Synthesis And Electrochemical Properties Of Metal Composite Oxides MFe₂O₄and Ce₂Sn₂O₇

A series of ferrite MFe2O4(M=Fe、Zn、Co、Mn、Mg) spinel spheres and ultrafine cube-shape Ce2Sn2O7nanoparticles crystallized in pure fluorite phase had been synthesized. Their electrochemical properties had been investigated in details. The specific research contents can be summaried as follows:Ferrite MFe2O4(M=Fe、Zn、Co、Mn、Mg) spinel spheres were prepared by a solvothermal process, which were used as the anode materials for lithium ion batteries. Electrochemical tests exhibited that the discharge-charge curves were relatively flat and charge-discharge platforms were longer, which had stable electrochemical performance. Among the MFe2O4(M=Fe、Zn、Co、Mn、Mg) nanospheres, the MgFe2O4demonstrated relatively the highest reversible capacity with a value of950mA·h/g, the highest coulumbic efficiency (73.1%), the best cycling stability and high rate capability. In order to improve cycling performance of the transition metal ferrite, ZnFe2O4and CoFe2O4were coated by conductive carbon. As can be seen by comparing, the capacity and capacity retention of the carbon-coated electrode materials had been greatly improved, indicating their promising application as anode materials for Li-ion batteries.Ultrafine cube-shape Ce2Sn2O7nanoparticles crystallized in pure fluorite phase with a size of about10nm had been synthesized by a facile hydrothermal method. The optimal synthesis conditions were as follows:180℃as reaction temperature,8h as reaction time, NaOH as the precipitator, pH=12. The as-synthesized Ce2Sn207ultrafine nanocubes had been evaluated as electrodes for pseudo-capacitors. The tests showed that the capacitor had good electrochemical reversibility, and a smaller electrode charge transfer impedance. The obtained material also had been used as the anode material for lithium ion batteries. The platform of charge-discharge curves were relatively close, indicating that excellent reversibility. At the large current density of IOC, the capacities were 56.1mA℉h/g、56mA-h/g after65cycles, which indicated that this electrode materials had good electrochemical reversibility and structural stability.