N‐Doped Porous Carbon Based on Anion and Cation Storage Chemistry for High‐Energy and Power‐Density Zinc Ion Capacitor

Abstract

Zinc ion hybrid capacitors (ZIHCs) show promise for large-scale energy storage because of their low cost, highly intrinsic safety, and eco-friendliness. However, their energy density has been limited by the lack of advanced cathodes. Herein, a high-capacity cathode material named N-doped porous carbon (CFeN-2) is introduced for ZIHCs. CFeN-2, synthesized through the annealing of coal pitch with FeCl₃·6H₂O as a catalytic activator and melamine as a nitrogen source, exhibits significant N content (10.95 wt%), a large surface area (1037.66 m² g^-1), abundant lattice defects and ultrahigh microporosity. These characteristics, validated through theoretical simulations and experimental tests, enable a dual-ion energy storage mechanism involving Zn²⁺ ions and CF₃SO₃ ^- anions for CFeN-2. When used as a cathode in ZIHCs, CFeN-2 achieves a high-energy density of 142.5 W h kg^-1 and a high-power density of 9500.1 W kg^-1. Furthermore, using CFeN-2 ZIHCs demonstrate exceptional performance with 77% capacity retention and nearly 100% coulombic efficiency after 10 000 cycles at 10 A g^-1, showcasing substantially superior performance to current ZIHCs. This study offers a pathway for developing high-energy and high-power cathodes derived from coal pitch carbon for ZIHC applications.