Effect of cations in ionic liquids on the electrochemical performance of lithium-sulfur batteries

Lithium-sulfur (Li-S) battery is a promising choice for the next generation of high-energy rechargeable batteries, but its application is impeded by the high dissolution of the polysulfides in commonly used organic electrolyte. Room temperature ionic liquids (RTILs) have been considered as appealing candidates for the electrolytes in Li-S batteries. We investigated the effect of cations in RTILs on the electrochemical performance for Li-S batteries. Ex situ investigation of lithium anode for Li-S batteries indicates that during the discharge/charge process the RTIL with N-methyl-N-propylpyrrolidine cations (P13) can effectively suppress the dissolution of the polysulfides, whereas the RTIL with 1-methyl-3-propyl imidazolium cation (PMIM) barely alleviates the shuttling problem. With 0.5 mol L−1 LiTFSI/P13TFSI as the electrolyte of Li-S battery, the ketjen black/sulfur cathode material exhibits high capacity and remarkable cycling stability, which promise the application of the P13-based RTILs in Li-S batteries.