Three dimensional FeCo2O4@MnO(2 )core-shell nanocomposites for integrated solid-state asymmetric supercapacitors

Three dimensional FeCo2O4@MnO2 core-shell nanocomposites with a unique spherical structure were prepared on nickel foam by a two-step hydrothermal + annealing method and they show the specific area capacitance 4.2 F/cm2 at a current density of 2 mA/cm2, which is nearly four times higher than that of a single FeCo2O4 electrode (1.1 F/cm2). The assembled FeCo2O4@MnO2//active carbon solid-state asymmetric supercapacitor (ASC) has a specific area capacitance of 1.81 F/cm2, an energy density of 54.3 Wh/kg and a power density of 769.6 W/kg at 10 mA/cm2. The solid-state ASC exhibited an initial capacitance retention of 62.4% after 7000 cycles, demonstrating good cycling stability. Especially, the integrated solid-state asymmetric supercapacitors based on FeCo2O4@MnO2 electrode material were constructed in different connected manners. The series supercapacitor devices demonstrated the typical enhancement of the operating voltage window and the parallel devices significantly improved the capacitance. Therefore, the FeCo2O4@MnO2 electrode material exhibited the outstanding electrochemical performances in solid-state supercapacitors and promising practical application prospects in integrated circuits for energy storage.