Efficiently\nDesigned Three-Dimensional Architecture\nof CoMn<sub>2</sub>O<sub>4</sub> Decorated V<sub>2</sub>CT<sub><i>x</i></sub> MXene for Asymmetric Supercapacitors

The structure, morphology, stoichiometry,\nand chemical characterization\nof the V<sub>2</sub>CT<sub><i>x</i></sub> MXene, CoMn<sub>2</sub>O<sub>4</sub>, and V<sub>2</sub>C@CoMn<sub>2</sub>O<sub>4</sub> nanocomposite, prepared by using a soft template method, have been\nstudied. The electron microscopy studies reveal that the V<sub>2</sub>C@CoMn<sub>2</sub>O<sub>4</sub> composite incorporates mesoporous\nspheres of CoMn<sub>2</sub>O<sub>4</sub> within the 2D layered structure\nof MXene. The specific capacitance of the composite electrode is ∼570\nF g<sup>–1</sup> at 1 A g<sup>–1</sup>, which is significantly\nhigher than that of the sum of the individual components. It also\nexhibits great rate capability and a Coulombic efficiency of ∼96.5%\nover 10000 cycles. An asymmetric supercapacitor prototype created\nwith V<sub>2</sub>C@CoMn<sub>2</sub>O<sub>4</sub>//activated carbon\noutperformed other reported ASCs in terms of achieving a high energy\ndensity of 62 Wh kg<sup>–1</sup> at a power density of 440\nW kg<sup>–1</sup>. The improved response of V<sub>2</sub>C@CoMn<sub>2</sub>O<sub>4</sub> and ASC is attributed to the enhanced active\narea available for charge transfer and the synergistic interaction\nbetween CoMn<sub>2</sub>O<sub>4</sub> spherical particles and nanolayered\nMXene. Supporting density functional theory (DFT) calculations are\nperformed to understand the impact of composite heterojunction formation\non its detailed electronic structure. Our atomistic simulations reveal\nthat by incorporating CoMn<sub>2</sub>O<sub>4</sub> in V<sub>2</sub>C, the density of electronic states at the Fermi level increases,\nboosting the charge transfer characteristics. These modifications\nin turn enhance the charge storage capabilities of heterojunction.\nFinally, the merits of the V<sub>2</sub>C@CoMn<sub>2</sub>O<sub>4</sub> composite electrode are discussed by comparing it with those of\nother existing high-performance MXene-based composite electrodes.