Preparation Of Nickel And Manganese Oxide And Its Electrochemical Performance

As a kind of new energy storage device, supercapacitor, so-called electrochemical capacity, combines the characteristics of conventional dielectric capacitors and batteries simultaneously. It owns unique advantages including high power density, long cycle life and friendly to environment and is a promising technology used in many fields such as energy recovery, capacitance automobile, instrument and so on. Transition metal oxide including NiOx and MnOx an important kind of supercapacitor electrode materials as substitute of expensive RuO2 because of its low cost and excellent electrochemical performance. As is known, electrode material is the core part of supercapacitor and the physicochemical properties of material are decided by its phase composition and microstructure. Therefore, the research on the preparation of material with large surface area and porous structure and special composites becomes the the focus of related research in recent years.In this paper, porous spherical nickel oxide was prepared via a simple hydrothermal method with C6H12N4 as precipitant and template. The formation process and mechanism were explored by a series of experiments. Besides, by means of adjusting the concentrations of reactants, NiO nanoflakes and particles were synthesized. Compare and analyze the final products of different microstructures, the one with the best electrochemical performance was found. In addition, we prepared the nickel and manganese oxides by simple coprecipatation method. Change the content of Ni2+ and Mn2+ in reactants, the nickel and manganese oxides with different Ni/Mn ratio were gained, and then the influence of the rative content of Ni2+ and Mn2+on electrochemical performance was explored. Phase composition and microstructure were identified by XRD respectively, and the electrochemical performance was tested by three-electrode system after electrode manufacture.The result shows that porous spherical NiO without impurity is synthesized, and the average diameter of the spheres is 5 um, constructed by the interactive arrangement of many nanoflakes in three dimensions. From the formation process we find that the construction of the sphere is gradually variational based on lower dimension. The concentrations of reactants have an important influence on the microstructure of final product. The optimum conditions of the perfect sphere is the concentrations of NiSO4 and (CH2)6N4 are 0.4M and 0.2M respectively. Further to change the concentrations of reactants, the other two kinds of microstructures-nanoflake and nano particle are gained, the transformation of the three kinds is continuous. Test their electrochemical performance using three-electrode system, we find that the porous spherical NiO is best, of which rate capacitance can reach 1080 F/g at the current density of 1A/g, and the reversibility and rate performance are unique at the same time. This is because that the large surface area and porous structure benefit the access of electrolyte and ion transformation. The resistance is small and the active points are many.In addition, nickel and manganese oxides compositions are synthesized trough coprecipatation. The Ni/Mn ratio influences the phase and microstructure heavily. When the Ni/Mn ratio exceeds 1, namely the content of Ni is more than Mn, the main phase is nano particle NiO, while it is Mn2O3 when the Ni/Mn ratio is smaller than 1. Among them, some samples including 3/1,2/1, 1/2,are the nickel and manganese oxides composition micron sphere composed of NiO/Ni2O3 and Mn2O3. Especailly, when the content of Ni is equal to Mn, the fianl product is the combination of NiMn2O4, NiMnO3 and Mn2O3 in the way of micron sphere. The electrochemical performance measurements showed that all the samples exhibit typical Faradic redox capacitance. The specific capacitance is different with the change of nickel and manganese molar ratio, which is related to the phase and microstructure. Among them, the samples of the nickel and manganese oxides composition have better performance than others. This is because the composition effect of nickel and manganese oxides develop the utilization of electrode material, leading to the optimization of electrochemical performance.