Structural regulation of coal‐derived hard carbon anode for sodium‐ion batteries via pre‐oxidation

Abstract Hard carbon (HC) is broadly recognized as an exceptionally prospective candidate for the anodes of sodium‐ion batteries (SIBs), but their practical implementation faces substantial limitations linked to precursor factors, such as reduced carbon yield and increased cost. Herein, a cost‐effective approach is proposed to prepare a coal‐derived HC anode with simple pre‐oxidation followed by a post‐carbonization process which effectively expands the d 002 layer spacing, generates closed pores and increases defect sites. Through these modifications, the resulting HC anode attains a delicate equilibrium between plateau capacity and sloping capacity, showcasing a remarkable reversible capacity of 306.3 mAh·g −1 at 0.03 A·g −1 . Furthermore, the produced HC exhibits fast reaction kinetics and exceptional rate performance, achieving a capacity of 289 mAh·g −1 at 0.1 A·g −1 , equivalent to ~ 94.5% of that at 0.03 A·g −1 . When implemented in a full cell configuration, the impressive electrochemical performance is evident, with a notable energy density of 410.6 Wh·kg −1 (based on cathode mass). In short, we provide a straightforward yet efficient method for regulating coal‐derived HC, which is crucial for the widespread use of SIBs anodes.