Covalent Tethering of Ion-Pair Motifs on Waste-Derived Carbon: A Molecular Approach to Accelerated Interfacial Ion...

Sluggish interfacial lithium-ion (Li⁺) transfer kinetics at the solid-liquid interface remain a fundamental bottleneck for fast-charging carbon-based anodes. Herein, we report a molecular engineering strategy to overcome this limitation by constructing covalently tethered ion-pair motifs on hard carbon derived from industrial toluene diisocyanate residue. Diverging from traditional destructive surface treatments, we implemented a mild, site-specific nucleophilic substitution (S_N2) reaction that harnesses the intrinsic lone-pair electrons of pyridinic nitrogen sites as reactive centers. This non-destructive interfacial design preserves the structural integrity of the carbon skeleton while triggering a dramatic transition from moderate hydrophobicity to instantaneous dual super-wettability (0° contact angle) toward both aqueous and organic electrolytes. Multi-dimensional molecular evidence and Gibbs free energy analysis reveal that the motifs transform the solid-liquid boundary from a repulsive barrier (+10.51 kcal·mol^-1) into an energetic ion trap (-30.84 kcal·mol^-1). This asymmetric interface provides a thermodynamic driving force to facilitate desolvation through a selective-stabilization mechanism, which strongly captures Li⁺ ions while maintaining low affinity for solvent molecules. Consequently, the modified anode delivers a reversible capacity of ∼1150 mAh·g^-1. This work not only provides a valorization route for industrial nitrogen-rich waste but also establishes a generalizable chemoselective strategy to regulate interfacial ion flux through molecular-level surface engineering.