Hydrothermally synthesized aster flowers of MnCo₂O₄ for development of high-performance asymmetric coin cell supercapacitor

In this study, manganese cobaltite (MnCo₂O₄) grown on Ni-foam are deposited by hydrothermal method at different deposition times (2, 4, 6, and 8 h). The MnCo₂O₄ electrodes were systematically characterized in terms of their structural, morphological, and electrochemical properties. The cubic crystal system of MnCo₂O₄ with Fd3m space group is revealed by X-ray diffraction. A morphological evolution from nanograins towards aster-flower-like nanostructures can be seen in the field emission scanning electron microscopy images. The stoichiometry of Mn, Co, and O elements and their valance states are studied using Energy Dispersive Spectroscopy. and X-ray Photoelectron Spectroscopy respectively. An aster-flower-like nanostructure of MnCo₂O₄ (8 h), exhibits areal capacitance of 11.4 Fcm⁻², and an energy density of about 0.98 mWhcm⁻² was evaluated at 3 mAcm⁻² current density within the −0.3 to 0.5 V potential window. An asymmetric coin cell (ASCC) device demonstrated an areal capacitance of 47.4 mFcm⁻², energy density of 13.0 μWhcm⁻², and power density of about 0.525 mWcm⁻² was measured at 0.5 mAcm⁻² applied current with exceptional cyclability of 95 % measured up to 9000 cycles.