Sealed battery

Abstract

The present disclosure provides a sealed battery with improved reliability. A sealed battery (10) according to the present disclosure comprises: an electrode body (14); an electrolytic solution; a bottomed cylindrical battery case (15) that accommodates the electrode body (14) and the electrolytic solution; and a sealing body (16) that closes an opening of the battery case (15). The sealing body (16) is configured by stacking a bottom plate (23), a PTC element (24), and a terminal cap (25) in this order from the lower side to the upper side in the axial direction. The bottom plate (23) has a flat section (23D) that protrudes toward the lower side in the axial direction and a protrusion that protrudes toward the upper side in the axial direction from the flat section (23D).

Description

Sealed Battery

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

[0002] The sealed battery includes, for example, an electrode body, an electrolytic solution, a bottomed cylindrical battery case that houses the electrode body and the electrolytic solution, and a sealing body that closes the opening of the battery case. The sealing body is configured by laminating a bottom plate, a PTC element, and a terminal cap in this order from the lower side to the upper side in the axial direction. Further, in the sealed battery, the sealing body is caulked and fixed at the opening of the battery case.

[0003] In the sealed battery, when caulking and fixing the sealing body, the PTC element is pressurized, so the operability of the PTC element may decrease. Therefore, for example, Patent Document 1 discloses a configuration in which a flat portion protruding downward from the bottom plate and separated from the PTC element is formed. Thereby, when caulking and fixing the sealing body, the PTC element can receive no reaction force from the bottom plate, and the pressurized area of the PTC element can be reduced.

[0004] Japanese Patent Translation of PCT International Publication No. 2010 - 522963

[0005] Here, in the sealing body, the terminal cap and the bottom plate are made of metal members, and the PTC element is mainly made of a resin material, and further made of a metal member, conductive particles, etc. In the sealing body of Patent Document 1, since the flat portion of the bottom plate is separated from the PTC element, when caulking and fixing the sealing body, the PTC element may warp and the outer diameter of the PTC element may become smaller. In this case, the reliability of the sealed battery may decrease.

[0006] Therefore, an object of the present disclosure is to provide a sealed battery capable of improving reliability.

[0007] The sealed battery according to the present disclosure includes an electrode body, an electrolytic solution, a bottomed cylindrical battery case that houses the electrode body and the electrolytic solution, and a sealing body that closes the opening of the battery case. In the sealing body, a bottom plate, a PTC element, and a terminal cap are laminated in this order from one side to the other side in a first direction, and the bottom plate has a first protrusion protruding from one side in the first direction and a second protrusion protruding from the first protrusion to the other side in the first direction.

[0008] The sealed battery of this disclosure can improve reliability.

[0009] This is an axial cross-sectional view showing a sealed battery, which is an example of an embodiment. This is a detailed view of part A in Figure 1. This is a perspective view showing a base plate, which is an example of an embodiment. This is an axial cross-sectional view showing stacked base plates. This is a perspective view showing a base plate, which is another example of an embodiment.

[0010] An example of an embodiment of this disclosure will be described in detail below. In the following description, specific shapes, materials, directions, numerical values, etc., are examples provided to facilitate understanding of this disclosure and can be modified as appropriate to suit the application, purpose, specifications, etc.

[0011] [Sealed Battery] An example of a sealed battery 10, which is an embodiment, will be described using Figure 1.

[0012] The sealed battery 10 is, for example, a lithium primary battery. However, the sealed battery of this disclosure is not limited to a lithium primary battery. The sealed battery of this disclosure may be, for example, a secondary battery, a battery using an aqueous electrolyte, or a battery using a non-aqueous electrolyte. As will be described in detail later, the sealed battery 10 can improve reliability.

[0013] The sealed battery 10 comprises, as will be described in detail later, an electrode body 14, an electrolyte, a bottomed cylindrical battery case 15 that houses the electrode body 14 and the electrolyte, and a sealing body 16 that closes the opening of the battery case 15.

[0014] In the following, each component may be described using the axial (first direction), circumferential, and radial directions. Also, for the sake of convenience in the explanation, the side on which the sealing body 16 is provided may be described as the upper side, and the side on which the bottom 15B of the battery case 15 is formed may be described as the lower side.

[0015] The electrode body 14 is a wound type, constructed by winding a strip-shaped positive electrode and a strip-shaped negative electrode with a separator in between. The electrode body 14 has a shape that corresponds to the shape of the battery case 15. If the battery case is cylindrical, the electrode body is usually cylindrical.

[0016] The positive electrode typically includes a positive electrode current collector and a positive electrode mixture attached to the positive electrode current collector. The positive electrode mixture contains a positive electrode active material. When the sealed battery 10 is a lithium primary battery, manganese dioxide can be used as the positive electrode active material. As the positive electrode current collector, for example, expanded metal, net, or perforated metal made of stainless steel can be used. In addition to the positive electrode active material, the positive electrode mixture may also contain optional components such as a binder and a conductive agent. As the binder, a resin material such as fluororesin can be used. As the conductive agent, a conductive material such as a carbon material can be used.

[0017] A lithium metal (or lithium alloy) is used as the negative electrode. For example, a strip-shaped sheet of lithium metal or lithium alloy can be used as the negative electrode. Examples of lithium alloys that can be used include Li-Al, Li-Mg, Li-Al-Mg, Li-Sn, Li-Ni-Si, and Li-Pb. In particular, it is preferable to use a Li-Al-Mg alloy. When a lithium alloy is used, the content of metallic elements other than lithium in the lithium alloy is preferably 0.1% by mass or more and 5% by mass or less, from the viewpoint of ensuring sufficient discharge capacity and stabilizing internal resistance.

[0018] As separators, for example, microporous membranes made of resin, nonwoven fabrics, etc., can be used. As separator materials, for example, polyolefins, polyamides, polyamide-imides, etc., can be used. As polyolefins, polyethylene (PE), polypropylene (PP), laminates of PP and PE, etc., can be used.

[0019] As the electrolyte, a non-aqueous solvent in which a lithium salt is dissolved can be used. Examples of non-aqueous solvents include propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, and γ-butyrolactone. Examples of lithium salts include lithium borofluoride, lithium hexafluoride phosphate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide.

[0020] The sealed battery 10 has insulating plates 17 and 18 positioned above and below the electrode body 14, respectively. In the example shown in Figure 1, the positive electrode lead 19 connected to the positive electrode extends through a through hole in the insulating plate 17 towards the sealing body 16, and the negative electrode lead 20 connected to the negative electrode extends through a through hole in the insulating plate 18 towards the bottom 15B of the battery case 15. The positive electrode lead 19 is connected by welding or the like to the bottom surface of the flat portion 23D of the bottom plate 23 that constitutes the sealing body 16, and the terminal cap 25 becomes the positive electrode external terminal. The negative electrode lead 20 is connected by welding or the like to the inner surface of the bottom 15B of the battery case 15, and the battery case 15 becomes the negative electrode external terminal.

[0021] The battery case 15 is a bottomed cylindrical metal container with an open top. The material of the battery case 15 is not particularly limited and includes, for example, iron, iron alloys (including stainless steel), aluminum, aluminum alloys (alloys containing trace amounts of other metals such as manganese and copper). The battery case 15 has a cylindrical tubular portion 15A, a circular bottom portion 15B when viewed from the bottom, a shoulder portion 15C formed in an annular shape along the circumferential direction of the battery case 15 at the open end of the tubular portion 15A, and a groove portion 15D formed along the circumferential direction of the tubular portion 15A.

[0022] The groove 15D is formed near the opening of the battery case 15, at a predetermined distance from the shoulder portion 15C. The groove 15D is a portion of the cylindrical portion 15A that protrudes inward from the battery case 15, and is formed, for example, by spinning the cylindrical portion 15A from the outside. At the position where the groove 15D is formed, the battery case 15 is reduced in diameter, and a fine linear groove is formed on the outer circumferential surface of the cylindrical portion 15A. The groove 15D preferably has a substantially U-shaped cross-section and is formed in an annular shape along the entire circumferential length of the cylindrical portion 15A.

[0023] A thin, explosion-proof section 15E is formed at the bottom 15B of the battery case 15. The thin, explosion-proof section 15E preferentially ruptures when an abnormality occurs in the sealed battery 10 and the internal pressure rises. This creates a gas outlet at the bottom 15B of the battery case 15. The thin, explosion-proof section 15E is formed in a predetermined shape on the outside of the bottom 15B of the battery case 15. The thin, explosion-proof section 15E may be formed in a linear shape (line segment, arc shape, etc.) when the bottom 15B of the battery case 15 is viewed from the outside of the case.

[0024] The gasket 21 is a rubber or resin component that prevents contact between the sealing body 16 and the battery case 15, thereby ensuring electrical insulation between the battery case 15 and the sealing body 16. The gasket 21 also seals the gap between the battery case 15 and the sealing body 16, thereby sealing the inside of the sealed battery 10.

[0025] [Sealing Body] An example of an embodiment, a sealing body 16, will be described using Figures 1 and 2.

[0026] The sealing body 16 is formed in a disc shape overall and has a bottom plate 23, a PTC element 24, and a terminal cap 25. The sealing body 16 is placed on the groove 15D of the battery case 15 and fixed to the upper end of the battery case 15. More specifically, the shoulder portion 15C of the battery case 15 is bent radially inward and crimped to the sealing body 16, so that the sealing body 16 is fixed to the upper end of the battery case 15 by the shoulder portion 15C and the groove 15D of the battery case 15, and the sealing body 16 closes the opening of the battery case 15.

[0027] The sealing body 16 is constructed by stacking a bottom plate 23, a PTC element 24, and a terminal cap 25 in order from the bottom to the top in the axial direction.

[0028] [Bottom Plate] A bottom plate 23, which is an example of an embodiment, will be described using Figures 1 to 5.

[0029] As shown in Figure 1, the bottom plate 23 constitutes the lowest part of the sealing body 16. The bottom plate 23, as will be described in detail later, can improve the reliability of the sealed battery 10. Furthermore, as will be described in detail later, it can improve the productivity of the sealed battery 10.

[0030] As shown in Figures 2 and 3, the bottom plate 23 has a flange portion 23A that is crimped to the upper end of the battery case 15, a first projection 23B that protrudes downward in the axial direction, and a second projection 23C that protrudes upward in the axial direction from the first projection 23B. The first projection 23B includes a flat portion 23D spaced apart from the PTC element 24 and an inclined portion 23E connecting the flange portion 23A and the flat portion 23D. The second projection 23C protrudes upward in the axial direction from the flat portion 23D. Here, on the back surface of the protruding surfaces of the first projection 23B and the second projection 23C, the area overlapping the first projection 23B and the second projection 23C is recessed. Also, in the radial direction of the sealed battery 10, the first projection 23B and the second projection 23C are formed inward from the flange portion 23A. The material of the base plate 23 is not particularly limited and includes, for example, iron, iron alloy (including stainless steel), aluminum, aluminum alloy, etc.

[0031] As shown in Figure 2, a thin-walled portion 23F, which is thinner than the flange portion 23A, may be formed on the outer edge of the flange portion 23A. The thin-walled portion 23F only needs to be formed in the portion that is crimped by the groove portion 15D of the battery case 15. This makes it possible to reduce the thickness of the crimped portion of the sealing body 16. As a result, the volume of the battery case 15 can be reduced, and the energy density of the sealed battery 10 can be improved. This makes it possible to improve the performance of the sealed battery 10.

[0032] In the sealed battery 10 of this embodiment, a thin-walled portion 21F is formed on the flange portion 23A of the bottom plate 23, and as will be described in detail later, a thin-walled portion 21F may also be formed on the flange portion 21A of the terminal cap 25. However, the sealed battery 10 of this disclosure is not limited thereto. In the sealed battery of this disclosure, a thin-walled portion may be formed only on the flange portion of the bottom plate, or a thin-walled portion may be formed only on the flange portion of the terminal cap.

[0033] As described above, the positive electrode lead 19 is connected to the bottom surface of the flat portion 23D by welding or the like. Also, as described above, the flat portion 23D is spaced apart from the PTC element 24. This allows the PTC element 24 to avoid receiving a reaction force from the bottom plate 23 when the sealing body 16 is crimped and fixed, thereby reducing the area of ​​pressure applied to the PTC element 24. As a result, a decrease in the operability of the PTC element 24 can be suppressed. Furthermore, because the flat portion 23D is spaced apart from the PTC element 24, the thermal influence on the PTC element 24 can be reduced when the positive electrode lead 19 is connected to the bottom surface of the flat portion 23D by welding or the like.

[0034] The second projection 23C is formed in the center of the flat portion 23D. In this embodiment, the second projection 23C is formed in a cylindrical shape with a diameter sufficiently smaller than the diameter of the bottom plate 23. The second projection 23C may contact the PTC element 24 (see Figure 1).

[0035] In this case, the sealing body 16 has terminal caps 25 and a bottom plate 23 made of metal, and the PTC element 24 is made of resin. However, because the flat portion 23D of the bottom plate 23 is spaced apart from the PTC element 24, the PTC element 24 may bend when the sealing body 16 is crimped and fixed, causing the outer diameter of the PTC element 24 to decrease. In this case, the reliability of the sealed battery 10 may be reduced.

[0036] In this embodiment, as described above, the bottom plate 23 has a second projection 23C that protrudes upward in the axial direction from the flat portion 23D, which suppresses the warping of the PTC element 24 when the sealing body 16 is crimped and fixed. This improves the reliability of the sealed battery 10. In the sealed battery of this disclosure, it is preferable that the PTC element does not come into contact with the second projection, but the PTC element may come into contact with the second projection. In particular, when a thin PTC element is used, some warping may occur in the PTC element even in the sealed battery of this disclosure. By having this thin PTC element come into contact with the second projection, further warping of this thin PTC element can be suppressed. Therefore, compared to a thin PTC element that constitutes a sealing body together with a bottom plate without the second projection, the reliability of this thin PTC element can be improved in the sealed battery of this disclosure.

[0037] Furthermore, in the manufacturing process of the sealed battery 10, the bottom plates 23 are stacked and temporarily stored, and may be removed one by one, for example, by a parts feeder. For example, in a configuration in which the second protrusion 23C is not formed on the bottom plate 23, the inclined portions 23E overlap each other, making it difficult for the bottom plates 23 to separate. In other words, it may be difficult to separate one bottom plate 23 from multiple stacked bottom plates 23.

[0038] As shown in Figure 4, in the bottom plate 23 of this embodiment, as described above, a second projection 23C is formed that protrudes upward in the axial direction from the flat portion 23D. Therefore, even when multiple bottom plates 23 are stacked, the inclined portions 23E do not overlap. This makes it easier for the bottom plates 23 to separate from each other. As a result, it becomes easier to separate one bottom plate 23 from multiple stacked bottom plates 23. This improves the productivity of the sealed battery 10.

[0039] [Other Embodiments (Bottom Plate)] As shown in Figure 5, the bottom plate 33 has a flange portion 33A that is crimped to the upper end of the battery case 15, a first projection 33B that protrudes downward in the axial direction, and a second projection 33C that protrudes upward in the axial direction from the first projection 33B. The first projection 33B includes a flat portion 33D spaced apart from the PTC element 24 and an inclined portion 33E that connects the flange portion 33A and the flat portion 33D. The second projection 33C protrudes upward in the axial direction from the flat portion 23D.

[0040] The second protrusions 33C are formed at approximately 90° intervals in a plan view on the inclined portion 33E. In this embodiment, the second protrusions 33C are formed in a rectangular shape in a plan view, for example. The second protrusions 33C are in contact with the PTC element 24. The bottom plate 33 provides the same effects as the bottom plate 23 described above.

[0041] [PTC Element] As shown in FIGS. 1 and 2 again, the PTC element 24, also called a thermal resistance element, has the property that its electrical resistance increases as the temperature rises. For example, when an abnormal current flows through the sealed battery 10, the temperature of the PTC element 24 rises due to heat generation, and accordingly, the resistance of the PTC element 24 increases. Thereby, the current flowing through the sealed battery 10 is decreased, and the abnormal heat generation of the sealed battery 10 is suppressed. According to the PTC element 24, the abnormal heat generation of the sealed battery 10 can be suppressed before the explosion-proof thin portion 15E cracks.

[0042] The PTC element 24 is formed in a disk shape or an annular shape. The PTC element 24 may include a composite of a resin and conductive particles. The PTC element 24 may have a structure in which such a composite layer is sandwiched between a pair of metal foils. As the resin, a polyethylene resin or the like can be used. As the metal foil, nickel, a clad material of copper and nickel, or a plated foil obtained by plating nickel on the surface of a copper foil can be used. In such a PTC element 24, when the resin expands due to heat generation, the distance between the conductive particles dispersed in the resin becomes larger, and the resistance of the composite (PTC element) increases.

[0043] Note that the configuration of the PTC element 24 is not particularly limited, and for example, a ceramic-based PTC element may be used. For example, a PTC element mainly composed of barium titanate may be used.

[0044] [Terminal Cap] The terminal cap 25 has, for example, a flange portion 25A caulked to the upper end portion of the battery case 15 and a protrusion 25B protruding axially upward from the inner edge of the flange portion 25A. In the protrusion 25B, in the back surface of the protruding surface, a region overlapping the protrusion 25B is recessed. The material of the terminal cap 25 is not particularly limited, and examples include iron, an iron alloy (including stainless steel), aluminum, an aluminum alloy, and the like.

[0045] On the outer edge of the flange portion 25A, as described above, a thin-walled portion 25F having a smaller thickness than the flange portion 25A may be formed. The thin-walled portion 25F may be formed at least in a portion caulked by the shoulder portion 15C of the battery case 15. Thereby, the thickness of the caulked portion of the sealing body 16 can be reduced. As a result, the volume of the battery case 15 can be decreased, and the energy density of the sealed battery 10 can be improved. As a result, the performance of the sealed battery 10 can be improved.

[0046] [Summary] The present invention will be further described by the following embodiments.

[0047] Configuration 1: A sealed battery including an electrode body, an electrolytic solution, a bottomed cylindrical battery case for housing the electrode body and the electrolytic solution, and a sealing body for closing an opening of the battery case, wherein the sealing body is configured by laminating a bottom plate, a PTC element, and a terminal cap in order from one side to the other side in a first direction, and the bottom plate has a first protrusion protruding to one side in the first direction and a second protrusion protruding from the first protrusion to the other side in the first direction.

[0048] Configuration 2: The sealed battery according to Configuration 1, wherein the first protrusion has a flange portion, a flat portion spaced apart from the PTC element, and an inclined portion connecting the flange portion and the flat portion, and the second protrusion is formed on the flat portion.

[0049] Configuration 3: The sealed battery according to Configuration 1, wherein the first protrusion has a flange portion, a flat portion spaced apart from the PTC element, and an inclined portion connecting the flange portion and the flat portion, and the second protrusion is formed on the inclined portion.

[0050] Configuration 4: The sealed battery according to any one of Configurations 1 to 3, wherein a thin-walled portion is formed at an edge of the terminal cap and / or the bottom plate.

[0051] Configuration 5: The sealed battery according to any one of Configurations 1 to 3, wherein the PTC element is formed in a disc shape or an annular shape.

[0052] Configuration 6; A sealed battery according to any one of Configurations 1 to 3, wherein a thin-walled explosion-proof portion is formed at the bottom of the battery case.

[0053] It should be noted that this disclosure is not limited to the embodiments and their modifications described above, and various changes and improvements are possible within the scope of the claims of this application.

[0054] 10 Sealed battery 14 Electrode body 15 Battery case 15A Cylindrical part 15B Bottom part 15C Shoulder part 15D Groove part 15E Explosion-proof thin-walled part 16 Sealing body 17 Insulating plate 18 Insulating plate 19 Positive lead 20 Negative lead 21 Gasket 23, 33 Bottom plate 23A, 33A Flange part 23B, 33B First protrusion 23C, 33C Second protrusion 23D, 33D Flat part 23E, 33E Inclined part 23F Thin-walled part 24 PTC element 24 Gasket 25 Terminal cap 25A Flange part 25B Protrusion 25F Thin-walled part

Claims

1. A sealed battery comprising an electrode body, an electrolyte, a bottomed cylindrical battery case containing the electrode body and the electrolyte, and a sealing body that closes the opening of the battery case, wherein the sealing body is constructed by stacking a bottom plate, a PTC element, and a terminal cap in order from one side to the other in a first direction, and the bottom plate has a first projection protruding to one side in the first direction and a second projection protruding from the first projection to the other side in the first direction.

2. A sealed battery according to claim 1, wherein the first projection has a flat portion spaced apart from the PTC element and an inclined portion connecting the flat portion, and the second projection is formed on the flat portion.

3. A sealed battery according to claim 1, wherein the first projection has a flat portion spaced apart from the PTC element and an inclined portion connected to the flat portion, and the second projection is formed on the inclined portion.

4. A sealed battery according to any one of claims 1 to 3, wherein a thin-walled portion is formed on the edge of the terminal cap and / or the bottom plate, as described in claim 1.

5. A sealed battery according to any one of claims 1 to 3, wherein the PTC element is formed in the shape of a disc or an annular ring.

6. A sealed battery according to any one of claims 1 to 3, wherein a thin-walled explosion-proof portion is formed at the bottom of the battery case.

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