The electrochemical performance of Li/graphite and LiCoO2/ graphite cells were investigated in 1 M LiPF6 dissolved in propylene carbonate (PC) + dimethyl carbonate (DMC) (Vol. 1:2) alone and with 1 wt.% vinyl acetate (VA) additive in this study. Decomposition of solvents at graphite electrode could be remarkably suppressed by addition of the VA additive in the electrolyte, leading to the improvement of electrochemical performances of the cells. We found that the VA additive should give a solid electrolyte interphase (SET) on the surface of graphite electrode, which effectively suppressed the PC decomposition in the electrolyte.