Cylindrical battery

Abstract

The objective of the present disclosure is to provide a cylindrical battery with which it is possible to reduce the number of components of a sealing body having the two safety functions of current interruption and exhaust. A cylindrical battery according to one embodiment of the present disclosure has a bottomed cylindrical outer casing can (20), and a sealing body (30) that closes the opening of the outer casing can (20). The sealing body (30) has: a rupture plate (31) in which an annular thin section (31A) is formed; and an annular insulation plate (32) positioned on the inner-surface side of the rupture plate (31) so as to face the thin section (31A). The rupture plate (31) includes a valve part (31B) surrounded by the thin section (31A), the valve part (31B) including a latching part (31D) that extends toward the radially outer side of the rupture plate (31) so as to cover at least the inner peripheral part of the inner surface of the insulation plate (32).

Description

[Technical Field]

[0001] The present disclosure relates to cylindrical batteries. [Background technology]

[0002] A cylindrical battery has a bottomed cylindrical outer can that houses an electrode assembly and an electrolyte, and a sealing body that closes the opening of the outer can (see, for example, Patent Document 1). In the sealing body of the cylindrical battery, a rupture plate and an internal terminal plate are stacked with an insulating plate interposed between them, and the rupture plate and the internal terminal plate are welded together to form a current path inside the sealing body. In the sealing body, if the internal pressure of the cylindrical battery increases in the event of an abnormality, the rupture plate deforms and breaks the internal terminal plate, interrupting the current path. If the internal pressure increases further, the rupture plate breaks, forming an outlet for gas inside the cylindrical battery. In other words, the sealing body has two safety functions: current interruption and exhaust. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 157749 Summary of the Invention [Problem to be solved by the invention]

[0004] The sealing body is composed of multiple parts made of metal and resin. Each part that makes up the sealing body needs to have a complex and highly accurate shape in order to activate the current interruption and exhaust in a stepwise manner. Parts with complex and highly accurate shapes increase the processing costs. In order to reduce the manufacturing costs of cylindrical batteries, it is necessary to reduce the number of parts in the sealing body.

[0005] An object of the present disclosure is to provide a cylindrical battery that can reduce the number of parts of a sealing body that has safety functions of current interruption and exhaust. [Means for solving the problem]

[0006] A cylindrical battery according to one aspect of the present disclosure is a cylindrical battery having an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, an electrolyte, a cylindrical outer can with a bottom that houses the electrode assembly and the electrolyte, and a sealing body that closes the opening of the outer can, wherein the sealing body has a rupture plate having a ring-shaped thin-walled portion formed thereon, and a ring-shaped insulating plate that is arranged on the inner surface side of the rupture plate so as to face the thin-walled portion, and the rupture plate includes a valve portion surrounded by the thin-walled portion, and the valve portion includes a locking portion that extends radially outward from the rupture plate so as to cover at least the inner periphery of the inner surface of the insulating plate. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, the number of parts of a sealing body having the safety functions of current interruption and exhaust can be reduced. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a cylindrical battery according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of a sealing body according to an embodiment. [Figure 3] FIG. 3 is a cross-sectional view of a sealing body according to an embodiment when current is interrupted. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The shapes, materials, and quantities described below are examples for the purpose of explanation and can be changed as appropriate depending on the specifications of the cylindrical battery. In the following, the same reference numerals will be used to designate equivalent elements in all drawings.

[0010] A cylindrical battery 10 as an example of an embodiment will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view of the cylindrical battery 10.

[0011] 1, a cylindrical battery 10 includes an electrode assembly 14, an electrolyte, an outer can 20 that houses the electrode assembly 14 and the electrolyte, and a sealing body 30 that closes the opening of the outer can 20. The electrode assembly 14 includes a positive electrode 11, a negative electrode 12, and a separator 13, and has a structure in which the positive electrode 11 and the negative electrode 12 are spirally wound with the separator 13 interposed therebetween. For ease of explanation, the sealing body 30 side of the cylindrical battery 10 (the opening side of the outer can 20) will be referred to as the top, and the bottom surface 20A side of the outer can 20 will be referred to as the bottom.

[0012] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer formed on at least one surface of the core. The positive electrode core can be made of a foil of a metal, such as aluminum or an aluminum alloy, that is stable within the potential range of the positive electrode 11, or a film with such a metal disposed on the surface. The positive electrode mixture layer contains a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride, and is preferably formed on both sides of the positive electrode core. For example, a lithium transition metal composite oxide is used as the positive electrode active material. The positive electrode 11 can be manufactured by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, etc., onto the positive electrode core, drying the coating, and then compressing the coating to form a positive electrode mixture layer on both sides of the core.

[0013] The negative electrode 12 has a negative electrode core and a negative electrode mixture layer formed on at least one surface of the core. The negative electrode core can be a foil of a metal, such as copper or a copper alloy, that is stable within the potential range of the negative electrode 12, or a film with such a metal disposed on the surface. The negative electrode mixture layer contains a negative electrode active material and a binder, such as styrene-butadiene rubber (SBR), and is preferably formed on both sides of the negative electrode core. Examples of the negative electrode active material include graphite and silicon-containing compounds. The negative electrode 12 can be manufactured by applying a negative electrode mixture slurry containing a negative electrode active material and a binder onto the negative electrode core, drying the coating, and then compressing the coating to form a negative electrode mixture layer on both sides of the core.

[0014] For example, a non-aqueous electrolyte is used as the electrolyte. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous solvent may be an ester, an ether, a nitrile, an amide, or a mixed solvent of two or more of these. The non-aqueous solvent may contain a halogen-substituted compound in which at least a portion of the hydrogen atoms in these solvents are substituted with halogen atoms such as fluorine. The non-aqueous electrolyte is not limited to a liquid electrolyte, but may also be a solid electrolyte. The electrolyte salt may be, for example, a lithium salt such as LiPF6. The type of electrolyte is not particularly limited, and may also be an aqueous electrolyte.

[0015] Cylindrical battery 10 has insulating plates 15 and 16 disposed above and below electrode assembly 14. In the example shown in FIG. 1 , positive electrode lead 17 connected to positive electrode 11 passes through a through-hole in insulating plate 15 and extends toward sealing body 30, and negative electrode lead 18 connected to negative electrode 12 passes outside insulating plate 16 and extends toward bottom 20A of outer can 20. Positive electrode lead 17 is connected by welding or the like to the bottom surface of flange 31C (described later) of rupture plate 31 constituting sealing body 30, with rupture plate 31 serving as the positive electrode external terminal. Negative electrode lead 18 is connected by welding or the like to the inner surface of bottom 20A of outer can 20, with outer can 20 serving as the negative electrode external terminal.

[0016] As described above, the cylindrical battery 10 has an outer can 20 and a sealing body 30 that closes the opening of the outer can 20. The outer can 20 is a cylindrical metal container with a bottom, including a bottom portion 20A and a side portion 20B. The bottom portion 20A is disk-shaped, and the side portion 20B is cylindrical and formed along the outer periphery of the bottom portion 20A. The sealing body 30 has a rupture plate 31 that is crimped and fixed to the opening of the outer can 20 via a gasket 21.

[0017] The rupture plate 31 is supported by the grooved portion 20C of the outer can 20 and is fixed by crimping by the crimped portion 20D of the outer can 20. The grooved portion 20C is formed in a ring shape along the circumferential direction of the outer can 20, with part of the side surface portion 20B protruding inward near the opening of the outer can 20. The crimped portion 20D is formed in a ring shape along the circumferential direction of the outer can 20 at the open end.

[0018] The sealing body 30 will be described in detail with reference to Figures 2 and 3. Figure 2 is a cross-sectional view of the sealing body 30, and Figure 3 is a cross-sectional view of the sealing body 30 when current is interrupted.

[0019] As described above, the sealing body 30 is a member that closes the opening of the outer can 20. The sealing body 30 also has the function of interrupting the current path in the cylindrical battery 10 when the internal pressure of the cylindrical battery 10 rises due to an abnormality in the cylindrical battery 10, and venting gas inside the cylindrical battery 10 when the internal pressure rises further. As shown in Figure 2, the sealing body 30 has a rupture plate 31 formed with an annular thin-walled portion 31A, and an annular insulating plate 32 that is placed on the inner surface (bottom side) of the rupture plate 31 so as to face the thin-walled portion 31A.

[0020] The rupture plate 31 includes a valve portion 31B formed radially inward of the thin-walled portion 31A of the rupture plate 31, and a flange portion 31C formed radially outward of the thin-walled portion 31A of the rupture plate 31. The valve portion 31B also includes a locking portion 31D extending radially outward of the rupture plate 31 so as to cover the inner periphery of the bottom surface of the insulating plate 32.

[0021] Next, the current interruption and exhaust operation of the sealing body 30 will be described in detail. As shown in Figure 3, when the internal pressure rises due to an abnormality in the cylindrical battery 10, the internal pressure pushes the rupture plate 31 upward. At this time, the insulating plate 32 receives an upward force from the locking portion 31D, causing the outer surface (top surface) and inner surface (bottom surface) of the insulating plate 32 to adhere tightly to the stepped surface 31G and the locking portion 31D, respectively. This maintains the sealed state of the cylindrical battery 10 even if part of the thin-walled portion 31A is ruptured, causing the internal pressure to further increase and completely separate the valve portion 31B from the flange portion 31C. Because the valve portion 31B and the flange portion 31C are prevented from being electrically connected by the insulating plate 32, the current path between the valve portion 31B and the flange portion 31C is interrupted. It is sufficient that the cylindrical battery 10 is sealed when the thin-walled portion 31A is broken so that the internal pressure rises to the extent that the valve portion 31B can be completely separated from the flange portion 31C.

[0022] If the internal pressure of the cylindrical battery 10 increases further after the current path is interrupted, at least one of the locking portion 31D and the insulating plate 32 will deform or break, blowing off the valve portion 31B and forming an exhaust port in the rupture plate 31. Gas inside the cylindrical battery 10 will be released from this exhaust port.

[0023] The rupture plate 31 is formed in a substantially circular plate shape in a plan view, and is produced by pressing a plate material made of aluminum or an aluminum alloy, for example.

[0024] The thinned portion 31A is the portion of the rupture plate 31 that breaks when the internal pressure of the cylindrical battery 10 rises due to an abnormality in the cylindrical battery 10. The thinned portion 31A is formed in a ring shape when viewed from above. The thinned portion 31A is formed in a U-shape or V-shape when viewed in cross section.

[0025] Valve portion 31B is formed in a substantially disk shape surrounded by thin portion 31A. Valve portion 31B includes a locking portion 31D formed at the lower end and a side peripheral surface 31E.

[0026] The flange portion 31C is a portion that is supported by the grooved portion 20C of the outer can 20 and is fixed by crimping with the crimping portion 20D of the outer can 20. The positive electrode lead 17 described above is connected to the bottom surface of the flange portion 31C by welding or the like.

[0027] The locking portion 31D extends radially outward from the rupture plate 31 so as to cover the inner surface of the insulating plate 32. The locking portion 31D does not need to cover the entire inner surface of the insulating plate 32, but it is preferable that the locking portion 31D cover at least the inner periphery of the inner surface of the insulating plate 32. Therefore, it is preferable that the locking portion 31D be formed in a ring shape around the side periphery 31E in a plan view. This prevents gas from escaping from between the inner surface of the insulating plate 32 and the locking portion 31D when the thin-walled portion 31A breaks.

[0028] To ensure that the cylindrical battery 10 remains sealed when the thin-walled portion 31A breaks, it is more preferable that the locking portion 31D be formed so that the radially outer tip surface 31F of the locking portion 31D is positioned radially outward of the thin-walled portion 31A.

[0029] Step surface 31G comes into close contact with the outer surface of the insulating plate when thin portion 31A breaks. This prevents gas from escaping between the outer surface of insulating plate 32 and step surface 31G when thin portion 31A breaks. Step surface 31G is formed by cutting out an annular shape on the inner periphery of the bottom surface of flange portion 31C. It is sufficient for step surface 31G to have the function of preventing gas from escaping between the outer surface of the insulating plate and rupture plate 31 when thin portion 31A breaks, and it is not necessarily necessary to provide a step between flange portion 31C and step surface 31G.

[0030] The insulating plate 32 is formed in a ring shape in a plan view. The insulating plate 32 is positioned with a gap between the top surface of the insulating plate 32 and the bottom surface of the thin-walled portion 31A and the stepped surface 31G of the flange portion 31C. This gap is not essential. From the perspective of ensuring a sealed state of the cylindrical battery 10 in the event of rupture of the thin-walled portion 31A, it is preferable that the peripheral side portion 31E be press-fitted into the opening of the insulating plate 32.

[0031] Cylindrical battery 10 allows the number of parts in sealing body 30 to be reduced while maintaining the safety functions of current interruption and exhaust by rupture plate 31 and insulating plate 32. For example, compared to a conventional sealing body in which an insulating plate is interposed between the rupture plate and the internal terminal plate, the number of internal terminal plates can be reduced. This reduces the manufacturing cost of sealing body 30.

[0032] Furthermore, compared to conventional sealing bodies in which a rupture plate and an internal terminal plate are welded to form a current path, cylindrical battery 10 reduces the number of welded locations and the number of manufacturing steps that involve welding, thereby reducing the manufacturing cost of sealing body 30.

[0033] Furthermore, with the cylindrical battery 10, the thickness of the sealing body 30 can be reduced while maintaining the safety functions of current interruption and exhaust. This allows the volume occupied by the electrode body 14 inside the cylindrical battery 10 to be increased, and ultimately the energy density of the cylindrical battery 10 to be increased.

[0034] The present invention is not limited to the above-described embodiment and its variations, and various modifications and improvements are possible within the scope of the claims of the present application. For example, in the present embodiment, the rupture plate 31 disposed on the outermost part of the sealing body 30 serves as the positive electrode external terminal, but this is not limiting. For example, a cap may be disposed on the outermost part of the sealing body 30 and serve as the positive electrode external terminal.

[0035] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to these examples.

[0036] <Example> [Making the sealing body] A rupture plate was produced by pressing an aluminum plate. A roughly annular thin-walled portion was formed in the center of the rupture plate, with the radially inner side of the thin-walled portion serving as the valve portion and the radially outer side serving as the flange portion. A circular locking portion was formed along the side periphery at the lower end of the valve portion. A stepped surface was formed on the radially inner side of the inner surface of the flange portion. The side periphery of the valve portion was press-fitted into a roughly annular insulating plate made of polymer resin so that the insulating plate faced the thin-walled portion, to produce a sealing body.

[0037] <Comparative Example> A sealing body was fabricated in the same manner as the sealing body of the example, except that no locking portion was formed at the lower end of the valve portion.

[0038] [Operating pressure measurement] Sealing bodies of the examples and comparative examples were prepared, and the operating pressures at which the current interruption mechanism and exhaust mechanism were activated were measured. The sealing bodies were fixed to a test apparatus so that nitrogen gas was supplied from the inner surface (bottom side) of the sealing body. At this time, the inner surface of the sealing body and the nitrogen gas supply path formed a sealed space. Nitrogen gas was then supplied to the inner surface of the sealing body, and the operating pressure (current interruption pressure) at the time the current path between the valve portion and the flange portion was interrupted and the operating pressure (exhaust pressure) at the time the exhaust port was formed were measured. The results are summarized in Table 1.

[0039] [Table 1]

[0040] In the example, the current interrupt pressure and exhaust pressure were 2.5 MPa and 3.0 MPa, respectively. That is, when the internal pressure of the battery reached 2.5 MPa, the valve portion completely separated from the flange portion, interrupting the current path, and the battery maintained its hermeticity until the internal pressure reached 3.0 MPa. Then, when the internal pressure reached 3.0 MPa, the valve portion was blown off, forming an exhaust port. In other words, it can be seen that the battery maintained its hermeticity from the time the thin-walled portion broke until the time the exhaust port was formed.

[0041] On the other hand, in the comparative example, only an exhaust pressure of 2.5 MPa was measured, and no current interruption pressure was measured. That is, in the comparative example, because no locking portion was formed, when a part of the thin-walled portion broke, the battery was not sealed, and the valve portion was not completely separated from the flange portion, and gas inside the battery was released. From the above results, it can be seen that by providing a locking portion as in the example, the sealing body can achieve the safety functions of current interruption and exhaust. [Explanation of symbols]

[0042] 10 cylindrical battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 15 insulating plate, 16 insulating plate, 17 positive electrode lead, 18 negative electrode lead, 20 outer can, 20A bottom portion, 20B side portion, 20C grooved portion, 20D crimped portion, 21 gasket, 30 sealing body, 31 rupture plate, 31A thin portion, 31B valve portion, 31C flange portion, 31D locking portion, 31E side peripheral surface, 31F tip surface, 31G stepped surface, 32 insulating plate.

Claims

[Claim 1] A cylindrical battery comprising: an electrode assembly in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; an electrolyte; a cylindrical outer can with a bottom that houses the electrode assembly and the electrolyte; and a sealing body that closes an opening of the outer can, The sealing body has a rupture plate having an annular thin portion formed thereon, and an annular insulating plate arranged on the inner surface side of the rupture plate so as to face the thin portion, the rupture plate includes a valve portion surrounded by the thin-walled portion, the valve portion includes a locking portion extending radially outward from the rupture plate so as to cover at least an inner circumferential portion of the inner surface of the insulating plate, The tip position of the locking portion is located radially outward of the rupture plate relative to the thin-walled portion. Cylindrical battery.

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