Hierarchically Tailored Porous Carbon via Precursor Engineering for Dual‐Redox Electrochemical Capacitors with Record‐High Energy Density

Abstract In energy storage systems utilizing redox reactions in the electrolyte (redox‐enhanced electrochemical capacitors; redox ECs), electrode materials play a critical role: pore size distribution, free volume, and internal surface area directly impact the adsorption and diffusion of redox‐active species at the electrode/electrolyte interface, thereby influencing overall energy storage capacity and efficiency. Importantly, achieving optimal full‐cell performance requires tailored hierarchical pore architectures capable of accommodating structurally distinct redox‐active species (catholytes and anolytes). Here, a streamlined precursor engineering strategy is presented to fabricate hierarchical, multi‐scale porous carbon structures, providing a simplified alternative to conventional acid etching or resource‐intensive pre‐treatments. The porous carbon is engineered through thermal oxidation of precursor composites at moderate temperatures, combined with precise modulation of K ₂ CO ₃ during activation. This approach yields a carbon material with a well‐balanced pore structure, featuring a micropore volume of 0.74 cm ³ g ⁻¹ and a mesopore volume of 1.64 cm ³ g ⁻¹ , and a specific surface area of 3,309 m ² g ⁻¹ . When applied in a pentyl viologen/bromide dual redox EC, this system achieves a record‐high energy density of 125 Wh kg ⁻¹ . These findings highlight the significant relationship between pore structure and redox EC performance, offering valuable insights for advanced carbon materials in energy storage systems.