Research On Supercapacitor Electrodes Of Hierarchically Manganese Oxide Nanostructures

Transition-oxides have been the focus of good supercapacitor materials, mangansese oxide, because of its low cost, large potential window, theoretical good performance, environmental friendly, has become most of researchers’ target.In this paper, co-precipotation and hydrothermal methods were utilized to synthesize MnO2with different crystalline and compound materials of MnO2and carbon nanotubes (CNTs) were prepared by co-precipotation methods. The morphology and structure of the products were characterized by XRD, SEM, and TG-DTA. Cyclic voltammetry (CV), AC impedence, and galvammetry charge-discharge tests were used to investigate the electrochemical performance of electrode materials. The main study work and results are as follows:Based on the ion response equation of3Mn2++2Mn7+�'5MnO2, controlling the reaction temperature, reaction time and additive, amorphous, β-, γ-MnO2and γ-MnOOH have been synthesized by coprecipotating and hydrothermal methods. The experimental results show that the electrochemical properties of MnO2with different crystalline are quite different, at the current density of50mA/g, the maximum specific capacitance ofγ-MnO2、γ-MnOOH、amorphous MnO2and β-MnO2achieved237F/g、215F/g、149F/g and28F/g, respectively the performance of γ-MnO2is optimal.γ-MnO2/β-MnO2were attained by γ-MnO2heated at220℃, and, at the current density of100mA/g, the maximum specific capacitance achieved218F/g, which is higher than γ-MnO2with specific capacitance of184F/g. However the cycle stability of γ-MnO2is better than γ-MnO2/β-MnO2and their specific capacitance attenuated11%and17%after20cycle times.CNTs were activated by different methods, the experimental results show that CNTs were actived better by ultrasonic2h with30%H2O2, and the cycle stability of composite materials were improved. The composites of γ-MnO2/CNTs were prepared by co-precipotation methods, while CNTs were active by30%H2O2. The effert of the percentage of the CNTs on the specific capacitance of composites were studied. The results show that when the percentage of the CNTs achived20%, the specific capacitance achived281F/g, at the current density of100mA/g. And its specific capacitance attenuated to190F/g after60cycle times.