Nitrogen-Doped Porous Carbon Fiber as a Self-Supporting Electrode for Boosting Zinc-Ion Hybrid Supercapacitors

Abstract

Zinc-ion hybrid supercapacitors (ZHSCs) are considered to be a promising and safe energy storage system. The design of carbon-based cathode materials is crucial to improving the performance of ZHSCs. In this work, a nitrogen-doped porous carbon fiber (NPCE) was prepared by a combination of template and etching methods, which could directly serve as the cathode for ZHSCs. The ion transfer channel was adjusted by rationally controlling the amount of ZnO template agent, which enhanced ion transfer and increased the capacitive contribution. The pyrolysis of polyacrylonitrile as carbon and nitrogen resources provided rich nitrogen functional groups for charge storage. In a 2 M ZnSO₄ electrolyte, the optimized NPCE-4 exhibited superior electrochemical performance with a capacitance of 283.9 F g^–1 at a current density of 1 mA cm^–2. The ZHSC achieved an energy density of 101 Wh kg^–1 at a power density of 457 W kg^–1, along with excellent cycle life with a capacity retention rate of 98.9% at 20 mA cm^–2 after 10 000 cycles.