CARBON-FIBER AS A NEGATIVE ELECTRODE IN LITHIUM SECONDARY CELLS

The charge and discharge behaviors of lithium cells with carbon fiber M-46 (Toray Industries, Incorporated) electrodes have been examined using 1M LiClO4 in a mixture of propylene carbonate (PC) and 1,2-dimethoxyethane (DME). The carbon fiber has good reversible anode performance for lithium secondary cells. The lithium storage mechanism was examined by x-ray photoelectron spectroscopy, x-ray diffraction, differential thermal analysis-thermogravimetry, and electrochemical measurements. Lithium intercalates into the carbon fiber M46 after an irreversible capacity loss during the first discharge. The first discharge mechanism, which has been mainly attributed to the formation of a passivating film on the carbon surface, is complicated; the mechanism changes with the electrolyte composition and with the discharge current density. Composite anodes of lithium metal and carbon fiber were examined in a cell with Cr3O8 cathodes and were found to significantly improve the charge and discharge property compared to pure lithium anodes, since lithium dendrite formation was reduced.