JP2001126682A - Sealed battery and method of fabricating it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealed battery that secures improved electrical and mechanical connection between the top cover and safety valve, improving the changes resulting from mechanical causes such as vibration and impact, heat history, or repetition of the charging and discharging cycle. SOLUTION: A sealed battery includes an outer can with an opening end for mounting a battery body 2, top cover 30 and safety valve 6 arranged in the opening end, and contact part for contacting the top cover 30 with the safety valve 6. The top cover 30 comprises at least a first metal layer 31, and a second metal layer 32 composed of Al or Al alloy serving as the clad metal. In any case, the portion of the top cover contacting the safety valve must be composed of the second metal layer 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed battery suitable for use in a non-aqueous electrolyte secondary battery and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, demand for batteries having high energy density and high output density has been rapidly increasing with the development of portable devices and electric vehicles such as electric vehicles. Above all,
Non-aqueous electrolyte secondary batteries using a lithium-containing compound as the positive electrode and a material capable of doping and undoping lithium as the negative electrode are widely used because of their high voltage, light weight and high energy density. Has been reached.

On the other hand, as the above-described devices have been improved in performance and the range of use has been expanded, the power consumption has been increased, and there has been a strong demand for the development of a battery having a small internal resistance and capable of stably obtaining a high output. Further, in the case where the battery is used for a portable device or an electric vehicle, the battery is particularly susceptible to vibration and impact, and furthermore, a large temperature change.

A sealed battery such as a non-aqueous electrolyte secondary battery is
As shown in a schematic cross-sectional view of one example in FIG. 5, a battery main body 2 is housed in a cylindrical bottomed outer can 1, and a non-aqueous electrolyte is injected into the outer can 1 and impregnated in the battery main body 2. Consisting of

As shown in the open perspective view of FIG. 2, the battery body 2 is formed by laminating a film-like positive electrode 21 and a negative electrode 22 via a film-like separator 23, respectively. However, for example, the center hole 2
It is wound around a cylindrical tubular core 24 having a length of 4 h. At both ends of the battery body 2 housed in the outer can 1,
Insulating sheets 3 and 4 are arranged. At the open end of the outer can 1, a top cover 5 made of a metal plate having excellent conductivity and a safety valve 6 are arranged and sealed.
The safety valve 6 is connected to a lead 7 on the positive electrode side derived from the battery body 2 via, for example, a conductive sub-disk 8. The top cover 5 is formed of a metal plate, and the outer peripheral flange 5f is in contact with the outer peripheral flange 6f of the safety valve 6 to be electrically connected to the safety valve 6 and electrically connected to the lead 7. Thus, it serves as an external lead-out terminal and mechanically protects the safety valve 6.

[0006] The top cover 5 and the safety valve 6 in the above-described conventional sealed type battery are provided with flanges 5f and 6f on the outer periphery thereof.
With the gasket 9
And is held by being caulked on the open end side of the outer can 1 through the opening.

[0007]

However, in the case where the top cover 5 and the safety valve 6 are overlapped with each other for electrical connection as described above, the mechanical force such as the above-described vibration or impact is applied, Due to changes over time due to thermal history or repeated charge / discharge cycles, the contact pressure between the two decreases, or a film is formed on the contact surface, resulting in a change in the contact resistance of this part, resulting in the battery The internal resistance increases and the output decreases.

In order to avoid such inconvenience, it is desirable that the electrical connection between the top cover 5 and the safety valve 6 be joined by metal such as welding. However, in practice, such joining was also difficult. This is for the following reason. That is, in a non-aqueous electrolyte secondary battery,
The safety valve is connected to the positive electrode of the battery, and
Since it is arranged in a portion that comes into contact with the electrolytic solution, it is composed of electrochemically stable Al. On the other hand, the top cover has excellent mechanical strength to mechanically protect the safety valve,
In addition, it is excellent in connectivity with an external load connected to this non-aqueous electrolyte secondary battery or an external terminal of another battery or the like, that is, made of a metal having excellent weldability to Cu, Ni, or the like. Required. Such a top cover is generally made of a metal material such as SUS (stainless steel), Fe, and Ni.

Therefore, for example, welding of the safety valve and the top cover means welding of Al to SUS, Fe or Ni.
Since they are softer than materials such as S, Fe, and Ni, and have a large difference in melting point, boiling point, and the like, it is difficult to alloy them.
Welding between them is extremely difficult. Also, in the case of joining by pressure contact, when the contact area is small, such as the surrounding flange, as in the case of the above-described battery component, it is difficult to make good pressure contact between Al and a dissimilar metal.

[0010] The present invention enables good electrical and mechanical joining between the above-described top cover and safety valve in a sealed battery, and is used in a battery of a portable device, an electric moving body, or the like. Another object of the present invention is to provide a sealed battery capable of effectively improving a mechanical force such as vibration and impact, a thermal history, and a change with time due to repetition of a charge / discharge cycle, and a method of manufacturing the same.

[0011]

In a sealed battery according to the present invention, a top cover and a safety valve are arranged at an open end of an outer can in which a battery body is housed, and the top cover and the safety valve come into contact with each other. A sealed battery having a contact portion,
The top cover is formed of at least a first metal layer and a clad material of a second metal layer made of a metal containing Al or an Al alloy, and at least a surface of the top cover serving as the contact portion is formed of the second metal layer. I do.

According to the configuration of the present invention, the top cover is formed with a metal clad layer containing Al or an Al alloy, and is brought into contact with the safety valve on the surface having the metal containing Al or the Al alloy. , And both can be favorably contacted.

Further, in the method for manufacturing a sealed battery according to the present invention, the contact portion of the top cover with the safety valve, that is, the connection portion is formed by a clad layer of a metal containing Al or an Al alloy, and the top cover and the safety valve are connected to each other. Is performed by ultrasonic welding, resistance welding, laser welding, friction welding, and cold welding. As described above, in the manufacturing method of the present invention, the contact portion of the top cover with the safety valve is set to A
By using a metal containing l or Al alloy, the electric connection between the two can be performed well by ultrasonic welding, resistance welding, laser welding, friction welding, and cold welding.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, a case where the present invention is applied to a non-aqueous electrolyte secondary battery of a sealed battery will be described. FIG. 1 is a schematic cross-sectional view of a main part of an example of this embodiment. In this sealed nonaqueous electrolyte secondary battery, for example, a battery main body 2 is housed in a cylindrical bottomed outer can 1, and the outer can 1
A non-aqueous electrolytic solution is injected into the inside and impregnated in the battery body 2.

As shown in an open perspective view of FIG. 2, the battery body 2 is formed by laminating a film-like positive electrode 21 and a negative electrode 22 via a film-like separator 23, respectively. Is wound around, for example, a cylindrical tubular core 24 made of, for example, polypropylene having a center hole 24h.

The positive electrode 21 and the negative electrode 22 are shown in FIG.
As shown in the schematic plan views of A and B, the positive electrode 21 is formed by applying a positive electrode active material 21m to both surfaces of a strip-shaped film electrode 21s made of, for example, Al foil,
The negative electrode 22 is formed by applying a negative electrode active material 22m to both surfaces of a strip-shaped film electrode sheet 22s made of, for example, Cu foil.

The positive electrode active material 21m is made of, for example, a material capable of undoping and re-doping Li, for example, an active material Li _x MO _{2 made} of a lithium transition metal oxide (M is Co, Ni, Mn).
And at least one transition metal represented by the following formula: 0.4 ≦ x ≦ 1.1).

The anode active material 22m is made of a material that can be doped and dedoped with Li, for example, a carbon material, for example, graphite,
Graphitizable carbon, hardly graphitizable carbon and the like can be used.

For example, regions where the active materials 21m and 22m are not applied are provided at, for example, one end of each of the film-like electrodes 21s and 22s of the positive electrode 21 and the negative electrode 22. One end of each of the lead 7 and the strip-shaped lead 27 made of Ni foil is joined, and each free end is led out from one side edge of each of the electrodes 21 and 22.

The separator 23 is made of, for example, polyethylene,
It can be constituted by a microporous membrane of polypropylene or Teflon (registered trademark).

The non-aqueous electrolyte comprises an organic solvent and an electrolyte dissolved therein. Alternatively, a so-called polymer electrolyte in which a non-aqueous electrolyte is mixed with a polymer compound can be used. The organic solvent is, for example, ethylene carbonate,
Cyclic carbonates such as propylene carbonate, dimer carbonate, chain carbonates such as diethyl carbonate, cyclic esters such as γ-butyrolactone and γ-parerolactone, chain esters such as ethyl acetate and methyl propionate, tetrahydrofuran, and 1,2-dimethoxy One or more kinds of ethers such as ethane can be used.
Examples of the electrolyte include lithium salts which dissolve in a solvent to be used and exhibit ionic conductivity, such as LiPF ₆ , LiBF ₄ , and Li
ClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ )
₂ , one or more of LiC (CF ₃ SO ₂ ) _{3 and the} like can be used.

The lead 27 of the battery body 2 housed in the outer can 1 is electrically connected to the outer can 1, for example, at the bottom. In the outer can 1, for example, insulating thin plates 3 and 4 are arranged at both ends of the battery main body 2 with the battery main body 2 interposed therebetween.

Further, a top cover 30 having a special configuration and a safety valve 6 are arranged at the open end of the outer can 1 and are substantially sealed by the safety valve 6. Top cover 5
As shown in a plan view of FIG. 4, for example, a bulging portion 3f having a flange portion 30f at a peripheral portion thereof and bulging outward at a central portion.
It has a shape of “0” and is squeezed out, for example, substantially into a dish shape as a whole. Then, a vent hole 30h is formed in a part thereof.

The safety valve 6 is, as usual, made of, for example, Al or an Al alloy, has a flange 6f on its outer periphery, bulges into the outer can 1, and has the center of the battery body 2 in the center. Projection 6p projecting toward the center
Is formed, for example, in a shape substantially squeezed into a dish shape.

The top cover 30 and the safety valve 6 are
In a state where these flange portions 30f and 6f are overlapped, they are crimped and held on the open end of the outer can 1 via the ring-shaped gasket 9.

On the battery body 2 side of the safety valve 6, a stripper disk 34 made of, for example, a metal plate and having a center hole penetrating the protrusion 6p of the safety valve 6 is provided via a ring insulator 33, for example. Is fixed.

The tip of the protruding portion 6p of the safety valve 6 protruding toward the battery body 2 through the center hole of the stripper disk 34 is welded to the free end of the lead 7 led out from the positive electrode 21 of the battery body 2. A sub disk 8 made of a conductive metal plate, for example, Al is welded.

In the present invention, the top cover 30 is formed of a clad material formed by laminating at least a first metal layer 31 and a second metal layer 32, for example, by cold pressing. The first metal layer 31 is made of, for example, SUS
(Stainless steel), made of a metal material having high mechanical strength and conductivity by Fe and Ni. The second metal layer 32 is made of a metal containing Al or an Al alloy. As this Al alloy, Al and various metals such as Si, Fe, Cu, Mn, Mg, Cr, Zn, Zr, T
alloys with one or more of i, Ga, V, Ti
Alloy No. 1085, 1080, 1070, 1 in S
050, 1100, 1200, 1N00, 1N30, 2
014, 2017, 2219, 2024, 3003, 3
203,3004,3104,3005,3105,5
055,5052,5652,5154,5254,5
454, 5082, 5182, 5083, 5086, 5
N01, 6061, 7075, and 7N01 can be used.

As described above, in the production of the above-mentioned sealed non-aqueous electrolyte secondary battery, the positive electrode 21 and the negative electrode 22 are laminated with the separator 23 interposed therebetween. For example, the battery main body 2 is formed by being wound around the periphery, for example, leading the lead 7 on the positive electrode side from the center portion thereof and leading the lead 27 on the negative electrode side from the outer peripheral portion side.

On the other hand, for example, an outer can 1 made of a bottomed cylindrical body made of Fe and Ni-plated on its surface is prepared,
The battery main body 2 is inserted into the outer can 1 so that the lead-out side of the lead 27 on the negative electrode side is positioned on the bottom side of the outer can 1 with the insulating thin plates 3 and 4 disposed at both ends in the axial direction. Then, the lead 27 is connected to the bottom surface of the outer can 1 by, for example, resistance welding.

Then, a so-called beading process is performed on the open end side of the outer can 1 so as to form, for example, a ring-shaped constricted portion that protrudes toward the axial center, thereby fixing the battery main body 2 in the outer can 1. .

Then, a gasket 9 made of, for example, polypropylene for sealing is inserted into the open end side of the outer can 1. The lead 7 on the positive electrode side of the battery body 2 penetrates through a through hole 33 formed in the insulating thin plate 3, and its free end is formed, for example, in a protruding portion 6 p previously exposed to the battery body 2 through the through hole of the stripper disk 34. Al attached by ultrasonic welding
Laser welding is performed on the sub disk 8.

Then, a non-aqueous electrolyte is injected into the outer can 1, and thereafter, the gasket 9, the flange 30f of the top cover 30, and the flange 6f of the safety valve 6 are laminated and adhered to each other. 1 was fixed by caulking the open end, the outer can 1 was sealed by the safety valve 6, and a top cover 30 was placed outside the outer can 1 to cover the outer can 1 to provide mechanical protection and lead out the positive electrode terminal to the outside. A sealed non-aqueous electrolyte secondary battery is constructed.

In the laminated portion of the flange 30f of the top cover 30 and the flange 6f of the safety valve 6, that is, in the contact portion,
The second metal layer 32 made of Al or an Al alloy of the top cover 30 is overlapped so as to be in contact with the safety valve 6 made of Al. In this way, these contact portions are brought into good contact. .

The flange 3 of the top cover 30
As shown in FIG. 4, a plurality of (three in the figure) joint portions 35 by ultrasonic welding can be provided at a laminated portion, that is, a contact portion of the safety valve 6 with the flange portion 6 f of the safety valve 6. The joint 35 can be formed in a ring shape over the entire circumference of the flange.

Alternatively, the joining portion 35 of the contact portion between the top cover 30 and the safety valve 6 is a joining portion formed by resistance welding. Alternatively, the joint 35 of the contact portion between the top cover 30 and the safety valve 6 is a joint by laser welding. Or, the joint 3 between the above-described top cover 30 and the safety valve 6
The joining of No. 5 is performed by friction welding. Alternatively, the joining of the joining portion 35 between the top cover 30 and the safety valve 6 is performed by cold pressing. Regardless of the close contact or the joining, the contact portion between the top cover 30 and the safety valve 6 is made of the same material, so that the contact is excellently and firmly joined.

The sealed type non-aqueous electrolyte secondary battery having this configuration has a configuration sealed by a safety valve 6, and for some reason, an abnormal internal pressure rise due to generation of gas or the like in the housing portion of the battery body 2 Occurs, safety valve 6
Is designed to bulge outward as shown by a chain line in FIG. 1 and, accordingly, to cut off a welded portion between the projection 6p and the sub-disk. Thus, the electrical connection between the external terminal, that is, the top cover 30 and the lead 7 is cut off. When the internal pressure further rises, the safety valve 6 is partially broken, and the gas inside the air passage 30 of the top cover 30 is released.
It is configured such that the internal pressure is not released to the outside through h and the internal pressure does not rise above a certain level.

Next, an embodiment of the sealed battery according to the present invention will be described, but the present invention is not limited to this example. [Embodiment 1] This embodiment is an embodiment of the sealed nonaqueous electrolyte secondary battery shown in FIG. A slurry of a positive electrode active material having the following composition and constituting the positive electrode 21 was prepared. Positive electrode active material: LiMn ₂ O ₄ powder (average particle size: 20 μm) 90 parts by weight Conductive agent: graphite powder 6 parts by weight Binder: vinylidene fluoride resin 4 parts by weight These are dispersed in N-methylpyrrolidone to form a slurry. Obtained. This slurry was applied to both surfaces of a current collector made of Al having a thickness of 20 μm, that is, a film-like electrode 21s, and the both surfaces were roll-pressed to produce a positive electrode raw material having a total thickness of 210 μm. This material was cut into a width of 50.5 mm and a length of 500 mm.
1 was produced. Then, an Al lead 7 having a thickness of 0.3 mm, a width of 4 mm, and a length of 70 mm was welded to an end of the positive electrode 21 where the active material was not applied.

On the other hand, a slurry of the negative electrode active material constituting the negative electrode 22 was prepared. Negative electrode active material: 90 parts by weight of graphite powder (average particle size: 20 μm) Binder: 10 parts by weight of vinylidene fluoride resin These were dispersed in N-methylpyrrolidone to obtain a slurry. This slurry was applied to both sides of a 15 μm thick current collector made of Cu, that is, a film-like electrode 22 s, and both sides were roll-pressed to produce a 140 μm-thick raw negative electrode. This material was cut into a width of 52.5 mm and a length of 550 mm, and the negative electrode 2 was cut.
2 was produced. Then, a Ni lead 27 having a thickness of 0.3 mm, a width of 5 mm, and a length of 65 mm was welded to an end of the negative electrode 22 where the active material was not applied.

The separator 23 was produced by cutting a 25 μm-thick microporous polyethylene film into a width of 54.5 mm.

The non-aqueous electrolyte was prepared by dissolving 1 mol / liter of LiPF ₆ in a mixed solvent of ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate.

The top cover 30 is made of a 0.4 mm thick S
A first metal layer 31 made of US304 and a clad material formed by cold press bonding of a second metal layer 32 made of 50 μm thick Al so that the second metal layer 32 made of Al is located on the safety valve 6 side. did. As described above, this clad material was processed into the dish shape shown in FIG. 4 and was ultrasonically welded to the safety valve 6 at the joint 35. Thereafter, the Al lead 7 and the Al subdisk 8 were welded. Then, a cylindrical sealed non-aqueous electrolyte secondary battery having a diameter of 18 mm and a height of 65 mm and having the configuration shown in FIG. 1 was produced.

[Comparative Example 1] The structure described with reference to FIG. 5, that is, the top cover 5 is made of only SUS304, and the top cover 5 and the safety valve 6 are connected to the respective flanges 5f and 6f.
This is a case in which a sealed nonaqueous electrolyte secondary battery is configured in the same size, shape, and configuration as in Example 1 except that the configuration is such that the overlapping portion f is simply pressed.

Comparative Example 2 In Comparative Example 1, the safety valve 6
Are ultrasonic bonding attempts at the overlapped portions of the respective flange portions 5f and 6f.

Example 1 according to the present invention and Comparative Examples 1
Table 1 shows the measurement results of the joint strength between the top cover 5 and the safety valve 6 and the change in resistance of the samples 2 and 2. In this measurement, the metal plates (referred to as A and B) constituting the top cover 5 and the safety valve 6 were joined by a joining method based on each of the examples and comparative examples, and one metal plate A was fixed. Then, one end of the other metal plate B is pinched and forcibly pulled up from the metal plate A in the direction of 90 °. Then, the surface peeled off by the pull was visually observed. As a result, in the metal configuration of Example 1, the base material was broken. That is, this peeling was not performed on the joint surface, and tearing occurred such that the constituent material of the metal plate, that is, the base material was broken. In this case, the resistance was measured by measuring the resistance between the respective center portions of the top cover and the safety valve, and the environmental test was performed by applying a heat cycle of −30 ° C. to + 70 ° C. and vibration. is there.

[0046]

[Table 1]

As is clear from the results shown in Table 1,
According to the present invention, it can be seen that the connection between the top cover and the safety valve can be made firmly, and the effects of heat history and vibration can be sufficiently improved as compared with the conventional structure.

In the first embodiment described above, the top cover and the safety valve are joined by ultrasonic welding. However, the above-described resistance welding, laser welding, friction welding, and cold welding Similar improvements were achieved in the case of press contact.

For example, the safety valve 6, the lead 7, the stripper disk 34, the sub disk 8, etc.
l It is not limited to the case where it is constituted by a single unit,
For example, it can also be constituted by the various Al alloys described above.

In the above-described example, the cylindrical non-aqueous electrolyte secondary battery has been described. However, the present invention can be applied to various other sealed batteries.

[0051]

As described above, in the present invention, the contact portion between the top cover and the safety valve is made of Al or an Al alloy, so that the heat cycle, that is, the heat history, the resistance due to the temporal change due to vibration, etc. , That is, an increase in the internal resistance of the battery can be effectively suppressed, and a sealed battery can be configured by maintaining a high output for a long period of time.

Further, when the contact portion between the top cover and the safety valve is made of the same material, the two can be brought into close contact with each other more satisfactorily, and a stronger connection can be made. Therefore, it is possible to form a strong battery in which the change over time with respect to temperature change and vibration is improved.

Further, Al or A is used as a top cover.
The use of a cladding layer made of a second metal layer made of a 1 alloy makes it possible to perform welding at a low temperature when joining with a safety valve as compared with a case of using a single-layer structure having a high melting point such as SUS, Fe, or Ni. As a result, distortion due to heat at the time of welding and generation of cracks can be suppressed, and a decrease in yield and a decrease in reliability due to impaired sealing performance can be avoided.

According to the structure of the present invention, the clad layer made of the second metal layer of Al or Al alloy having a lower electric resistivity than SUS, Fe or Ni is used as the top cover. The resistance of the top cover can be reduced.

Further, since the top cover and the safety valve can be connected firmly and stably as described above,
The resistance variation between the two can be made extremely small, the battery quality is stabilized, the inspection process is simplified, the workability is improved by lowering the defective product detection rate, and the cost is reduced by improving the yield. be able to.

On the other hand, the strength of the top cover is maintained not only by relatively soft Al or Al alloy as the top cover but also by the presence of the first metal layer of SUS, Fe or Ni having excellent mechanical strength. Can be.

Further, as described above, since the outer surface of the top cover can be constituted by the first metal layer made of SUS, Fe, or Ni, the connection with the outside, for example, a load or another battery can be prevented. The connection can be reliably and easily made by resistance welding or the like as well as the conventional one.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a main part of an example of a sealed battery according to the present invention.

FIG. 2 is a perspective view showing an open state of a battery body of an example of a sealed battery according to the present invention.

FIGS. 3A and 3B are plan views of main parts of a positive electrode and a negative electrode of an example of a sealed battery according to the present invention, respectively.

FIG. 4 is a plan view of a top cover of an example of a sealed battery according to the present invention.

FIG. 5 is a schematic sectional view of a main part of an example of a conventional sealed battery.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Outer can, 2 ... Battery body, 3, 4 ... Insulating thin plate, 5 ... Top cover, 5f ... Flange, 6 ...
・ Safety valve, 6f ・ ・ ・ Flange, 6p ・ ・ ・ Protrusion, 7,2
7 Lead, 8 Subdisk, 9 Gasket, 21 Positive electrode, 22 Negative electrode, 2
1s, 22s: Film electrode, 21m: Positive electrode active material, 22m: Negative electrode active material, 23: Separator, 24: Cylindrical core, 24h: Center hole, 30 ·
··· Top cover, 30f ··· flange, 30h ··· vent hole, 31 ··· first metal layer, 32 ··· second metal layer, 33 ··· ring-shaped insulator, · ..Stripper discs, 35 ... joints

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) AM04 AM05 AM07 AM16 BJ02 BJ14 BJ27 CJ05 DJ02 EJ01 HJ12

Claims (9)

[Claims] 1. A sealed battery having a top cover and a safety valve disposed at an open end of an outer can in which a battery body is housed, and having a contact portion where the top cover and the safety valve come into contact with each other. The top cover includes at least a first metal layer and Al.
Alternatively, the sealed battery is constituted by a clad material of a second metal layer made of a metal containing an Al alloy, and at least a surface of the top cover serving as the contact portion is constituted by the second metal layer. . 2. The sealed battery according to claim 1, wherein at least a part of a contact portion between the top cover and the safety valve is joined. 3. The non-aqueous electrolyte secondary battery main body having a lithium-containing compound in a positive electrode and a material capable of doping and undoping lithium in a negative electrode. 2. The sealed battery according to 1. 4. A method for manufacturing a sealed battery, wherein a top cover and a safety valve are disposed at an open end of an outer can in which a battery body is housed, and wherein the top cover and the safety valve have a contact portion where they come into contact with each other. Wherein the top cover comprises at least a first metal layer,
Alternatively, the top cover is formed of a clad material of a second metal layer made of a metal containing an Al alloy, and at least a surface of the top cover serving as the contact portion is formed of the second metal layer, and at least a part of the contact portion is joined. A method for manufacturing a sealed battery, comprising the steps of: 5. The method for manufacturing a sealed battery according to claim 4, wherein the bonding of the contact portions is performed by ultrasonic bonding. 6. The method for manufacturing a sealed battery according to claim 4, wherein the joining of the contact portions is performed by resistance welding. 7. The method for manufacturing a sealed battery according to claim 4, wherein the joining of the contact portions is performed by laser welding. 8. The method for manufacturing a sealed battery according to claim 4, wherein the joining of the contact portions is performed by friction welding. 9. The method for manufacturing a sealed battery according to claim 4, wherein the joining of the contact portions is performed by cold pressure welding.