Low concentration salt triggered in-situ asymmetric gel electrolyte for Li-S battery

Lithium-sulfur (Li-S) batteries with high specific capacity are expected to play important roles in next-generation high-energy-storage systems. However, uncontrollable shuttle effect of Li polysulfide (LiPS) and safety concerns still hinder their applications. Herein, we report an in-situ formed asymmetric gel polymer electrolyte (AGPE) fabricated through a novel and low-cost strategy. In cases of modifying the separator with Lewis acid and inducing an in-situ polymerization reaction, an enclosed catholyte chamber is constructed between sulfur cathode and separator while liquid-state electrolytes still maintain in the anode side. Experimental characterizations indicate the as-prepared AGPE could effectively prevents the shuttle effect while allowing rapidly Li+ transport property. With such AGPE, the Li symmetric cells show stable cycle performance over 1400 h cycling, and Li-S batteries exhibit a high capacity of 1090 mAh g−1 with a capacity decay rate of only ∼0.2% per cycle after 200 cycles. Besides, by combining the electrochemical measurements and the evolution of sulfur species upon cycling, the origin of enhanced cycle performance is demonstrated from the perspective of reaction kinetics in this work. Our research therefore provides a novel strategy for the electrolyte configuration and reveals a promising direction for the performance improvement of Li-S batteries.