纳米FePO4的合成及其正极材料LiFePO4/C的电化学性能研究

以Fe3+为铁源,采用控制结晶技术合成了纳米FePO4.xH2O,将FePO4.xH2O于500℃热处理4 h后得到纳米FePO4前驱体,然后通过碳热还原在不同温度下煅烧合成橄榄石结构的纳米LiFePO4/C样品.采用差热/热重、X射线衍射、扫描电镜、比表面测试、电化学性能测试等分析测试方法对纳米FePO4.xH2O、FePO4前驱体及不同煅烧温度下制得的纳米LiFePO4/C样品进行表征.研究结果表明,700℃烧结10 h合成LiFePO4/C样品的粒径在40~100 nm左右,比表面积为79.8 m2/g;700℃煅烧合成样品在电压2.5~4.2 V,倍率为0.1C、1C、5C、10C、15C时的放电比容量分别达到156.5、134.9、105.8、90.3和80.9 mAh/g,具有较好的倍率性能;样品还表现出较好的容量保持率.

Synthesis of Nano FePO4 and Electrochemical Characterization of Composite Cathode Material LiFePO4/C

Nano FePO4.xH2O powders were synthesized by controlled crystallization method,using Fe(Ⅲ) compound as the iron source.The nano FePO4.xH2O powders were pretreated at 500℃ for 4 h in air to obtain nano FePO4 pre-cursor.Then the olivine nano LiFePO4/C composites were obtained through carbonthermal reduction process at dif-ferent temperatures.The structure,morphology,physicochemical properties and electrochemical properties of the nano FePO4.xH2O powder,FePO4 precursor and LiFePO4/C composites synthesized at different temperatures were charac-terized in detail by thermogravimetric/differential scanning calorimeter(TG/DSC),X-ray diffraction(XRD),scan-ning electron microscope(SEM),Brunauer-Emmett-Teller(BET) surface area measurement and electrochemical measurement.The results show that the nano LiFePO4/C composite calcined at 700℃ for 10 h has fine particle sizes of about 40-100 nm.The BET test shows that the as-prepared nano LiFePO4/C composite has great specific surface area of 79.8 m2/g.The nano LiFePO4/C composite cathode material can deliver an initial discharge capacity of 156.5,134.9,105.8,90.3 and 80.9 mAh/g in the voltage range of 2.5-4.2 V,at rate of 0.1C,1C,5C,10C and 15C respec-tively,which exhibits good rate performance.The nano LiFePO4/C composite also demonstrates excellent cyclic performance.