Boosting Sodium-Ion Storage Performance of Sb Nanocrystals by Encapsulating Them in the Walls of Hollow Carbon Fibers and Controllable Presodiation

Antimony-based materials show high theoretical specific capacity and appropriate sodiation potential as anode materials for sodium-ion batteries, but the slow sodium-ion diffusion rate, large volume change, and low initial Coulombic efficiency hinder their practical application. Herein, we encapsulate the antimony nanocrystals uniformly in the walls of hollow carbon fibers through a pyrolysis procedure of polymeric precursors. The hollow feature of the carbon fibers not only buffers the volume variation during the sodiation/desodiation of antimony but also enhances the diffusion kinetics of sodium ions and electrolytes. The strong mechanical properties and evident charge carrier mobility of the fabric skeleton ensure that the as-prepared film of hollow carbon fibers encapsulated with antimony nanocrystals (Sb/HCNF) can serve as a self-supported anode. In addition, we developed a direct contact protocol for presodiating the Sb/HCNF, which increases the initial Coulombic efficiency from 67.3% to 97%.