Regulating the Microstructure of Bituminous Coal‐Based Carbon with Theabrownin to Enhance Its Plateau Sodium Storage Capacity

Abstract The inevitable graphitization of bituminous coal during carbonization suppresses its application as a carbon anode precursor for sodium‐ion batteries (SIBs). In this paper, a heterogeneous cross‐linking strategy is proposed to regulate the microstructure of bituminous coal‐based carbon. The experimental results display that the C(O)‐O structure generated by cross‐linking the oxygen‐containing groups between bituminous coal and theabrownin plays a steric hindrance effect on inhibiting long‐range ordered development of graphite microcrystals. The prepared bituminous coal‐based carbon possesses large interlayer spacing and ample closed pores. As the anode of SIBs, the as‐obtained carbon BTC‐10% releases an eminent initial reversible capacity of 290 mAh g ⁻¹ with an initial coulombic efficiency of 72.7%. Its low‐voltage (<0.1 V) plateau discharge capacity is as high as 239 mAh g ⁻¹ . In addition, a series of electrochemical measurements and carbon structure characterization reveals that the high sodium storage capacity of BTC‐10% anode mainly originates from the intercalation of Na ⁺ into the pseudo‐graphite layer and filling the closed pores in the plateau region. This work supplies an effective pathway for developing high‐performance and attractive‐cost carbon anodes of SIBs.