Chemical anchor of lithium polysulfide through sulfur copolymers for high-performance lithium-sulfur batteries

Abstract

The lithium-sulfur battery has been regarded as a potential candidate for next-generation energy storage and conversion devices due to its high energy density, high theoretical capacity, and low cost of sulfur. However, its practical applications are still restricted by the polysulfide shuttle effect and the low redox kinetics. It has been demonstrated efficiency in ameliorating the polysulfide problem by utilizing the chemical bonds to realize chemical anchor of polysulfides through the design of molecular structures of sulfur copolymers. Herein, a sulfur copolymer is developed by directly copolymerizing sulfur to 2-methylimidazole through a hydrogen abstraction. In this sulfur copolymer, not only the abundant S-N bonds strongly anchored lithium polysulfides, restricting the polysulfide transportation, but also the generated sulfur-contained chemical bonds contribute to the decrease of the lithiation barrier, accelerating the slow redox kinetics. Therefore, this sulfur copolymer reveals a high initial capacity of 952 mAh g−1 at 0.5 C, and a high capacity of 1524 mAh g−1 at 0.1 C and improved rate capacities while composite with carbon nanotubes.