One-step large-scale fabrication of Bi@N-doped carbon for ultrahigh-rate and long-life sodium-ion battery anodes

Bismuth has been deemed to be the promising anode material for sodium-ion batteries on account of large volumetric capacity (3800 mAh cm−3) and high electrical conductivity. However, huge volume change during sodiation/desodiation usually causes pulverization of electrode, leading to poor rate performance and cycling stability. Herein, one-step large-scale fabrication of bismuth@N-doped carbon (Bi@C) is proposed to construct well-behaved electrode materials for sodium-ion batteries. Surprisingly, the Bi@C anode presents superior sodium storage performance, manifesting a high specific capacity (346 mAh g−1 at 0.1 A g−1), excellent rate stability (274 mAh g−1 under ultrahigh current density of 50 A g−1) and long life span (344 mAh g−1 at 1 A g−1 after cycling over 1500 times, 0.003% loss per cycle). Such excellent performances of Bi@C are attributed to the nano-sized Bi particles (~ 15 nm) encapsulated by thin carbon layer doped with N. These structural characteristics optimize the ion transfer and increase the accessible area between electrode and electrolyte, and then give a high capacitive contribution to the capacity.