Hermetically sealed battery

Abstract

This hermetically sealed battery includes an electrode body, an exterior can (16), a sealing body, and a gasket (28) interposed between the exterior can and the sealing body. The sealing body is swaged and fixed to the opening-side end of the exterior can via the gasket. The gasket has a cylindrical body part (50) and a protrusion (54) protruding over the entire circumference from the outer peripheral surface of the body part to the outside in the radial direction. The protrusion is elastically bent outward in the axial direction so that the tip approaches the outer peripheral surface of the body part in a state in which the inner peripheral surface of a cylindrical part provided at the opening-side end part of the exterior can is pressed toward the outside in the radial direction.

Description

sealed battery

[0001] The present disclosure relates to a sealed battery, and in particular to a configuration in which a sealing body is crimped and fixed to the open end of an outer can via a gasket, which configuration achieves both an improved ability to remove electrolyte from the inner surface of the open end of the outer can and an improved insertability of the gasket into the outer can.

[0002] Conventionally, a sealed battery has been known that includes an electrode assembly, a cylindrical outer can with a bottom that houses the electrode assembly, and a sealing member that closes the opening of the outer can. In such a sealed battery, an electrolyte solution may be poured into the outer can before the sealing member is attached to the outer can. However, if the electrolyte solution remains on the inner surface of the open end of the outer can after the electrolyte solution is poured, the electrolyte solution adhering to the outer can may cause corrosion of the outer can or may cause the electrolyte solution to leak from the outer can.

[0003] Patent Document 1 describes a sealed battery in which a sealing body is crimped and fixed to the open end of an outer can via an insulating resin gasket. In the configuration described in Patent Document 1, in the sealed battery, a protrusion with a trapezoidal cross section that protrudes radially outward is formed on the outer peripheral surface of the gasket, and the protrusion abuts against the inner peripheral surface of the open end of the outer can. When the open end of the outer can is extended in the axial direction and the sealing body is inserted into the open end together with the gasket, the protrusion of the gasket abuts against the inner peripheral surface of the open end, and the protrusion scrapes off the electrolyte adhering to the inner peripheral surface.

[0004] International Publication No. 2021 / 200439

[0005] According to the configuration described in Patent Document 1, when a gasket is inserted into an outer can, the protrusions of the gasket scrape off any remaining electrolyte adhering to the inner surface of the open end of the outer can, potentially reducing the amount of electrolyte remaining on the open end of the outer can. However, with the gasket described in Patent Document 1, if the outer diameter of the protrusions is made too large compared to the inner diameter of the open end of the outer can in order to increase the amount of electrolyte scraped off, the protrusions must be compressed radially with a large force when inserting the gasket into the open end. This leaves room for improvement in terms of improving the gasket's ease of insertion into the can. On the other hand, if the outer diameter of the gasket's protrusions is roughly the same as the inner diameter of the open end of the outer can in order to improve can insertion, it becomes difficult to increase the amount of electrolyte scraped off, leaving room for improvement in terms of improving the ability to remove electrolyte from the inner surface of the outer can.

[0006] Therefore, an object of the present disclosure is to provide a sealed battery in which a sealing body is crimped and fixed to the open end of the outer can via a gasket, and which can achieve both an improved ability to remove electrolyte from the inner surface of the open end of the outer can and an improved insertability of the gasket into the outer can.

[0007] The sealed battery according to the present disclosure is 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 contains the electrode assembly and an electrolyte; 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 the sealing body is crimped and fixed to the open end of the outer can via the gasket; the gasket includes a cylindrical main body and a protrusion that protrudes radially outward from the outer peripheral surface of the main body around its entire circumference, and the protrusion is elastically bent axially outward so that its tip approaches the outer peripheral surface of the main body while biasing the inner peripheral surface of the cylindrical portion provided at the open end of the outer can radially outward.

[0008] In the sealed battery according to the present disclosure, when inserting a gasket into an outer can, the biasing force of the protrusions against the inner circumferential surface of the open end of the outer can can be ensured, and the elastic bending of the protrusions outward in the axial direction improves the ease of inserting the gasket into the outer can, thereby improving both the ability to remove electrolyte from the inner surface of the open end of the outer can and the ease of inserting the gasket into the outer can.

[0009] 1 is an axial cross-sectional view of a sealed battery according to an embodiment of the present disclosure; FIG. 2 is an enlarged view of part A of FIG. 1; FIG. 3 is a cross-sectional view of a gasket before insertion into an outer can in an embodiment; FIG. 4 is a view showing a process of inserting a gasket into an outer can in an embodiment; FIG. 5 is a cross-sectional view of a main part showing an initial state when inserting a gasket into an outer can in an embodiment; FIG. 6 is a view corresponding to FIG. 4( a) of a sealed battery of a comparative example; FIG. 7 is a view corresponding to FIG. 2 in another example of an embodiment; and FIG. 8 is a view corresponding to FIG. 5 in another example of an embodiment.

[0010] 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. In the following, a secondary battery (lithium ion battery) using a non-aqueous electrolyte will be exemplified as a sealed battery according to one embodiment.

[0011] 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 explanations are omitted. Furthermore, multiple drawings include schematic diagrams, and the dimensional ratios of the length, width, height, etc. of each component between different drawings do not necessarily match. Furthermore, among the components described below, components that are not recited in the independent claims representing the highest concept are optional components and are 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 of this application and their equivalents.

[0012] Fig. 1 is an axial cross-sectional view of a sealed battery 10 according to an embodiment. Fig. 2 is an enlarged view of part A in Fig. 1. As shown in Fig. 1, the sealed battery 10 includes a positive electrode 11, a negative electrode 12, and a separator 13, and is provided with an electrode assembly 14 in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween. The sealed battery 10 also includes a cylindrical outer can 16 with a bottom that houses the electrode assembly 14, and a sealing body 17 that closes the opening of the outer can 16. The outer can 16 houses a nonaqueous electrolyte together with the electrode assembly 14.

[0013] The exterior can 16 is a cylindrical metal container with a bottom, and has a tubular portion 30 and a bottom portion 31 provided at one axial end of the tubular portion 30. The exterior can 16 has a grooved portion 34 (described below) formed on the other axial end, which is the open end side of the tubular portion 30, and the sealing body 17 is supported by the grooved portion 34 to close the opening of the exterior can 16. For ease of explanation, the sealing body 17 side of the sealed battery 10 will be referred to as the top, and the bottom 31 side of the exterior can 16 will be referred to as the bottom.

[0014] The non-aqueous electrolyte has ion conductivity (e.g., lithium ion conductivity). The non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. 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.

[0015] 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 deterioration in the charge / discharge cycle characteristics of a sealed 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, based on the mass of the nonaqueous electrolyte.

[0016] As described above, the electrode assembly 14 has a wound structure in which the positive electrode 11 and the negative electrode 12 are spirally 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.

[0017] A positive electrode tab 20 and a negative electrode tab 21 are connected to the electrode body 14. The positive electrode tab 20 electrically connects the positive electrode 11 and the sealing body 17. The positive electrode tab 20 is provided in the longitudinal center of the positive electrode 11, at a position away from the winding start end and winding end end of the electrode body 14.

[0018] The negative electrode tab 21 is joined to an exposed core portion provided at the winding-start end, which is one longitudinal end of the negative electrode 12 located on the winding-start side of the negative electrode 12. In the example shown in Fig. 1 , the positive electrode tab 20 passes through the opening of the upper insulating plate 18, extends toward the sealing body 17, and is joined to the underside of the sealing body 17, with the sealing body 17 serving as the positive electrode terminal. The negative electrode tab 21 passes through the through-hole of the annular lower insulating plate 19, is bent so as to fit along the inner surface of the bottom 31 of the outer can 16, and is connected to the inner bottom surface of the outer can 16 by welding or the like, with the outer can 16 serving as the negative electrode terminal.

[0019] The negative electrode 12 is disposed on the outermost peripheral surface of the electrode body 14, and the exposed surface of a negative electrode core (described below) constituting the negative electrode 12 abuts against the inner peripheral surface of the outer can 16. This electrically connects both longitudinal ends of the negative electrode 12 to the outer can 16, ensuring good current collection.

[0020] The positive electrode 11 includes a positive electrode core and a positive electrode mixture layer formed on both sides of the 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 preferably contains a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF), and is formed on both sides of the positive electrode core. The thickness of the positive electrode mixture layer is, for example, 40 μm or more and 100 μm or less. The positive electrode active material can be, for example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al, or the like. The positive electrode tab 20 is preferably directly bonded to the positive electrode core by ultrasonic welding or the like.

[0021] The negative electrode 12 has a negative electrode core and a negative electrode mixture layer formed on both sides of the negative electrode core. The negative electrode core can be made of 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. The negative electrode mixture layer contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR). The thickness of the negative electrode mixture layer is, for example, 40 μm or more and 100 μm or less. For example, graphite, a Si-containing material, or the like is used as the negative electrode active material. The negative electrode tab 21 is preferably directly bonded to the negative electrode core by ultrasonic welding or the like.

[0022] An annular gasket 28 is interposed between the exterior can 16 and the sealing body 17. The sealing body 17 is fixed by crimping to the upper end portion, which is the open end portion of the exterior can 16, via the gasket 28. Specifically, a radially bent portion 38 that is bent radially inward around the entire periphery is formed at the upper end portion of the exterior can 16, and the upper end portion of the exterior can 16 is crimped to the peripheral edge of the sealing body 17 via the gasket 28. This seals the inside of the battery.

[0023] Furthermore, the exterior can 16 has a groove 34 formed, for example, by pressing the side surface from the outside, that supports the sealing body 17. The groove 34 is preferably formed in an annular shape along the circumferential direction of the exterior can 16, and supports the sealing body 17 on its upper surface.

[0024] The sealing body 17 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 23, a lower valve body 24, an insulating member 25, an upper valve body 26, and a cap 27 are layered. Each component constituting the sealing body 17 has, for example, a disk or ring shape, and all components except the insulating member 25 are electrically connected to each other. The cap 27 has a hat shape with an annular flange 27b on its outer periphery and a cylindrical portion 27c with a closed upper end in the center. The internal terminal plate 23 has multiple openings 23a penetrating vertically. The lower valve body 24 and the upper valve body 26 are connected to each other at their respective centers, and an insulating member 25 is interposed between their respective peripheral edges. The flange portion 17a of the sealing body 17 is formed by the flange 27b of the cap 27 and the portions of each component of the sealing body 17, except the cap 27, that overlap the flange 27b in the axial direction. The flange portion 17 a is an annular portion provided on the outer periphery of the sealing body 17 .

[0025] When the internal pressure of the battery increases, the lower valve body 24 deforms and breaks, pushing the upper valve body 26 toward the cap 27, thereby interrupting the current path between the lower valve body 24 and the upper valve body 26. When the internal pressure increases further, the upper valve body 26 breaks, and gas is discharged from the opening 27a of the cap 27.

[0026] As described above, in the configuration in which the sealing body 17 is crimped and fixed to the open end of the outer can 16 via the gasket 28, during battery manufacturing, an electrolyte is injected into the interior of the outer can 16 from the open end of the outer can 16 before the sealing body 17 is crimped and fixed to the open end of the outer can 16. However, if the electrolyte remains on the inner surface of the open end of the outer can 16 after the electrolyte is injected, the electrolyte adhering to the outer can 16 may cause corrosion of the outer can 16 or cause the electrolyte to seep out of the outer can 16.

[0027] Furthermore, in the configuration described in Patent Document 1, in which the gasket's trapezoidal cross-sectional mountain-shaped protrusions scrape off residual electrolyte adhering to the inner surface of the open end of the outer can when the gasket is inserted into the outer can, there is room for improvement in terms of both improving the ability to remove electrolyte from the inner surface of the open end of the outer can and improving the ease of inserting the gasket into the outer can. Therefore, in this embodiment, as described below, a protrusion 54 is provided that protrudes radially outward from the outer peripheral surface of the cylindrical main body 50 of the gasket 28. While the protrusion 54 biases the inner peripheral surface of the cylindrical portion of the outer can 16 radially outward, the protrusion 54 is elastically bent axially outward so that a tip 55 approaches the outer peripheral surface of the main body 50.

[0028] The configuration of the gasket 28 will be described in detail below with reference to Figures 2 to 5. Figure 3 is a cross-sectional view of the gasket 28 before insertion into the outer can 16. Figure 4 is a diagram showing the process of inserting the gasket 28 into the outer can 16. Figure 5 is a cross-sectional view of a main part showing the initial state when the gasket 28 is inserted into the outer can 16.

[0029] As shown in FIGS. 1 and 2 , the gasket 28 is formed of resin so as to have a generally C-shaped cross section and a generally annular planar shape. Specifically, the gasket 28 includes a cylindrical main body 50 provided at the outer peripheral end, an inner annular plate 51 connected to the axially inner end of the main body 50 and extending radially inward, and an outer annular plate 52 connected to the axially outer end of the main body 50 and extending radially inward. The main body 50 is formed in a generally cylindrical shape. In FIG. 1 , the radially inner end of the radially bent portion 38 of the outer can 16 and the radially inner end of the outer annular plate 52 are generally aligned. Note that the outer annular plate 52 may have a protruding portion that protrudes radially inward beyond the radially inner end of the radially bent portion 38.

[0030] Elastic insulating resin can be used for the gasket 28. Examples of such resins include polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), perfluoroalkoxy fluororesin (PFA), nylon, etc.

[0031] 2, the gasket 28 is provided with a protrusion 54 that protrudes radially outward along the entire circumference from the outer peripheral surface of the cylindrical main body 50. The protrusion 54 protrudes from the outer peripheral surface of the main body 50 at a position axially inward from the axially outer surface of the flange 17a of the sealing body 17. The flange 17a is not shown in FIG.

[0032] The protrusion 54 biases the inner circumferential surface of the upper tubular portion 30a, which is provided in the tubular portion 30 of the outer can 16 adjacent to the upper side of the grooved portion 34, radially outward in the direction of arrow α in FIG. 2 . In this state, the protrusion 54 is elastically bent axially outward so that the tip 55 approaches the outer circumferential surface of the main body 50. By elastically bending the protrusion 54, a force is generated in the protrusion 54 that attempts to elastically restore the tip 55 radially outward. As a result, the protrusion 54 biases the inner circumferential surface of the upper tubular portion 30a radially outward. As described below, this improves both the ability to remove electrolyte from the inner surface of the open end of the outer can 16 and the ease of inserting the gasket 28 into the outer can 16.

[0033] Furthermore, a gap 60 ( FIG. 2 ) is formed between the protrusion 54 and the outer peripheral surface of the main body 50. The gap 60 is an annular gap with a substantially triangular cross section that continues around the entire circumference between the protrusion 54 and the outer peripheral surface of the main body 50. This makes it difficult for the protrusion 54 to be compressed by the outer peripheral surface of the main body 50 and the outer can 16 when the gasket 28 is inserted into the outer can 16, as will be described later, and prevents the protrusion 54 from being excessively compressed by the outer can 16. This further improves the ease of insertion of the gasket 28 into the outer can 16.

[0034] In order to form the gasket 28 as described above when assembled to the outer can 16, as shown in FIG. 3 , the gasket 28 before insertion into the outer can 16 is formed into an annular shape having a generally L-shaped cross section and including a cylindrical portion 50a and an inner annular plate portion 51. The cylindrical portion 50a has tapered inner and outer peripheral surfaces such that the inner and outer diameters gradually increase axially outward. The maximum outer diameter d1 at the outer axial end of the cylindrical portion 50a is larger than the inner diameter d2 of the upper cylindrical portion 30c of the outer can 16 before crimping, as shown in FIG. 5 (described later). Because the outer peripheral surface of the cylindrical portion 50a of the gasket 28 is tapered, the gasket 28 can be more easily inserted into the upper cylindrical portion 30c of the outer can 16 before crimping.

[0035] A protrusion 54 protrudes from the bottom end along the entire circumference of the outer circumferential surface of the tubular portion 50a of the gasket 28. The protrusion 54 is a dish-shaped protrusion that protrudes radially outward from the bottom end of the outer circumferential surface of the tubular portion 50a along the entire circumference, and is inclined axially outward.

[0036] The outer peripheral surface of the cylindrical portion 50a, adjacent to the axially outer side of the base position of the protrusion 54, has a curved shape such that the outer diameter decreases toward the bottom end. The protrusion 54 protrudes radially outward from the part of the cylindrical portion 50a where the outer diameter is smallest.

[0037] Furthermore, before the gasket 28 is assembled to the outer can 16, the outer diameter d3 of the gasket 28 at a portion including the tip 55 of the protrusion 54 is larger than the inner diameter d2 (see FIG. 5 described later) of the upper tubular portion 30c extending in the axial direction before the outer can 16 is crimped. As a result, as shown in FIG. 2 , the protrusion 54 is elastically bent so as to approach the outer circumferential surface of the main body 50, and the inner surface of the upper tubular portion 30a of the outer can 16 can be biased radially outward by the protrusion 54.

[0038] Next, referring to FIGS. 1 to 3 as appropriate, a method for crimping and fixing the sealing body 17 to the outer can 16 via the gasket 28 will be described using FIGS. 4 and 5 . First, a portion of the cylindrical portion of the open end of the outer can 16 before crimping is recessed radially inward by spinning to form a grooved portion 34, and an upper cylindrical portion 30c is formed above the grooved portion 34. Next, electrolyte is poured into the outer can 16 from above the open end. At this time, as shown in FIG. 4( a), electrolyte 70, shown as sand in FIG. 4( a), may remain on the inner surface near the corner between the upper cylindrical portion 30c and the annular plate portion 34a that forms the upper end of the grooved portion 34 and protrudes radially inward of the battery.

[0039] Next, as indicated by arrow β in Fig. 4(a), the gasket 28 together with the sealing body is inserted into the upper tubular portion 30c of the outer can 16 from above, i.e., from the outer axial end side. The sealing body is not shown in Fig. 4. As explained above, at this time, the outer diameter d3 of the portion including the tip 55 of the protrusion 54 of the gasket 28 is larger than the inner diameter d2 of the upper tubular portion 30c of the outer can 16, as shown in Fig. 5, and therefore, as the gasket 28 is inserted into the outer can 16, the protrusion 54 is elastically bent so that the tip 55 approaches the outer peripheral surface of the tubular portion 50a.

[0040] Then, as shown in FIG. 4( b), the gasket 28 is inserted into the upper cylindrical portion 30 c while the protrusions 54 scrape downward any electrolyte 70 remaining near the corner between the annular plate portion 34 a and the upper cylindrical portion 30 c of the outer can 16. At this time, the outer peripheral surface of the upper end of the cylindrical portion 50 a of the gasket 28 is also pressed against the inner surface of the upper cylindrical portion 30 c of the outer can 16. Then, as shown in FIG. 4( c), the gasket 28 is placed on the upper surface of the annular plate portion 34 a with the protrusions 54 urging the inner surface of the upper cylindrical portion 30 c radially outward. Therefore, the electrolyte 70 remaining near the corner and adhering to the inner surface of the outer can 16 can be scraped down to near the upper surface of the annular plate portion 34 a. Furthermore, since the inner annular plate portion 51 of the gasket 28 is pressed against the upper surface of the annular plate portion 34a, the electrolyte 70 can be pushed out radially inward from between the inner annular plate portion 51 and the annular plate portion 34a.

[0041] Thereafter, the opening end of the outer can 16 and the upper portion of the cylindrical portion 50a of the gasket 28 are crimped radially inward along the entire circumference. The outer periphery of the flange portion 17a of the sealing body 17 is sandwiched between the radially bent portion 38 formed by the crimping and the upper surface of the grooved portion 34, with the gasket 28 interposed therebetween, thereby fixing the sealing body 17 to the outer can 16.

[0042] With the sealed battery 10 described above, when inserting the gasket 28 into the outer can 16, the biasing force of the protrusions 54 against the inner circumferential surface of the open end of the outer can 16 can be ensured, and the elastic bending of the protrusions 54 outward in the axial direction can improve the ease of inserting the gasket 28 into the outer can 16. This improves both the ability to remove electrolyte from the inner surface of the open end of the outer can 16 and the ease of inserting the gasket 28 into the outer can 16.

[0043] Furthermore, the protrusion 54 protrudes from the outer peripheral surface of the main body 50 at a position axially inward of the axially outer surface of the flange 17a of the sealing body 17. This prevents the radial bent portion 38 from compressing the protrusion 54 against the upper surface of the flange 17a, thereby preventing a decrease in the sealing performance of the sealing body 17.

[0044] Furthermore, since the protrusion position of the protrusion 54 is the axial inner end of the outer peripheral surface of the main body 50, more of the electrolyte adhering to the inner surface of the opening end of the outer can 16 can be scraped off up to the vicinity of the grooved portion 34.

[0045] In addition, the protrusion position of the protrusion 54 may be located on the outer surface of the main body 50, in a range axially inward from the axial outer surface of the flange portion 17a of the sealing body 17, and axially outward from the axial inner end of the outer surface of the main body 50.

[0046] FIG. 6 is a view corresponding to FIG. 4( a) of a comparative sealed battery. The comparative gasket 28a has a shape similar to that of the gasket described in Patent Document 1. Specifically, the comparative gasket 28a is formed in a substantially L-shaped cross-section ring shape before insertion into the outer can 16a and before crimping the open end. The gasket 28a includes a cylindrical portion 62 and an inner annular plate portion 61 that protrudes radially inward from the bottom end of the cylindrical portion 62. A trapezoidal protrusion 63 protrudes from the bottom of the outer peripheral surface of the cylindrical portion 62 around the entire circumference. The outer diameter of the gasket 28a, including the tip of the protrusion 63, is equal to or larger than the inner diameter of the upper cylindrical portion 30c that extends axially before crimping the outer can 16a.

[0047] 4(a), Fig. 6 shows the initial state of the process of assembling the gasket 28 to the outer can 16a. At this time, the annular gasket 28 with a generally L-shaped cross section is inserted into the inside of the upper cylindrical portion 30c extending in the axial direction of the outer can 16. Even in this comparative example, it is possible that the protrusion 63 can scrape off the electrolyte remaining on the inner surface of the upper cylindrical portion 30c of the outer can 16.

[0048] However, in the gasket 28a of the comparative example, if the outer diameter of the protrusion 63 is made too large compared to the inner diameter of the upper cylindrical portion 30c of the outer can 16a in order to increase the amount of electrolyte scraped off, the protrusion 63 needs to be compressed radially by the outer can 16a with a large force when the gasket 28a is inserted into the upper cylindrical portion 30c. This increases the resistance when inserting the gasket 28 into the outer can 16a. Therefore, the comparative example leaves room for improvement in terms of both improving the ability to remove electrolyte from the inner surface of the open end of the outer can 16a and improving the ease of inserting the gasket 28a into the outer can 16a.

[0049] According to the present embodiment, when the gasket 28 is bent, a protrusion 54 is formed that presses against the inner surface of the outer can 16, thereby preventing the above-described inconvenience and improving both the ability to remove the electrolyte from the inner surface of the open end of the outer can 16 and the ease of inserting the gasket 28 into the outer can 16.

[0050] 7 is a view corresponding to FIG. 2 of another example of the embodiment. In the configuration of this example, a ring-shaped recess 56 having a generally rectangular cross section and continuing around the entire circumference is formed on the outer peripheral surface of the axially inner end portion on the bottom side of the main body 50 of the gasket 28b. A protrusion 54a protrudes radially outward from the bottom end of the outer peripheral surface of the main body 50 around the entire circumference, adjacent to the lower end, which is the axially inner end, of the inner surface of the recess 56, and is inclined axially outward.

[0051] In this state, the protrusion 54a is elastically bent so as to approach the axially outer side of the base end of the protrusion 54a on the outer peripheral surface of the main body 50, and biases the inner surface of the upper tubular portion 30a of the outer can 16 radially outward. As a result, a recess 56 is formed in the outer peripheral surface of the main body 50 at a portion radially facing the protrusion 54a. A portion of the protrusion 54a fits into the recess 56, and a gap 64 is formed radially between the protrusion 54 and the outer peripheral surface of the main body, which is the inner surface of the recess 56.

[0052] According to the configuration of the above-described alternative example, by increasing the amount by which the protrusion 54 protrudes from the outer peripheral surface of the main body 50, it becomes easier to form a gap 64 in the radial direction between the protrusion 54 and the inner surface of the recess 56, even if the protrusion 54 is bent significantly in the radial direction toward the outer peripheral surface of the main body 50 when the gasket 28 is assembled to the outer can 16. This makes it possible to further improve the ability to remove the electrolyte without reducing the ease with which the gasket 28 can be inserted into the outer can 16. In this example, the other configurations and operations are the same as those of the configurations in FIGS. 1 to 5 .

[0053] Fig. 8 is a view corresponding to Fig. 5 in another example of the embodiment. In the configuration of this example, before the gasket 28c is assembled to the outer can 16, the main body 50 has a protrusion 54b that protrudes radially outward from the outer peripheral surface of the axially inner end, which is the bottom end, all around the circumference.

[0054] The outer diameter of the gasket 28c at a portion including the tip of the protrusion 54b is larger than the inner diameter of the upper tubular portion 30c before it is crimped to the outer can 16. Even if the gasket 28c has this shape before it is assembled to the outer can 16, the protrusion 54 is bent so as to approach the outer circumferential surface of the main body 50 as the gasket 28c is inserted into the open end of the outer can 16, and in this state, the inner surface of the upper tubular portion 30c of the outer can 16 can be urged radially outward. In this example, the other configurations and functions are the same as those in Figures 1 to 5.

[0055] The present disclosure is 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 contains the electrode assembly and an electrolyte; 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 the sealing body is fixed to the open end of the outer can by crimping via the gasket, and the gasket includes a cylindrical main body and a protrusion that protrudes radially outward from the outer peripheral surface of the main body along its entire circumference, and the protrusion is elastically bent axially outward so that its tip approaches the outer peripheral surface of the main body while biasing the inner peripheral surface of the cylindrical portion provided at the open end of the outer can radially outward. Configuration 2: The sealed battery according to Configuration 1, wherein a gap is formed radially between the protrusion and the outer peripheral surface of the main body. Configuration 3: The sealed battery according to Configuration 1 or 2, wherein an annular recess is formed in a portion of the outer peripheral surface of the main body portion radially facing the protrusion, and at least a portion of the protrusion fits into the recess.Configuration 4: The sealed battery according to any one of Configurations 1 to 3, wherein the sealing body has an annular flange portion provided on the outer peripheral side, and the protrusion protrudes from a portion of the outer peripheral surface of the main body portion that is axially more inward than the axially outer surface of the flange portion.Configuration 5: The sealed battery according to Configuration 4, wherein the protrusion protrudes from an axially inner end of the outer peripheral surface of the main body portion.

[0056] REFERENCE SIGNS LIST 10 Sealed battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16, 16a Outer can, 17 Sealing body, 17a Flange portion, 18 Upper insulating plate, 19 Lower insulating plate, 20 Positive electrode tab, 21 Negative electrode tab, 23 Internal terminal plate, 24 Lower valve body, 25 Insulating member, 26 Upper valve body, 27 Cap, 27a Opening, 27b Flange, 27c Cylindrical portion, 28, 28a, 28b, 28c Gasket, 30 Cylindrical portion, 30a, 30c Upper cylindrical portion, 31 Bottom portion, 34 Grooved portion, 38 Radial bend portion, 50 Main body portion, 50a Cylindrical portion, 51 Inner annular plate portion, 52 Outer annular plate portion, 54, 54a, 54b Protrusion portion, 55 Tip, 56 Recess, 61 inner annular plate, 62 cylindrical portion, 63 protrusion, 64 gap, 70 electrolyte.

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 cylindrical outer can with a bottom for accommodating the electrode assembly and an electrolyte; a sealing body for closing an opening of the outer can; and an annular gasket interposed between the outer can and the sealing body, wherein the sealing body is crimped and fixed to the open end of the outer can via the gasket, and the gasket includes a cylindrical main body and a protrusion that protrudes radially outward from an outer circumferential surface of the main body over its entire circumference, and the protrusion is elastically bent axially outward so that its tip approaches the outer circumferential surface of the main body while an inner circumferential surface of a cylindrical portion provided at the open end of the outer can is biased radially outward.

2. The sealed battery according to claim 1, wherein a gap is formed in the radial direction between the protrusion and the outer circumferential surface of the main body.

3. The sealed battery according to claim 1, wherein an annular recess is formed in a portion of the outer circumferential surface of the main body that faces the protrusion in the radial direction, and at least a portion of the protrusion fits into the recess.

4. A sealed battery as described in claim 1, wherein the sealing body has an annular flange portion provided on the outer periphery, and the protrusion protrudes from a portion of the outer periphery of the main body portion that is axially inward from the axial outer surface of the flange portion.

5. The sealed battery according to claim 4, wherein the protrusion protrudes from an axial inner end of the outer circumferential surface of the main body.

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