A fluorinated electrolyte consisting of fluorinated ether 1,1,2,2-Tetrafluoro-3-(1,1,2,2-tetrafluoroethoxy)propane (F-EPE) and 1,2-Dimethoxyethane (DME) is evaluated as a new electrolyte for Li-S batteries. The coulombic efficiency and capacity retention of Li-S batteries are significantly improved with the use of F-EPE/DME based electrolyte combing with PEO as binder. The Li-S batteries exhibit a high coulombic efficiency of similar to 96% and capacity retention of 78% after 100 cycles at 0.1C. Moreover, the F-EPE based electrolyte can work well without LiNO3 additive, thus make it possible to eliminate the safety concerns raised by the gassing reaction of LiNO3. The function mechanism of F-EPE as cosolvent was investigated by self-discharge test, polysulfide dissolution experiments, SEM and UV-Vis spectra. The enhanced electrochemical performances can be attributed to that F-EPE cannot only decrease the solubility of lithium polysulfides in electrolyte thus suppress the shuttle effect, but also take part in the formation of passivation film on lithium metal anode, indicating the positive effect of F-EPE on electrochemical properties of Li-S batteries. (C) 2018 The Electrochemical Society.