Mechanochemical regulation of microcrystalline in coal-derived disordered carbon for improved sodium storage: Metamorphic grade

Coals are common precursors of the disordered carbon anodes for sodium ion batteries. In order to hinder the long-range ordered development of coal precursors during thermal conversion, the acid reagents and calcination under air atmosphere have been adopted in the pre-oxidation procedure, not in accordance with the demand of green energy storage. Herein, the mechanochemical pretreatment was employed to break the aromatic structures and generate the edge defects and oxygen functional groups on the coal surface, which would suppress the long-range ordered tendency and promote the introduction of nitrogen heteroatoms during following calcination. With the increasing metamorphic grades, the molecular rigidity of coal precursors increases owing to more highly polycondensed aromatic structures and less interior buffer space. The aromatic structures in the highest-ranked anthracite are broken most heavily during the mechanochemical process. Thus the nitrogen-doped anthracite-based carbon materials have the most disordered carbon structures and deliver a high reversible capacity of 323 mA h g−1 under 0.03 A/g after 90 cycles. This work provides a facile and green solution to fabricate the highly disordered carbon anodes with low cost and high performance from the industrial raw materials.