Cylindrical battery

Abstract

A cylindrical battery (10) comprises an electrode body (14) in which a positive electrode (11) and a negative electrode (12) are wound with a separator (13) therebetween, a bottomed cylindrical external can (16) which accommodates the electrode body (14), and a sealing body (17) which seals an opening of the external can (16). A bottom part (40) of the external can (16) has a reverse part (43) which has a raised shape such that the reverse part (43) protrudes toward the electrode body (14) in the axial direction and which reverses when the pressure inside the battery reaches a first pressure. The sealing body (17) has a sealing plate (27) which releases gas that is inside the battery by breaking when the pressure inside the battery reaches a second pressure that is higher than the first pressure. The sealing plate (27) functions as a safety valve.

Description

Technical Field

[0001] The present disclosure relates to a cylindrical battery.

Background Art

[0002] Conventionally, there is a cylindrical battery described in Patent Document 1. This cylindrical battery includes a sealing body having a sealing plate, a metal plate as an internal terminal plate, and an insulating member interposed between the sealing plate and the metal plate. This cylindrical battery seals the inside by caulking and fixing the sealing body through a resin gasket to the opening of a bottomed cylindrical metal outer can. The sealing plate of this cylindrical battery is provided with an inclined portion that is displaced outward in the axial direction and whose thickness continuously decreases as it goes radially from the inner peripheral portion to the outer peripheral portion. When the internal pressure of this cylindrical battery rises due to abnormal heat generation, the safety mechanism operates. Specifically, when the internal pressure rises due to abnormal heat generation in this cylindrical battery, the inclined portion of the sealing plate is inverted and the current path inside the battery is interrupted. Further, when the internal pressure further rises, the inclined portion breaks and the gas inside the battery is discharged to the outside. The sealing plate functions as a safety valve.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a wound electrode body, the gas generated on the electrode plate flows out from both end faces in the axial direction of the electrode body. When a safety valve is provided in the sealing body that seals the opening of the outer can, the gas that has flowed out from the end face on the bottom side of the electrode body diffuses into the hollow portion and the inner side of the side surface of the electrode body. The gas that has diffused into the hollow portion of the electrode body can reach the safety valve without damaging the outer can, but the gas that has diffused outside the electrode body may cause damage to the side surface of the outer can, such as generating a through hole in the side surface of the outer can.

[0005] In this context, if a cylindrical battery overheats abnormally, and high-temperature gas is ejected from the side of the outer casing other than the safety valve, for example, in a battery pack containing multiple cylindrical batteries, the high-temperature gas may cause damage to surrounding cylindrical batteries or equipment.

[0006] Therefore, the purpose of this disclosure is to provide a cylindrical battery that is less susceptible to damage to its sides in the event of abnormal overheating, and that allows high-temperature gas to be smoothly exhausted to the outside through a safety valve. [Means for solving the problem]

[0007] To solve the above problems, the cylindrical battery of this disclosure comprises an electrode body in which a positive electrode and a negative electrode are wound with a separator between them, a bottomed cylindrical outer casing that houses the electrode body, and a sealing body that seals the opening of the outer casing. The bottom of the outer casing has a convex shape that protrudes toward the electrode body in the axial direction and has a reversal part that reverses when the internal pressure of the battery reaches a first pressure. The sealing body has a safety valve that ruptures when the internal pressure of the battery reaches a second pressure greater than the first pressure to release gas from inside the battery. [Effects of the Invention]

[0008] According to the cylindrical battery described herein, in the event of abnormal overheating, the sides are less likely to be damaged, and high-temperature gas can be easily and smoothly exhausted to the outside through a safety valve. [Brief explanation of the drawing]

[0009] [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] This is an enlarged cross-sectional view of the area surrounding the sealing body of the cylindrical battery described above. [Figure 4] This diagram illustrates the reversal operation of the sealing plate of the cylindrical battery described above. [Figure 5] This diagram illustrates the reversal operation of the reversal section of the cylindrical battery described above. [Figure 6] This is a cross-sectional view corresponding to Figure 1 of a modified cylindrical battery. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the cylindrical battery according to this disclosure will be described in detail with reference to the drawings. The cylindrical battery of this disclosure may be a primary battery or a secondary battery. It may also be a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte. In the following, a non-aqueous electrolyte secondary battery (lithium-ion battery) using a non-aqueous electrolyte will be given as an example of one embodiment of the cylindrical battery 10, but the cylindrical battery of this disclosure is not limited to this.

[0011] Where multiple embodiments and modifications are included below, it is intended from the outset that new embodiments may be constructed by appropriately combining their characteristic features. In the following embodiments, the same reference numerals are used for the same components in the drawings, and redundant explanations are omitted. In addition, 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. The axial direction of the cylindrical battery 10 coincides with the height direction of the cylindrical battery 10, but for the sake of explanation, the side of the sealing body 17 in the axial direction is referred to as "upper," and the bottom side of the outer casing 16 in the axial direction is referred to as "lower." 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.

[0012] 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 each other via the separator 13. As shown in 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.

[0013] 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 of 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.

[0014] As shown in Figure 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 to be slightly larger than the positive electrode 11 in order to suppress lithium deposition, and is longer than the positive electrode 11 in both the longitudinal and width (short-side) directions. The two separators 13 are formed to be at least slightly larger than the positive electrode 11 and are arranged, for example, to sandwich the positive electrode 11.

[0015] The positive electrode 11 has a positive electrode current collector and positive electrode mixture layers formed on both sides of the current collector. As 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 mixture layer contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc. onto the positive electrode current collector, drying the coating film, and then compressing it to form the positive electrode mixture layers on both sides of the current collector.

[0016] 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.

[0017] Examples of the conductive agent contained in the positive electrode mixture layer include carbon materials such as carbon black, acetylene black, ketjen black, and graphite. Examples of the binder contained in the positive electrode mixture layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resin, acrylic resin, polyolefin resin, etc. These resins may be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

[0018] The negative electrode 12 has a negative electrode current collector and negative electrode mixture layers formed on both sides of the 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 its surface layer can be used. The negative electrode mixture layer contains a negative electrode active material and a binder. The negative electrode 12 can be manufactured, for example, by applying a negative electrode mixture slurry containing a negative electrode active material and a binder, etc. onto the negative electrode current collector, drying the coating film, and then compressing it to form the negative electrode mixture layers on both sides of the current collector.

[0019] Generally, a carbon material that reversibly intercalates and releases 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 massive graphite, and artificial graphite such as graphitized mesophase carbon microbeads. The negative electrode binder layer may contain a Si material containing silicon (Si) 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 the metal, a compound containing the metal, or the like may be used.

[0020] As the binder contained in the negative electrode binder layer, a fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like may be used as in the case of the positive electrode 11, but preferably styrene-butadiene rubber (SBR) or a modified product thereof is used. The negative electrode binder layer may contain, for example, in addition to SBR or the like, CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, or the like.

[0021] A porous sheet having ion permeability and insulation is used for the separator 13. Specific examples of the porous sheet include a microporous thin film, a woven fabric, a non-woven fabric, and the like. As the material of the separator 13, polyolefin resins such as polyethylene and polypropylene, cellulose, and the like are preferable. The separator 13 may have either a single-layer structure or a laminated structure. A heat-resistant layer or the like may be formed on the surface of the separator 13. Note that the negative electrode 12 may constitute the start end of the electrode body 14, but generally, the separator 13 extends beyond the start side end of the negative electrode 12, and the start side end of the separator 13 becomes the start end of the electrode body 14.

[0022] 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.

[0023] As shown in Figure 1, the cylindrical battery 10 has 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, the 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 the negative electrode lead 21 attached to the negative electrode 12 extends towards the bottom 40 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 sealing plate 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 40 of the outer casing 16, and the outer casing 16 becomes the negative electrode terminal.

[0024] The outer casing 16 is a metal container with a bottomed cylindrical section. The space between the outer casing 16 and the sealing body 17 is sealed by an annular gasket 28, thereby sealing the internal space of the battery case 15. The gasket 28 also 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. In other words, the gasket 28 serves as a sealing material to maintain airtightness inside the battery and as an insulating material to prevent short circuits between the outer casing 16 and the sealing body 17.

[0025] The outer container 16 has an annular groove 35 on a portion of its cylindrical outer surface in the axial direction. The groove 35 can be formed, for example, by spinning a portion of the cylindrical outer surface radially inward to create a recess on the radially inward side. The outer container 16 has a bottomed cylindrical portion 30 including the groove 35 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 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 fixed to the outer container 16 by being sandwiched between the shoulder portion 33 and the groove 35 via a gasket 28 through the crimping.

[0026] Next, the structure of the bottom 40 of the outer can 16 will be described in detail. As shown in Figure 1, the bottom 40 of the outer can 16 has a convex inversion portion 43 that protrudes toward the electrode body 14 in the axial direction. The inversion portion 43 is located in the radial center of the bottom 40, and its planar shape when viewed from the outside of the bottom in the axial direction is approximately circular. The inversion portion 43 includes a tapered portion 43a whose inner diameter decreases as it approaches the electrode body 14 in the axial direction, and a flat portion 43b that connects to the annular end of the tapered portion 43a on the electrode body 14 side in the axial direction and is approximately perpendicular to the axial direction. In this embodiment, the tapered portion 43a and the flat portion 43b have the shape of an approximately frustoconical pyramid. However, the tapered portion 43a may have any shape in which the inner diameter decreases as it approaches the electrode body 14 in the axial direction. Also, the planar shape of the flat portion surface 43b when viewed from the outside of the bottom in the axial direction is approximately circular. The negative electrode lead 21 is connected to the flat portion 43b of the reversal portion 43.

[0027] Next, the structure of the sealing body 17 will be described in detail. Figure 3 is an enlarged cross-sectional view of the peripheral part of the sealing body of the cylindrical battery 10. As shown in Figure 3, the sealing body 17 has a structure in which a terminal plate 23, an annular insulating plate 25, and a sealing plate 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 insulating plate 25 is electrically connected. The terminal plate 23 constitutes the bottom plate of the sealing body 17 and has a circular upper surface 23a located on substantially the same plane. The terminal plate 23 has an annular thick-walled portion 23b located on the radially outward side and a disc-shaped thin-walled portion 23c that is thinner than the thick-walled portion 23b and is connected to the radially inward annular end of the thick-walled portion 23b. The positive electrode lead 20 is connected to the lower surface of the thick-walled portion 23b of the terminal plate 23 by welding or the like. The sealing body 17 may have a terminal cap placed on the sealing plate 27.

[0028] The sealing plate 27 is circular in plan view. The sealing plate 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 sealing plate 27, which functions as a safety valve (explosion-proof valve), because of their excellent flexibility. The sealing plate 27 is circular in plan view. The sealing plate 27 has a central portion 27a, an outer peripheral portion 27b, and an inclined portion 27c connecting the central portion 27a and the outer peripheral portion 27b. The upper surface of the thin-walled portion 23c of the terminal plate 23 and the lower surface of the central portion 27a of the sealing plate 27 are joined by metallurgical joining, for example, by laser welding. If the terminal plate 23 is formed of aluminum or an aluminum alloy, similar to the sealing plate 27, the joining of the sealing plate 27 and the terminal plate 23 can be easily performed.

[0029] The thickness of the inclined portion 27c is thinner than that of the central portion 27a. The lower surface of the inclined portion 27c is located above the lower surface of the central portion 27a and is connected to the lower surface of the central portion 27a via an annular step portion 29. The annular upper surface 26a of the inclined portion 27c is an inclined surface that is located higher as it moves radially outward, and the annular lower surface 26b of the inclined portion 27c is also an inclined surface that is located higher as it moves radially outward. The thickness of the inclined portion 27c decreases as it moves radially outward.

[0030] The insulating plate 25 is fixed by press-fitting onto the outer circumferential surface of the annular stepped portion 29, for example. The insulating plate 25 has an annular projection 25a on its radially outer circumferential side that bends downward in the axial direction, and the thickened portion 23b of the terminal plate 23 is fixed by press-fitting onto the inner circumferential surface of the annular projection 25a, for example. The insulating plate 25 is provided to ensure insulation and prevents the thickened portion 23b of the terminal plate 23 from making electrical contact with the sealing plate 27.

[0031] The insulating plate 25 is preferably made of a material that does not affect the battery characteristics. Examples of materials for the insulating plate 25 include polymer resins, such as polypropylene (PP) resin and polybutylene terephthalate (PBT) resin. The insulating plate 25 has one or more vent holes 25b that penetrate axially at a location that axially overlaps with the inclined portion 27c of the sealing plate 27, and the terminal plate 23 has one or more vent holes 23d that penetrate axially at a location that axially overlaps with the insulating plate 25. With this configuration, the gas generated in the electrode body 14 can pass through the vent holes 23d, the space between the insulating plates 25 and the insulating plates 25, and the vent holes 25b, and flow into the space 36 provided between the inclined portion 27c and the insulating plates 25 in the axial direction.

[0032] In the above configuration, when the cylindrical battery 10 overheats abnormally and the internal pressure of the cylindrical battery 10 reaches a predetermined value, the sealing body 17 performs the following current interruption and gas release operations. Specifically, when the cylindrical battery 10 overheats abnormally and the internal pressure of the cylindrical battery 10 reaches a predetermined value, as shown in Figure 4, the central portion 27a and the inclined portion 27c of the sealing plate 27 are inverted axially upward, with the radially outward annular end 39, which has lower rigidity, as a fulcrum, due to the internal pressure of the battery indicated by arrow a. Simultaneously with this inversion, as shown in Figure 4, the thin-walled portion 23c of the terminal plate 23 breaks, separating the portion connected from the terminal plate 23 to the sealing plate 27, or the weld between the terminal plate 23 and the sealing plate 27 comes undone. This operation interrupts the current path between the terminal plate 23 and the sealing plate 27.

[0033] Furthermore, as the internal pressure increases, as shown in Figure 5, the inverted portion 43 of the bottom 40 inverts axially downward, using its radially outward annular end 48 as a fulcrum. After the inverted portion 43 of the bottom 40 inverts, the inverted portion 43 becomes a convex shape that protrudes on the opposite side from the electrode body 14 in the axial direction. Subsequently, as the internal pressure increases further, the annular end 39 of the inclined portion 27c ruptures, and the gas inside the battery is discharged to the outside through the rupture in the sealing plate 27 via the vent holes 23d and 25b. This prevents the cylindrical battery 10 from rupturing even if the internal pressure rises, suppresses the impact on the equipment that houses the cylindrical battery 10, and enhances safety. The sealing plate 27 constitutes a safety valve, and the inclined portion 27c of the sealing plate 27 is a rupture portion that discharges the internal gas to the outside when it ruptures.

[0034] The first pressure at which the sealing plate 27, acting as a safety valve, ruptures can be adjusted, for example, by the thickness of the annular end 39 on the radially outward side of the inclined portion 27c. The second pressure at which the reversing portion 43 reverses can be adjusted, for example, by the thickness of the annular end 48 on the radially outward side of the tapered portion 43a of the bottom portion 40. The second pressure is adjusted to be less than the first pressure, but it is preferable that it be adjusted to be less than the pressure at which the sealing body 17 interrupts the current.

[0035] [Examples] The inventors have confirmed that by fabricating the cylindrical battery according to the following embodiment, the reversal portion can be reversed to the opposite side from the axial electrode body before the sealing plate (safety valve) breaks.

[0036] (Fabrication of the positive electrode) LiNi 0.8 Co 0.15 Al 0.05 O 2A positive electrode slurry was prepared by mixing 100 parts by mass of positive electrode active material, 1.7 parts by mass of polyvinylidene fluoride as a binder, and 2.5 parts by mass of acetylene black as a conductive agent in a dispersion medium. The positive electrode slurry was applied to both sides of a positive electrode current collector made of aluminum foil, excluding the connection portion of the positive electrode lead, dried, and then rolled to a predetermined thickness to obtain a positive electrode plate. This positive electrode plate was cut to a predetermined size, and an aluminum positive electrode lead was attached to the exposed portion of the current collector by ultrasonic welding to produce a positive electrode.

[0037] (Fabrication of the negative electrode) Easily graphitizable carbon was used as the negative electrode active material. 100 parts by mass of the negative electrode active material, 0.6 parts by mass of polyvinylidene fluoride as a binder, 1 part by mass of carboxymethylcellulose as a thickener, and an appropriate amount of water were mixed in a double-arm mixing machine to obtain a negative electrode mixture slurry. This negative electrode mixture slurry was applied to both sides of a negative electrode current collector made of copper foil, excluding the connection portion of the negative electrode lead, dried, and then rolled to a predetermined thickness to obtain a negative electrode plate. This negative electrode plate was cut to a predetermined size, and a negative electrode lead made of Ni-Cu-Ni clad material was attached to the exposed portion of the current collector by ultrasonic welding to produce a negative electrode.

[0038] (Preparation of non-aqueous electrolyte) A mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) is used, with lithium hexafluorophosphate (LiPF) as the electrolyte. 6 A non-aqueous electrolyte was prepared by dissolving the solution until the concentration reached 1.0 mol / L.

[0039] (Preparation of sealing body) A sealing body with the structure shown in Figure 2 was fabricated. First, a circular terminal plate was formed using aluminum material, and a thin section was provided in the radial center of the terminal plate. Then, the terminal plate, sealing plate, and insulating plate were integrated to create the sealing body.

[0040] (Manufacturing of outer cans) An outer casing with the structure shown in Figure 1 was manufactured. Before the deep drawing process, a reversal mechanism was fabricated by press working at the position of the steel plate at the bottom of the casing. The pressure during reversal due to the rise in internal pressure of the battery was adjusted to 1.5 MPa, which is smaller than the rupture pressure of the sealing plate acting as a safety valve, and the wall thickness was designed so that the reversal part would not rupture even at an internal pressure of 4 MPa. Subsequently, the steel plate was deep drawn to produce an outer casing with a reversal part at the bottom.

[0041] (Assembly of cylindrical batteries) The positive electrode and electrode plate described above were wound in a spiral shape via a separator made of polyolefin resin to create an electrode body. This electrode body was inserted into the outer casing via a disc-shaped bottom insulating plate, and the negative electrode lead, which is connected to the negative electrode, was electrically connected to the bottom surface of the battery casing by welding. After welding the positive electrode lead to the sealing body, a predetermined amount of non-aqueous electrolyte was injected into the outer casing. Then, the sealing body was placed on the grooved portion of the outer casing via a gasket. After that, the inside of the battery was sealed by crimping the sealing body into the opening of the outer casing, and a cylindrical battery was created.

[0042] According to this disclosure, before the sealing plate 27, which functions as a safety valve, breaks, the reversing portion 43, which is provided on the bottom 40 of the cylindrical battery 10 and has a convex shape that protrudes toward the electrode body 14 in the axial direction, reverses. Therefore, a space 60 (see Figure 5) is formed between the lower surface of the electrode body 14 and the bottom 40 of the outer casing 16 before the sealing plate 27 exhausts the high-temperature gas. As a result, the high-temperature gas that flows out from the lower surface of the electrode body 14 can be rectified toward the sealing plate 17 side through the hollow portion 57 of the electrode body 14, as shown by arrows b1 and b2 in Figure 5. In this way, the flow of high-temperature gas along the outer circumference of the outer casing 16 can be suppressed, so damage to the side of the outer casing 16 when the cylindrical battery 10 overheats can be effectively suppressed. Therefore, even if the cylindrical battery 10 overheats, the high-temperature gas can be smoothly exhausted through the safety valve, so damage to batteries and equipment around the cylindrical battery 10 can be suppressed.

[0043] [Preferred cylindrical battery configuration and its effects] The reversal portion 43 may include a tapered portion 43a whose inner diameter decreases as it moves toward the electrode body 14 in the axial direction, and a flat portion 43b that connects to the inner circumferential end of the tapered portion 43a and extends substantially parallel to a plane substantially perpendicular to the axial direction. Furthermore, it is preferable that the reversal portion 43 be provided at the center of the bottom portion 40, and it is more preferable that the planar shape of the reversal portion 43 be circular.

[0044] With the above configuration, the reversal section 43 can easily reverse smoothly using the annular end 48 on the radially outward side of the tapered section 43a as a fulcrum. In addition, since the gap between the lower surface of the hollow section 57 of the electrode body 14 and the bottom 40 of the outer can 16 becomes larger after reversal, the high-temperature gas can be efficiently guided towards the sealing body 17.

[0045] 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.

[0046] For example, in the above embodiment, the case in which the reversal portion 43 has a tapered portion 43a and a flat portion 43b was described. However, the reversal portion may have any convex shape that protrudes toward the electrode body in the axial direction. For example, the reversal portion may have a dome shape formed when the arch is rotated horizontally around its apex.

[0047] Furthermore, although the case in which the inversion portion 43 is provided at the center of the bottom portion 40 has been described, the inversion portion may also include a portion located radially outward from the bottom portion. Also, although the case in which the planar shape of the inversion portion 43 is circular has been described, the planar shape of the inversion portion may be any shape other than a circle. For example, the planar shape of the inversion portion may be a square, a rectangle, or an ellipse.

[0048] Furthermore, as shown in Figure 6, which is a cross-sectional view corresponding to Figure 1 in the modified cylindrical battery 110, the reversal portion 143 may have an annular portion 160 on the radially outward side, the axial thickness decreasing as it moves toward the radially outward side. In this way, the outer peripheral end 161 of the annular portion 160 can be reliably used as a pivot point for reversal, and the desired reversal can be achieved. [Explanation of Symbols]

[0049] 10,110 Cylindrical battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Battery case, 16 Outer casing, 17 Sealing body, 20 Positive electrode lead, 21 Negative electrode lead, 23 Terminal board, 27 Sealing plate, 28 Gasket, 40 Bottom, 43,143 Reversing section, 43a Tapered section, 43b Flat section.

Claims

1. An electrode body in which a positive electrode and a negative electrode are wound with a separator in between, A bottomed cylindrical outer container housing the electrode body, The outer can comprises a sealing body that seals the opening, The bottom of the outer casing has a convex shape that protrudes axially toward the electrode body and has a reversal part that reverses when the internal pressure of the battery reaches a first pressure. The sealing body has a safety valve that ruptures when the internal pressure of the battery reaches a second pressure greater than the first pressure, thereby releasing gas from inside the battery. The sealing body has a mechanism for blocking the current path between the electrode body and the sealing body. A cylindrical battery in which the current path is interrupted at a pressure lower than the first pressure when the internal pressure rises.

2. The cylindrical battery according to claim 1, wherein the bottom surface of the inverted portion includes a tapered portion whose inner diameter decreases as it approaches the electrode body side in the axial direction, and a flat portion that connects to the inner circumferential end of the tapered portion and is substantially perpendicular to the axial direction.

3. The cylindrical battery according to claim 1 or 2, wherein the reversing portion is provided at the center of the bottom portion.

4. The cylindrical battery according to any one of claims 1 to 3, wherein the planar shape of the reversal portion is circular.

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