JP2000090888A - Flat battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the occurrence of battery short circuit and liquid leakage when an opening end of a battery case formed into a bottomed cylindrical shape of an elliptic shape in cross section is sealed by crimp sealing. SOLUTION: Semi-circular portions B, C formed on both the sides of a battery case 1 break a gasket insulating between the battery case 1 and a sealing plate and generates battery short circuit when an opening end is increased in thickness due to overlapping of folding pieces by caulking work in sealing and pressurizing amount of caulking work is increased. When pressurizing amount is reduced, sealability is lowered and liquid leakage is caused. By forming thickness of the semi-circular portions B, C thinner than that of a linear portion A, an increase in thickness due to overlapping is reduced and battery short circuit is not caused, even if pressurizing amount is increased so as not to cause liquid leakage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat battery which is formed in a flat shape so that a portable electronic device such as a portable telephone can be reduced in size and thickness.

[0002]

2. Description of the Related Art As portable electronic devices such as portable telephones have become smaller and lighter and thinner, batteries used as power sources have also been required to be smaller and thinner. As an example of a battery developed in response to such a demand, a flat type lithium ion secondary battery as shown in FIG. 4 is known.

In this flat battery, as shown in FIG. 5, a power generation element 22 is accommodated in a battery case 21 and a battery case 2 is provided.
1 is formed by disposing a sealing plate 23 at the open end via a gasket 24 and crimp-sealing the open end.
The crimp sealing is performed by placing the gasket 24 and the sealing plate 23 on the narrowed portion 25 in which the neck of the battery case 21 is narrowed inward.
The gasket 24 is compressed between the narrowed portion 25 and the folded open end, and the battery case 21 is sealed by the sealing plate 23. .

[0004]

FIG. 6 shows a crimp-sealing of the open end of a battery case 21 formed in a bottomed cylindrical shape having an oblong cross section like the flat battery having the above structure. As described above, in the case of the oblong battery case 21 in which the semicircular portions b, b are formed at both ends of the linear portions a, a crimping fold is in the center direction of the arc in the semicircular portions b, b. Therefore, the folded portions overlap each other between the adjacent portions, and the thickness thereof increases. If pressure is applied while the thickness of the folded portion is increased, the leading end of the folded portion may break through the gasket 24 and reach the sealing plate 23 as shown in FIG. Sealing plate 2
Since the battery case 21 and the battery case 21 form the external output terminals of the positive and negative electrodes of the battery, respectively, the battery case 21 and the sealing plate 23 are insulated from each other by the gasket 24. When the tip of the bent portion comes into contact with the sealing plate 23, a short circuit occurs, which causes a problem that a battery failure occurs. If the amount of pressurization at the time of crimping is reduced so that this short circuit does not occur, the gasket 24 is compressed to reduce the hermeticity of sealing between the battery case 21 and the sealing plate 23. Will be generated.

[0005] An object of the present invention is to provide a flat battery in which an open end of a battery case formed into an oval cross section does not cause a short circuit and does not cause liquid leakage when the open end is crimped. Is to provide.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a battery case formed in a bottomed cylindrical battery case having a flattened oval cross section. In a flat battery in which the opening end of the battery case is sealed by caulking and fixing a sealing plate to the opening end of
A predetermined range centered on a semicircular portion formed on both sides of the battery case is formed to be thinner than the thickness of the straight portion.

According to this configuration, when the open end of the battery case having a flat cross section formed into a flat elliptical shape is folded inward at the time of sealing, a predetermined range centered on the semicircular portions on both sides is made thinner than the linear portion. By being formed, even if adjacent portions overlap each other, the increase in the thickness does not increase extremely due to the thin-walled shape, and is arranged between the battery case and the sealing plate. It does not pierce the gasket and cause a short circuit. Therefore, no short circuit occurs even if the pressurization amount of the caulking process is increased so as not to cause liquid leakage.

[0008] In the above-described structure, by forming a predetermined area not in contact with the straight part of the semicircular part to be thinner than other thin part forming parts, the thinner part is formed by focusing on the arc side where overlap is likely to occur due to folding. The effect of can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
The embodiment described below is an example embodying the present invention, and does not limit the technical scope of the present invention.

The flat battery according to the present embodiment has the same outer shape and internal structure as those of the conventional structure shown in FIGS. 4 and 5, and is obtained by improving the structure of the battery case. Is configured as

The battery case 1 used in the flat battery according to the first embodiment has a cylindrical shape with a bottom and an oval cross section, and the thickness of the side peripheral surface is as shown in FIG. The linear portion A and the semicircular portions B and C are configured to be different. The semicircular portions B and C are 120 ° from the center of the semicircular arc.
Is defined as a semicircular portion C, and a range of 60 ° from the semicircular portion C toward the straight portion A is defined as a semicircular portion B. The thickness of the side peripheral surface of each part is such that the thickness of the linear part A is 400 μm and the thickness of the semicircular parts B and C is 300 μm,
The semicircular portions B and C are formed so as to be thinner than the straight portion A.

Further, as shown in FIG. 2, the battery case 11 used in the flat battery according to the second embodiment has a thickness of 400 μm at the linear portion A and a thickness of 30 μm at the semicircular portion B.
0 μm, the thickness of the semicircular portion C is 200 μm, and the thickness of each portion is different.

A power generation element is accommodated in the battery case 1 having the structure of the first embodiment, and as shown in FIG.
The gasket 2 and the sealing plate 3 are arranged on the narrowing portion 4 formed on the opening end side of the battery case 1, and the opening end 1 a of the battery case 1 is folded inward as shown in FIG. The opening end of the battery case 1 is sealed by a crimp seal that compresses and fixes the sealing plate 3 by crimping. When the crimp is closed, the open end 1 of the battery case 1 is closed.
The straight portion A of FIG. 1A is folded flat, while the semicircular portions B and C are bent so as to be narrowed toward the center of the arc, so that wrinkles are formed, and the adjacent portions overlap each other to increase the thickness of the folded portion. become. However, since the thickness of the semicircular portions B and C is formed to be thinner than the thickness of the straight portion A as described above, the increase in the thickness of the folded portion becomes equal to that of the straight portion A even if an overlap occurs. The disadvantage caused by the increase in the thickness of the semicircular portion B during the crimping process is eliminated.

As shown in FIG. 2B, the height h from the upper end of the narrowing portion 4 to the folding position of the opening end 1a changes depending on the amount of pressure applied during the crimping, and the height h decreases. When the amount of pressurization is increased, the gasket 2 is compressed and the sealing property of the battery case 1 is improved. However, the folded end portion of the opening end 1a breaks through the gasket 2 and comes into contact with the sealing plate 3,
There is a risk of short-circuit failure of the battery. Conversely, height h
When the amount of pressurization is reduced so that
Although there is no danger that the gasket 2 will break through the gasket 2, the compression of the gasket 2 will be reduced, so that the sealing property of the battery case 1 will be reduced and the electrolyte will leak. Battery case 1 of the present embodiment
Then, when the amount of pressurization during the crimping process is increased to improve the sealing property of the battery case 1, the thickness of the semicircular portions B and C where the battery short circuit is most likely to occur is made thinner than the straight portion A. Therefore, even if the pressure in the caulking process is increased to improve the sealing property, occurrence of a battery short circuit can be suppressed.

Since the semicircular portion B has a large radius of an arc connected to the straight portion A, wrinkles are less likely to occur during crimping than the semicircular portion C. Therefore, as in the configuration of the second embodiment shown in FIG. 2, the semicircular portion C having the largest overlap due to wrinkles is formed to be the thinnest, and the thickness of the semicircular portion B and the straight portion A is increased in this order. By doing so, the increase in thickness due to the overlap becomes substantially uniform in the semicircular portions B and C, and the degree of breaking through the gasket 2 and causing a battery short circuit is further reduced.

The caulking dimension h shown in FIG. 3B is changed between the configuration of each of the first and second embodiments described above and the conventional configuration in which the thickness of the side peripheral surface is made uniform over the entire circumference. Then, 20 batteries each were prepared, and the breaking rate at which the gasket 2 was broken and the electrolyte leakage rate were verified. In addition, the liquid leakage rate was determined by reading the presence or absence of liquid leakage after storing in an environment of 80 ° C. for 2 weeks.

Table 1 shows the results of the verification.
(1) to (5) use the battery case 21 having the conventional configuration, and (6) to (11) use the battery case 1 having the configuration of the first embodiment. 18)
Shows a case where the battery case 21 having the configuration of the second embodiment is used.

[0018]

[Table 1]

As is evident from the verification results shown in Table 1, the gasket 2 is not broken in the configuration of each embodiment unless liquid is applied more than necessary at the time of caulking, and liquid leakage does not occur. Since the generated crimping strength can also be clearly determined, it is easy to set the crimp sealing condition that does not cause gasket breakage or liquid leakage.

[0020]

As described above, according to the present invention, the range of caulking conditions when sealing the open end of the battery case with the sealing plate is wide, and the conditions can be easily set. The crimp sealing that does not cause leakage can be performed, and the productivity of the battery can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view of an open end side of a battery case according to a first embodiment.

FIG. 2 is a plan view of an open end side of a battery case according to a second embodiment.

FIG. 3 is a schematic view showing a procedure for closing an open end of a battery case.

FIG. 4 is a perspective view showing the appearance of a flat battery.

FIG. 5 is a cross-sectional view showing the internal configuration of a flat battery.

FIG. 6 is a plan view of an open end side of a battery case according to a conventional configuration.

FIG. 7 is a schematic diagram showing a state in which a gasket is broken.

[Explanation of symbols]

 1, 11 battery case 2 gasket 3 sealing plate A linear part B, C semicircular part

Claims (2)

[Claims] 1. A power generation element is accommodated in a battery case formed in a cylindrical shape with a bottom and having a flattened oval cross section, and a sealing plate is caulked and fixed to an open end of the battery case via a gasket. In the flat battery in which the opening end of the battery case is sealed, a predetermined range centered on a semicircular portion formed on both sides of the battery case is formed to have a thickness smaller than the thickness of the straight portion. A flat-type battery characterized by the above-mentioned. 2. The flat battery according to claim 1, wherein the predetermined portion of the semicircular portion not in contact with the linear portion is formed thinner than the other thin portion.