Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Cell enclosure structure – e.g. – housing – casing – container,...
Reexamination Certificate
2003-01-29
2004-02-24
Maples, John S. (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Cell enclosure structure, e.g., housing, casing, container,...
C429S181000, C429S184000
Reexamination Certificate
active
06696199
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery having a terminal and a ceramic insulating sleeve.
2. Description of the Prior Art
FIG. 17
shows an example of a structure of a conventional ceramic hermetic seal for a non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery comprises a winding type of elliptic-cylindrical electric power generating element
1
, an elliptic-cylindrical metallic case
2
that houses the electric power generating element
1
, and an elliptic lid plate
3
that is hermetically fixed to the metallic case
2
in such a manner that it is fitted into an upper opening of the metallic case
2
and welded thereto.
A positive terminal
4
and a negative terminal
5
connected to a positive electrode and a negative electrode, respectively, of the electric power generating element
1
each have a terminal supporting plate
7
attached thereto via an insulating sleeve
6
made of ceramic.
As shown in
FIG. 18
, the positive terminal
4
is hermetically fixed to the cylindrical insulating sleeve
6
in such a manner that it is inserted therein, and the corner formed by the positive electrode
4
and the upper surface of the insulating sleeve
6
is sealed with a brazing metal
8
. In turn, the insulating sleeve
6
is hermetically fixed to the terminal supporting plate
7
in such a manner that it is inserted in an opening in the terminal supporting plate
7
, and the gap therebetween is sealed with a brazing metal
10
.
The positive terminal
4
is made of an aluminum alloy that is not dissolved in a non-aqueous electrolyte at a potential of the positive electrode. An aluminum or aluminum-alloy-based brazing metal
8
is used for brazing between the positive terminal
4
and the insulating sleeve
6
, because the brazing metal will have the same potential as the positive terminal.
Since the terminal supporting plate
7
is insulated from the positive electrode, it may be made of an aluminum alloy, stainless steel, nickel-plated iron or the like. The brazing metal
10
between the terminal supporting plate
7
and the insulating sleeve
6
may be appropriately selected, not being limited to the aluminum or aluminum-alloy-based brazing metal.
On the other hand, as shown in
FIG. 19
, the negative terminal
5
is hermetically fixed to the cylindrical insulating sleeve
6
in such a manner that it is inserted therein, and the gap between the negative electrode
5
and the insulating sleeve
6
is sealed with a brazing metal
9
. In turn, the insulating sleeve
6
is hermetically fixed to the terminal supporting plate
7
in such a manner that it is inserted in an opening in the terminal supporting plate
7
, and the gap therebetween is sealed with the brazing metal
10
.
The negative terminal
5
is made of a copper alloy, nickel alloy or the like, which is not susceptible to electrochemical corrosion at a potential of the negative electrode. A copper-alloy-based brazing metal
9
, such as a gold-copper brazing, is used for brazing between the negative terminal
5
and the insulating sleeve
6
, because the brazing metal will have the same potential as the negative terminal
5
.
Since the terminal supporting plate
7
is insulated from the negative electrode, it may be made of an aluminum alloy, stainless steel, nickel-plated iron or the like. The brazing metal
10
between the terminal supporting plate
7
and the insulating sleeve
6
is the same as that of the positive terminal
4
.
The terminal supporting plates
7
each having the positive terminal
4
or negative terminal
5
hermetically fixed thereto via the insulating sleeve
6
are hermetically fixed to the lid plate
3
in such a manner that they are inserted in openings at both ends of the lid plate and welded thereto. Then, the electric power generating element
1
mounted below the lid plate
3
is inserted in the metallic case
2
, and the lid plate
3
is fitted into the upper opening of the metallic case
2
and welded thereto. In this way, the battery sheath is sealed.
The ceramic material used for the insulating sleeve
6
has a coefficient of thermal expansion that is extremely lower than that of the aluminum alloy used for the positive terminal
4
, and is quite lower than that of the copper alloy used for the negative terminal
5
.
Accordingly, a battery, such as a non-aqueous electrolyte secondary battery, having such a conventional ceramic hermetic seal structure has a problem in that a distortion may occur between the positive terminal
4
or negative terminal
5
and the insulating sleeve
6
due to a variation of temperature, and the distortion stress may be concentrated in the insulating sleeve
6
to cause a crack in the ceramic material, resulting in a degradation of air tightness of the battery sheath.
Thus, the positive terminal
4
, which has a coefficient of thermal expansion especially largely different from that of the insulating sleeve, has been devised in terms of arrangement. That is, the brazing metal
8
is prevented from entering into the gap between the positive terminal
4
and the insulating sleeve
6
in order for the insulating sleeve
6
to be affected by expansion or shrinkage of the positive terminal
4
as little as possible, as shown in FIG.
18
. However, such an arrangement could not completely prevent a crack from occurring in the ceramic insulating sleeve
6
.
The stress of the distortion between the positive terminal
4
or negative terminal
5
and the insulating sleeve
6
may also be concentrated in the brazing metal
8
or
9
to cause a crack in the brazing material. A detailed research concerning why the crack occurs in the brazing material has proved that, when the brazing material applied to the terminal is cooled, a void is produced in the brazing material due to volumetric shrinkage of the brazing material, and the void causes occurrence of a crack.
If a crack exists in the brazing material, a problem may arise in that the crack develops to pierce through the brazing material, thereby degrading air tightness of the battery sheath. In such a case, there is an additional problem in that water is introduced into the battery and reacts with an active material (lithium if the battery is a lithium secondary battery, for example) to reduce the battery capacity or increase the internal resistance of the battery, which leads to decrease of the life of the battery.
SUMMARY OF THE INVENTION
The present invention has been devised to address such a circumstance. An object of the invention is to provide a battery having a terminal structure adapted to prevent an insulating sleeve or brazing metal from being damaged by a distortion caused by a difference in coefficient of thermal expansion between the metallic terminal and the insulating sleeve made of ceramic.
A battery according to the invention comprises: an insulating sleeve made of ceramic hermetically fixed into an opening in a battery sheath made of metal; a metallic terminal inserted in the insulating sleeve; and a metallic ring fitted over the metallic terminal. The metallic ring and the metallic terminal are hermetically fixed to each other by a brazing metal and the metallic ring and the insulating sleeve made of ceramic are hermetically fixed to each other by a brazing metal.
According to the arrangement, the metallic terminal and the insulating sleeve made of ceramic are fixed to each other via the metallic ring. Therefore, even if when the temperature varies, a dimension of the gap between the terminal and the insulating sleeve changes to cause a distortion due to the difference in coefficient of thermal expansion between metal and ceramic, the distortion can be accommodated by the metallic ring being deflected. Thus, a crack can be prevented from occurring in the insulating sleeve with reliability.
Preferably, the metallic ring is fixed to support the metallic terminal at an upper end face and/or lower end face of the insulating sleeve.
This can improve reliability of the terminal structure because the metallic ring
Hatanaka Teruhiro
Imamura Nobutaka
Inoue Takefumi
Iwamoto Tatsuya
Kamata Kouji
Japan Storage Battery Co., Ltd.
Maples John S.
Wenderoth , Lind & Ponack, L.L.P.
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