Novel crystalline Bi/amorphous Bi2O3 hybrid nanoparticles embedded in N-doped carbon for high-performance lithium-ion battery anodes

In this work, novel crystalline Bi/amorphous Bi₂O₃ hybrid nanoparticles (Bi/a-Bi₂O₃) are embedded into an N-doped carbon (Bi/a-Bi₂O₃@C) by a simple ball-milling and subsequent carbonization process to stabilize the structure and enhance the conductivity of the Bi/a-Bi₂O₃ anode during lithium storage. The results confirm that in Bi/a-Bi₂O₃@C the relatively dispersed quasi-spherical Bi/a-Bi₂O₃ hybrid nanoparticles are tightly embedded within the N-doped carbon with a wrinkled surface; meanwhile, the Bi–C and Bi–O–C bonds are formed between Bi/a-Bi₂O₃ and carbon, further reinforcing the combination between Bi/a-Bi₂O₃ and carbon and enhancing the conductivity of Bi/a-Bi₂O₃@C. Moreover, the amorphous a-Bi₂O₃ with an open architecture can offer more isotropic ion transfer ways to facilitate the transport of Li⁺. These distinctive structural features endow Bi/a-Bi₂O₃@C with fast electrochemical reaction kinetics, high capacitance ratio, superior structural stability and a LiF-rich SEI layer during cycle. As a result, the Bi/a-Bi₂O₃@C reveals outstanding electrochemical performance including high capacity, good rate performance and long lifespan, with 406.7 and 154.2 mAh g⁻¹ after 460 and 1000 cycles at 200 and 2000 mA g⁻¹ (about 13 C), respectively. This work provides a new insight into the improvement of lithium storage performances of the Bi-based anodes.