Cylindrical secondary battery

Abstract

The present invention is characterized by comprising an electrode assembly (14), a non-aqueous electrolyte, a bottomed cylindrical exterior can (20) that accommodates the electrode assembly (14) and the non-aqueous electrolyte, and a cap member (40) that is joined to the outer surface of the exterior can (20). The present invention is also characterized in that: the exterior can (20) has a crimping part (26) that extends radially inward; the cap member (40) has an annular top surface portion (41) covering the outer surface of the crimping part (26), extending radially inward of the exterior can (20), and forming the top surface of a cylindrical secondary battery (10); and the top surface portion (41) has a through hole (44) in a region radially inward of a radially inner end (26A) of the crimping part (26).

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 non-aqueous electrolyte, a bottomed cylindrical outer can that houses the electrode body, and a sealing body that closes the opening of the outer can. The outer can has a caulking portion where the opening edge is bent inward to press the sealing body via a gasket. The cylindrical secondary battery is characterized by being resistant to impact 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 the negative electrode side current collecting terminal 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] By the way, it is assumed that the non-aqueous electrolyte inside the battery leaks out from the caulking portion due to an abnormal internal pressure of the battery or the like. In the battery using the cap member disclosed in Patent Document 2, when the non-aqueous electrolyte leaks out, the non-aqueous electrolyte may stay inside the cap member, and the outer can and the cap member may corrode. When the outer can and the cap member corrode, an unintentional conduction path or the like may occur, and there is a possibility of an internal short circuit.

[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 non-aqueous electrolyte, a bottomed cylindrical outer casing containing the electrode body and the non-aqueous electrolyte, 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 crimped portion provided at the opening of the outer casing and extending radially inward from the outer casing, and the cap member covers the outer surface of the crimped portion and has an annular top portion that extends radially inward from the outer casing and forms the top surface of the cylindrical secondary battery, and the top portion has a through hole in a region radially inward from the radially inward end of the crimped portion.

[0007] According to one embodiment of the present disclosure, a cylindrical secondary battery can suppress corrosion of the outer casing and cap components due to leakage of non-aqueous electrolyte. As a result, the occurrence of internal short circuits is suppressed, and a highly reliable cylindrical secondary battery can be provided.

[0008] This is an axial cross-sectional view of a cylindrical secondary battery, which is one example of an embodiment. This is an enlarged view of part A in Figure 1. This is a top view of the cap member of a cylindrical secondary battery, which is one example of an embodiment. This is a top view of the cap member of a cylindrical secondary battery, which is another example of an embodiment. This is a top view of the cap member of a cylindrical secondary battery, which is another example of an embodiment.

[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. In this specification, the side of the cylindrical secondary battery 10 with the sealing body 30 in the axial direction (up and down direction) is referred to as "up," and the side of the outer casing 20 with the bottom 21 in the axial direction is 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 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 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 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 LiPF ６ Lithium salts such as these are used.

[0022] The outer casing 20 is a bottomed cylindrical metal container with an open top. Examples of metal materials that make up the outer casing 20 include iron, carbon steel, stainless steel, aluminum, aluminum alloy, and nickel alloy. The outer casing 20 has a bottom portion 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 portion 21 and include grooved portions 23 and openings 24, which will be described later.

[0023] 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.

[0024] 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.

[0025] The opening 24 is 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 is formed with an opening side portion 25 extending upward from the grooved portion 23 and a crimped portion 26 extending radially inward. In this embodiment, the radial inner end 26A of the crimped portion 26 (see Figure 2) 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. The cap member 40 is made of a metal material and is electrically connected to the outer can 20.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] Next, the configuration of the cap member 40, the insulating member 50, and the opening 24 of the outer can 20 will be described in detail with reference to Figures 2 and 3. Figure 2 is an enlarged view of part A in Figure 1, and Figure 3 is a top view of the cap member 40.

[0036] As shown in Figure 2, the cylindrical secondary battery 10 includes an annular 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 and can be made of, for example, a metal mainly composed of iron or an alloy containing nickel.

[0037] The cap member 40 has an annular top portion 41 that forms the top surface of the cylindrical secondary battery 10, a cylindrical tubular portion 42 that forms the outer circumferential surface of the cap member 40, and a locking portion 43 in which at least a part is located inside the grooved portion 23. The cap member 40 is provided around the entire circumference of the outer casing 20.

[0038] The top surface portion 41 covers the outer surface of the crimping portion 26 and extends radially inward, having an annular shape when viewed from above. Current collection terminals such as leads, which electrically connect multiple cylindrical secondary batteries 10 to each other when modularizing, are connected to the top surface of the top surface portion 41. 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.

[0039] The top surface portion 41 has a uniform width (radial length) around its entire circumference. The width (L1) 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.

[0040] The top surface portion 41 has a welded portion (not shown) that is joined to the crimping portion 26 by welding. The area and shape of the welded portion are set, for example, taking into consideration the joint strength and resistance. Generally, the larger the area of ​​the welded portion, 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 is formed in a C-shape or a circular shape when viewed from above.

[0041] In this embodiment, the top surface portion 41 has a substantially constant thickness in the radial direction. 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 the lead, which serves as the current collection 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 differ in the radial direction. For example, the thickness of the radially outer portion of the top surface portion 41 that abuts the crimping portion 26 may be greater than the thickness of the radially inner portion that abuts the insulating member 50.

[0042] Here, as shown in Figure 2, the top surface portion 41 has a through hole 44 extending circumferentially in a region radially inward from the radially inner end 26A of the crimped portion 26. In a cylindrical secondary battery 10, it is assumed that the non-aqueous electrolyte inside the battery may leak out from between the crimped portion 26 and the gasket 19, or from between the gasket 19 and the sealing plate 31, due to abnormal internal pressure of the battery, etc. By providing a through hole 44 in the top surface portion 41, the leaked non-aqueous electrolyte does not remain inside the cap member 40 but volatilizes. As a result, corrosion of the outer casing 20 and the cap member 40 by the non-aqueous electrolyte can be suppressed. In other words, if the top surface portion 41 does not have a through hole 44, the non-aqueous electrolyte may remain inside the cap member 40, causing corrosion of the outer casing 20 and the cap member 40. If the outer casing 20 and the cap member 40 corrode, unintended conductive paths may be created, potentially causing an internal short circuit.

[0043] The through-hole 44 is preferably provided at a position overlapping with the gap 60 between the caulking portion 26 and the insulating member 50 in a plan view. In this case, the retention of the non-aqueous electrolyte leaked from the inside of the battery can be further suppressed, and the exterior can 20 and the cap member 40 are less likely to be corroded. Note that a part of the through-hole 44 may be provided in a region radially outside the radially inner end 26A of the caulking portion 26.

[0044] The width (L2) of the through-hole 44 is preferably 2% or more, and more preferably 5% or more, of the width (L1) of the top surface portion 41. When the width (L2) of the through-hole 44 is 2% or more of the width (L1) of the top surface portion 41, the retention of the non-aqueous electrolyte leaked from the inside of the battery can be further suppressed, and the exterior can 20 and the cap member 40 are less likely to be corroded.

[0045] Further, the width (L2) of the through-hole 44 is preferably 25% or less, and more preferably 20% or less, of the width (L1) of the top surface portion 41. When the width (L2) of the through-hole 44 is 25% or less of the width (L1) of the top surface portion 41, it becomes easier to connect the current collector terminal to the upper surface of the top surface portion 41, and it becomes easier to ensure the strength of the cap member 40. As a result, when a load is applied to the cap member 40 due to an abnormal internal pressure of the battery or the like, the deformation of the cap member 40 is suppressed, and the cap member 40 is less likely to come off from the exterior can 20. Therefore, the width (L) of the through-hole 44 is preferably 2% or more and 25% or less, and more preferably 5% or more and 20% or less, of the width (L1) of the top surface portion 41. Further, the width (L2) of the through-hole 44 is preferably 2% or more and 25% or less, and more preferably 5% or more and 20% or less, of the radius of the top surface portion 41.

[0046] Of the top surface portion 41, the width (L3) of the region radially inside the through hole 44 (hereinafter referred to as "inner region 41A") is preferably 30% or more of the width (L1) of the top surface portion 41. On the upper surface of the inner region 41A of the top surface portion 41, current collecting terminals such as leads are connected. Therefore, by setting the width (L3) of the inner region 41A to 30% or more of the width (L1) of the top surface portion 41, an area for connecting the current collecting terminals can be secured, and the connection of the current collecting terminals becomes easier. Also, the diameter of the inner region 41A is preferably 30% or more of the diameter of the top surface portion 41, and more preferably 35% or more.

[0047] As shown in FIG. 3, in the present embodiment, eight through holes 44 extending along the circumferential direction are provided in the top surface portion 41. Each through hole 44 has the same shape. Each through hole 44 is arranged at substantially equal angular intervals with an interval along the circumferential direction of the top surface portion 41.

[0048] The through holes 44 are preferably arranged in a range of 50% or more of the entire circumference of the top surface portion 41, and more preferably in a range of 60% or more of the entire circumference of the top surface portion 41. When the through holes 44 are arranged in a range of 50% or more of the entire circumference of the top surface portion 41, the retention of the non-aqueous electrolyte leaked from inside the battery can be further suppressed, and the exterior can 20 and the cap member 40 are less likely to corrode.

[0049] Also, the through holes 44 are preferably arranged in a range of 98% or less of the entire circumference of the top surface portion 41, and more preferably in a range of 95% or less of the entire circumference of the top surface portion 41. When the through holes 44 are arranged in a range of 98% or less of the entire circumference of the top surface portion 41, it becomes easier to ensure the strength of the cap member 40. As a result, when a load is applied to the cap member 40 due to an abnormal internal pressure of the battery or the like, deformation of the cap member 40 is suppressed, and the cap member 40 is less likely to come off from the exterior can 20. Therefore, the through holes 44 are preferably arranged in a range of 50% or more and 98%or less of the entire circumference of the top surface portion 41, and more preferably in a range of 60% or more and 95% or less of the entire circumference of the top surface portion 41.

[0050] As shown in Figure 2, the cap member 40 of this embodiment has a top surface portion 41, a cylindrical portion 42, and a locking portion 43. The cylindrical portion 42 covers the entire circumference of the opening side portion 25 of the outer can 20. The top surface portion 41 is connected to the upper end of the cylindrical portion 42, and the locking portion 43 is connected to the lower end of the cylindrical portion 42.

[0051] The locking portion 43 extends radially inward from the cylindrical portion 42, and at least a part of it is positioned inside the grooved portion 23 when the cap member 40 is fitted into the opening 24 of the outer can 20. The locking portion 43 may extend substantially parallel to the radial direction, or it may extend in a direction inclined by a predetermined angle with respect to the radial direction.

[0052] The locking portion 43 abuts against the upper surface of the grooved portion 23 and hooks onto the grooved portion 23. By the locking portion 43 hooking onto the grooved portion 23, the cap member 40 can be firmly locked to the opening 24 of the outer casing 20. This prevents the cap member 40 from coming off the opening 24 of the outer casing 20 even when the internal pressure of the battery rises due to abnormal overheating of the battery, etc.

[0053] The length of the locking portion 43 can be appropriately set depending on the shape of the grooved portion 23, for example, it can be 5% or more and 50% or less of the length of the cylindrical portion 42. In this case, the locking portion 43 will be more likely to catch on the grooved portion 23.

[0054] Furthermore, the thickness of the locking portion 43 may be approximately the same as the thickness of the cylindrical portion 42. In this case, the locking portion 43 will be more easily caught by the grooved portion 23. The thickness of the cylindrical portion 42, including the locking portion 43, is, for example, 0.2 mm or more and 2.0 mm or less.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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. In this embodiment, the main body portion 52 is positioned radially inward of the gasket 19 with a gap between them. 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] The second projection 54 protrudes radially outward from the upper end of the radially outer side surface of the main body 52. ​​In this embodiment, the second projection 54 is positioned radially inward of the crimping portion 26 with a gap 60 between them. As described above, a through hole 44 is provided at a position that overlaps the gap 60 in the vertical direction. The width (radial length) of the gap 60 is, for example, 0.1 mm or more and 1 mm or less. Alternatively, the gap 60 may be omitted, and the second projection 54 may be brought into contact with the radially inner end 26A of the crimping portion 26.

[0063] 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 does not have to have at least one of the first protrusion 53 and the second protrusion 54. Alternatively, the insulating member 50 may have a recess in which the top surface 41 of the cap member 40 is sandwiched.

[0064] Next, a modified example of the cap member 40 will be described with reference to Figures 4 and 5. Figures 4 and 5 are top views of the modified cap member 40, and are corresponding to Figure 3.

[0065] In the example shown in Figure 4, the top surface 41 is provided with four arc-shaped through holes 44 that extend along the circumferential direction. Each through hole 44 is arranged at approximately 90° intervals along the circumferential direction of the top surface 41.

[0066] Furthermore, in the example shown in Figure 5, the top surface 41 is provided with two semicircular through holes 44 that extend along the circumferential direction. As shown in Figures 4 and 5, by increasing the circumferential length of the through holes 44 and increasing the area on the top surface 41 where the through holes 44 are provided, the accumulation of non-aqueous electrolyte leaking from inside the battery can be further suppressed, and the outer casing 20 and cap member 40 become less susceptible to corrosion.

[0067] The above embodiments can be modified within the scope of the purposes of this disclosure. For example, in the above embodiments, the cap member 40 has a top surface portion 41, a cylindrical portion 42, and a locking portion 43, but the cap member 40 may have only a top surface portion 41. When the cap member 40 has a cylindrical portion 42 and a locking portion 43, it is possible to prevent the cap member 40 from coming off the opening 24 of the outer casing 20 even when the internal pressure of the battery rises due to abnormal heat generation of the battery. As a result, a cylindrical secondary battery 10 with greater reliability can be provided.

[0068] 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 non-aqueous electrolyte, a bottomed cylindrical outer can containing the electrode body and the non-aqueous electrolyte, 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 crimped portion provided at the opening of the outer can and extending radially inward of the outer can, and the cap member covers the outer surface of the crimped portion and has an annular top portion that extends radially inward of the outer can and forms the top surface of the cylindrical secondary battery, and the top portion has a through hole in a region radially inward from the radially inward end of the crimped portion. Configuration 2: The cylindrical secondary battery according to Configuration 1, wherein the outer casing has a grooved portion provided on the side surface of the outer casing and recessed radially inward of the outer casing, and the cap member has a cylindrical tubular portion that forms the outer circumferential surface of the cap member, and a locking portion that extends radially inward from the tubular portion and at least a part of which is disposed inside the grooved portion. Configuration 3: The cylindrical secondary battery according to Configuration 1 or 2, wherein an insulating member is provided between the top surface and the sealing body, the insulating member is arranged with a gap radially inward of the crimping portion, and in a plan view of the top surface, the through hole is provided at a position that overlaps with the gap. Configuration 4: The cylindrical secondary battery according to any one of Configurations 1 to 3, wherein the top surface has a plurality of through holes, and the plurality of through holes are arranged at intervals along the circumferential direction of the top surface. Configuration 5: A cylindrical secondary battery according to any one of Configurations 1 to 4, wherein the through-hole extends along the circumferential direction of the top surface, and the width of the through-hole is 2% or more and 25% or less of the radius of the top surface. Configuration 6: A cylindrical secondary battery according to any one of Configurations 1 to 5, wherein the through-hole is located in a range of 50% or more and 98% or less of the entire circumference of the top surface. Configuration 7: A cylindrical secondary battery according to any one of Configurations 1 to 6, wherein the diameter of the region of the top surface radially inward from the through-hole is 30% or more of the diameter of the top surface.

[0069] 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, 26A Radial inner end, 30 Sealing body, 31 Terminal plate, 31A Protrusion, 32 Current collector plate, 40 Cap member, 41 Top surface, 41A Inner region, 42 Cylindrical part, 43 Locking part, 44 Through hole, 50 Insulating member, 51 Opening, 52 Main body, 53 First protrusion, 54 Second protrusion, 60 Gap

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 non-aqueous electrolyte; a bottomed cylindrical outer container housing the electrode body and the non-aqueous electrolyte; a sealing body that closes the opening of the outer container; and a cap member joined to the outer surface of the outer container, wherein the outer container has a crimped portion provided at the opening of the outer container and extending radially inward from the outer container; the cap member covers the outer surface of the crimped portion and has an annular top portion that extends radially inward from the outer container and forms the top surface of the cylindrical secondary battery; and the top portion has a through hole in a region radially inward from the radially inward end of the crimped portion.

2. The cylindrical secondary battery according to claim 1, wherein the outer casing has a grooved portion provided on the side surface of the outer casing and recessed toward the radially inward side of the outer casing, and the cap member has a cylindrical tubular portion that forms the outer circumferential surface of the cap member, and a locking portion that extends radially inward from the tubular portion and at least a portion of which is disposed inside the grooved portion.

3. An insulating member is provided between the top surface and the sealing body, the insulating member is positioned with a gap between it and the radially inward side of the crimped portion, and in a plan view of the top surface, the through hole is positioned to overlap with the gap, as described in claim 1.

4. The cylindrical secondary battery according to claim 1, wherein the top surface has a plurality of through holes, and the plurality of through holes are spaced apart along the circumferential direction of the top surface.

5. The cylindrical secondary battery according to claim 1, wherein the through hole extends along the circumferential direction of the top surface, and the width of the through hole is 2% or more and 25% or less of the radius of the top surface.

6. The cylindrical secondary battery according to claim 1, wherein the through holes are arranged in a range of 50% to 98% of the entire circumference of the top surface.

7. The cylindrical secondary battery according to claim 1, wherein the diameter of the region of the top surface that is radially inward from the through hole is 30% or more of the diameter of the top surface.

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