Improving the electrochemical performance of lithium-sulfur batteries by interface modification with a bifunctional electrolyte additive

Lithium-sulfur (Li-S) batteries with sulfur cathode and lithium anode are considered as a promising candidate in the next generation of high specific energy secondary batteries. However, the scalable application of Li-S batteries is limited by the unstable electrode/electrolyte interfaces. Herein, a novel bifunctional electrolyte additive, trifluoromethane sulfonamide (TFMSA), is introduced to stabilize both electrode/electrolyte interfaces to enhance the electrochemical performance of Li-S batteries. The TFMSA molecule can not only alleviate the passivation of the sulfur cathode surface, but also suppress Li dendrites growth and prevent the lithium anode from the corrosion of polysulfides. As a result, the assembled Li-S battery with TFMSA-containing electrolyte displays excellent long-cycle performance and rate capability. Moreover, the Li||Li symmetric cell using TFMSA electrolyte can stably cycle for 1200 h at 1 mA cm−2 and 1 mAh cm−2. The Li-S pouch cell with TFMSA also exhibits outstanding performance, indicating the prospect of practical application. This work sheds light on an innovative idea for interface modification via an electrolyte additive to overcome the inherent issues of Li-S batteries.