Coal-based graphene derived from different coal ranks: exceptional sodium storage performance in sodium-ion batteries

Coal is a premium carbon material precursor as anode materials for sodium-ion batteries (SIBs). Additionally, developing anode materials with large capacity and rapid charging performance is essential for the advancement of SIBs. Consequently, in this work, coal-based reduced graphene oxide (CrGO) was prepared as an anode materials for SIBs by a modified Hummers-high temperature thermal reduction method with different ranks of coal (coal-based graphite, CG) as a precursor. The CG prepared from higher-rank coal exhibits a higher degree of graphitization, and its graphene layers are easier to exfoliate. The unique microstructure of CrGO provides stability during the sodium storage process and exhibits fast ion capacitive adsorption behavior, enhancing reaction kinetics. CrGO, with an initial reversible capacity of up to 331 mA h g^-1 at a current density of 0.03 A g^-1, achieves a specific capacity of 75 mA h g^-1, even at a high current density of 10 A g^-1. Notably, CrGO also maintains a good specific capacity of 123 mA h g^-1 after 1000 cycles at a current density of 1 A g^-1, with a capacity retention rate of 91.8%. This study highlights the potential for using coal-derived materials in the development of high-performance anode materials for SIBs, promoting the green and high-value utilization of coal.