Efficiently Designed Three-Dimensional Architecture of CoMn₂O₄ Decorated V₂CT_<i>x</i> MXene for Asymmetric Supercapacitors

The structure, morphology, stoichiometry, and chemical characterization of the V₂CT_<i>x</i> MXene, CoMn₂O₄, and V₂C@CoMn₂O₄ nanocomposite, prepared by using a soft template method, have been studied. The electron microscopy studies reveal that the V₂C@CoMn₂O₄ composite incorporates mesoporous spheres of CoMn₂O₄ within the 2D layered structure of MXene. The specific capacitance of the composite electrode is ∼570 F g^-1 at 1 A g^-1, which is significantly higher than that of the sum of the individual components. It also exhibits great rate capability and a Coulombic efficiency of ∼96.5% over 10000 cycles. An asymmetric supercapacitor prototype created with V₂C@CoMn₂O₄//activated carbon outperformed other reported ASCs in terms of achieving a high energy density of 62 Wh kg^-1 at a power density of 440 W kg^-1. The improved response of V₂C@CoMn₂O₄ and ASC is attributed to the enhanced active area available for charge transfer and the synergistic interaction between CoMn₂O₄ spherical particles and nanolayered MXene. Supporting density functional theory (DFT) calculations are performed to understand the impact of composite heterojunction formation on its detailed electronic structure. Our atomistic simulations reveal that by incorporating CoMn₂O₄ in V₂C, the density of electronic states at the Fermi level increases, boosting the charge transfer characteristics. These modifications in turn enhance the charge storage capabilities of heterojunction. Finally, the merits of the V₂C@CoMn₂O₄ composite electrode are discussed by comparing it with those of other existing high-performance MXene-based composite electrodes.