Stabilizing antimony nanocrystals within ultrathin carbon nanosheets for high-performance K-ion storage

Sb based anode materials have been attracted enormous attention for K-ion batteries due to its high capacity and low working potential. However, the main challenge facing Sb anode is the huge volume change (∼400%). In this work, antimony nanocrystals embedded ultrathin carbon nanosheets (Sb/CNS) are prepared through a one-step solvothermal “metathesis” reaction between ferrocene and antimony trichloride in hexane. The antimony nanocrystals with an average size of 14.0 nm are uniformly embedded into the amorphous carbon nanosheets with a layer thickness about 18.6 nm. Without adding hexane, only bulk Sb/C composite is obtained. As anode for PIBs, a high specific capacity of 288.2 mA h g^-1 and an outstanding rate capability (101.4 mA h g^-1 at 2000 mA g^-1) can be maintained. Even for 600 cycles at 200 mA g^-1, a reversible capacity of 247 mA h g^-1 (up to 90% capacity retention) is obtained. The electrochemical performance is far better than that of the bulk counterpart. It is demonstrated through a series experimental measurements that this unique structure enables the Sb/CNS composite to accommodate the volume change of Sb, promote the fast electronic/ionic diffusion, and suppress the interface reaction with electrolyte during discharge/charge procedure.