Power storage device

Abstract

This power storage device includes: a terminal plate (21) that is positioned above an electrode body when a bottom section of a case (20) is treated as the lower end, and has a body section (21b) electrically connected to a first electrode of the electrode body, and a fragile section (21c) positioned between the body section (21b) and a connecting section (21a) to the inside thereof; a sealing plate (22) that is positioned above the terminal plate (21) and is electrically connected to the connecting section (21a); and a gasket (30) that is sandwiched between an opening of the case (20) and the sealing plate (22). The gasket (30) includes an annular upper portion (31), and a lower portion (32) that is provided below the upper portion (31) and has a retention section (33) contacting a lower surface of the body section (21b) of the terminal plate (21). The distance in the radial direction between the fragile section (21c) and the retention section (33) is smaller than the distance in the radial direction between the fragile section (21c) and the outermost periphery of the body section (21b).

Description

Power storage device

[0001] The present disclosure relates to an electricity storage device.

[0002] A secondary battery has been known as an energy storage device, comprising an electrode assembly, a cylindrical case with a bottom that houses the electrode assembly, and a sealing body that closes the opening of the case. The electrode assembly is connected to the sealing body via an electrode tab, allowing the sealing body to function as an electrode terminal. Patent Document 1 also describes a secondary battery in which a gasket supports the lower surface of the outer periphery of a current interrupting member (terminal plate) that faces the electrode assembly. Another gasket is also placed above this gasket, and the upper and lower surfaces of the outer periphery of the current interrupting member and the outer periphery are enclosed by the two gaskets.

[0003] Japanese Patent Application Laid-Open No. 2008-204839

[0004] In the configuration described in Patent Document 1, the gasket only supports the underside of the outer periphery of the terminal plate, so there is room for improvement in terms of protecting the notch-forming portion, which is a weak portion of the terminal plate, from external impact or vibration. As a result, in the configuration described in Patent Document 1, if the secondary battery is subjected to external impact or vibration, the weak portion may break, causing the battery to lose its function.

[0005] Therefore, an object of the present disclosure is to provide a highly reliable power storage device.

[0006] The energy storage device according to the present disclosure includes a cylindrical case having an opening and a bottom located below the opening, an electrode body located within the case and having a first electrode and a second electrode having a polarity different from that of the first electrode, a terminal plate located above the electrode body when the bottom is considered as the lower end and having a main body portion electrically connected to the first electrode, a connection portion connected to the main body portion, and a fragile portion located between the main body portion and the connection portion, a sealing plate located above the terminal plate and electrically connected to the connection portion, and a gasket sandwiched between the opening of the case and the sealing plate, wherein the gasket includes an annular upper portion sandwiched between the opening of the case and the sealing plate, and a lower portion provided below the upper portion and having a retaining portion that contacts the underside of the main body portion of the terminal plate, and the radial distance between the fragile portion and the retaining portion is smaller than the radial distance between the fragile portion and the outermost periphery of the main body portion.

[0007] According to the present disclosure, the reliability of the power storage device can be increased.

[0008] 10 is an axial cross-sectional view of an electric storage device according to an embodiment of the present disclosure. FIG. 1 is an enlarged view of an upper portion of FIG. 1. FIG. 2A is an enlarged view of a portion A of FIG. 2A. It is a diagram showing a state before a gasket constituting the electric storage device of FIG. 1 is attached to a case, where (a) is a top view and (b) is a cross-sectional view taken along B-B. It is a diagram showing a state before a gasket constituting an electric storage device of another example of the embodiment is attached to a case, where (a) is a top view and (b) is a cross-sectional view taken along C-C. It is a top view showing a state before a gasket constituting an electric storage device of another example of the embodiment is attached to a case. It is a top view showing a state before a gasket constituting an electric storage device of another example of the embodiment is attached to a case. It is a top view showing a state before a gasket constituting an electric storage device of another example of the embodiment is attached to a case. It is a diagram corresponding to FIG. 2A of an electric storage device of another example of the embodiment. It is a cross-sectional view showing a state before two gaskets constituting the electric storage device of FIG. 8 are attached to a case. It is a diagram corresponding to FIG. 2A of an electric storage device of another example of the embodiment. It is a top view showing a state before a gasket constituting the electric storage device of FIG. 10 is attached to a case. 13 is a top view showing a state before a gasket constituting an electric storage device according to another example of an embodiment is attached to a case. FIG. 14 is a view corresponding to FIG. 2A of an electric storage device according to another example of an embodiment. FIG. 15 is a top view showing a state before a gasket constituting the electric storage device of FIG. 13 is attached to a case. FIG. 16 is a top view showing a state before a gasket constituting an electric storage device according to another example of an embodiment is attached to a case. FIG. 17 is a top view showing a state before a gasket constituting an electric storage device according to another example of an embodiment is attached to a case. FIG. 18 is a view corresponding to FIG. 2A of an electric storage device according to another example of an embodiment.

[0009] Hereinafter, an embodiment of the power storage device according to the present disclosure will be described in detail with reference to the drawings. The power storage device according to the present disclosure may be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. The power storage device according to the present disclosure may also be a capacitor. Below, a cylindrical secondary battery will be described as the power storage device according to the embodiment, but the power storage device according to the present disclosure is not limited to a cylindrical secondary battery, and various configurations can be adopted as long as it is a power storage device including a cylindrical case having an opening and a bottom and an electrode body disposed in the case.

[0010] 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 denoted by the same reference numerals in the drawings, and redundant description will be omitted. Furthermore, the drawings include schematic diagrams, and the dimensional ratios of the length, width, height, and other dimensions of each component do not necessarily match between different drawings. In this specification, the axial opening side of the case 20 of the cylindrical secondary battery 10 is referred to as "upper," and the axial bottom 20b side is referred to as "lower." That is, the bottom 20b of the case 20 will be described as the lower end. The energy storage device disclosed herein does not necessarily only cover devices in which the bottom of the case is positioned vertically below the opening when in use. For example, the bottom of the case may be configured vertically above the opening when in use. 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.

[0011] FIG. 1 is an axial cross-sectional view of a secondary battery 10, which is an energy storage device of an embodiment. FIG. 2A is an enlarged view of an upper portion of FIG. 1. FIG. 2B is an enlarged view of portion A of FIG. 2A. The axial cross-sectional view of FIG. 1 shows a cross section including the central axis of the secondary battery 10. As shown in FIG. 1, the secondary battery 10 includes a cylindrical case 20 having an opening 20e and a bottom 20b, an electrode assembly 14, a non-aqueous electrolyte, a sealing body 19 that closes the opening 20e of the case 20, and a gasket 30. The case 20 is a cylindrical metal container with a bottom, inside which the electrode assembly 14 and the non-aqueous electrolyte are disposed. The sealing body 19 includes a sealing plate 22 located at the upper end.

[0012] The electrode body 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 positive electrode 11 corresponds to a first electrode. The negative electrode 12 corresponds to a second electrode having a polarity different from that of the first electrode. The first electrode may be a negative electrode, and the second electrode may be a positive electrode. The case 20 has a cylindrical portion 20a having an opening, and a bottom portion 20b located at the lower end.

[0013] 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 secondary 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.

[0014] 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 cylindrical secondary battery or improving input characteristics, the non-aqueous 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 non-aqueous electrolyte.

[0015] 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.).

[0016] 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-shaped 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] 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.

[0018] 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.

[0019] 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.

[0020] 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 ２ The 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.

[0021] Insulating plates 15 and 16 are disposed above and below the electrode body 14. In the example shown in FIG. 1 , a positive electrode tab 17, which is an electrode tab connected to the positive electrode 11, passes through a through-hole in the insulating plate 15 and extends toward the sealing plate 22. A negative electrode tab 18 attached to the negative electrode 12 passes outside the insulating plate 16 and extends toward the bottom 20b of the case 20. The positive electrode tab 17 and the negative electrode tab 18 are each formed into a long plate shape using a conductive material. The positive electrode tab 17 is joined by welding or the like to the underside of a terminal plate 21 (described below), which is the inner surface of the sealing body 19 facing the inside of the case 20. The center of the terminal plate 21 is electrically connected to the sealing plate 22. This allows the sealing plate 22 to function as a positive electrode terminal. The negative electrode tab 18 is connected by welding or the like to the inner surface of the bottom 20b of the case 20, allowing the case 20 to function as a negative electrode terminal. The negative electrode tab 18 may be provided in a ribbon or band shape. The electrode tab is joined to the main body portion 21b.

[0022] An annular gasket 30 is interposed between the case 20 and the sealing plate 22 to ensure the sealing of the inside of the battery and the insulation between the case 20 and the sealing plate 19 .

[0023] At the upper end portion, which is the end portion on the opening side of the case 20, a radially bent portion 20c is formed that is bent radially inward along the entire circumference, and the sealing plate 22 is thereby fixed to the upper end portion of the case 20 by crimping via a gasket 30. In this way, the sealing plate 22 is fixed to the axially inner side of the upper end portion of the case 20.

[0024] An annular grooved portion 24 is provided on the upper end side, which is the axial opening end side, of the cylindrical portion 20a of the case 20, closer to the bottom portion 20b than the radially bent portion 20c. The grooved portion 24 is a portion that protrudes radially inward around the entire circumference in a portion adjacent to the lower side of the opening-side cylindrical portion 20d provided on the upper end side of the cylindrical portion 20a of the case 20. The grooved portion 24 is formed by recessing a portion of the cylindrical portion 20a radially inward by, for example, spinning. The grooved portion 24 supports the sealing plate 22 via the gasket 30.

[0025] 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.

[0026] The sealing body 19, including the sealing plate 22, is a disc-shaped member equipped with a current interruption mechanism and is disposed above the electrode body 14. The sealing body 19 has a structure in which, from the electrode body 14 side, a terminal plate 21, an insulating plate 23, and the sealing plate 22 are stacked. The terminal plate 21 is annular and has a main body portion 21b to the underside of which the positive electrode tab 17 is joined, and a disc-shaped connecting portion 21a provided in the center of the terminal plate 21 and connected to the main body portion 21b at its outer periphery. This electrically connects the main body portion 21b to the positive electrode 11. The connecting portion 21a is a thin portion that is thinner than the main body portion 21b. Note that the connecting portion 21a and the main body portion 21b may have the same thickness.

[0027] 2B, between main body portion 21b and connecting portion 21a, weakened portion 21c, which is thinner than the central portion of connecting portion 21a, is located. Weak portion 21c is formed as a thin annular portion on the upper surface of terminal board 21 by an annular slit 21d formed between connecting portion 21a and main body portion 21b.

[0028] 2A , third through-holes 21 g are formed in a plurality of positions (e.g., six positions) around the circumference of main body 21 b, and each third through-hole 21 g is circular or has an arc shape along the circumference of main body 21 b. An annular stepped surface 21 f is formed around the entire circumference of the lower surface of the outer periphery of main body 21 b, recessed upward.

[0029] Insulating plate 23 is a disk-shaped member made of an insulating material and has an opening 23a in the center. Sealing plate 22 is disposed opposite terminal plate 21 with insulating plate 23 interposed between them. The center of sealing plate 22 is connected by welding or the like to connecting portion 21a in the center of terminal plate 21 through opening 23a of insulating plate 23, thereby establishing electrical continuity. In this way, insulating plate 23 is sandwiched between sealing plate 22 and terminal plate 21.

[0030] At multiple positions (e.g., six positions aligned in the circumferential direction) on insulating plate 23, fourth through holes 23b having a shape similar to that of third through holes 21g are formed at positions aligned with third through holes 21g of terminal plate 21. Furthermore, a tubular hook 23c protruding downward and tilting radially inward is formed on the outer periphery of the lower surface of insulating plate 23. Hook 23c is pressed against outer periphery 21e of terminal plate 21. The tip of hook 23c engages with the lower surface of stepped surface 21f of terminal plate 21. As a result, the outer periphery of terminal plate 21 is enclosed by insulating plate 23. In other words, there is no direct contact between the outer periphery of terminal plate 21 and sealing plate 22.

[0031] The insulating plate 23 can be made of insulating resin or insulating metal. Examples of such resins include thermosetting resins such as phenolic resin, epoxy resin, and unsaturated polyester resin, and thermoplastic resins such as polyphenylene sulfide resin (PPS), polyimide resin (PI), polyamide-imide resin, polyetherimide resin (PAI), and fluororesin such as polytetrafluoroethylene (PTFE). Alternatively, the insulating plate 23 may be made of thermoplastic resins such as polypropylene (PP) and polybutylene terephthalate (PBT).

[0032] Examples of metals that can be used to form the insulating plate 23 include stainless steel and iron. The metal can be insulated by coating the metal with an insulating resin, such as polyimide resin or polypropylene resin.

[0033] Sealing plate 22 is disposed above terminal plate 21. Sealing plate 22 has separation portion 22b located above the fragile portion of terminal plate 21 and ring portion 22c surrounding separation portion 22b, and the outermost periphery of separation portion 22b and ring portion 22c are connected by easy-to-break portion 22a ( FIG. 2A ) located in the radially intermediate portion of sealing plate 22.

[0034] The easily breakable portion 22a is a ring-shaped thin portion formed by a ring-shaped groove formed on the inner surface (the lower surface in FIG. 2A ) of the sealing plate 22. The pressure inside the case 20 acts on the ring-shaped groove of the sealing plate 22 through the third through-hole 21g and the fourth through-hole 23b, which are vent holes formed in the terminal plate 21 and the insulating plate 23.

[0035] A ring-shaped protrusion 22d that protrudes downward is formed at the radially intermediate portion of the lower surface of the ring portion 22c of the sealing plate 22. The protrusion 22d is inclined radially inward as it approaches the bottom. The protrusion 22d presses against the outer peripheral surface 21e, which is the side surface of the terminal plate 21, via the hook portion 23c of the insulating plate 23. As a result, as described below, not only does the gasket 30 support the main body portion 21b of the terminal plate 21 from below, but the sealing plate 22 also supports the outer peripheral portion of the terminal plate 21, thereby further suppressing vibrations transmitted to the fragile portion 21c of the terminal plate 21.

[0036] When the pressure (internal pressure) inside the case 20 rises and reaches or exceeds a predetermined threshold, the second predetermined pressure described below, the sealing plate 22 deforms outward, the easily breakable portion 22a is cut, and the radially inner portion (separation portion 22b) of the easily breakable portion 22a moves away from the case 20.

[0037] In the secondary battery 10, the terminal plate 21, to which the positive electrode tab 17 is connected, is electrically connected to the sealing plate 22, thereby forming a current path from the electrode body 14 to the sealing plate 22. If an abnormality such as overcharging occurs in the battery and the internal pressure rises above a first predetermined pressure, the terminal plate 21 breaks, and the connection portion 21a of the terminal plate 21 is separated from the outer main body portion 21b and deforms to become convex toward the outside of the battery. As a result, the secondary battery 10 is configured so that the portion of the terminal plate 21 to which the positive electrode tab 17 is connected is electrically disconnected from the sealing plate 22, thereby interrupting the current path. If the internal pressure of the battery further rises above a second predetermined pressure that is greater than the first predetermined pressure, the frangible portion 22a breaks as described above, forming an opening for venting gas inside the battery. The gas released from this opening is discharged to the outside of the battery through an opening at the top of the battery. Therefore, after fragile portion 21c of terminal plate 21 is cut and main body portion 21b and connecting portion 21a of terminal plate 21 are separated, at least a portion of fragile portion 22a of sealing plate 22 is cut, and separating portion 22b and ring portion 22c are separated at least a portion of the continuous portion (fragile portion 22a) between them. Therefore, after current is interrupted by cutting fragile portion 21c, gas inside the battery can be released to the outside, thereby providing a more reliable secondary battery 10.

[0038] 3A and 3B are diagrams showing the state of the gasket 30 before it is attached to the case 20, with Fig. 3A being a top view and Fig. 3B being a cross-sectional view taken along the line B-B. As shown in Fig. 3, the gasket 30 includes an annular upper portion 31 and a double annular lower portion 32 that is integrally formed below the upper portion 31 and continues radially inward from the lower end of the upper portion 31.

[0039] As shown in FIG. 3 , before the gasket 30 is attached to the case 20, the upper portion 31 is cylindrical. The lower portion 32 includes an annular portion 51 extending radially inward from the lower end of the upper portion 31, a retaining portion 33 that is a circular annular portion arranged inside the annular portion 51 and has the same central axis, and a plurality of (four in the illustrated example) radially extending connecting portions 36 that connect the annular portion 51 and the retaining portion 33. The connecting portions 36 are preferably arranged to contact the lower surface of the terminal board 21, similar to the retaining portions 33. This allows the lower surface of the main body portion 21b, which is located near the fragile portion 21c of the terminal board 21, to be supported, thereby making it easier to protect the fragile portion 21c from external impact or vibration.

[0040] A circular first through hole 34 is formed inside the retaining portion 33. Four second through holes 35 are formed between the retaining portion 33 and the annular portion 51 between two adjacent connecting portions 36 in the circumferential direction. The four second through holes 35 are arc-shaped along the same circumferential direction and have a width in the radial direction. As a result, the retaining portion 33 is located between the first through hole 34 and the second through hole 35. In particular, the retaining portion 33 is located between the first through hole 34 and the second through hole 35 in the radial direction. Note that by changing the number of connecting portions 36, the number of second through holes 35 can be two, three, five or more.

[0041] 2A and 2B , when gasket 30 is assembled to case 20, upper portion 31 is sandwiched between the opening of case 20 and sealing plate 22. At this time, upper portion 31 of gasket 30 is pressed into the inside of the tip (opening side end) of case 20, which simply extends cylindrically, until it abuts against grooved portion 24, and then the tip of case 20 is crimped radially inward. As a result, the upper end of upper portion 31 is sandwiched between radially bent portion 20c of case 20 and the upper surface of the outer periphery of sealing plate 22, and the outer periphery of annular portion 51 is sandwiched between the upper surface of grooved portion 24 of case 20 and the lower surface of the outer periphery of sealing plate 22.

[0042] Furthermore, the retaining portion 33 faces and contacts the lower surface of the portion of the main body 21b of the terminal plate 21 that is radially inward from the third through holes 21g, supporting the terminal plate 21 from below. The portion of the upper end of the positive electrode tab 17 that extends above the upper insulating plate 15 is bent into a U-shape below the terminal plate 21. The upper surface of the tip of the positive electrode tab 17 is joined by welding or the like to a portion of the main body 21b of the terminal plate 21 that is radially inward from the third through holes 21g, at a position different from the retaining portion 33 of the gasket 30. At this time, the positive electrode tab 17 is joined to the main body 21b of the terminal plate 21 at the lower portion 32, passing through the inside of the second through hole 35 that is radially outward from the retaining portion 33, as shown by the two-dot chain line in FIG. 3( a). The two-dot chain line in FIG. 3( a ) shows the state of the positive electrode tab 17 after the upper end of the positive electrode tab 17 is joined to the terminal plate 21 but before it is bent.

[0043] The radial distance d1 ( FIG. 2B ) between the fragile portion 21c of the terminal plate 21 and the retaining portion 33 of the gasket 30 in the secondary battery 10, more specifically, the radial distance d1 in the case 20, is smaller than the radial distance d2 ( FIG. 2A ) between the fragile portion 21c and the outermost periphery of the main body portion 21b. As a result, unlike the configuration described in Patent Document 1, in which the gasket supports only the underside of the outer periphery of the terminal plate, the retaining portion 33 can support the underside of the main body portion 21b located near the fragile portion 21c of the terminal plate 21, thereby making it easier to protect the fragile portion 21c from external impact or vibration. This ensures both current interruption when the internal pressure of the secondary battery 10 increases and impact and vibration resistance. This improves the reliability of the secondary battery 10. Furthermore, in this example, the radial distance d1 (FIG. 2B) of the secondary battery 10 between the fragile portion 21c of the terminal board 21 and the retaining portion 33 of the gasket 30 is smaller than the distance d4, which is half the radial distance d2 (FIG. 2A) between the fragile portion 21c and the outermost periphery of the main body portion 21b. This allows the retaining portion 33 to support the underside of the main body portion 21b, which is located closer to the fragile portion 21c of the terminal board 21, making it easier to protect the fragile portion 21c from external impact or vibration.

[0044] Furthermore, the retaining portion 33 is located radially between the first through hole 34 and the second through hole 35. The lower surface of the connecting portion 21a of the terminal plate 21 communicates with the space in the secondary battery 10 where the electrode assembly 14 is disposed through the inside of the first through hole 34. The lower surface of the outer periphery of the separating portion 22b of the sealing plate 22 communicates with the space in which the electrode assembly 14 is disposed through the second through hole 35, the third through hole 21g of the terminal plate 21, and the fourth through hole 23b of the insulating plate 23. This makes it easier to position the retaining portion 33, which supports the fragile portion 21c, closer to the fragile portion 21c while enabling current interruption when the internal pressure of the secondary battery 10 increases. This improves the impact resistance and vibration resistance of the secondary battery 10.

[0045] Furthermore, when the secondary battery 10 is configured to include an insulating plate 23 formed of resin and sandwiched between the sealing plate 22 and the terminal plate 21, even if external vibrations are applied to the sealing plate 22, the vibrations transmitted to the fragile portion 21c of the terminal plate 21 are absorbed by the insulating plate 23, making the terminal plate 21 (fragile portion 21c) less likely to be damaged.

[0046] Furthermore, in this example, terminal board 21 has third through hole 21g, and the radial distance d1 ( FIG. 2B ) between weak portion 21c of terminal board 21 and retaining portion 33 is smaller than the radial distance d3 ( FIG. 2B ) between weak portion 21c and third through hole 21g. Here, the radial distance between weak portion 21c and third through hole 21g refers to the shortest distance between weak portion 21c and the inner end of through hole 21g in the radial direction of terminal board 21. This allows retaining portion 33 of gasket 30 to suppress vibrations transmitted to weak portion 21c at a position closer to weak portion 21c of terminal board 21. This further reduces unintended damage to weak portion 21c.

[0047] FIG. 4 shows a gasket 30a constituting a secondary battery, which is a power storage device according to another embodiment, before being attached to a case 20. (A) is a top view, and (B) is a cross-sectional view taken along the line C-C. In this example, the lower portion 32 of the gasket 30a is integral with the upper portion 31 by continuing radially inward from the lower end of the upper portion 31. The lower portion 32 includes an annular portion 51 and two parallel, linear retaining portions 33a. An upwardly protruding protrusion 52 is formed on the upper surface of each of the two retaining portions 33a. Two protrusions 52 are provided, spaced apart in the longitudinal direction of the retaining portion 33a. Each protrusion 52 is cylindrical with a hemispherical portion at its upper end. The protrusions may be cylindrical with a flat upper end, or rectangular.

[0048] Inside the annular portion 51, first through holes 34a are formed inside the two retaining portions 33a. When viewed in the axial direction, the first through holes 34a have a generally rectangular shape with arcs at both ends. More specifically, the first through holes 34a have a shape obtained by cutting both ends of a circle. Inside the annular portion 51, for each retaining portion 33a, a second through hole 35a is formed on the opposite side of the first through hole 34a. When viewed in the axial direction, each second through hole 35a has a shape similar to the end of a circle, surrounded by an arc and a chord, and is smaller than a semicircle. Each second through hole 35a has the same shape. This allows the first through holes 34a and the second through holes 35a to have different shapes. Furthermore, the first through holes 34a are larger than the second through holes 35a.

[0049] When the gasket 30a is attached to the case 20, the upper ends of the projections 52 face and contact the lower surface of the main body 21b of the terminal board 21, as shown by the two-dot chain line in Figure 4(b). As a result, the projections 52 press against the lower surface of the terminal board 21.

[0050] According to the configuration of this example, the contact pressure between each holding portion 33a and the underside of the terminal board 21 can be increased, so that the terminal board 21 can be held more firmly and it becomes easier to prevent misalignment of the contact portion between the holding portion 33a and the terminal board 21.

[0051] Furthermore, in this example, second through holes 35a are formed in the lower portion 32 of the gasket 30a between each protrusion 52 and the outer peripheral surface of the gasket 30a, penetrating vertically. The second through holes 35a also correspond to sixth through holes. As a result, even if the cylindrical outer peripheral surface of the gasket 30a is deformed by crimping the case 20, the deformation of the second through holes 35a can mitigate the effect of the deformation on the positional accuracy of the protrusions 52. This makes it difficult for the position of each protrusion 52 to change, and each protrusion 52 can more easily support the vicinity of the fragile portion 21c of the terminal board 21. Other configurations and functions of this example are similar to those of FIGS. 1 to 3.

[0052] 5 is a top view showing a state of a gasket 30b constituting a secondary battery, which is an energy storage device, according to another example of the embodiment, before it is attached to the case 20. In this example, the lower portion 32 of the gasket 30b includes a substantially disk-shaped retaining portion 33b that is integrally formed by continuing radially inward from the lower end of the upper portion 31. A first through-hole 34a that is substantially rectangular when viewed in the axial direction is formed in a portion including the center of the retaining portion 33b.

[0053] When gasket 30b is attached to case 20, the upper surfaces of two separated portions of retaining portion 33b, separated by a first through-hole 34a near the center, face and contact the lower surface of main body portion 21b (FIGS. 2A and 2B) of terminal board 21. As a result, retaining portion 33b presses against the lower surface of terminal board 21, supporting terminal board 21 from below. In this manner, gasket 30b may be configured with only one through-hole 34a. In this example, the other configurations and functions are the same as those in FIGS. 1 to 3.

[0054] 6 is a top view showing a state of a gasket 30c constituting a secondary battery, which is an electricity storage device, according to another example of the embodiment, before it is attached to the case 20. In this example, the lower portion 32 provided on the gasket 30c includes a substantially circular annular portion 51 that is integrally provided by continuing radially inward from the lower end of the upper portion 31, and linear holding portions 33c that extend radially to connect both lateral ends of the inner surface of the annular portion 51.

[0055] Two through holes, a first through hole 61 and a second through hole 62, separated by a retaining portion 33c, are formed inside the annular portion 51. As a result, the retaining portion 33c is located between the first through hole 61 and the second through hole 62. When viewed in the axial direction, each of the through holes 61, 62 has a shape that is only one side of a circle, is surrounded by an arc and a chord, and is smaller than a semicircle. Each of the through holes 61, 62 has the same shape.

[0056] When gasket 30c is attached to case 20, the upper surfaces of two portions of retaining portion 33c that are spaced apart from each other near the center face and contact the lower surface of main body portion 21b (FIGS. 2A and 2B) of terminal board 21. As a result, retaining portion 33c presses against the lower surface of terminal board 21, supporting terminal board 21 from below. In this way, gasket 30c may be configured to have only two through holes 61, 62. In this example, the other configurations and functions are the same as those in FIGS. 1 to 3.

[0057] 7 is a top view showing a gasket 30d constituting a secondary battery, which is an electricity storage device, according to another example of the embodiment, before being attached to the case 20. In this example, the shape of the gasket 30d is the same as that of the gasket 30a shown in FIG. 4, except that the protrusions 52 are omitted.

[0058] With gasket 30d attached to case 20, the upper surface of each holding portion 33a faces and contacts the lower surface of main body 21b (FIGS. 2A and 2B) of terminal board 21. As a result, each holding portion 33a presses against the lower surface of terminal board 21, supporting terminal board 21 from below. In this example, other configurations and functions are the same as those in FIGS. 1 to 3.

[0059] Fig. 8 is a view corresponding to Fig. 2A of a secondary battery 10a which is a power storage device according to another embodiment of the present invention. Fig. 9 is a cross-sectional view showing the state before two gaskets 30e constituting the secondary battery 10a are attached to the case 20.

[0060] In this example, the upper portion 37 and the lower portion 38 of the gasket 30 are provided as separate members. The upper portion 37 is annular, and more specifically, has a circular plate shape.

[0061] The lower portion 38 includes a cylindrical portion 38a facing the outer periphery of the lower surface of the upper portion 37, a substantially disk-shaped annular portion 51 connected to the cylindrical portion 38a so as to extend radially from the inner surface of the lower end of the cylindrical portion 38a, a circular holding portion 33 inside the annular portion 51, and a plurality of (e.g., four) connecting portions 36 arranged radially to connect the annular portion 51 and the holding portion 33. The upper portion 37 of this example has the same shape as the upper end portion of the upper portion 31 in the configuration of Figures 1 to 3. The lower portion 38 of this example has the same shape as the cylindrical portion of the upper portion 31 and the lower portion 32 in the configuration of Figures 1 to 3, which are connected in the vertical direction.

[0062] When assembling the gasket 30e to the case 20, the lower portion 38 of the gasket 30e is pushed into the inside of the cylindrically extending tip (opening end) of the case 20 until it abuts against the grooved portion 24. Then, the sealing body 19 is placed inside the tip of the case 20 so as to rest on the outer periphery of the annular portion 51 of the lower portion 38. Furthermore, with the upper portion 37 resting on the upper side of the outer periphery of the top surface of the sealing plate 22 and the upper side of the cylindrical portion 38a of the lower portion 38, the tip of the case 20 is crimped radially inward. As a result, the upper portion 37 is sandwiched between the radially bent portion 20c of the case 20 and the upper surface of the outer periphery of the sealing plate 22. Furthermore, the outer periphery of the annular portion 51 is sandwiched between the grooved portion 24 of the case 20 and the lower surface of the outer periphery of the sealing plate 22.

[0063] Similar to the configurations shown in Figures 1 to 3, the holding portion 33 is the main body portion 21b of the terminal board 21, and faces and contacts the underside of the portion radially inward from the plurality of third through holes 21g, thereby supporting the terminal board 21 from below.

[0064] In this way, in this example, because the gasket 30e is divided into two components, the number of curved portions of the gasket 30e can be reduced. This makes the gasket 30e less susceptible to breakage. Note that in this example, the outer periphery of the lower surface of the upper portion 37 and the upper end of the cylindrical portion 38a of the lower portion 38 are in contact with each other when the gasket 30e is assembled to the case 20. However, this configuration is not limited thereto, and the outer periphery of the lower surface of the upper portion 37 and the upper end of the cylindrical portion 38a of the lower portion 38 may be spaced apart when assembled.

[0065] Furthermore, in this example, the upper portion 37 and the lower portion 38 of the gasket 30e may be made of different materials, with the upper portion 37 being made of a material with greater heat resistance than the lower portion 38. For example, the upper portion 37 may be made of a resin with higher heat resistance than the lower portion 38. In this case, by welding a tab (not shown) for connecting to an external device, for example, to the upper surface of the radially bent portion 20c after the case 20 is crimped, the gasket 30e can easily maintain its functionality even when heat is applied. Furthermore, even if the tip of the case 20 is crimped radially inward while heated, the gasket 30e is less likely to be damaged. In either case, since the entire gasket 30e does not need to be made of a highly heat-resistant material, costs can be reduced. Furthermore, the lower portion 38 can be made of a material more suitable for holding the terminal board 21. In this example, the other configurations and functions are similar to those of FIGS. 1 to 3. In this example, the gasket may be divided into three or more members.

[0066] Fig. 10 is a view corresponding to Fig. 2A of a secondary battery 10b which is a power storage device according to another embodiment. Fig. 11 is a top view showing a state before a gasket 30f constituting the secondary battery 10b is attached to the case 20.

[0067] In this example, in the configuration of Fig. 6, upwardly projecting protrusions 39 are formed at two positions spaced apart in the longitudinal direction on the upper surface of the holding portion 33c. Each protrusion 39 is cylindrical.

[0068] Furthermore, two third through holes 21h having a shape that can fit with each protrusion 39 are formed in terminal board 21 at positions facing each protrusion 39. Two other through holes (not shown) having shapes similar to the shapes of through holes 61, 62 when viewed in the axial direction are formed in terminal board 21 at positions axially facing two through holes 61, 62 of gasket 30c. Each third through hole 21h is a circular hole. Insulating plate 23 has a circular fourth through hole 23d axially facing third through hole 21h, and two other through holes (not shown) axially facing the other through holes of terminal board 21 and having shapes similar to the shapes of through holes 61, 62 when viewed in the axial direction.

[0069] As shown in FIG. 10 , when the gasket 30f and the sealing body 19 are assembled inside the opening of the case 20, the upper surface of the retaining portion 33c of the gasket 30f faces and contacts the lower surface of the main body portion 21b of the terminal board 21, supporting the terminal board 21 from below. Furthermore, the two protrusions 39 of the gasket 30f are fitted into the two third through-holes 21h of the terminal board 21. The engagement of the protrusions 39 of the gasket 30f with the third through-holes 21h suppresses rotation of the terminal board 21 and prevents circumferential displacement of the gasket 30f and the terminal board 21 from the proper positional relationship. Other configurations and functions of this example are the same as those of FIGS. 1 to 3 or the configuration of FIG. 6 . The protrusions 39 may be polygonal pillars, such as rectangular pillars. The third through-holes 21h that fit with the protrusions 39 may be polygonal holes when viewed in the axial direction, matching the shape of the protrusions 39. Furthermore, third through-hole 21h may be a hole having a shape different from the shape of protrusion 39 when viewed in the axial direction, as long as it can fit onto protrusion 39 to prevent rotation of terminal board 21.

[0070] Furthermore, in this example, the protrusion of the gasket 30f is not limited to being formed on the upper surface of the retaining portion 33c, but may be formed on the upper surface of the annular portion 51, and the protrusion may be configured to fit into the third through hole of the terminal board 21.

[0071] Fig. 12 is a top view showing a state before a gasket 30g constituting a secondary battery, which is a power storage device according to another embodiment, is attached to a case 20. In this example, in the configuration shown in Fig. 5, the gasket 30 includes two protrusions 39 protruding upward from positions on either side of the first through-hole 34a on the upper surface of the holding portion 33b. The two protrusions 39 of the gasket 30g are fitted into two third through-holes 21h (Fig. 10) formed in the terminal board 21. In this example, the other configurations and functions are the same as those shown in Figs. 1 to 3, Fig. 5, or Figs. 10 and 11.

[0072] Fig. 13 is a diagram corresponding to Fig. 2A of a secondary battery 10c which is a power storage device according to another embodiment. Fig. 14 is a top view showing a state before a gasket 30h constituting the secondary battery 10c is attached to a case 20.

[0073] 10 and 11, upwardly projecting protrusions 41 are formed on the upper surface of the holding portion 33c at two positions spaced apart in the longitudinal direction. Each protrusion 41 is generally cylindrical, with the diameter of the outer circumferential surface increasing upward. Note that the outer circumferential surface of each protrusion 41 may be simply cylindrical, with the diameter remaining constant throughout the axial direction, or may be polygonal, such as rectangular.

[0074] Furthermore, each protrusion 41 is formed with a fifth through hole 42 that penetrates in the vertical direction, and the lower end of the fifth through hole 42 leads to the underside of the lower portion 32 of the gasket 30h. Each protrusion 41 is fitted into the third through hole 21h of the terminal plate 21 and the fourth through hole 23d of the insulating plate 23. In this configuration, the pressure of gas generated on the electrode body 14 side inside the case 20 can be applied to the underside of the sealing plate 22 through the through hole 42 of each protrusion 41.

[0075] Furthermore, in this example, the protrusions 41 of the gasket 30h are fitted into the third through-hole 21h of the terminal board 21 and the fourth through-hole 23d of the insulating board 23, thereby suppressing rotation of the terminal board 21 and the insulating board 23 and preventing circumferential displacement of the gasket 30 from the proper positional relationship with the terminal board 21 and the insulating board 23. In this example, the other configurations and functions are the same as those in Figures 1 to 3 or Figures 10 and 11.

[0076] FIG. 15 is a top view showing a gasket 30i constituting a secondary battery, which is a power storage device according to another embodiment, before it is attached to the case 20. In this example, in the configuration shown in FIG. 12 , the gasket 30i includes two protrusions 41 protruding upward from positions on either side of the first through-hole 34a on the upper surface of the holding portion 33. The two protrusions 41 of the gasket 30i are fitted into two third through-holes 21h ( FIG. 13 ) formed in the terminal board 21 and a fourth through-hole 23d ( FIG. 13 ) in the insulating plate 23. Each protrusion 41 of the gasket 30i is formed with a fifth through-hole 42 penetrating vertically, and the lower end of the fifth through-hole 42 communicates with the lower surface of the lower portion 32 of the gasket 30i. Other configurations and functions of this example are similar to those of FIGS. 1 to 3 , 12 , 13 , and 14 .

[0077] 16 is a top view showing a state before a gasket 30j constituting a secondary battery, which is an energy storage device according to another embodiment, is attached to a case 20. In this example, a sixth through-hole 43 is formed in a disk-shaped retaining portion 33b constituting the lower portion 32 of the gasket 30j, penetrating vertically between each protrusion 39 and the outer circumferential surface of the gasket 30j. The sixth through-hole 43 has an arc shape that roughly follows the outer circumferential surface of the retaining portion 33 and has a width in the radial direction. Note that the sixth through-hole 43 may have various shapes, including a rectangular shape when viewed vertically, as long as it does not interfere with the protrusions 39 and does not reach the outer circumferential surface of the retaining portion 33.

[0078] According to the configuration of this example, even if the outer peripheral surface of the gasket 30i is deformed by crimping the case 20, the deformation of the outer peripheral surface can mitigate the effect of the deformation on the positional accuracy of the protrusions 39 by the deformation of the sixth through holes 43. This makes it difficult for the positions of the protrusions 39 to change, and makes it easier for the protrusions 39 to fit into the third through holes 21h ( FIG. 10 ) of the terminal board 21. In this example, other configurations and functions are the same as those of the configurations of FIGS. 10 and 11 or 12 .

[0079] 17 is a top view showing a state of a gasket 30k constituting a secondary battery that is an electricity storage device according to another example of the embodiment before it is attached to the case 20. In this example, sixth through holes 43 are formed in the disk-shaped holding portion 33b constituting the lower portion 32 of the gasket 30k so as to penetrate in the vertical direction between each protrusion 41 and the outer peripheral surface of the gasket 30k.

[0080] According to the configuration of this example, even if the outer peripheral surface of gasket 30k is deformed by crimping case 20, the deformation of the outer peripheral surface can mitigate the effect on the positional accuracy of the protrusions due to the deformation of the outer peripheral surface, by the deformation of sixth through hole 43. This makes it difficult for the positions of each protrusion 41 to change, and each protrusion 41 can easily fit into third through hole 21h ( FIG. 13 ) of terminal board 21 and fourth through hole 23d ( FIG. 13 ) of insulating plate 23. In this example, other configurations and functions are the same as those of the configurations of FIGS. 13 , 14 , and 15 .

[0081] 18 is a diagram corresponding to FIG. 2A of a secondary battery 10d, which is a power storage device according to another embodiment. In this example, the terminal plate 55 does not have a disk portion with a thinner central portion on the underside than the other portions. Specifically, the vertical thickness of the disk-shaped connecting portion 56 provided at the center of the terminal plate 55 is the same as the vertical thickness of the annular plate-shaped main body portion 57 provided radially outward from the connecting portion 56.

[0082] The outer peripheral surface of the connecting portion 56 and the inner peripheral surface of the main body portion 57 are welded together at a weld in the vertical middle portion. This weld forms an annular weakened portion 59 that is thinner than the main body portion 57 in the vertical middle portion between the connecting portion 56 and the main body portion 57.

[0083] The upper surface of the holding portion 33c that constitutes the lower portion 32 of the gasket 30c and extends in the radial direction faces and contacts the lower surfaces of the main body 57 and the connecting portion 56. As a result, the holding portion 33c supports the vicinity of the fragile portion 59 of the terminal board 55 from below. The shape of the gasket 30c itself is the same as the configuration shown in FIG. 6.

[0084] Furthermore, the radial distance of the secondary battery 10d between the fragile portion 59 of the terminal plate 55 and the retaining portion 33c of the gasket 30c is approximately zero, and this distance is smaller than the radial distance d2a between the fragile portion 59 and the outermost periphery of the main body portion 57 of the terminal plate 55. As a result, unlike when the gasket 30c supports only the underside of the outer periphery of the terminal plate 55, the retaining portion 33c can support the underside of the main body portion 57 and the underside of the connection portion 56, which are located near the fragile portion 59 of the terminal plate 55, thereby making it easier to protect the fragile portion 59 from external impact or vibration. Furthermore, in this example, the radial distance of the secondary battery 10 between the fragile portion 59 of the terminal plate 55 and the retaining portion 33c of the gasket 30c is smaller than the distance d4a, which is half the radial distance d2a between the fragile portion 59 and the outermost periphery of the main body portion 57. This allows the holding portion 33c to support the underside of the main body portion 57, which is located closer to the fragile portion 59 of the terminal board 55, thereby making it easier to protect the fragile portion 59 from external shock or vibration. In this example, the other configurations and functions are the same as those in FIGS. 1 to 3 or the configuration in FIG. 6.

[0085] The present disclosure will be further described by the following embodiments. Configuration 1: A cylindrical case (20) having an opening (20e) and a bottom (20b) located below the opening (20e), an electrode body (14) arranged in the case (20) and having a first electrode (11, 12) and a second electrode (11, 12) having a polarity different from that of the first electrode (11, 12), and a terminal plate (21, 55) arranged above the electrode body (14) when the bottom (20b) is the lower end, and having a main body (21b, 57) electrically connected to the first electrode (11, 12), a connection part (21a, 56) connected to the main body (21b, 57), and a fragile part (21c, 59) located between the main body (21b, 57) and the connection part (21a, 56). a sealing plate (22) disposed above the terminal plate (21, 55) and electrically connected to the connection portion (21a, 56); and a gasket (30) sandwiched between the opening (20e) of the case (20) and the sealing plate (22), wherein the gasket (30) includes: an annular upper portion (31) sandwiched between the opening (20e) of the case (20) and the sealing plate (22); and a lower portion (32) provided below the upper portion (31) and having a retaining portion (33) in contact with a lower surface of the main body portion (21b, 57) of the terminal plate (21, 55), and the radial distance between the fragile portion (21c, 59) and the retaining portion (33) is smaller than the radial distance between the fragile portion (21c, 59) and the outermost periphery of the main body portion (21b, 57). An electric storage device (10, 10a, 10b, 10c, 10d). Configuration 2: The electric storage device (10, 10a, 10b, 10c, 10d) according to Configuration 1, wherein a first through hole (34, 34a, 61) and a second through hole (35) are provided at mutually different positions in the lower portion (32) of the gasket (30, 30a, 30c, 30d, 30e, 30f, 30h, 30j, 30k), and the holding portion (33) is located between the first through hole (34, 34a, 61) and the second through hole (35, 35a, 62, 43).Configuration 3: The electricity storage device (10, 10a, 10b, 10c, 10d) according to Configuration 1 or 2, further comprising an insulating plate (23) made of resin and sandwiched between the sealing plate (22) and the terminal plate (21, 55). Configuration 4: The electricity storage device (10, 10a, 10b, 10c, 10d) according to Configuration 3, further comprising an electrode tab (17) connecting the terminal plate (21, 55) and the first electrode (11, 12), wherein when pressure inside the case (20) increases, the fragile portion (21c, 59) is cut, and a portion of the terminal plate (21, 55) to which the electrode tab (17) is connected is electrically disconnected from the sealing plate (22), and the sealing plate (22) has a separation portion (22b) located above the fragile portion (21c, 59), a ring portion (22c) surrounding the separation portion (22b), and an easy-to-break portion (22a) provided between the separation portion (22b) and the ring portion (22c), and the easy-to-break portion (22a) is cut after the fragile portion (21c, 59) is cut. Configuration 5: The electric storage device (10, 10a, 10b, 10c, 10d) according to any one of Configurations 1 to 4, wherein the terminal board (21, 55) has a third through hole (21g, 21h), and a radial distance between the fragile portion (21c, 59) and the holding portion (33, 33c) is smaller than a radial distance between the fragile portion (21c, 59) and the third through hole (21g, 21h). Configuration 6: The energy storage device (10, 10a, 10b, 10c, 10d) according to Configuration 4, wherein the ring portion (22c) of the sealing plate (22) includes a convex portion (22d) protruding downward, the insulating plate (23) includes a hook portion (23c) protruding downward, and the convex portion (22d) of the sealing plate (22) presses against a side surface of the terminal plate (21, 55) via the hook portion (23c) of the insulating plate (23).Configuration 7: The energy storage device according to any one of Configurations 1 to 4, wherein the holding portion (33) includes a protrusion (39, 41) protruding upward, and the protrusion (39, 41) presses against a lower surface of the terminal plate (21, 55).Configuration 8: The electricity storage device according to any one of Configurations 1 to 4, wherein the lower portion (38) includes a protrusion (39, 41) protruding upward, the terminal plate has a third through hole (21h), and the protrusion (39, 41) is fitted into the third through hole (21h).Configuration 9: The electricity storage device according to Configuration 3 or 4, wherein the lower portion (38) includes a protrusion (39, 41) protruding upward, the terminal plate (21, 55) has a third through hole (21g, 21h), the insulating plate (23) has a fourth through hole (23b), and the protrusion (39, 41) is fitted into the third through hole (21g, 21h) and the fourth through hole (23b). Configuration 10: The electricity storage device according to Configuration 2, wherein the upper portion (37) and the lower portion (38) of the gasket (30) are formed as separate members, and the lower portion (38) includes the retaining portion (33, 33c) and the first through hole (34, 34a, 61). Configuration 11: The electricity storage device according to Configuration 10, wherein the upper portion (37) and the lower portion (38) of the gasket (30) are formed of different materials, and the material forming the upper portion (37) has a higher heat resistance than the material forming the lower portion (38). Configuration 12: The electricity storage device according to Configuration 9, wherein the protrusion (39, 41) of the lower portion (38) is provided with a fifth through hole (42) penetrating in the vertical direction. Configuration 13: The electricity storage device according to Configuration 7, 8, or 9, wherein the lower portion (38) is provided with a sixth through hole (43), and the sixth through hole (43) is disposed between the protrusions (39, 41) of the lower portion (38) and the outer peripheral surface of the gasket (30). Configuration 14: The electricity storage device according to Configuration 2, wherein the first through hole (34) of the gasket (30) is larger than the second through hole (35). Configuration 15: The electricity storage device according to Configuration 2, wherein the first through hole (34) and the second through hole (35) of the gasket (30) have different shapes.

[0086] 10, 10a, 10b, 10c, 10d 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 Sealing body, 20 Case, 20a Cylindrical portion, 20b Bottom portion, 20c Radial bending portion, 20d Opening side cylindrical portion, 20e Opening, 21 Terminal plate, 21a Connection portion, 21b Main body portion, 21c Fragile portion, 21d Slit, 21e Outer circumferential surface, 21f Step surface, 21g, 21h Third through hole, 22 Sealing plate, 22a Easily breakable portion, 22b Separation portion, 22c Ring portion, 22d Convex portion, 23 Insulating plate, 23a Opening, 23b, 23d Fourth through hole, 23c Hook portion, 24 Grooved portion, 30, 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, 30k Gasket, 31 Upper portion, 32 Lower portion, 33, 33a, 33b, 33c Holding portion, 34 First through hole, 35 Second through hole, 36 Connecting portion, 37 Upper portion, 38 Lower portion, 39, 41 Protrusion, 42 Fifth through hole, 43 Sixth through hole, 51 Annular portion, 52 Protrusion, 55 Terminal board, 56 Connection portion, 57 Main body portion, 59 Fragile portion, 60 First through hole, 62 Second through hole.

Claims

1. An energy storage device comprising: a cylindrical case having an opening and a bottom located below the opening; an electrode body located within the case and having a first electrode and a second electrode having a polarity different from that of the first electrode; a terminal plate located above the electrode body when the bottom is considered to be the lower end, the terminal plate having a main body portion electrically connected to the first electrode, a connection portion connected to the main body portion, and a fragile portion located between the main body portion and the connection portion; a sealing plate located above the terminal plate and electrically connected to the connection portion; and a gasket held between the opening of the case and the sealing plate, the gasket including an annular upper portion held between the opening of the case and the sealing plate, and a lower portion provided below the upper portion and having a holding portion in contact with the underside of the main body portion of the terminal plate, the radial distance between the fragile portion and the holding portion being smaller than the radial distance between the fragile portion and the outermost periphery of the main body portion.

2. The energy storage device according to claim 1, wherein a first through hole and a second through hole are provided at mutually different positions in the lower portion of the gasket, and the retaining portion is located between the first through hole and the second through hole.

3. The electricity storage device according to claim 1, further comprising an insulating plate sandwiched between the sealing plate and the terminal plate and made of resin.

4. The energy storage device according to claim 3, further comprising an electrode tab that electrically connects the terminal plate and the first electrode, and configured such that when pressure inside the case increases, the fragile portion is cut off, and the portion of the terminal plate to which the electrode tab is connected is electrically disconnected from the sealing plate, and the sealing plate has a separation portion located above the fragile portion, a ring portion that surrounds the separation portion, and an easily breakable portion provided between the separation portion and the ring portion, and the easily breakable portion is cut after the fragile portion is cut.

5. The electric storage device according to any one of claims 1 to 4, wherein the terminal plate has a third through hole, and the radial distance between the weak portion and the holding portion is smaller than the radial distance between the weak portion and the third through hole.

6. The energy storage device according to claim 4, wherein the ring portion of the sealing plate includes a convex portion that protrudes downward, the insulating plate includes a hook portion that protrudes downward, and the convex portion of the sealing plate presses against a side surface of the terminal plate via the hook portion of the insulating plate.

7. The electricity storage device according to any one of claims 1 to 4, wherein the holding portion includes a protrusion that protrudes upward, and the protrusion presses against the lower surface of the terminal board.

8. The energy storage device according to any one of claims 1 to 4, wherein the lower portion includes a protrusion that protrudes upward, the terminal plate has a third through hole, and the protrusion is fitted into the third through hole.

9. The energy storage device according to claim 3 or 4, wherein the lower portion includes a protrusion that protrudes upward, the terminal plate has a third through hole, the insulating plate has a fourth through hole, and the protrusion is fitted into the third through hole and the fourth through hole.

10. The energy storage device according to claim 2, wherein the upper and lower portions of the gasket are formed as separate members, and the lower portion includes the retaining portion and the first through-hole.

11. The energy storage device according to claim 10, wherein the upper and lower portions of the gasket are made of different materials, and the material forming the upper portion has a higher heat resistance than the material forming the lower portion.

12. The electricity storage device according to claim 9, wherein the protrusion of the lower portion is provided with a fifth through-hole that penetrates in the vertical direction.

13. The energy storage device according to claim 7, wherein the lower portion is provided with a sixth through-hole, and the sixth through-hole is disposed between the protrusion of the lower portion and the outer peripheral surface of the gasket.

14. The electricity storage device according to claim 2, wherein the first through-hole of the gasket is larger than the second through-hole.

15. The electricity storage device according to claim 2, wherein the first through-hole and the second through-hole of the gasket have different shapes.

Images