Nonaqueous electrolyte secondary battery

Abstract

Provided is a nonaqueous electrolyte secondary battery that has a reduced risk of short circuiting. A nonaqueous electrolyte secondary battery according to one aspect of the present disclosure comprises: an electrode body in which a first electrode and a second electrode that are strip-shaped and have different polarities are wound in the longitudinal direction with a separator therebetween; and an exterior body that accommodates the electrode body. The first electrode includes a current collector and a mixture layer formed on a surface of the current collector. On both surfaces of the first electrode, a pair of current collector exposed portions of the current collector are formed so as to overlap each other in the thickness direction of the first electrode, and a pair of protective tapes covering the current collector exposed portions are disposed so as to overlap each other in the thickness direction of the first electrode. The pair of protective tapes each include a protruding portion protruding from the current collector in the widthwise direction of the first electrode, and are adhered to each other at the protruding portions.

Description

Nonaqueous electrolyte secondary battery

[0001] The present disclosure relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery including a wound electrode assembly.

[0002] Conventionally, non-aqueous electrolyte secondary batteries have been widely used, in which a wound electrode assembly, in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator interposed therebetween, is housed in an outer casing. Patent Document 1 discloses a technique in which exposed portions where the current collectors are exposed are formed on each of the positive electrode and the negative electrode, leads are welded to these exposed portions, and the leads are then covered with protective tape.

[0003] Japanese Patent Application Laid-Open No. 2004-311282

[0004] The inventors' investigations revealed that repeated expansion and contraction of the electrode assembly due to charging and discharging of the battery can cause peeling or cracks in the mixture layer, originating from the edge of the adhesive layer of the protective tape, which can lead to a short circuit. The technology disclosed in Patent Document 1 does not consider the risk of short circuits, and there is still room for improvement.

[0005] An object of the present disclosure is to provide a non-aqueous electrolyte secondary battery with a reduced risk of short circuit.

[0006] A nonaqueous electrolyte secondary battery according to one aspect of the present disclosure includes an electrode assembly in which strip-shaped first and second electrodes having different polarities are wound longitudinally with a separator interposed therebetween, and an exterior body that houses the electrode assembly, wherein the first electrode has a current collector and a mixture layer formed on the surface of the current collector, and a pair of current collector exposed portions where the current collector is exposed are formed on both sides of the first electrode so as to overlap each other in the thickness direction of the first electrode, and a pair of protective tapes covering the current collector exposed portions are arranged so as to overlap each other in the thickness direction of the first electrode, and the pair of protective tapes include protrusions that protrude from the current collector in the short direction of the first electrode and are bonded to each other at the protrusions.

[0007] The nonaqueous electrolyte secondary battery according to the present disclosure reduces the risk of short circuits and is therefore excellent in safety.

[0008] 1 is an axial cross-sectional view of a cylindrical secondary battery that is an example of an embodiment. FIG. 2 is a perspective view of a wound electrode body provided in the secondary battery shown in FIG. 1. FIG. 3 is a front view showing a positive electrode and a negative electrode that constitute an electrode body that is an example of an embodiment in a developed state. FIG. 4 is a cross-sectional view taken along line A-A in FIG. 3. FIG. 5 is an enlarged view of the periphery of an exposed portion of a positive electrode current collector in FIG. 3. FIG. 6 is a view corresponding to FIG. 5 in another example of an embodiment.

[0009] Hereinafter, an example of an embodiment of a cylindrical secondary battery according to the present disclosure will be described in detail with reference to the drawings. In the following description, specific shapes, materials, numerical values, directions, etc. are examples for facilitating understanding of the present invention and can be appropriately changed according to the specifications of the cylindrical secondary battery. Furthermore, when the following description includes multiple embodiments and modified examples, it is assumed from the beginning that the characteristic portions of those embodiments and modified examples can be appropriately combined and used.

[0010] FIG. 1 is an axial cross-sectional view of a cylindrical secondary battery 10 according to an embodiment. The secondary battery 10 shown in FIG. 1 includes an electrode assembly 14 and a nonaqueous electrolyte (not shown) housed in an outer casing 15. The electrode assembly 14 has a wound structure in which a strip-shaped positive electrode 11 and a strip-shaped negative electrode 12 are wound with a separator 13 interposed therebetween. Examples of nonaqueous solvents (organic solvents) for the nonaqueous electrolyte include carbonates, lactones, ethers, ketones, esters, and the like. Two or more of these solvents can be mixed together. When two or more solvents are mixed together, a mixed solvent containing a cyclic carbonate and a chain carbonate is preferably used. For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and the like can be used as the cyclic carbonate, and dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and the like can be used as the chain carbonate. The electrolyte salt of the non-aqueous electrolyte is LiPF ６ , LiBF ４ , LiCF ３ SO ３etc., and mixtures thereof can be used. The amount of electrolyte salt dissolved in the non-aqueous solvent can be, for example, 0.5 to 2.0 mol / L. For convenience of explanation, the following description will be given with the sealing body 16 side as the "top" and the bottom side of the exterior body 15 as the "bottom."

[0011] The open end of the exterior body 15 is sealed with the sealing body 16, thereby sealing the interior of the secondary battery 10. Insulating plates 17 and 18 are provided above and below the electrode body 14. The positive electrode lead 19 extends upward through a through hole in the insulating plate 17 and is welded to the underside of a filter 22, which is the bottom plate of the sealing body 16. In the secondary battery 10, a cap 26, which is the top plate of the sealing body 16 and is electrically connected to the filter 22, serves as the positive electrode terminal. On the other hand, the negative electrode lead 20 extends through a through hole in the insulating plate 18 to the bottom side of the exterior body 15 and is welded to the inner bottom surface of the exterior body 15. In the secondary battery 10, the exterior body 15 serves as the negative electrode terminal. Note that when the negative electrode lead 20 is provided at the outer end of the winding, the negative electrode lead 20 passes outside the insulating plate 18, extends to the bottom side of the exterior body 15, and is welded to the inner bottom surface of the exterior body 15.

[0012] The exterior body 15 is, for example, a cylindrical metal exterior can with a bottom. A gasket 27 is provided between the exterior body 15 and the sealing body 16 to ensure the airtightness of the interior of the secondary battery 10. The exterior body 15 has a grooved portion 21 that supports the sealing body 16, formed, for example, by pressing the side surface from the outside. The grooved portion 21 is preferably formed in an annular shape along the circumferential direction of the exterior body 15, and supports the sealing body 16 on its upper surface.

[0013] The sealing body 16 includes a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26, which are stacked in this order from the electrode body 14 side. Each component of the sealing body 16 has, for example, a disk or ring shape, and all components except for the insulating member 24 are electrically connected to each other. The lower valve body 23 and the upper valve body 25 are connected to each other at their respective centers, with the insulating member 24 interposed between their respective peripheral edges. If the internal pressure of the battery increases due to abnormal heat generation, for example, the lower valve body 23 may rupture, causing the upper valve body 25 to bulge toward the cap 26 and separate from the lower valve body 25, thereby cutting off the electrical connection between them. If the internal pressure continues to increase, the upper valve body 25 may rupture, allowing gas to be released from the opening 26a of the cap 26.

[0014] Next, the electrode assembly 14 will be described with reference to FIG. 2 . FIG. 2 is a perspective view of the electrode assembly 14. As described above, the electrode assembly 14 has a wound structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween. The positive electrode 11, the negative electrode 12, and the separator 13 are all formed in a strip shape and spirally wound around a winding core arranged along a winding axis 28, resulting in a state in which they are alternately stacked in the radial direction of the electrode assembly 14. In the radial direction, the side of the winding axis 28 is referred to as the inner side of the winding, and the opposite side is referred to as the outer side of the winding. In the electrode assembly 14, the longitudinal direction of the positive electrode 11 and the negative electrode 12 is the winding direction, and the short-side direction of the positive electrode 11 and the negative electrode 12 is the axial direction. The positive electrode lead 19 extends in the axial direction from approximately the center in the radial direction between the center and the outermost periphery at the upper end of the electrode assembly 14. The negative electrode lead 20 extends in the axial direction from the vicinity of the winding axis 28 at the lower end of the electrode body 14 .

[0015] A porous sheet having ion permeability and insulating properties is used for the separator 13. 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 an olefin resin such as polyethylene or polypropylene. The thickness of the separator 13 is, for example, 10 μm to 50 μm.

[0016] Next, the positive electrode 11 and the negative electrode 12 of the secondary battery 10 will be described in detail with reference to FIGS. 3 to 6. An example in which the positive electrode 11 is the first electrode and the negative electrode 12 is the second electrode will be described below. Note that the present embodiment is not limited to this example. For example, the negative electrode 12 may be the first electrode. Alternatively, the second electrode may have the same characteristics as the first electrode, and both the positive electrode 11 and the negative electrode 12 may have the characteristics of the first electrode.

[0017] 3 is a front view showing the positive electrode and negative electrode constituting an electrode assembly according to an embodiment in a developed state. As shown in FIG. 3, the negative electrode 12 is generally formed to be slightly larger than the positive electrode 11 in order to prevent lithium precipitation. That is, the negative electrode 12 is formed to be longer than the positive electrode 11 in both the longitudinal and lateral directions.

[0018] The positive electrode 11 has a positive electrode current collector 30 and a positive electrode mixture layer 32 formed on the surface of the positive electrode current collector 30. The positive electrode current collector 30 can be a foil of a metal such as aluminum that is stable in the potential range of the positive electrode, or a film with such a metal disposed on the surface layer.

[0019] The positive electrode mixture layer 32 includes, for example, a positive electrode active material, a conductive agent, and a binder. The content of the positive electrode active material in the positive electrode mixture layer 32 is, for example, 85% by mass to 99% by mass with respect to the total mass of the positive electrode mixture layer. The positive electrode can be produced, for example, by applying a positive electrode mixture slurry including a positive electrode active material, a conductive agent, a binder, etc., to both surfaces of the positive electrode current collector 30, drying the coating, and then rolling the coating using a roller or the like. The positive electrode mixture layer 32 is preferably formed on both surfaces of the positive electrode current collector 30.

[0020] The positive electrode active material contained in the positive electrode mixture layer 32 can be, for example, a lithium transition metal composite oxide containing a transition metal element such as Co, Mn, or Ni. ｘ CoO ２ , Li ｘ NiO ２ , Li ｘ MnO ２ , Li ｘ Co ｙ Ni １－ｙ O ２ , Li ｘ Co ｙM 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 (M is at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B, and 0<x≦1.2, 0<y≦0.9, and 2.0≦z≦2.3). These may be used alone or in combination.

[0021] The positive electrode active material preferably contains a lithium nickel composite oxide, since this can increase the capacity of the secondary battery 10. The lithium nickel composite oxide is preferably Li ｘ NiO ２ , Li ｘ Co ｙ Ni １－ｙ O ２ , Li ｘ Ni １－ｙ M ｙ O ｚ (M is at least one 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) The higher the Ni content of the lithium nickel composite oxide, the higher the capacity.

[0022] Examples of the conductive agent contained in the positive electrode mixture layer 32 include carbon black such as acetylene black and ketjen black, graphite, carbon nanotubes (CNT), carbon nanofibers, graphene, metal fibers, metal powder, conductive whiskers, etc. These may be used alone or in combination of two or more.

[0023] Examples of the binder contained in the positive electrode mixture layer 32 include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide-based resins, acrylic-based resins, polyolefin-based resins, etc. These may be used alone or in combination of two or more.

[0024] A pair of positive electrode current collector exposed portions 34, where the positive electrode current collector 30 is exposed, are formed on both sides of the positive electrode 11 so as to overlap each other in the thickness direction of the positive electrode 11. A positive electrode lead 19 is connected to the positive electrode current collector exposed portion 34 on the inner side of the winding. The positive electrode current collector exposed portion 34 is provided, for example, by intermittent application in which the positive electrode mixture slurry is not applied to a part of the positive electrode current collector 30. A plurality of positive electrode current collector exposed portions 34 may be formed so as to be aligned in the longitudinal direction of the positive electrode 11.

[0025] 3 , the positive electrode current collector exposed portion 34 is in contact with only one end 11 a of both ends in the lateral direction of the positive electrode 11, and does not extend to the other end 11 b in the lateral direction of the positive electrode 11. As a result, the positive electrode mixture layer 32 is present between the other end 11 b in the lateral direction of the positive electrode 11 and the positive electrode current collector exposed portion 34, and the battery capacity of the secondary battery 10 is increased.

[0026] A pair of protective tapes 36 covering the positive electrode current collector exposed portion 34 are arranged on both sides of the positive electrode 11 so as to overlap each other in the thickness direction of the positive electrode 11. In the example shown in Fig. 3 , the entire surface of the positive electrode current collector exposed portion 34, the positive electrode lead 19, and a portion of the positive electrode mixture layer 32 adjacent to the positive electrode current collector exposed portion 34 are covered with the protective tape 36. The protective tape 36 is an insulating member that prevents the positive electrode lead 19 and the positive electrode current collector exposed portion 34 from short-circuiting with the opposing negative electrode mixture layer if the separator 13 is torn.

[0027] The pair of protective tapes 36 include protruding portions 37 that protrude from the positive electrode current collector 30 in the short-side direction of the positive electrode 11, and are bonded to each other at the protruding portions 37. This allows the pair of protective tapes 36 to be arranged so as to overlap each other in the thickness direction of the positive electrode 11 when the positive electrode 11 and the negative electrode 12 are wound together to produce the electrode body 14. Furthermore, because the adhesive layer of the pair of protective tapes 36 is not present on the surface of the positive electrode mixture layer 32, peeling and cracking can be suppressed.

[0028] The negative electrode 12 has a negative electrode current collector 40 and a negative electrode mixture layer 42 formed on the surface of the negative electrode current collector 40. The negative electrode current collector 40 can be a foil of a metal such as copper that is stable in the potential range of the negative electrode, or a film with such a metal disposed on the surface layer.

[0029] The anode mixture layer 42 includes, for example, an anode active material and a binder. The content of the anode active material in the anode mixture layer 42 is, for example, 80% by mass to 99% by mass with respect to the total mass of the anode mixture layer 42. The anode 12 can be produced, for example, by applying an anode mixture slurry containing the anode active material, the binder, and the like to the surface of the anode current collector 40, drying the coating, and then rolling the coating using a roller or the like. The anode mixture layer 42 is preferably formed on both sides of the anode current collector 40.

[0030] The negative electrode active material contained in the negative electrode mixture layer 42 is not particularly limited as long as it can reversibly absorb and release lithium ions, and generally, a carbon material such as graphite is used. The graphite may be any of natural graphite such as flake graphite, lump graphite, and amorphous graphite, and artificial graphite such as lump artificial graphite and graphitized mesophase carbon microbeads.

[0031] As the negative electrode active material, metals that can be alloyed with Li, such as Si and Sn, metal compounds containing Si, Sn, etc., and lithium-titanium composite oxides 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 particles of Si 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 graphite.

[0032] Examples of the binder contained in the negative electrode mixture layer 42 include styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), carboxymethyl cellulose (CMC) or a salt thereof, polyacrylic acid (PAA) or a salt thereof (PAA-Na, PAA-K, etc., or a partially neutralized salt), polyvinyl alcohol (PVA), etc. These may be used alone or in combination of two or more.

[0033] An anode exposed portion 44, where the anode current collector 40 is exposed, is formed on the surface of the anode 12, and the anode lead 20 is connected to the anode exposed portion 44. The anode exposed portion 44 is provided, for example, by intermittent application in which the anode mixture slurry is not applied to a part of the anode current collector 40. In the example shown in Fig. 3, the anode 12 has the anode exposed portion 44 at an inner end portion in the longitudinal direction.

[0034] Fig. 4 is a cross-sectional view taken along line A-A in Fig. 3. Positive electrode mixture layers 32 are formed on both sides of the positive electrode current collector 30, and positive electrode current collector exposed portions 34 are formed on both sides of the positive electrode 11 so as to face each other with the positive electrode current collector 30 interposed therebetween. In the example shown in Fig. 4, the positive electrode lead 19 is connected to the surface of the positive electrode current collector 30 on the inner side of the winding. Protective tape 36 is arranged on both the inner and outer sides of the winding of the positive electrode 11 so as to cover the positive electrode current collector exposed portions 34. The positive electrode lead 19 may also be connected to the surface of the positive electrode current collector 30 on the outer side of the winding.

[0035] The protective tape 36 includes a substrate layer 38. The substrate layer 38 may be made of any insulating resin, such as polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyimide (PI), polypropylene (PP), polyethylene terephthalate (PET), or polybutylene terephthalate (PBT). Among these, PI, which has a relatively high hardness, is preferred from the viewpoint of protecting the exposed positive electrode current collector portion 34. The thickness of the substrate layer 38 is, for example, 5 μm or more and 50 μm or less. Although not shown in FIG. 4 , as described below, the protective tape 36 further includes an adhesive layer 39 formed on one surface of the substrate layer 38. A heat-resistant layer containing inorganic particles such as metal oxide may be provided between the substrate layer 38 and the adhesive layer 39.

[0036] Fig. 5 is an enlarged view of the periphery of the positive electrode current collector exposed portion 34 in Fig. 3. Each of the pair of protective tapes 36 has an adhesive layer 39 formed on the protruding portion 37 along the longitudinal direction of the positive electrode 11. In the example shown in Fig. 5, the adhesive layer 39 is formed on the end portion of the protruding portion 37 in the shorter direction of the positive electrode 11. The pair of protective tapes 36 are bonded to each other by the adhesive layer 39.

[0037] The pair of protective tapes 36 are adhered to the positive electrode lead 19 at the protruding portions 37 by the adhesive layer 39. This fixes the pair of protective tapes 36 to the positive electrode 11, and the pair of protective tapes 36 can be disposed at predetermined positions on the positive electrode 11 when the electrode body 14 is produced.

[0038] 5, the adhesive layer 39 is formed continuously between both ends of the protective tape 36, but the aspect of the adhesive layer 39 according to this embodiment is not limited to this example. The adhesive layer 39 is preferably longer than at least the positive electrode current collector exposed portion 34 in the longitudinal direction of the positive electrode 11. This makes it possible to suppress the occurrence of a short circuit due to the intrusion of foreign matter into the electrode body 14. Alternatively, the adhesive layer 39 may be formed intermittently along the longitudinal direction of the positive electrode 11.

[0039] The thickness of the adhesive layer 39 is, for example, 1 μm or more and 30 μm or less. The adhesive layer 39 may contain at least one of a rubber-based polymer and an acrylic-based polymer. The rubber-based polymer and the acrylic-based polymer have adhesive properties, and therefore can bond the protective tapes 36 together. The adhesive layer 39 may further contain, for example, a silicone-based polymer.

[0040] The width W1 of the adhesive layer 39 in the short-side direction of the positive electrode 11 is, for example, 0.5 mm≦W1≦5 mm, and preferably 1 mm≦W1≦2 mm. This allows the pair of protective tapes 36 to be more reliably bonded to each other. Furthermore, the width W2 of the protrusion 37 in the short-side direction of the positive electrode 11 is, for example, 0.5 mm≦W2≦5 mm, and preferably 1 mm≦W2≦2 mm. The width W1 and the width W2 may satisfy the relationship 0.5≦W1 / W2≦1.

[0041] The ratio L2 / L1 of the length L2 of the positive electrode current collector exposed portion 34 in the short-side direction of the positive electrode 11 to the total length L1 of the positive electrode 11 in the short-side direction is, for example, 5% to 50%.

[0042] Next, an embodiment different from the examples shown in Figures 3 to 5 will be described with reference to Figure 6. Figure 6 is an enlarged view of the periphery of a positive electrode current collector exposed portion 34 in another example of the embodiment. In the example shown in Figure 6, the positive electrode current collector exposed portion 34 extends from one end 11a to the other end 11b in the lateral direction of the positive electrode 11, and the positive electrode current collector exposed portion 34 contacts both ends of the positive electrode 11 in the lateral direction.

[0043] In the example shown in Fig. 6, similarly to Fig. 5, it is preferable that an adhesive layer 39 be formed on the protrusion 37 on the one end 11a side. This provides the same effect as the example shown in Fig. 5. It is also more preferable that an adhesive layer 39 be formed on the protrusion 37 on the other end 11b side, similarly to the protrusion 37 on the one end 11a side. This makes it possible to prevent short circuits from occurring due to the intrusion of foreign matter into the electrode body 14.

[0044] 6, as in the example shown in Fig. 5, the width W1 of the adhesive layer 39 in the short-side direction of the positive electrode 11 is, for example, 0.5 mm ≦ W1 ≦ 5 mm, and preferably 1 mm ≦ W1 ≦ 2 mm. The width W2 of the protrusion 37 in the short-side direction of the positive electrode 11 is, for example, 0.5 mm ≦ W2 ≦ 5 mm, and preferably 1 mm ≦ W2 ≦ 2 mm. The width W1 and the width W2 may satisfy the relationship 0.5 ≦ W1 / W2 ≦ 1.

[0045] As described above, the nonaqueous electrolyte secondary battery of the present disclosure can suppress peeling and cracking in the positive electrode mixture layer originating near the end of the adhesive layer of the protective tape, thereby reducing the risk of short circuiting.

[0046] The present disclosure is further described by the following embodiments. Aspect 1: A non-aqueous electrolyte secondary battery including an electrode assembly in which strip-shaped first and second electrodes having opposite polarities are wound longitudinally with a separator interposed therebetween, and an exterior housing that houses the electrode assembly, wherein the first electrode has a current collector and a mixture layer formed on the surface of the current collector, a pair of current collector exposed portions where the current collector is exposed is formed on both sides of the first electrode so as to overlap each other in the thickness direction of the first electrode, and a pair of protective tapes covering the current collector exposed portions is disposed so as to overlap each other in the thickness direction of the first electrode, the pair of protective tapes including protrusions protruding from the current collector in the short direction of the first electrode and bonded to each other at the protrusions. Aspect 2: The non-aqueous electrolyte secondary battery according to Aspect 1, wherein leads are connected to the current collector exposed portions, and the pair of protective tapes are bonded to the leads at the protrusions. Configuration 3: The nonaqueous electrolyte secondary battery according to Configuration 1 or 2, wherein the current collector exposed portion contacts only one of both ends in the short side direction of the first electrode.Configuration 4: The nonaqueous electrolyte secondary battery according to Configuration 1 or 2, wherein the current collector exposed portion contacts both ends in the short side direction of the first electrode.Configuration 5: The nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 4, wherein each of the pair of protective tapes has a base layer and an adhesive layer formed on a surface of the base layer, the adhesive layer is formed on the protruding portion along the longitudinal direction of the first electrode, and a width W1 of the adhesive layer in the short side direction of the first electrode is 0.5 mm≦W1≦5 mm.Configuration 6: The nonaqueous electrolyte secondary battery according to Configuration 5, wherein a width W2 of the protruding portion in the short side direction of the first electrode is 0.5 mm≦W2≦5 mm, and W1 and W2 satisfy the relationship 0.5≦W1 / W2≦1. Configuration 7: The nonaqueous electrolyte secondary battery according to any one of configurations 1 to 6, wherein the first electrode is a positive electrode.

[0047] REFERENCE SIGNS LIST 10 secondary battery, 11 positive electrode, 11a one end, 11b other end, 12 negative electrode, 13 separator, 14 electrode body, 15 outer casing, 16 sealing body, 17, 18 insulating plate, 19 positive electrode lead, 20 negative electrode lead, 21 grooved portion, 22 filter, 23 lower valve body, 24 insulating member, 25 upper valve body, 26 cap, 26a opening, 27 gasket, 28 winding shaft, 30 positive electrode current collector, 32 positive electrode mixture layer, 34 positive electrode current collector exposed portion, 36 protective tape, 37 protrusion, 38 substrate layer, 39 adhesive layer, 40 negative electrode current collector, 42 negative electrode mixture layer, 44 negative electrode exposed portion,

Claims

1. A non-aqueous electrolyte secondary battery comprising an electrode assembly in which strip-shaped first and second electrodes having opposite polarities are wound longitudinally with a separator interposed therebetween, and an exterior housing that houses the electrode assembly, wherein the first electrode has a current collector and a mixture layer formed on the surface of the current collector, a pair of current collector exposed portions where the current collector is exposed is formed on both sides of the first electrode so as to overlap each other in the thickness direction of the first electrode, and a pair of protective tapes covering the current collector exposed portions is arranged so as to overlap each other in the thickness direction of the first electrode, and the pair of protective tapes include protrusions that protrude from the current collector in the short direction of the first electrode, and are bonded to each other at the protrusions.

2. The nonaqueous electrolyte secondary battery according to claim 1, wherein leads are connected to the exposed current collector portions, and the pair of protective tapes are bonded to the leads at the protruding portions.

3. The nonaqueous electrolyte secondary battery according to claim 1, wherein the current collector exposed portion is in contact with only one of both ends in the short side direction of the first electrode.

4. The nonaqueous electrolyte secondary battery according to claim 1, wherein the exposed current collector portion contacts both ends of the first electrode in the short direction.

5. The nonaqueous electrolyte secondary battery according to claim 1, wherein the protective tape has a base layer and an adhesive layer formed on the surface of the base layer, the adhesive layer is formed on the protruding portion along the longitudinal direction of the first electrode, and a width W1 of the adhesive layer in the lateral direction of the first electrode is 0.5 mm≦W1≦5 mm.

6. The nonaqueous electrolyte secondary battery according to claim 5, wherein the width W2 of the protrusion in the short-side direction of the first electrode is 0.5 mm≦W2≦5 mm, and W1 and W2 satisfy the relationship 0.5≦W1 / W2≦1.

7. The nonaqueous electrolyte secondary battery according to claim 1, wherein the first electrode is a positive electrode.

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