Monofluorination of solvents exerts the strong polar effect on various properties. We have investigated the electrolytic properties of ethyl fluoroethyl carbonate (EFEC) and its application to a lithium battery. Conductivities of EFEC solutions are higher than those of diethyl carbonate (DEC) counterparts above 25 degrees C or below 1 mol dm(-3) of LiPF6. The anodic stability of EFEC is also higher than that of DEC. The use of EFEC as a cosolvent improves the performance of a Li/LiCoO2 coin cell.