Mixed solvent electrolyte for high voltage lithium metal secondary cells

We have examined various solvents and solutes as electrolytes for high volt age lithium metal secondary cells in terms of the oxidation potential, spec ific conductivity and cycling performance of Li/LiMn1.9Co0.1O4 cells. We se lected propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonat e (DMC), diethyl carbonate (DEC), 1,2-dimethoxyethane (DME) and 1,2-diethox yethane (DEE) as the solvents, and LiClO4, LiPF6, LiAsF4 and LiBF4 as the s olutes. 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 meri t (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 co nductivity of 3.1 mS cm(-1) at -20 degrees C and 18.7 mS cm(-1) at 60 degre es C. (C) 1999 Elsevier Science Ltd. All rights reserved.