Construction of hierarchical FeCo2O4@MnO2 core-shell nanostructures on carbon fibers for high-performance asymmetric supercapacitor

In this work, the novel hierarchical FeCo2O4@MnO2 core-shell nanosheet arrays have been synthesized by a facile hydrothermal method, which are grown directly on a flexible carbon fiber (CF) as an integrated electrode for supercapacitors. Scanning electron microscopy and high-resolution transmission electron microscopy measurements illustrate that MnO2 nanoflakes uniformly wrap around the surface of two-dimensional FeCo2O4 nanosheets. The electrode exhibits high areal capacitance of 4.8Fcm-2 at a current density of 1mAcm-2. Moreover, an asymmetric FeCo2O4@MnO2//active carbon (AC) cell is successfully fabricated. The asymmetric supercapacitor (ASC) displays high energy density/power density (22.68Whkg-1 at 406.01Wkg-1 and 7.06Whkg-1 at 1802.5Wkg-1), as well as excellent cycling stability with 90.1% of the initial capacitance after 5000 continuous cycles. Moreover, two ASCs connected in series can light a LED. These performances demonstrate great potential of the designed ASC in the field of energy storage due to their remarkable electrochemical properties.