The synergy of ferric surface anchoring and interior doping engineering enables anode with boosted potassium ion storage performances

Interfacial engineering, especially atomic substitution at the interface or inside the nanomaterials, is a promising strategy for fabricating high-performance electrode materials. Herein, an interfacial modification strategy was reported to develop cobaltous sulfide (CoS2) nanomaterials with Fe clusters modified on their interface and Fe single atoms partially substituted Co atoms in CoS2 (Fe-CFS), which were further wrapped by graphene networks, forming highly active Fe-CFS@graphene nanomaterials (Fe-CFS@C) with triple reaction interfaces. As the 1st interface, graphene can decrease their electrical resistance. At the 2nd interface, partial substitution of Co atoms in CoS2 by Fe single atoms can reduce its band gap and boost the potassium ion (K+) diffusion rate. At the 3rd interface, anchoring Fe clusters on the surface of CoS2 results in the formation of Schottky junction and promotes the formation of built-in electric fields, which accelerates the K+ insertion/extraction kinetics and depresses the dynamic polarization. Acting as anode for K+ battery, Fe-CFS@C exhibits a high reversible capacity of 755.8 mA h g-1 at 0.05 A g-1. Even at 10 A g-1, it can maintain 178.3 mA h g-1 over 4000 cycles due to the greatly enhanced electrochemical reaction kinetics and effectively improved structural stability.