Research On Preparation And Electrochemical Performance Of Metal Oxide Electrode Material With Core-shell Structure

Supercapacitors,which can maintain high energy density while maintaining high power density,have been extensively studied in recent years.Electrode material is the core component of the supercapacitor,which plays a major role in the performance of the supercapacitor.The manganese,cobalt and nickel oxide are superb electrode materials on account of its high theoretical capacitance,abundant in nature,low cost.The core-shell hierarchical structure can shorten the ion diffusion distance,increase the specific capacitance and improve the stability of the electrode.Because of this,we prepare the electrode materials with core-shell structure,which were based on the metal oxide.And electrodes with excellent performance are obtained.The research work of this thesis mainly includes:?1?Prepare the MnO₂ nanoflake/MnO₂ nanotube/three-dimensional graphene foam electrode with core-shell structure and study its electrochemical property.Firstly,the core-shell structure was obtained via CVD method and hydrothermal treatment.The morphology and composition of the samples were characterized by X-Ray Diffraction,Scanning electron microscope,Transmission electron microscopy and Raman spectra.A three-electrode experimental system was employed to study the relationship between the mass loading and electrochemical property.The results indicate when the mass loading is about 60%,at the scan rate of 2 mV/s,the specific capacitance can reach 176 F/g based on the mass of the whole electrode.The cycling lifetime test over 5000 cycles for electrode material was carried out at 50 mV/s.The specific capacitance can reach 124%of the initial value.?2?Prepare the NiO@MnCo₂O₄ electrode with core-shell structure and study its electrochemical property.By means of hydrothermal and thermal annealing process,the electrode material of Ni O@MnCo₂O₄ with core-shell structure was prepared on the Ni foam,and the composition and morphology of the samples were analyzed.A three-electrode experimental system was employed to test the electrochemical performance of the individual MnCo₂O₄ and NiO@MnCo₂O₄composite with core-shell structure.The results demonstrate hierarchical NiO@MnCo₂O₄ core–shell electrode delivered a high specific capacitance of 1186 F/g at current density of 1 A/g,respectively,which is superior to that of the MnCo₂O₄ electrode at the same current density.The results indicate preparing the core-shell structure can enhance the specific capacitance of the electrode.?3?The supercapacitor device was assembly with MnCo₂O₄ electrode material,and we also study the effect of assembly process on the performance of the devices.The device delivered areal specific capacitance of 0.1 F/cm² at current density of 0.5 mA/cm².The assembly process of supercapacitors needs further optimization.