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

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.