Study On Preparation And Properties Of Carbon Based Electrode Materials For MnO₂ Composite Film

Super ecapacitor is a new energy storage element between conventional capacitor and chemical power supply. It has broad prospects and has caused extensive concern of scientists around the world, because of its short charging time, less environmental pollution, high power density, wide operating temperature range, long storage life and other advantages. In this paper, carbon paper as the substrate, then deposited a layer of nanometer Mn O2(manganese dioxide) film on the carbon paper surface by redox process. In this way, a new type of composite thin film electrode materials had been prepared. The electrochemical properties of the electrode materials at the different etching time(0.5-3h) of carbon substrates and potassium ion concentration ratio(0.2-0.4 mol) at 80℃, had been systematically studied and analyzed by the constant current charge and discharge, cyclic voltammetry(CV) and AC impedance spectroscopy.(1) There was the most excellent performance for the sample of thin film electrode materials prepared at 80 ℃ of water bath, the redox ratio of the mixed solution at a concentration of 0.2 mol and reaction time of 1 hour.(2) When the deposition time was equal to 3 hours, the ratio of the concentration of a mixed solution of H2SO4 and KMn O4 was 0.2 mol(carrying amount of Mn O2 was0.0230 g m-2), nano Mn O2 electrode thin films on the substrate of the carbon paper have the highest specific capacitance of 149.5 F·g-1.(3) The AC impedance test showed that the charge transfer resistance of the four samples size order was in sequence of 0.2 mol> 0.3 mol> 0.4 mol>0.1 mol. With the formation of internal pore structure, the electrode prepared in 0.2mol was more beneficial to the charge transfer from the electrolyte to the electrode, and it had the minimum internal resistance.(4) When the deposition time was equal to 1 hour, nano MnO2 film electrode prepared on carbon paper substrate was the most stable. The attenuation of specific capacitance was 8.8%, when the scan rate increased from 10 m V/s to 5m V/s; the attenuation of specific capacitance was 22.3%, when the scan rate was increased to 20 m V/s; When the deposition time was equal to 3 hours,, the attenuation of specific capacitance was more than 50%, with the worst stability. Therefore, the deposition time was too long,which was not conducive to the stability of the electrode capacity.