Multi-shell tin phosphide nanospheres as high performance anode material for a sodium ion battery

Tin phosphide (Sn4P3) combined with the good conductivity of tin (Sn) and high capacity of phosphorus has been reported to be a potential anode material for the sodium ion battery (SIB). However, the preparation of Sn4P3 is limited to ball-milling and compositing with carbon materials. The novel and detailed structure of Sn4P3 itself has so far not been revealed. In this research, the multi-shell Sn4P3 nano-structure was obtained, for the first time, using a simple and general low temperature solvothermal method. The multi-shell structure with a larger specific surface area and interlayer space endows this new anode material with a short cut pathway for sodium ion diffusion and a buffer space for volume expansion during sodiation, thus avoiding electrode pulverization and improving the cycling performance of the SIB. The as-prepared multi-shell Sn4P3 delivers an excellent specific capacity of 770 mAh g−1 with capacity retention of 96% after 50 cycles at the current density of 50 mA g−1, demonstrating the superiority of structure optimization in SIB anode preparation.