Preparation And Electrochemical Performance Of Nano-metal Oxide Materials For Supercapacitors

Supercapacitor is a new type of electrochemical energy storage devices which performance between the typical dielectric capacitors and the typical rechargeable batteries.It has the advantages of both of them.The typical dielectric capacitors can provide high power densities and have long cycle life,but low energy densities.The typical-rechargeable batteries can provide high energy densities,but low power densities and short cycling life.Supercapacitors can meet both power and energy requirements of the systems,and have drawn more and more attention in recent years.Studies on super-capacitors are mainly focus on the preparation of high performance electrode materials and electrolytes.In this dissertation,electrode materials preparation and electrolyte choice were investigated.The microstructures and morphologies of these materials were investigated by XRD?SEM measurements.The electrochemical performance has been evaluated by galvanostatic charge-discharge,cyclic voltammetry(CV)and A.C.Impedance.The main content is the following:The MWCNTs was treated by HNO3,The micro structures and morphologies of these materials were investigated by IR?SEM measurements.The electrochemical performance has been evaluated by galvanostatic charge-discharge,cyclic voltammetry(CV)and A.C.Impedance.In an electrolyte of 2mol·L-1 KOH,the treated samples showed perfect supercapacitor characterization,a specific capacitance of 32.4F·g-1 was achieved.Also,the PAN electrochemical performance was investigated.CNTs/MnO2 were prepared with chemical co-precipitation method by reacting MWCNTs,KMnO4 and MnSO4.The electrochemical influence of raw material ratio and electrolyte was main investigated.In an electrolyte of 2mol·L-1 KOH,?(MnO2)=20%,a specific capacitance of 103F·g-1 was achieved.Cauliflower MnO2 were prepared by hydrothermal synthesis method by reacting MnSO4 and(NH4)2S2O8 with Fe(NO3)3.The samples were analyzed by X-ray diffraction(XRD)and scanning electron microscopy(SEM).Cyclic voltammetry and galvanostatic charge-discharge were used to characterize the electrochemical performance of the samples.The results showed that the prepared samples were ?-MnO2.The particles were in a cauliflower shape with a diameter of 700nm.In an electrolyte of 6mol·L-1 KOH,electrode based on the MnO2 showed perfect supercapacitor characterization in the potential region of 0-0.4V(vs.SCE).At a current density of 100mA·g-1,a specific capacitance of 176F·g-1 was achieved.The Fe3O4 nanoparticals were prepared with chemical co-precipitation method,where the effect of process factors such as the ratio of Fe3+ and Fe2+,pH,temperature of crystallization on Fe3O4 nanoparticals were investigated,and the optimum preparation conditions were determined.The prepared Fe3O4 nanoparticals,used as electrode materials for supercapacitor,were also detected through electrochemical performances test.The results show that the products were well-crystallized Fe3O4 nanoparticles when the optimum effect conditions were used.As electrode materials,the operating voltage of Fe3O4 is 0.4V.Its specific capacitance is 24.3F/g at a current density of ImA/cm2.