• Pre-oxidation introduces oxygen functional groups that mitigate steric hindrance from aromatic rings, enabling cross-linked structures in pitch-derived hard carbon.
• Aromatic rings in asphaltene form a rigid carbon framework during carbonization, preventing ordered layer rearrangement and promoting closed pore formation.
• Asphaltene with abundant oxygen groups and large aromatic rings, pre-oxidized at 300 °C and carbonized at 1200 °C, achieves a reversible sodium storage capacity of 316.7 mAh g−1.
• The study provides a theoretical basis for selecting pitch molecular components to optimize hard carbon anodes for sodium-ion batteries.