Hexagonal Sb Nanocrystals as High-Capacity and Long-Cycle Anode Materials for Sodium-Ion Batteries

Antimony (Sb) is regarded as a promising anode material for sodium ion batteries (SIBs) on account of its high theoretical specific capacity (∼660 mAh g^-1) and low cost. However, the large volume expansion (∼390%) during charging has inhibited its practical application. Herein, hexagonal Sb nanocrystals encapsulated by P/N-co-doped carbon nanofibers (Sb@P-N/C) were prepared using a low-cost but mass-produced electrospinning method. The as-prepared Sb@P-N/C, used as anode material for SIBs, exhibits unexpected cycling stability and rate capability, with 500.1 mAh g^-1 at 50 mA g^-1 after 200 cycles and 295.6 mAh g^-1 at 500 mA g^-1 after 400 cycles. Especially, the full battery fabricated by Na (Ni_1/3Fe_1/3Mn_1/3) O₂ || Sb@P-N/C possesses a reversible specific capacity of 66.8 mAh g^-1 at 50 mA g^-1 over 60 cycles. This simple and low-cost fabrication technology combined with unique crystal morphology offers new strategies for the advancement of sodium ion batteries (SIBs) in energy storage and electrical transportation.