Molecular engineering of sulfur-providing materials for optimized sulfur conversion in Li-S chemistry

The practical implementation of lithium-sulfur (Li-S) batteries is greatly hampered by the low sulfur utilization and limited battery lifespan stemming from the complexity of the sulfur conversion reactions. As a core element in Li-S chemistry, the intrinsic physiochemical properties of sulfur have predominant impacts on the final battery performance, and thus rational engineering of its structure at the molecular level may provide ample possibilities to optimize the sulfur conversion behaviors and hence to promote the commercialization of Li-S technology. This review summarizes the recent advancements in tailoring the electrochemical performance of Li-S batteries through engineering the molecular structures of sulfur-providing materials themselves, such as by heteroatom doping, skeleton grafting, and construction of polysulfides-based functional intermediates. Some new-type inorganic sulfur-equivalent active molecules with beneficial electrochemical properties for cathode application are also included. Finally, the perspectives on the challenges of molecular engineering of sulfur for achieving advanced Li-S batteries are discussed.