Optimization of SbBix nanoparticles embedded in ultra-thin carbon networks for enhanced sodium/potassium storage

The alloy proportions of SbBix show obvious influence on sodium/potassium storage. Herein, SbBix nanoparticles embedded in ultra-thin carbon networks (SbBix@C, x = 1, 0.5, 0.15) are successfully synthesized by a facile salt template assisted pyrolysis method. The effect of different alloy proportions on the chemical and electrochemical properties of active materials is revealed. Density functional theory calculation demonstrates that SbBi0.5 has the smallest formation energy (-5.131 eV) and the smallest volume expansion rate for both sodium/potassium storage (222%/376%). Benefiting from the optimized volume expansion for both sodium/potassium storage and carbon networks structure, the optimized SbBi0.5@C anode shows high reversible capacities of 301 mAh/g and 390 mAh/g after 100 cycles at 0.1 A/g for sodium/potassium storage, respectively. It is also observed that the SbBi0.5@C anode delivers different behaviours of sodium/potassium storage, which is due to the various composition of SEI films formed after sodium/potassium storage. It is believed that this work provides a synthetic strategy for fabricating alloy-type anode materials for SIBs/PIBs, in view of structure design and the regulation of alloy proportion.