Structure and composition of composite cathodes used in solid state lithium polymeric batteries

There is considerable current interest in the development of advanced rechargeable lithium batteries containing ionically conducting solid polymeric electrolytes. The cathodes in some of these batteries consist of an electroactive material embedded in a matrix of electrolyte to form a flexible film. Typically, the cathode materials are insertion compounds such as V/sub 6/O/sub 13/ or TiS/sub 2/ and the electrolytes are combinations of poly(ethyleneoxide), PEO and lithium salts such as lithium trifluoromethanesulphonate, LiCF/sub 3/SO/sub 3/. The aim of this work was to gain an increased understanding of the cathode region of solid state batteries of the type Li/PEO/sub n/:LiCF/sub 3/SO/sub 3//V/sub 6/O/sub 13/. The cathode region typically consists of 45% by volume of the elecrochemically active material, V/sub 6/O/sub 13/ and 5% of acetylene black in particulate form, together with 50% of an ionically conducting matrix of PEO/sub 9.0/:LiCF/sub 3/SO/sub 3/. It was hoped that a better characterisation of the cathode region, particularly its morphology, would enable important aspects of the problem of loss of battery capacity with usage to be effectively addressed. Results are reported of SEM/EDX, polarising microscopy and complex impedance conductivity studies of the influence of morphology on the behaviour of thin polymeric catholyte films