ELECTROCHEMICAL SYNTHESIS OF COMPOSITE FILMS OF MANGANESE-DIOXIDE ANDPOLYPYRROLE AND THEIR PROPERTIES AS AN ACTIVE MATERIAL IN LITHIUM SECONDARY BATTERIES

Composite films of polypyrrole and beta-MnO2 or lithiated MnO2 (Li-MnO 2) particles have been synthesized for use as cathode-active materials of rechargeable lithium batteries. The composite films were prepared by electrolysis of pyrrole dissolved in propylene carbonate solution i n the presence of suspended MnO2 particles. The maximum amount of the incorporation of MnO2 was 50.2 and 40.6 weight percent for beta-MnO2 a nd Li-MnO2, respectively. It was found that both polypyrrole and the i ncorporated MnO2 worked as the active material with one potential plat eau in the charge-discharge test conducted in a mixed solution of prop ylene carbonate and dimethoxyethane in which LiClO4 was dissolved. Fur thermore, it was shown that polypyrrole worked as a conducting network for the incorporated MnO2. Though the utilization of the incorporated MnO2 was not high (beta-MnO2 and Li-MnO2 gave 0.23 and 0.57, respecti vely), the composite films prepared under optimal electrolysis conditi ons gave the specific energy density on volume basis of more than 150% of that obtained for a fully-utilized MnO2-free polypyrrole. Elementa l analysis of the composite films revealed that electrolyte anions alo ne were involved in the redox reaction of polypyrrole of the composite films and Li+ ions in the redox reaction of the incorporated MnO2.