Unleashing the potential of binder-free manganese cobalt oxide films for high performance asymmetric supercapacitor application

Abstract

In the present study, a vertical hydrothermal reactor is used to deposit MnCo₂O₄ (MCO) nanoflakes on Ni-foam at different reaction time. The deposited MCO films are studied by a series of different characterizations. The polycrystalline nature of MCO films is observed through XRD and HR-TEM analysis, while the FT-IR study has confirmed the functional bonding in MCO samples. The distribution of elements and their oxidation state in MCO films are analyzed by EDAX mapping and XPS study. The growth of the nanoflake structure on the Ni-foam is observed by SEM and TEM analysis. It is observed that the MCO film deposited at 6 h reaction time exhibited better structural and morphological properties. Further, the highest surface area of 37 m²/g with a mesoporous nature is exhibited by the MCO-3 sample. Interestingly, MCO-3 film exhibits better structural stability and mesoporous characteristics, as evidenced by its maximum specific capacitance at 1 mA/cm² of 738 F/g. Additionally, MCO-3 film has shown a good cycling stability of 94.2 % over 5000 cycles. Promising performance metrics, including a specific energy density of 35.7 Wh/kg and a power density of 208.3 W/kg, are exhibited by the fabricated asymmetric device. Notably, excellent cycling stability is demonstrated by the device, with 91.6 % of its initial capacitance retained after 5000 cycles while maintaining a high Coulombic efficiency at 95.4 %. These outcomes underscore the significant potential of MnCo₂O₄-based binder-less films for advance supercapacitors.