Solid electrolyte battery

Details Solid electrolyte battery Solid electrolyte battery

2000-03-08

2002-09-03

Weiner, Laura (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Plural concentric or single coiled electrode

C429S094000, C429S211000, C429S300000, C429S304000, C429S178000, C429S181000

Reexamination Certificate

active

06444351

ABSTRACT:

RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P11-067031 filed Mar. 12, 1999 which application is incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a solid electrolyte battery incorporating a wound electrode constituted such that elongated positive and negative electrodes are laminated such that a solid electrolyte is sandwiched is wound in their lengthwise direction.
In recent years, a multiplicity of portable electronic apparatuses, such as camcoders, portable telephones and portable computers, are coming. An attempt has been made to reduce the size and weight of the apparatus. Also reduction in the size and weight of a battery serving as the portable power source of the electronic apparatus is required. Therefore, a lithium ion battery capable of meeting the requirement has been developed and industrially put into practical use. The foregoing battery incorporates a porous polymer separator disposed between the positive electrode and the negative electrode and impregnated with electrolytic solution. To prevent leakage of the electrolytic solution, the overall body of the battery is packaged in a thick and heavy metal container.
On the other hand, a solid-electrolyte battery incorporating a solid electrolyte which serves as the ion conductive material acting between the positive electrode and the negative electrode is free of leakage of solution. Therefore, the solid electrolyte battery is considered to be capable of reducing the size and weight of the battery by simplifying the package. In particular, attention is focused on a solid polymer electrolyte containing lithium salt which is dissolved in polymers as solid solution and a solid electrolyte in the form of gel (hereinafter called a “gel electrolyte”) such that matrix polymers contain electrolytes.
A gel electrolyte battery
10
incorporating the gel electrolyte, for example, as shown in
FIG. 1
, has a wound electrode hermetically enclosed in a casing film
11
. The wound electrode incorporates an elongated positive electrode
12
, an elongated negative electrode
13
disposed opposite to the negative electrode
13
and a gel electrolyte layer
14
disposed between the positive electrode
12
and the negative electrode
13
. The positive electrode
12
and the negative electrode
13
are laminated such that the gel electrolyte layer
14
is sandwiched between the positive electrode
12
and the negative electrode
13
. The formed laminate is wound many times in the lengthwise direction so that the wound electrode is constituted. A positive-electrode lead (not shown) is connected to the positive electrode
12
, while a negative-electrode lead
15
is connected to the negative electrode
13
.
The gel electrolyte battery
10
can be manufactured as follows.
The positive electrode
12
is manufactured as follows: a positive electrode mix containing a positive-electrode active material and a binder is uniformly applied to the two sides of a collector of the positive electrode. Then, the positive-electrode mix is dried so that a positive-electrode active material layer is formed. Then, drying is performed, and then a pressing process using a roll press is performed to obtain a positive-electrode sheet.
The negative electrode
13
is manufactured as follows: a negative electrode mix containing a negative-electrode active material and a binder is uniformly applied to the two sides of a collector of the negative electrode. Then, the negative-electrode mix is dried so that a negative-electrode active material layer is formed. Then, drying is performed, and then a pressing process using a roll press is performed to obtain a negative-electrode sheet.
The gel electrolyte layer
14
is formed as follows: sol electrolytic solution containing nonaqueous solvent, an electrolyte and matrix polymers is uniformly applied to the two sides of each of the positive-electrode sheet and the negative-electrode sheet, and then the two sheets are dried to remove the solvent. Thus, the gel electrolyte layer
14
is formed on the positive-electrode active material layer and the negative-electrode active material layer.
Then, the positive-electrode sheet having the gel electrolyte layer
14
formed thereon is cut into, for example, an elongated shape. Then, the gel electrolyte layer
14
and the positive-electrode active material layer in the portion in which the positive-electrode lead is welded is removed by cutting. The positive-electrode lead is welded to the cut portion so that the elongated positive electrode
12
having the gel electrolyte layer is obtained.
The negative-electrode sheet having the gel electrolyte layer formed thereon is cut into, for example, an elongated sheet. Then, the gel electrolyte layer and the negative-electrode active material layer in the portion in which the negative-electrode lead is welded is removed by cutting. The negative-electrode lead
15
is welded to the cut portion so that the elongated negative electrode
13
having the gel electrolyte layer is obtained.
Finally, the positive electrode
12
having the gel electrolyte layer
14
formed thereon and the negative electrode
13
having the gel electrolyte layer are laminated. The formed laminate is wound many times in the lengthwise direction so that the wound electrode is obtained. The wound electrode is sandwiched between the casing films
11
, and then the outermost peripheries of the casing films
11
are welded to each other with heat to seal the opened portions. Thus, the wound electrode is hermetically enclosed in the casing films
11
so that the gel electrolyte battery
10
is manufactured.
The gel electrolyte battery
10
incorporating the thus-manufactured wound electrode suffers from a problem of defective sealing when the wound electrode is hermetically enclosed in the casing films
11
.
The electrode leads disposed to overlap the elongated positive electrode
12
and the elongated negative electrode
13
in the widthwise direction of the electrodes
12
and
13
are welded for the overall width of the electrodes in order to reduce the internal resistance of the battery and improve the heavy load resistance.
The operation for sealing the opened portion of the casing films
11
is performed such that the space between the wound electrode and the casing films
11
is minimized to raise the volume energy density. At this time, an end of the electrode lead is sometimes caught by the sealed portion of the casing films
11
, as indicated with a circle B shown in FIG.
1
.
FIG. 1
shows a state in which an end of the negative-electrode lead
15
has been caught by the sealed portion of the casing films
11
.
If the end of the electrode lead is caught by the sealed portion of the casing films
11
, the portion cannot satisfactorily be sealed. The defective sealing and a damaged portion of the casing film caused when the electrode lead has been caught result in introduction of moisture into the space between the casing films
11
. Thus, an adverse influence is exerted on the performance of the gel electrolyte battery
10
.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a solid-electrolyte battery which is capable of preventing a problem that an electrode lead is caught by casing films when the casing films are sealed without any deterioration in the heavy load resistance and preventing defective sealing.
To achieve the foregoing object, according to one aspect of the present invention, there is provided a solid-electrolyte battery comprising: an elongated electrode; a positive-electrode lead connected to the positive electrode such that the long side of the positive-electrode lead is substantially in parallel with the widthwise direct ion of the positive electrode and formed into substantially a rectangular shape; an elongated negative electrode disposed opposite to the positive electrode; a negative-electrode lead connected to the negative electrode such tha

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