Design and Synthesis of Multi-Functional Polymeric Binders for High-Performance Lithium-Sulfur Batteries Based on Ring Opening Polymerization of Thiolactone

Comprehensive Summary The application of high-performance lithium-sulfur (Li-S) batteries is severely influenced by the "shuttle effect" of polysulfides and the volume change of sulfur cathode. Herein, two different polymeric binders SOT-A and SOT-C with three-dimensional network structure containing polar groups (sulfhydryl groups, amide groups and amino groups) are synthesized by the nucleophilic ring-opening polymerization (ROP) of thiolactone with amino groups. The network structure formed by hydrogen bonds and functional groups can resist the volume change of the cathode. The sulfhydryl groups and the S-S bond formed by oxidative dehydrogenation of sulfhydryl group participate in the charge and discharge process of the battery as active materials, which improves the discharge specific capacity of the battery. Polar functional groups have strong chemisorption on polysulfides and effectively inhibit the "shuttle effect". The electrochemical performances of Li-S batteries containing SOT-A and SOT-C binders are significantly enhanced. At 1 C rate, the batteries achieve initial discharge specific capacity of 871 and 837 mAh.g(-1), respectively, and have 83.9% and 62.5% capacity retention after 500 cycles.