Synthesis And Properties Research Of ?-Fe₂O₃ And Composites As Supercapacitor Electrode Material

Supercapacitors, due to their high power densities, fast charging/discharging, and long cycle life, continue to draw a great deal of research attention as an indispensable energy storage device of the clean energy era. A large number of the research effort has been focused on the development of electrode materials. Iron oxides (FexOy) have been considered as promising electrode materials for supercapacitors, since its low cost, earth abundance, low toxicity, environmental friendliness, but the practical application in supercapacitors has been limited by its low electronic conductivity and cycle life. Therefore, in dissertation, Fe3+ was used as iron resource to synthesize ferric oxide nanoparticles and nanocomposites which were used in electrochemical field.1. Preparation and electrochemical application of y-Fe2O3 nanoparticlesA simple electrophoretic deposition process for fabricating y-Fe2O3 nanoparticles by using Fe(NO3)3 as the iron resource and N-methyl-2-pyrrolidone as solvent. The synthesis process can be speculated by changing the concentration of Fe(NO3)3 and refluxing time. The morphology and structure of the synthesized materials were characterized by a series of tests. The results showed that the y-Fe2O3 nanoparticles aggregated to form the three-dimensional broccoli structure. The electrochemical performance of electrode materials was studied by cyclic voltammetry and constant current charge/discharge and AC impedance. The test showed that y-Fe2O3 nanoparticles as the electrode material displayed good reversibility and the specific capacitance as high as 345 F g-1 at a current density of 3 A g-1. The cycling measurement showed that its capacity retention was 89.3% after 1000 cycles at a current density of 1 A g-1.2. Preparation and electrochemical characteristics of y-Fe2O3/graphite nanocompositesy-Fe2O3/graphite nanocomposites were synthesized via one-step solvothermal process using liquid phase stripping of graphite (Gp) as the carbon source, FeCl3 as the iron resource, NaOH as the precipitant and N-methyl-2-pyrrolidone as solvent. The y-Fe2O3/Gp nanocomposites can be observed by changing the reaction temperature and the amount of graphite. The products can be characterized by the help of TEM, XRD, SEM, Raman, etc. It had successfully prepared the y-Fe2O3/Gp nanocomposites. The electrochemical performance of y-Fe2O3 and y-Fe2O3/Gp was investigated using cyclic voltammetry (CV), galvanostatic charge-discharge measurement (GCD), AC impedance by three-electrode system. The results showed that the electrode material are all typical pseudo-capacitance capacitors. In the process of charge-discharge process occurred oxidation-reduction reaction. The product of adding the 7 mL graphite dispersion with 20 g L-1 solid content showed specific capacitance 520 F g-1 at a current density of 3 A g-1. The cycling measurement showed that its capacity retention is 91.3% after 1000 cycles at a current density of 3 A g-13. Solvent evaporation induced self-assembly of magnetic nanoparticles form y-Fe2O3 filmThe solvothermal synthesized y-Fe2O3/Gp nanoparticles were dispersed in different volume of ethanol, different polar solvents and binary system. y-Fe2O3 film embodied from dot shape to dendritic morphology were obtained, which keep the possibility to be uased as supercapacitor electrode.