A Novel Zwitterionic Ionic Liquid-Based Electrolyte for More Efficient and Safer Lithium-Sulfur Batteries

The shuttle effect of polysulfide and the flammability of the conventional electrolyte are the two major obstacles restricting the development progress of lithium-sulfur batteries. Exploring highly efficient electrolyte components coupled with the conventional electrolyte is a reliable strategy to solve these issues. However, the current electrolyte components usually relieve these issues at the expense of the sacrificed electrochemical performance. Herein, a novel zwitterionic ionic liquid named as TLTFSI is reported, which exhibits a high ionic conductivity of 3.7 × 10^-3 S cm^-1, a wide electrochemical potential window from 1.51 to 4.82 V at 25 °C, and a high thermal decomposition temperature of 275 °C. The optimized TLTFSI-based electrolyte is nonflammable and performs superior electrochemical performance in terms of larger capacity, better rate capability, and longer cyclic life compared with the conventional organic electrolyte. The robust performance is attributed to the high intrinsic ionic conductivity, the suppressed polysulfide dissolution/diffusion, and the high interface compatibility toward the lithium anode of the TLTFSI-based electrolytes. This present work represents the first demonstration of the zwitterionic ionic liquid to efficiently improve the overall electrochemical performance and the safety of lithium-sulfur batteries.