Cylindrical battery

Abstract

Provided is a cylindrical battery characterized by comprising an electrode body (14) and an outer can, wherein: a negative electrode (12) is disposed on the outermost circumference of the electrode body (14); the surface of a negative electrode core body (50) and the inner surface of the outer can are in contact with each other; a band-shaped tape (60) for fixing a winding finish end (12A) of the negative electrode (12) is affixed to the outer circumferential surface of the electrode body (14); the tape (60) includes first regions (61) respectively provided at both winding direction ends of the tape (60), and a second region (62) provided between the first regions (61) in the winding direction of the tape (60) and having a tensile elongation rate that is greater than the tensile elongation rate of the first regions (61); and the second region (62) is disposed so as to extend across the winding finish end (12A) of the negative electrode (12).

Description

Cylindrical battery

[0001] The present disclosure relates to a cylindrical battery.

[0002] Conventionally, cylindrical batteries including an electrode body in which a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween, and an outer can that accommodates the electrode body are widely known. Patent Document 1 discloses a cylindrical battery in which a negative electrode core made of copper foil or the like is exposed on the outermost periphery of the electrode body. By bringing the negative electrode core into contact with the inner surface of the outer can, the outer can functions as a negative electrode terminal. Further, Patent Document 1 discloses that a tape is attached to the outer surface of the negative electrode provided on the outermost periphery of the electrode body to fix the winding end of the negative electrode.

[0003] International Publication No. 2018 / 168628

[0004] When a tape is attached to the outer surface of the negative electrode disposed on the outermost periphery to fix the winding end of the negative electrode, stress tends to concentrate in the vicinity of the winding end of the negative electrode due to an increase in the diameter of the electrode body accompanying expansion of the negative electrode mixture layer during charging. This may cause wrinkles in the outermost negative electrode, reduce the contact area between the outer surface of the negative electrode core and the inner surface of the outer can, and increase electrical resistance.

[0005] Note that when no tape is attached to the outer surface of the negative electrode disposed on the outermost periphery, the wound state of the positive electrode and the negative electrode may be loosened due to volume change of the negative electrode mixture layer during charge and discharge. This may increase the electrode plate distance between the positive electrode and the negative electrode, and increase electrical resistance.

[0006] A cylindrical battery according to one aspect of the present disclosure is a cylindrical battery comprising an electrode body in which a positive electrode and a negative electrode are wound with a separator between them, and a bottomed cylindrical outer casing that houses the electrode body, wherein the negative electrode has a negative electrode core and a negative electrode mixture layer disposed on at least one surface of the negative electrode core, the negative electrode is disposed on the outermost periphery of the electrode body, the surface of the negative electrode core and the inner surface of the outer casing are in contact, and a strip-shaped tape is attached to the outer circumferential surface of the electrode body to fix the end of the winding of the negative electrode, the tape includes first regions provided at both ends in the winding direction of the tape, and a second region provided between the first regions in the winding direction of the tape, the tensile elongation rate being greater than that of the first region, and the second region is arranged to straddle the end of the winding of the negative electrode.

[0007] According to a cylindrical battery in one aspect of this disclosure, it is possible to suppress the increase in the plate distance between the positive electrode and the negative electrode while suppressing the occurrence of wrinkles at the outermost negative electrode.

[0008] This is an axial cross-sectional view of a cylindrical battery, which is an example of an embodiment. This is a perspective view of an electrode body, which is an example of an embodiment. This is a plan view of a tape in an unfolded state, which is an example of an embodiment. This is a schematic diagram showing the unfolding of a tape, which is an example of an embodiment. This is a radial cross-sectional view of an electrode body, which is an example of an embodiment. This is a plan view of a tape in an unfolded state, which is another example of an embodiment.

[0009] Hereinafter, an example of an embodiment of the cylindrical battery according to this disclosure will be described in detail with reference to the drawings. The embodiment described below is merely an example, and this disclosure is not limited to the embodiments described below. Furthermore, forms obtained by selectively combining each component of the embodiments described below are included in this disclosure.

[0010] Referring to Figure 1, the overall configuration of a cylindrical battery 10, which is an example of an embodiment, will be described. Figure 1 is an axial cross-sectional view of the cylindrical battery 10.

[0011] As shown in Figure 1, the cylindrical battery 10 comprises an electrode body 14, a non-aqueous electrolyte (not shown), and an outer casing 20 that houses the electrode body 14 and the non-aqueous electrolyte. The outer casing 20 is a bottomed cylindrical metal container with one side open in the axial direction, and the opening of the outer casing 20 is sealed by a sealing body 30. For the sake of explanation, the side of the cylindrical battery 10 with the sealing body 30 will be referred to as "upper," and the side of the outer casing 20 with the bottom surface 21 will be referred to as "lower."

[0012] The electrode body 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound in a spiral shape via the separator 13. The separator 13 isolates the positive electrode 11 and the negative electrode 12 from each other, suppressing contact between the positive electrode 11 and the negative electrode 12 that would cause a short circuit. The electrode body 14 also has a positive electrode lead 15 connected to the positive electrode 11 by welding or the like. The number of positive electrode leads 15 is not particularly limited and may be two or more.

[0013] Insulating plates 16 and 17 are positioned above and below the electrode body 14, respectively. In the example shown in Figure 1, the positive electrode lead 15 extends towards the sealing body 30 through a through-hole in the insulating plate 16. The positive electrode lead 15 is connected to the lower surface of the internal terminal plate 31 of the sealing body 30 by welding or the like, and the external terminal plate 33, which is the top plate of the sealing body 30 and is electrically connected to the internal terminal plate 31, becomes the positive electrode terminal. Furthermore, as will be described in more detail later, a negative electrode core 50 constituting the negative electrode 12 is positioned on the outermost periphery of the electrode body 14, and the surface of the negative electrode core 50 is in contact with the inner surface of the side portion 22 of the outer can 20. As a result, the outer can 20 becomes the negative electrode terminal.

[0014] Non-aqueous electrolytes are lithium ion conductive. Non-aqueous electrolytes may be liquid electrolytes (electrolytes) or solid electrolytes.

[0015] A liquid electrolyte (electrolyte solution) comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include esters, ethers, nitriles, amides, and mixtures of two or more of these. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof. The non-aqueous solvent may also contain halogen-substituted solvents (e.g., fluoroethylene carbonate) in which at least some of the hydrogen atoms of the solvent are replaced with halogen atoms such as fluorine. Examples of electrolyte salts include LiPF4. ６ Lithium salts such as these are used.

[0016] 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, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, 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 a non-aqueous solvent and gels is used. Examples of polymer materials include fluororesins, acrylic resins, polyether resins, etc.

[0017] The outer casing 20 is a bottomed cylindrical metal container with an open top. The outer casing 20 has a bottom portion 21 and side portions 22 that form the side of the cylindrical battery 10. The side portions 22 are the parts of the outer casing 20 excluding the bottom portion 21 and include grooved portions 23. The opening edge of the side portion 22 is bent radially inward toward the peripheral edge of the sealing body 30 when the sealing body 30 is crimped and fixed to the outer casing 20.

[0018] The grooved portion 23 is a part of the side portion 22 that protrudes radially inward, and its upper surface supports the sealing body 30. The grooved portion 23 is formed in an annular shape along the circumferential direction of the outer can 20. The grooved portion 23 can be formed, for example, by spinning a part of the side portion 22 radially inward to create an annular recess on the radially inward side.

[0019] As described above, the sealing body 30 is a member that closes the opening of the outer can 20. In this embodiment, the sealing body 30 has a structure in which an internal terminal plate 31, an insulating member 32, and an external terminal plate 33 are stacked in order from the electrode body 14 side.

[0020] The internal terminal plate 31 is a metal plate that includes a thick-walled portion 31A to which the positive electrode lead 15 is connected, and a thin-walled central portion 31B that is detached from the thick-walled portion 31A when the internal pressure of the battery exceeds a predetermined threshold. Multiple ventilation holes 31C are formed in the thick-walled portion 31A.

[0021] The insulating member 32 insulates the portion of the internal terminal plate 31 and the external terminal plate 33 other than the connection portion. The insulating member 32 has an opening 32A in its radial center, and a ventilation hole 32B is formed in the portion that overlaps with the ventilation hole 31C of the internal terminal plate 31.

[0022] The external terminal plate 33 forms a part of the upper surface of the cylindrical battery 10 and is positioned opposite the internal terminal plate 31 with an insulating member 32 in between. The external terminal plate 33 has a thin-walled portion 33A that breaks when the internal pressure of the cylindrical battery 10 exceeds a predetermined threshold. The external terminal plate 33 is connected to the central portion 31B of the internal terminal plate 31 by welding or the like at its radial center. The radially outer side of the external terminal plate 33 is crimped and fixed to the outer casing 20 via a gasket 34.

[0023] When an abnormality occurs in the cylindrical battery 10 and the internal pressure rises, the high-temperature gas generated pushes the internal terminal plate 31 upward, causing it to rupture and the central portion 31B to separate from the thick portion 31A, and the external terminal plate 33 to deform so that it protrudes outward from the battery. This interrupts the current path in the sealing body 30. Then, if the internal pressure of the cylindrical battery 10 rises further after the current path has been interrupted, the thin portion 33A of the external terminal plate 33 ruptures, forming a gas outlet in the external terminal plate 33.

[0024] The structure of the sealing body 30 is not limited to the structure shown in Figure 1, as long as it can close the opening of the outer can 20. The sealing body 30 may, for example, have a convex cap that covers the external terminal plate 33.

[0025] The gasket 34 is a sealing material interposed between the outer casing 20 and the external terminal plate 33 that constitutes the sealing body 30. By providing the gasket 34, the gap between the outer casing 20 and the external terminal plate 33 is sealed, ensuring airtightness inside the cylindrical battery 10. In other words, the gasket 34 is required to seal the gap between the outer casing 20 and the external terminal plate 33.

[0026] Next, the configuration of the electrode body 14 will be described in detail with further reference to Figure 2. Figure 2 is a perspective view of the electrode body 14.

[0027] As shown in Figures 1 and 2, the electrode body 14 has a wound structure in which a positive electrode 11 and a negative electrode 12 are wound in a spiral shape via a separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 are all formed in a strip shape and are wound in a spiral shape around a winding core arranged along the winding axis, resulting in them being alternately stacked in the radial direction of the electrode body 14. In other words, in the electrode body 14, the longitudinal direction of the positive electrode 11, the negative electrode 12, and the separator 13 is the winding direction, and the width direction of the positive electrode 11, the negative electrode 12, and the separator 13 is the axial direction.

[0028] The positive electrode 11 comprises a positive electrode core 40 and a positive electrode mixture layer 41 formed on the positive electrode core 40. The positive electrode core 40 can be made of a metal foil that is stable within the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal arranged on its surface. The positive electrode mixture layer 41 contains a positive electrode active material, a conductive agent, and a binder, and is preferably formed on both sides of the positive electrode core 40, excluding the portion where the positive electrode lead 15 is welded. The positive electrode 11 can be manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core 40, drying the coating, and then compressing it to form the positive electrode mixture layer 41 on both sides of the positive electrode core 40.

[0029] The positive electrode composite layer 41 contains particulate lithium transition metal composite oxide as the positive electrode active material. The lithium transition metal composite oxide is a composite oxide containing metal elements such as Co, Mn, Ni, and Al in addition to Li. The metal elements constituting the lithium transition metal composite oxide are, 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 transition metal composite oxides containing Ni, Co, and Mn, and lithium transition metal composite oxides containing Ni, Co, and Al.

[0030] Examples of conductive agents included in the positive electrode mixture layer 41 include carbon black such as acetylene black and Ketjenblack, graphite, carbon nanotubes (CNTs), carbon nanofibers, and graphene. Examples of binders included in the positive electrode mixture layer 41 include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resins, and polyolefins. In addition, these resins may be used in combination with carboxymethylcellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

[0031] The negative electrode 12 comprises a negative electrode core 50 and a negative electrode mixture layer 51 formed on the negative electrode core 50. The negative electrode core 50 can be made of a metal foil that is stable in the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with the metal arranged on its surface. The thickness of the negative electrode core 50 is, for example, 5 μm or more and 50 μm or less, and may be 5 μm or more and 30 μm or less. The negative electrode mixture layer 51 contains a negative electrode active material, a binder, and optionally a conductive agent. The negative electrode 12 can be manufactured by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to the surface of the negative electrode core 50, drying the coating, and then compressing it to form the negative electrode mixture layer 51 on both sides of the negative electrode core 50.

[0032] The negative electrode mixture layer 51 generally contains a carbon material that reversibly intercepts and releases lithium ions as the negative electrode active material. A suitable example of the carbon material is graphite such as natural graphite such as flake graphite, lump graphite, or clay graphite, or artificial graphite such as lump graphite (MAG) or graphitized mesophase carbon microbeads (MCMB). The negative electrode mixture layer 51 may also contain a material as the negative electrode active material that includes at least one of an element that alloys with Li, such as Si or Sn, and a material containing such an element. In particular, it is preferable that the negative electrode mixture layer 51 contains a composite material containing Si as the negative electrode active material.

[0033] A preferred example of a composite material containing Si is SiO ２ Examples include materials in which Si nanoparticles are dispersed in a phase or silicate phase such as lithium silicate, or materials in which Si nanoparticles are dispersed in an amorphous carbon phase. A conductive layer, such as a carbon coating, may be formed on the particle surface of the composite material. By using a carbon material and a Si-containing composite material in combination as the negative electrode active material, it is possible to achieve higher battery capacity.

[0034] The binder in the negative electrode mixture layer 51 may be a fluororesin, PAN, polyimide, acrylic resin, polyolefin, etc., as in the positive electrode mixture layer 41, but styrene-butadiene rubber (SBR) is preferred. Furthermore, the negative electrode mixture layer 51 preferably contains CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), etc. In particular, it is preferable to use SBR in combination with CMC or a salt thereof, PAA or a salt thereof. The negative electrode mixture layer 51 may also contain a conductive agent such as CNT.

[0035] The separator 13 is made of a porous sheet having ion permeability and insulating properties. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator 13 include polyethylene, polyolefins such as polypropylene, and cellulose. The separator 13 may have a single-layer structure or a multi-layer structure. Furthermore, a heat-resistant resin layer, such as aramid resin, may be formed on the surface of the separator 13.

[0036] As shown in Figures 1 and 2, a negative electrode 12 is arranged on the outermost periphery of the electrode body 14. At least a portion of the negative electrode 12 arranged on the outermost periphery does not have the negative electrode mixture layer 51 on its outer surface, which is the radially outward-facing surface of the negative electrode core 50, and the outer surface of the negative electrode core 50 is exposed. In other words, at least a portion of the outer periphery surface of the electrode body 14 is composed of the negative electrode core 50. For the sake of explanation, the portion of the negative electrode 12 arranged near the outermost periphery in which the negative electrode mixture layer 51 is not arranged on at least the outer surface of the negative electrode core 50 and the outer surface of the negative electrode core 50 is exposed will be referred to as the "exposed core portion 52".

[0037] The core exposure portion 52 may be formed only on a part of the outer circumferential surface of the electrode body 14, but preferably it is formed over the entire outer circumferential surface of the electrode body 14. The core exposure portion 52 is formed, for example, in a range of about one to two turns of the circumference of the electrode body 14 from the winding end 12A, which is one end of the negative electrode 12 in the longitudinal direction. In the core exposure portion 52, the negative electrode mixture layer 51 may or may not be arranged on the inner surface of the negative electrode core body 50, which is the surface facing radially inward. Furthermore, in the core exposure portion 52, there may be a region on the inner surface of the negative electrode core body 50 where the negative electrode mixture layer 51 is arranged and a region on the inner surface of the negative electrode core body 50 where the negative electrode mixture layer 51 is not arranged.

[0038] Next, the structure of the tape 60 will be described in detail with further reference to Figures 3 to 5. Figure 3 is a plan view of the tape 60 in an unfolded state, Figure 4 is a schematic diagram showing the extension of the tape 60 shown in Figure 3, and Figure 5 is a radial cross-sectional view of the electrode body 14 in the area to which the tape 60 is attached. Note that in Figure 5, only a part of the outer circumference of the electrode body 14 is shown, and the positive electrode 11 and separator 13 are not shown.

[0039] In the following, as shown in Figure 3, the direction facing one side of the tape 60's winding direction may be referred to as the "X1 direction," and the direction facing the other side of the winding direction may be referred to as the "X2 direction." Also, the direction facing one side of the tape 60's width direction may be referred to as the "Y1 direction," and the direction facing the other side of the width direction may be referred to as the "Y2 direction."

[0040] As shown in FIGS. 2 and 3, a tape 60 is adhered to the outer peripheral surface of the electrode assembly 14. The tape 60 is a winding stopper tape for fixing the winding end 12A of the negative electrode 12 and maintaining the wound structure of the electrode assembly 14. The tape 60 is formed in an elongated strip shape, and is adhered such that the longitudinal direction of the tape 60 is along the circumferential direction of the electrode assembly 14. In other words, the longitudinal direction of the tape 60 coincides with the winding direction of the tape 60.

[0041] The tape 60 is adhered along the circumferential direction of the electrode assembly 14 so as to straddle the winding end 12A of the negative electrode 12. For example, the tape 60 may be adhered over a range of 50% or more of the circumferential length of the outermost periphery of the electrode assembly 14, or may be adhered over a range of 70% or more of the circumferential length of the outermost periphery of the electrode assembly 14. Further, the tape 60 may be adhered over the entire circumference of the outermost periphery of the electrode assembly 14.

[0042] In the present embodiment, two tapes 60 are respectively adhered to both upper and lower end sides of the electrode assembly 14. By adhering the two tapes 60 to both upper and lower end sides of the electrode assembly 14 respectively, for example, when inserting the electrode assembly 14 into the outer can 20, curling of the upper and lower end portions of the electrode assembly 14 caused by contact with the edge of the outer can 20 is suppressed, and insertion of the electrode assembly 14 into the outer can 20 becomes smoother. In addition, during charge and discharge, the diameter change of the electrode assembly 14 tends to be larger at the vertically central side of the electrode assembly 14 compared to both vertically end sides. Therefore, by adhering the two tapes 60 to both upper and lower end sides of the electrode assembly 14 respectively, the stress applied from the tapes 60 to the negative electrode 12 is relieved, and generation of wrinkles in the outermost negative electrode 12 can be further suppressed. In the present embodiment, the two tapes 60 respectively adhered to both upper and lower end sides of the electrode assembly 14 have substantially the same configuration.

[0043] Each tape 60 has, for example, a width corresponding to 5% or more and 25% or less of the width of the negative electrode 12. In the present embodiment, the width of the tape 60 is constant over the entire length. The tape 60 is adhered, for example, within a range of 30% or less of the width of the negative electrode 12 from the vicinity of both widthwise ends of the negative electrode 12.

[0044] The tape 60 includes, for example, a base material layer formed of an insulating resin, and an adhesive layer formed on one side of the base material layer. The tape 60 is preferably an insulating tape that has substantially no conductivity. The tape 60 may have a layer structure of three or more layers, and the base material layer may be formed of two or more layers of the same type or different types of laminated films. Further, the tape 60 may contain inorganic fillers such as titania, alumina, silica, zirconia, etc., and a layer containing the inorganic filler may be provided separately from the base material layer and the adhesive layer.

[0045] Examples of the resin constituting the base material layer of the tape 60 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 applying an adhesive to one side of the base material layer. The adhesive constituting the adhesive layer of the tape 60 may be a hot-melt type that develops adhesiveness when heated or a thermosetting type that cures by heating, but from the viewpoint of productivity, an adhesive that exhibits adhesiveness at room temperature is preferred. Examples of the adhesive constituting the adhesive layer include acrylic adhesives and synthetic rubber adhesives.

[0046] The thickness of the tape 60 is, for example, 10 µm or more and 50 µm or less, and may be 15 µm or more and 35 µm or less. Note that the thickness of the tape 60 means the total thickness of the tape 60 including the base material layer and the adhesive layer.

[0047] In the winding direction (longitudinal direction) of the tape 60, the tensile elongation percentage of the tape 60 changes locally. Specifically, as shown in FIG. 3, the tape 60 includes first regions 61 respectively provided at both ends of the tape 60 in the winding direction, and a second region 62 provided between the first regions 61 in the winding direction of the tape 60 and having a tensile elongation percentage larger than that of the first regions 61. In the first regions 61, the tape 60 has a substantially constant tensile elongation percentage. Note that the tensile elongation percentage of the tape 60 in this specification means the tensile elongation percentage in the winding direction of the tape 60 measured based on the method defined in JIS Z 0237 (2009).

[0048] When the winding end 12A of the negative electrode 12 is fixed with tape 60, it has become clear that stress is locally concentrated near the winding end 12A of the negative electrode 12 due to the increase in the diameter of the electrode body 14 caused by the expansion of the negative electrode mixture layer 51 during charging. As a result, wrinkles may form on the outermost negative electrode core body 50, reducing the contact area between the outer surface of the negative electrode core body 50 and the inner surface of the outer casing 20, which may increase electrical resistance.

[0049] In this embodiment, the second region 62 of the tape 60 is positioned to straddle the winding end 12A of the negative electrode 12. By positioning the second region 62, which has a high tensile elongation rate, in the region overlapping with the winding end 12A of the negative electrode 12, when the diameter of the electrode body 14 increases due to the expansion of the negative electrode mixture layer 51 during charging, the second region 62 stretches preferentially. As a result, the stress applied near the winding end 12A of the negative electrode 12 is relieved, and the occurrence of wrinkles in the outermost negative electrode core 50 can be suppressed. Consequently, the contact area between the outer surface of the negative electrode core 50 and the inner surface of the outer casing 20 is secured, and the increase in electrical resistance can be suppressed.

[0050] Furthermore, if the tensile elongation rate is increased over the entire winding direction of the tape 60, or if the tape 60 is not provided, the winding state of the positive electrode 11 and negative electrode 12 may be unraveled due to volume changes in the negative electrode mixture layer 51 during charging and discharging. This increases the plate distance between the positive electrode 11 and the negative electrode 12, which may actually increase the electrical resistance. Therefore, by providing a first region 61 with a low tensile elongation rate at both ends of the tape 60 in the winding direction, and a second region 62 with a high tensile elongation rate in the region overlapping with the winding end 12A of the negative electrode 12, it is possible to suppress the unraveling of the winding state of the positive electrode 11 and the negative electrode 12 while suppressing the occurrence of wrinkles on the outermost negative electrode 12. As a result, a cylindrical battery 10 with reduced electrical resistance can be realized.

[0051] The ratio of the tensile elongation of the second region 62 to the tensile elongation of the first region 61 should be greater than 1, but is preferably 1.2 or greater, and more preferably 1.5 or greater. By setting the ratio of the tensile elongation of the second region 62 to the tensile elongation of the first region 61 to 1.2 or greater, the stress applied near the winding end 12A of the negative electrode 12 is further relieved, and the occurrence of wrinkles in the outermost negative electrode core 50 can be further suppressed. There is no particular upper limit to the ratio of the tensile elongation of the second region 62 to the tensile elongation of the first region 61; for example, it is 5. Therefore, the ratio of the tensile elongation of the second region 62 to the tensile elongation of the first region 61 is preferably 1.2 or greater and 5 or less, and more preferably 1.5 or greater and 5 or less.

[0052] As shown in Figure 3, the tape 60 of this embodiment is provided with a plurality of slits 70 in the middle of the tape 60 in the winding direction. The slits 70 extend along the width direction, which is perpendicular to the winding direction of the tape 60. When the diameter of the electrode body 14 increases during charging, the slits 70 open and the width of the slits 70 expands, as shown in Figure 4. As a result, the tape 60 stretches in the winding direction. Therefore, the region where the slits 70 are formed has a higher tensile elongation rate than the ends of the tape 60 in the winding direction. Thus, the region where slits 70 are not formed on both ends of the tape 60 in the winding direction becomes the first region 61, and the region where slits 70 are formed becomes the second region 62. More specifically, the region of the tape 60 from the end of the slit 70 on the X1 direction side to the end of the slit 70 on the X2 direction side becomes the second region 62.

[0053] In the example shown in Figure 3, the slit 70 includes a first slit 71 that contacts either end of the tape 60 in the width direction, and a second slit 72 that does not contact either end of the tape 60 in the width direction, but is provided in the middle of the tape 60 in the width direction. When the slit 70 includes the first slit 71 and the second slit 72, the second region 62 becomes easier to stretch when the diameter of the electrode body 14 increases during charging, and the occurrence of wrinkles in the outermost negative electrode 12 can be further suppressed.

[0054] The first slit 71 includes first slits 71A, 71B, and 71C that are in contact with the Y1 direction end of the tape 60, and first slits 71D, 71E, and 71F that are in contact with the Y2 direction end of the tape 60. The first slits 71A and 71D, 71B and 71E, and 71C and 71F are each positioned to overlap in the width direction of the tape 60.

[0055] Each of the first slits 71A to 71F has, for example, the same length and width. The length of the first slits 71A to 71F is preferably 10% to 45% of the width of the tape 60, and more preferably 15% to 40% of the width of the tape 60. When the length of the first slits 71A to 71F is 10% to 45% of the width of the tape 60, the second region 62 stretches more easily when the diameter of the electrode body 14 increases. The width of the first slits 71A to 71F is not particularly limited, and is, for example, 0.1 mm to 1 mm.

[0056] Furthermore, the second slit 72 includes a second slit 72A provided between the first slit 71A and the first slit 71B in the winding direction of the tape 60, a second slit 72B provided between the first slit 71B and the first slit 71C, and a second slit 72C provided on the X1 side of the first slit 71C. The second slit 72A is provided at the central position between the first slit 71A and the first slit 71B in the winding direction of the tape 60, and the second slit 72B is provided at the central position between the first slit 71B and the first slit 71C in the winding direction of the tape 60. The second slit 72C is provided at a position where the distance between the second slit 72C and the second slit 72B is the same as the distance between the second slit 72A and the second slit 72B.

[0057] Each of the second slits 72A to 72C has, for example, the same length and width. The length of the second slits 72A to 72C is preferably 20% to 90% of the width of the tape 60, and more preferably 25% to 85% of the width of the tape 60. When the length of the second slits 72A to 72C is 20% to 90% of the width of the tape 60, the second region 62 stretches more easily when the diameter of the electrode body 14 increases. The width of the second slits 72A to 72C is not particularly limited, and is, for example, 0.1 mm to 1 mm, similar to the first slit 71.

[0058] Preferably, the second slit 72 is provided so as to overlap with the first slit 71 in the winding direction of the tape 60. In this case, when the diameter of the electrode body 14 increases during charging, the opening width of the slit 70 increases, making it easier for the second region 62 to stretch further.

[0059] Furthermore, the distance between the first slit 71 and the second slit 72 adjacent to each other in the winding direction of the tape 60 is preferably 5% to 30% of the length of the second region 62 in the winding direction of the tape 60. In this case, the strength of the tape 60 is ensured while the second region 62 is more easily stretched when the diameter of the electrode body 14 increases during charging.

[0060] The arrangement of the slits 70, as well as their shape, including their length and width, are not limited to the configuration shown in Figure 3. For example, the slits 70 may consist of only one of the first slit 71 and the second slit 72. Also, at least a portion of the slits 70 may extend along the winding direction of the tape 60.

[0061] As shown in Figure 5, in the radial cross-section of the electrode body 14, θ1 is defined as the angle formed by a straight line L1 connecting the winding center Z of the electrode body 14 and the winding end 12A of the negative electrode 12, and a straight line L2 connecting the winding center Z of the electrode body 14 and the X1 direction end 62X of the second region 62. Similarly, θ2 is defined as the angle formed by the above straight line L1 and a straight line L3 connecting the winding center Z of the electrode body 14 and the X2 direction end 62Y of the second region 62. In this case, θ1 and θ2 are preferably 5° or more, and more preferably 10° or more. In this case, when the diameter of the electrode body 14 increases due to the expansion of the negative electrode mixture layer 51 during charging, the second region 62 becomes easier to stretch, and the stress applied near the winding end 12A of the negative electrode 12 is further relieved. As a result, the occurrence of wrinkles in the outermost negative electrode core 50 is further suppressed, and the contact area between the outer surface of the negative electrode core 50 and the inner surface of the outer casing 20 is ensured. In this specification, the winding center Z of the electrode body 14 is defined as the center of the circumscribed circle of the electrode body 14 in the radial cross-section of the electrode body 14.

[0062] Furthermore, θ1 and θ2 are preferably 90° or less, and more preferably 60° or less. In this case, it becomes easier to secure the area of ​​the first region 61, and the unwinding of the winding state of the positive electrode 11 and the negative electrode 12 can be further suppressed. Therefore, θ1 and θ2 are preferably 5° or more and 90° or less, and more preferably 10° or more and 60° or less.

[0063] In this embodiment, the tape 60 is attached such that the central part of the second region 62 in the winding direction of the tape 60 overlaps with the winding end 12A of the negative electrode 12. In other words, θ1 and θ2 are the same. However, the arrangement of the tape 60 is not limited to this, and θ1 may be larger than θ2, or θ1 may be smaller than θ2.

[0064] Next, a modified version of the tape 60 will be described with reference to Figure 6. Figure 6 is a plan view of the modified tape 60 in an unfolded state, and corresponds to Figure 3.

[0065] The tape 60 shown in Figure 6 has recesses 80 that are indented inward in the width direction at both ends of the tape 60 in the width direction. The recesses 80 have, for example, a rectangular shape in plan view. In the winding direction of the tape 60, the width of the tape 60 is smaller in the region where the recesses 80 are provided compared to the region where the recesses 80 are not provided. As a result, the tensile elongation rate of the region where the recesses 80 are provided can be made greater than the tensile elongation rate of the region where the recesses 80 are not provided. Therefore, the region of the tape 60 where the recesses 80 are not formed becomes the first region 61, and the region where the recesses 80 are formed and which is narrower than the first region 61 becomes the second region 62.

[0066] In the example shown in Figure 6, one recess 80 is provided at each end of the tape 60 in the width direction. Furthermore, the recesses 80 provided at each end of the tape 60 in the width direction are positioned to coincide with each other in the width direction of the tape 60. In addition, the center of the recess 80 in the winding direction coincides with the center of the tape 60 in the winding direction. Note that the arrangement of the recesses 80 is not limited to this, and for example, the recesses 80 may be provided at only one end of the tape 60 in the width direction.

[0067] The width of the second region 62 should be smaller than the width of the first region 61, but it is preferably 80% or less of the width of the first region 61, and more preferably 60% or less of the width of the first region 61. When the width of the second region 62 is 80% or less of the width of the first region 61, the second region 62 is more likely to stretch when the diameter of the electrode body 14 increases during charging. The lower limit of the width of the second region 62 is, for example, 20% of the width of the first region 61. When the width of the second region 62 is less than 20% of the width of the first region 61, the tape 60 may break starting from the second region 62, and the winding state of the positive electrode 11 and the negative electrode 12 may be undone. Therefore, the width of the second region 62 is preferably 20% or more and 80% or less of the width of the first region 61, and more preferably 20% or more and 60% or less of the width of the first region 61. Furthermore, if the width of the second region 62 differs in the winding direction of the tape 60, the width of the second region 62 referred to above means the minimum width in the second region 62.

[0068] In the examples shown in Figures 3 to 6, a second region 62 with a high tensile elongation rate is formed on the center side of the tape 60 in the winding direction by providing a slit 70 or recess 80 on the center side of the tape 60 in the winding direction. However, the method of forming the second region 62 is not limited to these. For example, the second region 62 with a high tensile elongation rate may be formed on the center side of the tape 60 in the winding direction by changing the thickness of the tape 60 between the center side and both ends of the winding direction.

[0069] Furthermore, in the examples shown in Figures 3 to 6, the tape 60 is attached so that its longitudinal direction aligns with the circumferential direction of the electrode body 14, and the longitudinal direction of the tape 60 coincides with the winding direction of the tape 60. However, the arrangement of the tape 60 is not limited to this. For example, the tape 60 may be attached so that its short direction aligns with the circumferential direction of the electrode body 14, and the short direction of the tape 60 coincides with the winding direction of the tape 60.

[0070] The present disclosure will be further described by the following embodiments. Configuration 1: A cylindrical battery comprising an electrode body in which a positive electrode and a negative electrode are wound with a separator between them, and a bottomed cylindrical outer casing for housing the electrode body, wherein the negative electrode has a negative electrode core and a negative electrode mixture layer disposed on the negative electrode core, the negative electrode is disposed on the outermost periphery of the electrode body, the surface of the negative electrode core and the inner surface of the outer casing are in contact, and a strip-shaped tape is attached to the outer circumferential surface of the electrode body to fix the winding end of the negative electrode, the tape includes first regions provided at both ends of the tape in the winding direction, and a second region provided between the first regions in the winding direction of the tape, the tensile elongation rate of which is greater than that of the first region, and the second region is arranged to straddle the winding end of the negative electrode. Configuration 2: The cylindrical battery according to Configuration 1, wherein, in the radial cross-section of the electrode body, when θ1 is the angle formed by a straight line connecting the winding center of the electrode body and the winding end of the negative electrode and a straight line connecting the winding center of the electrode body and one end of the second region in the winding direction, and θ2 is the angle formed by a straight line connecting the winding center of the electrode body and the winding end of the negative electrode and a straight line connecting the winding center of the electrode body and the other end of the second region in the winding direction, θ1 and θ2 are 5° or more and 90° or less. Configuration 3: The cylindrical battery according to Configuration 1 or 2, wherein the second region is provided with a plurality of slits. Configuration 4: The cylindrical battery according to Configuration 3, wherein the slits include a first slit that contacts either end of the tape in the width direction, and a second slit that does not contact either end of the tape in the width direction but is provided in the middle of the tape in the width direction. Configuration 5: The cylindrical battery according to Configuration 4, wherein the second slit is provided so as to overlap the first slit with the winding direction of the tape. Configuration 6: The cylindrical battery according to Configuration 4 or 5, wherein the length of the first slit in the width direction of the tape is 10% or more and 45% or less of the width of the tape. Configuration 7: The cylindrical battery according to any one of Configurations 4 to 6, wherein the length of the second slit in the width direction of the tape is 20% or more and 90% or less of the width of the tape.Configuration 8: The cylindrical battery according to Configuration 5, wherein the distance between adjacent first and second slits in the winding direction of the tape is 5% or more and 30% or less of the length of the second region in the winding direction of the tape. Configuration 9: The cylindrical battery according to Configuration 1 or 2, wherein the width of the second region is smaller than the width of the first region. Configuration 10: The cylindrical battery according to Configuration 9, wherein the width of the second region is 20% or more and 80% or less of the width of the first region.

[0071] 10 Cylindrical battery, 11 Positive electrode, 12 Negative electrode, 12A End of winding, 13 Separator, 14 Electrode body, 15 Positive electrode lead, 16, 17 Insulating plate, 20 Outer can, 21 Bottom part, 22 Side part, 23 Grooved part, 30 Sealing body, 31 Internal terminal plate, 31A Thick part, 31B Center part, 31C Ventilation hole, 32 Insulating member, 32A Opening, 32B Ventilation hole, 33 External terminal plate, 33A Thin part, 34 Gasket, 40 Positive electrode core, 41 Positive electrode mixture layer, 50 Negative electrode core, 51 Negative electrode mixture layer, 52 Core exposed part, 60 Tape, 61 First region, 62 Second region, 70 Slits, 71, 71A, 71B, 71C, 71D, 71E, 71F First slits, 72, 72A, 72B, 72C Second slit, 80 Recess, Z Winding center

Claims

1. A cylindrical battery comprising: an electrode body in which a positive electrode and a negative electrode are wound with a separator between them; and a bottomed cylindrical outer casing for housing the electrode body, wherein the negative electrode has a negative electrode core and a negative electrode mixture layer disposed on at least one surface of the negative electrode core; the negative electrode is disposed on the outermost periphery of the electrode body, and the surface of the negative electrode core is in contact with the inner surface of the outer casing; a strip-shaped tape is attached to the outer circumferential surface of the electrode body to fix the winding end of the negative electrode, and the tape includes: first regions provided at both ends of the tape in the winding direction; and second regions provided between the first regions in the winding direction of the tape, the tensile elongation rate of which is greater than that of the first regions; and the second region is arranged to straddle the winding end of the negative electrode.

2. In the radial cross-section of the electrode body, when θ1 is the angle formed by a straight line connecting the winding center of the electrode body and the winding end of the negative electrode and a straight line connecting the winding center of the electrode body and one end of the winding direction of the second region, and θ2 is the angle formed by a straight line connecting the winding center of the electrode body and the winding end of the negative electrode and a straight line connecting the winding center of the electrode body and the other end of the winding direction of the second region, θ1 and θ2 are 5° or more and 90° or less, the cylindrical battery according to claim 1.

3. The cylindrical battery according to claim 1, wherein the second region is provided with a plurality of slits.

4. The cylindrical battery according to claim 3, wherein the slit includes a first slit that contacts either end of the tape in the width direction, and a second slit that does not contact either end of the tape in the width direction but is provided in the middle of the tape in the width direction.

5. The cylindrical battery according to claim 4, wherein the second slit is provided so as to overlap with the first slit in the winding direction of the tape.

6. The cylindrical battery according to claim 4, wherein the length of the first slit in the width direction of the tape is 10% or more and 45% or less of the width of the tape.

7. The cylindrical battery according to claim 4, wherein the length of the second slit in the width direction of the tape is 20% or more and 90% or less of the width of the tape.

8. The cylindrical battery according to claim 5, wherein the distance between the first slit and the second slit adjacent to each other in the winding direction of the tape is 5% or more and 30% or less of the length of the second region in the winding direction of the tape.

9. The cylindrical battery according to claim 1, wherein the width of the second region is smaller than the width of the first region.

10. The cylindrical battery according to claim 9, wherein the width of the second region is 20% or more and 80% or less of the width of the first region.

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