Nonaqueous electrolyte secondary battery

Abstract

Provided is a nonaqueous electrolyte secondary battery which has a reduced risk of a short circuit. A nonaqueous electrolyte secondary battery according to one embodiment of the present disclosure comprises: an electrode body in which a first electrode and a second electrode, which are strip-shaped and have mutually different polarities, are wound in a longitudinal direction; and an exterior body. On the surfaces of the inside and the outside of the winding of the first electrode, collector exposed parts in which a current collector is exposed are formed in a position overlapping the first electrode in the thickness direction thereof. A first protective tape is disposed on the inside of the winding of the first electrode so as to cover the collector exposed part, and a second protective tape is disposed on the outside of the winding of the first electrode so as to cover the collector exposed part. The first protective tape has a base material layer and an adhesive layer formed on the surface of the base material layer, and the second protective tape has a base material layer but does not have an adhesive layer. The first protective tape and the second protective tape include protruding parts protruding from the current collector in the lateral direction of the first electrode and are bonded to each in the protruding parts.

Description

Non-aqueous 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 cracking in the mixture layer, originating from the edge of the adhesive layer of the protective tape, which can lead to a short circuit. The inventors also discovered that the mixture layer formed on the outer side of the current collector is more susceptible to peeling or cracking due to the tensile stress it receives compared to the mixture layer formed on the inner side of the current collector. The technology disclosed in Patent Document 1 does not address 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 first protective tape disposed on the inner surface of the first electrode so as to cover the current collector exposed portion; and a second protective tape disposed on the outer surface of the first electrode so as to cover the current collector exposed portion, the second protective tape having a base layer and no adhesive layer, the first protective tape having a base layer but no adhesive layer, the first protective tape and the second protective tape including a protrusion protruding from the current collector in the widthwise direction of the first electrode and being bonded to each other by the protrusion.

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

[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 ３ etc., 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 11 and the negative electrode 12 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 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 (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] On the inner and outer surfaces of the positive electrode 11, a positive electrode current collector exposed portion 34 where the positive electrode current collector 30 is exposed is formed at a position where the exposed portions overlap each other in the thickness direction of the positive electrode 11. FIG. 3 shows the inner surfaces of the positive electrode 11 and the negative electrode 12, and a positive electrode lead 19 is connected to the inner positive electrode current collector exposed portion 34. The positive electrode current collector exposed portion 34 is formed, 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 and 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 11a of both ends in the lateral direction of the positive electrode 11, and does not extend to the other end 11b in the lateral direction of the positive electrode 11. As a result, the positive electrode mixture layer 32 is present between the other end 11b 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 first protective tape 35 is disposed on the wound inner side of the positive electrode 11 so as to cover the positive electrode current collector exposed portion 34. 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 first protective tape 35. On the wound outer side of the positive electrode 11 (not shown in FIG. 3 ), a second protective tape 36 is disposed at a position overlapping the first protective tape 35 in the thickness direction of the positive electrode 11 so as to cover the positive electrode current collector exposed portion 34. The first protective tape 35 and the second protective tape 36 are insulating members that prevent 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 first protective tape 35 and the second protective tape 36 include protruding portions 37 that protrude from the positive electrode current collector 30 in the short-side direction of the positive electrode 11. The first protective tape 35 and the second protective tape 36 are bonded to each other at the protruding portions 37 by an adhesive layer 39 of the first protective tape 35, which will be described later. This allows the first protective tape 35 and the second protective tape 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.

[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.

[0035] The first protective tape 35 arranged on the inside of the wound cathode 11 has a base material layer 38a and an adhesive layer 39 formed on the surface of the base material layer 38a, while the second protective tape 36 arranged on the outside of the wound cathode 11 has a base material layer 38b but no adhesive layer. As a result, no end of the adhesive layer is present on the surface of the positive electrode mixture layer 32 on the outside of the wound cathode 11, and peeling and cracking can be suppressed on the outside of the wound cathode 11 where tensile stress is applied. Furthermore, at the protruding portion 37, the first protective tape 35 and the second protective tape 36 are adhered to each other by the adhesive layer 39 of the first protective tape 35.

[0036] The first protective tape 35 is adhered to the surface of the positive electrode mixture layer 32 by an adhesive layer 39. As a result, the first protective tape 35 and the second protective tape 36, which is adhered to the first protective tape 35 at the protruding portion 37, are fixed to the positive electrode 11 and are disposed at a predetermined position on the positive electrode 11 when the electrode body 14 is produced. Note that, because a compressive stress is applied to the inside of the wound positive electrode 11, there is little possibility that peeling or cracks will occur due to the end of the adhesive layer present on the inside of the wound positive electrode 11.

[0037] The base layers 38a, 38b may be made of any insulating resin, such as PPS (polyphenylene sulfide), PEEK (polyether ether ketone), PI (polyimide), PP (polypropylene), PET (polyethylene terephthalate), or PBT (polybutylene terephthalate). Among these, PI, which has a relatively high hardness, is preferred from the viewpoint of protecting the positive electrode current collector exposed portion 34. The thickness of the base layers 38a, 38b is, for example, 5 μm or more and 50 μm or less. In this embodiment, the base layers 38a, 38b are made of the same material and have the same thickness, but may be made of different materials and have different thicknesses.

[0038] The adhesive layer 39 is a portion for adhering the first protective tape 35 to the positive electrode 11. The adhesive layer 39 is formed, for example, on the entire outer surface of the base material layer 38a. 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 adhere the first protective tape 35 to the surface of the positive electrode 11. The adhesive layer 39 may further contain, for example, a silicone-based polymer. In the first protective tape 35, a heat-resistant layer containing inorganic particles such as metal oxide may be provided between the base material layer 38a and the adhesive layer 39.

[0039] 4 , the positive electrode lead 19 is connected to the surface of the positive electrode current collector 30 on the inner side of the wound state. The first protective tape 35 is bonded to the positive electrode lead 19 at a protruding portion 37. 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 wound state.

[0040] 5 is an enlarged view of the periphery of the positive electrode current collector exposed portion 34 in FIG. 3. The width W of the protrusion 37 in the short-side direction of the positive electrode 11 is, for example, 0.5 mm≦W≦5 mm. 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%.

[0041] Next, with reference to Fig. 6, an embodiment different from the examples shown in Fig. 3 to Fig. 5 will be described. Fig. 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 Fig. 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.

[0042] In the example shown in Fig. 6, the first protective tape 35 and the second protective tape 36 protrude from both ends 11a, 11b of the positive electrode current collector 30 and include two protrusions 37. This provides the same effect as the example shown in Fig. 5. Note that the first protective tape 35 and the second protective tape 36 may protrude from only one end of the positive electrode current collector 30, and it is preferable that the first protective tape 35 and the second protective tape 36 protrude from one end 11a of the positive electrode current collector 30.

[0043] In the example shown in FIG. 6, similarly to the example shown in FIG. 5, the width W of the protrusion 37 in the short-side direction of the positive electrode 11 is, for example, 0.5 mm≦W≦5 mm.

[0044] 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.

[0045] The present disclosure will be further described by the following embodiments. Configuration 1: A nonaqueous electrolyte secondary battery including an electrode assembly in which strip-shaped first and second electrodes having opposite polarities are wound in the longitudinal direction 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, current collector exposed portions where the current collector is exposed are formed on the inner and outer surfaces of the first electrode at positions overlapping the first electrode in the thickness direction, a first protective tape is disposed on the inner surface of the first electrode so as to cover the current collector exposed portion, and a second protective tape is disposed on the outer surface of the first electrode so as to cover the current collector exposed portion at a position overlapping the first protective tape in the thickness direction of the first electrode, the first protective tape has a base layer and an adhesive layer formed on the surface of the base layer, and the second protective tape has the base layer but does not have an adhesive layer, A nonaqueous electrolyte secondary battery, wherein the first protective tape and the second protective tape include protruding portions protruding from the current collector in the widthwise direction of the first electrode, and are bonded to each other at the protruding portions. Structure 2: The nonaqueous electrolyte secondary battery according to Structure 1, wherein a lead is connected to the current collector exposed portion, and the first protective tape is bonded to the lead at the protruding portion. Structure 3: The nonaqueous electrolyte secondary battery according to Structures 1 or 2, wherein the current collector exposed portion contacts only one of both ends in the widthwise direction of the first electrode. Structure 4: The nonaqueous electrolyte secondary battery according to any one of Structures 1 to 3, wherein the current collector exposed portion contacts both ends in the widthwise direction of the first electrode. Structure 5: The nonaqueous electrolyte secondary battery according to any one of Structures 1 to 4, wherein the width of the protruding portion in the widthwise direction of the first electrode is 0.5 mm or more and 5 mm or less. Structure 6: The nonaqueous electrolyte secondary battery according to any one of Structures 1 to 5, wherein the first electrode is a positive electrode.

[0046] 10 Secondary battery, 11 Positive electrode, 11a One end, 11b Other end, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Exterior body, 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, 35 First protective tape, 36 Second protective tape, 37 Protrusion, 38a, 38b Base 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, and current collector exposed portions where the current collector is exposed are formed on the inner and outer surfaces of the first electrode at positions overlapping the thickness of the first electrode, a first protective tape is disposed on the inner surface of the first electrode so as to cover the current collector exposed portion, and a second protective tape is disposed on the outer surface of the first electrode so as to cover the current collector exposed portion at a position overlapping the first protective tape in the thickness of the first electrode, the first protective tape has a base layer and an adhesive layer formed on the surface of the base layer, and the second protective tape has the base layer but does not have the adhesive layer, the first protective tape and the second protective tape include protruding portions that protrude from the current collector in a short-side direction of the first electrode, and are bonded to each other at the protruding portions.

2. The nonaqueous electrolyte secondary battery according to claim 1, wherein a lead is connected to the exposed portion of the current collector, and the first protective tape is bonded to the lead at the protruding portion.

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 width of the protrusion in the short-side direction of the first electrode is 0.5 mm or more and 5 mm or less.

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

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