Enhancing Sodium Storage Performance by Regulating the Microstructure of Coal-Based Hard Carbon through the Boudouard Reaction

Abstract Coal-based hard carbon is a low-cost and industrially promising anode material for sodium-ion batteries (SIBs), yet the highly ordered structure generated from coal precursors after high-temperature carbonization severely degrades its electrochemical performance. Herein, an efficient microstructure modulation strategy is developed to restrict the formation of ordered carbon domains. Using high-fixed-carbon anthracite as the raw material, the Boudouard reaction is adopted to etch the carbon framework, creating abundant defects and nanopores. This approach inhibits microcrystal growth, enlarges interlayer spacing, induces more pseudo-graphitic structures, and optimizes nanopore distribution. The optimized THCO2-1300 electrode balances slope and plateau capacities, delivering a remarkable reversible capacity of 285.8 mAh g–1 at 25 mA g–1 and a high initial Coulombic efficiency of 73.9%. Furthermore, the assembled Na3V2(PO4)2O2F//THCO2-1300 full cell can still achieve a high energy density of 195.2 Wh kg–1 even at the highest power density of 8740.4 W kg–1. This work provides new insights into the microstructure regulation of coal-based hard carbon materials, which is expected to accelerate the practical application of low-cost, high-performance hard carbon in advanced SIBs.