Superior sodium storage anode constructed via chemical bonding between S-doped hard carbon and graphene oxide binder

Hard carbon stands out as one of the most prospective anode materials for the storage of sodium due to its abundant resources, low cost, high conductivity, and suitable potential. In this study, S-doped hard carbon (SFC/S-3) was synthesized from a mixture of Shenfu bituminous coal (SFC) and S powder via the one-step pyrolysis method. S doping effectively enlarged the carbon layer spacing, formed -C-SO_x-C- bonds, and increased the specific surface area of the hard carbon, which significantly enhanced the sodium storage capacity of hard carbons. Furthermore, coal-based graphene oxide (CGO) was used as a multi-functional binder to further boost the sodium storage performance of SFC/S-3 by reducing the surface defects and forming a conductive network. Consequently, the SFC/S-3@CGO exhibited an excellent sodium storage performance, delivering a high reversible capacity of 449.4 mAh g⁻¹, a high-rate capacity of 224.7 mAh g⁻¹ at 1 A g⁻¹, and approximately 74% capacity retention after 500 cycles at 1 A g⁻¹. This study offers a versatile approach for heteroatom doping and promotes the clean utilization of coal.