We report a new carbonate electrolyte of 1 M LiFSI dissolved in the EMC/FEC (70/30, v/v) solvent for lithium metal based batteries. Favorable LiF-rich SEI layer is formed on Li anode to suppress side reactions under the synergistic effect of LiFSI and FEC. Thus, the dendrite-free Li morphology and high Coulombic efficiency for Li plating/stripping can be obtained with improved cycle stability compared with conventional LiPF6/EC-DMC electrolyte. Li | S@pPAN cell assembled with the new electrolyte shows quite low lithium ion transfer resistance, excellent long cycle stability and rate performance. A high discharge capacity of 1270 mAh g−1 remains after 1000 cycles at 2 C, with an inappreciable capacity decay of 0.0015% per cycle. Due to the low interface impedance and high Li+ diffusion coefficient, a capacity of 1210 mAh g−1 even at 10 C can be maintained. This deliberately designed electrolyte offers new insights into the understanding of interfacial stability between electrolyte and Li anode. Furthermore, our work offers a new approach towards high energy-density and high rate Li-S battery.