Coordination Chemistry of Single-Atom Catalysts in Expediating Kinetics for Advanced Lithium-Sulfur Batteries

The shuttling effect and sluggish conversion kinetics of lithium polysulfides (LiPSs) hinder the further advancement of lithium-sulfur (Li-S) batteries, exhibiting high barriers. Among catalysts, single-atom catalysts (SACs) can accelerate LiPSs redox kinetics by leveraging M-S coordination, interfacial charge transfer, and anchoring effect of coordinating heteroatoms. Numerous researches have reported improved catalytic activity via screening central metal and coordinating atoms as well as optimizing coordination configurations. However, systematic summary concerning the principles in screening and design of asymmetric coordination structures, the evolution mechanisms of orbital hybridization and spatial geometry, and the corresponding structure-activity relationships governing LiPSs conversion kinetics remain unknown. In this review, we systematically summarize the modifications brought by asymmetric coordination chemistry and dual-atom coordination structures in terms of geometric configuration engineering, molecular orbital hybridization, and interfacial charge rearrangement, together with the underlying mechanisms for boosting LiPSs conversion kinetics. Centered on theoretical calculations supplemented by experimental validations, we elaborate the critical significance of asymmetric coordination chemistry of SACs in elevating the catalytic efficiency. Finally, the future developments of SACs in Li─S batteries are outlooked and prospected.