Conjugation-Activity Regulated Molecular Templates Enable Microcrystallite-Refined Hard Carbon for High-Performance Sodium Storage

The microcrystallite structure of carbon materials has a significant impact on their electrochemical properties, yet it usually suffers from uncontrollable aromatic ordering and thickening during carbonization. Here, we develop a conjugation-activity regulated molecular template strategy to program the microcrystallite evolution of coal-derived hard carbon toward sodium storage. By modulating conjugation capacity and bond-cleavage thresholds of aromatic N-heterocycles, we propose a molecular template design principle: strong conjugation creates supplementary microcrystallite growth sites to alter aromatic domain evolution, while molecular activity controls the effective activation range for conjugation-mediated reconstruction. N-Phenylcarbazole, which integrates a sufficiently conjugated aromatic core with a locally labile N-phenyl linkage, realizes this balance by enabling radical-mediated precursor reconstruction during pre-oxidation and constrained aromatic-layer rearrangement during carbonization. The resulting hard carbon exhibits refined and dispersed turbostratic microcrystallites with enlarged interlayer spacing and regulated defects, retaining 250.3 mAh g^-1 after 5600 cycles at 500 mA g^-1, corresponding to 83.6% capacity retention. This work establishes an activity-window-modulated conjugated-molecule design principle for programming coal-derived carbon microcrystallites.