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

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