Cylindrical secondary battery and manufacturing method for cylindrical secondary battery
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD
- Filing Date
- 2026-01-14
- Publication Date
- 2026-07-30
Smart Images
Figure JP2026000855_30072026_PF_FP_ABST
Abstract
Description
Cylindrical secondary battery and method for manufacturing a cylindrical secondary battery
[0001] The present disclosure relates to a cylindrical secondary battery and a method for manufacturing 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. An inwardly bent caulking portion that presses the sealing body via a gasket is formed on the opening edge of the outer can. Cylindrical secondary batteries are characterized by being resistant to impact and easy to modularize, and 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 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 Unexamined Patent Application Publication No. 2006-261083 International Publication No. 2024 / 161945
[0005] The cap member disclosed in Patent Document 2 is fixed to the outer can by arranging the cap member on the outer surface of the outer can and then caulking the end portion of the cap member so that the end portion of the cap member is arranged inside a groove portion formed in the outer can. Therefore, when the cap member disclosed in Patent Document 2 is applied, an additional process of caulking the cap member is required in the battery manufacturing process. In addition, since the width of the groove portion generally formed in the outer can is small, it may be difficult to caulk the cap member.
[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 cylindrical outer can having a bottom and 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. The outer can has a grooved portion on its side surface that is recessed radially inward, an open side portion extending from the grooved portion toward the opposite side of the bottom, and a crimping portion extending radially inward and pressing down on the sealing body. The cap member has a cylindrical tubular portion that forms the outer circumferential surface of the cap member, an extension portion extending radially inward from the tubular portion and covering the crimping portion, and a locking portion extending radially inward from the tubular portion, with at least a portion of which is located inside the grooved portion. The open side portion extends from the grooved portion toward the opposite side of the bottom, along a direction inclined radially outward with respect to the axial direction of the outer can.
[0007] A method for manufacturing a cylindrical secondary battery, according to one aspect of the present disclosure, comprises: a first step of inserting an electrode body into a cylindrical outer casing having a bottom; a second step of forming a groove recessed radially inward on the side surface of the outer casing; a third step of placing a sealing body on the upper surface of the groove and crimping the opening of the outer casing; and a fourth step of pressing an annular cap member from the top side of the cylindrical secondary battery and fitting the cap member into the opening of the outer casing, wherein the cap member has a cylindrical outer periphery that forms the outer circumferential surface of the cap member, and a top surface that extends radially inward from the outer periphery and forms the top surface of the cap member, and the outer periphery is characterized in that, in the state before the cap member is fitted into the opening of the outer casing, the end of the outer periphery on the bottom side of the outer periphery is bent radially inward.
[0008] According to a method for manufacturing a cylindrical secondary battery in one aspect of this disclosure, the cap member can be fixed to the outer casing without crimping the cap member, thus providing a cylindrical secondary battery with excellent productivity.
[0009] 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 how a locking portion is formed on the cap member. This is an axial cross-sectional view of the cap member before it is fitted into the outer casing.
[0010] 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.
[0011] 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."
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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.
[0021] 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 casing 20 through the outside of the insulating plate 16. Note that the current collection configuration of the positive electrode 11 and the negative electrode 12 is not limited to this.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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. 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.
[0026] 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.
[0027] 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.
[0028] The opening 24 is the area 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 has an opening side portion 25 that extends upward from the grooved portion 23 and a crimping portion 26 that extends radially inward and presses down on the sealing body 30. As will be described in more detail later, a cap member 40 is fitted onto 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] Next, with further reference to Figure 2, 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. Figure 2 is an enlarged view of part A in Figure 1.
[0039] As shown in FIGS. 1 and 2, the cylindrical secondary battery 10 includes an annular cap member 40 fitted on the outer surface of an outer can 20. The cap member 40 is disposed so as to cover the opening 24 of the outer can 20. The cap member 40 is, for example, a conductive member to which current collecting terminals such as leads for electrically connecting a plurality of cylindrical secondary batteries 10 to each other are connected when modularizing. The constituent material of the cap member 40 is not particularly limited, and for example, it is made of a metal mainly composed of iron or an alloy containing nickel.
[0040] The cap member 40 has a cylindrical tubular portion 41 forming the outer peripheral surface of the cap member 40, an extending portion 42 extending radially inward from the tubular portion 41 and covering the caulking portion 26, and a locking portion 43 extending radially inward from the tubular portion 41 and at least a part of which is disposed inside the grooved portion 23. The cap member 40 is provided over the entire circumference of the outer can 20.
[0041] The tubular portion 41 covers the outer surface of the opening side surface portion 25 of the outer can 20 over the entire circumference. An extending portion 42 is connected to the upper end of the tubular portion 41, and a locking portion 43 is connected to the lower end of the tubular portion 41. Although details will be described later, the extending portion 42 and the locking portion 43 are already formed before the cap member 40 is fitted into the opening 24 of the outer can 20. The tubular portion 41 has a uniform height (axial length) over the entire circumference.
[0042] The extending portion 42 extends radially inward from the tubular portion 41 and covers the outer surface of the caulking portion 26 over the entire circumference. On the upper surface of the extending portion 42, current collecting terminals such as leads for electrically connecting a plurality of cylindrical secondary batteries 10 to each other are connected when modularizing.
[0043] The extending portion 42 has an annular shape in a top view. The lower surface of the extending portion 42 has a radially outer portion abutting against the caulking portion 26 and a radially inner portion abutting against an insulating member 50 described later. The extending portion 42 extends, for example, substantially parallel to the radial direction. The extending portion 42 has, for example, a uniform width (radial length) over the entire circumference. The width of the extending portion 42 is, for example, 10% or more and 40% or less of the outer diameter of the outer can 20.
[0044] The extending portion 42 has a welded portion (not shown) that is joined to the caulking portion 26 by welding. The area and shape of the welded portion are set in consideration of, for example, the joining strength and resistance. Generally, as the area of the welded portion increases, the joining strength increases and the resistance decreases. From the viewpoint of increasing the joining strength between the cap member 40 and the caulking portion 26, the welded portion is preferably formed in a C shape or a circular shape in a top view.
[0045] In the present embodiment, the extending portion 42 has a substantially constant thickness in the radial direction. The thickness of the extending portion 42 is, for example, 0.2 mm or more and 2.0 mm or less. When the thickness of the extending portion 42 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 extending portion 42. Note that the thickness of the extending portion 42 may vary in the radial direction. For example, the thickness of the radially outer portion of the extending portion 42 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.
[0046] The locking portion 43 extends radially inward from the cylindrical portion 41, and when the cap member 40 is fitted into the opening 24 of the outer can 20, at least a part of it is disposed inside the groove portion 23. The locking portion 43 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.
[0047] The locking portion 43 abuts on the upper surface of the groove portion 23 and is hooked on the groove portion 23. By the locking portion 43 being hooked on the groove portion 23, the cap member 40 can be firmly locked to the opening 24 of the outer can 20. Thereby, even when the internal pressure of the battery rises during abnormal heat generation of the battery or the like, it is possible to prevent the cap member 40 from coming off from the opening 24 of the outer can 20.
[0048] The length of the locking portion 43 can be appropriately set according to the shape of the groove portion 23 and the like, and is, for example, 5% or more and 20% or less of the length of the cylindrical portion 41. In this case, it becomes easier for the locking portion 43 to be hooked on the groove portion 23.
[0049] Furthermore, the thickness of the locking portion 43 may be the same as the thickness of the cylindrical portion 41. In this case, the locking portion 43 will be more easily caught by the grooved portion 23. The thickness of the cylindrical portion 41 and the locking portion 43 is, for example, 0.2 mm or more and 2.0 mm or less.
[0050] As described above, the locking portion 43 is already formed before the cap member 40 is fitted into the opening 24 of the outer can 20. Therefore, there is no need to perform a crimping process after positioning the cap member 40, as described in Patent Document 2 (International Publication No. 2024 / 161945), and the thickness of the locking portion 43 can be made the same as the thickness of the cylindrical portion 41. In other words, if the crimping process is performed after positioning the cap member 40 to form the locking portion 43, as described in Patent Document 2, the locking portion 43 will be pressed, and the thickness of the locking portion 43 will be smaller than the thickness of the cylindrical 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, and a protruding portion 53 that protrudes from the upper 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 extension portion 42 of the cap member 40, except for the portion where the protrusion portion 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 extension portion 42 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 extension portion 42. 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 protrusion 53 extends upward from the radially inner end of the upper surface of the main body 52. The convex portion 31A of the sealing plate 31 is positioned radially inside the protrusion 53, and the extended portion 42 of the cap member 40 is positioned radially outside the protrusion 53. In other words, the convex portion 31A of the sealing plate 31 and the extended portion 42 of the cap member 40 are radially opposite each other via the protrusion 53.
[0057] The height (vertical length) of the protrusion 53 is, for example, greater than or equal to the thickness of the extension 42 of the cap member 40. In this case, contact between the convex portion 31A of the sealing plate 31 and the extension 42 of the cap member 40 can be further suppressed.
[0058] 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 in which the extension 42 of the cap member 40 is sandwiched.
[0059] As shown in Figure 2, the open side portion 25 of the outer casing 20 in this embodiment extends upward from the grooved portion 23 along a direction inclined radially outward with respect to the axial direction. This makes it easy to fit the cap member 40 into the opening 24 of the outer casing 20 when the cap member 40 is pressed from the top side. Furthermore, after the cap member 40 is fitted, it becomes less likely to come off the opening 24 of the outer casing 20, improving the reliability of the battery.
[0060] The inclination angle of the opening side portion 25 of the outer can 20 with respect to the axial direction is, for example, 1° or more and 30° or less, and may be 3° or more and 20° or less.
[0061] Furthermore, in this embodiment, the crimped portion 26 of the outer can 20 extends radially inward along a direction inclined downward with respect to the radial direction. The inclination angle of the crimped portion 26 of the outer can 20 with respect to the radial direction is, for example, 1° or more and 20° or less, and may be 3° or more and 15° or less. The crimped portion 26 of the outer can 20 may also extend along the radial direction.
[0062] As described above, the opening side portion 25 of the outer can 20 is inclined with respect to the axial direction. Therefore, the cylindrical portion 41 of the cap member 40 that covers the opening side portion 25 is also inclined with respect to the axial direction. In other words, the cylindrical portion 41 of the cap member 40 is positioned radially outward as it moves upward.
[0063] In this case, in an axial cross-sectional view of the cylindrical secondary battery 10, it is preferable that the radial outer end 41X of the cylindrical portion 41 is positioned to axially overlap with the outer surface of the side portion 22 of the outer casing 20, specifically the area below the grooved portion 23. This prevents an increase in battery size (radial length), thus enabling miniaturization of the battery module containing multiple cylindrical secondary batteries 10.
[0064] Next, the manufacturing method of the cylindrical secondary battery 10 of this embodiment will be described with reference to Figures 3 and 4. Figure 3 is a schematic diagram showing how the locking portion 43 is formed on the cap member 40, and Figure 4 is an axial cross-sectional view of the state before the cap member 40 is fitted into the opening 24 of the outer casing 20, showing the vicinity of the opening 24.
[0065] The manufacturing method for the cylindrical secondary battery 10 of this embodiment includes a first step of inserting an electrode body 14 into an outer casing 20; a second step of forming a grooved portion 23 in the side portion 22 of the outer casing 20; a third step of placing a sealing body 30 on the upper surface of the grooved portion 23 and crimping the opening 24 of the outer casing 20; and a fourth step of pressing a cap member 40 from the top side and fitting it into the opening 24 of the outer casing 20.
[0066] In other words, the manufacturing method of the cylindrical secondary battery 10 in this embodiment differs from the manufacturing method described in the aforementioned Patent Document 2 (International Publication No. 2024 / 161945) in that it does not require crimping the cap member 40 after it has been placed in the opening 24 of the outer casing 20. This simplifies the manufacturing process and improves productivity, while also preventing damage to the battery during crimping and improving the reliability of the battery. Furthermore, since the width of the grooved portion 23 is generally small, a crimping jig with a thin tip that can be inserted into the grooved portion 23 was required when crimping the cap member 40. However, the tip of such a crimping jig tended to be easily damaged during the crimping process. In the manufacturing method of this embodiment, since the crimping process of the cap member 40 is unnecessary, such a jig is also unnecessary.
[0067] In the first step, the electrode body 14 is inserted into the outer container 20. At this time, for example, the electrode body 14 is inserted with the sealing body 30 connected via the positive electrode tab 17. Alternatively, the electrode body 14 and the sealing body 30 may be connected via the positive electrode tab 17 after the electrode body 14 has been inserted into the outer container 20.
[0068] In the second step, a groove 23 is formed on the opening side of the outer can 20 by spinning from the radially outer side to support the sealing body 30. After that, a non-aqueous electrolyte (electrolyte solution) is poured into the inside of the outer can 20.
[0069] In the third step, the sealing body 30 is inserted into the outer can 20, and the sealing plate 31 is placed on the upper surface of the grooved portion 23 via the gasket 19. Then, the open end of the outer can 20 is bent radially inward, and the opening 24 of the outer can 20 is crimped. As a result, the sealing body 30 is crimped and fixed to the opening 24 of the outer can 20 via the gasket 19.
[0070] In the third step, the opening 24 of the outer can 20 is crimped so that the opening side portion 25 of the outer can 20 is inclined with respect to the axial direction. This makes it easier to fit the cap member 40 into the opening 24 of the outer can 20 when the cap member 40 is pressed from the top side. In addition, after the cap member 40 is fitted, it becomes less likely to come off the opening 24 of the outer can 20, improving the reliability of the battery.
[0071] In the fourth step, as shown in Figure 4, the cap member 40 is pressed from the top side and fitted into the opening 24 of the outer can 20. Before fitting the cap member 40, as shown in Figure 3, the lower end of the cylindrical portion 41 of the cap member 40 is bent radially inward to form a locking portion 43. In other words, the cap member 40 has a cylindrical portion 41, an extended portion 42, and a locking portion 43 in the state before being fitted into the opening 24 of the outer can 20. The method for bending the cylindrical portion 41 radially inward to create the locking portion 43 is not particularly limited and can be, for example, press working, rolling, and spinning.
[0072] When the lower end of the cylindrical portion 41 is bent radially inward to form the locking portion 43, the length of the locking portion 43 may be 5% or more and 20% or less of the length of the cylindrical portion 41. In this case, when the cap member 40 is fitted into the opening 24 of the outer can 20, the cap member 40 will be less likely to come off the opening 24 of the outer can 20.
[0073] Here, as shown in Figure 4, when the cap member 40 is not fitted, it is preferable that θ1 < θ2 when the angle between the cylindrical portion 41 and the extended portion 42 of the cap member 40 is θ1, and the angle between the opening side portion 25 and the crimping portion 26 of the outer can 20 is θ2. In this case, when the cap member 40 is fitted from the top side, the extended portion 42 of the cap member 40 bends upward, and the opening 24 of the outer can 20 and the cap member 40 are fixed in an interference fit. This allows the cap member 40 to be firmly locked into the opening 24 of the outer can 20.
[0074] θ1 only needs to be smaller than θ2, for example, an angle that is 3° or more and 10° or less smaller than θ2. In this case, the cap member 40 can be firmly locked by the opening 24 of the outer can 20. θ2 is, for example, 60° or more and 90° or less.
[0075] After fitting the cap member 40 into the opening 24 of the outer can 20, the extended portion 42 of the cap member 40 and the crimped portion 26 of the outer can 20 are joined by laser welding or the like. From the viewpoint of increasing the joint strength between the cap member 40 and the crimped portion 26, it is preferable that the welded portion is formed in a C-shape or a circular shape when viewed from above.
[0076] This disclosure is further illustrated 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 cylindrical outer can having a bottom and 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 on its side surface that is recessed radially inward, an open side portion extending from the grooved portion toward the opposite side of the bottom, and a crimping portion extending radially inward and pressing down on the sealing body, wherein the cap member has a cylindrical tubular portion that forms the outer circumferential surface of the cap member, an extension portion extending radially inward from the tubular portion and covering the crimping portion, and a locking portion extending radially inward from the tubular portion and at least a part of which is disposed inside the grooved portion, wherein the open side portion extends radially outward with respect to the axial direction of the outer can, toward the opposite side of the bottom from the grooved portion. Configuration 2: The cylindrical secondary battery according to Configuration 1, wherein, in an axial cross-sectional view of the cylindrical secondary battery, the radial outer end of the cylindrical portion is positioned to overlap axially with the outer surface of the side surface of the outer casing, in the region below the grooved portion. Configuration 3: The cylindrical secondary battery according to Configuration 1 or 2, wherein the length of the locking portion is 5% or more and 20% or less of the length of the cylindrical portion. Configuration 4: The cylindrical secondary battery according to any one of Configurations 1 to 3, wherein the thickness of the locking portion is the same as the thickness of the cylindrical portion.Configuration 5: A method for manufacturing a cylindrical secondary battery, comprising: a first step of inserting an electrode body into a cylindrical outer can having a bottom; a second step of forming a groove recessed radially inward on the side surface of the outer can; a third step of placing a sealing body on the upper surface of the groove and crimping the opening of the outer can; and a fourth step of pressing an annular cap member from the top side of the cylindrical secondary battery and fitting the cap member into the opening of the outer can, wherein the cap member comprises: a cylindrical tubular portion that forms the outer circumferential surface of the cap member; an extension portion that extends radially inward from the tubular portion and forms the top 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 positioned inside the groove when the cap member is fitted into the opening of the outer can. Configuration 6: The method for manufacturing a cylindrical secondary battery according to Configuration 5, wherein the outer can has an open side portion extending from the grooved portion toward the opposite side of the bottom portion, and a crimping portion extending radially inward and pressing down on the sealing body, and in the state before the cap member is fitted into the opening of the outer can, when the angle between the cylindrical portion and the extended portion is θ1 and the angle between the open side portion and the crimping portion is θ2, θ1 < θ2.
[0077] 10 Cylindrical secondary 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 section, 24 Opening, 25 Opening side section, 26 Crimped section, 30 Sealing body, 31 Sealing plate, 31A Protrusion, 32 Current collector plate, 40 Cap member, 41 Cylindrical section, 41X Radial outer end, 42 Extension, 43 Locking section, 50 Insulating member, 51 Opening, 52 Main body, 53 Protruding section
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 cylindrical outer can having a bottom and 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 on its side surface that is recessed radially inward; an open side portion extending from the grooved portion toward the opposite side of the bottom; and a crimping portion extending radially inward and pressing down on the sealing body, wherein the cap member has a cylindrical tubular portion that forms the outer circumferential surface of the cap member; an extension portion extending radially inward from the tubular portion and covering the crimping portion; and a locking portion extending radially inward from the tubular portion, with at least a part of it positioned inside the grooved portion, wherein the open side portion extends radially outward with respect to the axial direction of the outer can, toward the opposite side of the bottom from the grooved portion.
2. In an axial cross-sectional view of the cylindrical secondary battery, the radial outer end of the cylindrical portion is positioned to overlap in the axial direction with the outer surface of the side surface of the outer casing, in the region below the grooved portion, as described in claim 1.
3. The cylindrical secondary battery according to claim 1, wherein the length of the locking portion is 5% or more and 20% or less of the length of the cylindrical portion.
4. The cylindrical secondary battery according to claim 1, wherein the thickness of the locking portion is the same as the thickness of the cylindrical portion.
5. A method for manufacturing a cylindrical secondary battery, comprising: a first step of inserting an electrode body into a cylindrical outer casing having a bottom; a second step of forming a groove recessed radially inward on the side surface of the outer casing; a third step of placing a sealing body on the upper surface of the groove and crimping the opening of the outer casing; and a fourth step of pressing an annular cap member from the top side of the cylindrical secondary battery and fitting the cap member into the opening of the outer casing, wherein the cap member comprises: a cylindrical tubular portion that forms the outer circumferential surface of the cap member; an extension portion that extends radially inward from the tubular portion and forms the top 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 positioned inside the groove when the cap member is fitted into the opening of the outer casing.
6. The method for manufacturing a cylindrical secondary battery according to claim 5, wherein the outer casing has an open side portion extending from the grooved portion toward the opposite side of the bottom portion, and a crimping portion extending radially inward and pressing down on the sealing body, and in the state before the cap member is fitted into the opening of the outer casing, when the angle between the cylindrical portion and the extended portion is θ1 and the angle between the open side portion and the crimping portion is θ2, θ1 < θ2.