Secondary battery

Abstract

This secondary battery comprises: a wound electrode body (14) in which a positive electrode and a negative electrode (12) are wound via a separator; and a cylindrical outer can that houses the electrode body (14). A belt-shaped tape (50) for fixing a winding end is adhered to the outer peripheral surface of the electrode body (14). The tape (50) is adhered so that: the tape (50) does not overlap itself in the thickness direction of the tape (50); and both ends (51, 52) of the tape (50) in the length direction overlap each other in the axial direction of the electrode body (14).

Description

secondary battery

[0001] The present disclosure relates to secondary batteries.

[0002] Conventionally, secondary batteries have been widely known that include a wound electrode assembly in which a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween, and an outer can that houses the electrode assembly (see, for example, Patent Document 1). In wound electrode assemblies, a stop tape for maintaining the wound structure is generally attached to the outer peripheral surface of the electrode assembly. For example, Patent Document 1 discloses an electrode assembly in which stop tapes for fixing the winding end of the negative electrode are attached to both axial ends of the outer peripheral surface.

[0003] International Publication No. 2018 / 168628

[0004] However, if the stop tape overlaps the outer peripheral surface of the electrode body in the thickness direction of the tape, the outer diameter of the electrode body increases, which may make it difficult to insert the electrode body into the outer can. Therefore, the stop tape is generally attached over a length range of 50% to 90% of the circumferential length of the outer peripheral surface of the electrode body. In other words, the stop tape is attached with a gap between both ends.

[0005] However, if the stop tape is attached with a gap between its ends, the edge of the outer can may come into contact with the gap when the electrode body is inserted into the outer can, potentially causing the negative electrode plate located on the outer periphery of the electrode body to curl up. If the negative electrode plate curls up, it may come into contact with the positive electrode plate or the positive electrode lead electrically connected to the positive electrode plate, potentially causing a short circuit.

[0006] A secondary battery according to one embodiment of the present disclosure is a secondary battery comprising a wound electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, and a cylindrical outer can that houses the electrode body, and is characterized in that a strip of tape is attached to the outer surface of the electrode body to fix the end of the winding, and the tapes are attached so that the tapes do not overlap in the thickness direction of the tape, and so that both longitudinal ends of the tape overlap in the axial direction of the electrode body.

[0007] According to the secondary battery of one aspect of the present disclosure, a gap is provided between both ends of the winding stop tape, and the electrode plate can be prevented from rolling up when the electrode assembly is inserted into the outer can, thereby providing a secondary battery in which the occurrence of short circuits is suppressed.

[0008] Fig. 1 is a cross-sectional view of a secondary battery that is an example of an embodiment; Fig. 2 is a perspective view of an electrode body that is an example of an embodiment; Fig. 3 is a plan view of an electrode body that is an example of an embodiment, viewed from the radial outside; Fig. 4 is a plan view of an electrode body that is another example of an embodiment, viewed from the radial outside; Fig. 5 is a plan view of an electrode body that is another example of an embodiment, viewed from the radial outside; Fig. 6 is a plan view of an electrode body that is another example of an embodiment, viewed from the radial outside.

[0009] Hereinafter, an example of an embodiment of a secondary 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 embodiments obtained by selectively combining the components of the embodiments described below.

[0010] FIG. 1 is a schematic diagram illustrating a cross section of a secondary battery 10 according to an embodiment. Note that a strip-shaped tape 50, which will be described later, is not illustrated in FIG. 1 . As shown in FIG. 1 , the secondary battery 10 includes an electrode assembly 14, a non-aqueous electrolyte (not shown), and an outer can 16 that accommodates the electrode assembly 14 and the non-aqueous electrolyte. The electrode assembly 14 includes 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 outer can 16 is a cylindrical metal container with a bottom and an opening on one axial side, and the opening of the outer can 16 is closed by a sealing member 17. Hereinafter, for convenience of explanation, the sealing member 17 side of the secondary battery 10 will be referred to as the "top" and the bottom side of the outer can 16 will be referred to as the "bottom."

[0011] The non-aqueous electrolyte has lithium ion conductivity and may be a liquid electrolyte (electrolytic solution) or a solid electrolyte.

[0012] 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

[0013] 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.

[0014] The positive electrode 11, negative electrode 12, and separator 13 that make up 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 is formed to be slightly larger than the positive electrode 11 in order to prevent lithium deposition. That is, the negative electrode 12 is formed to be longer in the length direction and width direction (short direction) than the positive electrode 11. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and two separators 13 are arranged to sandwich the positive electrode 11. The secondary battery 10 includes insulating plates 18 and 19 arranged above and below the electrode assembly 14, respectively.

[0015] The positive electrode 11 has a positive electrode core 30 and a positive electrode mixture layer 31 formed on the positive electrode core 30. The positive electrode core 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. The positive electrode mixture layer 31 contains a positive electrode active material, a conductive agent, and a binder, and is preferably formed on both sides of the positive electrode core 30 except for the exposed portion of the positive electrode core (not shown) to which the positive electrode lead 20 is welded. 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, etc. to the positive electrode core 30, drying the coating, and then compressing it to form the positive electrode mixture layer 31 on both sides of the positive electrode core 30.

[0016] The positive electrode mixture layer 31 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, and lithium metal composite oxides containing Ni, Co, and Al.

[0017] Examples of the conductive agent contained in the positive electrode mixture layer 31 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 31 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.

[0018] The negative electrode 12 has a negative electrode core 40 and a negative electrode mixture layer 41 formed on the negative electrode core 40. For the negative electrode core 40, 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 with such a metal disposed on the surface layer, can be used. The negative electrode mixture layer 41 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 core 40 except for the negative electrode core exposed portion 42 described below. The negative electrode 12 can be produced by applying a negative electrode mixture slurry containing a negative electrode active material and a binder, etc., to the surface of the negative electrode core 40, drying the coating, and then compressing it to form the negative electrode mixture layer 41 on both sides of the negative electrode core 40.

[0019] The negative electrode mixture layer 41 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, as the negative electrode active material, 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 may be used. Among these, a composite material containing Si is preferred.

[0020] 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.

[0021] As in the case of the positive electrode mixture layer 31, the binder contained in the negative electrode mixture layer 41 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 41 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 SBR in combination with CMC or a salt thereof, PAA or a salt thereof, or the like. The negative electrode mixture layer 41 may contain a conductive agent such as CNT.

[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 negative electrode 12 is disposed on the outer peripheral surface of the electrode body 14. The electrode body 14 has a positive electrode lead 20 connected to a positive electrode core 30 by welding or the like. In the example shown in FIG. 1 , no negative electrode lead is provided, but an exposed portion of the negative electrode core 40 may be provided on the inner peripheral side of the electrode body 14 and the negative electrode lead may be connected to this exposed portion.

[0024] A negative electrode core exposed portion 42, in which the surface of the negative electrode core 40 is exposed, is formed on the outer peripheral surface of the electrode body 14. The negative electrode core exposed portion 42 may be formed on a portion of the outer peripheral surface of the electrode body 14, but is preferably formed on the entire outer peripheral surface. The negative electrode core exposed portion 42 may be formed on only one side (outer surface) of the negative electrode core 40 facing outward from the electrode body 14, or may be formed on both sides of the negative electrode core 40. The negative electrode core exposed portion 42 is formed, for example, within a range of a length equivalent to approximately one to two revolutions around the circumference of the electrode body 14 from a winding end (not shown), which is one end in the length direction of the negative electrode core 40 (negative electrode 12) located on the outer peripheral surface of the electrode body 14.

[0025] In the secondary battery 10, the negative electrode substrate exposed portion 42 of the negative electrode 12 contacts the inner surface of the outer can 16, electrically connecting the negative electrode 12 and the outer can 16. The negative electrode substrate exposed portion 42 contacts the inner surface of the outer can 16, for example, along the entire outer periphery of the electrode body 14. The positive electrode lead 20 passes through the through hole in the insulating plate 18 and extends toward the sealing body 17, and is connected by welding or the like to the underside of the internal terminal plate 23, which is the bottom plate of the sealing body 17. As a result, the sealing body 17 serves as a positive electrode external terminal, and the outer can 16 serves as a negative electrode external terminal.

[0026] As described above, the outer can 16 is a cylindrical metal container with a bottom and an opening on one axial side. A gasket 28 is provided between the outer can 16 and the sealing body 17 to ensure sealing of the battery interior and insulation between the outer can 16 and the sealing body 17. The outer can 16 has a grooved portion 21 formed on its side surface that protrudes inward and supports the sealing body 17. The grooved portion 21 is preferably formed in an annular shape along the circumferential direction of the outer can 16, and supports the sealing body 17 on its top surface. The sealing body 17 is fixed to the top of the outer can 16 by the grooved portion 21 and the open end of the outer can 16 that is crimped to the sealing body 17.

[0027] The sealing body 17 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are stacked. Each member constituting the sealing body 17 has, for example, a disk or ring shape, and each member except for the insulating member 25 is electrically connected to one another. The lower valve body 24 and the upper valve body 26 are connected at their respective centers, and the insulating member 25 is interposed between their respective peripheral edges. If an abnormality occurs in the battery and the internal pressure increases, the lower valve body 24 deforms and breaks, pushing the upper valve body 26 toward the cap 27, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. If the internal pressure further increases, the upper valve body 26 breaks, and gas is discharged from the opening of the cap 27.

[0028] The electrode assembly 14, and in particular the tape 50, will be described in detail below with reference to FIGS.

[0029] Fig. 2 is a perspective view of the electrode body 14. As shown in Fig. 2, tape 50 is attached to the outer peripheral surface of the electrode body 14. The tape 50 is a winding stop tape that fixes the winding end (not shown) of the negative electrode 12 to the outer peripheral surface of the electrode body 14 and maintains the wound structure of the electrode body 14. In this embodiment, as described above, the outer peripheral surface of the electrode body 14 is formed by the negative electrode core exposed portion 42 of the negative electrode 12.

[0030] The tape 50 is formed in a long, narrow strip shape. The tape 50 is attached to both axial ends of the electrode body 14 along the circumferential direction of the electrode body 14. The tape 50 is attached over the entire outer peripheral surface of the electrode body 14 so as not to overlap in the thickness direction of the tape 50. By attaching the tape 50 so as not to overlap in the thickness direction of the tape 50, it is possible to prevent the outer diameter of the electrode body 14 from increasing, and the electrode body 14 can be smoothly inserted into the outer can 16.

[0031] The width of the tape 50 is preferably 5% to 30% of the axial length of the electrode assembly 14, excluding narrow regions 53 and 54 (see FIG. 3 ), which will be described later. The width of the tape 50 is constant over the entire length, excluding the narrow regions 53 and 54. The tape 50 may be attached, for example, only within a range of 30% or less of the width (vertical length) of the negative electrode 12 from the upper and lower ends of the negative electrode substrate exposed portion 42 (negative electrode 12). The tape 50 may be attached with a predetermined gap between the upper and lower ends of the negative electrode substrate exposed portion 42 in consideration of attachment error; however, the gap between the tape 50 and the upper and lower ends of the negative electrode substrate exposed portion 42 is, for example, 1 mm or less.

[0032] The area to which the tape 50 is applied is preferably 20% or more, and more preferably 30% or more, of the area of ​​the outer peripheral surface of the electrode assembly 14. By applying the tape 50 to 20% or more of the area of ​​the outer peripheral surface of the electrode assembly 14, the effect of the tape 50 in suppressing the electrode plate from turning over, as described below, becomes more pronounced. Furthermore, the area to which the tape 50 is applied is preferably 70% or less, and more preferably 60% or less, of the area of ​​the outer peripheral surface of the electrode assembly 14. By applying the tape 50 to 70% or less of the area of ​​the outer peripheral surface of the electrode assembly 14, the area of ​​the negative electrode substrate exposed portion 42 disposed on the outer periphery of the electrode assembly 14 can be increased, thereby achieving low resistance of the secondary battery 10. Therefore, the area to which the tape 50 is applied is preferably 20% or more and 70% or less, and more preferably 30% or more and 60% or less, of the area of ​​the outer peripheral surface of the electrode assembly 14.

[0033] The tape 50 has a substrate made of an insulating resin and an adhesive layer formed on one side of the substrate. The tape 50 is preferably an insulating tape that is substantially non-conductive. The tape 50 may have a layer structure of three or more layers, and the substrate may be made of two or more layers of the same or different laminated films. The tape 50 may contain an inorganic filler such as titania, alumina, silica, or zirconia, and may have a layer containing an inorganic filler provided separately from the substrate and adhesive layer.

[0034] Examples of resins constituting the base material of the tape 50 include polyesters such as polyethylene terephthalate (PET), polypropylene (PP), polyimide (PI), polyphenylene sulfide (PPS), polyetherimide (PEI), and polyamide. The adhesive layer is formed, for example, by coating one side of the base material with an adhesive. The adhesive constituting the adhesive layer may be a hot-melt type that develops adhesiveness when heated or a thermosetting type that hardens when heated, but from the standpoint of productivity, etc., adhesives that are adhesive at room temperature are preferred. Examples of adhesives constituting the adhesive layer include acrylic adhesives and synthetic rubber adhesives.

[0035] The thickness of the tape 50 is not particularly limited, but is, for example, 20 μm or more and 100 μm or less, and preferably 30 μm or more and 70 μm or less.

[0036] Fig. 3 is a plan view of the electrode body 14 as seen from the radial outside. As shown in Fig. 3, the tape 50 is attached to both axial ends of the electrode body 14 along the circumferential direction of the electrode body 14. In this embodiment, the tape 50 attached to the upper axial end of the electrode body 14 and the tape 50 attached to the lower axial end of the electrode body 14 have the same shape.

[0037] As described above, the tape 50 is adhered over the entire outer peripheral surface of the electrode assembly 14 so as not to overlap in the thickness direction of the tape 50. Furthermore, when one end of the tape 50 in the longitudinal direction is defined as a first end 51 and the other end of the tape 50 in the longitudinal direction is defined as a second end 52, the tape 50 is adhered so that the first end 51 and the second end 52 overlap in the axial direction of the electrode assembly 14. This prevents the negative electrode 12 (negative electrode core exposed portion 42) from being exposed in the axial direction of the electrode assembly 14 on the outer peripheral surface of the electrode assembly 14. As a result, even if the edge of the outer can 16 hits the electrode assembly 14 when inserting the electrode assembly 14 into the outer can 16, the electrode plate can be prevented from curling up.

[0038] More specifically, assume that, for example, when the electrode assembly 14 is inserted into the outer can 16 from above, the edge of the outer can 16 abuts against the lower end 42A of the negative electrode substrate exposed portion 42 that is exposed from the gap 55 between the first end 51 and the second end 52. In this case, localized curling of the electrode plate may occur at the lower end 42A of the negative electrode substrate exposed portion 42. As described above, the tape 50 is attached so that the first end 51 and the second end 52 overlap in the axial direction of the electrode assembly 14. Therefore, even if the electrode assembly 14 is inserted further downward in the outer can 16 and the curling progresses in the insertion direction of the electrode assembly 14, i.e., along the axial direction of the electrode assembly 14, the tape 50 can block the progression of the curling. In other words, if the first end 51 and the second end 52 of the tape 50 are attached so as not to overlap in the axial direction of the electrode body 14, an area where the negative electrode 12 is exposed is generated on the outer peripheral surface of the electrode body 14 along the axial direction of the electrode body 14, and the progress of the curling may not be prevented. As a result, the curled negative electrode 12 may come into contact with the positive electrode 11 or the positive electrode lead 20, causing a short circuit.

[0039] In this embodiment, the first end 51 and the second end 52 of the tape 50 are inclined with respect to the axial direction of the electrode assembly 14 and are formed approximately parallel to each other. This makes it possible to prevent the tapes 50 from overlapping in the thickness direction, while preventing the negative electrode 12 (negative electrode core exposed portion 42) from being exposed over the entire axial direction on the outer circumferential surface of the electrode assembly 14. As a result, it is possible to suppress the progression of curling of the electrode plate that occurs when the electrode assembly 14 is inserted into the outer can 16.

[0040] The inclination angles of the first end 51 and the second end 52 with respect to the axial direction of the electrode body 14 are not particularly limited, but are, for example, 20° to 70°. The inclination angles of the first end 51 and the second end 52 with respect to the axial direction of the electrode body 14 may be different from each other. For example, the inclination angle of the first end 51 may be larger than the inclination angle of the second end 52.

[0041] The distance between the first end 51 and the second end 52, i.e., the circumferential length of the gap 55, is preferably 1.0 mm or more, and more preferably 2.0 mm or more. In this case, even taking into account production variations, it becomes easy to apply the tape 50 over the entire outer peripheral surface of the electrode body 14 without overlapping in the thickness direction of the tape 50. Furthermore, the distance between the first end 51 and the second end 52 may be uniform along the axial direction of the electrode body 14, or may vary along the axial direction of the electrode body 14. For example, the distance between the first end 51 and the second end 52 may be smaller in a lower region of the tape 50 and larger in an upper region of the tape 50.

[0042] The tape 50 has narrow regions 53, 54 in which the width of the tape 50 gradually decreases as it approaches the first end 51 and the second end 52. In this embodiment, in the narrow regions 53, 54, the width of the tape 50 decreases linearly as it approaches the first end 51 and the second end 52. Note that the width of the tape 50 may also decrease nonlinearly as it approaches the first end 51 and the second end 52. Furthermore, the narrow regions 53, 54 may be formed at only one of both longitudinal end portions of the tape 50.

[0043] Modified shapes of the tape 50 are shown with reference to FIGS. 4 to 6 . FIGS. 4 to 6 are plan views of the electrode assembly 14 viewed from the radially outer side. As shown in FIG. 4 , the tape 50A has a shape in which the first end 51A and the second end 52A are each bent. By bending the first end 51A and the second end 52A, the tape 50A can be attached so that the first end 51A and the second end 52A overlap in the axial direction of the electrode assembly 14 while preventing the tape 50A from overlapping in the thickness direction. In this embodiment, the first end 51A is bent in a V-shape so that the center in the width direction protrudes, and the second end 52A is bent in a V-shape so that the center in the width direction is recessed.

[0044] 5, the first end 51B and the second end 52B of the tape 50B may each have an arc shape. Even in this case, similar to the tapes 50 and 50A, the tape 50B can be attached so that the first end 51B and the second end 52B overlap in the axial direction of the electrode body 14 while preventing the tapes 50B from overlapping in the thickness direction. In this embodiment, the first end 51A is curved so that the center portion in the width direction protrudes, and the second end 52A is curved so that the center portion in the width direction is recessed. Furthermore, when the first end 51B and the second end 52B have an arc shape, stress concentration at the ends of the tape 50B is alleviated, making the tape 50B less likely to peel off from the outer peripheral surface of the electrode body 14.

[0045] 6, the first end 51C and the second end 52C of the tape 50C may each have a stepped shape. Even in this case, similar to the tapes 50, 50A, and 50B, the tape 50C can be attached so that the first end 51C and the second end 52C overlap in the axial direction of the electrode body 14 while preventing the tapes 50C from overlapping in the thickness direction. Note that the number of steps is not limited to one, and may be two or more.

[0046] The above embodiment can be modified as appropriate without impairing the object of the present disclosure. For example, in the above embodiment, two tapes 50 are attached to both axial ends of the electrode body 14, but this is not limited to this. For example, one tape 50 may be attached to the lower axial end of the electrode body 14. Alternatively, one tape 50 may be attached to the axial center of the electrode body 14. From the perspective of further suppressing short circuits due to curling of the electrode plates, it is preferable that the tape 50 be attached to at least the lower axial end of the electrode body 14, and more preferably to both axial end portions of the electrode body 14.

[0047] Furthermore, in the above embodiment, the gaps 55 between the two tapes 50 attached to both axial ends of the electrode body 14 are arranged in approximately the same straight line along the axial direction of the electrode body 14, but the arrangement of the gaps 55 is not limited to this.

[0048] The present disclosure will be further described by the following embodiments. Configuration 1: A secondary battery including a wound electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, and a cylindrical outer can housing the electrode assembly, wherein a strip of tape is attached to the outer peripheral surface of the electrode assembly to secure the winding end, and the tape is attached so that the tape does not overlap in the thickness direction of the tape, and the tape is attached so that the vicinity of both longitudinal ends of the tape overlap in the axial direction of the electrode assembly. Configuration 2: The secondary battery according to Configuration 1, wherein, in a side view from the radially outer side of the electrode assembly, the end of the tape is inclined with respect to the axial direction of the electrode assembly. Configuration 3: The secondary battery according to Configuration 1 or 2, wherein the tape has a narrow region in which the width of the tape gradually decreases toward the end of the tape in the longitudinal direction. Configuration 4: The secondary battery according to any one of Configurations 1 to 3, wherein, in a side view from the radially outer side of the electrode assembly, the end of the tape has a bent shape. Configuration 5: The secondary battery according to any one of Configurations 1 to 4, wherein the end of the tape has an arc shape in a side view from the radially outer side of the electrode body.Configuration 6: The secondary battery according to any one of Configurations 1 to 5, wherein the tape is attached to both axial end portions of the electrode body.Configuration 7: The secondary battery according to any one of Configurations 1 to 6, wherein the area to which the tape is attached is 20% or more of the area of ​​the outer peripheral surface of the electrode body.

[0049] REFERENCE SIGNS LIST 10 secondary battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 16 outer can, 17 sealing body, 18, 19 insulating plate, 20 positive electrode lead, 21 grooved portion, 23 internal terminal plate, 24 lower valve body, 25 insulating member, 26 upper valve body, 27 cap, 28 gasket, 30 positive electrode core, 31 positive electrode mixture layer, 40 negative electrode core, 41 negative electrode mixture layer, 42 negative electrode core exposed portion, 42A lower end portion, 50, 50A, 50B, 50C tape, 51, 51A, 51B, 51C first end, 52, 52A, 52B, 52C second end, 53, 54 narrow region, 57 gap

Claims

1. A secondary battery comprising: a wound electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; and a cylindrical outer can that houses the electrode assembly, wherein a strip of tape is attached to the outer circumferential surface of the electrode assembly to fix the end of the winding, and the tapes are attached so that the pieces of tape do not overlap in the thickness direction of the tape, and both ends of the tape in the longitudinal direction overlap in the axial direction of the electrode assembly.

2. The secondary battery according to claim 1, wherein, in a side view from the radially outer side of the electrode body, the end portions in the longitudinal direction of the tape are inclined with respect to the axial direction of the electrode body.

3. The secondary battery according to claim 1, wherein the tape has a narrow region in which the width of the tape gradually decreases toward an end of the tape in the longitudinal direction.

4. The secondary battery according to claim 1, wherein an end portion in the longitudinal direction of the tape has a bent shape in a side view from the radially outer side of the electrode body.

5. The secondary battery according to claim 1, wherein an end portion in the longitudinal direction of the tape has an arc shape when viewed from a radially outer side of the electrode body.

6. The secondary battery according to claim 1, wherein the tape is attached to both axial ends of the electrode body.

7. The secondary battery according to claim 1, wherein the area to which the tape is applied is 20% or more of the area of ​​the outer circumferential surface of the electrode body.

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