Cylindrical secondary battery

Abstract

The present invention is characterized by comprising: a bottomed cylindrical exterior can (20) accommodating an electrode body; and a cap member (40) joined to an outer surface of the exterior can (20), the exterior can (20) having a groove entry part (23) that is recessed inward in the radial direction of the exterior can (20) and a crimped part (26) which is provided at an opening (24) of the exterior can (20) and which extends inward in the radial direction of the exterior can (20), the cap member (40) having a top surface part (41) which covers the outer surface of the crimped part (26) and extends inward in the radial direction of the exterior can (20), a groove-disposed part (42) disposed inside the groove entry part (23), and a connecting part (43) connecting the top surface part (41) and the groove-disposed part (42), the top surface part (41) having a weld part (44) joined to the crimped part (26), and a recessed part (45) being provided in a region thereof more radially inward than the weld part (44).

Description

Cylindrical secondary battery

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

[0002] A cylindrical secondary battery generally includes a wound electrode body, a bottomed cylindrical outer can that houses the electrode body, and a sealing body that closes the opening of the outer can. In the outer can, a caulking portion is formed where the opening edge is bent inward to press the sealing body via a gasket. Cylindrical secondary batteries are characterized by being resistant to shock and easy to modularize. In applications that require a large capacity, a plurality of cylindrical secondary batteries are electrically connected and modularized. At this time, leads for connecting the cylindrical secondary batteries to each other are joined to the external terminals of the cylindrical secondary batteries by laser welding or the like (see, for example, Patent Document 1).

[0003] In a cylindrical secondary battery, for example, the sealing body serves as the positive electrode external terminal, and the outer can serves as the negative electrode external terminal. Patent Document 2 discloses a technique in which a cap member is provided at the caulking portion of the outer can, which is the negative electrode external terminal, close to the sealing body, and a current collecting terminal on the negative electrode side is welded to the cap member. In this case, since the current collecting terminals on the positive electrode side and the negative electrode side can be arranged on one end side in the axial direction of the cylindrical secondary battery, for example, the size of the battery module can be reduced.

[0004] Japanese Patent Application Laid-Open No. 2006-261083 International Publication No. 2024 / 161945

[0005] When abnormal heat generation occurs in a cylindrical secondary battery, the internal pressure of the battery may increase, and the sealing body may deform convexly toward the outside of the battery. At this time, in a battery provided with a cap member at the caulking portion of the outer can as described in Patent Document 2, as the sealing body deforms, the cap member is pressed toward the outside of the battery. As a result, the caulking portion that joins with the cap member is also pressed toward the outside of the battery. Consequently, the caulking portion that presses the sealing body may come off, and the sealing body may be released. If the sealing body is released, for example, the materials inside the battery may scatter outside, which may affect the devices around the battery.

[0006] A cylindrical secondary battery according to one aspect of the present disclosure comprises an electrode body in which a positive electrode and a negative electrode are wound with a separator between them, a bottomed cylindrical outer casing that houses the electrode body, a sealing body that closes the opening of the outer casing, and a cap member joined to the outer surface of the outer casing, wherein the outer casing has a grooved portion provided on the side of the outer casing that is recessed radially inward of the outer casing, and a crimped portion provided at the opening of the outer casing that extends radially inward of the outer casing, and the cap member covers the outer surface of the crimped portion and extends radially inward of the outer casing, forming the top surface of the cylindrical secondary battery, a grooved portion arranged inside the grooved portion, and a connecting portion that connects the top surface portion and the grooved portion, wherein the top surface portion has a welded portion joined to the crimped portion, and a recess is provided in a region radially inward of the welded portion.

[0007] According to a cylindrical secondary battery in one aspect of this disclosure, a cap member is provided at the crimped portion of the outer casing, while preventing the sealing body from opening when the battery overheats abnormally.

[0008] This is an axial cross-sectional view of a cylindrical secondary battery, which is an example of an embodiment. This is an enlarged view of section A in Figure 1. This is a schematic diagram showing the appearance of the opening when the internal pressure of the battery rises in a cylindrical secondary battery, which is an example of an embodiment. This is a schematic diagram showing the appearance of the opening when the internal pressure of the battery rises in a cylindrical secondary battery, which is a comparative example. This is a schematic diagram showing the appearance of the opening when the internal pressure of the battery rises further in a cylindrical secondary battery, which is a comparative example.

[0009] Referring to Figure 1, an example of an embodiment, a cylindrical secondary battery 10, will be described. Figure 1 is an axial cross-sectional view of the cylindrical secondary battery 10.

[0010] As shown in Figure 1, the cylindrical secondary 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 24 of the outer casing 20 is sealed by a sealing body 30. Hereafter, the side of the cylindrical secondary battery 10 with the sealing body 30 in the axial direction (up and down direction) will be referred to as "up," and the side of the outer casing 20 with the bottom 21 in the axial direction will be referred to as "down."

[0011] The electrode body 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and the positive electrode 11 and the negative electrode 12 are wound in a spiral shape via the separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 are all elongated strips, and are alternately stacked in the radial direction of the electrode body 14 by being wound in a spiral shape. 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 than the positive electrode 11 in both the longitudinal and width (short-side) directions. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and two separators are arranged so as to sandwich the positive electrode 11. The cylindrical secondary battery 10 also includes insulating plates 15 and 16 arranged above and below the electrode body 14, respectively.

[0012] The positive electrode 11 comprises a positive electrode core and a positive electrode mixture layer formed on the positive electrode core. The positive electrode core 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 contains a positive electrode active material, a conductive agent, and a binder, and is preferably formed on both sides of the positive electrode core, excluding the exposed portion of the positive electrode core to which the positive electrode tab 17 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, drying the coating, and then compressing it to form the positive electrode mixture layer on both sides of the positive electrode core.

[0013] The positive electrode composite layer 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 elements constituting the lithium 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 metal composite oxides containing Ni, Co, and Mn, and lithium metal composite oxides containing Ni, Co, and Al.

[0014] Examples of conductive agents included in the positive electrode mixture layer 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 include fluorine-containing resins 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.

[0015] The negative electrode 12 comprises a negative electrode core and a negative electrode mixture layer formed on the negative electrode core. The negative electrode core can be made of a metal foil that is stable within 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 negative electrode mixture layer contains a negative electrode active material, a binder, and optionally a conductive agent, and is preferably formed on both sides of the negative electrode core, excluding the exposed portion of the negative electrode core to which the negative electrode tab 18 is welded. 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, drying the coating, and then compressing it to form the negative electrode mixture layer on both sides of the negative electrode core.

[0016] The negative electrode composite layer generally contains a carbon material that reversibly intercepts and releases lithium ions as the negative electrode active material. Suitable examples of carbon materials include natural graphite such as flake graphite, lumpy graphite, and clay graphite, as well as artificial graphite such as lumpy artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB). In addition, 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 as the negative electrode active material. Among these, composite materials containing Si are preferred.

[0017] 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 a 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 film, is formed on the particle surface of the composite material.

[0018] The binder in the negative electrode mixture layer may be a fluororesin, PAN, polyimide, acrylic resin, polyolefin, etc., similar to the positive electrode mixture layer, but styrene-butadiene rubber (SBR) is preferred. Furthermore, the negative electrode mixture layer preferably contains CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), etc. Among these, a combination of SBR and CMC or a salt thereof, PAA or a salt thereof is preferred. The negative electrode mixture layer may also contain a conductive agent such as CNT.

[0019] 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 polyethylene, polyolefins such as polypropylene, and cellulose. The separator 13 may have a single-layer structure or a multi-layer structure. A 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.

[0020] A positive electrode tab 17 is connected to the positive electrode 11, and a negative electrode tab 18 is connected to the end of the winding of the negative electrode 12. The positive electrode tab 17 extends towards the sealing body 30 through a through hole in the insulating plate 15, and the negative electrode tab 18 extends towards the bottom 21 of the outer can 20 through the outside of the insulating plate 16.

[0021] The non-aqueous electrolyte contained in the outer container 20 is lithium ion conductive. The non-aqueous electrolyte may be a liquid electrolyte (electrolyte solution) or a solid electrolyte.

[0022] 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.

[0023] 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.

[0024] The outer casing 20 is a bottomed cylindrical metal container with an open top. The outer casing 20 has a bottom 21 and side portions 22 that form the sides of the cylindrical secondary battery 10. The side portions 22 are the parts of the outer casing 20 excluding the bottom 21 and include grooved portions 23 and openings 24, which will be described later.

[0025] The grooved portion 23 is a part of the side surface 22 that is recessed radially inward, and is provided in an annular shape along the circumferential direction of the outer can 20. The grooved portion 23 supports the sealing body 30 on its upper surface. The grooved portion 23 can be formed, for example, by spinning a part of the side surface 22 radially inward to create an annular recess toward the radially inward side.

[0026] The width (vertical length) of the grooved portion 23 is not particularly limited, but for example, it is 0.1 mm or more and 2.0 mm or less. The depth (radial length) of the grooved portion 23 is also not particularly limited, but for example, it is 0.5 mm or more and 5.0 mm or less.

[0027] The opening 24 is located in the region of the side portion 22 above the grooved portion 23, and forms the opening of the outer can 20. The opening 24 is bent radially inward when the sealing body 30 is crimped and fixed to the outer can 20. As a result, the opening 24 forms an opening side portion 25 that forms part of the side of the cylindrical secondary battery 10 and covers the outer circumferential surface of the gasket 19, and a crimped portion 26 that forms part of the upper surface of the cylindrical secondary battery 10 and extends radially inward. In this embodiment, the radial inner end of the crimped portion 26 is located radially outward from the radial inner end of the gasket 19. That is, a part of the upper surface of the gasket 19 is not covered by the crimped portion 26. Furthermore, as will be described in more detail later, a cap member 40 is provided on the outer surface of the opening 24, which is joined to the crimped portion 26. The cap member 40 is made of a metal material and is electrically connected to the outer can 20.

[0028] As described above, the sealing body 30 has the function of closing the opening 24 of the outer can 20. In this embodiment, the sealing body 30 includes a sealing plate 31 and a current collector plate 32. The sealing plate 31 and the current collector plate 32 are stacked on the outer periphery and are crimped and fixed to the opening 24 of the outer can 20 via a gasket 19. The configuration of the sealing body 30 is not limited to this, as long as it is capable of closing the opening 24 of the outer can 20.

[0029] The sealing plate 31 is a metal member that is circular in shape when viewed from above. The material of the sealing plate 31 is not particularly limited, but examples of preferred materials include aluminum or an aluminum alloy.

[0030] A protrusion 31A is provided in the center of the sealing plate 31, projecting outwards from the battery. The protrusion 31A has a circular shape when viewed from above. The diameter of the protrusion 31A is not particularly limited, but for example, it is 25% or more and 60% or less of the diameter of the sealing plate 31. The height of the protrusion 31A is not particularly limited, but for example, it is 0.5 mm or more and 5.0 mm or less. The upper surface of the sealing plate 31 may have a flat shape throughout.

[0031] The top surface of the protrusion 31A is exposed and forms the top surface of the cylindrical secondary battery 10. In addition, the area of ​​the upper surface of the sealing plate 31 surrounding the protrusion 31A is covered by an insulating member 50, which will be described later.

[0032] The current collector plate 32 is positioned below the sealing plate 31 and is a circular metal member when viewed from above. The material of the current collector plate 32 is not particularly limited, but a suitable example of a suitable material is aluminum or an aluminum alloy, similar to the sealing plate 31. The current collector plate 32 is joined to the sealing plate 31 at its outer circumference by laser welding or the like, and is electrically connected to the sealing plate 31.

[0033] The current collector plate 32 has a recess that is radially inward from the outer circumference that is joined to the sealing plate 31, and is recessed downward relative to the outer circumference. A through hole is provided in the radial center of the recess, through which the positive electrode tab 17 passes. The positive electrode tab 17 is positioned in the space formed by the recess, and the positive electrode tab 17 is joined to the upper surface of the recess. Note that the cylindrical secondary battery 10 may not have a current collector plate 32, and the positive electrode tab 17 may be joined to the lower surface of the sealing plate 31.

[0034] The cylindrical secondary battery 10 includes a gasket 19 interposed between the outer casing 20 and the sealing body 30. The gasket 19 is a flexible insulating material that electrically isolates the sealing body 30, which is the positive electrode external terminal, from the outer casing 20, which is the negative electrode external terminal, while ensuring airtightness inside the outer casing 20 when compressed. The material of the gasket 19 is not particularly limited as long as it is a compressible insulating material, and for example, polypropylene (PP), polyphenylene sulfide (PPS), polyethylene (PE), polybutylene terephthalate (PBT), perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), polyamide (PA), etc. can be used.

[0035] In this embodiment, the positive electrode tab 17 is joined to the current collector plate 32 by welding or ultrasonic welding, and the sealing plate 31, which is electrically connected to the current collector plate 32, becomes the positive electrode external terminal. The current collector terminal on the positive electrode 11 side is welded, for example, to the top surface of the protrusion 31A of the sealing plate 31. The negative electrode tab 18 is joined to the inner surface of the bottom 21 of the outer can 20 by welding or ultrasonic welding, and the cap member 40, which is electrically connected to the outer can 20, becomes the negative electrode external terminal. It is also possible to electrically connect the negative electrode 12 and the outer can 20 by bringing the negative electrode core into contact with the inner surface of the outer can 20. The current collector terminal on the negative electrode 12 side is welded, for example, to the upper surface of the cap member 40.

[0036] In the cylindrical secondary battery 10, the sealing plate 31 of the sealing body 30, which functions as the positive electrode external terminal, and the cap member 40, which functions as the negative electrode external terminal, are both located on the upper surface. Therefore, when modularizing the cylindrical secondary battery 10, the leads, which serve as current collection terminals, can be connected to the positive or negative electrode external terminal located on the upper surface of the cylindrical secondary battery 10, making it possible to miniaturize the module and improve productivity.

[0037] Next, the cap member 40 and the insulating member 50 will be described in detail with further reference to Figure 2. Figure 2 is an enlarged view of part A in Figure 1.

[0038] As shown in Figures 1 and 2, the cylindrical secondary battery 10 includes a cap member 40 joined to the outer surface of the outer casing 20. The cap member 40 is positioned to cover the opening 24 of the outer casing 20. The cap member 40 is a conductive member to which current collection terminals such as leads are connected when modularizing multiple cylindrical secondary batteries 10 to each other. The material of the cap member 40 is not particularly limited, but for example, it is made of a metal mainly composed of iron.

[0039] The cap member 40 has a top surface portion 41 whose upper surface is exposed and which forms the top surface of the cylindrical secondary battery 10, a groove arrangement portion 42 which is arranged inside the grooved portion 23, and a connecting portion 43 which connects the top surface portion 41 and the groove arrangement portion 42. The cap member 40 is provided around the entire circumference of the outer casing 20.

[0040] The top surface portion 41 covers the outer surface of the crimping portion 26 and extends radially inward. The top surface portion 41 has an annular shape when viewed from above. The lower surface of the top surface portion 41 has a radially outer portion that abuts against the crimping portion 26 and a radially inner portion that abuts against the insulating member 50. The top surface portion 41 extends, for example, substantially parallel to the radial direction. The top surface portion 41 has, for example, a uniform width (radial length) around its entire circumference. The width of the top surface portion 41 is, for example, 10% or more and 40% or less of the outer diameter of the outer can 20.

[0041] The top surface portion 41 has a welded portion 44 that is joined to the crimping portion 26 by welding. The area and shape of the welded portion 44 are set, for example, taking into consideration the joint strength and resistance. Generally, the larger the area of ​​the welded portion 44, the higher the joint strength and the lower the resistance. From the viewpoint of increasing the joint strength between the cap member 40 and the crimping portion 26, it is preferable that the welded portion 44 be formed in a C-shape or a circular shape when viewed from above.

[0042] In this embodiment, the top surface portion 41 has a substantially constant thickness over the radial direction except for the portion where a recess 45 described later is formed. The thickness of the top surface portion 41 is, for example, 0.2 mm or more and 2.0 mm or less. When the thickness of the top surface portion 41 is within the above range, it becomes easier to weld a lead as a current collecting terminal on the negative electrode 12 side to the outer surface of the top surface portion 41. Note that the thickness of the top surface portion 41 may be different in the radial direction. For example, the thickness of the radially outer portion of the top surface portion 41 that abuts on the caulking portion 26 may be larger than the thickness of the radially inner portion that abuts on the insulating member 50.

[0043] As shown in FIG. 2, a recess 45 is provided in the top surface portion 41 in a region radially inner than the welding portion 44. When the internal pressure of the battery rises, such as during abnormal heat generation of the battery, the sealing body 30 (sealing plate 31) may deform convexly toward the outside of the battery. Then, as the sealing body 30 deforms, the top surface portion 41 is also pressed toward the outside of the battery. When the recess 45 is provided in the top surface portion 41, when the top surface portion 41 is pressed toward the outside of the battery as the internal pressure of the battery increases, the region where the recess 45 is provided preferentially bends. Thereby, the stress applied to the region radially outer than the recess 45 of the top surface portion 41 is relaxed, the caulking portion 26 is less likely to come off, and the cap member 40 is less likely to come off from the opening portion 24 of the outer can 20.

[0044] The cross-sectional shape of the recess 45 is not particularly limited. The recess 45 may be, for example, a substantially U-shaped, substantially V-shaped, or substantially semi-circular shape in a cross-sectional view. Also, the bottom surface of the recess 45 may be flat. Also, a plurality of recesses 45 may be provided. The width of the recess 45 is, for example, 0.1 mm or more and 2 mm or less.

[0045] In the examples shown in FIGS. 1 and 2, the recess 45 is provided on the upper surface of the top surface portion 41 (the surface opposite to the surface on the electrode body 14 side). Note that the recess 45 may be provided on the lower surface (the surface on the electrode body 14 side) of the top surface portion 41. When the recess 45 is provided on the lower surface of the top surface portion 41, the upper surface of the top surface portion 41 becomes flat. Therefore, it becomes easy to weld a lead as a current collecting terminal on the negative electrode 12 side to the upper surface of the top surface portion 41. Also, the recess 45 may be provided on both surfaces of the top surface portion 41.

[0046] In a top view of the cylindrical secondary battery 10, the length along the radial direction from the center of the cylindrical secondary battery 10 to the concave portion 45 is preferably 50% or more, and more preferably 70% or more, of the length along the radial direction from the center of the cylindrical secondary battery 10 to the welded portion 44. By forming the concave portion 45 in the vicinity of the welded portion 44, when the top surface portion 41 is deformed starting from the concave portion 45, the stress applied to the region radially outside the concave portion 45 of the top surface portion 41 is more relaxed, the caulked portion 26 is less likely to come off, and the cap member 40 is less likely to come off from the opening portion 24 of the outer can 20.

[0047] The minimum thickness of the top surface portion 41 of the portion where the concave portion 45 is provided is preferably 80% or less, and more preferably 70% or less, of the average thickness of the top surface portion 41 of the portion where the concave portion 45 is not provided. In this case, when the top surface portion 41 is pressed toward the outside of the battery as the battery internal pressure rises, the region where the concave portion 45 is provided can be preferentially bent. Further, the minimum thickness of the top surface portion 41 of the portion where the concave portion 45 is provided is preferably 20% or more, and more preferably 30% or more, of the average thickness of the top surface portion 41 of the portion where the concave portion 45 is not provided. In this case, when the deformation of the sealing body 30 due to the rise in the battery internal pressure is small, the top surface portion 41 can be held without being bent, and the sealing body 30 (sealing plate 31) can be pressed by the top surface portion 41. Therefore, the minimum thickness of the top surface portion 41 of the portion where the concave portion 45 is provided is preferably 20% or more and 80% or less, and more preferably 30% or more and 70% or less, of the average thickness of the top surface portion 41 of the portion where the concave portion 45 is not provided.

[0048] The groove arrangement portion 42 is provided below the connection portion 43 and is arranged inside the groove insertion portion 23. The groove arrangement portion 42 is formed by bending the lower portion of the connection portion 43 toward the inside in the radial direction. The groove arrangement portion 42 may extend substantially parallel to the radial direction, or may extend in a direction inclined by a predetermined angle with respect to the radial direction.

[0049] The grooved portion 42 abuts against the upper surface of the grooved portion 23 and is hooked onto the grooved portion 23. By the grooved portion 42 being hooked onto the grooved portion 23, the cap member 40 can be firmly locked to the opening 24 of the outer casing 20. As a result, even if the internal pressure of the battery rises due to abnormal heat generation of the battery, the deformation of the opening 24 of the outer casing 20 is suppressed by the cap member 40. Consequently, the sealing body 30 is less likely to be released to the outside of the battery, and the scattering of materials from inside the battery to the outside can be suppressed.

[0050] The connecting portion 43 connects the top surface portion 41 and the groove arrangement portion 42. The connecting portion 43 is connected to the radially outer end of the top surface portion 41 and extends along the vertical direction. The connecting portion 43 covers the entire circumference of the opening side portion 25. The thickness of the connecting portion 43 may be the same as or different from the thickness of the top surface portion 41.

[0051] As shown in Figure 2, the cylindrical secondary battery 10 is equipped with an insulating member 50 positioned on the upper surface of the sealing plate 31 to prevent electrical connection between the sealing plate 31 and the cap member 40. The insulating member 50 is a resin member with a circular shape when viewed from above, positioned between the sealing plate 31 and the cap member 40. The material of the insulating member 50 is not particularly limited, and for example, polypropylene (PP), polyphenylene sulfide (PPS), polyethylene (PE), polybutylene terephthalate (PBT), perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), polyamide (PA), etc. can be used.

[0052] The insulating member 50 has an opening 51 in its radial center. The opening 51 has a circular shape when viewed from above and is formed to penetrate the insulating member 50 in the thickness direction. The opening 51 is a hole for passing the protrusion 31A of the sealing plate 31.

[0053] In this embodiment, the insulating member 50 includes a main body portion 52 having a substantially uniform thickness and whose lower surface abuts against the sealing plate 31, a first projection portion 53 protruding from the upper surface of the main body portion 52, and a second projection portion 54 protruding from the radially outer side surface of the main body portion 52.

[0054] The main body portion 52 is formed in a flat, annular shape and has a substantially uniform thickness along the entire circumferential length of the insulating member 50. The upper surface of the main body portion 52 is in contact with the lower surface of the cap member 40, except for the portion where the first protrusion 53 is formed.

[0055] The thickness of the main body portion 52 is, for example, approximately the same as the sum of the thickness of the crimped portion 26 of the outer can 20 and the thickness of the gasket 19. In this case, the top surface portion 41 of the cap member 40 can be extended approximately parallel to the radial direction. As a result, it becomes easier to weld the lead, which serves as the current collection terminal for the negative electrode 12, to the upper surface of the top surface portion 41. The width (radial length) of the main body portion 52 is, for example, the length that covers approximately the entire area around the protrusion 31A of the sealing plate 31, where the upper surface is not covered by the gasket 19.

[0056] The first projection 53 protrudes upward from the radially inner end portion of the upper surface of the main body 52. ​​The convex portion 31A of the sealing plate 31 is positioned radially inside the first projection 53, and the top surface portion 41 of the cap member 40 is positioned radially outside the first projection 53. In other words, the convex portion 31A of the sealing plate 31 and the top surface portion 41 of the cap member 40 are facing each other radially via the first projection 53.

[0057] The height (vertical length) of the first protrusion 53 is, for example, greater than or equal to the thickness of the top surface 41 of the cap member 40. In this case, contact between the convex portion 31A of the sealing plate 31 and the top surface 41 of the cap member 40 can be further suppressed.

[0058] The second projection 54 protrudes radially outward from the upper end of the radially outer side surface of the main body 52. ​​A gasket 19 is placed in the gap formed below the second projection 54. The upper surface of the second projection 54 is in contact with the lower surface of the cap member 40. In other words, the top surface 41 of the cap member 40 and the gasket 19 are facing each other vertically via the second projection 54.

[0059] The shape of the insulating member 50 is not limited to this, as long as it can prevent electrical connection between the sealing plate 31 and the cap member 40. For example, the insulating member 50 may have a recess, and the top surface 41 of the cap member 40 may be sandwiched in the recess.

[0060] Next, the appearance of the opening 24 when the internal pressure of the battery increases will be explained with reference to Figures 3 to 5. Figure 3 is a schematic diagram showing the appearance of the opening 24 when the internal pressure of the battery increases in the cylindrical secondary battery 10 of this embodiment, and Figures 4 and 5 are schematic diagrams showing the appearance of the opening 24 when the internal pressure of the battery increases in a cylindrical secondary battery in which the recess 45 is not provided on the top surface 41.

[0061] As shown in Figure 3, when the battery overheats abnormally and the internal pressure of the battery rises, the sealing body 30 deforms into a convex shape toward the outside of the battery. As the deformation of the sealing body 30 increases, the top surface portion 41 is also pressed against the sealing body 30 and pushed toward the outside of the battery.

[0062] The portion of the top surface 41 where the recess 45 is provided is thinner than other portions and therefore has less strength. As a result, when the top surface 41 is pressed outward due to an increase in the internal pressure of the battery, the top surface 41 bends starting from the region where the recess 45 is provided. This relieves the stress applied to the region radially outward from the recess 45 of the top surface 41, maintaining the state in which the groove arrangement portion 42 is positioned inside the grooved portion 23, and making it difficult for the cap member 40 to come off the opening 24 of the outer can 20. As a result, the shape of the opening 24 of the outer can 20 is maintained, the crimping portion 26 that holds the sealing body 30 in place does not come off, and the sealing plate 31 is not released.

[0063] On the other hand, as shown in Figure 4, in a cylindrical secondary battery in which the top surface 41 does not have a recess 45, when the top surface 41 is pressed outward due to an increase in the internal pressure of the battery, the top surface 41 does not bend, but is pushed outward.

[0064] Therefore, if the internal pressure of the battery rises further, as shown in Figure 5, the grooved portion 42 of the cap member 40 will detach from the grooved portion 23, and the cap member 40 will detach from the opening 24 of the outer casing 20. Also, as described above, the top portion 41 is joined to the crimped portion 26 by welding. Therefore, if the top portion 41 is pushed outwards from the battery, the crimped portion 26 will also be pushed outwards from the battery. As a result, the crimped portion 26 will detach, and the sealing body 30 will be released. When the sealing body 30 is released, for example, materials inside the battery may scatter to the outside, potentially affecting surrounding equipment, etc.

[0065] The above embodiments can be modified without altering the purpose of this disclosure. For example, in the above embodiments, the recess 45 provided on the top surface 41 of the cap member 40 is formed around the entire circumference, but the arrangement of the recess 45 is not limited to this. For example, the recess 45 may be formed in a C-shape when viewed from above. Alternatively, a plurality of recesses 45 may be formed on the top surface 41 of the cap member 40 at intervals in the circumferential direction.

[0066] Furthermore, in the above embodiment, the sealing plate 31 of the sealing body 30 functions as the positive external terminal and the cap member 40 functions as the negative external terminal. However, the sealing plate 31 of the sealing body 30 may function as the negative external terminal and the cap member 40 may function as the positive external terminal. In this case, the positive tab 17 is connected to the outer can 20 and the negative tab 18 is connected to the current collector plate 32.

[0067] The present disclosure will be further described by the following embodiments. Configuration 1: A cylindrical secondary battery comprising an electrode body in which a positive electrode and a negative electrode are wound with a separator between them, a bottomed cylindrical outer can housing the electrode body, a sealing body that closes the opening of the outer can, and a cap member joined to the outer surface of the outer can, wherein the outer can has a grooved portion provided on the side of the outer can and recessed toward the radially inward side of the outer can, and a crimped portion provided at the opening of the outer can and extending toward the radially inward side of the outer can, wherein the cap member covers the outer surface of the crimped portion and extends toward the radially inward side of the outer can and has a top surface portion that forms the top surface of the cylindrical secondary battery, a groove arrangement portion disposed inside the grooved portion, and a connecting portion that connects the top surface portion and the groove arrangement portion, wherein the top surface portion has a welded portion that is welded to the crimped portion, and a recess is provided in the region radially inward from the welded portion. Configuration 2: The cylindrical secondary battery according to Configuration 1, wherein the recess is provided on the electrode body side of the top surface. Configuration 3: The cylindrical secondary battery according to Configuration 1, wherein the recess is provided on both sides of the top surface. Configuration 4: The cylindrical secondary battery according to any one of Configurations 1 to 3, wherein the recess is provided around the entire circumference of the top surface. Configuration 5: The cylindrical secondary battery according to any one of Configurations 1 to 4, wherein, in a top view of the cylindrical secondary battery, the radial length from the center of the cylindrical secondary battery to the recess is 50% or more of the radial length from the center of the cylindrical secondary battery to the welded portion. Configuration 6: The cylindrical secondary battery according to any one of Configurations 1 to 5, wherein the minimum thickness of the top surface in the portion where the recess is provided is 20% or more and 80% or less of the average thickness of the top surface in the portion where the recess is not provided.

[0068] 10 Cylindrical secondary battery (battery), 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15, 16 Insulating plate, 17 Positive electrode tab, 18 Negative electrode tab, 19 Gasket, 20 Outer can, 21 Bottom, 22 Side, 23 Grooved part, 24 Opening, 25 Opening side, 26 Crimped part, 30 Sealing body, 31 Terminal plate, 31A Protrusion, 32 Current collector plate, 40 Cap member, 41 Top surface, 42 Groove arrangement part, 43 Connection part, 44 Welded part, 45 Recess, 50 Insulating member, 51 Opening, 52 Main body, 53 First protrusion, 54 Second protrusion.

Claims

1. A cylindrical secondary battery comprising: an electrode body in which a positive electrode and a negative electrode are wound with a separator between them; a bottomed cylindrical outer can housing the electrode body; a sealing body that closes the opening of the outer can; and a cap member joined to the outer surface of the outer can, wherein the outer can has: a grooved portion provided on the side of the outer can and recessed toward the radially inward side of the outer can; a crimped portion provided at the opening of the outer can and extending toward the radially inward side of the outer can; the cap member having: a top surface portion that covers the outer surface of the crimped portion and extends toward the radially inward side of the outer can and forms the top surface of the cylindrical secondary battery; a groove arrangement portion disposed inside the grooved portion; and a connecting portion that connects the top surface portion and the groove arrangement portion, wherein the top surface portion has a welded portion joined to the crimped portion by welding, and a recess is provided in the region radially inward from the welded portion.

2. The cylindrical secondary battery according to claim 1, wherein the recess is provided on the electrode body side of the top surface.

3. The cylindrical secondary battery according to claim 1, wherein the recesses are provided on both sides of the top surface.

4. The cylindrical secondary battery according to claim 1, wherein the recess is provided around the entire circumference of the top surface.

5. The cylindrical secondary battery according to claim 1, wherein, in a top view of the cylindrical secondary battery, the radial length from the center of the cylindrical secondary battery to the recess is 50% or more of the radial length from the center of the cylindrical secondary battery to the welded portion.

6. The cylindrical secondary battery according to claim 1, wherein the minimum thickness of the top surface of the portion where the recess is provided is 20% or more and 80% or less of the average thickness of the top surface of the portion where the recess is not provided.

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