A soft carbon materials with engineered composition and microstructure for sodium battery anodes

Abstract

Sodium-ion batteries (SIBs) have advantages in high sodium resources, providing powerful supplement to the current energy storage system. However, the lack of low-cost and high-performance anode materials still limits its practical application. Herein, a soft carbon anode derived from petroleum coke was successfully synthesized by engineering its composition and microstructure through resin and sodium phosphate compositing with optimal heat treatment process, delivering significant merits over existing composite anode in term of price density, initial Coulombic efficiency (ICE) and carbon yield. Resin helps to increase micropores and inhibit graphitization. Na₃PO₄ contributes to expand layer spacing and increase reversible groups, meanwhile facilitates the cross-linking of graphite microcrystalline and provides additional sodium supplement with improved ICE and conductivity. Through the synergistic effect by the additives, the optimized sample (P-ONH-1200) exhibits a superior reversible charge specific capacity of 311.9 mAh g⁻¹ with high cycling stability, ICE (90.7 %) in SIBs, and high carbon yield (70 %). It also gains rate performance of 209.7 mAh g⁻¹ at 4 C with 98 % retention after 1000 cycles. The full cell with Na₃V₂(PO₄)₃ (NVP) cathode at 1.05 N/P ratio exhibits an excellent stability with a capacity retention of 70 % after 500 cycles at 1 C. It provides a model reference for the microstructure regulation of petroleum coke and a revenue for preparation high-performance soft carbon anode for SIBs.