WO2025192233A1 - Secondary battery - Google Patents

Abstract

A secondary battery (10) comprising an electrode body (14), a strip-shaped tape (50) which is adhered to an outer peripheral surface of the electrode body (14) and is for fixing a winding end edge, and a bottomed cylindrical outer can (20) which accommodates the electrode body (14) and has a bottom surface portion (21) and a side surface portion (22), said secondary battery characterised in that the side surface portion (22) includes: a first section (25) that is in contact with the outer peripheral surface of the electrode body (14); and a second section (26) that is opposite at least the tape (50) and has an inner surface that is recessed radially outward in relation to the inner surface of the first section (25).

Description

secondary battery

This disclosure relates to secondary batteries.

Secondary batteries have been widely known, including a wound electrode assembly in which a positive electrode and a negative electrode are wound spirally with a separator interposed therebetween, and an outer can housing the electrode assembly. Patent Document 1 discloses a secondary battery in which an exposed negative electrode current collector portion made of copper foil or the like is provided at the outermost periphery of the electrode assembly. By abutting the exposed negative electrode current collector portion against the inner surface of the outer can, the outer can becomes the negative electrode terminal. Patent Document 1 also discloses attaching tape to the exposed negative electrode current collector portion provided at the outermost periphery of the electrode assembly to secure the winding end of the negative electrode.

International Publication No. 2018/168628

If tape is applied to the exposed portion of the negative electrode current collector located at the outermost periphery to secure the winding end of the negative electrode, repeated charging and discharging will cause the diameter of the electrode body to increase as the mixture layer expands during charging, which tends to concentrate stress at the edge of the tape. As a result, there is a risk of damage such as cracks occurring in the electrode plate near the edge of the tape.

One aspect of the secondary battery disclosed herein is a secondary battery comprising a wound electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a strip of tape attached to the outer peripheral surface of the electrode assembly for fixing the end of the winding; and a bottomed, cylindrical outer can that houses the electrode assembly and has a bottom and side surfaces, wherein the side surfaces include a first portion that abuts against the outer peripheral surface of the electrode assembly, and a second portion that faces at least the tape and whose inner surface is recessed radially outward relative to the inner surface of the first portion.

A secondary battery according to one aspect of the present disclosure can suppress damage to the electrode plates when repeatedly charged and discharged.

1 is an axial cross-sectional view of a secondary battery according to an embodiment of the present invention; 1 is a perspective view of an electrode assembly and a tape that constitute a secondary battery that is an example of an embodiment. 1 is an axial cross-sectional view of a secondary battery according to an embodiment, showing an enlarged view of a portion of an outer can. FIG. 2 is an axial cross-sectional view of a secondary battery according to another embodiment. FIG. 2 is an axial cross-sectional view of a secondary battery that is another example of the embodiment.

Below, 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, forms formed by selectively combining the components of the embodiments described below are also included in the present disclosure.

The overall configuration of a secondary battery 10, which is an example of an embodiment, will be described with reference to Figure 1. Figure 1 is an axial cross-sectional view of the secondary battery 10.

As shown in FIG. 1, the secondary battery 10 comprises an electrode assembly 14, a non-aqueous electrolyte (not shown), and an outer can 20 that houses the electrode assembly 14 and the non-aqueous electrolyte. The outer can 20 is a cylindrical metal container with a bottom that is open on one axial side, and the opening of the outer can 20 is closed by a sealing body 30. For ease of explanation, the sealing body 30 side of the secondary battery 10 will be referred to as the "top" and the bottom surface 21 side of the outer can 20 will be referred to as the "bottom".

As will be described in more detail below, 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 spirally wound with the separator 13 interposed between them. The electrode body 14 has a positive electrode lead 18 connected to the positive electrode 11 by welding or the like. In addition, a strip of tape 50 is attached to the outer periphery of the electrode body 14 to secure the winding end 12A (see Figure 2).

Insulating plates 16 and 17 are arranged above and below the electrode body 14. In the example shown in FIG. 1, the positive electrode lead 18 passes through a through hole in the insulating plate 16 and extends toward the sealing body 30. The positive electrode lead 18 is connected to the underside 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, serves as the positive electrode terminal. Note that the number of positive electrode leads 18 may be two or more. As will be described in more detail below, a negative electrode current collector exposed portion 44, where the negative electrode current collector 42 is exposed, is provided at the outermost periphery of the electrode body 14, and the negative electrode current collector exposed portion 44 abuts the inner surface of the outer can 20. This makes the outer can 20 the negative electrode terminal.

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

The liquid electrolyte (electrolytic solution) contains 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 mixed solvents 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 mixed solvents of these. The non-aqueous solvent may contain a halogen-substituted solvent (e.g., fluoroethylene carbonate) in which at least a portion of the hydrogen atoms of these solvents are replaced with halogen atoms such as fluorine. The electrolyte salt may be, for example, a lithium salt such as _LiPF6 .

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 for all-solid-state lithium-ion secondary batteries (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. Examples of polymer materials include fluororesin, acrylic resin, polyether resin, etc.

The outer can 20 is a cylindrical metal container with a bottom that is open on one axial side. The outer can 20 has a bottom portion 21 and a side portion 22 that forms the side of the secondary battery 10. The side portion 22 is the portion of the outer can 20 excluding the bottom portion 21, and includes an annular groove 23 and an opening 24. As will be described in more detail below, the side portion 22 has a first portion 25 that abuts the outer peripheral surface of the electrode body 14, and a second portion 26 that faces at least the tape 50 and has an inner surface that is recessed radially outward from the inner surface of the first portion 25.

The annular groove 23 is a portion of the side surface 22 that protrudes radially inward, and its upper surface supports the sealing body 30. The annular groove 23 is formed in a ring shape along the circumferential direction of the outer can 20. The annular groove 23 can be formed, for example, by spinning a portion of the side surface 22 radially inward to create a ring-shaped recess radially inward.

The opening 24 is an area of the side surface 22 above the annular groove 23, and forms the opening of the outer can 20. When the sealing body 30 is crimped and fixed to the outer can 20, the opening 24 is bent radially inward toward the peripheral edge of the sealing body 30.

The sealing body 30 is a disc-shaped member equipped with a safety valve. The sealing body 30 has a structure in which, from the electrode body 14 side, an internal terminal plate 31, an insulating member 32, and an external terminal plate 33 are stacked.

The internal terminal plate 31 is a metal plate including a thick portion 31A to which the positive electrode lead 18 is connected, and a thin central portion 31B that is separated from the thick portion 31A when the internal pressure of the battery exceeds a predetermined threshold. Multiple ventilation holes 31C are formed in the thick portion 31A.

The insulating member 32 insulates the area other than the connection between the internal terminal board 31 and the external terminal board 33. The insulating member 32 has an opening 32A formed in the radial center, and an air vent 32B formed in the area overlapping with the air vent 31C of the internal terminal board 31.

The external terminal plate 33 forms part of the upper surface of the secondary battery 10 and is disposed opposite the internal terminal plate 31 with the insulating member 32 sandwiched between them. The external terminal plate 33 has a thin-walled portion 33A that breaks when the internal pressure of the secondary battery 10 exceeds a predetermined threshold. The external terminal plate 33 is connected at its radial center to the central portion 31B of the internal terminal plate 31 by welding or the like. The radial outer side of the external terminal plate 33 is held between the annular groove 23 and the opening 24 formed by bending the opening of the outer can 20 inward, via a gasket 34.

When an abnormality occurs in the secondary battery 10 and the internal pressure rises, the generated high-temperature gas pushes the internal terminal plate 31 upward, causing the internal terminal plate 31 to break, separating the central portion 31B from the thick portion 31A and deforming the external terminal plate 33 so that it protrudes toward the outside of the battery. This interrupts the current path in the sealing body 30. Then, if the internal pressure of the secondary battery 10 rises further after the current path is interrupted, the thin portion 33A of the external terminal plate 33 breaks, forming a gas outlet in the external terminal plate 33.

Note that the structure of the sealing body 30 is not limited to the structure shown in FIG. 1, as long as it is capable of sealing the opening of the outer can 20. The sealing body 30 may, for example, have a convex cap that covers the external terminal board 33.

The gasket 34 is a sealing material interposed between the outer can 20 and the external terminal plate 33 that constitutes the sealing body 30. By providing the gasket 34, the gap between the outer can 20 and the external terminal plate 33 is sealed, ensuring the airtightness of the interior of the secondary battery 10. In other words, the gasket 34 is required to seal the gap between the outer can 20 and the external terminal plate 33.

Next, the configuration of the electrode assembly 14 and tape 50 will be described in detail with reference to Figures 1 and 2. Figure 2 is a perspective view of the electrode assembly 14 and tape 50.

As shown in Figures 1 and 2, the electrode assembly 14 has a wound structure in which the positive electrode 11 and negative electrode 12 are wound in a spiral shape with the separator 13 interposed between them. In other words, the separator 13 isolates the positive electrode 11 and negative electrode 12 from each other, preventing the positive electrode 11 and negative electrode 12 from coming into contact with each other and causing a short circuit.

The positive electrode 11, negative electrode 12, and separator 13 are all formed in a strip shape and are spirally wound around a winding core arranged along the winding axis, resulting in an alternating stack of electrodes 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, negative electrode 12, and separator 13 is the winding direction, and the width direction of the positive electrode 11, negative electrode 12, and separator 13 is the axial direction.

The positive electrode 11 has a positive electrode current collector 40 and a positive electrode mixture layer 41 formed on the positive electrode current collector 40. The positive electrode current collector 40 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 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 current collector 40 except for the portion to which the positive electrode lead 18 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, and a binder to the positive electrode current collector 40, drying the coating, and then compressing it to form the positive electrode mixture layer 41 on both sides of the positive electrode current collector 40.

The positive electrode mixture layer 41 contains particulate lithium metal composite oxide as the 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. It is particularly 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.

Examples of conductive agents contained in the positive electrode mixture layer 41 include carbon black such as acetylene black and ketjen black, graphite, carbon nanotubes (CNT), carbon nanofibers, graphene, and other carbon materials. Examples of binders contained in the positive electrode mixture layer 41 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 its salts, polyethylene oxide (PEO), and the like.

The negative electrode 12 has a negative electrode current collector 42 and a negative electrode mixture layer 43 formed on the negative electrode current collector 42. The negative electrode current collector 42 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 with such a metal disposed on its surface. The negative electrode mixture layer 43 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 42, excluding 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 a negative electrode active material and a binder to the surface of the negative electrode current collector 42, drying the coating, and then compressing it to form the negative electrode mixture layer 43 on both sides of the negative electrode current collector 42.

The negative electrode mixture layer 43 generally contains, as the negative electrode active material, a carbon material that reversibly absorbs and releases lithium ions. Suitable examples of carbon materials 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). The negative electrode active material may also contain 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.

Suitable examples of Si-containing composite materials include materials in which Si fine particles are dispersed in a _SiO2 phase or a silicate phase such as lithium silicate, or materials 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 surfaces of the composite material. Using a carbon material and a Si-containing composite material together as the negative electrode active material is preferred from the viewpoint of achieving both high capacity and high durability of the battery.

As with the positive electrode mixture layer 41, the binder contained in the negative electrode mixture layer 43 can be fluorine-containing resin, PAN, polyimide, acrylic resin, polyolefin, etc., but styrene-butadiene rubber (SBR) is preferred. Furthermore, the negative electrode mixture layer 43 preferably contains CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), etc. Among these, it is preferable to use a combination of SBR with CMC or a salt thereof, PAA or a salt thereof, etc. The negative electrode mixture layer 43 may also contain a conductive agent such as CNT.

A porous sheet having ion permeability and insulating properties is used for the separator 13. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. 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 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.

A negative electrode current collector exposed portion 44, where the surface of the negative electrode current collector 42 is exposed, is formed on the outer peripheral surface of the electrode body 14. The negative electrode current collector exposed portion 44 may be formed on part of the outer peripheral surface of the electrode body 14, but is preferably formed on the entire outer peripheral surface of the electrode body 14. The negative electrode current collector exposed portion 44 may be formed on only one side (outer surface) of the negative electrode current collector 42 facing outward from the electrode body 14, or may be formed on both sides of the negative electrode current collector 42. The negative electrode current collector exposed portion 44 is formed, for example, within a length range of approximately one to two revolutions around the circumference of the electrode body 14 from the winding end 12A, which is one longitudinal end of the negative electrode current collector 42 (negative electrode 12) located on the outer peripheral surface of the electrode body 14.

As shown in FIG. 2, tape 50 is attached to the outer peripheral surface of the electrode body 14. Tape 50 is a winding stop tape that secures the winding end 12A 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 current collector exposed portion 44 of the negative electrode 12. Tape 50 is attached to the negative electrode current collector exposed portion 44 so as to straddle the winding end 12A, which is one longitudinal end of the negative electrode 12, and secures the winding end 12A to the outer peripheral surface of the electrode body 14.

The tape 50 is formed in a long, narrow strip shape. The tape 50 is attached so that its length runs along the circumferential direction of the electrode body 14. The tape 50 runs along the circumferential direction of the electrode body 14, crossing the winding end 12A and adhering over an area of, for example, 50% or more of the circumferential length of the outer surface. The tape 50 may also be attached so that at least a portion overlaps in the thickness direction of the tape 50.

As shown in Figure 2, the tape 50 is preferably attached to both axial ends of the electrode body 14. In this case, for example, the axial ends of the electrode body 14 are prevented from coming into contact with the edge of the outer can 20 and curling up, making it easier to insert the electrode body 14 into the outer can 20.

The tape 50 preferably has a width equivalent to 5% or more and 25% or less of the axial length of the electrode body 14. Generally, the width of the tape 50 is constant over its entire length. For example, the tape 50 is attached only within a range of 25% or less of the width (vertical length) of the negative electrode 12 from the upper and lower ends of the negative electrode current collector exposed portion 44 (negative electrode 12). The tape 50 may be attached with a predetermined gap between the upper and lower ends of the negative electrode current collector exposed portion 44 to allow for attachment error, but the gap between the tape 50 and the upper and lower ends of the negative electrode current collector exposed portion 44 is, for example, 1 mm or less.

Tape 50 has a substrate made of insulating resin and an adhesive layer formed on one side of the substrate. Tape 50 is preferably an insulating tape that is substantially non-conductive. 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. Tape 50 may contain inorganic fillers such as titania, alumina, silica, zirconia, etc., and may have a layer containing an inorganic filler provided separately from the substrate and adhesive layer.

Examples of resins that make up the base material of 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 that makes up the adhesive layer may be a hot-melt type that becomes adhesive when heated, or a thermosetting type that hardens when heated, but from the perspective of productivity, etc., adhesives that are adhesive at room temperature are preferred. Examples of adhesives that make up the adhesive layer include acrylic adhesives and synthetic rubber adhesives.

The thickness of the tape 50 is, for example, 20 μm or more and 100 μm or less, and preferably 30 μm or more and 70 μm or less.

Next, the configuration of the side surface portion 22 of the outer can 20 will be described with reference to Figures 1 and 3. Figure 3 is an axial cross-sectional view of the secondary battery 10, showing an enlarged portion of the side surface portion 22.

As shown in Figures 1 and 3, the side surface 22 of the outer can 20 has a first portion 25 that abuts the outer peripheral surface of the electrode body 14, and a second portion 26 that faces at least the tape 50 and has an inner surface that is recessed radially outward relative to the inner surface of the first portion 25. In this embodiment, the second portion 26 is configured to be thinner than the first portion 25, so that the inner surface of the second portion 26 is recessed radially outward relative to the inner surface of the first portion 25.

The second portion 26 is formed over the entire area of the side surface 22 that faces the tape 50 and does not abut the tape 50. In other words, the tape 50 is positioned in a recess formed by the second portion 26. This prevents stress from being concentrated on the edge of the tape 50, even when the diameter of the electrode body 14 increases due to the expansion of the mixture layer during charging after repeated charging and discharging. As a result, damage such as cracking of the electrode plate near the edge of the tape 50 can be prevented.

As described above, the tape 50 is attached to both axial ends of the electrode body 14. Therefore, the first portion 25 is located at a position on the side surface portion 22 facing the axial center of the electrode body 14, and the second portions 26 are located on both axial sides of the first portion 25. Furthermore, in the example shown in FIG. 1, the bottom surface portion 21, the annular groove 23, and the opening 24 have approximately the same thickness as the second portion 26. In other words, in the outer can 20, only the first portion 25 is configured to be thick-walled.

The first portion 25 and the second portion 26 are arranged around the entire inner surface of the side portion 22. In other words, the first portion 25 and the second portion 26 are arranged in an annular shape along the circumferential direction of the inner surface of the side portion 22.

The inner surface of the second portion 26 is preferably recessed radially outward relative to the inner surface of the first portion 25 by a length at least 1.0 times the thickness of the tape 50, and more preferably by a length at least 1.2 times the thickness of the tape 50. In this case, even if the diameter of the electrode body 14 increases due to expansion of the mixture layer during charging after repeated charging and discharging, stress is further prevented from concentrating on the edge of the tape 50. Furthermore, when at least a portion of the tape 50 is attached so that they overlap in the thickness direction, the inner surface of the second portion 26 may be recessed radially outward relative to the inner surface of the first portion 25 by a length at least 2.0 times the thickness of the tape 50.

Furthermore, it is preferable that the inner surface of the second portion 26 be recessed radially outward from the inner surface of the first portion 25 by a length that is 5.0 times or less the thickness of the tape 50, and it is more preferable that it be recessed radially outward by a length that is 3.0 times or less the thickness of the tape 50. In this case, excessive enlargement of the outer diameter of the secondary battery 10 is prevented. Therefore, it is preferable that the inner surface of the second portion 26 be recessed radially outward from the inner surface of the first portion 25 by a length that is 1.0 to 5.0 times the thickness of the tape 50, and it is more preferable that it be recessed radially outward by a length that is 1.2 to 3.0 times the thickness of the tape 50.

As shown in Figure 3, it is preferable that the boundary 27 between the inner surface of the first portion 25 and the inner surface of the second portion 26 is rounded. In this case, damage such as cracking of the electrode plate caused by the outer surface of the electrode body 14 coming into contact with the boundary 27 between the inner surface of the first portion 25 and the inner surface of the second portion 26 can be prevented.

Furthermore, the second portion 26 has an inclined region 28 in which the inner surface is inclined radially outward more than the inner surface of the first portion 25 as it moves away from the first portion 25. In the example shown in FIG. 3 , in the inclined region 28, the thickness of the second portion 26 decreases linearly as it moves away from the first portion 25. Note that the thickness of the second portion 26 may also decrease non-linearly as it moves away from the first portion 25. The length of the inclined region 28 in the axial direction of the outer can 20 is not particularly limited, but may be, for example, 0.1 mm or more and 5.0 mm or less, or 0.5 mm or more and 3.0 mm or less.

The method for forming the second portion 26 is not particularly limited, but it can be formed, for example, by press working.

Next, a secondary battery 10, which is another example of an embodiment, will be described with reference to Figures 4 and 5. Figures 4 and 5 are axial cross-sectional views of a secondary battery 10, which is another example of an embodiment.

The secondary battery 10 shown in FIG. 4 differs from the secondary battery 10 shown in FIG. 1 in that the outer casing 20 has a substantially uniform thickness throughout. Furthermore, the first portion 25 and the second portion 26 are formed by recessing the approximate center of the side surface 22 from the radially outer side toward the radially inner side. In the example shown in FIG. 4 as well, stress is prevented from concentrating on the edge portions of the tape 50. As a result, damage such as cracking of the electrode plates near the edge portions of the tape 50 can be prevented.

The secondary battery 10 shown in Figure 5 differs from the secondary battery 10 shown in Figure 1 in that the bottom surface 21, annular groove 23, and opening 24 of the outer can 20 have approximately the same thickness as the first portion 25. In other words, only the area of the outer can 20 facing the tape 50 is thin-walled. In the example shown in Figure 5, stress is prevented from concentrating on the edge of the tape 50. As a result, damage such as cracking of the electrode plate near the edge of the tape 50 can be prevented.

The present disclosure is further illustrated by the following embodiments.
Configuration 1:
A secondary battery comprising: a wound electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a strip-shaped tape attached to the outer peripheral surface of the electrode body for fixing the end of the winding; and a bottomed cylindrical outer can that houses the electrode body and has a bottom and a side surface, wherein the side surface includes a first portion that abuts against the outer peripheral surface of the electrode body, and a second portion that faces at least the tape and has an inner surface that is recessed radially outward relative to the inner surface of the first portion.
Configuration 2:
2. The secondary battery according to claim 1, wherein the inner surface of the second portion is recessed radially outward from the inner surface of the first portion by a length that is 1.0 to 5.0 times the thickness of the tape.
Configuration 3:
3. The secondary battery according to claim 1, wherein a boundary between the inner surface of the first portion and the inner surface of the second portion is rounded.
Configuration 4:
The secondary battery according to any one of configurations 1 to 3, wherein the tape is attached to each of both end portions of the electrode body, and the second portion is disposed on each axial side of the first portion.
Configuration 5:
5. The secondary battery of any one of configurations 1 to 4, wherein the thickness of the second portion is smaller than the thickness of the first portion.
Configuration 6:
The secondary battery according to any one of configurations 1 to 5, wherein the second portion has an inclined region whose inner surface is inclined radially outward relative to the inner surface of the first portion as it moves away from the first portion.

10. Secondary battery, 11. Positive electrode, 12. Negative electrode, 12A. Winding end, 13. Separator, 14. Electrode body, 16, 17. Insulating plate, 18. Positive electrode lead, 20. Outer can, 21. Bottom portion, 22. Side portion, 23. Annular groove, 24. Opening, 25. First portion, 26. Second portion, 27. Boundary portion, 28. Sloped region, 30. Sealing body, 31. Internal terminal plate, 31A. Thick portion, 31B. Center portion, 31C. Ventilation hole, 32. Insulating member, 32A. Opening, 32B. Ventilation hole, 33. External terminal plate, 33A. Thin portion, 34. Gasket, 40. Positive electrode current collector, 41. Positive electrode mixture layer, 42. Negative electrode current collector, 43. Negative electrode mixture layer, 44. Exposed portion of negative electrode current collector, 50. Tape

Claims (6)

a wound electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween;
a strip-shaped tape attached to the outer peripheral surface of the electrode body for fixing the winding end;
a cylindrical outer can having a bottom and a side surface and containing the electrode assembly;
A secondary battery comprising:
The side surface portion is
a first portion abutting on an outer peripheral surface of the electrode body;
a second portion facing at least the tape and having an inner surface recessed radially outwardly relative to the inner surface of the first portion;
A secondary battery comprising: The secondary battery described in claim 1, wherein the inner surface of the second portion is recessed radially outward from the inner surface of the first portion by a length that is 1.0 to 5.0 times the thickness of the tape. The secondary battery of claim 1, wherein the boundary between the inner surface of the first portion and the inner surface of the second portion is rounded. The tape is attached to both ends of the electrode body,
The secondary battery according to claim 1 , wherein the second portions are disposed on both axial sides of the first portion. The secondary battery described in claim 1, wherein the thickness of the second portion is smaller than the thickness of the first portion. The secondary battery described in claim 1, wherein the second portion has an inclined region whose inner surface is inclined radially outward relative to the inner surface of the first portion as it moves away from the first portion.