The enhanced performance of lithium sulfur battery with ionic liquid-based electrolyte mixed with fluorinated ether

1,1,2,2-Tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) was selected as a co-solvent of ionic liquid for fabricating the functional electrolyte of Li-S batteries. The basic properties of the electrolyte and electrochemical performances of the cell with alterative TTE contents were intensively investigated. It is found that the fluorinated ether helps to promote ion conduction in the electrolyte, modify and stabilize SEI on Li metal, reduce charge transfer impedance, as well as restrict dissolution and shuttle of polysulfides. Consequently, high reversible capacity, good cycle, and rate capability are achieved at moderate TTE addition. The novel electrolyte guides a promising direction to construct Li-S batteries with high-energy density, long life, and high safety.