Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1998-12-15
2001-08-21
Weiner, Laura (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S213000
Reexamination Certificate
active
06277518
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electrode materials for use in batteries, and electrodes and batteries using the same.
2. Description of the Related Art
In conventional polymer batteries, electrically conductive &pgr;-conjugated polymers formed by electrochemical or chemical polymerization have been used as electrode materials. For example, the use of polyacetylene for electrodes was reported in J. Chem. Soc. Chem. Commun., (1981) 317-319. Thereafter, extensive investigations on polyaniline, polypyrrole, polythiophene and the like have been carried out, and books for the explanation of batteries using electrically conductive polymers have already been published.
However, when an electrically conductive &pgr;-conjugated polymer alone is used, the resulting capacity is limited because of the reaction of 0.5 to 1 electron per monomeric unit.
Accordingly, in order to increase the capacity, it has been intended to fabricate a composite electrode by forming an electrically conductive &pgr;-conjugated polymer by electrochemical or chemical polymerization and then adding thereto a quinone compound which has poor electronic conductivity but can induce an oxidation-reduction reaction. For example, a composite electrode formed from polyaniline and benzoquinone has been reported in Synth. Met., 83 (1996) 89-96. In this composite electrodes, the proportion of a part contributing to a oxidation-reduction reaction per molecular weight is increased, resulting in an increased capacity. The reason for this is that, while the use of an electrically conductive &pgr;-conjugated polymer alone gives a low capacity because of the reaction of 0.5 to 1 electron per monomeric unit, the combined use of benzoquinone can add its oxidation-reduction capacity thereto. Moreover, the oxidation-reduction reaction of quinone proceeds rapidly as a result of interaction between the nitrogen atoms of polyaniline and benzoquinone, resulting in an enhanced power density.
However, batteries using such composite electrodes have the disadvantage that, as the number of charge-discharge cycles is increased, the quinone compound is eliminated to cause a decrease in capacity.
On the other hand, an electrode formed by adding an electrically conducting additive (e.g., carbon) to an unconjugated polymer having no electrical conductivity, such as an electrode using a polymer of benzoquinone as the unconjugated polymer, has been investigated. However, also with respect to batteries using such electrodes, it has been reported that, as the number of charge-discharge cycles is increased, the contact between the polymer and the electrically conducting additive is lost to cause a decrease in capacity.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide batteries having excellent cycle characteristics and a high power density, as well as electrodes and electrode materials for use therein.
Accordingly, the present invention relates to an electrode material for use in batteries which comprises a polymer comprised of structural units having a basic structure derived from a nitrogen-containing compound and a quinone compound.
Moreover, the present invention relates to an electrode material for use in batteries which comprises a copolymer comprised of monomeric units having a basic structure derived from a nitrogen-containing compound and a quinone compound, and monomeric units forming a &pgr;-conjugated polymer.
Furthermore, the present invention relates to a battery electrode comprising one of the aforesaid electrode materials for use in batteries.
Moreover, the present invention relates to a battery using, as at least one electrode thereof, the battery electrode comprising one of the aforesaid electrode materials for use in batteries.
In the present invention, the nitrogen atom(s) of the nitrogen-containing compound and the active group of the quinone compound (hereinafter referred to as the “quinone active group”) are present in the same molecule and, moreover, in the same structural units of the polymer. Thus, the oxidation-reduction reaction at the quinone site is efficiently accelerated to cause an enhancement in power density. This effect is suggested in Synth. Met., 83, 89 (1996), where it is reported that, on a composite electrode fabricated by synthesizing polyaniline by electrolytic polymerization and sweeping it in an aqueous solution of benzoquinone, the oxidation-reduction reaction of quinone proceeds rapidly as a result of interaction between the nitrogen atoms of polyaniline and the quinone.
Moreover, since the nitrogen-containing compound and the quinone active group are present in the same molecule, the battery can be repeatedly charged and discharged without eliminating the quinone active groups from the electrode, resulting in improved cycle characteristics.
Furthermore, as compared with the case in which molecules having a quinone active group and a polymer having nitrogen atoms are simply mixed together, the molecular weight required for the reaction of each electron is reduced because nitrogen atoms and quinone active groups are present in the same molecule. That is, the theoretical capacity is increased owing to the presence of nitrogen atoms and quinone active groups in the same molecule.
In addition, when the aforesaid polymer is copolymerized with a monomer forming an electrically conductive polymer, quinone active groups inherently having poor electronic conductivity, together with electrically active polymeric units, are present in the same molecule. Thus, the copolymer can retain electronic conductivity even if its contact with an electrically conducting additive is lost, resulting improved cycle characteristics.
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D. MacInnes et al., “Organic Batteries: Reversible n- and p- Type Electrochemical Doping of Polyacetylene, (CH)x”, J. Chem. Soc. Chem. Commun., (1981), pp. 317-319.
E.S. Matveeva, “Could the acid doping of polyaniline represents the charge transfer interaction”, Synthetic Metal s 83, (1996), pp. 89-96.
V.K. Gater et al., “Quinone molecular films derived from aminoquinones”,J. Electroanal. Chem., vol. 257, 1988, pp. 133-146.
V.K. Gater et al., “Quinone Molecular Films Derived from 1,5-Diaminoanthra-quinone”J. Electroanal. Chem., vol. 235, 1987, pp. 381-385.
L. Roullier et al., “Electrodes Modified by a Thick Deposit of an Organic Compound”,Journal of Electrochemical Society, vol. 132, No. 5, 1985, pp. 1121-1125.
S. Moteki et al., “Synthetic and electrochemical studies of anthraquinone-substituted poly(pyrrole) films”,Journal of Electroanalytical Chemistry, vol. 447, 1998, pp. 91-95.
M.S. Hossain et al., “The Electrochemistry of Graphite and Modified Graphite Surfaces: The Reduction of O2”,Electrochimica Acta, vol. 34, No. 12, 1989, pp. 1733-1737.
M. Fujihara et al., “Photo-assisted Electrochemical Oxidation of Isopropanol to Acetone Sensitized by Photoexcited Anthraquinone Derivatives Chemically Bound on a Carbon Electrode”,J. Electroanal. Chem., vol. 137, 1982, pp. 163-170.
Harada Gaku
Kurihara Junko
Manago Ari
Naoi Katsuhiko
Nishiyama Toshihiko
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
Weiner Laura
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