N, S co-doped coal-based hard carbon prepared by two-step carbonization and a molten salt template method for sodium storage

• N and S co-doped coal-based hard carbon (NSPC1200) was synthesized via two-step carbonization and NaCl template method, achieving high sodium storage capacity of 314.2 mAh g−1 at 20 mA g−1. • The two-step carbonization process effectively expanded interlayer spacing and adjusted carbon microcrystal structure, enhancing Na+ intercalation kinetics. • Heteroatom doping (N, S) and porous structure from NaCl template synergistically improved electronic conductivity and electrolyte accessibility, leading to excellent cycling stability (224.4 mAh g−1 after 200 cycles). • This work demonstrates a strategic approach for high-value utilization of coal in advanced energy storage, offering a promising anode material for sodium-ion batteries.