A Universal Strategy for Defect‐Rich Porous Carbons via Air‐Montmorillonite Assisted Carbonization Toward High‐Performance Zinc‐Ion Hybrid Capacitors

ABSTRACT The design of defect‐rich porous carbon is crucial for enhancing capacitive performance. Herein, a general strategy is proposed to construct SP 3 ─C─rich porous carbon by leveraging the flame‐retardant and activation effects of montmorillonite (MMT) during carbonization of diverse precursors in a muffle furnace. Air‐carbonized samples possess more defects than those prepared under N 2 . The defect generation follows coal‐derived precursor > polymer > biomass, attributed to their aromaticity. High‐aromaticity precursors exhibit high HOMO energy and the strong oxidation propensity. In the coal tar pitch (CTP) precursor, oxygen functional groups from air create steric hindrance, which impedes the ordered stacking of polycyclic aromatic hydrocarbons, delaying graphitization and promoting SP 3 ─C formation. HRTEM characterization is used to analyze the defects of the materials, and the gas‐phase and condensed‐phase flame retardants of MMT are identified. Meanwhile, an MMT‐PVA gel electrolyte with high ionic conductivity is prepared. The solid‐state zinc‐ion hybrid capacitor fabricated using the prepared gel electrolyte and CTP‐based porous carbon delivers outstanding specific capacity (312 mAh g −1 ) and high energy density (272.9 Wh kg −1 ). This work presents a simple and universal strategy for defect‐rich porous carbons, extendable to diverse carbon precursors for constructing high‐performance capacitor materials.