Study on Tin-Cobalt Bimetallic Phosphide Nanoparticles as a Negative Electrode of Sodium-Ion Batteries.

Tin phosphide (SnP) holds great promise because sodium-ion batteries use this material as an anode with impressive theoretical capacity. In this paper, it is reported that Co-doped SnP is embedded into carbon-based materials and SnCoP/C with a porous skeleton is prepared. As a result, SnCoP/C-2, as the material utilized in sodium-ion battery anodes, exhibits reversible capacities at 415.6, 345.9, and 315.6 mAh g at current intensities of 0.5, 1.0, and 2.0 A g, respectively. The electrochemical reversibility, cycle stability, and rate performance of SnCoP/C samples are obviously better than those of SnP/C. Cobalt in SnCoP/C stabilizes the conductive matrix of tin phosphide and promotes the diffusion kinetics of sodium. These results show that, with an appropriate amount of cobalt doping, highly dispersed nanoparticles can be formed in the tin phosphide matrix, which can significantly enhance the cycle stability of tin-based electrode materials.