Preparation And Characterization Of Manganese Dioxide Electrode Material For Supercapacitor

Manganese dioxide as electrode materials for supercapacitor has similar capacitance characteristics with RuO2. Manganese dioxide is taken seriouly more and more due to its abundant resource, its low cost and environmental friendly, etc. There are many methods to prepare manganese dioxide. However, most of the preparation conditions are rigor, and the conditions are limited by temperature and pressure. In this paper, we adopt a simple liquid precipitation method to prepare nano manganese oxide electrode material. There is no need high pressure and high temperature in this method. MnO2are characterized by X-Ray diffraction (XRD), Scanning Electron Microscope (SEM), cyclic voltammetry and constant current charge-discharge.We study the effect of CMC and the heating treatment on physical and electrochemical performance of MnO2. The sample synthesized with the addition of CMC showed higher resistance and worse electrochemical stability. Therefore, the specific capacity of the sample decresed. The heat treatment at300℃and400℃could change crystal structure of MnO2and improve electrochemical performance of the manganese dioxide. Especially, MnO2treated at300℃shows good cycle stability.The composite materials prepared by the liquid precipitation method are doped with Cr. The influence to MnO2physical and electrochemical properties was studied on factors of the content of K2Cr2O7, backflow time and reductant. The results show that the K2Cr2O7amount and refluxing time have effect on physical characteristics and the electrochemical performance of the MnO2materials. In company with the increase of the K2Cr2O7amount and the reflux time, the morphology of the products change from nanospheres to nanorods with an average diameter of80nm and the length of0.5～2μm. When the mass ratio of KMnO4to K2Cr2O7is10:1and the refluxing time is0.5h, the MnO2materials are nanospheres, and its specific surface area is the largest. The sample showed good electrochemical performance. In0.5mol/L Na2SO4solution, the MnO2electrodes showed a specific capacitance of129F/g at a current density of1.5A/g, which is twice more than that of the undoped material.The composite materials prepared by the liquid precipitation method are doped with Sn. The effect of the content of Sn on the composite materials were studied. XRD and SEM of the samples showed that the morphology of the materials doped with Sn was not affected. MnO2 doped with Sn were nanospheres, whose average diameter is50-100nm. When the molar ratio of Mn to Sn is100:2.5, the composite materials showed high rate performance. In1mol/L KOH solution, a specific capacitance of287F/g was obtained at a current density of0.5A/g for MnO2doped with Sn, the value is higher than that of the undoped (101F/g). At a current density of1A/g, the specific capacitance of MnO2doped with Sn still remained183F/g, and electrochemical properties were better than other electrodes.