Battery

Abstract

A battery (10) comprises: an electrode body (14); an external can (20) that accommodates the electrode body (14); a sealing body (19) that is for sealing an opening of the external can (20); and a conductive member (40) that is joined to an upper surface (36) (end surface on the opposite side from the electrode body (14) side in the axial direction of the sealing body (19)) of the sealing body (19). The conductive member (40) is constituted by a conductive material. The melting point of the conductive member (40) is lower than the melting point of the material constituting the upper surface (36). A battery (10) according to the present disclosure makes it easier to cut off current to an external device at the time of abnormal heating.

Description

Battery

[0001] The present disclosure relates to a battery, for example, a cylindrical battery, a prismatic battery, or the like.

[0002] Conventionally, as a cylindrical battery, there is one described in Patent Document 1. This cylindrical battery includes an electrode body in which a long positive electrode including a positive electrode core and a positive electrode mixture layer and a long negative electrode including a negative electrode core and a negative electrode mixture layer are wound via a separator, an electrolyte, a bottomed cylindrical outer can that houses the electrode body and the electrolyte, and a sealing body that is caulked and fixed to the opening of the outer can via a gasket. A sealing body electrically connected to the positive electrode core via a positive electrode lead constitutes a positive electrode terminal, and an outer can electrically connected to the negative electrode core via a negative electrode lead constitutes a negative electrode terminal.

[0003] Japanese Unexamined Patent Application Publication No. 2013-016328

[0004] When a cylindrical battery generates abnormal heat, it is necessary to suppress damage to an external device by interrupting the current between the cylindrical battery and the external device. This current interruption is performed by fusing the positive electrode lead due to Joule heat when a large current flows during abnormal heat generation. However, in recent years, the reduction of the resistance of cylindrical batteries has been promoted, the Joule heat generated in the positive electrode lead has become smaller, and it has become difficult for the positive electrode lead to fuse during abnormal heat generation of the cylindrical battery. Also, in batteries other than cylindrical batteries, it is desired that the current can be smoothly interrupted between the battery and an external device during abnormal heat generation, and damage to the external device can be suppressed. Therefore, an object of the present disclosure is to provide a battery that can easily interrupt the current with an external device during abnormal heat generation.

[0005] To solve the above problems, a battery according to the present disclosure includes an electrode body, an outer can that houses the electrode body, a sealing body for closing the opening of the outer can, and a conductive member that is joined to an end face on the opposite side of the electrode body side in the axial direction in the sealing body and is made of a material having a lower melting point than the material constituting the end face.

[0006] In this specification, a sealing body is defined as a single sealing plate having a joint portion to which the electrodes (positive or negative) of an electrode body are directly or indirectly joined via electrode leads, and a sealing portion that is directly or indirectly fixed to the opening of the outer can to close the opening of the outer can, or an integrated body comprising a plurality of members that are integrated with at least one of the joint portion to which the electrodes of an electrode body are directly or indirectly joined via electrode leads, and a sealing portion that is directly or indirectly fixed to the opening of the outer can to close the opening of the outer can, and if there is an annular insulating plate that is integrated with two or more of the plurality of members even if it is not related to both the sealing portion and fixing to the outer can, then the integrated body also includes that annular insulating plate. Therefore, in the definition of this specification, the conductive member is not related to the joint portion to which the electrodes of an electrode body are directly or indirectly joined via electrode leads, is not related to sealing (closing) the opening of the outer can or fixing to the outer can, and is not an annular insulating plate, so it is not included in the sealing body. Furthermore, the axial direction of batteries other than cylindrical batteries is defined as the height direction of the battery.

[0007] According to this disclosure, it is easier to interrupt the current from external devices when the device is generating heat at normal temperatures.

[0008] This is a cross-sectional view in the axial direction of a cylindrical battery according to one embodiment of the present disclosure. This is a top view of the cylindrical battery as seen from above in the axial direction. This is a top view corresponding to Figure 2 of a first modified cylindrical battery. This is a top view corresponding to Figure 2 of a second modified cylindrical battery. This is a top view corresponding to Figure 2 of a third modified cylindrical battery.

[0009] Hereinafter, embodiments of the battery according to this disclosure will be described in detail with reference to the drawings. The battery according to this disclosure may be a primary battery or a secondary battery. Furthermore, the battery according to this disclosure may be a cylindrical battery, a prismatic battery, or any other type of battery. Furthermore, the battery according to this disclosure may use an aqueous electrolyte or a non-aqueous electrolyte. In the following, a lithium-ion cylindrical secondary battery will be given as an example of one embodiment of battery 10, but the battery according to this disclosure is not limited to this.

[0010] It is intended from the outset that new embodiments can be constructed by appropriately combining the characteristic features of the embodiments and modifications described below. 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. In this specification, the axial (height direction) sealing body 19 side of the cylindrical battery 10 is referred to as "top," and the axial bottom 20A side of the outer casing 20 is referred to as "bottom." 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.

[0011] In this specification, a sealing body is defined as comprising a single sealing plate having a joint portion to which the electrodes (positive or negative) of an electrode body are joined directly or indirectly via electrode leads, and a sealing portion that is fixed directly or indirectly via a gasket to the opening of the outer can in order to close the opening of the outer can, or a composite body comprising a plurality of members integrated, which are related to at least one of the joint portion to which the electrodes of an electrode body are joined directly or indirectly via electrode leads, and the sealing portion that is fixed directly or indirectly via a gasket to the opening of the outer can in order to close the opening of the outer can, and which also comprises an annular insulating plate that is integrated with two or more of the plurality of members, even if it is not related to both the sealing portion and fixing to the outer can. Therefore, according to the definitions of this specification, the conductive members 40, 140, 240, and 340 described below are not related to the joints where the electrodes 11 of the electrode body 14 are joined directly or indirectly via the electrode leads 17, nor are they related to sealing (closing) the opening of the outer can 20 or fixing it to the outer can 20, nor are they annular insulating plates 23, and are therefore not included in the sealing body 19.

[0012] Figure 1 is an axial cross-sectional view of a cylindrical battery 10 according to one embodiment of the present disclosure. As shown in Figure 1, the cylindrical battery (hereinafter simply referred to as "battery") 10 comprises an electrode body 14, a non-aqueous electrolyte, a bottomed cylindrical outer casing 20 housing the electrode body 14 and the non-aqueous electrolyte, and a sealing body 19 that closes the opening of the outer casing 20 via an annular gasket 24. The outer casing 20 may be made of a metal mainly composed of iron, for example, a material made of iron with nickel plating. Alternatively, the outer casing 20 may be made of a metal mainly composed of aluminum or the like. The gasket 24 is preferably made of an insulating material with excellent compressibility and resistance, for example, a polyolefin, and more specifically, preferably PP (polypropylene), PPS (polyphenylene sulfide), PFA (perfluoroalkoxyalkane), or PPT (polypropylene terephthalate). The outer casing may have openings at both ends in the vertical direction in the axial direction, and the battery may have a configuration in which each of the two openings is closed by one or more members.

[0013] The electrode body 14 includes a long positive electrode 11, a long negative electrode 12, and two long separators 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 separators 13. The negative electrode 12 is formed to be slightly larger in dimensions than the positive electrode 11 in order to prevent lithium deposition. The negative electrode 12 is formed to be longer than the positive electrode 11 in the winding direction and in the axial direction. The two separators 13 are formed to be slightly larger in dimensions than the positive electrode 11 and are arranged to sandwich the positive electrode 11. The separators 13 protrude above and below the positive electrode 11 and the negative electrode 12.

[0014] Non-aqueous electrolytes are ionic conductive (e.g., lithium ion conductive). Non-aqueous electrolytes may be liquid electrolytes (electrolytes) or solid electrolytes. Liquid electrolytes (electrolytes) contain a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include esters, ethers, nitriles, amides, and mixtures of two or more of these. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof. Non-aqueous solvents may contain halogen-substituted compounds (e.g., fluoroethylene carbonate) in which at least some of the hydrogen atoms in these solvents are replaced with halogen atoms such as fluorine. Examples of electrolyte salts include LiPF4. ６ Lithium salts such as these are used.

[0015] As solid electrolytes, for example, solid or gel-like polymer electrolytes, inorganic solid electrolytes, etc., are used. Polymer electrolytes include, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As matrix polymers, for example, polymer materials that absorb non-aqueous solvents and gel are used. As polymer materials, for example, fluororesins, acrylic resins, polyether resins, etc., are used. As inorganic solid electrolytes, for example, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.) are used.

[0016] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer formed on both sides of the positive electrode core. The positive electrode core can be made of a metal foil that is stable within the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal arranged on its surface. The positive electrode mixture layer contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 is manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder onto the positive electrode core, drying the coating, and then compressing it to form the positive electrode mixture layer on both sides of the positive electrode core.

[0017] The positive electrode active material is mainly composed of a lithium-containing metal composite oxide. Examples of 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, and W. A preferred example of a lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn, and Al.

[0018] Examples of conductive agents included in the positive electrode mixture layer include carbon black such as acetylene black and Ketjen black, and carbon materials such as graphite. Examples of binders included in the positive electrode mixture layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. These resins may be used in combination with cellulose derivatives such as carboxymethylcellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

[0019] The negative electrode 12 comprises a negative electrode core and negative electrode mixture layers formed on both sides of the negative electrode core. The negative electrode core can be made of a metal foil that is stable within the potential range of the negative electrode 12, such as copper or a copper alloy, or a film with the metal arranged on its surface. The negative electrode mixture layers contain a negative electrode active material and a binder. The negative electrode 12 is manufactured, for example, by applying a negative electrode mixture slurry containing the negative electrode active material and binder onto the negative electrode core, drying the coating, and then compressing it to form the negative electrode mixture layers on both sides of the negative electrode core.

[0020] Generally, carbon materials that reversibly intercept and release lithium ions are used as the negative electrode active material. Preferred carbon materials are graphite such as natural graphite such as flake graphite, lump graphite, and clay graphite, and artificial graphite such as lump graphite and graphitized mesophase carbon microbeads. The negative electrode mixture layer may contain silicon (Si) material as the negative electrode active material. In addition, metals that alloy with lithium other than Si, alloys containing such metals, compounds containing such metals, etc., may be used as the negative electrode active material.

[0021] The binder included in the negative electrode mixture layer may be fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, etc., as in the case of the positive electrode 11, but preferably styrene-butadiene rubber (SBR) or a modified version thereof is used. In addition to SBR, the negative electrode mixture layer may also contain, for example, CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, etc.

[0022] 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, polyolefin resins such as polypropylene, or cellulose. 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.

[0023] An upper insulating plate 15 is positioned above the electrode body 14, and a lower insulating plate 16 is positioned below the electrode body 14. In the example shown in Figure 1, a single positive electrode lead 17 attached to the positive electrode 11 extends through a through-hole in the upper insulating plate 15 towards the sealing body 19 and is joined to the lower surface of the sealing body 19. One end of the positive electrode lead 17 is joined to the positive electrode 11 of the electrode body 14 by ultrasonic welding or the like, and the other end of the positive electrode lead 17 is joined to the lower surface of the sealing body 19 by welding or the like. On the other hand, a negative electrode lead 18 attached to the negative electrode 12 extends through the outside of the lower insulating plate 16 towards the bottom 20A of the outer container 20 and is joined to the inner surface of the bottom 20A. One end of the negative electrode lead 18 is joined to the negative electrode 12 of the electrode body 14 by ultrasonic welding or the like, and the other end of the negative electrode lead 18 is joined to the bottom 20A by welding or the like.

[0024] To effectively suppress short circuits, it is preferable that the area around the joint connecting the positive electrode 11 to the positive electrode lead 17 is covered with insulating tape (not shown), and it is preferable that the area around the joint connecting the negative electrode 12 to the negative electrode lead 18 is covered with insulating tape (not shown). Here, these insulating tapes are made of an insulating material, for example, a polyimide film may be used as the base material and silicone as the adhesive. The sealing body 19 to which the positive electrode lead 17 is connected becomes the positive electrode terminal, and the outer casing 20 to which the negative electrode lead 18 is connected becomes the negative electrode terminal.

[0025] In the example shown in Figure 1, the positive lead 17 is electrically connected to an intermediate part of the positive core, such as the center in the winding direction, and the negative lead 18 is electrically connected to the winding end in the negative core. However, the positive lead 17 may be electrically connected to a location other than the intermediate part in the winding direction of the positive core, and the negative lead may be electrically connected to the winding start end in the winding direction of the negative core.

[0026] The electrode body may have two negative electrode leads, with one end of one negative electrode lead electrically connected to the winding start end in the winding direction of the negative electrode core, and the other end of the negative electrode lead electrically connected to the bottom of the outer can. Then, one end of the other negative electrode lead may be electrically connected to the winding end in the winding direction of the negative electrode core, and the other end of the other negative electrode lead electrically connected to the bottom of the outer can. Alternatively, regardless of whether the negative electrode and the bottom of the outer can are electrically connected by one or more negative electrode leads, the negative electrode and the outer can may be electrically connected by bringing the exposed negative electrode core portion, which constitutes part or all of the outer surface of the electrode body and exposes the negative electrode core, into contact with the inner surface of the outer can.

[0027] Furthermore, there may be multiple positive electrode leads (for example, eight positive electrode leads) joined to the positive electrode core at intervals in the longitudinal direction of the positive electrode, and the multiple positive electrode leads may be joined to a metal current collector plate included in the sealing body by laser welding or the like. Alternatively, the upper end of the positive electrode core may constitute the upper end of the electrode body, and the upper end of the positive electrode core may be joined to a metal current collector plate included in the sealing body by laser welding or the like. Also, the lower end of the negative electrode core may constitute the lower end of the electrode body. The lower end of the negative electrode core may be joined to the upper surface of the metal current collector plate by laser welding or the like, and the lower surface of the current collector plate may be joined to the bottom of the outer casing by laser welding or the like.

[0028] A gasket 24 is provided between the outer casing 20 and the sealing body 19 to ensure airtightness inside the battery and insulation between the outer casing 20 and the sealing body 19. The outer casing 20 has a cylindrical portion 20B and a bottom portion 20A. The cylindrical portion 20B includes an annular grooved portion 28 and an annular shoulder portion 29. The grooved portion 28 is formed by spinning a part of the cylindrical portion 20B to create a recess radially inward. On the other hand, the shoulder portion 29 is formed when the upper end of the cylindrical portion 20B is bent radially inward and crimped to the flange portion (peripheral edge) 31 of the sealing body 19, and extends radially inward. The sealing body 19 is fixed to the outer casing 20 by being sandwiched between the shoulder portion 29 and the grooved portion 28 via the gasket 24 through crimping.

[0029] The sealing body 19 has a structure in which a metal terminal plate 21, an annular insulating plate 23, and a metal sealing plate 22 are stacked in order from the electrode body 14 side. The sealing plate 22 constitutes a rupture plate (valve body) and is positioned opposite the terminal plate 21 with the annular insulating plate 23 in between. The insulating plate 23 has an opening 23A in the radial center and a ventilation hole 23B in the part that overlaps with the ventilation hole 21C of the terminal plate 21. The sealing plate 22 has a valve portion 22A on the radial center side that ruptures as the internal pressure of the battery increases. The terminal plate 21 has an annular portion 21A and a central portion 21B that is connected to the radially inward end of the annular portion 21A and is located in the radial center. The central portion 21B has a disc shape and is thinner than the annular portion 21A.

[0030] The valve portion 22A is joined to the central portion 21B of the terminal plate 21 by welding or the like through an opening 23A in the insulating plate 23. The valve portion 22A includes a projection 33 located in the radial center and projecting downward, and a thin-walled portion 34 located radially outside the projection 33. The thickness of the thin-walled portion 34 decreases as it extends radially outward. Because the thickness of the thin-walled portion 34 decreases as it extends radially outward, an annular space 39 is provided below the thin-walled portion 34. The insulating plate 23 is positioned radially outside the projection 33 so as to surround the projection 33 around its entire circumference. The insulating plate 23 includes a portion located between the sealing plate 22 and the terminal plate 21.

[0031] The sealing plate 22 holds the insulating plate 23, and the insulating plate 23 holds the terminal plate 21. Specifically, the sealing plate 22 includes an annular thickened portion 35 connected to the radially outward end of the thinned portion 34, and the thickened portion 35 has an annular projection 37 that protrudes downward. The outer circumferential surface of the insulating plate 23 is fitted and fixed to the inner circumferential surface of the annular projection 37. The insulating plate 23 also has an annular projection 38 that protrudes downward on the outer circumferential side, and the inner circumferential surface of the annular projection 38 is fitted and fixed to the outer circumferential surface of the terminal plate 21. The insulating plate 23 includes a clamping portion that is sandwiched radially between the annular projection 37 and the terminal plate 21. The ventilation hole 21C is provided in the annular portion 21A. The positive lead 17 is joined to the lower surface of the annular portion 21A. The terminal board 21 to which the positive lead 17 is connected and the sealing plate 22 are electrically connected, thereby forming a current path from the electrode body 14 to the sealing plate 22.

[0032] The structure of the sealing body 19 is not limited to the structure shown in Figure 1. For example, the sealing body 19 may consist only of rupture plates. Alternatively, the sealing body may have a laminated structure including two rupture plates (lower valve body and upper valve body) joined at their radial centers, an annular insulating plate sandwiched between the two rupture plates, and a convex terminal cap covering the rupture plates. Alternatively, the sealing body may have a structure comprising a sealing plate and a current collector plate having an upper surface to which a plurality of positive electrode leads are welded by laser welding or the like, with the lower surface on the outer circumference of the sealing body and the upper surface on the outer circumference of the current collector plate joined by laser welding or the like. Alternatively, the sealing body does not have to have rupture plates, and the bottom of the outer casing may have a thin, easily breakable portion that breaks when the battery overheats abnormally.

[0033] The battery 10 further comprises a conductive member 40 joined to the upper surface 36 of the sealing body 19 (the end face of the sealing body 19 opposite to the electrode body 14 side in the axial direction). Figure 2 is a top view of the battery 10 as seen from above in the axial direction. In this embodiment, the conductive member 40 is a disc member having a substantially uniform (substantially constant) thickness and has a substantially circular shape when viewed from above. The conductive member 40 is joined to the upper surface 36 of the sealing body 19 by resistance welding, laser welding, or ultrasonic welding. The upper surface 36 of the sealing plate (rupture plate) 22 has a flat portion 36a in the radial center that extends substantially parallel to the axial direction perpendicular to the axial direction. All of the conductive member 40 is positioned so as to overlap the flat portion 36a in the axial direction.

[0034] The conductive member 40 is made of a material that has a lower melting point and conductivity than the material that makes up the upper surface 36. The sealing plate (rupture plate) 22 including the upper surface 36 is made of aluminum with a melting point of 660.3°C, and the conductive member 40 may be made of Sn (tin), Bi (bismuth), Pb (lead), or a compound containing one or more of these elements. Alloys of Sn and Bi are known to have a melting point of about 140°C. Therefore, in the above example, the conductive member 40 has a much lower melting point than the sealing plate 22 including the upper surface 36, and will melt at an early stage if the battery 10 overheats abnormally.

[0035] A conductive connecting member, electrically connected to the terminals of an external device (not shown), is joined to or in contact with the conductive member 40, thereby electrically connecting the external device to the battery 10. The external device may be any electrical product. For example, if the battery 10 is included in a battery module in which multiple batteries 10 are electrically connected, the tongue-shaped leads of a current collector plate, cut from the body of the current collector plate to which the positive electrodes of the other multiple batteries 10 are electrically connected, may be joined to the conductive member 40 by laser welding or the like. In this case, the connecting member is made up of a current collector plate, and the external device includes multiple batteries 10 other than the battery 10 in question. Alternatively, the battery 10 may be used as a detachable power source for an electrical product that constitutes the external device. In this case, by attaching the battery 10 to a predetermined mounting location in the electrical product, the conductive member 40 comes into contact with a conductive connecting member built into the electrical product.

[0036] Next, the effects of the battery 10 of this disclosure will be explained. In the above configuration, suppose the battery 10 overheats abnormally due to an internal short circuit or the like. Then, in the initial stage after the battery 10 overheats abnormally, the heat transmitted from the heated electrode body 14 to the conductive member 40 via the positive electrode lead 17 and the sealing body 19 causes the conductive member 40, which has a low melting point, to melt. This melting separates the connecting member that electrically connects the sealing body 19 to the external device from the sealing body 19, thereby interrupting the current path and heat transfer path from the abnormally overheated battery 10 to the external device. This interruption prevents the external device from being damaged by the current and heat from the abnormally overheated battery 10.

[0037] Subsequently, if the abnormal heat generation of the battery 10 continues and the internal pressure of the battery 10 rises, the valve portion 22A inverts so that it becomes convex axially upward, using the radially outward annular end portion 22B (see Figure 1), which has low rigidity in the thin-walled portion 34, as a fulcrum. Simultaneously with this inversion, the central portion 21B is separated from the annular portion 21A or detaches from the valve portion 22A. Since the valve portion 22A is insulated from the annular portion 21A by the insulating plate 23, the current path electrically connecting the electrode body 14 and the sealing body 19 is interrupted by this inversion. If the internal pressure of the battery rises further, the annular end portion 22B of the thin-walled portion 34 ruptures, forming a gas outlet, and high-temperature gas and molten material are discharged to the outside. This discharge of high-temperature gas etc. makes the battery 10 safe. The annular end portion 22B constitutes the rupture portion of the sealing plate (rupture plate) 22.

[0038] The interruption of the current path and heat transfer path between the battery 10 and the external device due to the melting of the conductive member 40 may occur after the reversal of the valve 22A, or after the rupture plate breaks. In those cases as well, the heat transmitted to the external device can be reduced by the melting of the conductive member 40, thereby suppressing damage to the external device. Alternatively, in the case of a structure in which the sealing body does not break, as in this embodiment, damage to the external device can be suppressed after the conductive member 40 has melted. That is, regardless of the configuration of the sealing body, by joining the conductive member 40, which is made of a material with a lower melting point than the material constituting the upper surface 36 of the sealing body 19, to the upper surface 36 of the sealing body 19, damage to the external device can be suppressed when the battery 10 overheats abnormally.

[0039] It is preferable that the thickness (maximum thickness) of the conductive member 40 is 0.1 mm or more, as this makes it easier and more reliable to connect the conductive connecting member that is electrically connected to the external device. It is preferable that the thickness (maximum thickness) of the conductive member 40 is 2.0 mm or less, as this makes it easier to reduce the axial dimension of the battery 10 and to make the battery 10 more compact. It is preferable that the upper end of the conductive member 40 is located below the upper end of the outer casing 20 (on the electrode body 14 side in the axial direction), as this makes it easier to reduce the axial dimension of the battery 10 and to make the battery 10 more compact.

[0040] It is preferable that the conductive member 40 is composed of Sn (tin), Bi (bismuth), Pb (lead), or a compound containing one or more of these elements, in order to ensure sufficient rigidity of the conductive member 40 while making it easier to lower the melting point of the conductive member 40. It is preferable that all of the conductive member 40 be arranged in a location that overlaps axially with the planar portion 36a which extends substantially parallel to the orthogonal direction perpendicular to the axial direction, in order to make it easier to stably, easily, and reliably bond the conductive member 40 to the sealing body 19. Furthermore, in the case where the conductive member 40 is bonded to the upper surface of the rupture plate, as in this embodiment, arranging all of the conductive member 40 in a location that overlaps axially with the planar portion 36a effectively suppresses the conductive member 40 from affecting the reversal and fracture movements of the rupture plate.

[0041] This disclosure is not limited to the embodiments and their variations described above, and various improvements and modifications are possible within the scope of the claims of this application and their equivalents. For example, the conductive member joined to the upper surface of the sealing body may include portions that overlap axially in a direction that is not substantially parallel to the orthogonal direction perpendicular to the axial direction. The conductive member may also be made of a material other than Sn, Bi, Pb, or a compound containing one or more of these elements. The axial thickness (maximum thickness) of the conductive member may be less than 0.1 mm or greater than 2.0 mm. Furthermore, although the case in which the conductive member 40 has a substantially uniform thickness has been described, the conductive member may have portions where the thickness changes.

[0042] The planar shape of the conductive member when viewed from the axial upper side can be any shape. For example, as shown in Figure 3, the planar shape of the conductive member 140 when viewed from the axial upper side can be a square, and as shown in Figure 4, the planar shape of the conductive member 240 when viewed from the axial upper side can be a regular pentagon or any other polygon. Alternatively, as shown in Figure 5, the planar shape of the conductive member 340 when viewed from the axial upper side can be an ellipse or a roughly ellipse, or any other shape enclosed by a closed curved line. Furthermore, although the case in which the positive electrode 11 is electrically connected to the sealing body 19 and the negative electrode 12 is electrically connected to the outer casing 20 has been described, the negative electrode may be electrically connected to the sealing body and the positive electrode may be electrically connected to the outer casing 20. In addition, the battery of this disclosure may be a battery other than a cylindrical battery, for example, a prismatic battery.

[0043] Furthermore, the battery of this disclosure may have the following configurations: Configuration 1: A battery comprising an electrode body, an outer casing for housing the electrode body, a sealing body for closing the opening of the outer casing, and a conductive member joined to the end face of the sealing body opposite to the electrode body side in the axial direction, and made of a material having a lower melting point and conductivity than the material constituting the end face. Configuration 2: The battery according to Configuration 1, wherein the end face is contained in a rupture plate having a fracture portion that breaks as the internal pressure increases. Configuration 3: The battery according to Configuration 1 or 2, wherein the conductive member is made of Sn, Bi, Pb, or a compound containing one or more of these elements. Configuration 4: The battery according to any one of Configurations 1 to 3, wherein the axial thickness of the conductive member is 0.1 mm or more and 2.0 mm or less. Configuration 5: The battery according to any one of Configurations 1 to 4, wherein the end face has a planar portion that extends substantially parallel to an orthogonal direction perpendicular to the axial direction, and all of the conductive members are arranged in a location that overlaps the planar portion in the axial direction.

[0044] 10 Battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Upper insulating plate, 16 Lower insulating plate, 17 Positive electrode lead, 18 Negative electrode lead, 19 Sealing body, 20 Outer can, 20A Bottom, 20B Cylindrical part, 21 Terminal board, 21A Annular part, 21B Central part, 21C Ventilation hole, 22 Sealing plate, 22A Valve part, 22B Annular end (broken part), 23 Insulating plate, 23A Opening, 23B Ventilation hole, 24 Gasket, 28 Grooved part, 29 Shoulder part, 33 Protruding part, 34 Thin-walled part, 35 Thick-walled part, 36 Top surface of sealing plate, 36a Flat part 37, 38 Annular projection, 39 Space, 40, 140, 240, 340 Conductive members.

Claims

1. A battery comprising: an electrode body; an outer casing for housing the electrode body; a sealing body for closing the opening of the outer casing; and a conductive member joined to the end face of the sealing body opposite to the electrode body side in the axial direction, and made of a material having a lower melting point and conductivity than the material constituting the end face.

2. The battery according to claim 1, wherein the end face is included in a rupture plate having a fracture portion that breaks as the internal pressure increases.

3. The battery according to claim 1, wherein the conductive member is composed of Sn, Bi, Pb, or a compound containing one or more of these elements.

4. The battery according to claim 1, wherein the axial thickness of the conductive member is 0.1 mm or more and 2.0 mm or less.

5. The battery according to any one of claims 1 to 4, wherein the end face has a planar portion extending substantially parallel to an orthogonal direction perpendicular to the axial direction, and all of the conductive members are arranged so as to overlap the planar portion in the axial direction.

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