Pitch-starch derived composite hard carbon with high initial coulombic efficiency and excellent cycling stability for sodium-ion batteries
摘要
In this study, a high-performance hard carbon composite was synthesized for sodium-ion battery anodes using pitch-modified corn starch. Through a co-carbonization approach involving pre-oxidized pitch and corn starch, the expansion and foaming typically observed during starch pyrolysis were effectively mitigated, leading to a notable decrease in specific surface area to 4.33 m2 g⁻1 at 1400 °C. The molten pitch served as a filler to establish a pre-sodiated interface, resulting in a high initial Coulombic efficiency of 95.47%. Optimization of the pyrolysis temperature to 1400 °C yielded a composite with increased interlayer spacing (3.811 Å), a partially graphitized structure, and a high abundance of oxygen-containing functional groups. These characteristics collectively enhanced sodium storage performance, achieving a remarkable reversible capacity of 391.6 mAh g⁻1. Furthermore, the composite exhibited excellent cycling stability (89.4% capacity retention after 500 cycles at 300 mA g⁻1) and exceptional rate capability (289.8 mAh g⁻1 at 1500 mA g⁻1). These improvements can be attributed to the mechanical reinforcement from the pitch coating, the optimized porous structure, and the enhanced electronic conductivity facilitated by the developed graphitic microdomains. This research presents a scalable and sustainable method for fabricating cost-effective biomass-derived carbon anodes, offering valuable insights for advancing next-generation high-performance sodium-ion batteries.