Synergistic Nitrogen‐Catalytic Engineering Direct K ₂ S ₃ ‐to‐K ₂ S Conversion in High‐Performance Potassium‐Sulfur Batteries

Abstract Potassium‐sulfur (K‐S) batteries are considered a promising candidate for next‐generation energy storage due to the earth‐abundance of potassium and sulfur and their high theoretical capacities. However, their development is hindered by sluggish redox kinetics, limited mechanistic understanding of solid‐state conversion processes, and the polysulfide shuttle effect. Here, the detailed mechanism of the solid‐solid conversion stage in K‐S batteries is investigated. Conventional carbon‐based sulfur hosts follow a two‐step pathway (K 2 S 3 →K 2 S 2 →K 2 S) with a high intrinsic activation barrier, which fundamentally restricts reaction kinetics. Through first‐principles calculations, it is shown that nitrogen‐doped carbon‐particularly with pyridinic and pyrrolic nitrogen‐enables a direct one‐step conversion from K 2 S 3 to K 2 S, substantially lowering the energy barrier and enhancing K 2 S redox kinetics. Guided by this insight, a nitrogen‐doped carbon/graphene (NCG) matrix is designed with a high nitrogen content (15 wt.%) as a sulfur host. The NCG framework combines high conductivity with strong chemical affinity between nitrogen sites and sulfur species, accelerating redox reactions while suppressing polysulfide dissolution. The S/NCG‐1 cell shows a low‐capacity decay of 0.135% over 500 cycles, highlighting improved sulfur utilization and long‐term stability. This work establishes mechanistic design principles for heteroatom‐doped carbon cathodes and advances the rational development of high‐performance K‐S battery systems.