Structural engineering of N/S co-doped hard carbon anodes for enhanced potassium storage performance

Potassium-ion batteries are an attractive replacement for lithium-ion batteries due to their abundance and economic viability. Nevertheless, its practical implementation is considerably obstructed by the inadequate electrochemical performance of carbonaceous anodes. A nitrogen/sulfur co-doped hard carbon (NSHC) material is synthesized via a straightforward pyrolysis process, employing phenolic resin and trithiocyanuric acid as the carbon and dopant precursors, respectively. Comprehensive structural analysis demonstrates that the dual-heteroatom co-doping effectively enlarges the interlayer distance and introduces substantial defects, both of which promote rapid potassium-ion diffusion and improve potassium-ion storage capability. Consequently, this optimized NSHC anode delivers exceptional electrochemical performance, including a capacity of 649.5 mAh g⁻¹ at 0.1 A g⁻¹ and a capacity of 100.1 mAh g⁻¹ at 10 A g⁻¹, outperforming that of the undoped hard carbon (HC) counterpart. This work illuminates the structure-property relationship about heteroatom-doped carbon, providing a strategic framework for advanced PIB anode design.