Co3+ and oxygen vacancy engineering in Co3O4 electrode for high-energy hybrid supercapacitor

초록

In this work, 2D and 3D-tricobalt tetraoxide (Co3O4) nanostructures were synthesized via a hydrothermal route and used as battery-type electrodes. The effect of induced oxygen vacancy and Co3+ oxidation state in 3D-Co3O4 showed improved electrochemical performance as compared to 2D-Co3O4. Herein, a high-energy density hybrid supercapacitor (hSC) device is introduced utilizing 3D-Co3O4, with multi-walled carbon nanotubes (MWCNTs) as an electric double-layer electrode, KOH as an aqueous electrolyte, and Nickel-Foam (Ni-F) as a current-collecting substrate. The hSC exhibits a high energy density (53.65 Wh Kg−1) at 0.8 A g−1, stable performance (94.1%) over 104 cycles, and acts as a functional device. Electrochemical characterization confirms highly reversible surface and near-surface Faradaic redox charge storage, further validated by investigations using the Dunn method. While the hSC devices exhibit excellent cyclic stability, performance degradation was further analysed using thermal stability and voltage holding self-discharge tests. The hSC was further demonstrated as a functional device during red-LED illumination. Additionally, the mechanical stability of the hSC device upon bending at various angles underscores its potential as a flexible device without any loss in performance, making it uniquely suited for flexible energy storage applications. This exceptional combination of high-energy density, performance stability, and functionality as an energy device establishes Co3O4-MWCNT hSC as a promising option for a sustainable and high-efficiency energy storage system. These hSC devices are anticipated to play critical roles in emerging applications such as portable electronics, smart-grid systems, and hybrid-electric vehicles, where high energy efficiency, rapid charge-discharge capability, and long-term reliability are of utmost importance. © 2026

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