Facile coating of manganese oxide on tin oxide nanowires with high-performance capacitive behavior

In this paper, a very simple solution-based method is employed to coat amorphous MnO₂ onto crystalline SnO₂ nanowires grown on stainless steel substrate, which utilizes the better electronic conductivity of SnO₂ nanowires as the supporting backbone to deposit MnO₂ for supercapacitor electrodes. Cyclic voltammetry (CV) and galvanostatic charge/discharge methods have been carried out to study the capacitive properties of the SnO₂/MnO₂ composites. A specific capacitance (based on MnO₂) as high as 637 F g^-1 is obtained at a scan rate of 2 mV s^-1 (800 F g^-1 at a current density of 1 A g^-1) in 1 M Na₂SO₄ aqueous solution. The energy density and power density measured at 50 A g ^-1 are 35.4 W h kg^-1 and 25 kW kg^-1, respectively, demonstrating the good rate capability. In addition, the SnO ₂/MnO₂ composite electrode shows excellent long-term cyclic stability (less than 1.2% decrease of the specific capacitance is observed after 2000 CV cycles). The temperature-dependent capacitive behavior is also discussed. Such high-performance capacitive behavior indicates that the SnO₂/MnO₂ composite is a very promising electrode material for fabricating supercapacitors.