Upper valve body, 26 Cap, 26a Opening, 27 Gasket, 30 Positive electrode mixture layer, 31 Positive electrode core body, 31a Positive electrode core body exposed part, 40 Protective tape, 42 Metal foil, 44 Welded part.

Claims

1. A non-aqueous electrolyte secondary battery comprising a wound electrode body in which a first electrode and a second electrode having opposite polarities are wound around a separator, wherein the first electrode comprises a core body and a composite layer formed on the surface of the core body, a core body exposed portion is formed on the surface of the first electrode where the core body is exposed, an electrode tab is bonded to the core body exposed portion, a metal foil is bonded to the electrode tab and the core body exposed portion, and a protective tape is attached so as to cover the core body exposed portion, at least the portion of the electrode tab that is positioned on the core body exposed portion, and the metal foil.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the thickness of the metal foil is 50% or less of the thickness of the electrode tab.

3. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the metal foil is joined at three locations along the winding direction of the electrode body: between the metal foil and the core body, between the metal foil and the electrode tab, and between the metal foil and the core body.

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