Suppression of electrochemical decomposition of propylene carbonate at a graphite anode in lithium-ion cells

The decomposition of propylene carbonate (PC) at a graphite anode in lithium-ion cells is suppressed remarkably by choosing a proper mixing ratio of PC with co-existing solvents. For example, the decomposition of PC is essentially inhibited using PC-diethyl carbonate (DEC), PC-methylethyl carbonate (MEC) or PC-dimethyl carbonate (DMC) with 1:4 (v/v) mixed solvent solution containing a volume % of PC of less than 25%. Conductivity measurements show that all PC molecules can be solvated to Li+ ions as Li(PC)2 in these mixed solvents, where 1.0 M LiPF6 and 25 vol. % of PC are used. This suggests that the solvated PC molecules are not decomposed at graphite anode.