Integrated DES-Mediated Extraction and In Situ Polymerization Toward Coal Tar Phenolic-Derived Defective Porous Carbon for High-Energy-Density Zinc-Ion Hybrid Capacitors

This work establishes a facile and integrated strategy combining deep eutectic solvent (DES) selective extraction and in situ polymerization to upcycle low-value coal tar phenolics into high-performance defective porous carbon for zinc-ion hybrid capacitors (ZIHCs). Benefiting from strong hydrogen-bonding interaction, aldehyde-functionalized DES achieves efficient separation of phenolic components from coal tar with an extraction efficiency up to 94.73%. Eliminating tedious back-extraction procedures, the phenolic-enriched system realizes pH-regulated in situ polymerization to fabricate three types of phenolic resin precursors with distinct molecular architectures. The three-dimensional, oxygen-rich precursor formed under alkaline conditions induces steric hindrance that suppresses aromatic stacking during carbonization, yielding highly defective porous carbon. Combined with rational activation treatment, all derived carbon materials exhibit well-developed pore structures and favorable capacitive performance. Notably, the extraction phase is innovatively reused to fabricate a highly conductive gel electrolyte. The assembled ZIHC using prepared porous carbon and gel electrolyte achieves a favorable specific capacity of 257.9 mAh g −1 , a high energy density of 186.9 Wh kg −1 , and ultra-long cycling durability. This study clarifies the intrinsic correlation between precursor microstructure, carbon defect configuration and electrochemical energy storage behavior, and provides a new strategy for high-value sustainable utilization of coal tar toward advanced energy storage devices. Graphical An integrated “extraction-polymerization-carbonization” strategy is developed to convert coal tar phenolics into porous carbon. pH-controlled phenolic polymerization affords three kinds of precursors. The precursor from alkaline polymerization suppresses graphitization, generating highly defective porous carbon, which enables the assembled ZIHC to achieve high specific capacity and superior energy density.