Sulfur‐containing polymer cathode materials: From energy storage mechanism to energy density

Besides lithium-ion batteries, it is imperative to develop new battery energy storage system with high energy density. In conjunction with the development of Li-S batteries, emerging sulfur-containing polymers with tunable sulfur-chain length and organic groups gradually attract much attention as cathode materials. This can avoid the problems that are impeding the development of the typical Li-S batteries, such as volume expansion, active material dissolution, shuttle effect, and so on. This review aims to generalize the type of sulfur-containing polymers and the working principles in Li-S batteries. The sulfur-containing polymers (R-Sn-R) with different sulfur-chain length (n > 6, n ≤ 2, and 3 ≤ n ≤ 6) are summarized. It also discusses several organic groups such as phenyl rings, N-heterocycles, and unique structure with cross-linked networks and multi-micropores skeleton. This review also explores other strategies of sulfur-containing polymers in the rest of Li-S batteries, providing a summary of the advantages of sulfur-containing polymers, recent development, in-depth discussion of the mechanism in Li-S batteries, and organic group-structure-performance relationship. This review would have guidelines for future development of sulfur-containing polymers in Li-S batteries.