C₃N₄ Template-Based N-Doped Porous Carbon Cathode for Zinc-Ion Hybrid Capacitors

Zinc-ion hybrid capacitors (ZIHCs), which combine the advantages of batteries and supercapacitors, are very competitive in the field of advanced energy storage applications. However, their performance is limited by carbon cathodes that have a low specific surface area and inferior porous structure. Here, we report a N-doped porous carbon cathode prepared by high-temperature calcination and chemical activation based on a soft C3N4 template. The as-prepared N-doped porous carbon cathode shows a hierarchical nano structure with micropores and mesopores, which can provide additional active sites for zinc-ion adsorption, reduce charge-transfer resistance, and enhance kinetic performance. The ZIHCs assembled by using this N-doped porous carbon cathode exhibits a specific capacitance of 166 mAh g–1 at a current density of 0.1 A g–1, an energy density of up to 124 Wh kg–1, and an 82.4% capacitance retention after 5000 cycles at a current density of 5 A g–1, showing a great potential for practical applications. Our work provides a way for developing high-performance zinc-ion hybrid capacitors.