Structure Engineering of Coal Pitch-Derived Hard Carbon by Molecular Locking and Multi-Stage Pore Forming for Enhanced Sodium Storage

Pitch, featuring low cost and high aromaticity, is widely recognized as a promising precursor for cost-effective hard carbon anodes of sodium-ion batteries (SIBs). However, pitch-derived hard carbon suffers from low battery performance due to the large lateral size, narrow interlayer spacing, and deficient pores─issues caused by excessive aromatic hydrocarbon polymerization and intense π-π stacking. Herein, we report the structure engineering of pitch-derived hard carbon by molecular locking and multistage pore forming to enhance sodium storage. Spectroscopic and microcrystalline characterizations show that molecular locking between adjacent aromatic hydrocarbons─facilitated by benzoyl peroxide─suppresses pitch softening and molecular rearrangement, reducing microcrystal lateral size and expanding interlayer spacing. Real-time studies of the carbonization process reveal that the multistage pore formation synergistically utilizes the release of volatiles from aliphatic chains, Zn(NO₃)₂ decomposition, and carbon etching mediated by the ZnO intermediate. This structural engineering provides rapid ion transport pathways and abundant storage sites. Consequently, it enhances the reversible capacity from 152.18 to 344.09 mAh g^-1 and achieves a high-rate performance of 203.85 mAh g^-1 at 2 A g^-1. This work provides a structural engineering strategy to address the issues of excessive graphitization and pore deficiency associated with aromatic hydrocarbons in the preparation of high-performance hard carbon materials.