Gaskets and cylindrical batteries

Abstract

Provided are a highly reliable cylindrical battery and the like which exhibit a small variation in operation pressure of a current cutoff mechanism.　A cylindrical battery (10) comprises a current cutoff mechanism having a sealing body (17) which includes a terminal plate (23) for cutting off flowing of current by being broken. A gasket (28) of the cylindrical battery (10) has, in an independent state before incorporation into an exterior can (16), a cylindrical part and an annular part which extends from an end at a first axial side of the cylindrical part to the radially inner side. The annular part has, at a radially inner side portion of a surface at the first axial side, a recess recessed toward a second axial side.

Description

Technical Field

[0001] The present disclosure relates to gaskets and cylindrical batteries.

Background Art

[0002] Conventionally, there is a cylindrical battery described in Patent Document 1. This cylindrical battery includes an electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, an electrolyte, a bottomed cylindrical outer can that houses the electrode body and the electrolyte, a sealing body, and a sandwiching portion sandwiched between the outer can and the sealing body, and includes an annular gasket that insulates the sealing body from the outer can. The outer can has a protruding portion protruding radially inward on the inner peripheral side by providing a groove extending in the circumferential direction on the outer peripheral surface.

[0003] By bending the end portion on the opening side of the outer can inward and caulking it toward the sealing body side, the sealing body is sandwiched between the protruding portion and the caulked portion of the outer can together with the gasket and fixed to the outer can. The sealing body has a current interruption mechanism. Specifically, when the cylindrical battery generates abnormal heat, gas is generated inside the battery and the internal pressure rises. The current interruption mechanism has a breaking portion that breaks when the internal pressure becomes excessive during abnormal heat generation of the battery, and interrupts the current by breaking the breaking portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inventors of this application have discovered the following problem. Specifically, as shown in Figure 7, the sealing body 317 is crimped during sealing and mounted on the cylindrical battery 310. During crimping, considerable pressure acts on the sealing body 317, gasket 328, and outer casing 316, and the sealing body 317 deforms due to the circumferential stress applied during crimping. That is, during crimping, the valve cap 327 included in the sealing body 317 is subjected to a force radially inward and deforms, causing the inner diameter of the valve cap 327 to decrease, and more specifically, the retaining diameter of the valve cap 327 to decrease inward.

[0006] Against this backdrop, the greater the difference in the inner diameter of the contact surface between the valve cap and the safety valve (rupture valve), the greater the variation in the operating pressure of the current interruption mechanism, leading to a decrease in the reliability of the cylindrical battery. Specifically, if the inner diameter of the valve cap is small and the diameter of the contact area with the safety valve is small, the operating pressure of the current interruption mechanism tends to be high, while if the inner diameter of the valve cap is large and the diameter of the contact area with the safety valve is large, the operating pressure of the current interruption mechanism tends to be low.

[0007] Therefore, the purpose of this disclosure is to provide a gasket that can construct a highly reliable cylindrical battery by reducing variations in the operating pressure of the current interruption mechanism, and a highly reliable cylindrical battery by reducing variations in the operating pressure of the current interruption mechanism. [Means for solving the problem]

[0008] To solve the above problems, the gasket according to the present disclosure is a gasket for a cylindrical battery, comprising a cylindrical portion and an annular portion extending radially inward from the first axial end of the cylindrical portion, wherein the annular portion has a recess on the radially inward side of the first axial side surface that is recessed on the axially second side.

[0009] Furthermore, the cylindrical battery according to the present disclosure comprises an electrode body in which a positive electrode and a negative electrode are wound with a separator between them, an electrolyte, a bottomed cylindrical outer casing that houses the electrode body and the electrolyte, a sealing body, and an annular gasket that includes a clamping portion sandwiched between the outer casing and the sealing body, and insulates the sealing body from the outer casing, wherein the sealing body includes a current interruption mechanism having a rupture portion that interrupts the flow of current when ruptured, and in its standalone state before being assembled into the outer casing, the gasket has a cylindrical portion and an annular portion extending radially inward from the first axial end of the cylindrical portion, and the annular portion has a recess on the radially inward side of the first axial side surface that is recessed on the axially second side.

[0010] The cylindrical portion may have a cylindrical shape or a non-cylindrical shape. For example, the cylindrical portion may have a frustoconical shape, or it may have an annular structure having an inner cylindrical surface and an outer circumferential surface of a frustoconical having the same central axis as the cylindrical portion. In short, the cylindrical portion only needs to have an annular structure in which its minimum inner diameter is greater than the maximum inner diameter of the annular portion. Also, the second side in the axial direction is the opposite side of the first side in the axial direction. Furthermore, the "standalone state before being incorporated into the outer can" refers to the state in which the gasket is not integrated with the sealing body and the outer can, and is in a state in which the gasket exists independently without contacting either the sealing body or the outer can. [Effects of the Invention]

[0011] The gasket according to this disclosure makes it possible to construct a highly reliable cylindrical battery by reducing variations in the operating pressure of the current interruption mechanism. Furthermore, the cylindrical battery according to this disclosure makes it possible to increase the reliability of the battery by reducing variations in the operating pressure of the current interruption mechanism. [Brief explanation of the drawing]

[0012] [Figure 1] This is an axial cross-sectional view of a cylindrical battery according to one embodiment of the present disclosure. [Figure 2] This is a perspective view of the electrode body of the cylindrical battery described above. [Figure 3](a) is an enlarged cross-sectional view of the area around the sealing body of the cylindrical battery before the operation of the current interruption mechanism, and (b) is an enlarged cross-sectional view of the area around the sealing body after the operation of the current interruption mechanism. [Figure 4] This is a cross-sectional view of one side portion of the gasket of the present disclosure, located on one side of the central axis, before it is incorporated into the outer can. [Figure 5] This figure shows the analysis results obtained by using a simulation model to analyze the deformation transition during the crimping process of gaskets for each of the following: a gasket with an annular recess, a gasket from Comparative Example 1 without a recess, and a gasket from Comparative Example 2 without a recess. [Figure 6] This figure shows the simulation results of the cylindrical batteries used in the example, comparative example 1, and comparative example 2, after crimping. [Figure 7] This is a diagram illustrating the crimping process for cylindrical batteries. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments of the gasket and cylindrical battery according to this disclosure will be described in detail with reference to the drawings. The cylindrical battery according to this disclosure may be a primary battery or a secondary battery. Furthermore, the cylindrical battery according to this disclosure may be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. In the following, a non-aqueous electrolyte secondary battery (lithium-ion battery) using a non-aqueous electrolyte will be given as an example of a cylindrical battery 10, which is one embodiment, but the cylindrical battery according to this disclosure is not limited to this.

[0014] In cases where multiple embodiments or modifications are included below, it is anticipated from the outset that new embodiments may be constructed by appropriately combining their characteristic features. In addition, in the following embodiments, the same reference numerals are used for the same components in the drawings, and redundant explanations are omitted. Furthermore, multiple drawings include schematic diagrams, and the dimensional ratios such as length, width, and height of each component do not necessarily match between different drawings. Also, in this specification, for the sake of explanation, the direction along the axial direction of the battery case 15 is defined as the height direction, the side of the sealing body 17 in the height direction is defined as "upper," and the bottom side of the outer casing 16 in the height direction is defined as "lower." Furthermore, among the components described below, components that are not described in the independent claim indicating the highest-level concept are optional components and are not essential components.

[0015] Figure 1 is an axial cross-sectional view of a cylindrical battery 10 according to one embodiment of the present disclosure, and Figure 2 is a perspective view of the electrode body 14 of the cylindrical battery 10. As shown in Figure 1, the cylindrical battery 10 comprises a wound electrode body 14, a non-aqueous electrolyte (not shown), and a battery case 15 that houses the electrode body 14 and the non-aqueous electrolyte. As shown in Figure 2, 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 around the separator 13. Referring again to Figure 1, the battery case 15 consists of a bottomed cylindrical outer casing 16 and a sealing body 17 that closes the opening of the outer casing 16. The cylindrical battery 10 also includes a resin gasket 28 disposed between the outer casing 16 and the sealing body 17.

[0016] A non-aqueous electrolyte comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous solvent may include, for example, esters, ethers, nitriles, amides, and mixtures of two or more of these. The non-aqueous solvent may also contain halogen-substituted solvents in which at least some of the hydrogen atoms in the solvent are replaced with halogen atoms such as fluorine. The non-aqueous electrolyte is not limited to a liquid electrolyte, but may also be a solid electrolyte using a gel-like polymer. Lithium salts such as LiPF6 are used as the electrolyte salt.

[0017] As shown in Fig. 2, the electrode body 14 has a long positive electrode 11, a long negative electrode 12, and two long separators 13. The electrode body 14 also has a positive electrode lead 20 joined to the positive electrode 11 and a negative electrode lead 21 joined to the negative electrode 12. The negative electrode 12 is formed with dimensions slightly larger than those of the positive electrode 11 in order to suppress the precipitation of lithium, and is formed longer than the positive electrode 11 in the longitudinal direction and the width direction (short side direction). Also, the two separators 13 are formed with dimensions at least slightly larger than those of the positive electrode 11 and are arranged, for example, so as to sandwich the positive electrode 11.

[0018] The positive electrode 11 has a positive electrode current collector and positive electrode active material layers formed on both sides of the positive electrode current collector. For the positive electrode current collector, a foil of a metal stable within the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film having such a metal disposed on its surface layer can be used. The positive electrode active material layer contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be produced, for example, by applying a positive electrode active material slurry containing a positive electrode active material, a conductive agent, a binder, etc. onto the positive electrode current collector, drying the coating film, and then compressing it to form the positive electrode active material layers on both sides of the current collector.

[0019] The positive electrode active material is mainly composed of a lithium-containing metal composite oxide. Examples of the metal elements contained in the lithium-containing metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, W, etc. An example of a preferable lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al.

[0020] Examples of the conductive agent contained in the positive electrode active material layer include carbon materials such as carbon black, acetylene black, ketjen black, and graphite. Examples of the binder contained in the positive electrode active material layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide, acrylic resin, and polyolefin. These resins may be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

[0021] The negative electrode 12 has a negative electrode current collector and negative electrode active material layers formed on both surfaces of the negative electrode current collector. As the negative electrode current collector, a foil of a metal stable within the potential range of the negative electrode 12, such as copper or a copper alloy, or a film having such a metal disposed on the surface layer can be used. The negative electrode active material layer contains a negative electrode active material and a binder. The negative electrode 12 can be produced, for example, by applying a negative electrode active material slurry containing a negative electrode active material, a binder, etc. on a negative electrode current collector, drying the coating film, and then compressing it to form negative electrode active material layers on both surfaces of the current collector.

[0022] Generally, a carbon material that reversibly intercalates and deintercalates lithium ions is used as the negative electrode active material. Preferred carbon materials are graphite such as flaky graphite, massive graphite, and earthy graphite, artificial graphite such as massive artificial graphite and graphitized mesophase carbon microbeads. The negative electrode active material layer may contain a Si-containing compound as the negative electrode active material. Further, as the negative electrode active material, a metal that alloys with lithium other than Si, an alloy containing such a metal, a compound containing such a metal, etc. may be used.

[0023] For the binder contained in the negative electrode active material layer, similar to the case of the positive electrode 11, fluororesins, PAN, polyimide resin, acrylic resin, polyolefin resin, etc. may be used, but preferably styrene-butadiene rubber (SBR) or its modified product is used. The negative electrode active material layer may contain, for example, in addition to SBR, CMC or its salt, polyacrylic acid (PAA) or its salt, polyvinyl alcohol, etc.

[0024] A porous sheet having ion permeability and insulating properties is used for the separator 13. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. The material of the separator 13 is preferably polyethylene, olefin resins such as polypropylene, or cellulose. The separator 13 may have either a single-layer structure or a laminated structure. A heat-resistant layer may be formed on the surface of the separator 13. The negative electrode 12 may constitute the winding start end of the electrode body 14, but generally the separator 13 extends beyond the winding start end of the negative electrode 12, and the winding start end of the separator 13 becomes the winding start end of the electrode body 14.

[0025] In the examples shown in Figures 1 and 2, the positive electrode lead 20 is electrically connected to an intermediate part of the positive electrode core, such as the center in the winding direction, and the negative electrode lead 21 is electrically connected to the winding end in the winding direction of the negative electrode core. However, the negative electrode lead may also be electrically connected to the winding start end in the winding direction of the negative electrode core. Alternatively, the electrode body may have two negative electrode leads, with one negative electrode lead electrically connected to the winding start end in the winding direction of the negative electrode core and the other negative electrode lead electrically connected to the winding end in the winding direction of the negative electrode core. Alternatively, the negative electrode and the outer casing may be electrically connected by bringing the winding end side of the negative electrode core in contact with the inner surface of the outer casing.

[0026] As shown in Figure 1, the cylindrical battery 10 further includes an insulating plate 18 positioned above the electrode body 14 and an insulating plate 19 positioned below the electrode body 14. In the example shown in Figure 1, a positive electrode lead 20 attached to the positive electrode 11 extends towards the sealing body 17 through a through-hole in the insulating plate 18, and a negative electrode lead 21 attached to the negative electrode 12 extends towards the bottom 68 of the outer casing 16, passing outside the insulating plate 19. The positive electrode lead 20 is connected by welding or the like to the lower surface of the terminal plate 23, which is the bottom plate of the sealing body 17, and the valve cap 27, which is the top plate of the sealing body 17 and is electrically connected to the terminal plate 23, becomes the positive electrode terminal. The negative electrode lead 21 is connected by welding or the like to the inner surface of the bottom 68 of the outer casing 16, and the outer casing 16 becomes the negative electrode terminal. The structure of the sealing body 17 will be described in detail later.

[0027] The outer casing 16 is a metal container having a bottomed cylindrical section. The outer casing 16 and the sealing body 17 are sealed by an annular gasket 28, which seals the internal space of the battery case 15. The gasket 28 includes a clamping portion 32 that is sandwiched between the outer casing 16 and the sealing body 17, insulating the sealing body 17 from the outer casing 16. The gasket 28 acts as a sealing material to maintain airtightness inside the battery and prevents leakage of electrolyte. The gasket 28 also acts as an insulating material to prevent short circuits between the outer casing 16 and the sealing body 17.

[0028] The outer container 16 has a projection 36 on its inner circumference that protrudes radially inward by providing an annular groove 35 in a part of the height direction of the cylindrical outer surface of the outer container 16. The annular groove 35 can be formed, for example, by spinning a part of the cylindrical outer surface radially inward to create a recess radially inward. The outer container 16 has a bottomed cylindrical portion 30 including the projection 36 and an annular shoulder portion 33. The bottomed cylindrical portion 30 houses the electrode body 14 and the non-aqueous electrolyte, and the shoulder portion 33 is bent radially inward from the opening end of the bottomed cylindrical portion 30 and extends radially inward. The shoulder portion 33 is formed when the upper end of the outer container 16 is bent inward and crimped to the peripheral edge portion 31 of the sealing body 17. The sealing body 17 is secured to the outer can 16 by being crimped together with the gasket 28 between the shoulder portion 33 and the upper side of the protruding portion 36.

[0029] Next, the structure of the sealing body 17 will be described in detail. As shown in Figure 1, the sealing body 17 has a structure in which a terminal plate 23 (an example of a rupture portion), a safety valve 24, an annular insulator 26, and a valve cap 27 are stacked in order from the electrode body 14 side. Each component constituting the sealing body 17 has a disc shape or a ring shape, and each component except the annular insulator 26 is electrically connected. The terminal plate 23 constitutes the bottom plate of the sealing body 17 and has a circular top surface 23a located on substantially the same plane. The terminal plate 23 has an annular thick portion 23b located on the radially outward side and a disc-shaped thin portion 23c that is thinner than the thick portion 23b and is connected to the radially inward annular end of the thick portion 23b.

[0030] The positive lead 20 is connected to the lower surface of the thickened portion 23b of the terminal plate 23 by welding or the like. The safety valve 24 is formed by bending or pressing a metal disc member having approximately the same thickness. The safety valve 24 has an annular portion 24a, an annular stepped portion 24b, and a disc portion 24c. An annular projection 24d is provided on the outer circumference of the annular portion 24a, projecting downwards, and an annular groove 34 exists above the annular projection 24d. The annular stepped portion 24b extends downwards from the radially inner end of the annular portion 24a. The disc portion 24c is provided in the radially central part. The disc portion 24c is connected to the lower end of the annular stepped portion 24b and is located on a plane approximately perpendicular to the height direction. The safety valve 24 has a substantially circular upper surface 24e and an annular projection 24f that protrudes upward in the height direction from the outer edge of the annular portion 24a. Furthermore, the safety valve 24 has a thin-walled portion 24g with a groove that is substantially isosceles triangular in shape, as shown in the cross-sectional view of Figure 1. The reason for providing this thin-walled portion 24g will be explained later.

[0031] As described above, the thin-walled portion 23c of the terminal plate 23 is connected to the lower surface of the disc portion 24c of the safety valve 24 by welding or the like, thereby electrically connecting the terminal plate 23 to the safety valve 24. It is preferable to form the terminal plate 23 and the safety valve 24 from aluminum or an aluminum alloy, as this makes it easy to connect the central portions of the terminal plate 23 and the safety valve 24. As a connection method, metallurgical joining is preferred, and laser welding is an example of metallurgical joining.

[0032] The annular insulator 26 is press-fitted into the inner circumferential surface of the annular projection 24d, and the lower surface of the annular insulator 26 is pressed upward by the upper surface of the thickened portion 23b. The annular insulator 26 is provided to ensure insulation and prevents the thickened portion 23b of the terminal plate 23 from electrically connecting to the safety valve 24. Preferably, the annular insulator 26 is made of a material that does not affect the battery characteristics. Examples of materials for the annular insulator 26 include polymer resins, such as polypropylene (PP) resin and polybutylene terephthalate (PBT) resin.

[0033] As shown in Figure 1, the inner circumferential surface of the annular projection 24d may be a frustoconical shape with an inner diameter decreasing towards the bottom, and the outer circumferential surface of the annular insulator 26 may be a frustoconical shape corresponding to its inner circumferential surface. In such cases, by press-fitting and fixing the annular insulator 26 to the annular projection 24d, misalignment of the annular insulator 26 relative to the annular projection 24d can be reliably prevented.

[0034] The valve cap 27 constitutes the top plate of the sealing body 17 and is circular in plan view. The valve cap 27 can be manufactured, for example, by press-forming a sheet of aluminum or an aluminum alloy. Aluminum and aluminum alloys are preferred materials for the valve cap 27 because they have excellent flexibility. The valve cap 27 has a valve annular portion 27a, an annular bent portion 27b, and a disc portion 27c. The valve annular portion 27a has an annular shape and is provided on the radially outward side. The valve annular portion 27a extends on a plane substantially perpendicular to the height direction. The outer circumferential surface of the valve annular portion 27a abuts the inner circumferential surface of the annular projection 24f of the safety valve 24 by the crimping described above, and a radially inward force is applied from the inner circumferential surface of the annular projection 24f. The annular bent portion 27b bends upward in the height direction from the radially inward end of the valve annular portion 27a and protrudes upward in the height direction. The annular bent portion 27b has a through hole 37. The disc portion 27c is connected to the upper end of the annular bent portion 27b and extends in a plane that is substantially perpendicular to the height direction.

[0035] In the cylindrical battery 10 of this embodiment, the terminal plate 23, safety valve 24, and annular insulator 26 constitute the current interruption mechanism 70. Next, the operation of the current interruption mechanism 70 will be described. Figure 3(a) is an enlarged cross-sectional view of the area around the sealing body 17 before the operation of the current interruption mechanism 70, and Figure 3(b) is an enlarged cross-sectional view of the area around the sealing body 17 after the operation of the current interruption mechanism 70. Note that the positive electrode lead 20 is not shown in Figures 3(a) and (b). As shown in Figure 3(a), when the internal pressure of the cylindrical battery 10 is within the normal range, the upper surface 23a of the terminal plate 23 is spread in a direction substantially perpendicular to the height direction. In response to this, if the cylindrical battery 10 overheats abnormally and its internal pressure rises above a certain value, as shown in Figure 3(b), the portion of the annular portion 24a of the safety valve 24 that is not in contact with the valve cap 27 is pushed upward in the height direction by the high internal pressure, using the radially inward end of the annular portion 24a that is in contact with the valve cap 27 as a fulcrum 29, and bends upward in the height direction. Simultaneously with this upward bending of the annular portion 24a, the fixing portion (welded portion in the case of welding) 39 fixed to the disc portion 24c of the safety valve 24 at the thin-walled portion 23c of the terminal plate 23 springs upward together with the annular portion 24a and is severed from the terminal plate 23.

[0036] This interrupts the current path between the terminal board 23 and the safety valve 24. Furthermore, if the internal pressure rises, the safety valve 24 ruptures at a thin-walled section 24g (see Figure 1) with a triangular cross-section groove and low rigidity, and the gas passes through the safety valve 24 and is then discharged to the outside through the through-hole 37 of the valve cap 27. As a result, even if the cylindrical battery 10 overheats abnormally, the effects of that overheating can be suppressed or prevented from affecting the equipment that houses the cylindrical battery 10, ensuring complete safety and suppressing or preventing damage to the equipment.

[0037] In cylindrical batteries, when the crimping described above is performed, the safety valve is prone to being subjected to excessive force inward, including a radially inward component, which tends to increase the variation in the operating pressure of the current interruption mechanism. In particular, unlike the cylindrical battery 10 shown in Figure 1, where the annular portion 24a of the safety valve 24 extends horizontally, the annular portion of the safety valve may not spread in the orthogonal direction perpendicular to the height direction, but rather become inclined and conform to that orthogonal direction. In such cases, in particular, unlike the cylindrical battery 10 shown in Figure 1, the operating pressure of the current interruption mechanism tends to differ significantly from the desired operating pressure, further reducing the reliability of the cylindrical battery.

[0038] In contrast, when a cylindrical battery 10 is formed using the gasket 28 of this disclosure, the valve annular portion 27a of the valve cap 27 extends horizontally, as shown in Figure 1, and the variation in the operating pressure of the current interruption mechanism 70 is reduced, making it easier to realize a highly reliable cylindrical battery 10. Next, the structure of the gasket 28 of this disclosure, which facilitates the manufacture of such a highly reliable cylindrical battery 10, will be described.

[0039] Figure 4 is a cross-sectional view of one side portion located on one side of the central axis of an annular gasket 28 that facilitates the construction of such a cylindrical battery 10, and is a half-cross-sectional view showing the state of such a gasket 28 before it is assembled into the outer casing 16. As shown in Figure 4, in its standalone state before being assembled into the outer casing 16, the gasket 28 has a cylindrical portion 40 and an annular portion 50 extending radially inward from the first axial side (lower side) end of the cylindrical portion 40. The annular portion 50 has an annular recess 52 recessed on the second axial side (upper side) on the radially inward side of the first axial side (lower side) surface 51.

[0040] The gasket 28 is made of an insulating material, such as a resin material such as polypropylene. It is preferable that the gasket 28 has the dimensions described below when it is in a standalone state before being incorporated into the outer casing 16, as this can more significantly suppress variations in the operating pressure of the current interruption mechanism of the cylindrical battery 10. Specifically, the outer diameter t1 of the gasket 28 is preferably 94 to 98% of the outer diameter of the outer casing 16, and the inner diameter t2 of the gasket 28 is preferably 74 to 78% of the outer casing 16. Furthermore, the material thickness t3 of the cylindrical portion 40 of the gasket 28 is preferably 1 to 4% of the material thickness of the outer casing 16. Furthermore, the gasket height t4 is preferably 2 to 10 mm, the material thickness of the annular portion 50 (axial height of the annular portion 50) t5 is preferably 17 to 22% of the gasket height t4, and the depth of the recess 52 (axial height) t6 is preferably 20 to 30% of the material thickness of the annular portion 50 (axial height of the annular portion 50) t5. In addition, it is preferable that at least a portion of the recess 52 is located at a position of 80 to 88% of the outer diameter with respect to the radial direction of the gasket 28.

[0041] [Exam Overview] The inventors of this application measured the variation in the operating pressure of the current interruption mechanism between 20 cylindrical batteries 10 made using 20 gaskets that satisfy the above dimensions, and 20 cylindrical batteries made using 20 gaskets that differed only in that the recess 52 was not formed in those 20 gaskets, and obtained the following results.

[0042] <Measurement of operating pressure of current interruption mechanism> The operating pressure was measured by utilizing the discrete increase in electrical resistance when the weld between the terminal plate and the safety valve breaks. The terminal plate is welded to the safety valve, but the area below the sealing body is sealed, and the internal pressure of this sealed space is increased. While measuring the internal pressure of the sealed space, the electrical resistance of the valve cap and terminal plate was measured as the internal pressure increased. The internal pressure at which the resistance value increased by 1Ω or more was defined as the operating pressure of the current interruption mechanism.

[0043] <Test Results> The variation in operating pressure σ (standard deviation) of the current interruption mechanism in a cylindrical battery fabricated using the current gasket without the recess 52 was 0.07. On the other hand, the variation in operating pressure σ (standard deviation) of the current interruption mechanism in a cylindrical battery 10 fabricated using the gasket with the recess 52 was 0.03. Therefore, it was confirmed that fabricating a cylindrical battery using the current gasket without the recess 52 significantly reduces the variation in operating pressure σ (standard deviation) of the current interruption mechanism.

[0044] Next, we will qualitatively explain why variations in the operating pressure of the current interruption mechanism in a cylindrical battery 10, which is manufactured using a gasket having a recess 52 regardless of the various dimensions of the gasket described above, can be suppressed.

[0045] Figure 5 shows the results of an analysis using a simulation model to examine the deformation transitions during the crimping process of gaskets 28, 128, and 228, respectively, for gasket 28 with an annular recess 52, gasket 128 of Comparative Example 1 without a recess, and gasket 228 of Comparative Example 2 without a recess.

[0046] Referring to Figure 5, during the crimping process, a diagonal downward and inward force, indicated by arrow A, acts from the shoulder portion of the outer can 16, 116, 216 through the gaskets 28, 128, 228 to the peripheral edge of the sealing body 17, 117, 217, and a diagonal upward and inward force, indicated by arrow B, acts from the protruding portion of the outer can 16, 116, 216 through the gaskets 28, 128, 228 to the peripheral edge of the sealing body 17, 117, 217. In this context, as shown in the gasket 128 of Comparative Example 1 and the gasket 228 of Comparative Example 2, if there is no recess on the radially inward lower side of the annular portion of the gaskets 128, 228, the lower compression portions 128a, 228a that are in contact with the protruding portion of the gaskets 128, 228 cannot be released.

[0047] Therefore, when the thickness of the lower compression portion 128a of the gasket 128 is large, as in the gasket 128 of Comparative Example 1, the diagonal upward and inward force shown by arrow B becomes large, and as shown in the figure after crimping, the valve annular portion 127a of the valve cap 127 of the sealing body 117 tends to bend upward as it goes radially outward. Conversely, when the thickness of the lower compression portion 228a of the gasket 228 is small, as in the gasket 228 of Comparative Example 2, the diagonal downward and inward force shown by arrow A becomes large, and as shown in the figure after crimping, the valve annular portion 227a of the valve cap 227 of the sealing body 217 tends to bend downward as it goes radially outward.

[0048] In contrast, when a recess 52 exists on the lower radially inward side of the annular portion of the gasket 28, as in the gasket 28 of the embodiment, a portion of the material of the lower compression portion 28a can be released into the recess 52 during crimping, thereby reducing the diagonally downward and inward force indicated by arrow A and the diagonally upward and inward force indicated by arrow B. Therefore, excessive diagonally downward and inward forces and excessive diagonally upward and inward forces acting on the valve annular portion 27a of the valve cap 27 of the sealing body 17 can be suppressed, and as shown in the figure after crimping in the embodiment, the valve annular portion 27a of the valve cap 27 of the sealing body 17 becomes more likely to expand in a direction perpendicular to the height direction, and as a result, variations in the operating pressure of the current interruption mechanism can be suppressed.

[0049] <Regarding the sealing properties of the cylindrical battery in this disclosure> Furthermore, the inventors of this application confirmed through stress analysis using a simulation model that the cylindrical battery of this disclosure also has good gasket sealing performance. Figure 6 shows the simulation results of the stress distribution after crimping for each of the cylindrical batteries of the example, comparative example 1, and comparative example 2 used in the analysis of Figure 5.

[0050] In Figure 6, the white areas indicate low stress areas, the gray areas indicate medium stress areas, and the black areas indicate high stress areas. As shown in Figure 6, the simulation results confirmed that in all three examples (Example, Comparative Example 1, and Comparative Example 2), particularly high stress areas k1, k2, l1, l2, m1, and m2 extended along the space between the shoulder of the outer casing and the gasket, and between the upper side of the protrusion of the outer casing and the gasket. Therefore, it was confirmed that even if a recess 52 is formed on the lower radially inward side of the annular portion 50 of the gasket 28, the sealing performance of the gasket 28 in the cylindrical battery 10 can be made as good as that of a cylindrical battery using a gasket without a recess.

[0051] As described above, the gasket 28 is a gasket for the cylindrical battery 10. The gasket 28 comprises a cylindrical portion 40 and an annular portion 50 extending radially inward from the first axial side (lower side) end of the cylindrical portion 40. The annular portion 50 has a recess 52 on the radially inward side of the first axial side surface 51, recessed on the second axial side (upper side).

[0052] Therefore, during the crimping process, the material of the lower compression portion 28a can be released into the recess 52, and variations in the radially inward force acting on the peripheral edge of the sealing body 17 during the crimping process can be suppressed. Thus, variations in the current interruption mechanism 70 can be reduced, making it possible to manufacture a highly reliable cylindrical battery 10, and moreover, a cylindrical battery 10 with excellent sealing performance of the gasket 28 can be manufactured.

[0053] Furthermore, in the standalone state before the gasket 28 is assembled into the outer can 16, the axial dimension of the annular portion 50 may be 17% to 22% of the total axial length of the gasket 28. Also, in the standalone state before the gasket 28 is assembled into the outer can 16, the depth of the recess 52 may be 20% to 30% of the axial dimension of the annular portion 50. Furthermore, in the standalone state before the gasket 28 is assembled into the outer can 16, at least a portion of the recess 52 may be located at a position 80% to 88% of the outer diameter of the gasket 28 in the radial direction.

[0054] By adopting these configurations, variations in the current interruption mechanism 70 can be further reduced, making it possible to manufacture a cylindrical battery 10 with even greater reliability.

[0055] Furthermore, the cylindrical battery 10 comprises an electrode body 14 in which a positive electrode 11 and a negative electrode 12 are wound via a separator 13, an electrolyte, a bottomed cylindrical outer casing 16 housing the electrode body 14 and the electrolyte, a sealing body 17, and an annular gasket 28 that insulates the sealing body 17 from the outer casing 16, including a clamping portion 32 that is sandwiched between the outer casing 16 and the sealing body 17. The sealing body 17 also includes a current interruption mechanism 70 having a terminal plate (break portion) 23 that interrupts the flow of current when broken. Furthermore, in its standalone state before being assembled into the outer casing 16, the gasket 28 has a cylindrical portion 40 and an annular portion 50 extending radially inward from the first axial end of the cylindrical portion 40, and the annular portion 50 has a recess 52 on the radially inward side of the first axial side surface 51 that is recessed on the axial side.

[0056] Therefore, the variation in the operating pressure of the current interruption mechanism 70 in the cylindrical battery 10 can be reduced, thereby increasing reliability.

[0057] Furthermore, the sealing body 17 may have a valve cap 27 whose second axial side (upper side) surface is exposed to the outside. The valve cap 27 may also have an annular valve ring portion 27a located radially outward from the outer can 16 and extending in a direction substantially perpendicular to the height direction.

[0058] As described above, when the valve cap 27 has an annular valve ring portion 27a that extends in a direction substantially perpendicular to the height direction, as explained with reference to Figure 5, an appropriate force of not excessive magnitude acts radially inward on the peripheral edge of the sealing body 17 during the crimping process. Therefore, the operating pressure of the current interruption mechanism 70 of the cylindrical battery 10 can be made significantly less variable, the reliability of the cylindrical battery 10 can be made significantly higher, and the sealing performance of the cylindrical battery 10 can be made even better.

[0059] This disclosure is not limited to the embodiments and their modifications, and various improvements and modifications are possible within the scope of the claims of this application and their equivalents.

[0060] For example, while the description described a case where the axial dimension of the annular portion 50 is 17% to 22% of the total axial length of the gasket 28 when the gasket 28 is in its standalone state before being assembled into the outer can 16, the axial dimension of the annular portion does not have to be 17% to 22% of the total axial length of the gasket. Also, while the description described a case where the depth of the recess 52 is 20% to 30% of the axial dimension of the annular portion 50 when the gasket 28 is in its standalone state before being assembled into the outer can 16, the depth of the recess does not have to be 20% to 30% of the axial dimension of the annular portion. Furthermore, while the description described a case where at least a part of the recess 52 is located at 80% to 88% of the outer diameter of the gasket 28 in the radial direction when the gasket 28 is in its standalone state before being assembled into the outer can 16, the entire recess does not have to be located at 80% to 88% of the outer diameter of the gasket in the radial direction.

[0061] Furthermore, although the case where the recess 52 is annular has been described, the recess provided on the radially inward side of the first axial side surface of the annular portion of the annular gasket, so as to be recessed on the axially second side, does not have to be annular.

[0062] For example, an annular gasket, in its standalone state before being incorporated into the outer can, may have multiple identical recesses on the radially inward side of the first axial side surface of its annular portion, which are spaced equally in the circumferential direction and recessed on the second axial side, or it may have multiple non-identical recesses spaced equally in the circumferential direction and recessed on the second axial side.

[0063] Alternatively, the annular gasket, in its standalone state before being incorporated into the outer can, may have a plurality of identical recesses on the radially inward side of the first axial side surface of its annular portion, which are located at non-equally spaced intervals in the circumferential direction and recessed on the second axial side, or it may have a plurality of non-identical recesses located at non-equally spaced intervals in the circumferential direction and recessed on the second axial side.

[0064] Alternatively, the annular gasket, in its standalone state before being incorporated into the outer can, may have only one recess on the radially inward side of the first axial side surface of its annular portion, which is recessed to the second side and has a C-shape when viewed from one side (bottom) in the height direction.

[0065] In short, an annular gasket, in its standalone state before being assembled into the outer can, only needs to have one or more recesses on the radially inward side of the first axial side surface of its annular portion, with the second recess being recessed on the second side, and these one or more recesses can take any form.

[0066] Furthermore, although the case in which the valve annular portion 27a of the valve cap 27 extends on a plane substantially perpendicular to the height direction (axial direction) has been described, in the cylindrical battery of this disclosure, the valve annular portion of the valve cap may have a portion that is inclined with respect to a plane substantially perpendicular to the height direction (axial direction).

[0067] Furthermore, the case in which the cylindrical battery 10 has a current interruption mechanism 70 that interrupts the current by breaking the terminal plate 23 has been described. However, the current interruption mechanism of the cylindrical battery can be any mechanism that interrupts the flow of current by breaking the breakable part. Therefore, the current interruption mechanism of the cylindrical battery is not limited to the mechanism described above, but can be any of the many types of current interruption mechanisms currently known, or any other mechanism that interrupts the flow of current by breaking the breakable part. [Explanation of Symbols]

[0068] 10 Cylindrical battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Battery case, 16 Outer casing, 17 Sealing body, 18,19 Insulating plate, 20 Positive electrode lead, 21 Negative electrode lead, 23 Terminal plate, 23a Top surface, 23b Thick-walled section, 23c Thin-walled section, 24 Safety valve, 24a Annular section, 24b Stepped section, 24c Disc section, 24d Annular projection, 24e Top surface, 24f Annular projection, 24g Thin-walled section, 26 Annular insulator, 27 Valve cap, 27a Valve annular section, 27b Annular bend section, 27c Disc section, 28 Gasket, 28a Lower compression section, 30 Bottomed cylindrical portion, 31 Peripheral portion, 32 Clamping portion, 33 Shoulder portion, 35 Annular groove, 36 Protruding portion, 37 Through hole, 40 Cylindrical portion, 50 Annular portion, 51 First axial side (lower side) surface of the annular portion, 52 Recess, 70 Current interruption mechanism.

Claims

1. An annular gasket used in a cylindrical battery comprising an electrode body in which a positive electrode and a negative electrode are wound with a separator between them, an electrolyte, a bottomed cylindrical outer casing that houses the electrode body and the electrolyte and has an annular groove recessed radially inward along the entire circumference, and a sealing body, wherein the annular gasket is disposed between the outer casing and the sealing body to insulate the sealing body from the outer casing, A cylindrical part, An annular portion extending radially inward from the first axial end of the cylindrical portion, Equipped with, The annular portion has a recess on the radially inward side of the first side surface in the axial direction, which is recessed on the second side in the axial direction. A gasket in which the sealing body is axially sandwiched between the upper surface of the annular groove and the shoulder of the outer can via the gasket, and the portion of the annular part where the recess is provided in the annular part contacts the upper surface of the annular groove of the outer can.

2. The gasket according to claim 1, wherein the axial dimension of the annular portion is 17% to 22% of the total length in the axial direction.

3. The gasket according to claim 1 or 2, wherein the depth of the recess is 20 to 30% of the axial dimension of the annular portion.

4. The gasket according to any one of claims 1 to 3, wherein at least a portion of the recess is located at a position of 80 to 88% of the outer diameter with respect to the radial direction.

5. A cylindrical battery comprising: an electrode body in which a positive electrode and a negative electrode are wound with a separator between them; an electrolyte; a bottomed cylindrical outer container housing the electrode body and the electrolyte; a sealing body; and an annular gasket that includes a clamping portion sandwiched between the outer container and the sealing body, and insulates the sealing body from the outer container, The sealing body includes a current interruption mechanism having a break portion that interrupts the flow of current when broken, A cylindrical battery, in its standalone state before being incorporated into the outer casing, having a cylindrical portion and an annular portion extending radially inward from the first axial end of the cylindrical portion, wherein the annular portion has a recess on the radially inward side of the first axial side surface that is recessed on the second axial side, and when the cylindrical portion is crimped, the portion of the annular portion with the recess provided in it contacts the upper surface of the annular groove of the outer casing.

6. The sealing body has a valve cap on which the second side surface in the axial direction is exposed to the outside, The cylindrical battery according to claim 5, wherein the valve cap is located radially outward of the outer casing and has an annular valve ring portion that extends in a direction substantially perpendicular to the height direction.

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