The complex of ethyl viologen halides and UIO-67 as separator materials for upgrading performance of lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are considered to be the most promising energy storage system to replace lithium-ion batteries due to their ultra-high energy density. However, the shuttling of polysulfides and the growth of lithium dendrites lead to several challenges for practical use. This study, UIO-67 separator modified material coating with zwitterionic of ethyl viologen halides (EV(2+)2X(-) ,X = Cl, Br, I) is prepared by a simple onestep method. The cation (EV2+) can adsorb polysulfides through electrostatic interaction, and then promote the conversion of polysulfides. The free halogen anions contribute to the desolvation of Li+ by coordination, thereby accelerating the transport of Li+ . Among them, the UIO-67@EV(2+)2I(-) modified separator exhibits the best electrochemical performance for Li-S batteries. The capacity decay rate is 0.022 % after 800 cycles at 2C, and it still has excellent cycle stability under high sulfur loading of 5 mg cm( -2) and lean electrolyte of E/S = 3 mu L mg(-1) . This work sheds new light on the selection of modified materials for Li-S battery separators.