Non-aqueous electrolyte secondary battery

Abstract

Provided is a non-aqueous electrolyte secondary battery comprising an electrode body in which a belt-form positive electrode (11) and a belt-form negative electrode (12) are wound with a separator interposed therebetween, wherein the non-aqueous electrolyte secondary battery is characterized in that: the surface of the positive electrode (11) is provided with a positive electrode current collector exposed portion (34) where a positive electrode current collector is exposed; the positive electrode current collector exposed portion (34) is covered by a protective tape (50); the protective tape (50) has a facing region (51) that faces the negative electrode (12), and a non-facing region (52) that does not face the negative electrode (12); and the non-facing region (52) is provided with at least one or more notches (53) that extend from an upper end (50A) of the protective tape (50) toward a lower-end (50B) side of the protective tape (50).

Description

Nonaqueous electrolyte secondary battery

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

[0002] In recent years, non-aqueous electrolyte secondary batteries have become increasingly high-capacity and high-power. The increased capacity and high-power of batteries has led to an increase in the amount of heat generated when an internal short circuit occurs in the battery, creating a need to reduce the risk of an internal short circuit. A positive electrode exposed portion, where the surface of the positive electrode current collector is exposed, is formed on the surface of the positive electrode of the battery, and a positive electrode lead for current collection is connected to the positive electrode exposed portion. Patent Document 1 discloses a method for reducing the risk of an internal short circuit by covering the positive electrode lead with an insulating protective tape.

[0003] Japanese Patent Application Laid-Open No. 2003-132875

[0004] During the manufacturing process of a battery, an external load may be applied to the wound electrode assembly. For example, when the electrode assembly is pressed from above, a load may be applied to the protective tape, which may cause the protective tape to bend. When the protective tape is bent, a load may also be applied to the opposing negative electrode, which may damage the electrode plate.

[0005] A nonaqueous electrolyte secondary battery according to one aspect of the present disclosure is a nonaqueous electrolyte secondary battery including an electrode assembly in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator interposed therebetween, and a bottomed cylindrical outer can that houses the electrode assembly, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer provided on the surface of the positive electrode current collector, the surface of the positive electrode is provided with a positive electrode current collector exposed portion where the positive electrode current collector is exposed, the positive electrode current collector exposed portion is covered with a protective tape, and the protective tape has a facing region that faces the negative electrode and a non-facing region that does not face the negative electrode, and the non-facing region is provided with at least one notch or cutout extending from an upper end of the protective tape toward a lower end of the protective tape.

[0006] According to the nonaqueous electrolyte secondary battery of one aspect of the present disclosure, it is possible to suppress the occurrence of internal short circuits and to suppress damage to the electrode plates due to bending of the protective tape.

[0007] Fig. 1 is an axial cross-sectional view of a nonaqueous electrolyte secondary battery that is an example of an embodiment; Fig. 2 is a perspective view of an electrode body that constitutes a nonaqueous electrolyte secondary battery that is an example of an embodiment; Fig. 3 is a view showing a positive electrode and a negative electrode that constitute a nonaqueous electrolyte secondary battery that is an example of an embodiment in a developed state; Fig. 4 is a cross-sectional view of a positive electrode that constitutes a nonaqueous electrolyte secondary battery that is an example of an embodiment; Fig. 5 is a view showing a positive electrode and a negative electrode that constitute a nonaqueous electrolyte secondary battery that is another example of an embodiment in a developed state; Fig. 6 is a view showing a positive electrode and a negative electrode that constitute a nonaqueous electrolyte secondary battery that is another example of an embodiment in a developed state.

[0008] Hereinafter, an example of an embodiment of a cylindrical battery according to the present disclosure will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the present disclosure is not limited to the following embodiment. Furthermore, the present disclosure also includes configurations obtained by selectively combining the components of the embodiments described below.

[0009] The configuration of a nonaqueous electrolyte secondary battery 10 of this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a diagram schematically showing an axial cross section of the nonaqueous electrolyte secondary battery 10, and Figure 2 is a perspective view of an electrode assembly 14 that constitutes the nonaqueous electrolyte secondary battery 10.

[0010] 1 and 2 , the nonaqueous electrolyte secondary battery 10 includes an electrode assembly 14 in which a positive electrode 11 and a negative electrode 12 are wound with a separator 13 interposed therebetween, a nonaqueous electrolyte (not shown), an outer can 16 that houses the electrode assembly 14 and the nonaqueous electrolyte, and a sealing body 17 that closes the opening of the outer can 16. In this specification, the sealing body 17 side of the nonaqueous electrolyte secondary battery 10 is referred to as the "top" and the bottom 16A side of the outer can 16 is referred to as the "bottom."

[0011] The electrode assembly 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and has a 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 that constitute the electrode assembly 14 are all long, strip-like bodies that are spirally wound and alternately stacked in the radial direction of the electrode assembly 14. The negative electrode 12 protrudes downward beyond the positive electrode 11 and the separator 13. That is, the negative electrode 12 is formed to be longer in the longitudinal direction and width direction than the positive electrode 11. The separator 13 is formed to be slightly larger than the positive electrode 11, and, for example, two separators 13 are arranged to sandwich the positive electrode 11.

[0012] The electrode body 14 has a positive electrode lead 20 that is connected to the positive electrode current collector exposed portion 34 (see FIG. 3 ) of the positive electrode 11 by welding or the like. In this embodiment, the electrode body 14 has a plurality of positive electrode leads 20. The number of positive electrode leads 20 may be one. Furthermore, the electrode body 14 may have a negative electrode lead in addition to the positive electrode lead 20. The number of negative electrode leads may be one or more.

[0013] The positive electrode 11 has a positive electrode current collector 30 and a positive electrode mixture layer 32 formed on the positive electrode current collector 30. The positive electrode current collector 30 can be a foil of a metal such as aluminum or an aluminum alloy that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on the surface layer. A suitable positive electrode current collector 30 is a foil of a metal whose main component is aluminum or an aluminum alloy. The thickness of the positive electrode current collector 30 is, for example, 10 μm or more and 30 μm or less.

[0014] The positive electrode mixture layer 32 contains a positive electrode active material, a conductive agent, and a binder, and is preferably formed on both sides of the positive electrode current collector 30 except for the positive electrode current collector exposed portion 34 to which the positive electrode lead 20 is welded. As will be described in detail later, the positive electrode current collector exposed portion 34 is covered with a protective tape 50 (see FIG. 3 ). The positive electrode 11 can be produced, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, and the like onto the positive electrode current collector 30, drying the coating, and then compressing it to form the positive electrode mixture layer 32 on both sides of the positive electrode current collector 30.

[0015] The positive electrode mixture layer 32 contains particulate lithium metal composite oxide as a positive electrode active material. The lithium metal composite oxide is a composite oxide containing metal elements such as Co, Mn, Ni, and Al in addition to Li. The metal element constituting the lithium metal composite oxide is, for example, at least one selected from Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, and Bi. Among these, it is preferable to contain at least one selected from Co, Ni, and Mn. Examples of suitable composite oxides include lithium metal composite oxides containing Ni, Co, and Mn, or lithium metal composite oxides containing Ni, Co, and Al.

[0016] 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, and other carbon materials. Examples of the binder contained in the positive electrode mixture layer 32 include fluorine-containing resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resin, polyolefin, and the like. Furthermore, these resins may be used in combination with carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), and the like.

[0017] The negative electrode 12 has a negative electrode current collector 40 and a negative electrode mixture layer 42 formed on the negative electrode current collector 40. The negative electrode current collector 40 can be a foil of a metal, such as copper or a copper alloy, that is stable within the potential range of the negative electrode 12, or a film having such a metal disposed on its surface. The negative electrode mixture layer 42 contains a negative electrode active material, a binder, and, if necessary, a conductive agent, and is preferably formed on both sides of the negative electrode current collector 40 except for the negative electrode current collector exposed portion 44 described below. The negative electrode 12 can be produced by applying a negative electrode mixture slurry containing the negative electrode active material and the binder to the surface of the negative electrode current collector 40, drying the coating, and then compressing it to form the negative electrode mixture layer 42 on both sides of the negative electrode current collector 40.

[0018] The negative electrode mixture layer 42 generally contains, as the negative electrode active material, a carbon material that reversibly absorbs and releases lithium ions. Suitable examples of the carbon material include natural graphite, such as flake graphite, lump graphite, and amorphous graphite, and artificial graphite, such as massive artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB). Furthermore, the negative electrode active material may include a material containing at least one of an element that alloys with Li, such as Si or Sn, and a material containing such an element. Among these, a composite material containing Si is preferred.

[0019] A suitable example of a composite material containing Si is SiO ２ Examples of the composite material include a material in which Si fine particles are dispersed in a silicate phase such as lithium silicate, or a material in which Si fine particles are dispersed in an amorphous carbon phase. A conductive layer such as a carbon coating is formed on the particle surface of the composite material. The combined use of a carbon material and a Si-containing composite material as the negative electrode active material is preferred from the viewpoint of achieving both high capacity and high durability of the battery.

[0020] As in the case of the positive electrode mixture layer 32, the binder contained in the negative electrode mixture layer 42 can be a fluorine-containing resin, PAN, polyimide, acrylic resin, polyolefin, or the like, but preferably styrene-butadiene rubber (SBR) is used. The negative electrode mixture layer 42 preferably contains CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), or the like. Among these, it is preferable to use a combination of SBR with CMC or a salt thereof, PAA or a salt thereof, or the like. The negative electrode mixture layer 42 may contain a conductive agent such as CNT.

[0021] The negative electrode 12 has, at its lower axial end, a negative electrode current collector exposed portion 44 where the negative electrode mixture layer 42 is not provided and the negative electrode current collector 40 is exposed. The negative electrode current collector exposed portion 44 is provided over a range from the end at the winding start side to the end at the winding end side in the longitudinal direction of the negative electrode 12. Therefore, the lower axial end of the electrode body 14 is constituted by the negative electrode current collector exposed portion 44. The width (axial length) of the negative electrode current collector exposed portion 44 is, for example, 2 mm or more and 20 mm or less.

[0022] The separator 13 is a porous sheet having ion permeability and insulating properties. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Suitable materials for the separator 13 include polyolefins such as polyethylene and polypropylene, and cellulose. The separator 13 may have a single-layer structure or a multi-layer structure. A highly heat-resistant resin layer such as an aramid resin may be formed on the surface of the separator 13. A filler layer containing an inorganic filler may be formed at the interface between the separator 13 and at least one of the positive electrode 11 and the negative electrode 12.

[0023] The non-aqueous electrolyte has lithium ion conductivity and may be a liquid electrolyte (electrolytic solution) or a solid electrolyte.

[0024] The liquid electrolyte (electrolytic solution) contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and mixed solvents of two or more of these. Examples of the non-aqueous solvent include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents of these. The non-aqueous solvent may contain a halogen-substituted compound (e.g., fluoroethylene carbonate) in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine. Examples of the electrolyte salt include LiPF ６ Lithium salts such as

[0025] As the solid electrolyte, for example, a solid or gel-like polymer electrolyte, an inorganic solid electrolyte, etc. can be used. As the inorganic solid electrolyte, a material known in all-solid-state lithium ion secondary batteries, etc. (for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a halogen-based solid electrolyte, etc.) can be used. The polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt, and a matrix polymer. As the matrix polymer, for example, a polymer material that absorbs the non-aqueous solvent and gels is used. As the polymer material, for example, a fluororesin, an acrylic resin, a polyether resin, etc. can be used.

[0026] An insulating plate 18 is disposed on top of the electrode body 14. A positive electrode lead 20 passes through a through-hole 18A provided in the insulating plate 18 and extends toward the sealing body 17. The positive electrode lead 20 is bent so as to fit along the upper surface of an upper current collector plate 22 that constitutes the sealing body 17, and is joined to the upper surface of the upper current collector plate 22 by welding or the like. This makes the sealing body 17 a positive electrode terminal.

[0027] As described above, the negative electrode current collector exposed portion 44 is provided at the lower end of the electrode body 14. The negative electrode current collector exposed portion 44 is bent radially inward at the lower end and joined by welding or the like to the upper surface of the lower current collector plate 23 provided at the bottom of the electrode body 14. The lower current collector plate 23 is also joined to the inner surface of the bottom 16A of the outer can 16. This makes the outer can 16 a negative electrode terminal.

[0028] The outer can 16 is a cylindrical metal container with a bottom and an opening on one axial side. The opening of the outer can 16 is closed by a sealing body 17. A gasket 21 made of a resin material is provided between the outer can 16 and the sealing body 17. The provision of the gasket 21 ensures airtightness inside the battery and also ensures insulation between the outer can 16 and the sealing body 17. In other words, the gasket 21 serves as a sealing member to maintain airtightness inside the battery and as an insulating member to insulate the outer can 16 from the sealing body 17.

[0029] The outer can 16 has a grooved portion 16B formed in a side wall that protrudes inward and supports the sealing body 17. The grooved portion 16B is preferably formed in an annular shape along the circumferential direction of the outer can 16, and its upper surface supports the sealing body 17. The grooved portion 16B can be formed, for example, by spinning a portion of the side wall of the outer can 16 radially inward to recess it radially inward.

[0030] The sealing body 17 has a function of sealing the opening of the outer can 16. In this embodiment, the sealing body 17 is composed of an upper current collector plate 22 to which the positive electrode lead 20 is joined, and a sealing plate 24 that covers the upper current collector plate 22. The sealing body 17 is fixed to the opening of the outer can 16 by crimping via a gasket 21. Note that the configuration of the sealing body 17 is not limited to this, as long as it is capable of sealing the opening of the outer can 16.

[0031] The upper current collector plate 22 is an annular metal plate-like member having a through-hole in the center. The upper current collector plate 22 has a recessed portion on the lower side, to which the positive electrode lead 20 is joined. The outer periphery of the upper current collector plate 22 abuts against the outer periphery of the sealing plate 24. In addition, the outer periphery of the upper current collector plate 22 is preferably joined to the sealing plate 24 by laser welding or the like.

[0032] The sealing plate 24 is a metal plate-like member that does not have any through holes. A convex portion that protrudes toward the outside of the battery is provided in the center of the sealing plate 24. The convex portion has, for example, a substantially circular shape when viewed from above.

[0033] Next, the positive electrode 11 and the protective tape 50 provided on the positive electrode 11 will be described in detail with reference to Fig. 3 and Fig. 4. Fig. 3 is a diagram showing the positive electrode 11 and the negative electrode 12 in a developed state, and Fig. 4 is a cross-sectional view of the positive electrode 11.

[0034] 3 and 4 , the positive electrode 11 has a positive electrode current collector 30 and a positive electrode mixture layer 32 provided on the surface of the positive electrode current collector 30. From the viewpoint of preventing lithium deposition during charging, the positive electrode 11 is formed to have dimensions slightly smaller than the negative electrode 12. In other words, the positive electrode 11 is formed to be shorter than the negative electrode 12 in the longitudinal and width directions.

[0035] The positive electrode 11 has a surface on which the positive electrode mixture layer 32 is not provided, and instead has a positive electrode current collector exposed portion 34 where the positive electrode current collector 30 is exposed. The positive electrode current collector exposed portion 34 is provided, for example, on both surfaces of the positive electrode 11. In this embodiment, the positive electrode lead 20 is joined by welding or the like to the surface of the positive electrode current collector exposed portion 34 provided on the inner periphery of the positive electrode 11. The positive electrode lead 20 may also be joined to the surface of the positive electrode current collector exposed portion 34 provided on the outer periphery of the positive electrode 11.

[0036] As described above, a plurality of positive electrode leads 20 are joined to the positive electrode 11. Therefore, a plurality of positive electrode current collector exposed portions 34 are provided on the surface of the positive electrode 11. Note that a positive electrode current collector exposed portion 34 to which no positive electrode lead 20 is joined may also be provided on the surface of the positive electrode 11. In other words, a greater number of positive electrode current collector exposed portions 34 than the number of positive electrode leads 20 may be provided on the surface of the positive electrode 11.

[0037] The positive electrode current collector exposed portion 34 is provided at the upper end 11A of the positive electrode 11. In other words, the positive electrode current collector exposed portion 34 is in contact only with the upper end 11A of the positive electrode 11 and does not extend to the lower end 11B of the positive electrode 11. This allows the positive electrode mixture layer 32 to be present between the positive electrode current collector exposed portion 34 and the lower end 11B of the positive electrode 11. As a result, the battery capacity of the nonaqueous electrolyte secondary battery 10 can be improved. The positive electrode current collector exposed portion 34 may be provided across the width direction of the positive electrode 11.

[0038] The shape and size of the positive electrode current collector exposed portion 34 can be set appropriately depending on the shape, size, etc. of the positive electrode lead 20. The positive electrode current collector exposed portion 34 has, for example, a rectangular shape. The length of the positive electrode current collector exposed portion 34 along the longitudinal direction of the positive electrode 11 is, for example, 5 mm or more and 50 mm or less. 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.

[0039] One end of the positive electrode lead 20 is connected to the positive electrode current collector exposed portion 34, and the other end extends upward in the width direction of the positive electrode 11 and is joined to the upper current collector plate 22 (see FIG. 1 ). One end of the positive electrode lead 20 can be joined to the positive electrode current collector exposed portion 34 by, for example, ultrasonic welding. The material of the positive electrode lead 20 is not particularly limited as long as it is conductive, but it is preferably made of a metal containing aluminum as a main component.

[0040] A protective tape 50 is attached to the surface of the positive electrode 11 to cover the positive electrode current collector exposed portion 34. The protective tape 50 covers the entire positive electrode current collector exposed portion 34, a part of the positive electrode lead 20, and the positive electrode mixture layer 32 around the positive electrode current collector exposed portion 34. By providing the protective tape 50, if the separator 13 is damaged, contact between the positive electrode current collector exposed portion 34 and the positive electrode lead 20 and the opposing negative electrode 12 can be suppressed. As a result, an internal short circuit can be suppressed.

[0041] The protective tape 50 has an upper end 50A located above an upper end 12A of the negative electrode 12. That is, the protective tape 50 has a facing region 51 facing the negative electrode 12 and a non-facing region 52 located above the facing region 51 and not facing the negative electrode 12. In this embodiment, the upper end 50A of the protective tape 50 is located above the upper end of the separator 13 (see FIG. 2 ).

[0042] The protective tape 50 is an adhesive tape having a substrate and an adhesive portion formed on one surface of the substrate. A heat-resistant layer containing inorganic particles such as metal oxide can be provided between the substrate and the adhesive portion. The substrate can 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). The thickness of the substrate is, for example, 5 μm or more and 50 μm or less, and preferably 10 μm or more and 30 μm or less.

[0043] The adhesive portion is a portion for adhering the protective tape 50 to the surface of the positive electrode 11. The thickness of the adhesive portion is, for example, 1 μm or more and 30 μm or less, and preferably 5 μm or more and 25 μm or less. The adhesive portion 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 protective tape 50 to the surface of the positive electrode 11. The adhesive portion may further contain, for example, a silicone-based polymer.

[0044] As shown in FIG. 3 , the non-facing region 52 of the protective tape 50 is provided with at least one notch 53 extending from the upper end 50A of the protective tape 50 toward the lower end 50B of the protective tape 50. By providing the notch 53 in the protective tape 50, the upper end 50A of the protective tape 50 can be made flexible. As a result, unintended bending of the protective tape 50 is suppressed when a load is applied from above the protective tape 50. If the protective tape 50 is bent due to a load from above, the bent portion may come into contact with the opposing negative electrode 12, causing damage such as breakage of the negative electrode 12. In other words, by covering the positive electrode current collector exposed portion 34 with the protective tape 50 having the notch 53 at the upper end 50A, it is possible to suppress the occurrence of an internal short circuit while suppressing damage to the negative electrode 12 due to bending of the protective tape 50.

[0045] In this embodiment, the protective tape 50 is provided with ten notches 53 extending along the width direction of the positive electrode 11 (the axial direction of the outer can 16). The notches 53 are provided at positions that do not face the positive electrode lead 20. This prevents the positive electrode lead 20 from coming into contact with the negative electrode 12 and causing an internal short circuit. The number and arrangement of the notches 53 can be set appropriately depending on the sizes of the protective tape 50 and the positive electrode lead 20, etc.

[0046] It is preferable that at least some of the notches 53 are provided at approximately equal intervals in the longitudinal direction of the positive electrode 11. In this case, it is easy to impart flexibility to the upper end 50A of the protective tape 50. In this embodiment, the notches 53 are provided at approximately equal intervals except for the region facing the positive electrode lead 20. The interval between adjacent notches 53 in the longitudinal direction of the positive electrode 11 can be set appropriately depending on the size of the protective tape 50, etc., and is, for example, 0.5 mm or more and 10 mm or less.

[0047] In the width direction of the positive electrode 11, the length of the notch 53 is preferably 50% or more, and more preferably 75% or more, of the length of the non-facing region 52. In other words, the notch 53 may terminate halfway through the non-facing region 52. By setting the length of the notch 53 to 50% or more of the length of the non-facing region 52, it becomes easy to impart flexibility to the upper end 50A of the protective tape 50. The length of the non-facing region 52 in the width direction of the positive electrode 11 can be set appropriately depending on the battery performance, etc., and is, for example, 0.1 mm or more and 3.0 mm or less.

[0048] The notch 53 may extend beyond the non-facing region 52 into the facing region 51. On the other hand, from the viewpoint of suppressing internal short circuits, it is preferable that the notch 53 does not face the positive electrode 11. The upper limit of the length of the notch 53 is, for example, preferably 150% or less of the length of the non-facing region 52. Therefore, in the width direction of the positive electrode 11, the length of the notch 53 is preferably 50% or more and 150% or less of the length of the non-facing region 52, and more preferably 75% or more and 150% or less.

[0049] In the longitudinal direction of the positive electrode 11, the ratio (L50 / L20) of the length (L20) of the positive electrode lead 20 to the length (L50) of the protective tape 50 is preferably 2.0 or more and 10.0 or less, and more preferably 3.0 or more and 8.0 or less. In this case, internal short circuits can be further suppressed.

[0050] The notches 53 can be formed, for example, by adhering the protective tape 50 to the surface of the positive electrode 11 and then cutting the protective tape 50 from above with a blade or the like. Alternatively, the protective tape 50 on which the notches 53 have been formed in advance may be adhered to the surface of the positive electrode 11.

[0051] As described above, by providing the notch 53 at the upper end 50A of the protective tape 50, the upper end 50A of the protective tape 50 can be made flexible, and unintended bending of the protective tape 50 can be suppressed when a load is applied to the protective tape 50. As a result, damage to the negative electrode 12 due to bending of the protective tape 50 can be suppressed. In other words, by covering the positive electrode current collector exposed portion 34 with the protective tape 50, it is possible to suppress the occurrence of an internal short circuit and also to suppress damage to the negative electrode 12 due to bending of the protective tape 50.

[0052] The above embodiment can be modified as appropriate without impairing the object of the present disclosure. For example, in the above embodiment, the notch 53 extends along the width direction of the positive electrode 11, but this is not limited thereto. For example, the notch 53 may extend along a direction inclined with respect to the width direction of the positive electrode 11. The inclination angle of the extension direction of the notch 53 with respect to the width direction of the positive electrode 11 is, for example, 0° or more and 45° or less.

[0053] In the above embodiment, the length of all the notches 53 in the width direction of the positive electrode 11 is the same, but the lengths of the notches 53 may be different from one another. For example, the notches 53 may be longer as they are farther from the positive electrode lead 20.

[0054] Furthermore, in the above embodiment, the notches 53 are provided in the non-facing region 52 of the protective tape 50, but notches may be provided instead of or in addition to the notches 53. For example, as shown in FIG. 5 , a plurality of rectangular notches 54 may be provided in the non-facing region 52 of the protective tape 50. By providing the notches 54 in the protective tape 50, the upper end 50A of the protective tape 50 can be made flexible. The width of the notches 54 (the length along the longitudinal direction of the positive electrode 11) is, for example, 0.05 mm or more and 3.0 mm or less. The size, arrangement, etc. of the notches 54 can be adapted to the size, arrangement, etc. of the notches 53 described above.

[0055] 6 , the notch 54 may be provided in substantially the entire non-facing region 52 except for the region facing the positive electrode lead 20. That is, the protective tape 50 may have a facing region 51 facing the negative electrode 12 and a protruding region 55 that protrudes upward from the facing region 51 and faces the positive electrode lead 20.

[0056] The present disclosure is further described by the following embodiments. Aspect 1: A nonaqueous electrolyte secondary battery including an electrode assembly in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator interposed therebetween, and a bottomed cylindrical outer can housing the electrode assembly, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer provided on the surface of the positive electrode current collector, the surface of the positive electrode is provided with a positive electrode current collector exposed portion where the positive electrode current collector is exposed, the positive electrode current collector exposed portion is covered with a protective tape, the protective tape has a facing region facing the negative electrode and a non-facing region not facing the negative electrode, and the non-facing region is provided with at least one slit or notch extending from an upper end of the protective tape toward a lower end of the protective tape. Aspect 2: The nonaqueous electrolyte secondary battery according to Aspect 1, wherein a positive electrode lead is connected to the positive electrode current collector exposed portion, and the slit and the notch do not face the positive electrode lead. Configuration 3: The non-facing region has a plurality of the notches, and at least some of the plurality of notches are provided at approximately equal intervals in the longitudinal direction of the positive electrode.Configuration 4: The non-facing region has a plurality of the notches, and the interval between adjacent notches in the longitudinal direction of the positive electrode is 0.5 mm or more and 10 mm or less.Configuration 5: The non-aqueous electrolyte secondary battery of any one of Configurations 1 to 4, wherein the length of the notch or the cutout in the width direction of the positive electrode is 50% or more of the length of the non-facing region.Configuration 6: The non-aqueous electrolyte secondary battery of any one of Configurations 1 to 5, wherein the length of the non-facing region in the width direction of the positive electrode is 0.1 mm or more and 3.0 mm or less. A positive electrode lead is connected to the positive electrode current collector exposed portion, and a ratio of a length of the protective tape to a length of the positive electrode lead in a longitudinal direction of the positive electrode is 2.0 or more and 10.0 or less. A nonaqueous electrolyte secondary battery according to any one of Aspects 1 to 7, wherein the cutout has a rectangular shape.Configuration 9: The nonaqueous electrolyte secondary battery according to any one of Configurations 1 to 8, wherein a plurality of exposed positive electrode current collector portions are provided on the surface of the positive electrode.

[0057] REFERENCE SIGNS LIST 10 non-aqueous electrolyte secondary battery, 11 positive electrode, 11A upper end, 11B lower end, 12 negative electrode, 12A upper end, 13 separator, 14 electrode body, 16 outer can, 16A bottom, 16B grooved portion, 17 sealing body, 18 insulating plate, 18A through hole, 20 positive electrode lead, 21 gasket, 22 upper current collector, 23 lower current collector, 24 sealing plate, 30 positive electrode current collector, 32 positive electrode mixture layer, 34 exposed portion of positive electrode current collector, 40 negative electrode current collector, 42 negative electrode mixture layer, 44 exposed portion of negative electrode current collector, 50 protective tape, 50A upper end, 50B lower end, 51 facing region, 52 non-facing region, 53 notch, 54 notch, 55 protruding region

Claims

1. A non-aqueous electrolyte secondary battery comprising: an electrode assembly in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound with a separator interposed therebetween; and a bottomed cylindrical exterior can that houses the electrode assembly, wherein the positive electrode has a positive electrode current collector and a positive electrode mixture layer provided on a surface of the positive electrode current collector, the surface of the positive electrode is provided with a positive electrode current collector exposed portion where the positive electrode current collector is exposed, the positive electrode current collector exposed portion is covered with a protective tape, the protective tape has a facing region that faces the negative electrode and a non-facing region that does not face the negative electrode, and the non-facing region is provided with at least one cut or notch extending from an upper end of the protective tape toward a lower end of the protective tape.

2. The nonaqueous electrolyte secondary battery according to claim 1, wherein a positive electrode lead is connected to said positive electrode current collector exposed portion, and said cutout and said notch do not face said positive electrode lead.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein a plurality of said notches are provided in said non-facing region, and at least some of said plurality of notches are provided at approximately equal intervals in the longitudinal direction of said positive electrode.

4. The non-aqueous electrolyte secondary battery according to claim 1, wherein a plurality of said notches are provided in said non-facing region, and the distance between adjacent said notches in the longitudinal direction of said positive electrode is 0.5 mm or more and 10 mm or less.

5. The nonaqueous electrolyte secondary battery according to claim 1, wherein the length of said cut or said notch in the width direction of said positive electrode is 50% or more of the length of said non-facing region.

6. The nonaqueous electrolyte secondary battery according to claim 1, wherein the length of the non-facing region in the width direction of the positive electrode is 0.1 mm or more and 3.0 mm or less.

7. The nonaqueous electrolyte secondary battery according to claim 1, wherein a positive electrode lead is connected to the exposed portion of the positive electrode current collector, and the ratio of the length of the protective tape to the length of the positive electrode lead in the longitudinal direction of the positive electrode is 2.0 or more and 10.0 or less.

8. The nonaqueous electrolyte secondary battery according to claim 1, wherein the notch has a rectangular shape.

9. The nonaqueous electrolyte secondary battery according to claim 1, wherein a plurality of exposed positive electrode current collector portions are provided on a surface of the positive electrode.

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