Improvement of the cycling behavior of the Li/Li=CoO2 cell has been brought about by the use of esters and alkyl carbonate-based mixed solvents, and by physical modifications of the cathode structure. Binary solvent mixtures of methyl formate with either dimethyl carbonate, diethyl carbonate, or CO2 and LiAsF6 electrolyte exhibit superior resistance towards solvent oxidation as well as improved lithium cycling efficiencies. Use of these mixed solvents with newly developed thin cathodes has resulted in stable Li/Li=CoO2 cells which can be cycled more than 100 times at current densities of 1-10 mA cm -2, and at an average cell discharge voltage of between 3.9 and 3.7V. Due to the high rate of solid-state diffusion of Li § the LixCoO2 cathode can be charged at rates of up to 2 mAcm -2 over at least 100 deep charge and discharge cycles.

No abstract