Coordination Regulation Strategy in Fabricating Bi₂S₃@CNFs Composites with Uniform Dispersion for Robust Sodium Storage

To solve large volume change and low conductivity of Bi₂S₃-based anodes, a coordination regulation strategy is proposed to prepare Bi₂S₃ nanoparticles dispersed in carbon fiber (Bi₂S₃@CNF) composites. It has been discovered that introducing trimesic acid as a ligand can significantly improve the loading and dispersion of Bi³⁺ in polyacrylonitrile fibers. The results exhibit that Bi₂S₃ nanoparticles of 200-300 nm are uniformly anchored on the superficial surface layer of CNFs, and Bi₂S₃ nanoparticles of about 20 nm are evenly dispersed in the interior of CNFs. Assessed as sodium-ion batteries' anode material, the discharge capacity of the Bi₂S₃@CNF anode in the second cycle is 669.3 mAh g^-1 at 0.1 A g^-1 and still retains 620.2 mAh g^-1 after 100 cycles, with the capacity retention rate of 92.7%. Even at 0.5 A g^-1, the specific capacity of the second cycle is 432.99 mAh g^-1, which still keeps 400.9 mAh g^-1 after 800 cycles, with a retention rate of 92.5%. The excellent cycle stability is mainly attributed to the uniform distribution of small Bi₂S₃ nanoparticles in CNFs providing abundant active sites, preventing side reactions, relieving volume expansion, improving the electrical conductivity, and accelerating the electrochemical reaction kinetics.