Sealed battery
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Filing Date
- 2026-04-22
- Publication Date
- 2026-07-29
AI Technical Summary
During the manufacturing process of sealing battery, when the sealing body is fixed to the end of the outer can by the sealing gasket, wrinkles are prone to appear at the end of the sealing gasket, resulting in significant deformation in the axial direction of the protruding part of the sealing gasket, which in turn causes welding defects and dimensional detection errors.
A series of -notch (grooves) surrounding the entire circumference are formed on the gasket of the sealing cell, the axial thickness of these grooves is smaller than the thickness of adjacent areas of the gasket, and such a structure is formed on the projecting portion of the gasket to reduce axial deformation.
By forming the -notch structure, the deformation of the gasket protrusion in the axial direction is reduced, contact with the battery can shoulder and the welding test rod is avoided, and welding defects and dimensional detection errors are prevented.
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Abstract
Description
sealed battery
[0001] The present disclosure relates to a sealed battery, and in particular to suppressing defects that may occur when wrinkles form at the end of a gasket in a configuration in which a sealing body is crimped and fixed to the end of an outer can via a gasket.
[0002] A sealed battery having a configuration including an electrode assembly, a cylindrical outer can with a bottom that houses the electrode assembly, and a sealing body that closes the opening of the outer can has been known. Patent Document 1 describes a sealed battery in which the sealing body is crimped and fixed to the end of the outer can via an insulating resin gasket.
[0003] Japanese Patent Application Laid-Open No. 2008-204839
[0004] In a configuration in which a sealing body is crimped to the end of an outer can via a gasket, as described in Patent Document 1, during battery manufacturing, a gasket having a cylindrical portion extending in the axial direction along the inner peripheral shape of the open end of the outer can before crimping is bent radially inward at a substantially right angle along the entire circumference as the end of the outer can is crimped. Furthermore, a radially bent portion is formed by bending the end of the outer can radially inward, and a protruding portion of the gasket is provided so as to protrude radially from the radially inner end of the bent portion. In this case, by increasing the radial length of the protruding portion, it becomes easier to ensure a radial insulation distance between the tip of the outer can and the outer peripheral surface of the cylindrical portion provided in the center of the sealing body.
[0005] However, when the end of the outer can is crimped, the end of the gasket is bent radially inward, which generates a large compressive stress in the circumferential direction at the radially inner end of the gasket. This can lead to wrinkles in the protruding portion of the gasket, causing the protruding portion to deform into a wavy shape. Due to these wrinkles, the protruding portion of the gasket alternates between portions that are deformed so as to bend outward in the axial direction of the battery and portions that are deformed axially inward and pressed against the axially outer surface of the sealing body. Furthermore, the greater the radial length of the protruding portion, the greater the axially outward deformation of the protruding portion.
[0006] If the occurrence of such wrinkles causes significant axial outward deformation at the protruding portion, various problems may occur. For example, when welding a metal current collector plate to a shoulder portion provided near the corner of the open end of the outer can, the gasket may prevent the current collector plate from contacting the shoulder portion, resulting in a poor weld. Also, when inspecting the height from the bottom to the shoulder portion of the battery during the inspection process during battery manufacturing, the inspection jig may come into contact with the protruding portion of the gasket instead of the shoulder portion, resulting in the battery being determined to be dimensionally defective.
[0007] Therefore, an object of the present disclosure is to provide a sealed battery that can suppress problems that occur when wrinkles occur at the end of a gasket in a configuration in which a sealing body is crimped and fixed to the end of an outer can via a gasket.
[0008] The sealed battery according to the present disclosure comprises an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, a cylindrical outer can with a bottom that houses the electrode assembly, a sealing body that closes the opening of the outer can, and an annular gasket that is interposed between the outer can and the sealing body, wherein a radially bent portion that is bent radially inward is formed at the open end of the outer can, so that the sealing body is crimped and fixed to the open end via the gasket, the gasket is formed with a protruding portion that protrudes radially inward from the radially inner end of the radially bent portion, and a notch is formed on the axially outer surface of the protruding portion that is continuous along at least a portion of the circumferential direction and has a radial width that includes the tip of the protruding portion, and the axial thickness of the portion of the protruding portion where the notch is formed is smaller than the thickness of a portion of the gasket that is adjacent to the radially outer side of the notch.
[0009] In the sealed battery according to the present disclosure, in a configuration in which a sealing body is crimped and fixed to the end of an outer can via a gasket, even if wrinkles occur at the end of the gasket, the formation of the notch prevents the tip portion of the protruding portion of the gasket, which is prone to deformation axially outward, from deforming axially outward beyond the shoulder portion of the outer can, thereby preventing defects caused by wrinkles in the gasket, such as poor welding of the current collector plate.
[0010] FIG. 4 is an axial cross-sectional view of a sealed battery according to an embodiment of the present disclosure, in which there are no wrinkles in the protruding portion of the gasket. FIG. 5 is an enlarged view of part A of FIG. 1. FIG. 1 is a view from above. FIG. 5 corresponds to FIG. 2, in which wrinkles have occurred in the protruding portion of the gasket in an embodiment. FIG. 6 is a view from above. FIG. 7 corresponds to FIG. 4, in which a problem occurs when wrinkles have occurred in the protruding portion of the gasket in a sealed battery of a comparative example. FIG. 7 corresponds to FIG. 2, in which there are no wrinkles in the protruding portion of the gasket in a sealed battery of another example of the embodiment. FIG. 8 corresponds to FIG. 8, in which wrinkles have occurred in the protruding portion of the gasket in a sealed battery of another example of the embodiment.
[0011] Hereinafter, embodiments of a sealed battery according to the present disclosure will be described in detail with reference to the drawings. The sealed battery according to the present disclosure may be a primary battery or a secondary battery. It may also be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. Hereinafter, a non-aqueous electrolyte secondary battery (lithium ion battery) using a non-aqueous electrolyte will be exemplified as a sealed battery according to one embodiment, but the sealed battery according to the present disclosure is not limited thereto, and the electrolyte may also be an aqueous electrolyte.
[0012] It is anticipated from the beginning that new embodiments may be constructed by appropriately combining the features of the embodiments and variations described below. In the following embodiments, the same components are designated by the same reference numerals in the drawings, and redundant description will be omitted. Furthermore, multiple drawings include schematic diagrams, and the dimensional ratios of the length, width, height, and other dimensions of each component between different drawings do not necessarily match. In this specification, the axial direction of the sealing body 19 of the sealed battery 10 is referred to as "upper," and the axial direction of the bottom 20a of the outer can 20 is referred to as "lower." Furthermore, among the components described below, components not recited in the independent claims representing the highest concepts are optional components and not essential components. Furthermore, the present disclosure is not limited to the following embodiments and variations thereof, and various improvements and modifications are possible within the scope of the claims and their equivalents.
[0013] Fig. 1 shows an axial cross-sectional view of a sealed battery 10 according to an embodiment of the present disclosure, in which there are no wrinkles in the protruding portion 31 of the gasket 30. Fig. 2 is an enlarged view of portion A in Fig. 1. Fig. 3 is a view as seen from above in Fig. 1. The axial cross-sectional view in Fig. 1 shows a cross section including the central axis of the sealed battery 10. As shown in Fig. 1, the sealed battery 10 includes an electrode assembly 14, a non-aqueous electrolyte, an outer can 20 which is a cylindrical metal container with a bottom that accommodates the electrode assembly 14 and the non-aqueous electrolyte, a sealing body 19 that closes the opening of the outer can 20, and a gasket 30.
[0014] The electrode assembly 14 includes a positive electrode 11, a negative electrode 12, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween. The outer can 20 is a cylindrical container with a bottom, and has a bottom 20a and a cylindrical portion 20b.
[0015] The non-aqueous electrolyte has ion conductivity (e.g., lithium ion conductivity). The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte is not limited to a liquid electrolyte (nonaqueous electrolytic solution), and may be a solid electrolyte using a gel polymer or the like. The sealed battery 10 is preferably a lithium ion battery. The electrolyte salt may be, for example, LiBF ４ , LiPF ６ Examples of the non-aqueous solvent include esters such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP), ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may contain a halogen-substituted product in which at least a portion of the hydrogen atoms of these solvents are substituted with halogen atoms such as fluorine.
[0016] Examples of halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, and fluorinated chain carboxylic acid esters such as methyl fluoropropionate (FMP). From the viewpoint of suppressing a decrease in the charge-discharge cycle characteristics of a nonaqueous electrolyte secondary battery or improving input characteristics, the nonaqueous electrolyte preferably contains 5% by mass or more of FEC, and more preferably 5% by mass to 15% by mass of FEC, relative to the mass of the nonaqueous electrolyte.
[0017] Examples of the solid electrolyte include solid or gel polymer electrolytes and inorganic solid electrolytes. 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. Examples of the matrix polymer include a polymer material that absorbs the non-aqueous solvent and gels. Examples of the polymer material include fluororesin, acrylic resin, and polyether resin. Examples of the inorganic solid electrolyte include materials known in all-solid-state lithium ion secondary batteries (e.g., oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.).
[0018] As described above, the electrode assembly 14 has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween. The positive electrode 11, the negative electrode 12, and the separator 13 are all long, strip-like bodies that are spirally wound and alternately stacked in the radial direction of the electrode assembly 14. 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 in both the longitudinal and lateral directions than the positive electrode 11. The separator 13 is formed to be at least slightly larger than the positive electrode 11, and, for example, two separators 13 are arranged to sandwich the positive electrode 11.
[0019] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer provided on both sides of the positive electrode core. The positive electrode core can be a foil of a metal, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on the surface. The positive electrode mixture layer contains a positive electrode active material, a conductive agent, such as acetylene black, and a binder, such as polyvinylidene fluoride (PVDF). The positive electrode 11 can be produced by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder to the positive electrode core, drying the coating, and then compressing it to form a positive electrode mixture layer on both sides of the positive electrode core.
[0020] For example, a lithium transition metal composite oxide is used as the positive electrode active material. Examples of metal elements contained in the lithium transition metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. An example of a suitable lithium transition metal composite oxide is a lithium metal composite oxide containing at least one of Ni, Co, and Mn. Specific examples include a composite oxide containing Ni, Co, and Mn, and a composite oxide containing Ni, Co, and Al.
[0021] The negative electrode 12 has a negative electrode core and a negative electrode mixture layer provided on both sides of the negative electrode core. The negative electrode core can be a foil of a metal such as copper or a copper alloy that is stable within the potential range of the negative electrode 12, or a film with such a metal disposed on the surface layer. The negative electrode mixture layer contains a negative electrode active material and a binder such as styrene butadiene rubber (SBR). The negative electrode 12 can be produced by applying a negative electrode mixture slurry containing the negative electrode active material and the binder to the negative electrode core, drying the coating, and then compressing it to form a negative electrode mixture layer on both sides of the negative electrode core.
[0022] The negative electrode active material may be, for example, natural graphite such as flake graphite, lump graphite, or amorphous graphite, or artificial graphite such as lump artificial graphite or graphitized mesophase carbon microbeads. The negative electrode active material may be a metal that alloys with lithium, such as Si or Sn, an alloy containing such a metal, or a compound containing such a metal, which may be used in combination with graphite. A suitable example of such an active material is SiO ２The Si-containing material is a Si-containing material in which fine Si particles are dispersed in a silicate phase such as lithium silicate or an amorphous carbon phase.
[0023] Insulating plates 15 and 16 are disposed above and below the electrode body 14. In the example shown in Fig. 1 , a positive electrode lead 17 attached to the positive electrode 11 passes through a through-hole in the insulating plate 15 and extends toward the sealing body 19, and a negative electrode lead 18 attached to the negative electrode 12 passes through a through-hole in the insulating plate 16 and extends toward the bottom 20a of the outer can 20. The positive electrode lead 17 is connected by welding or the like to the inner surface of the sealing body 19 facing inward, and the sealing body 19 serves as a positive electrode terminal. The negative electrode lead 18 is connected by welding or the like to the inner surface of the bottom 20a of the outer can 20, and the outer can 20 serves as a negative electrode terminal.
[0024] An annular gasket 30 is interposed between the outer can 20 and the sealing body 19 to ensure the sealing of the inside of the battery and the insulation between the outer can 20 and the sealing body 19 .
[0025] A radially bent portion 20c is formed in the upper end portion, which is the end portion on the opening side of the outer can 20, by bending the sealing body 19 radially inward along the entire circumference, and thereby the sealing body 19 is crimped and fixed to the upper end portion of the outer can 20 via a gasket 30. As shown in Fig. 2, in conjunction with this crimping, an annular shoulder portion 20d is formed near the corner of the upper end portion of the outer can 20, which is the portion whose height from the bottom portion 20a is greatest at the radial middle position.
[0026] An annular grooved portion 28 is provided at the upper end of the cylindrical portion 20b of the outer can, closer to the bottom portion 20a than the radially bent portion 20c. The grooved portion 28 is a portion that protrudes radially inward around the entire circumference at the upper end side of the cylindrical portion 20b of the outer can 20. The grooved portion 28 is formed by recessing a portion of the cylindrical portion 20b radially inward by, for example, spinning. The grooved portion supports the sealing body 19, which will be described later, via a gasket 30.
[0027] An elastic insulating resin can be used for the gasket 30. Examples of such resins include polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), perfluoroalkoxy fluororesin (PFA), nylon, etc.
[0028] The sealing body 19 is a disk-shaped member equipped with a current interruption mechanism. The sealing body 19 has a structure in which an internal terminal plate 21, an insulating plate 23, a rupture plate 22, and a cap 25 are stacked in this order from the electrode body 14 side. The internal terminal plate 21 has a thin-walled portion in the center that is thinner than the outer annular portion to which the positive electrode lead 17 is connected.
[0029] The insulating plate 23 is a generally ring-shaped member made of insulating material and has a substantially Z-shaped cross section. The radially middle portion of the rupture plate 22 is disposed opposite the internal terminal plate 21 via the insulating plate 23. The center of the rupture plate 22 is connected to the thin-walled portion at the center of the internal terminal plate 21 by welding or the like through a circular hole in the insulating plate 23, thereby achieving electrical continuity.
[0030] Furthermore, the rupture plate 22 has an easily breakable portion 22a in the radially intermediate portion. The easily breakable portion 22a is configured as an annular groove formed on the inner surface (lower surface in FIG. 1) of the rupture plate 22. The groove for configuring the easily breakable portion 22a may be formed on the outer surface (upper surface in FIG. 1) of the rupture plate 22.
[0031] The cap 25 is hat-shaped and has an annular flange 26 on its outer periphery, and the inner surface of the flange 26 and the outer surface of the outer periphery of the rupture plate 22 are welded together so as to be electrically conductive.
[0032] A plurality of arc-shaped protrusions 22b (FIG. 2) are formed along the circumferential direction on the outer periphery side of the easily breakable portion 22a on the inner surface of the rupture plate 22. The outer periphery of the insulating plate 23 is fitted into the inner diameter side of the plurality of protrusions 22b of the rupture plate 22. Furthermore, a fitting cylindrical portion 22c is formed on the outer periphery of the rupture plate 22, protruding upward along the entire periphery, and a flange 26 of a cap 25 is fitted into the fitting cylindrical portion 22c.
[0033] The internal terminal plate 21 is fitted onto the inner surface of the insulating plate 23 .
[0034] 2, such a sealing body 19 is fixed to the outer can 20 by crimping via a gasket 30, with the flange 26 of the cap 25 and the outer peripheral portion of the rupture plate 22 overlapping each other. At this time, as shown in Figures 2 and 3, an annular protruding portion 31 that protrudes around the entire circumference of the gasket 30 is formed radially inward from the radially inner end of the radially bent portion 20c of the outer can 20. By increasing the radial length of this protruding portion 31, it is possible to ensure a radial insulation distance between the tip of the outer can 20 and the outer peripheral surface of the tubular portion 27 that forms the cap 25 of the sealing body 19.
[0035] In the sealed battery 10, the internal terminal plate 21, to which the positive electrode lead 17 is connected, is electrically connected to the rupture plate 22, thereby forming a current path from the electrode assembly 14 to the rupture plate 22. When an abnormality occurs in the battery and the internal pressure increases, the internal terminal plate 21 breaks, and the thin-walled portion of the internal terminal plate 21 is separated from its outer annular portion and deformed so as to become convex toward the outside of the battery. This interrupts the current path. When the internal pressure of the battery further increases, the easily breakable portion 22a breaks as described above, forming a vent for gas inside the battery. The gas released from this vent is discharged to the outside of the battery through an opening (not shown) formed in the cap 25.
[0036] The structure of sealing body 19 is not limited to the structure shown in FIG.
[0037] In the above-described configuration in which the sealing body 19 is crimped to the end of the outer can 20 via the gasket 30, the end of the gasket 30 is bent radially inward as the open end of the outer can 20 is crimped during battery manufacturing. This causes a large circumferential compressive stress at the radially inner end of the gasket 30. This can result in wavy wrinkles in the radially inner end of the gasket 30 protruding from the outer can 20. Due to these wrinkles, the protruding portion 31 of the gasket 30 alternates between portions that are deformed so as to bend outward in the axial direction of the battery and portions that are deformed axially inward and pressed against the axially outer surface of the sealing body 19. Furthermore, the greater the radial length of the protruding portion 31, the greater the axial deformation of the protruding portion 31.
[0038] If the occurrence of such wrinkles causes significant axial outward deformation at multiple circumferential positions in the protruding portion 31 of the gasket 30, the deformed portion of the protruding portion may impede contact with the shoulder portion 20d of the current collector plate, inspection jig, or the like. This may result in defects such as poor welding of the current collector plate or incorrect battery dimensions. Furthermore, if the gasket 30 has a protruding portion, it is difficult to completely prevent the occurrence of wrinkles. In this embodiment, to prevent such defects, a notch 32 is formed along the circumferential direction on the axially outer surface of the protruding portion 31, as described below.
[0039] The configuration of the gasket 30 will be described in detail below with reference to FIGS. 1 to 3. As shown in FIGS. 1 to 3, the gasket 30 is formed of resin so as to have a generally U-shaped cross section and a generally annular planar shape. Specifically, the gasket 30 has a cylindrical portion 33 provided at the outer peripheral end, an outer annular plate portion 34 connected to the axially outer end of the cylindrical portion 33 and extending radially inward, and an inner annular plate portion 35 connected to the axially inner end of the cylindrical portion 33 and extending radially inward. The outer annular plate portion 34 is formed with the above-mentioned protruding portion 31, which protrudes radially inward beyond the radially inner end of the radially bent portion 20c of the outer can 20. The radial length of the protruding portion 31 may be 0.5 mm or greater.
[0040] The radially inner end of the inner annular plate portion 35 is bent toward the bottom portion 20a (lower side in FIG. 2 ), and then an inner bent portion 36 is formed that extends radially inward so as to face the side surface of the bottom portion 20a of the insulating plate 23. An annular protrusion 35a is formed on the axially outer surface of the inner annular plate portion 35, and the protrusion 35a fits into the annular groove 22d formed on the inner surface of the rupture plate 22, thereby increasing the bonding strength of the gasket 30 to the sealing body 19.
[0041] In this embodiment, a circumferentially continuous notch 32 is formed around the entire circumference of the axially outer surface of the protruding portion 31 of the gasket 30. The notch 32 is formed to have a radial width that includes a tip 37 of the protruding portion 31.
[0042] 2 and 3 , when no wrinkles are formed in the protruding portion 31, the notch 32 has a conical surface shape like a chamfer obtained by removing a corner of the tip end portion of the axially outer surface of the gasket 30. As a result, the notch 32 has a shape formed by cutting out the axially outer surface of the protruding portion 31 so that the thickness of the protruding portion 31 on the tip 37 side gradually decreases.
[0043] The axial thickness of the protruding portion 31 at the portion where the notch 32 is formed is smaller than the thickness d1 ( FIG. 2 ) of the portion of the gasket 30 adjacent to the radially outer side of the notch 32. In FIG. 3 , the protruding portion 31 is shown as a sandy portion. In FIG. 2 , the thickness of the protruding portion 31 gradually increases radially inward from the protruding base position from the outer can 20 to the notch 32, but the thickness may be constant from the protruding base position to the notch 32.
[0044] 1 to 3 show the shape of the gasket 30 when there are no wrinkles in the protruding portion 31. In this case, as shown in Fig. 2, the protruding portion 31 does not protrude axially outward (toward the upper side in Fig. 2) from the shoulder portion 20d of the outer can 20. In Fig. 2, the solid line S indicates an imaginary plane that passes through the shoulder portion 20d and is perpendicular to the central axis of the battery. The protruding portion 31 shown in Fig. 2 does not protrude axially outward from the imaginary plane S.
[0045] Such a notch 32 can be formed by a notch previously formed in the gasket 30 before insertion into the opening end of the outer can 20. For example, if the gasket 30 before insertion into the outer can has a cylindrical portion and an inner annular plate portion 35, but is an annular shape with a generally L-shaped cross section before the outer annular plate portion 34 is formed, a conical notch is previously formed in the outer peripheral surface of the axially outer end of the cylindrical portion, where the protruding portion 31 will be. Then, the gasket 30 is inserted into the opening end of the outer can 20 with the portion that will become the protruding portion 31 protruding axially outward from the cylindrically extending opening end of the outer can 20. Thereafter, the opening end of the outer can 20 is crimped radially inward to form a radially bent portion 20c in the outer can 20. As a result, the protruding portion 31 is also deformed radially inward, and the notch 32 having the shape shown in FIGS. 2 and 3 is formed in the axially outer surface of the protruding portion 31, including the tip 37.
[0046] 1 to 3, it is difficult to completely prevent wrinkles from forming in the protruding portion 31 during the actual manufacture of the sealed battery 10. Figures 4 and 5 show an embodiment in which wrinkles have formed in the protruding portion 31 of the gasket 30, with Figure 4A corresponding to Figure 2 and Figure 5 being a view from above of Figure 4.
[0047] In this case, as shown in FIG. 5 , due to wrinkles (not shown) occurring at multiple radial positions on the protruding portion 31 of the gasket 30, portions of the protruding portion 31 that are warped outward in the axial direction and have a reduced radial length and portions that are pressed against the flange 26 of the sealing body 19 and have a large radial length are alternately generated in the circumferential direction. As a result, the inner peripheral edge of the protruding portion 31 has a continuous, annular waveform when viewed from above as shown in FIG. 5 . For example, at a position P in FIG. 5 where the inner peripheral edge of the protruding portion 31 is deformed to be recessed radially outward, the protruding portion 31 is deformed to be warped outward in the axial direction. On the other hand, at a position Q in FIG. 5 where the inner peripheral edge of the protruding portion 31 protrudes radially inward, a portion of the protruding portion 31, including its tip end, is pressed against the axially outer surface of the flange 26.
[0048] When wrinkles occur in the protruding portion 31, the surface of the protruding portion 31 has a circumferentially wavy shape. As in the cases of Figures 2 and 3, the notch 32 has a shape formed by cutting out the axially outer surface of the protruding portion 31 so that the thickness of the protruding portion 31 decreases toward the tip. Furthermore, the axial thickness of the portion of the protruding portion 31 where the notch 32 is formed is smaller than the thickness of the portion of the gasket 30 adjacent to the radially outer side of the notch 32.
[0049] According to this embodiment, a notch 32 that reduces the thickness is formed in a portion of the axially outer surface of the protruding portion 31, including the tip 37. As a result, even if wrinkles occur in the protruding portion 31, the portion of the protruding portion 31 on the tip 37 side, which is prone to deform axially outward, can be prevented from deforming axially outward beyond the shoulder 20d of the outer can 20. For example, as shown in FIG. 4 , even at a position where the protruding portion 31 is deformed axially outward to the maximum extent, the protruding portion 31 does not protrude axially outward beyond the imaginary plane S. As a result, contact with the shoulder 20d of the current collector plate 40 is not obstructed by the protruding portion 31, and poor welding to the shoulder 20d of the current collector plate 40 can be prevented.
[0050] Similarly, in the inspection process during battery manufacturing, when an inspection jig for inspecting the height from the bottom 20 a of the battery to the shoulder 20 d is pressed against the shoulder 20 d, even if wrinkles occur in the protruding portion 31, the inspection jig can be prevented from contacting the protruding portion 31 instead of the shoulder 20 d. This prevents the occurrence of dimensional defects in the battery. In this way, according to this embodiment, defects caused by wrinkles in the gasket 30 can be suppressed.
[0051] In this example, the notch 32 is formed around the entire circumference of the protruding portion 31. However, the notch 32 may be formed so as to be continuous along at least a portion of the circumferential direction of the axially outer surface of the protruding portion 31. For example, since the protruding portion 31 deforms significantly axially outward in the circumferential range of the protruding portion 31 indicated by the arrow α in FIG. 5 , a circular-arc notch that is continuous in the circumferential direction beyond this range and has a radial width may be formed on the axially outer surface of the protruding portion 31. The current collector plate 40 ( FIG. 4 ) may be welded to the shoulder portion 20d of the outer can 20 in a range that coincides with the notch in the circumferential direction, so that the current collector plate 40 faces the notch. In this case, poor welding of the current collector plate 40 to the shoulder portion 20d, which is a defect caused by wrinkles in the gasket 30, can be prevented.
[0052] On the other hand, Fig. 6 is a diagram corresponding to Fig. 4 , illustrating the inconvenience that occurs when wrinkles form in the protruding portion 31b of a comparative sealed battery 10a in which the protruding portion 31 of the gasket 30b does not have a notch. When wrinkles form in the protruding portion 31b, since no notch is formed on the axially outer surface, including the tip of the protruding portion 31b, multiple circumferential positions on the tip side of the protruding portion 31b are significantly deformed axially outward, as shown in Fig. 6 . This causes the protruding portion 31b to protrude axially outward beyond the imaginary plane S. This may result in defects such as poor welding between the current collector plate 40 and the shoulder portion 20d of the outer can 20.
[0053] FIG. 7 is a view corresponding to FIG. 2 of a sealed battery 10b according to another embodiment, in which the protruding portion 31c of the gasket 30c has no wrinkles. In this sealed battery 10b, a notch 38 formed around the entire periphery of the axially outer surface of the protruding portion 31c of the gasket 30c changes the thickness of the protruding portion 31c in a stepped manner. Specifically, as shown in FIG. 7, when no wrinkles are formed in the protruding portion 31c, the notch 38 has a shape in which the corners of the leading end portion of the axially outer surface of the gasket 30c are removed by a step. As a result, the notch 38 has a shape in which the thickness of the leading end of the protruding portion 31c is reduced. In this way, the axial thickness of the protruding portion 31c at the portion where the notch 38 is formed is smaller than the thickness of the portion of the gasket 30c adjacent to the radially outer side of the notch 38.
[0054] The notch 38 can be formed by a notch that has been pre-formed in the gasket 30c before it is inserted into the open end of the outer can 20. For example, if the gasket 30c before it is inserted into the outer can 20 has a cylindrical portion and an inner annular plate portion 35, but is an annular portion with a generally L-shaped cross section before the outer annular plate portion 34 is formed, a notch having a stepped surface and a small-diameter cylindrical portion adjacent to the axially outer side of the stepped surface is pre-formed in the outer peripheral surface of the axially outer end of the portion that will become the protruding portion 31c of the cylindrical portion. The outer diameter of the small-diameter cylindrical portion is smaller than the outer diameter of the portion of the cylindrical portion of the gasket 30 that is adjacent to the axially inner side of the stepped portion.
[0055] Then, with the portion that will become the protruding portion 31c protruding axially outward from the cylindrically extending opening end of the outer can 20, the gasket 30c is inserted into the opening end of the outer can 20. Thereafter, the opening end of the outer can 20 is crimped radially inward to form the radially bent portion 20c. As a result, the protruding portion 31c is also deformed radially inward, and a notch 38 having the shape shown in FIG. 7 is formed in a portion including the tip of the axially outer surface of the protruding portion 31c.
[0056] Fig. 8 shows a diagram corresponding to Fig. 4 in the case where wrinkles have occurred in the protruding portion 31c of the gasket 30c in the configuration of this example. In this case, as in the case shown in Fig. 5, wrinkles have occurred at multiple radial positions in the protruding portion 31c, causing the protruding portion 31 to alternate in the circumferential direction between portions that have been warped outward in the axial direction and reduced in radial length and portions that have been pressed against the flange 26 of the sealing body 19 and increased in radial length. As a result of this deformation of the protruding portion 31c, as shown in Fig. 8, portions of the protruding portion 31c that have been deformed outward in the axial direction and portions of the protruding portion 31c that have been pressed against the flange 26, similar to the shape in Fig. 7, alternate in the circumferential direction of the protruding portion 31c.
[0057] When wrinkles occur in the protruding portion 31c, the surface of the protruding portion 31c has a circumferentially wavy shape. As in the case shown in Fig. 7, the notch 38 has a shape formed by cutting out the axially outer surface of the protruding portion 31c so that the thickness of the tip end of the protruding portion 31c is reduced. Furthermore, the axial thickness of the portion of the protruding portion 31c where the notch 38 is formed is smaller than the thickness of the portion of the gasket 30 adjacent to the radially outer side of the notch 38.
[0058] According to the configuration of this example, a thin notch 38 is formed in the axially outer surface of the protruding portion 31c in a portion including the tip 39. As a result, even if wrinkles occur in the protruding portion 31c, the portion of the protruding portion 31c on the tip 39 side, which is prone to deform axially outward, can be prevented from deforming axially outward beyond the shoulder 20d of the outer can 20. Therefore, similar to the configurations of Figures 1 to 5, problems caused by wrinkles in the gasket 30c can be prevented.
[0059] Furthermore, according to the configuration of this example, the notch 38 causes the thickness of the protruding portion 31c to change in a stepped manner. This allows the creeping distance from the radially inner end of the radially bent portion 20c of the outer can 20, along the surface of the protruding portion 31c of the gasket 30c, as shown at A1, A2, A3, and A4 in FIG. 7, to the surface of the flange 26 of the sealing body 19 to be longer than when the conical notch 32 is formed as in the configurations of FIGS. 1 to 5. This ensures better insulation between the outer can 20 and the sealing body 19. Other configurations and functions of this example are similar to those of the configurations of FIGS. 1 to 5.
[0060] In this example, the notch may be formed so as to continue only along a portion of the circumferential direction of the axially outer surface of the protruding portion 31 c, which can prevent defects caused by wrinkles in the gasket 30 c, such as poor welding of the current collecting plate welded to the shoulder portion 20 d.
[0061] The present disclosure will be further described by the following embodiments. Configuration 1: A sealed battery comprising: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a cylindrical outer can with a bottom that houses the electrode assembly; a sealing body that closes the opening of the outer can; and an annular gasket interposed between the outer can and the sealing body, wherein a radially bent portion that is bent radially inward is formed at an open end of the outer can, so that the sealing body is crimped and fixed to the open end via the gasket, the gasket is formed with a protruding portion that protrudes radially inward from a radially inner end of the radially bent portion, and a notch is formed on an axially outer surface of the protruding portion that is continuous with at least a portion of the circumferential direction of the protruding portion and has a radial width that includes a tip of the protruding portion, and the axial thickness of the portion of the protruding portion where the notch is formed is smaller than the thickness of a portion of the gasket that is adjacent to the radially outer side of the notch. Configuration 2: The sealed battery according to Configuration 1, wherein the circumferential range in which the notch is formed is the entire circumference of the protruding portion.Configuration 3: The sealed battery according to Configuration 1 or Configuration 2, wherein the notch has a shape formed by cutting out an axially outer surface of the protruding portion so that the thickness of the tip end of the protruding portion is smaller.Configuration 4: The sealed battery according to Configuration 3, wherein the notch changes the thickness of the protruding portion in a stepwise manner.
[0062] 10, 10a, 10b Sealed battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15, 16 Insulating plate, 17 Positive electrode lead, 18 Negative electrode lead, 19 Sealing body, 20 Outer can, 20a Bottom, 20b Cylindrical portion, 20c Radial bend portion, 20d Shoulder portion, 21 Internal terminal plate, 22 Rupture plate, 22a Easily breakable portion, 22b Protrusion, 22c Fitting cylindrical portion, 22d Annular groove, 23 Insulating plate, 25 Cap, 26 Flange, 27 Cylindrical portion, 28 Grooved portion, 30, 30b, 30c Gasket, 31, 31b, 31c Protruding portion, 32 Notch, 33 Cylindrical portion, 34 Outer annular plate portion, 35 Inner annular plate portion, 35a Protrusion, 36: Inner bent portion, 37: Tip, 38: Notch, 39: Tip, 40: Current collecting plate, 41: Insulating ring.
Claims
1. A sealed battery comprising: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; a bottomed, cylindrical outer can containing the electrode assembly; a sealing body that closes the opening of the outer can; and an annular gasket interposed between the outer can and the sealing body, wherein a radially bent portion that is bent radially inward is formed at an open end of the outer can, so that the sealing body is crimped and fixed to the open end via the gasket, and the gasket is formed with a protruding portion that protrudes radially inward from a radially inner end of the radially bent portion, and a notch is formed in the axial outer surface of the protruding portion, the protruding portion having a radial width that is continuous with at least a portion of the circumferential direction of the axially outer surface of the protruding portion and that has a radial width that includes a tip of the protruding portion, and the axial thickness of the protruding portion at a portion where the notch is formed is smaller than the thickness of a portion of the gasket that is adjacent to the radially outer side of the notch.
2. The sealed battery according to claim 1, wherein the circumferential range in which the notch is formed is the entire circumference of the protruding portion.
3. The sealed battery according to claim 1, wherein the cutout has a shape formed by cutting out an axially outer side surface of the protruding portion so that the thickness of the tip end side of the protruding portion becomes smaller.
4. The sealed battery according to claim 3, wherein the notch changes the thickness of the protruding portion in a stepwise manner.