Efficiently Preparing of High‐Rate Coal‐Based Hard Carbon Anodes via Plasma Pre‐Oxidation

ABSTRACT Coal emerges as an exceptional candidate for hard carbon precursors, attributed to its three‐dimensional (3D) structure and high carbon yield. Nevertheless, abundant aromatic rings in coal tend to form a highly ordered graphitic structure after high‐temperature carbonization, which hinders sodium‐ion (Na+) storage. Herein, glow discharge plasma is employed to effectively introduce oxygen‐containing groups into coal effectively, facilitating the formation of a cross‐linked structure, which is subsequently subjected to high‐temperature carbonization to obtain structurally optimized coal‐based hard carbon (HC). Compared with the traditional pre‐oxidation method, the surface chemical composition and microstructure of coal‐based HC (OCHC20) obtained after carbonized are effectively modified by oxygen plasma treatment. The OCHC20 exhibits a remarkable initial Coulombic efficiency (ICE) of 89.3% and a reversible capacity of 302 mAh g – 1 at 0.05 A g −1 , which is higher than the 263 mAh g −1 reversible capacity of hard carbon (OCHC) prepared by traditional pre‐oxidation. Particularly, OCHC20 displays superior rate performance with a capacity of 238 mAh g −1 at 5 A g −1 , representing a 22.7% increase over OCHC (194 mAh g −1 ). This study demonstrates the potential of plasma technology in the rational design of carbon‐based anodes for high‐performance sodium‐ion batteries (SIBs).