Preparation And Electrochemical Performance Of Several Transition Metal (Ni,Cu,Mn) Oxides And Composites

Supercapacitors, a new energy storage device, compared with Li-ion batteries and traditional capacitors, they have longer cycling life, higher power density and have higher energy density. So it has been widely investigated. However, supercapacitor energy density is very low, which restricted their further applications in the future. The supercapacitors electrode materials are usually include polymers, carbon materials, metals oxides, and their composite materials. Because of transition metal oxides (NiO, Co3O4, CuO , FeOx , MnO2 andV2O5) have excellent pseudocapacitive behavior, high electrical conductivity and environmental friendliness, they have been widely investigated in supercapacitors. In view of their practical application, electrode materials should be synthesis easily, abundant reserves,reasonable price. Each kind of electrode materials owns its intrinsic shortcomings, which will hinder its electrochemical performance in the supercapacitors. Recently some researches show that rational design of materials strcture can improve the specific capacitance. The main contents are summarized as follows:Through a simple hydrothermal process, we get unique morphology CuO-NiO composites. SEM?TEM?XRD and XPS test were imployed to test the morphology and structure of the composites. In the electrochemical test, we use CuO-NiO composites as positive electrode, Pt as counter electrode and Hg/HgO as reference electrode. We use the unique morphology CuO-NiO composites which can improve the capacitive of the positive eletrode and the energy density of the capacitor. The composites in the 6 M KOH electrolyte,high energy density of 35 Wh/kg, specific capacitance of 280 F/g, good cycling stability after 1000 cycles, the capacitance retention can be achieved 94%. Its electrochemical properties can be found according to the research, the electrochemical properties of CuO-NiO composites is much higher specific capacitance and better cycle stability than pure CuO and pure NiO.Through a modify stober method prepare silica sphere, and coated a layer of N-droped carbon shell. Calcination the product , use a facile approach to directly grow MnO2 nanosheets on NHCS frameworks, between KMnO4 and carbon occur the redox reaction. The product is SiO2@NHCSs@MnO2. Add NaOH solution, etch SiO2 The final product is NHCSs@MnO2. The SEM image and the TEM image shows that the composites is hollow structure, this unique structure can tremendously increase the product surface area, the large specific surface area will provide much electrical contact spot with the current collector,which is beneficial for improving electrochemical capacity. (The composites in the Na2SO4 electrolyte, specific capacitance of 306 F/g, good cycling stability, after 5000 cycles, the capacitance retention can be achieved 95%). NHCSs@MnO2 has better electrochemical properties than pure NCS and pure MnO2, NHCSs@MnO2 is an ideal electrode material.