| Three-dimensional ordered macroporous material(3DOM) has many advantages such as large aperture, uniform distribution, good cyclical channel arrangement. At the same time, it possesses the characteristic of large specific surface area and thin hole wall, which makes it an ideal substrate to prepare high stability and high-energy lithium-ion battery. Three dimensional ordered macroporous titania(3DOM TiO2) prepared by colloidal crystal template has highly ordered three-dimensional reticular structure, but its capacity is not high, and conductivity is poor. The transition metal oxides, such as α-Fe2O3 and Fe3O4, is a kind of environmental friendly materials with high specific capacity(1005 mAh g-1 and 926 mAh g-1, respectively), good conductivity, low cost, abundant resources. However, its cycle performance and stability are not high.In this paper, we proposed to synthesize a novel 3DOM TiO2/iron oxide composite, in which the permanent magnet CoPt coating was added to adsorb the pulverized iron oxide particles so as to enhance the comprehensive performance of the composite electrode. The PMMA microspheres with different particle sizes were obtained by emulsifier free emulsion polymerization to fabricate colloidal crystal templates. Sol-gel method and hydrothermal method were used to prepare 3DOM Ti O2, TiO2/CoPt and iron oxide. The phase and morphology characterization of the prepared samples were analyzed. The cycle performance, charge/discharge performance and magnetic performance of the materials under different condition were tested.In chapter 3, the PMMA microspheres with different particle size were synthesized to prepare the colloidal crystal template. Then 3DOM Ti O2 with different particle size were successfully prepared on the template using isopropyl titanate as precursor. The results show that reaction time, temperature and initiator will affect the particle size of PMMA microspheres. Through lots of experiments, the PMMA microspheres with the size of 230, 360, 460 and 560 nm were prepared. The optimal condition for the preparation of PMMA colloidal crystal template is under constant temperature of 60 ℃ and humidity of 60 %. SEM shows that the prepared TiO2 has three-dimensional ordered porous structure. Combining to the charge/discharge curve and ratio curve, it is found that the electrochemical performance of the sample with particle size of 460 nm is the best.In chapter 4, using 3DOM TiO2 as the base, 3DOM TiO2/CoPt composites were prepared by sol-gel method, and the different aperture, solution concentration and the dosage of influence on the electrochemical properties were discussed. The results show that the most suitable solution concentration is 0.4 mol/L, dosage is 2 mL. Electrochemical test results show that the sample with the size of 230 nm has the highest reversible capacity. But the particle size of 230 nm is too small,which is not beneficial to the subsequent coating of iron oxide materials. So the sample with the pore size of 460 nm is chosed to be the base.In chapter 5, nanosized Fe3O4 with 500 nm was synthesized by hydrothermal method. TiO2/CoPt composite was mixed with Fe3O4 particles. At the same time, Fe2O3 particles about 2~5 nm was also prepared, and 3DOM TiO2/CoPt/Fe2O3 composite materials were synthesized by sol-gel method. The magnetic properties of Fe3O4 and TiO2/CoPt and the electrochemical properties of the other samples were tested. The results show that the capacity of magnetized Ti O2/CoPt/Fe3O4 composite remains 42.28% after 50 times cycle at different current density and back to 50 mA g-1 again, which is higher than unmagnetized TiO2/CoPt/Fe3O4 composite(31.29 %) and the pure Fe3O4(11.37 %). The discharge capacity of magnetized 3DOM TiO2/CoPt/Fe2O3 composite is up to 1563.33 mAh g-1 for the first time in the current density of 50 mA g-1. The ratio curve also shows that the rate performance of magnetized 3DOM TiO2/CoPt/Fe2O3 composite is better than Fe2O3 and the unmgnetized 3DOM TiO2/CoPt/Fe2O3 composite. |
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