Reducing Overpotential of Solid‐State Sulfide Conversion in Potassium‐Sulfur Batteries

Abstract Improving kinetics of solid‐state sulfide conversion in sulfur cathodes can enhance sulfur utilization of metal‐sulfur batteries. However, fundamental understanding of the solid‐state conversion remains to be achieved. Here, taking potassium‐sulfur batteries as a model system, we for the first time report the reducing overpotential of solid‐state sulfide conversion via the meta‐stable S 3 2− intermediates on transition metal single‐atom sulfur hosts. The catalytic sulfur host containing Cu single atoms demonstrates high capacities of 1595 and 1226 mAh g −1 at current densities of 335 and 1675 mA g −1 , respectively, with stable Coulombic efficiency of ≈100 %. Combined spectroscopic characterizations and theoretical computations reveal that the relatively weak Cu‐S bonding results in low overpotential of solid‐state sulfide conversion and high sulfur utilization. The elucidation of solid‐state sulfide conversion mechanism can direct the exploration of highly efficient metal‐sulfur batteries.