Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1999-07-07
2001-08-14
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S212000, C429S214000
Reexamination Certificate
active
06274268
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to polymer secondary batteries having a high rate of appearance of capacity and excellent cycle characteristics, and methods of making the same.
2. Description of the Prior Art
In the positive and negative electrodes of conventional secondary batteries, an electrically conducting additive such as carbon is used together with an electrode active material in order to enhance its electrical conductivity.
FIG. 4
is a schematic view showing the structure of such an electrode. An electrically conducting additive
53
is dispersed in a film of an electrode active material
52
which is formed on a current collector
51
.
However, the use of an organic compound polymer as an electrode active material involves various problems. They include, for example, low efficiency in the utilization of the active material, a low rate of appearance of battery capacity, and the inability to use a substance having low electronic conductivity as an active material. According to investigations made by the present inventors, organic compound polymers generally have poor electronic conductivity when used as active materials, so that the oxidation-reduction reactions do not proceed rapidly. If it is tried to enhance electrical conductivity by adding an electrically conducting additive in large amounts, the rate of appearance of capacity is reduced owing to a limited amount of the active material. Moreover, it has been found that the mere addition of an electrically conducting additive to an electrode active material fails to impart sufficient electrical conductivity thereto because the area of contact between the carbon and the active material is limited to result in low bond strength.
Meanwhile, it is described in Japanese Patent Laid-Open Nos. 74051/′ 91 and 290852/′ 93 that polypyrrole is formed on a carbon electrode by electrolytic polymerization. However, these patents have the disadvantage that, since polypyrrole is formed on a mass of carbon shaped into an electrode, the active material cannot be secured in such an amount as to give a sufficient capacity.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a polymer secondary battery having a high rate of appearance of capacity and excellent cycle characteristics, and another object of the present invention is to provide methods of making the same.
The present invention is directed to a polymer secondary battery using, for at least one of the positive and negative electrodes, a polymer-carbon composite material comprising powdered carbon having its surfaces coated with an organic compound polymer capable of adsorbing and desorbing protons electrochemically.
In one embodiment of the present invention, the aforesaid polymer-carbon composite material is obtained by chemically polymerizing a monomer yielding the organic compound polymer in the presence of the powdered carbon, and removing the solvent from the resulting polymerization product. In this particular embodiment, electrolytic polymerization is not used to produce the organic compound polymer.
In another embodiment of the present invention, the aforesaid polymer-carbon composite material is obtained by dispersing the powdered carbon in a solution of the organic compound polymer, and removing the solvent from the resulting dispersion.
Moreover, the present invention is also directed to a method of making a polymer secondary battery which comprises the steps of providing a polymer-carbon composite material obtained by polymerizing, in the presence of powdered carbon, a monomer yielding an organic compound polymer capable of adsorbing and desorbing protons electrochemically, and removing the solvent from the resulting polymerization product; and fabricating at least one of the positive and negative electrodes by forming a layer of the polymer-carbon composite material on a current collector.
Furthermore, the present invention is also directed to a method of making a polymer secondary battery which comprises the steps of providing a polymer-carbon composite material obtained by dispersing powdered carbon in a solution containing an organic compound polymer capable of adsorbing and desorbing protons electrochemically, and removing the solvent from the resulting dispersion; and fabricating at least one of the positive and negative electrodes by forming a layer of the polymer-carbon composite material on a current collector.
REFERENCES:
patent: 5324599 (1994-06-01), Oyama et al.
patent: 5462566 (1995-10-01), Skotheim
patent: 3-74051 (1991-03-01), None
patent: 4-146965 (1992-05-01), None
patent: 5-28823 (1993-02-01), None
patent: 5-290852 (1993-11-01), None
patent: 8-96799 (1996-04-01), None
patent: 8-109196 (1996-04-01), None
patent: 9-22733 (1997-01-01), None
patent: 9-92281 (1997-04-01), None
patent: 9-115519 (1997-05-01), None
Oyama et al., “Organosulfur polymer batteries . . . ” Journal of Power Sources, vol. 68, Issue 1, pp. 135-138, Sep. 1997.
Fujiwara Masaki
Harada Gaku
Nishiyama Toshihiko
Okada Shinako
Chaney Carol
NEC Corporation
Young & Thompson
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