Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Patent
1993-05-13
1995-01-24
Kalafut, Stephen
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
205 58, H01M 460
Patent
active
053842154
DESCRIPTION:
BRIEF SUMMARY
This application is a national phase application, filed under 35 USC 371, of PCT/JP91/01559, published under International Publication Number WO 92/09112.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a polypyrrole shaped material suitable for use as an electrode for a secondary battery, a process for production thereof, and a secondary battery. More particularly, the present invention relates to a polypyrrole shaped material enabling charging and discharging at high current densities and having large charging and discharging capacities, a process for production thereof, and a secondary battery using said polypyrrole shaped material as an electrode.
DESCRIPTION OF RELATED ART
It is known that, in general, conducting polymers show high electrical conductivity and, moreover, can be oxidized and reduced electrochemically. It is further known that the oxidation or reduction reaction of a conducting polymer is accompanied by the outflow or inflow of the counter ion contained therein. Because of this function, conducting polymers are used as electrodes, and there have been proposed electrodes using a polypyrrole, a polythiophene, a polyaniline or the like.
When the conventionally proposed conducting polymers are used as electrodes, however, the electrodes have problems in that they allow neither charging nor discharging at high current densities and that they have no large charging and discharging capacities. In order to solve these problems, Japanese Patent Application Kokai (Laid-Open) No. 48749/1988 discloses an electrode obtained by polymerization under the application of full-wave-rectified voltage and Japanese Patent Application Kokai (Laid-Open) No. 48750/1988 discloses an electrode obtained by polymerization under the application of asymmetrical voltage. In these proposals, a polypyrrole or a polythiophene is mainly used as a conducting polymer.
In the conducting polymers obtained by the conventional controlled-current or controlled-potential polymerization, the properties are not uniform throughout the whole portion; when such a conducting polymer is used as an electrode of cell, the cell reaction takes place disproportionately in part of the electrode; tending to invite a rise in charging voltage at an early stage, resulting in reduction in charging and discharging capacities of the cell. In contrast, in the conduction polymers obtained by polymerization according to the above proposals, the above drawback has been alleviated.
Even the conducting polymers obtained according to the above proposals, however, are not sufficiently effective when produced in a thick film, although they are effective when produced in a thin film. That is, even the conducting polymers obtained according to the above proposals are not sufficiently free from a drawback that the charging and discharging accompanied by the outflow and inflow of counter ions proceed smoothly in the vicinity of the film surface but do not proceed smoothly within the film inside because the diffusion of counter ion is not smooth within the film inside and thus the charging and discharging take place disproportionately in the vicinity of the film surface. Generally in secondary batteries, in order to obtain large charging and discharging capacities with a small film area, there is used a thick film of 100 .mu.m or more in thickness and, depending upon the case, of 1 mm in thickness. In secondary batteries using such a film thickness, it is therefore difficult to obtain sufficiently large charging and discharging capacities even when an improved electrode such as mentioned above is used. This is particularly noticeable when discharging is made at a high current density.
Meanwhile, Japanese Patent Application Kokai (Laid-Open) No. 2468/1987 proposes to form a conducting polymer film containing an ion of large ionic radius and assemble it into a cell using an ion of small ionic radius as an electrolyte. This proposal was made in order to achieve the smooth outflow and inflow of ions by using a counter ion of small size and
REFERENCES:
patent: 4472488 (1984-09-01), Maxfield et al.
patent: 4543306 (1985-09-01), Bubols et al.
patent: 4818646 (1989-04-01), Takakubo et al.
patent: 5151162 (1992-09-01), Muller et al.
Hagiwara Tsuneo
Sato Kazuhiko
Yamaura Michio
Kalafut Stephen
Teijin Limited
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