Synergistic composite hard carbon anodes based on petroleum coke and rice husk for high-performance sodium-ion batteries

There is a great effort to find an apt anode which is low-cost, efficient, and highly stable for commercial use in sodium-ion batteries. In this work, a composite hard carbon (HC) anode was engineered by blending petroleum coke (PC)-derived soft carbon with rice husk (RH)-derived HC. The PC + RH-HC composite anode achieves superior sodium-ion storage performance due to the synergistic structural and chemical contributions of both precursors. Structural characterization confirmed that the composite inherits enlarged interlayer spacing and hierarchical porosity from RH-HC, and conductivity and structural order from PC-SC, with oxygen-rich surface functional groups and a residual silicic framework from rice husk acting as structural pillars. At 0.2C, the PC + RH anode outperforms both individual constituents, achieving long-term coulombic efficiency exceeding 98% after 500 cycles. At an accelerated rate of 5C, the anode delivers an initial capacity of ≈167 mAh g⁻¹ and retains ≈94.15% capacity over the final 1000 of 5000 cycles, demonstrating exceptional high-rate durability. These results highlight a sustainable and scalable route for developing high-power, long-life HC anodes for next-generation sodium-ion energy storage.