Abstract
A potassium-ion hybrid system has been shown to be highly suitable for dual-mode applications as both a battery and a supercapacitor, once the issues of slow kinetics in the anode and low capacity in the cathode are addressed. In this study, we design a Potassium-ion hybrid energy storage (PIHES) system that excels in both rapid charging and high energy density. The PIHES full cells are developed using zeolitic imidazolate frameworks (ZIFs) grown on 3D graphene oxide aerogels (RGOAs). These microporous ZIFs on 3D RGOAs form a Zn-embedded hierarchical porous graphitic carbon anode material. Sub-nanometer Zn particles in the anode facilitate rapid faradaic reactions, as confirmed by operando X-ray diffraction studies combined with kinetic analysis. The hierarchical structure of the material, with its porosity and graphitization, promotes the efficient transport of ions and electrons. First-principles density functional theory calculations reveal the underlying mechanism of potassium's superior adsorption behavior on sub-nanometer Zn nanoparticles compared to other materials, resulting in high-rate capability. The Zn-embedded ZIF-derived hierarchical porous carbon (ZZHPC) offers approximately twice the capacity of pristine ZIFs. Our cathode materials are derived from the graphitic carbon production and Zn evaporation from ZIFs on 3D RGOAs, featuring N-rich microporous sites for high capacity, excellent electrolyte wettability, and mesoporous graphitic carbon channels for rapid ion and electron transport. Our potassium-ion hybrid capacitor, utilizing a ZZHPC anode and a ZIF-derived hierarchical porous carbon (ZHPC) cathode, achieves an unprecedented energy density of 207.5 Wh kg-1 and a fast-chargeable power density of 21,500 W kg-1, while maintaining nearly 100% Coulombic efficiency over 10,000 cycles.
Published Version
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