Preparation And Study Of Manganese Oxide Nanomaterials With Different Morphologies

Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption(electrochemical double-layer capacitors) or fast surface redox reactions(pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. Toupin et al. predicted theoretically a high specific capacitance(SC) of 1370 F/g for MnO2-based supercapacitor electrodes.However, practically, these oxides generally show poorer SC, ca. one-sixth or one-seventh of the above value. Major limitations of MnO2-based materials are their poor electronic conductivity and densely packed structures with limited accessible surface area, which significantly affect their electrochemical activity. O ne key strategy in improving the SC is the morphological and crystal lographic design of manganese oxides at nanometer-scale including the fabrication of nanoparticle, nanowire, nano sheet, hollow nanosphere and nanoporous materials. A number of studies have reported that a capacitance value of nanoscale manganese oxides can be improved by enhancing the surface area. Another method is to add more conductive materials to manganese oxide matrix to improve the electronic conduc tivity.This thesis mainly chose manganese dioxide nano materials as the object of study. A variety of MnO2 nano materials with special morphologies was prepared and studied using scanning electron microscopy, X-ray diffraction, BET specific surface area test, nitrogen/adsorption to characterize the microstructure of the material. And the constant current charge and discharge tests were operated to study the electrochemical performance.This paper mainly includes the review and two experimental parts. C hapterⅠ overview section discusses the basic features, development status, structural ultracapacitors, energy storage mechanism and the main methods of preparation of manganese dioxide nanomaterials. The experimental part chooses manganese sulfate and potassium persulfate as the reaction system. They were prepared under different conditions in a long rod-shaped manganese dioxide nanomaterials and flower globular manganese dioxide nanomaterials(C hapter III). And they were further prepared in a short rod manganese dioxide nanomaterials and a linear manganese dioxide nanomaterials by adding a cationic influential to the reaction system(C hapter Ⅳ). The electrochemical performance of the prepared nano manganese dioxide material was then studied. The last chapter(Chapter Ⅴ)is the summary of the whole text.