Fundamental, application and opportunities of single atom catalysts for Li-S batteries

Li-S batteries are regarded as promising energy storage devices for future electric vehicles (EVs) due to the advantages of high energy density and low cost. However, their practical application is still seriously limited by the sluggish conversion reactions of lithium polysulfides (LiPSs) and the shuttle effect. Exploring efficient catalysts for promoting the conversion reactions of LiPSs is a valid strategy for increasing the utilization of active material, and eliminating the LiPSs shuttle effect. Recently, single atom catalyst (SAC) become a new frontier and a hot topic in electrocatalysis because of its 100% atomic utilization efficiency, superior catalytic activity and selectivity, and tunable structures. These advanced properties endow SAC a great potential in Li-S batteries. In this review, the mechanism of SACs in catalyzing LiPSs conversion reactions will be discussed. The detailed structures and their influence on the catalytic performances of SACs will be summarized. The practical applications of SACs in the composite cathode, separator/interlayer, lithium anode engineering layer, electrolyte additives, etc. in Li-S batteries will be illustrated. Finally, the perspectives and future research focus of SACs for Li-S batteries are proposed. This review aims to comprehensively summarize the fundamentals and the development of SACs for Li-S batteries, to inspire more novel ideas for designing high performance SACs, and to better understand their mechanism.