Electrochemical Synthesis of Composite Films of Manganese Dioxide and Polypyrrole and Their Properties as an Active Material in Lithium Secondary Batteries

Composite films of polypyrrole and or lithiated 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 in the presence, of suspended particles. The maximum amount of the incorporation of was 50.2 and 40.6 weight percent for and , respectively. It was found that both polypyrrole and the incorporated worked as the active material with one potential plateau in the charge‐discharge test conducted in a mixed solution of propylene carbonate and dimethoxyethane in which was dissolved. Furthermore, it was shown that polypyrrole worked as a conducting network for the incorporated . Though the utilization of the incorporated was not high ( and gave 0.23 and 0.57, respectively), the composite films prepared under optimal electrolysis conditions gave the specific energy density on volume basis of more than 150% of that obtained for a fully‐utilized . Elemental analysis of the composite films revealed that electrolyte anions alone were involved in the redox reaction of polypyrrole of the composite films and Li+ ions in the redox reaction of the incorporated .