Bismuth-Antimony Alloy Nanoparticles Embedded in 3D Hierarchical Porous Carbon Skeleton Film for Superior Sodium Storage

A composite film that features bismuth–antimony alloy nanoparticles uniformly embedded in a 3D hierarchical porous carbon skeleton is synthesized by the polyacrylonitrile-spreading method. The dissolved polystyrene is used as a soft template. The average diameter of the bismuth–antimony alloy nanoparticles is ~34.5 nm. The content of the Bi-Sb alloy has an impact on the electrochemical performance of the composite film. When the content of the bismuth–antimony alloy is 45.27%, the reversible capacity and cycling stability of the composite film are the best. Importantly, the composite film outperforms the bismuth–antimony alloy nanoparticles embedded in dense carbon film and the cube carbon nanobox in terms of specific capacity, cycling stability, and rate capability. The composite film can provide a discharge capacity of 322 mAh g(−1) after 500 cycles at 0.5 A g(−1), 292 mAh g(−1) after 500 cycles at 1 A g(−1), and 185 mAh g(−1) after 2000 cycles at 10 A g(−1). The carbon film prepared by the spreading method presents a unique integrated composite structure that significantly improves the structural stability and electronic conductivity of Bi-Sb alloy nanoparticles. The 3D hierarchical porous carbon skeleton structure further enhances electrolyte accessibility, promotes Na(+) transport, increases reaction kinetics, and buffers internal stress.