High performance advanced asymmetric supercapacitor based on ultrathin and mesoporous MnCo^sub 2^O^sub 4.5^-NiCo^sub 2^O^sub 4^ hybrid and iron oxide decorated reduced graphene oxide electrode materials

Herein, we demonstrate a facile fabrication of nickel cobalt oxide nanoflake decorated manganese cobalt oxide nanostick-arrays (MnCo2O4.5-NiCo2O4), as a hybrid electrode material through multistep hydrothermal protocols for high performance power device applications. Iron oxide nanoparticles decorated reduced graphene oxide (Fe-rGO) was synthesized through a simplistic reduction process of GO. The morphological features, specific surface areas and morphology dependent electrochemical activity of the as-prepared electrode materials have been investigated systematically. Our as-prepared manganese cobalt oxide/nickel cobalt oxide, MnCo2O4.5-NiCo2O4 (abbreviated as MCO/NCO) hybrid electrode reveals a highest specific capacitance (Cs) value of ∼2506 F g−1 as compared to the base MnCo2O4.5 (∼1220 F g−1) at 1 A g−1 constant current density. The higher Cs values of the hybrid composite can be credited to the synergistic property of MCO and NCO, which eventually facilitates electron transportation. In contrast, Fe-rGO shows a Cs value of ∼236 F g−1 at 1 A g−1. Moreover, an advanced asymmetric supercapacitor (ASC) device was fabricated utilizing MCO/NCO as positive and Fe-rGO as a negative electrode in presence of a potassium hydroxide (KOH) soaked laboratory Whatman 40 filter paper as separator. The device exhibits a Cs value of 170.8 F g−1 at 1 A g−1 together with a decent energy density of ∼34 Wh kg−1 (power density of 597.18 W kg−1 at 1 A g−1) and a longtime cyclic stability (90% Cs retention after 3000 Galvanostatic charge-discharge series). These results suggest superior application potential of our ASC for next -generation portable energy storage applications.