Fabrication of Fe3O4-incorporated MnO2 nanoflowers as electrodes for enhanced asymmetric supercapacitor performance

Manganese dioxide (MnO2) is considered a promising aspirant for energy storage materials on account of its higher theoretical capacitance along with low capital cost. However, its performance is generally limited by its poor lifespan and intrinsic conductivity. In this study, MnO2-incorporated iron oxide (Fe3O4) nanoflowers were synthesized through a facile hydrothermal route and their electrochemical performance was probed. The surface composition and morphology of the as-synthesized samples were confirmed using X-ray diffraction, X-ray photoemission spectroscopy, and field emission scanning microscopy. The nanoflower-like structure and synergistic effect between the two oxides of the as-prepared MnO2@Fe3O4 nanocomposite electrode result in desirable surface area and intrinsic conductivity. Owing to its higher surface area and electrical conductivity, the MnO2@Fe3O4 nanoflower-like nanocomposite exhibits an enhanced specific capacitance (Cs) of 1651 F g-1 (1 A g-1) in a three-electrode test cell, which is two-fold higher than those of pristine Fe3O4 and MnO2. In addition, an asymmetric supercapacitor (ASC) was readily constructed by sandwiching a cellulose membrane (separator) between MnO2@Fe3O4 (cathode) and activated carbon (anode). Significantly, the ASC displayed a high Cs of 131 F g-1 (1 A g-1) along with a pretty high cycling stability of 96% over 5000 cycles at 15 A g-1 and a high energy density of 46.6 Wh kg-1 at 0.8 kW kg-1. These results demonstrate the significant potential of the MnO2@Fe3O4 nanoflower ASC device for state-of-the-art futuristic advanced energy storage applications.