Regulating Intrinsic Structure in Anthracite‐Based Hard Carbon for High Initial Coulombic Efficiency Sodium‐Ion Storage

Hard carbon (HC) is a promising anode material for sodium‐ion batteries due to its affordability, substantial sodium storage capacity, and low sodium intercalation potential. However, it suffers from low initial coulombic efficiency (ICE). Herein, an innovative acetylene‐mediated strategy is proposed to tailor the heteroatom content and pore structure of anthracite‐derived HC. During pyrolysis, hydrogen radicals from acetylene react with heteroatoms (O, N, S) in anthracite, eliminating them as gaseous species (e.g., H 2 O, NH 3 , H 2 S), while carbon radicals deposit into defects, converting open pores into closed pores. Compared to HC produced through direct anthracite carbonization, the optimized anthracite‐based HC demonstrates superior electrochemical performance, delivering a high specific capacity of 220 mAh g −1 at 0.3C with 88% ICE. Furthermore, the material exhibits exceptional cycling stability, maintaining a reversible discharge capacity of 210 mAh g −1 at 0.3C after 500 cycles. This radical‐mediated approach simultaneously mitigates irreversible Na + consumption and boosts capacity, surpassing the typical ICE limit (70%–85%) of HCs. The method provides a universal route for designing high‐performance carbon anodes from diverse precursors.