Sealed battery

Abstract

A sealed battery according to one example of an embodiment comprises: an electrode body in which a positive electrode (11) and a negative electrode (12) are laminated with a separator (13) therebetween; a bottomed cylindrical external can (20) which has a bottom surface part (20A) and a side surface part (20B) and which accommodates the electrode body; and a sealing body which closes an opening of the external can (20). The external can (20) has a thin portion (30) that is formed along the circumferential direction such that an inner surface of the side surface part (20B) is recessed. The lower end of the thin portion (30) is positioned between the bottom surface part (20A) and the lower end of the positive electrode (11) in the height direction of the external can (20).

Description

sealed battery

[0001] The present disclosure relates to a sealed battery, and more particularly to a sealed battery provided with a cylindrical outer can with a bottom.

[0002] Conventionally, sealed batteries including a cylindrical outer can with a bottom that houses an electrode assembly have been widely known. Patent Document 1 discloses a sealed battery that uses a cylindrical outer can with a bottom that has a notch formed on the bottom side of the can, so that the outer can breaks at the notch when subjected to a load in the vertical direction. This battery is designed to prevent short circuits between electrodes that may occur when the outer can is compressed in the vertical direction and the electrode assembly is ejected from the outer can. Patent Document 1 describes that short circuits between electrodes can be prevented by ejecting the electrode assembly from the bottom side of the can opposite the sealing body.

[0003] JP 2009-295576 A

[0004] As described above, when the outer can is subjected to a load in the height direction, irregular deformation of the side surface that may damage the electrode assembly may occur. The sealed battery of Patent Document 1 has a notch in the outer can to restrict the ejection direction of the electrode assembly, but there is still room for improvement in suppressing damage to the electrode assembly due to deformation of the outer can.

[0005] In order to solve the above problems, the sealed battery according to the present disclosure comprises an electrode assembly in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween, a cylindrical outer can with a bottom and a side surface and containing the electrode assembly, and a sealing body that closes the opening of the outer can, the outer can having a thin-walled portion formed along the circumferential direction so that the inner surface of the side surface is recessed, and in the height direction of the outer can, the lower end of the thin-walled portion is located between the bottom surface of the outer can and the lower end of the positive electrode.

[0006] According to the sealed battery of the present disclosure, when the outer can is subjected to a load in the height direction, irregular deformation of the side surface of the outer can that may damage the electrode assembly can be suppressed.

[0007] Fig. 1 is a cross-sectional view of a sealed battery according to an embodiment; Fig. 2 is an enlarged cross-sectional view of a thin-walled portion and its vicinity according to an embodiment; Fig. 3 is an enlarged cross-sectional view of a thin-walled portion according to an embodiment; Fig. 4 is an enlarged cross-sectional view of a thin-walled portion and its vicinity according to an embodiment;

[0008] As described above, in a conventional outer can having a side surface of uniform thickness, when a load is applied in the height direction, the outer can is likely to buckle, causing irregular deformation of the side surface, and this deformation may damage the electrode assembly. As a result of careful consideration to suppress damage to the electrode assembly caused by deformation of the outer can, the inventors have found that damage to the electrode assembly caused by deformation of the outer can can be suppressed by forming a thin-walled portion along the circumferential direction in a portion of the side surface of the outer can that does not face either the positive electrode or the negative electrode, so that the inner surface of the side surface is recessed.

[0009] In this case, when the sealed battery is subjected to a load in the height direction, the thin-walled portion deforms preferentially, thereby suppressing irregular deformation of the side surface. That is, the side surface of the outer can can be deformed preferentially in the portion that does not face either the positive electrode or the negative electrode. Furthermore, by forming the thin-walled portion so that the inner surface of the side surface is recessed, the outer can deforms by bulging outward from the thin-walled portion toward the outside of the sealed battery, thereby more reliably suppressing damage to the electrode assembly due to deformation of the outer can.

[0010] An example of an embodiment of the present disclosure will be described in detail below. Hereinafter, as an example of an embodiment of a sealed battery according to the present disclosure, a cylindrical battery in which a wound electrode assembly 14 is housed in a cylindrical outer can 20 with a bottom will be exemplified. However, the battery may also be a prismatic battery equipped with a cylindrical outer can with a bottom. The electrode assembly may also be a laminated type in which multiple positive electrodes and multiple negative electrodes are alternately stacked with separators interposed therebetween. For convenience of explanation, in this specification, the direction along the axial direction of the outer can 20 will be referred to as the "vertical direction," the side of the sealing body 19 of the outer can 20 will be referred to as the "upper," and the side of the bottom portion 20A of the outer can 20 will be referred to as the "lower."

[0011] Fig. 1 is a vertical cross-sectional view of a sealed battery 10 according to an embodiment. As shown in Fig. 1, the sealed battery 10 includes an electrode assembly 14, an electrolyte, a cylindrical outer can 20 with a bottom that accommodates the electrode assembly 14 and the electrolyte, and a sealing body 19 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 interposed between the positive electrode 11 and the negative electrode 12, and has a wound structure in which the positive electrode 11 and the negative electrode 12 are wound with the separator 13 interposed therebetween. The outer can 20 is a cylindrical container with a bottom, and has a bottom portion 20A and a side portion 20B.

[0012] As will be described in detail later, the exterior can 20 has a thin-walled portion 30 where the thickness of the side surface portion 20B is locally reduced. The thin-walled portion 30 is formed along the circumferential direction so that the inner surface of the side surface portion 20B is recessed, and is an easily deformable portion that deforms preferentially when a load acts on the sealed battery 10 in the vertical direction.

[0013] The electrolyte may be either an aqueous electrolyte or a non-aqueous electrolyte. One example of a suitable sealed battery 10 is a non-aqueous electrolyte secondary battery, such as a lithium ion battery, that uses a non-aqueous electrolyte. The non-aqueous electrolyte includes, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and mixed solvents 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, and may be a solid electrolyte using a gel-like polymer or the like. The electrolyte salt may be LiPF ６ Lithium salts such as

[0014] The electrode assembly 14 has a long positive electrode 11, a long negative electrode 12, and two long separators 13. The electrode assembly 14 also has, as electrode leads, a positive electrode lead 17 joined to the positive electrode 11 and a negative electrode lead 18 joined to the negative electrode 12. The negative electrode 12 is formed to have dimensions slightly larger than the positive electrode 11 in order to suppress lithium deposition. Therefore, the lower end of the negative electrode 12 is disposed 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 have dimensions at least slightly larger than the positive electrode 11 and are disposed, for example, so as to sandwich the positive electrode 11 therebetween.

[0015] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer provided on both sides of the positive electrode core. The positive electrode core can be 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 material, such as acetylene black, and a binder, such as polyvinylidene fluoride (PVdF). The positive electrode 11 can be produced by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive material, and a binder to the positive electrode core, drying the coating, and then compressing it to form a positive electrode mixture layer on both sides of the positive electrode core.

[0016] For example, a lithium transition metal composite oxide is used as the positive electrode active material. Examples of metal elements contained in the lithium transition metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. 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. Specific examples include a composite oxide containing Ni, Co, and Mn, and a composite oxide containing Ni, Co, and Al.

[0017] The negative electrode 12 has a negative electrode core and a negative electrode mixture layer provided on both sides of the negative electrode 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 layer. The negative electrode mixture layer contains a negative electrode active material and a binder such as styrene butadiene rubber (SBR). The negative electrode 12 can be produced by applying a negative electrode mixture slurry containing the negative electrode active material and the binder to the negative electrode core, drying the coating, and then compressing it to form a negative electrode mixture layer on both sides of the negative electrode core.

[0018] The negative electrode active material may be, for example, natural graphite such as flake graphite, lump graphite, or amorphous graphite, or artificial graphite such as lump artificial graphite or graphitized mesophase carbon microbeads. The negative electrode active material may be a metal that alloys with lithium, such as Si or Sn, an alloy containing such a metal, or a compound containing such a metal, which may be used in combination with graphite. A suitable example of the active material is SiO ２The Si-containing material is a Si-containing material in which fine Si particles are dispersed in a silicate phase such as lithium silicate or an amorphous carbon phase.

[0019] Insulating plates 15 and 16 are disposed above and below the electrode body 14. In the example shown in Fig. 1 , a positive electrode lead 17 attached to the positive electrode 11 passes through a through-hole in the insulating plate 15 and extends toward the sealing body 19, and a negative electrode lead 18 attached to the negative electrode 12 passes outside the insulating plate 16 and extends toward the bottom portion 20A of the outer can 20. The positive electrode lead 17 is connected by welding or the like to the inner surface of the sealing body 19 facing inward of the outer can 20, and the sealing body 19 serves as a positive electrode external terminal. The negative electrode lead 18 is connected by welding or the like to the inner surface of the bottom portion 20A of the outer can 20, and the outer can 20 serves as a negative electrode external terminal.

[0020] The outer can 20 is a cylindrical metal container 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 sealing of the battery interior and insulation between the outer can 20 and the sealing body 19. The outer can 20 has a grooved portion 20C formed by a part of the side surface 20B protruding inward to support the sealing body 19. The grooved portion 20C is preferably formed in an annular shape along the circumferential direction of the outer can 20, and supports the sealing body 19 on its top surface. The sealing body 19 is fixed to the top of the outer can 20 by the grooved portion 20C and the open end of the outer can 20, which is crimped to the sealing body 19.

[0021] As described above, the exterior can 20 has a thin-walled portion 30 formed along the circumferential direction so as to recess the inner surface of the side surface portion 20B. As will be described in detail later, the thin-walled portion 30 is formed at the lower end of the side surface portion 20B in a portion that does not face either the positive electrode 11 or the negative electrode 12 in the radial direction of the exterior can 20. The thin-walled portion 30 may be formed in a portion of the side surface portion 20B in the circumferential direction of the side surface portion 20B. However, the total circumferential length of the thin-walled portion 30 is preferably at least one-third, and more preferably at least one-half, of the circumferential length (perimeter) of the inner surface of the side surface portion 20B. In this case, when a load is applied in the vertical direction to the exterior can 20, the thin-walled portion 30 deforms preferentially, making it easier to suppress irregular deformation of the side surface portion 20B. The circumferential length of the thin-walled portion 30 can be measured based on the upper end of the thin-walled portion 30 on the inner surface of the side surface portion 20B.

[0022] When the length of the thin-walled portions 30 along the circumferential direction of the inner surface of the side surface portion 20B is shorter than the circumferential length of the side surface portion 20B, it is preferable to form the thin-walled portions 30 at multiple positions so that they are evenly distributed throughout the entire circumferential direction of the inner surface of the side surface portion 20B, rather than being concentrated in a certain portion of the circumferential direction. The thin-walled portions 30 may be formed, for example, at substantially equal intervals along the circumferential direction of the inner surface of the side surface portion 20B. In this embodiment, the thin-walled portions 30 are formed along the entire periphery of the inner surface of the side surface portion 20B. That is, the thin-walled portions 30 are formed in an annular shape along the circumferential direction of the inner surface of the side surface portion 20B. In this case, the effect of suppressing the irregular deformation is more pronounced.

[0023] The sealing body 19 is a disk-shaped member equipped with a current interruption mechanism. The sealing body 19 has a structure in which, in order from the electrode body 14 side, an internal terminal plate 21, an insulating plate 23, and a rupture plate 22 are stacked. The internal terminal plate 21 is a metal plate including a thick annular portion 21A to which the positive electrode lead 17 is connected and a thin central portion 21B that is separated from the annular portion 21A when the internal pressure of the battery exceeds a predetermined threshold. A vent hole 21C is formed in the annular portion 21A.

[0024] The rupture plate 22 is disposed opposite the internal terminal plate 21 with the insulating plate 23 sandwiched therebetween. An opening 23A is formed in the radial center of the insulating plate 23, and an air vent 23B is formed in a portion overlapping with the air vent 21C of the internal terminal plate 21. The rupture plate 22 has a valve portion 22A that ruptures when the internal pressure of the battery exceeds a predetermined threshold, and the valve portion 22A is connected to the central portion 21B of the internal terminal plate 21 via the opening 23A of the insulating plate 23 by welding or the like. The insulating plate 23 insulates portions other than the connection portion between the annular portion 21A and the central portion 21B of the valve portion.

[0025] The valve portion 22A includes a lower protrusion that protrudes toward the inside of the battery and a thin-walled portion formed around the lower protrusion, and is formed in the radial center of the rupture plate 22. In the sealed battery 10, the internal terminal plate 21, to which the positive electrode lead 17 is connected, is electrically connected to the rupture plate 22, thereby forming a current path connecting the electrode body 14 to the rupture plate 22. When an abnormality occurs in the battery and the internal pressure increases, the internal terminal plate 21 breaks, the central portion 21B is separated from the annular portion 21A, and the valve portion 22A deforms so that it protrudes toward the outside of the battery. This interrupts the current path. When the internal pressure of the battery further increases, the valve portion 22A breaks, forming a gas outlet.

[0026] The structure of sealing body 19 is not limited to the structure shown in Fig. 1. Sealing body 19 may have a laminated structure including two valve bodies, or may have a convex sealing body cap that covers the valve bodies.

[0027] The thin-walled portion 30 will be described in detail below with further reference to Figures 2 and 3. Figure 2 is a vertical cross-sectional view of the sealed battery 10 according to an embodiment, showing an enlarged view of the thin-walled portion 30 and its vicinity. Figure 3 is a further enlarged view of the thin-walled portion 30 shown in Figure 2.

[0028] 2 and 3 , the thin-walled portion 30 is a portion where the thickness of the side surface portion 20B is smaller than the portion other than the thin-walled portion 30 (hereinafter referred to as the "reference region") by forming a groove 33 on the inner surface of the side surface portion 20B, and is an easily deformable portion that deforms preferentially when a load in the vertical direction acts on the sealed battery 10. By forming the groove 33 on the inner surface of the side surface portion 20B, the side surface portion 20B deforms so as to bulge from the thin-walled portion 30 toward the outside of the sealed battery 10, thereby suppressing damage to the electrode body 14 due to deformation of the outer can 20. Note that the reference region of the side surface portion 20B has a substantially constant thickness.

[0029] The lower end 32 of the thin-walled portion 30 is located between the bottom surface portion 20A and the lower end of the positive electrode 11 in the up-down direction of the exterior can 20. The lower end 32 of the thin-walled portion 30 may be located a predetermined distance above the inner surface of the bottom surface portion 20A (e.g., 0.10 mm to 0.50 mm above), but in this embodiment, it is formed at the same height as the inner surface of the bottom surface portion 20A. In a cross-sectional view of the exterior can 20 in the up-down direction, the intersection of an imaginary line α extending in the up-down direction along the inner surface of the side surface portion 20B and the inner surface of a reference region of the side surface portion 20B is the lower end 32 of the thin-walled portion 30. At the lower part of the side surface portion 20B, the outer surface of the side surface portion 20B is formed flush, and the portion of the inner surface of the side surface portion 20B recessed from the imaginary line α forms the thin-walled portion 30.

[0030] The upper end 31 of the thin-walled portion 30 may be formed so as to be located above the lower end of the positive electrode 11 in the up-down direction of the exterior can 20, but is preferably located between the bottom surface portion 20A and the lower end of the positive electrode 11. In other words, the entire thin-walled portion 30 is preferably formed in a position that does not face either the positive electrode 11 or the negative electrode 12 in the radial direction of the exterior can 20. In this embodiment, the lower end of the negative electrode 12 is disposed closer to the bottom surface 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 surface portion 20A and the lower end of the negative electrode 12. In other words, the entire thin-walled portion 30 is located so as not to face either the positive electrode 11 or the negative electrode 12 in the radial direction of the exterior can 20.

[0031] 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 surface portion 20A. The vertical length from the upper end 31 to the lower end 32 of the thin-walled portion 30 is not particularly limited, but an example of a suitable length is 0.10 mm to 1.0 mm. By positioning the upper end 31 of the thin-walled portion 30 between the bottom surface portion 20A and the lower end of the positive electrode 11, even if a large load acts in the vertical direction of the sealed battery 10 and the thin-walled portion 30 is significantly deformed, the deformation location is limited to a portion of the electrode body 14 that does not affect the opposing portion of the positive electrode 11 and the negative electrode 12, and damage to the electrode body 14 can be effectively suppressed.

[0032] The radial thickness of the thin-walled portion 30 can be adjusted by changing the depth of the groove 33. From the viewpoint of making the thin-walled portion 30 function as an easily deformable portion, as shown in FIG. 3 , the thickness t of the thin-walled portion 30 at its smallest point is preferably 80% or less of the thickness of the reference region, and more preferably 40% to 80%. The thickness of the thin-walled portion 30 refers to the length of the thin-walled portion 30 (side surface 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.

[0033] The inner surface of the thin-walled portion 30 is formed with an inclined surface 34 inclined at a predetermined angle θ with respect 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 toward the lower end 32. As shown in FIG. 3 , in a vertical cross-sectional view of the outer can 20, the inclined surface 34 forming the thin-walled portion 30 is inclined at a predetermined angle θ with respect to an imaginary line α extending in the vertical direction along the inner surface of the side portion 20B. The inclined surface 34 is formed so as to be linear in the vertical cross-sectional view of the outer can 20. By forming the inclined surface 34, the thin-walled portion 30 can be deformed more preferentially when a load is applied in the vertical direction. From the viewpoint of further preferential deformation, the inclination angle θ of the inclined surface 34 is preferably 30° to 60°. The vertical length of the inclined surface 34 is not particularly limited, but a preferred example is 20% to 80% of the vertical length of the thin-walled portion 30 from the upper end 31 to the lower end 32.

[0034] 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 toward the upper end 31. Similar to the upper end 31 side, an inclined surface may be formed on the lower end 32 side of 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 toward the upper end 31.

[0035] The shape of the groove 33 is not limited to a groove-like shape having an inclined surface 34 inclined at a predetermined angle θ with respect to an imaginary line α extending in the vertical direction along the inner surface of the side portion 20B in a vertical cross-sectional view of the outer can 20 as shown in FIG. 3 , and may be set so as to function as an easily deformable portion.

[0036] For example, as shown in Fig. 4, the groove 43 may be formed in a circular shape without corners. Also, a plurality of grooves 33 may be formed. Furthermore, the thickness of the thin-walled portion 30 along the radial direction at the upper end 31 or the lower end 32 of the thin-walled portion 30 may be the smallest among the thicknesses of the thin-walled portion 30 along the radial direction.

[0037] The present disclosure will be explained in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0038] Example 1 [Fabrication of Outer Can] After drawing to fabricate a bottomed cylindrical outer can made of steel sheet material, a rotating roller was used to form a groove on the inner surface of the side wall, forming a circular thin-walled portion around the entire circumference of the side wall. The lower end of the thin-walled portion was at the same height as the inner surface of the bottom wall of the outer can. The upper end of the thin-walled portion was located below the lower end of the negative electrode, and the entire thin-walled portion was located between the inner surface of the bottom wall and the lower end of the negative electrode. Note that since the lower end of the negative electrode was located below the lower end of the positive electrode, the upper end of the thin-walled portion was located below the lower end of the positive electrode. The thickness of the reference region of the side wall was 0.30 mm, and the minimum thickness of the thin-walled portion was 0.24 mm.

[0039] An inclined surface was formed on the inner surface of the thin-walled portion at a predetermined angle θ relative to the vertical direction of the outer can so that the thickness of the thin-walled portion gradually decreased from the upper end to the lower end of the thin-walled portion. The inclination angle θ was 30°, and the vertical length of the inclined surface was 0.10 mm. The vertical length from the upper end to the lower end of the thin-walled portion was 0.20 mm.

[0040] [Preparation of Positive Electrode] LiNi was used as the positive electrode active material. ０．８ Co ０．１５ Al ０．０５ O ２ A positive electrode mixture paste was prepared by mixing 100 parts by mass of the positive electrode active material, 1.7 parts by mass of polyvinylidene fluoride, and 2.5 parts by mass of acetylene black, and using N-methyl-2-pyrrolidone as a dispersion medium. The positive electrode mixture paste was applied to both sides of a positive electrode core made of aluminum foil, excluding the connection portion of the positive electrode lead, and the coating was dried. Thereafter, the positive electrode was compressed to a predetermined thickness to obtain a positive electrode. This positive electrode was cut to a predetermined size, and a positive electrode lead was connected to the exposed portion of the core by ultrasonic welding.

[0041] [Negative Electrode Fabrication] Graphitizable carbon was used as the negative electrode active material. 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 were mixed, and a negative electrode paste was obtained using water as a dispersion medium. The negative electrode mixture paste was applied to both sides of a negative electrode core made of copper foil, excluding the connection portion of the negative electrode lead, and the coating was dried. The negative electrode was then compressed to a predetermined thickness to obtain a negative electrode. The negative electrode was cut to a predetermined size, and a negative electrode lead was connected to the exposed portion of the core by ultrasonic welding.

[0042] [Preparation of non-aqueous electrolyte] Lithium hexafluorophosphate (LiPF ) was dissolved in a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). ６ ) was dissolved in the solution to a concentration of 1.0 mol / L to prepare a non-aqueous electrolyte solution.

[0043] [Battery Assembly] The positive electrode and negative electrode were spirally wound with a polyolefin separator between them to produce an electrode assembly. This electrode assembly was inserted into the outer can via a disc-shaped can bottom insulating plate, and the negative electrode lead connected to the negative electrode was connected to the bottom of the outer can by welding. Next, groove forming plastic processing was performed with a rotating roller at a height of 4 mm from the tip of the opening of the outer can. Thereafter, the positive electrode lead connected to the positive electrode and the sealing body were connected by welding, and an electrolyte was injected. Thereafter, the sealing body was inserted into the outer can and bent starting at a height of 2 mm from the tip of the opening of the outer can, and the sealing body was crimped and fixed to the open end of the outer can.

[0044] Comparative Example 1 A battery was fabricated in the same manner as in Example 1, except that no thin-walled portion was formed in the fabrication of the outer can.

[0045] [Load Test Evaluation] For each battery of the Examples and Comparative Examples, a displacement load test was performed in which the outer can was compressed vertically using a load cell up to a displacement of 8 mm. During the test, the potential difference between the sealing body (positive electrode external terminal) and the outer can (negative electrode external terminal) was measured, and a voltage drop of 0.05 V was determined to indicate a short circuit. The evaluation results are shown in Table 1.

[0046]

[0047] As shown in Table 1, a short circuit occurred in the battery of the comparative example, whereas no short circuit was observed in the battery of the example. In other words, it is believed that by forming a thin portion on the side surface of the outer can, when a load is applied to the outer can in the vertical direction, the thin portion formed below the opposing portion of the positive and negative electrodes in the electrode assembly deforms preferentially, thereby effectively suppressing damage to the electrode assembly.

[0048] REFERENCE SIGNS LIST 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 grooved portion, 21 internal terminal plate, 21A annular portion, 21B central portion, 21C vent hole, 22 rupture plate, 22A valve portion, 23 insulating plate, 23A opening, 23B vent hole, 24 gasket, 30, 40 thin portion, 31 upper end, 32 lower end, 33, 43 groove, 34 inclined surface, α imaginary line

Claims

1. an electrode assembly in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween; a cylindrical exterior can having a bottom and a side surface and configured to accommodate the electrode assembly; a sealing body that closes an opening of the outer can; Equipped with the exterior can has a thin-walled portion formed along a circumferential direction so as to be recessed on an inner surface of the side surface, a lower end of the thin portion is located between the bottom portion of the outer can and a lower end of the positive electrode in a height direction of the outer can.

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

3. 3. The sealed battery according to claim 1, wherein the thin portion has a slope formed so that the thickness gradually decreases from the upper end to the lower end.

4. 3. The sealed battery according to claim 1, wherein the thickness of the thin portion at the thinnest point is 80% or less of the thickness of the side surface portion excluding the thin portion.

5. 3. The sealed battery according to claim 1, wherein the total circumferential length of the thin-walled portions is equal to or greater than one-third of the circumferential length of the inner surface of the side portion.