Study On Preparation And Electrochemical Properties Of Nano-porous Manganese Dioxide Composites Electrode

Manganese dioxide（MnO₂） as supercapacitor electrode materials has many advantages such as high theoretical capacitance, low cost and environmental friendliness and so on. However, the capacitive characteristics of high energy density for supercapacitor materials is ultimately limited by its poor effective utilization and electrical conductivity. The coupling technique of electrodeposition and lattice doping was used to prepare the vanadium and iron（V+Fe） co-doped MnO₂ oxide film electrode on the Titanium plate with a interlayer of IrO₂, as well as the MnO₂ and manganese-vanadium-iron（MnVFe） oxide film on the carbon fiber paper（CFP） with or without a interlayer of SnO₂+Sb₂O₃. Meanwhile, the surface morphology, phase structure and electrochemical properties of the nano-composite electrodes were characterized by X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS）,field emission scanning electron microscopy（FESEM）, transmission electron microscopy（TEM） and the electrochemical test.The results showed that the MnVFe nano-composite oxide on the highly conductive IrO₂ nano-wedges grown on the Titanium plate consist of the lamellar structure that is composed of γ-MnO₂ nanocrystallites（1-5nm）. The pore in the MnVFe oxide is composed of dominant micropores, partial mesopores and small amounts of macropores. The MnVFe oxide film electrode prepared at a current density of 25 m A cm-2possesses an average pore diameter of 2.19 nm, a pore volume of 0.160 cm3 g-1 and a specific surface area of 291 m2 g-1. The specific capacitance of the Ti/IrO₂/MnVFe oxide nano-composite electrode declines from 426.3 Fg-1 to 314.4Fg-1with a relatively limited loss of 26% when the galvanostatic（GV）charging-discharging rate is increased from 0.2 Ag-1 to 5 Ag-1. Meanwhile, it retains93.6% of the initial specific capacitance after 10000 charge/discharge cycles at a charge-discharge current density of 10 Ag-1, showing an excellent cyclical stability.When the galvanostatic（GV） charging-discharging rate is increased from 0.2 Ag-1 to 5 Ag-1, specific capacitance of the CFP/MnVFe oxide nano-composite electrode declines from 425 Fg-1（1062.5 m F cm-2） to 85.6 Fg-1（214.1 m F cm-2） with a capacitance loss of 80%. Similarly, specific capacitance of the CFP/SnO₂+Sb₂O₃/MnVFe oxide nano-composite electrode declines from 261.25 Fg-1（653.1 m F cm-2） to 100 Fg-1（250 m F cm-2） with a capacitance loss of 60%. Although,the nano-composite oxide electrodes grown on the CFP have a poor capacitance retention under high current densities, it still maintains a high areal capacitances.With increasing deposition time, the loading amount of MnVFe oxide on the CFP increased, the utilization rate of MnVFe oxide and specific capacitance of the nano-composite electrode decreased.