Enabling highly-efficient and stable potassium-ion storage by exposing atomic-dispersed super-coordinated antimony O2Sb1N4 sites on N-doped carbon nanosheets

Carbonaceous anodes hold great promise for potassium-ion batteries (PIBs), however, their electrochemical performance is still unsatisfactory to meet practical requirements due to low capacities and sluggish insertion of large K+ ions. Herein, we showcase a previously unexplored design of high-load atomic antimony coordinated with four nitrogen and two oxygen atoms (i.e., O2Sb1N4) in nitrogen-doped micropore carbon nanosheets (O-Sb-N SA@NC) for the PIB anode with markedly enhanced performance. Substantial in situ and ex situ experimental results along with theoretical computation explicitly reveal that the unique coordination environment of O2Sb1N4 sites brings fascinating features for K+ storage including abundant K+ ion storage sites, reduced K+ diffusion barrier, enhanced capability for K+ ion adsorption/desorption, while O-Sb-N SA@NC effectively alleviates volume variation and agglomeration. Accordingly, the resultant anode has demonstrated large reversible capacities (593.3 mA h g(-1), 100 cycles at 0.1 A g(-1)), high-rate capability, and extraordinary durability, outperforming most of the reported carbonaceous anodes. Notably, the assembled full cell exhibits exceptional rate capability and ultra-long lifespan (1200 cycles, 81% capacity retention at 5 A g(-1)). Our work paves the way for constructing novel single atom materials on carbon with unique coordination structures for high-performance energy storage devices.