Precise Design of MOF-Derived Single Atom Catalysts with Symmetric and Asymmetric Coordination for Advanced Lithium-Sulfur Batteries

Single atom catalysts (SACs) have demonstrated great potential for ideal electrocatalytic hosts of sulfur cathode in lithium-sulfur (Li-S) batteries. The coordination microenvironments of SACs influence hugely on lithium polysulfides (LiPSs) shuttle effect and sulfur reaction kinetics. Recently, metal-organic frameworks (MOFs) have emerged as a versatile platform for the precise synthesis of SACs, stemming from the high metal loading capacity, structurally ordered porosity and atomiclevel tailorability. Many efforts have been made to create symmetric and asymmetric coordination structures in MOF-based SACs in the application of Li-S batteries, but a comprehensive summary on the catalysts design, structural evolution, and performance evaluation is still lacking. In this article, we systematically categorize the design strategies of symmetric and asymmetric coordination structures in the use of sulfur cathode hosts and their action mechanisms in reinforced Li-S batteries. We also deeply discussed the influence of coordination symmetry of SACs derived from MOFs on the adsorption energy of LiPSs and catalytic performance of sulfur conversion. To propel the development of high-performance MOFsderived SACs in Li-S batteries, the current technical challenges and proposed research directions are presented.