A Study of Cobalt and Manganese Fluorides as Cathode Materials for Rechargeable Lithium Cells

This paper describes a study of the lithium/transition metal fluoride cells using nanocomposites of carbon with cobalt or manganese fluorides as cathode materials. The nanocomposite cathode materials were prepared by high energy milling of carbon and metal fluorides. It was, however, found that cobalt trifluoride reacted with carbon during the high energy milling process to form carbon fluoride. The Li/cobalt fluoride cells were, therefore, studied by using nanocomposite cathodes prepared by high energy milling of carbon, cobalt metal and lithium fluoride or cathodes prepared by mixing carbon and cobalt trifluoride without subjecting the mixture to the high energy milling process. The charge- discharge characteristics of lithium/transition metal fluoride cells were studied at 22oC and 50oC using a 1M LiPF6-sulfolane solution as the electrolyte. The cells were found to be electrochemically reversible but could not be completely charged due to simultaneous oxidation of the electrolyte at potentials above ~4.5 Volts.