Preparation Of Hybridized And Doped Layered-MnO₂-Based Nanomaterials And Their Electrochemical Performance

With the sustainable development of industrialization in modern society,the increasingly serious energy crisis and environmental pollution have to be seriously considered.Supercapacitor as a New Energy Storage device has attracted the attention because of its excellent performance.The electrochemical performance of supercapacitor is mainly determined by the properties of electrode material in capacitor..Transition metal oxide electrode materials have high theoretical specific capacitance and better thermal stability,and are considered as the ideal supercapacitor electrode materials.Co₃O₄,NiO and MnO₂ have been extensively investigated as electrode materials.Among them,Co₃O₄ and MnO₂ have higher theoretical specific capacitance and strong redox reaction ability.But at the same time,their conductivity is poor and their cycle life is short.For electrode materials,the endowing high specific surface area and high electrical conductivity will help of transition metal oxides to improve their electrical conductivity and cycle stability.In this dissertation,the load and doping methods are adopted to overcome the shortcomings of the metal oxide MnO₂,such as low conductivity and actual specific capacitance.rGO-MnO₂ composite and Co-,Ni-doped MnO₂ materials have been prepared and the improvement trend of electrochemical performance of materials with different preparation ratios has been explored.X-ray diffraction,transmission electron microscopy,infrared spectroscopy,scanning electron microscopy,Raman spectroscopy and specific surface area tests were performed to characterize the morphology,structure and physicochemical properties of the as-prepared materials.Electrochemical performance testing of electrode materials were measured using electrochemical workstations and Landeng battery systems.The results show that both of rGO-MnO₂ composite and Co-,Ni-doped MnO₂ materials have improved specific capacitance.At the current density of 1 A g^-1,the optimistic specific capacitances of rGO-MnO₂,Co-,Ni-doped MnO₂ materials are 162.3,118.5 and157.5 Fg^-1,respectively.After 5000 cycles of charge and discharge,the specific capacitance of rGO-MnO₂ was 83%of its original.Excellent chemical properties of rGO-MnO₂ are relative to its high specific surface area and the good electrical conductivity of rGO.The latter can effectively improve the charge transfer rate in the redox process of material.And the improvement of electrochemical performance for Co-,Ni-doped MnO₂ materials maybe be relative to the micro-crystallization of the two-dimensional nanosheets...