Biomass hard carbon of high initial coulombic efficiency for sodium-ion batteries: Preparation and application

Biomass hard carbon anodes have attracted wide attention due to the advantage of low cost and renewability, but the low initial coulombic efficiency (ICE) limits their practical application in sodium-ion batteries (SIBs). In this work, a carbonization method with low heating rate was conducted to prepare biomass hard carbon materials from camphor wood residues and explore the key factors that influence the ICE. As the heating rate decreases, the as-prepared biomass hard carbon with a relatively low amount of defects displays a high ICE of 82.8% by decreasing the initial irreversible capacity loss. Specifically, when the heating rate decreases to 0.25 ℃ min−1, the obtained hard carbon exhibits the optimal electrochemical performance with the initial charge capacity of 324.6 mAh g−1 and excellent cycle stability (90.0% capacity retention after 200 cycles at 50 mA g−1). Besides, matched with Na3V2(PO4)/C cathode, the full cell exhibits a high energy density of 245.3 Wh kg−1 and stable cycling performance. This comprehensive study provides a feasible method and opens new opportunities for biomass hard carbon, and extends the strategy to design the high-performance anode materials for SIBs.