Facile one-pot synthesis of bismuth microspheres@N-doped porous carbon composite anodes for high power density and ultralong-life sodium-ion batteries

Bismuth microspheres@N-doped porous carbon anode (Bi@NPC-2) is rational designed and successfully prepared by an easy one-pot heat treatment process. The composite demonstrated superior sodium storage performance, including excellent cyclic stability of 326.4 mAh g⁻¹ after 4000 cycles at 5 A g⁻¹ with a capacity retention of 95% and ultra-high rate capability of 286.7 mAh g⁻¹ at a high current rate of 40 A g⁻¹. This excellent performance is mainly due to the unique material design, the three-dimensional porous structure not only helps to mitigate the volume expansion of bismuth, but also shortens the diffusion path of sodium ions. In addition, nitrogen doping improves the conductivity of the electrode and provides more active sites for sodium storage. More importantly, the preparation process is simple, and the raw materials used are cheap, thus the Bismuth microspheres@N-doped porous carbon composite shows important practical large-scale applications. This one-step sintering method can also be applied to other alloy-based sodium storage materials.