Dual Atomic Defect Modulation in Three-Dimensional Mesoporous Graphene for High-Performance Potassium Ion Hybrid Capacitors

Abstract

By combining the high energy density of potassium ion batteries (PIBs) with the fast power delivery of supercapacitors (SCs), potassium ion hybrid capacitors (PIHCs) pave the way for advanced energy storage technologies. Nevertheless, a significant challenge persists in developing electrode materials that can effectively balance the behaviors of battery-type anodes with those of capacitor-type cathodes. This study introduces three-dimensional porous graphene (NP-3DPG) doped with nitrogen and phosphorus, engineered with specific structural and electrochemical properties to overcome these limitations. The NP-3DPG material demonstrates remarkable dual functionality, serving as a large-capacity anode and a capacitance-rich cathode. The as-fabricated PIHCs achieve 167.4 W h kg−1 energy density, 72,000 W kg−1 power density, and maintain 87.3% capacity over 10,000 cycles. Extensive characterization coupled with density functional theory (DFT) analysis attributes this performance to its extensive specific surface area, interconnected porous architecture, expanded interlayer spacing, abundant redox sites, optimized electronic properties, and accelerated ion diffusion dynamics. This work emphasizes NP-3DPG as a promising electrode material for next-generation PIHCs.