Synthesis of carbon coated Bi₂O₃ nanocomposite anode for sodium-ion batteries

Bi₂O₃ is a promising sodium storage material due to its high gravimetric specific capacity. However, Bi₂O₃ possesses lower electrochemical performance due to its poor electrical conductivity and structural integrity during Na⁺ insertion/extraction process. Here, we prepared a carbon coated Bi₂O₃ nanocomposite by a redox reaction and a carbon coating process. In this nanocomposite, the carbon layer can avoid the direct contact between Bi₂O₃ and electrolyte, which inhibits the repeated formation and decomposition of solid electrolyte interface film. Additionally, the carbon layer can enhance the electrical conductivity of Bi₂O₃ and suppress its aggregation due to its volume change during charge and discharge process. In addition, nano-sized Bi₂O₃ can reduce the transport distance of Na⁺ and electron. The nanocomposite shows excellent cycling performance and rate capability as anode for sodium-ion batteries. A high capacity of 421 mAh g⁻¹ can be maintained after 100 cycles at 1500 mA g⁻¹ and 392 mAh g⁻¹ can be shown at 3200 mAh g⁻¹.