Sealed battery

Abstract

A sealed battery according to one embodiment of the present invention is provided with: an electrode body in which a positive electrode (11) and a negative electrode (12) are laminated with a separator (13) interposed therebetween; a bottomed cylindrical outer can (20) having a bottom surface section (20A) and a side surface section (20B) and accommodating the electrode body; and a sealing body that closes the opening of the outer can (20). The outer can (20) has a thin portion (30) formed so that the inner surface of the side surface portion (20B) is recessed in the circumferential direction. In the height direction of the outer can (20), the lower end of the thin portion (30) is located between the bottom surface portion (20A) and the lower end of the positive electrode (11).

Description

Technical Field

[0001] The present disclosure relates to a sealed battery, and more particularly, to a sealed battery including a bottomed cylindrical outer can. Background Art

[0002] In the past, a sealed battery having a bottomed cylindrical outer can for accommodating an electrode body has been widely known. Patent document 1 discloses a sealed battery, which is constructed by using a bottomed cylindrical outer can with a notch formed on the bottom side of the can, so that when subjected to a load in the height direction, the outer can breaks at the notch. The battery is designed to prevent short circuits between electrodes that may occur when the outer can is compressed in the height direction and the electrode body is ejected from the outer can. Patent document 1 describes the following scheme: By ejecting the electrode body from the bottom side of the can opposite to the sealing body, short circuits between electrodes can be prevented.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-295576 Summary of the invention

[0006] As described above, when the outer can is subjected to a load in the height direction, there is a concern that irregular deformation of the side surface may occur, which may damage the electrode body. The sealed battery of Patent Document 1 has a notch portion in the outer can to limit the ejection direction of the electrode body, but there is still room for improvement in suppressing damage to the electrode body accompanying deformation of the outer can.

[0007] In order to solve the above-mentioned problems, the sealed battery involved in the present disclosure comprises: an electrode body, in which a positive electrode and a negative electrode are stacked with a separator; an outer can with a bottom cylindrical shape, having a bottom portion and a side portion, and accommodating the electrode body; and a sealing body, which blocks the opening of the outer can, and the outer can has a thin-walled portion, which is formed as a depression on the inner surface of the side portion along the circumferential direction, and in the height direction of the outer can, the lower end of the thin-walled portion is located between the bottom portion of the outer can and the lower end of the positive electrode.

[0008] According to the sealed battery according to the present disclosure, when the outer can is subjected to a load in the height direction, it is possible to suppress irregular deformation of the side surface of the outer can that may damage the electrode assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a cross-sectional view of a sealed battery as an example of an embodiment.

[0010] Figure 2 This is an enlarged cross-sectional view of a thin-walled portion and its vicinity as an example of an embodiment.

[0011] Figure 3 This is an enlarged cross-sectional view of a thin-walled portion as an example of an embodiment.

[0012] Figure 4 This is an enlarged cross-sectional view of a thin-walled portion and its vicinity as an example of an embodiment. DETAILED DESCRIPTION

[0013] As described above, in the conventional outer can having a side portion with uniform thickness, when a load acts in the height direction, the outer can bends, and the side portion is easily deformed irregularly, and the electrode body may be damaged due to the deformation. The inventors of the present invention have conducted intensive research to suppress the damage of the electrode body caused by the deformation of the outer can, and found that by forming a thin-walled portion as a depression on the inner surface of the side portion along the circumferential direction in the portion of the side portion of the outer can that is not opposed to both the positive electrode and the negative electrode, the damage of the electrode body caused by the deformation of the outer can can be suppressed.

[0014] In this case, when the sealed battery is subjected to a load in the height direction, the thin-walled portion is deformed first, and irregular deformation of the side portion can be suppressed. That is, the side portion of the outer can is deformed first in the portion that is not opposite to the positive electrode and the negative electrode. In addition, the thin-walled portion is formed as a depression in the inner surface of the side portion, so that the outer can is deformed to expand toward the outside of the sealed battery starting from the thin-walled portion, thereby more reliably suppressing damage to the electrode body caused by deformation of the outer can.

[0015] Hereinafter, an example of an embodiment of the present disclosure is described in detail. Hereinafter, as an example of an embodiment of the sealed battery involved in the present disclosure, a cylindrical battery in which a wound electrode body 14 is contained in an outer can 20 having a bottom cylindrical shape is illustrated, but the battery may also be a square battery having a square outer can with a bottom cylindrical shape. In addition, the electrode body may also be a stacked type in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with separators. In this specification, for the sake of convenience of explanation, the direction along the axial direction of the outer can 20 is set as the "up and down direction", the sealing body 19 side of the outer can 20 is set as the "up", and the bottom portion 20A side of the outer can 20 is set as the "down".

[0016] Figure 1 FIG. 1 is a cross-sectional view of a sealed battery 10 in the vertical direction as an example of an embodiment. Figure 1As shown, the sealed battery 10 includes an electrode body 14, an electrolyte, a bottomed cylindrical outer can 20 that accommodates the electrode body 14 and the electrolyte, and a sealing body 19 that blocks the opening of the outer can 20. The electrode body 14 includes a positive electrode 11, a negative electrode 12, and a separator 13 between the positive electrode 11 and the negative electrode 12, and has a winding structure in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween. The outer can 20 is a bottomed cylindrical container having a bottom portion 20A and a side portion 20B.

[0017] Although described in detail later, the outer can 20 has a thin wall portion 30 where the thickness of the side surface 20B is locally reduced. The thin wall portion 30 is formed as a depression on the inner surface of the side surface 20B along the circumferential direction and is an easily deformable portion that deforms preferentially when a vertical load acts on the sealed battery 10.

[0018] The electrolyte can be any of an aqueous electrolyte and a non-aqueous electrolyte. An example of a suitable sealed battery 10 is a non-aqueous electrolyte secondary battery such as a lithium ion battery using a non-aqueous electrolyte. The non-aqueous electrolyte, for example, includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. For the non-aqueous solvent, esters, ethers, nitriles, amides, and mixed solvents of two or more thereof are used. The non-aqueous solvent may also contain a halogen substituted body obtained by replacing at least a portion of the hydrogen of these solvents with a halogen atom such as fluorine. In addition, the non-aqueous electrolyte is not limited to a liquid electrolyte, and may also be a solid electrolyte using a gel-like polymer or the like. For the electrolyte salt, a lithium salt such as LiPF6 is used.

[0019] The electrode body 14 includes a long positive electrode 11, a long negative electrode 12, and two long separators 13. In addition, the electrode body 14 includes a positive electrode lead 17 connected to the positive electrode 11 and a negative electrode lead 18 connected to the negative electrode 12 as electrode leads. In order to suppress the precipitation of lithium, the negative electrode 12 is formed to be one size larger than the positive electrode 11. Therefore, the lower end of the negative electrode 12 is arranged to be closer to the bottom portion 20A of the outer can 20 than the lower end of the positive electrode 11. The two separators 13 are formed to be at least one size larger than the positive electrode 11, and are arranged to sandwich the positive electrode 11, for example.

[0020] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer arranged on both sides of the positive electrode core. For the positive electrode core, a foil of a metal such as aluminum or aluminum alloy that is stable within the potential range of the positive electrode 11, a film in which the metal is arranged on the surface, etc. can be used. The positive electrode mixture layer contains a positive electrode active material, a conductive material such as acetylene black, and a binding material such as polyvinylidene fluoride (PVdF). A positive electrode mixture slurry containing a positive electrode active material, a conductive material, and a binding material is applied to the positive electrode core, and after the coating is dried, it is compressed to form the positive electrode mixture layer on both sides of the positive electrode core, thereby making it possible to produce the positive electrode 11.

[0021] For the positive electrode active material, for example, a lithium transition metal composite oxide is used. As the metal elements contained in the lithium transition metal composite oxide, Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, W, etc. can be listed. An example of a suitable lithium transition metal composite oxide is a lithium metal composite oxide containing at least one of Ni, Co, and Mn. As a specific example, a composite oxide containing Ni, Co, and Mn and a composite oxide containing Ni, Co, and Al can be listed.

[0022] The negative electrode 12 has a negative electrode core and negative electrode mixture layers arranged on both sides of the negative electrode core. For the negative electrode core, a foil of a metal such as copper or copper alloy that is stable within the potential range of the negative electrode 12, a film in which the metal is arranged on the surface, etc. can be used. The negative electrode mixture layer contains a negative electrode active material and a binding material such as styrene butadiene rubber (SBR). A negative electrode mixture slurry containing a negative electrode active material and a binding material is applied to the negative electrode core, and after the coating is dried, it is compressed to form the negative electrode mixture layers on both sides of the negative electrode core, thereby making it possible to produce the negative electrode 12.

[0023] For the negative electrode active material, for example, natural graphite such as flaky graphite, block graphite, and earthy graphite, block artificial graphite, and artificial graphite such as graphitized mesophase carbon microbeads are used. For the negative electrode active material, metals such as Si and Sn alloyed with lithium, alloys containing the metals, compounds containing the metals, etc. can be used, and they can also be used in combination with graphite. An example of the active material is a Si-containing material in which Si particles are dispersed in a silicate phase such as SiO2 phase or lithium silicate, or an amorphous carbon phase.

[0024] Insulating plates 15 and 16 are disposed above and below the electrode body 14, respectively. Figure 1 In the example shown, the positive electrode lead 17 attached to the positive electrode 11 extends to the sealing body 19 side through the through hole of the insulating plate 15, and the negative electrode lead 18 attached to the negative electrode 12 extends to the bottom portion 20A side of the outer can 20 through the outside of the insulating plate 16. The positive electrode lead 17 is connected to the inner surface of the sealing body 19 facing the inner side of the outer can 20 by welding or the like, and the sealing body 19 serves as a positive electrode external terminal. The negative electrode lead 18 is connected to the inner surface of the bottom portion 20A of the outer can 20 by welding or the like, and the outer can 20 serves as a negative electrode external terminal.

[0025] The outer can 20 is a metal container in a cylindrical shape with a bottom and an opening on one side in the vertical direction. A gasket 24 is provided between the outer can 20 and the sealing body 19 to ensure the airtightness of the interior of the battery and the insulation between the outer can 20 and the sealing body 19. A groove 20C for supporting the sealing body 19 is formed in the outer can 20, in which a part of the side surface 20B extends inward. The groove 20C is preferably formed in an annular shape along the circumference of the outer can 20, and the sealing body 19 is supported by its upper surface. The sealing body 19 is fixed to the upper part of the outer can 20 by the groove 20C and the open end of the outer can 20 riveted to the sealing body 19.

[0026] As described above, the outer can 20 has a thin-walled portion 30 formed as a depression on the inner surface of the side portion 20B along the circumferential direction. As described in detail later, the thin-walled portion 30 is formed in the lower end of the side portion 20B in a portion that is not opposed to both the positive electrode 11 and the negative electrode 12 in the radial direction of the outer can 20. The thin-walled portion 30 can also be formed in a part of the side portion 20B in the circumferential direction of the side portion 20B, and the total length of the circumferential direction of the thin-walled portion 30 is preferably more than one-third of the length (circumference) of the circumferential direction of the inner surface of the side portion 20B, and more preferably more than half. In this case, when a load in the up-down direction acts on the outer can 20, the thin-walled portion 30 is deformed first, and it becomes easy to suppress the irregular deformation of the side portion 20B. In addition, the circumferential length of the thin-walled portion 30 can be measured based on the upper end of the thin-walled portion 30 in the inner surface of the side portion 20B.

[0027] In the case where the length of the thin-walled portion 30 along the circumference of the inner surface of the side portion 20B is shorter than the circumference of the side portion 20B, it is preferred that the thin-walled portion 30 is formed at a plurality of positions so that it is not biased in a part of the circumference of the inner surface of the side portion 20B, but is evenly present in the entire circumference. For example, the thin-walled portion 30 may be formed substantially at equal intervals along the circumference of the inner surface of the side portion 20B. In the present embodiment, the thin-walled portion 30 is formed over the entire circumference of the inner surface of the side portion 20B. That is, the thin-walled portion 30 is formed in an annular shape along the circumference of the inner surface of the side portion 20B. In this case, the above-mentioned irregular deformation suppression effect becomes more significant.

[0028] The sealing body 19 is a disc-shaped member having a current cutoff mechanism. The sealing body 19 has a structure in which an internal terminal plate 21, an insulating plate 23, and a break plate 22 are stacked in order from the electrode body 14 side. The internal terminal plate 21 is a metal plate including a thick-walled annular portion 21A connected to the positive lead 17 and a thin-walled central portion 21B that separates from the annular portion 21A when the internal pressure of the battery exceeds a given threshold. A vent hole 21C is formed in the annular portion 21A.

[0029] The break plate 22 and the internal terminal plate 21 are arranged opposite to each other with the insulating plate 23 sandwiched therebetween. The insulating plate 23 has an opening 23A formed in the radial center, and a vent hole 23B formed in a portion overlapping with the vent hole 21C of the internal terminal plate 21. The break plate 22 has a valve portion 22A that breaks when the internal pressure of the battery exceeds a given threshold, and the valve portion 22A is connected to the central portion 21B of the internal terminal plate 21 through the opening 23A of the insulating plate 23 by welding or the like. The insulating plate 23 insulates the portion other than the connection portion between the annular portion 21A and the central portion 21B of the valve portion.

[0030] The valve portion 22A includes a lower convex portion convex toward the inner side of the battery and a thin-walled portion formed around the lower convex portion, and is formed in the radial center of the rupture plate 22. In the sealed battery 10, the internal terminal plate 21 connected to the positive lead 17 is electrically connected to the rupture plate 22, thereby forming a current path from the electrode body 14 to the rupture plate 22. When an abnormality occurs in the battery and the internal pressure rises, the internal terminal plate 21 breaks, the central portion 21B separates from the annular portion 21A, and the valve portion 22A is deformed to convex toward the outer side of the battery. As a result, the current path is cut off. When the internal pressure of the battery rises further, the valve portion 22A breaks, forming a gas discharge port.

[0031] In addition, the structure of the sealing body 19 is not limited to Figure 1 The sealing body 19 may have a laminated structure including two valve bodies, or may have a convex sealing body cover covering the valve body.

[0032] Further reference is made to Figure 2 as well as Figure 3 The thin-walled portion 30 will be described in detail. Figure 2 It is a cross-sectional view in the vertical direction of the sealed battery 10 as an example of the embodiment, and is a diagram showing the thin-walled portion 30 and its vicinity in an enlarged manner. Figure 3 Yes Figure 2 The thin-walled portion 30 is shown in a further enlarged view.

[0033] like Figure 2 as well as Figure 3 As shown, the thin-walled portion 30 is a portion where the groove 33 is formed on the inner surface of the side portion 20B so that the thickness of the side portion 20B becomes smaller than the portion other than the thin-walled portion 30 (hereinafter referred to as the "reference region"), and is an easily deformable portion that is preferentially deformed when a load in the vertical direction acts on the sealed battery 10. Since the groove 33 is formed on the inner surface of the side portion 20B, the side portion 20B deforms to expand toward the outside of the sealed battery 10 starting from the thin-walled portion 30, so that damage to the electrode body 14 caused by deformation of the outer can 20 can be suppressed. In addition, the reference region of the side portion 20B has a substantially constant thickness.

[0034] The lower end 32 of the thin-walled portion 30 is located between the bottom portion 20A and the lower end of the positive electrode 11 in the vertical direction of the outer can 20. The lower end 32 of the thin-walled portion 30 may be located above the inner surface of the bottom portion 20A by a given length (for example, 0.10 mm to 0.50 mm), but in the present embodiment, it is formed at the same height as the inner surface of the bottom portion 20A. In a cross-sectional view in the vertical direction of the outer can 20, the intersection of a virtual line α extending in the vertical direction along the inner surface of the side portion 20B and the inner surface of the reference area of ​​the side portion 20B is the lower end 32 of the thin-walled portion 30. At the lower portion of the side portion 20B, the outer surface of the side portion 20B is formed flush, and the portion of the inner surface of the side portion 20B that is recessed from the virtual line α is the thin-walled portion 30.

[0035] The upper end 31 of the thin-walled portion 30 may be formed to be located above the lower end of the positive electrode 11 in the vertical direction of the outer can 20, but is preferably located between the bottom face portion 20A and the lower end of the positive electrode 11. That is, it is preferred that the entire thin-walled portion 30 is formed at a position that is not opposed to both the positive electrode 11 and the negative electrode 12 in the radial direction of the outer can 20. In the present embodiment, the lower end of the negative electrode 12 is arranged closer to the bottom face portion 20A than the lower end of the positive electrode 11, and the entire thin-walled portion 30 is located between the inner surface of the bottom face portion 20A and the lower end of the negative electrode 12. That is, the entire thin-walled portion 30 is located at a position that is not opposed to both the positive electrode 11 and the negative electrode 12 in the radial direction of the outer can 20.

[0036] The upper end 31 of the thin-walled portion 30 is formed, for example, at a height of 5.0 mm or less from the inner surface of the bottom portion 20A. The length from the upper end 31 to the lower end 32 of the thin-walled portion 30 in the vertical direction is not particularly limited, but an example of a suitable length is 0.10 mm to 1.0 mm. Since the upper end 31 of the thin-walled portion 30 is located between the bottom portion 20A and the lower end of the positive electrode 11, even if a large load acts on the sealed battery 10 in the vertical direction and the thin-walled portion 30 is greatly deformed, the deformed portion will be limited to a portion that does not affect the opposing portions of the positive electrode 11 and the negative electrode 12 in the electrode body 14, and damage to the electrode body 14 can be effectively suppressed.

[0037] The thickness of the thin-walled portion 30 in the radial direction can be adjusted by changing the depth of the groove 33. From the perspective of making the thin-walled portion 30 function as an easily deformable portion, as shown in FIG. Figure 3 As shown, the thickness t of the portion where the thickness of the thin-walled portion 30 becomes the smallest is preferably 80% or less of the thickness of the reference region, and more preferably 40% to 80%. In addition, the thickness of the thin-walled portion 30 refers to the length of the thin-walled portion 30 (side portion 20B) along the radial direction of the outer can 20. An example of the minimum thickness of the thin-walled portion 30 is 0.10 mm to 0.50 mm.

[0038] The inner surface of the thin-walled portion 30 is formed with an inclined surface 34 inclined at a given angle θ relative to the vertical direction of the outer can 20, so that the thickness of the thin-walled portion 30 gradually decreases from the upper end 31 to the lower end 32. Figure 3 As shown, in a cross-sectional view of the outer can 20 in the vertical direction, the inclined surface 34 forming the thin-walled portion 30 is inclined at a given angle θ relative to a virtual line α extending in the vertical direction along the inner surface of the side portion 20B. In a cross-sectional view of the outer can 20 in the vertical direction, the inclined surface 34 is formed as a straight line. By forming the inclined surface 34, the thin-walled portion 30 can be deformed more preferentially when a load in the vertical direction acts. Furthermore, from the perspective of preferential deformation, the inclination angle θ of the inclined surface 34 is preferably 30° to 60°. The length of the inclined surface 34 in the vertical direction is not particularly limited, but an example of a suitable length is 20% to 80% of the length from the upper end 31 to the lower end 32 of the thin-walled portion 30 in the vertical direction.

[0039] A curved surface is formed on the inner surface of the thin-walled portion 30 so that the thickness of the thin-walled portion 30 gradually decreases from the lower end 32 to the upper end 31. An inclined surface may be formed on the lower end 32 side of the inner surface of the thin-walled portion 30 in the same manner as on the upper end 31 side so that the thickness of the thin-walled portion 30 gradually decreases from the lower end 32 to the upper end 31.

[0040] The shape of the groove 33 is not limited to Figure 3 A groove-like shape having an inclined surface 34 as shown, wherein, in a cross-sectional view in the up-down direction of the outer can 20, the inclined surface 34 is inclined at a given angle θ relative to a virtual line α extending in the up-down direction along the inner surface of the side portion 20B, and it is sufficient as long as it is set to be able to function as an easily deformable portion.

[0041] For example, Figure 4 As shown, the groove 43 may also be formed into a circular shape without corners. In addition, a plurality of grooves 33 may also be formed. Further, the thickness along the radial direction of the thin-walled portion 30 at the upper end 31 or the lower end 32 of the thin-walled portion 30 may also be the smallest among the thicknesses along the radial direction of the thin-walled portion 30.

[0042] Example

[0043] Hereinafter, the present disclosure will be described in further detail by way of examples, but the present disclosure is not limited to these examples.

[0044] <Example 1>

[0045] [Production of outer cans]

[0046] After deep drawing of a bottomed cylindrical outer can made of a steel plate material, a groove is formed on the inner surface of the side portion using a rotating roller, and the thin-walled portion is formed into a circular ring shape over the entire circumference of the side portion. The lower end of the thin-walled portion is at the same height as the inner surface of the bottom portion of the outer can. The upper end of the thin-walled portion is lower than the lower end of the negative electrode, and the thin-walled portion is located as a whole between the inner surface of the bottom portion and the lower end of the negative electrode. In addition, since the lower end of the negative electrode is located lower than the lower end of the positive electrode, the upper end of the thin-walled portion is lower than the lower end of the positive electrode. The thickness of the reference area of ​​the side portion is 0.30 mm, and the minimum thickness of the thin-walled portion is 0.24 mm.

[0047] An inclined surface is formed on the inner surface of the thin-walled portion, and the inclined surface is inclined at a given angle θ relative to the vertical direction of the outer can, so that the thickness of the thin-walled portion gradually decreases from the upper end to the lower end side of the thin-walled portion. The inclination angle θ is 30°, and the vertical length of the inclined surface is 0.10 mm. In addition, the vertical length from the upper end to the lower end of the thin-walled portion is 0.20 mm.

[0048] [Production of positive electrode]

[0049] As the positive electrode active material, LiNi 0.8 Co 0.15 Al 0.05 O2. 100 parts by mass of positive electrode active material, 1.7 parts by mass of polyvinylidene fluoride and 2.5 parts by mass of acetylene black were mixed, and N-methyl-2-pyrrolidone was used as a dispersion medium to prepare a positive electrode mixture paste. The positive electrode mixture paste was applied to both sides of a positive electrode core body composed of aluminum foil, and the coating was dried except for the connection part of the positive electrode lead, and then compressed to a given thickness, thereby obtaining a positive electrode. The positive electrode was cut to a given size, and the positive electrode lead was connected to the exposed part of the core body by ultrasonic welding.

[0050] [Production of negative electrode]

[0051] As the negative electrode active material, graphitizable carbon is used. 100 parts by mass of the negative electrode active material, 0.6 parts by mass of polyvinylidene fluoride and 1 part by mass of carboxymethyl cellulose are mixed, and water is used as a dispersion medium to obtain a negative electrode paste. The negative electrode mixture paste is applied to both sides of the negative electrode core composed of copper foil, and the coating is dried except for the connection part of the negative electrode lead, and then compressed to a given thickness, thereby obtaining a negative electrode. The negative electrode is cut to a given size, and the negative electrode lead is connected to the exposed part of the core by ultrasonic welding.

[0052] [Preparation of non-aqueous electrolyte]

[0053] Lithium hexafluorophosphate (LiPF6) was dissolved in a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) to a concentration of 1.0 mol / L to prepare a non-aqueous electrolyte.

[0054] [Battery Assembly]

[0055] The positive electrode and the negative electrode are wound into a spiral shape through a separator made of polyolefin to produce an electrode body. The electrode body is inserted into the above-mentioned outer can via a disc-shaped can bottom insulating plate, and the negative electrode lead connected to the negative electrode is connected to the bottom of the outer can by welding. Next, at a height position of 4 mm from the front end of the opening of the above-mentioned outer can, a groove plastic processing is performed with a rotating roller. After that, the positive electrode lead connected to the positive electrode is connected to the sealing body by welding, and the electrolyte is injected. After that, the sealing body is inserted into the outer can, and the bending process is performed starting from a height position of 2 mm from the front end of the opening of the outer can, and the sealing body is riveted and fixed through the open end of the outer can.

[0056] <Comparative Example 1>

[0057] In the production of the outer can, a battery was produced in the same manner as in Example 1 except that the thin-walled portion was not formed.

[0058] [Evaluation of load test]

[0059] For each battery of the embodiment and the comparative example, a displacement load test was performed using a force sensor to compress the outer can in the vertical direction within a displacement range of 8 mm. In the test, the potential difference between the sealing body as the positive electrode external terminal and the outer can as the negative electrode external terminal was measured, and a short circuit was determined to have occurred when a voltage drop of 0.05 V occurred. The evaluation results are shown in Table 1.

[0060] [Table 1]

[0061]

[0062] As shown in Table 1, the battery of the comparative example had a short circuit, but no short circuit was confirmed in the battery of the example. That is, by forming a thin-walled portion on the side of the outer can, when a load in the vertical direction acts on the outer can, the thin-walled portion formed on the lower side than the opposing portion of the positive electrode and the negative electrode in the electrode body is deformed first, so it is believed that damage to the electrode body can be effectively suppressed.

[0063] -Explanation of Reference Numerals-

[0064] 10 sealed 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; 19 sealing body; 20 outer can; 20A bottom portion; 20B side portion; 20C groove portion; 21 internal terminal plate; 21A annular portion; 21B central portion; 21C vent hole; 22 breaking plate; 22A valve portion; 23 insulating plate; 23A opening portion; 23B vent hole; 24 gasket; 30, 40 thin-walled portion; 31 upper end; 32 lower end; 33, 43 grooves; 34 inclined surface; α virtual line.

Claims

1. A sealed battery having: The electrode body is formed by stacking the positive electrode and the negative electrode with a separator between them; a bottomed cylindrical outer can having a bottom portion and a side portion and accommodating the electrode body; and A sealing body, blocking the opening of the outer can, The outer can has a thin-walled portion, and the thin-walled portion is formed as a depression on the inner surface of the side surface along the circumferential direction. In the height direction of the outer can, the lower end of the thin-walled portion is located between the bottom surface portion of the outer can and the lower end of the positive electrode.

2. The sealed battery according to claim 1, wherein: In the height direction of the outer can, the upper end of the thin-walled portion is located between the bottom surface portion of the outer can and the lower end of the positive electrode.

3. The sealed battery according to claim 1 or 2, wherein: The thin-walled portion has an inclined surface formed so as to gradually decrease in thickness from an upper end toward a lower end side.

4. The sealed battery according to any one of claims 1 to 3, wherein: The thickness of a portion of the thin-walled portion having the smallest thickness is equal to or less than 80% of the thickness of the side surface portion excluding the thin-walled portion.

5. The sealed battery according to any one of claims 1 to 4, wherein The total length of the thin-walled portion in the circumferential direction is equal to or greater than one third of the length of the inner surface of the side surface portion in the circumferential direction.

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