We have examined various solvents and solutes as electrolytes for high voltage lithium metal secondary cells in terms of the oxidation potential, specific conductivity and cycling performance of Li/LiMn1.9Co0.1O4 cells. We selected propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), 1,2-dimethoxyethane (DME) and 1,2-diethoxyethane (DEE) as the solvents, and LiClO4, LiPF6, LiAsF4 and LiBF4 as the solutes. Of the mixed solvent electrolytes we used, 1.0 mol dm(-3) LiPF6 in a mixture of EC and DMC with a ratio of 1:1, provided a high figure of merit (FOM) of 43.5 for lithium cycling efficiency with Li/LiMn1.9Co0.1O4 cells as well as a high potential of over 5 V vs. Li/Li+- and a high specific conductivity of 3.1 mS cm(-1) at -20 degrees C and 18.7 mS cm(-1) at 60 degrees C.