High Lithium Ion Conductivity LiF/GO Solid Electrolyte Interphase Inhibiting the Shuttle of Lithium Polysulfides in Long-Life Li-S Batteries

The "shuttle effect" that stems from the dissolution of polysulfides is the most fatal issue affecting the cycle life of lithium-sulfur (Li-S) batteries. In order to suppress the "shuttle effect," a new strategy of using a highly lithium ion conductive lithium fluoride/graphene oxide (LiF/GO) solid electrolyte interphase (SEI) to mechanically prevent the lithium dendrite breakthrough is reported. When utilized in Li-S batteries, the LiF/GO SEI coated separator demonstrates significant feature in mitigating the polysulfide shuttling as observed by in situ UV-vis spectroscopy. Moreover, the restrained " shuttle effect" can also be confirmed by analysis of electrochemical impedance spectroscopy and characterization of lithium dendrites, which indicates that no insulating layer of solid Li2S2/Li2S is found on lithium anode surface. Furthermore, the LiF/GO SEI layer puts out good lithium ion conductivity as its lithium ion diffusion coefficient reaches a high value of 1.5 x 10(-7) cm(2) s(-1). These features enable a remarkable cyclic property of 0.043% of capacity decay per cycle during 400 cycles.