Cylindrical secondary battery

Abstract

A cylindrical secondary battery (10) comprises an electrode body (14) in which a positive electrode (11) and a negative electrode (12) are wound with a separator (13) interposed therebetween, a bottomed cylindrical external can (20) which accommodates the electrode body (14), and a sealing body (30) which covers an opening (24) of the external can (20), said cylindrical secondary battery (10) being characterized in that a discharge valve (21A) that opens when the internal pressure of the battery reaches a prescribed pressure is provided to the bottom (21) of the external can (20), and a biasing part (50) that biases the electrode body (14) toward the bottom (21) is provided between the electrode body (14) and the sealing body (30).

Description

Cylindrical secondary battery

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

[0002] Cylindrical batteries generally include a wound electrode body, a bottomed cylindrical outer can that houses the electrode body, and a sealing body that closes the opening of the outer can. Patent Document 1 discloses a cylindrical secondary battery provided with a discharge valve at the bottom of the outer can for discharging the electrode body and the like to the outside of the battery when the internal pressure of the battery rises due to abnormal heat generation.

[0003] WO 2016 / 067510

[0004] In applications that require a large capacity such as in-vehicle use, a plurality of batteries may be electrically connected and modularized. At that time, if abnormal heat generation occurs in one of the plurality of batteries, heat may be transferred to the surrounding batteries, and abnormal heat generation may also occur in the surrounding batteries. Therefore, from the perspective of improving reliability, for a battery in which abnormal heat generation has occurred, it is required to smoothly discharge components such as the electrode body to the outside of the battery through a discharge valve provided in the battery, and to lower the temperature of the battery in which abnormal heat generation has occurred.

[0005] A cylindrical secondary battery according to one aspect of the present disclosure is a cylindrical secondary battery including an electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, a bottomed cylindrical outer can that houses the electrode body, and a sealing body that closes the opening of the outer can, wherein a discharge valve that opens when the internal pressure of the battery reaches a predetermined pressure is provided at the bottom of the outer can, and a biasing portion that biases the electrode body toward the bottom side is provided between the electrode body and the sealing body.

[0006] According to the cylindrical secondary battery according to one aspect of the present disclosure, the electrode body can be smoothly discharged to the outside of the battery during abnormal heat generation of the battery.

[0007] It is an axial cross-sectional view of a cylindrical secondary battery which is an example of an embodiment.

[0008] A cylindrical secondary battery 10 which is an example of an embodiment will be described while referring to FIG. 1. FIG. 1 is an axial cross-sectional view of the cylindrical secondary battery 10.

[0009] As shown in Figure 1, the cylindrical secondary battery 10 comprises an electrode body 11, a non-aqueous electrolyte (not shown), an outer casing 20 that houses the electrode body 11 and the non-aqueous electrolyte, and a sealing body 30 that closes the opening 24 of the outer casing 20. Hereafter, the side of the cylindrical secondary battery 10 with the sealing body 30 in the axial direction (up and down direction) will be referred to as "up," and the side of the outer casing 20 with the bottom 21 in the axial direction will be referred to as "down."

[0010] The cylindrical secondary battery 10 further includes a positive electrode current collector plate 31 positioned above the electrode body 11 and welded to the sealing body 30, a negative electrode current collector plate 32 positioned below the electrode body 11 and welded to the outer casing 20, and an insulating plate 33 positioned between the electrode body 11 and the positive electrode current collector plate 31.

[0011] The electrode body 11 has a positive electrode, a negative electrode, and a separator (none of which are shown), and has a structure in which the positive electrode and the negative electrode are wound in a spiral shape with the separator in between. The positive electrode, the negative electrode, and the separator are all elongated strips, and are alternately stacked in the radial direction of the electrode body 11 by being wound in a spiral shape. The negative electrode is formed to be slightly larger in dimensions than the positive electrode in order to prevent lithium deposition. That is, the negative electrode is formed to be longer in the longitudinal direction and the width direction (short direction) than the positive electrode. The separator is formed to be at least slightly larger in dimensions than the positive electrode, and two separators are arranged so as to sandwich the positive electrode. A hollow portion 11A is formed at the winding center of the electrode body 11. The hollow portion 11A is a space that extends along the vertical direction.

[0012] The positive electrode comprises a positive electrode core and a positive electrode mixture layer formed on the positive electrode core. The positive electrode core can be made of a metal foil that is stable in the positive electrode potential range, 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, and is preferably formed on both sides of the positive electrode core, excluding the exposed portion of the positive electrode core to which the positive electrode tab 12 is welded. The positive electrode can be 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.

[0013] The positive electrode composite layer contains particulate lithium metal composite oxide as the positive electrode active material. The lithium metal composite oxide is a composite oxide containing metal elements such as Co, Mn, Ni, and Al in addition to Li. The metal elements constituting the lithium metal composite oxide are, for example, at least one selected from Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, and Bi. Among these, it is preferable to contain at least one selected from Co, Ni, and Mn. Examples of suitable composite oxides include lithium metal composite oxides containing Ni, Co, and Mn, and lithium metal composite oxides containing Ni, Co, and Al.

[0014] Examples of conductive agents included in the positive electrode mixture layer include carbon black such as acetylene black and Ketjenblack, graphite, carbon nanotubes (CNTs), carbon nanofibers, and graphene. Examples of binders included in the positive electrode mixture layer include fluorine-containing resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resins, and polyolefins. In addition, these resins may be used in combination with carboxymethylcellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

[0015] The negative electrode comprises a negative electrode core and a negative electrode mixture layer formed on the negative electrode core. The negative electrode core can be made of a metal foil that is stable in the negative electrode potential range, such as copper or a copper alloy, or a film with the metal arranged on its surface. The negative electrode mixture layer contains a negative electrode active material, a binder, and optionally a conductive agent, and is preferably formed on both sides of the negative electrode core, excluding the exposed portion 11B of the negative electrode core described later. The negative electrode can be manufactured by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to the surface of the negative electrode core, drying the coating, and then compressing it to form the negative electrode mixture layer on both sides of the negative electrode core.

[0016] The negative electrode composite layer generally contains a carbon material that reversibly intercepts and releases lithium ions as the negative electrode active material. Suitable examples of carbon materials include natural graphite such as flake graphite, lumpy graphite, and clay graphite, as well as artificial graphite such as lumpy artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB). In addition, a material containing at least one of an element that alloys with Li, such as Si or Sn, and a material containing such an element may be used as the negative electrode active material. Among these, composite materials containing Si are preferred.

[0017] A suitable example of a composite material containing Si is SiO ２ Examples include materials in which Si nanoparticles are dispersed in a phase or a silicate phase such as lithium silicate, or materials in which Si nanoparticles are dispersed in an amorphous carbon phase. A conductive layer, such as a carbon film, is formed on the particle surface of the composite material.

[0018] The binder in the negative electrode mixture layer may be a fluororesin, PAN, polyimide, acrylic resin, polyolefin, etc., similar to the positive electrode mixture layer, but styrene-butadiene rubber (SBR) is preferred. Furthermore, the negative electrode mixture layer preferably contains CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), etc. Among these, a combination of SBR and CMC or a salt thereof, PAA or a salt thereof is preferred. The negative electrode mixture layer may also contain a conductive agent such as CNT.

[0019] A porous sheet having ion permeability and insulating properties is used as the separator. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator include polyethylene, polyolefins such as polypropylene, and cellulose. The separator may have a single-layer structure or a multi-layer structure. A heat-resistant resin layer, such as aramid resin, may be formed on the surface of the separator. A filler layer containing an inorganic filler may be formed at the interface between the separator and at least one of the positive and negative electrodes.

[0020] A positive electrode tab 12 is connected to the positive electrode. The positive electrode tab 12 extends towards the sealing body 30 through a through hole 33B provided in the insulating plate 33. The positive electrode tab 12 is welded to the upper surface of the positive electrode current collector plate 31 and electrically connected to the sealing body 30. Therefore, the sealing body 30 becomes the positive electrode terminal. There may be only one positive electrode tab 12, but it is preferable to have multiple tabs from the viewpoint of reducing battery resistance. The number of positive electrode tabs 12 is, for example, two or more and eight or less. Figure 1 shows two positive electrode tabs 12.

[0021] In this embodiment, the lower end of the negative electrode is provided with a negative electrode core exposed portion 11B in which the negative electrode core is exposed. The negative electrode core exposed portion 11B is connected to the upper surface of the negative electrode current collector plate 32 by welding or the like, and is electrically connected to the outer casing 20. Thus, the outer casing 20 becomes the negative electrode terminal. Note that the current collection method is not limited to this, and the negative electrode and the outer casing 20 may be electrically connected via a negative electrode tab or the like. Alternatively, the negative electrode core may be placed on the outermost surface of the electrode body 11, and the negative electrode and the outer casing 20 may be electrically connected by bringing the negative electrode core on the outermost surface into contact with the inner surface of the outer casing 20.

[0022] The non-aqueous electrolyte contained in the outer container 20 is lithium ion conductive. The non-aqueous electrolyte may be a liquid electrolyte (electrolyte solution) or a solid electrolyte.

[0023] A liquid electrolyte (electrolyte solution) comprises 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. The non-aqueous solvent may also contain halogen-substituted compounds (e.g., fluoroethylene carbonate) in which at least some of the hydrogen atoms in the solvent are replaced with halogen atoms such as fluorine. Examples of electrolyte salts include lithium salts such as LiPF6.

[0024] As the solid electrolyte, for example, a solid or gel-like polymer electrolyte, an inorganic solid electrolyte, etc., can be used. As the inorganic solid electrolyte, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, etc.) can be used. The polymer electrolyte includes, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As the matrix polymer, for example, a polymer material that absorbs a non-aqueous solvent and gels is used. Examples of polymer materials include fluororesins, acrylic resins, polyether resins, etc.

[0025] The outer casing 20 is a bottomed cylindrical metal container with an open top. The outer casing 20 has a bottom 21 and side portions 22 that form the sides of the cylindrical secondary battery 10. The side portions 22 are the parts of the outer casing 20 excluding the bottom 21 and include grooved portions 23 and openings 24, which will be described later.

[0026] The bottom portion 21 is provided with a discharge valve 21A that opens when the internal pressure of the battery reaches a predetermined pressure. When the internal pressure of the battery rises due to abnormal heat generation, battery components such as the electrode body 11 are discharged to the outside through the discharge valve 21A. This reduces the temperature of the battery that has experienced abnormal heat generation. As a result, in a module using multiple batteries, it is possible to suppress the increase in the temperature of the batteries surrounding the battery that has experienced abnormal heat generation.

[0027] In this embodiment, a groove 21B is formed in the bottom portion 21, and the portion surrounded by the groove 21B becomes a discharge valve 21A. The groove 21B may be C-shaped or the like when viewed from the bottom, but it is preferable to form it in a circular shape when viewed from the bottom, from the viewpoint of improving fracture resistance when the internal pressure rises. The groove 21B is, for example, an imprint formed on the outer surface side of the bottom portion 21. The depth of the groove 21B is, for example, 50% or more and 90% or less of the thickness of the bottom portion 21. Multiple discharge valves 21A may be provided, but preferably one is provided in the radial center of the bottom portion 21.

[0028] Furthermore, in this embodiment, the bottom portion 21 has a shape in which the region on the radially central side is recessed upward relative to the radially outer region. However, the shape of the bottom portion 21 is not limited to this, and the inner surface of the bottom portion 21 may be flat throughout its plane.

[0029] The grooved portion 23 is a part of the side surface 22 that is recessed radially inward, and is provided in an annular shape along the circumferential direction of the outer can 20. The grooved portion 23 supports the sealing body 30 and the positive electrode current collector plate 31 on its upper surface. The grooved portion 23 can be formed, for example, by spinning a part of the side surface 22 radially inward to create an annular recess toward the radially inward side.

[0030] The opening 24 is located in the area of ​​the side portion 22 above the grooved portion 23, and forms the opening of the outer can 20. The opening 24 is bent radially inward when the sealing body 30 and the positive electrode current collector plate 31 are crimped and fixed to the outer can 20.

[0031] The sealing body 30 is a disc-shaped metal component. The sealing body 30 is crimped and fixed to the opening 24 of the outer can 20 via a gasket 35. The sealing body 30 is made of a metal, for example, aluminum as the main component.

[0032] The sealing body 30 has a protrusion 30A in its radial center. The protrusion 30A has a circular shape when viewed from above. Wiring material is connected to the upper surface of the protrusion 30A when modularizing the cylindrical secondary battery 10. The diameter of the protrusion 30A is not particularly limited, but for example, it is 25% or more and 60% or less of the diameter of the sealing body 30.

[0033] The positive electrode current collector plate 31 is a disc-shaped metal member having an outer diameter similar to that of the sealing body 30. The positive electrode current collector plate 31 is crimped and fixed to the opening 24 of the outer can 20 via a gasket 35. The positive electrode current collector plate 31 is made of a metal mainly composed of aluminum, similar to the sealing body 30. In this embodiment, the positive electrode current collector plate 31 has a substantially uniform thickness in its plane. The thickness of the positive electrode current collector plate 31 is, for example, 0.3 mm or more and 1.0 mm or less.

[0034] The positive electrode current collector plate 31 has an opening 31A in its radial center. The opening 31A is a through hole for passing the positive electrode tab 12 through, and also a through hole for arranging the compression coil spring 50, which will be described later. The opening 31A is formed, for example, in a substantially circular shape in plan view. The center of the circle of the opening 31A is located on the extension of the central axis (winding axis) of the electrode body 11. The diameter of the opening 31A is larger than the diameter of the compression coil spring 50, for example, 30% or more and 70% or less of the diameter of the positive electrode current collector plate 31.

[0035] The positive electrode current collector plate 31 is bent upward at a position radially outward from the periphery of the opening 31A. The height of the step formed at the bend is, for example, 0.3 mm or more and 1.5 mm or less. A portion of the area radially outward from the bend is welded to the sealing body 30 by laser welding or the like. The welded portion between the sealing body 30 and the positive electrode current collector plate 31 may be formed, for example, in a continuous annular shape, or multiple welds may be formed intermittently on the same circumference. The positive electrode tab 12 is welded to the upper surface of the area radially inward from the bend of the positive electrode current collector plate 31.

[0036] In this embodiment, an annular metal plate 34 is placed between the sealing body 30 and the positive electrode current collector plate 31. The positive electrode tab 12 is sandwiched between the positive electrode current collector plate 31 and the metal plate 34. The metal plate 34 is made of a metal mainly composed of aluminum, similar to the positive electrode current collector plate 31. By sandwiching the positive electrode tab 12 between the positive electrode current collector plate 31 and the metal plate 34, the positive electrode tab 12 is less likely to come off the surface of the positive electrode current collector plate 31, and the workability when welding the positive electrode tab 12 can be improved. The shape of the metal plate 34 is not particularly limited. Also, the cylindrical secondary battery 10 does not need to have the metal plate 34.

[0037] A negative electrode current collector plate 32 is provided at the lower part of the electrode body 11. The negative electrode current collector plate 32 is joined to the exposed negative electrode core portion 11B on its upper surface and to the outer casing 20 on its lower surface. The shape of the negative electrode current collector plate 32 is not particularly limited as long as it can electrically connect the exposed negative electrode core portion 11B and the outer casing 20. The negative electrode current collector plate 32 may have a shape in which the radial center portion protrudes downward, as in this embodiment, or it may be flat throughout its surface. Alternatively, the cylindrical secondary battery 10 may not have a negative electrode current collector plate 32, and the exposed negative electrode core portion 11B and the inner surface of the outer casing 20 may be directly welded together.

[0038] An insulating plate 33 is provided on the upper part of the electrode body 11. The material constituting the insulating plate 33 is not particularly limited and can be, for example, polypropylene (PP), polyethylene (PE), nylon (PA), etc. The insulating plate 33 has a substantially uniform thickness across its surface. The thickness of the insulating plate 33 is, for example, 0.1 mm or more and 2 mm or less.

[0039] In this embodiment, the insulating plate 33 has a through hole 33A in the radial center and a through hole 33B on the radial outer side. The through hole 33A has a circular shape in plan view, and the center of the circle of the through hole 33A is located on the extension of the central axis (winding axis) of the electrode body 11. The diameter of the through hole 33A is smaller than the diameter of the compression coil spring 50, which will be described later. The through hole 33B is a hole through which the positive electrode tab 12 passes, and is formed, for example, in an arc shape in plan view.

[0040] The gasket 35 is a flexible insulating member that electrically isolates the sealing body 30, which is the positive terminal, from the outer can 20, which is the negative terminal, while ensuring airtightness inside the outer can 20 when compressed. The material of the gasket 35 is not particularly limited as long as it is a compressible insulating material, and for example, polypropylene (PP), polyphenylene sulfide (PPS), polyethylene (PE), polybutylene terephthalate (PBT), perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), polyamide (PA), etc. can be used.

[0041] In this embodiment, the gasket 35 covers substantially the entire lower surface of the positive electrode current collector plate 31. Also, a part of the gasket 35 is inserted from below into the opening 31A of the positive electrode current collector plate 31 and covers the inner peripheral surface of the opening 31A of the positive electrode current collector plate 31. Note that the shape of the gasket 35 is not limited to this.

[0042] The outer surface of the opening 24 of the exterior can 20 is covered by the negative electrode cap 40. The negative electrode cap 40 is a portion where a wiring member is connected when modularizing the cylindrical secondary battery 10. The constituent material of the negative electrode cap 40 is not particularly limited, and for example, it is made of a metal mainly composed of iron or an alloy containing nickel. Also, an annular insulating member 41 that insulates each other is disposed between the negative electrode cap 40 and the sealing body 30. Note that the cylindrical secondary battery 10 may not have the negative electrode cap 40 and the insulating member 41.

[0043] As shown in FIG. 1, a compression coil spring 50 as a biasing portion is provided between the electrode body 11 and the sealing body 30. The upper surface of the compression coil spring 50 abuts against the lower surface of the convex portion 30A of the sealing body 30, and the lower surface abuts against the upper surface of the insulating plate 33. The compression coil spring 50 is housed inside the battery in a compressed state and biases the electrode body 11 downward. Thereby, when the discharge valve 21A is opened due to an increase in the internal pressure of the battery, the electrode body 11 can be smoothly discharged to the outside of the battery. As a result, the temperature of the battery in which an abnormality has occurred can be efficiently lowered, and an increase in the temperature of the surrounding batteries can be suppressed.

[0044] In this embodiment, as described above, the insulating plate 33 is disposed above the electrode body 11. Therefore, the compression coil spring 50 biases the electrode body 11 downward via the insulating plate 33. When the compression coil spring 50 biases the electrode body 11 downward via the insulating plate 33, the electrode body 11 is pressed over a wide range, so that when the discharge valve 21A is opened due to an increase in the internal pressure of the battery, the electrode body 11 can be discharged more smoothly to the outside of the battery.

[0045] In this embodiment, the compression coil spring 50 is a cylindrical coil spring having a cylindrical shape. Note that the shape of the compression coil spring 50 is not limited to this, and it may be a conical coil spring having a conical shape. The wire diameter of the compression coil spring 50 is not particularly limited, and for example, it is 0.1 mm or more and 1 mm or less. In addition, the number of turns of the compression coil spring 50 is not particularly limited, and for example, it is 3 or more and 15 or less.

[0046] The central portion in the radial direction of the compression coil spring 50 is located on the extension line of the central axis (winding axis) of the electrode body 11. Thereby, the electrode body 11 can be discharged to the outside of the battery more smoothly. Further, the center of the circle of the through hole 33A of the insulating plate 33 is located on the extension line of the central axis (winding axis) of the electrode body 11 as described above. Therefore, the central portion in the radial direction of the compression coil spring 50 overlaps with the center of the circle of the through hole 33A of the insulating plate 33 in the axial direction.

[0047] The outer diameter of the compression coil spring 50 is larger than the diameter of the through hole 33A of the insulating plate 33 and smaller than the diameter of the lower surface of the convex portion 30A of the sealing body 30. Note that the compression coil spring 50 may have an outer diameter larger than the diameter of the lower surface of the convex portion 30A of the sealing body 30, and the upper surface of the compression coil spring 50 may be in contact with the lower surface around the convex portion 30A.

[0048] Examples of the material of the compression coil spring 50 include materials containing a metal that is stable within the potential range of the positive electrode, such as aluminum. Further, the compression coil spring 50 may be made of a resin material having electrolyte resistance, such as polyether ether ketone (PEEK).

[0049] Note that the above embodiment can be changed within the scope of the object of the present disclosure. For example, the cylindrical secondary battery 10 may have a plurality of compression coil springs 50 as biasing portions. When the cylindrical secondary battery 10 has a plurality of compression coil springs 50, the plurality of compression coil springs 50 may be arranged at substantially equal angular intervals in a top view of the cylindrical secondary battery 10, for example.

[0050] Furthermore, the cylindrical secondary battery 10 does not necessarily have an insulating plate 33. In that case, the lower surface of the compression coil spring 50 abuts against the electrode body 11, and the compression coil spring 50 directly biases the electrode body 11 downwards. By omitting the insulating plate 33, the number of parts in the cylindrical secondary battery 10 is reduced, which can, for example, lead to lower costs.

[0051] Furthermore, although a compression coil spring 50 is used as the biasing part in the above embodiment, the biasing part is not limited to a compression coil spring 50 as long as it can bias the electrode body 11 downwards. The biasing part may be, for example, a rubber spring that utilizes the elastic force of rubber. The shape of the rubber spring is not particularly limited and examples include cylindrical, prismatic, and annular shapes. The material used for the rubber spring must be resistant to electrolytes.

[0052] The present disclosure is further illustrated by the following embodiments. Configuration 1: A cylindrical secondary battery comprising an electrode body in which a positive electrode and a negative electrode are wound with a separator between them, a bottomed cylindrical outer casing housing the electrode body, and a sealing body that closes the opening of the outer casing, wherein a discharge valve that opens when the internal pressure of the battery reaches a predetermined pressure is provided at the bottom of the outer casing, and a biasing portion that biases the electrode body toward the bottom is provided between the electrode body and the sealing body. Configuration 2: The cylindrical secondary battery according to Configuration 1, wherein the biasing portion includes a compression coil spring. Configuration 3: The cylindrical secondary battery according to Configuration 2, wherein the outer diameter of the compression coil spring is larger than the outer diameter of the hollow portion formed at the winding center of the electrode body. Configuration 4: The cylindrical secondary battery according to any one of Configurations 1 to 3, wherein the sealing body has a convex portion that protrudes radially outward from the battery, and the biasing portion abuts against the bottom side surface of the convex portion. Configuration 5: The cylindrical secondary battery according to any one of Configurations 1 to 4, wherein the biasing portion biases the electrode body toward the bottom side via a disc-shaped insulating plate. Configuration 6: The cylindrical secondary battery according to Configuration 5, wherein the biasing portion includes a compression coil spring, the insulating plate has a through hole in its radial center, and the outer diameter of the compression coil spring is larger than the diameter of the through hole.

[0053] 10 Cylindrical secondary battery (battery), 11 Electrode body, 11A Hollow section, 11B Exposed negative electrode core, 12 Positive electrode tab, 20 Outer casing, 21 Bottom section, 21A Discharge valve, 21B Groove, 22 Side section, 23 Grooved section, 24 Opening, 30 Sealing body, 30A Protrusion, 31 Positive electrode current collector plate, 31A Opening, 32 Negative electrode current collector plate, 33 Insulating plate, 33A Through hole, 33B Through hole, 34 Metal plate, 35 Gasket, 40 Negative electrode cap, 41 Insulating member, 50 Compression coil spring (biasing section)

Claims

1. A cylindrical secondary battery comprising: an electrode body in which a positive electrode and a negative electrode are wound with a separator between them; a bottomed cylindrical outer casing for housing the electrode body; and a sealing body for closing the opening of the outer casing, wherein a discharge valve is provided at the bottom of the outer casing that opens when the internal pressure of the battery reaches a predetermined pressure, and a biasing part is provided between the electrode body and the sealing body for biasing the electrode body toward the bottom.

2. The cylindrical secondary battery according to claim 1, wherein the biasing portion includes a compression coil spring.

3. The cylindrical secondary battery according to claim 2, wherein the outer diameter of the compression coil spring is larger than the outer diameter of the hollow portion formed at the winding center of the electrode body.

4. The cylindrical secondary battery according to claim 1, wherein the sealing body has a convex portion that protrudes outward from the battery at its radial center, and the biasing portion abuts against the bottom surface of the convex portion.

5. The cylindrical secondary battery according to claim 1, wherein the biasing portion biases the electrode body toward the bottom side via a disc-shaped insulating plate.

6. The cylindrical secondary battery according to claim 5, wherein the biasing portion includes a compression coil spring, the insulating plate has a through hole in its radial center, and the outer diameter of the compression coil spring is larger than the diameter of the through hole.

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