Modification And Capacitance Of Electrolytic Manganese Dioxide For Supercapacitors

In this thesis, using EMD as raw materials, modification EMD powders were prepared by the hydrothermal synthesis and doping-Al2O3after ball-milling method. The capacitance of the as-modified EMD electrode materials was systematically studied. The samples were characterized by powder X-ray diffraction(XRD), scanning electron micrsoscopy(SEM) and suface area analyzer(BET). The results showed that the as-modified EMD electrode materials were satisfy the super-capacitor application.(1) By the hydrothermal modification, the MnO2nanowire with about50nm diameter and beyond5μm length and115.58m2/g special surface area was obtained. Increasing the EMD concentration should lead to prepare the longer and thinner nanowire, and increasing the hydrothermal temperature and time should lead to prepare better crystalline quality. The complete γ-MnO2phase was prepared by hydrothermal modified at260℃for24h. The result of CV showed that the as-modified material had a perfect supercapacitor performance. The specific discharge capacitance of the samples untreated and treated were140.94F/g and176.41F/g, respectively, that is, the value increased by25.17%after treated. Long cycle life and high coulombic efficiency were also demonstrated after charge/discharge100cycles.(2) Using EMD as raw materials, MnO2used for electrode materials of super capacitor was prepared by ball-milling and doped modification. The EMD materials after and before modification were spherical γ-MnO2. The dispersibility and BET area of the as-modified MnO2were both increased. The specific capacity of EMD before modification was140F/g and while doping amount was1%(mass fraction of Al2O3), the as-treated material could attain the highest specific capacity of165F/g, and after200cycles of constant charge-discharge, the electrode was stable and its capacitance still kept more than90%.(3) By comparing to the hydrothermal synthesis method and ball-milling-doped modification method on pilot-plant test, the magnifying effect of the hydrothermal modification method was unobvious and should better suit the modification of the EMD for the supercapacitor.