控制溶液pH值氧化Fe²⁺离子制备球状FePO₄.2H₂O及LiFePO₄/C电极材料

Preparation of Spherical FePO₄.2H₂O and LiFePO₄/C Electrode Materials by Controlled Solution pH during Oxidation of Fe²⁺ Ions

在1.0 mol/L FeSO4和H3PO4溶液中,通过调节氧化Fe2+时溶液的pH值,在无任何添加剂的条件下制备出不同形貌和结构的FePO4·2H2O沉淀。以FePO4前驱体、Li2CO3和蔗糖为原料,经700℃碳热反应10 h后得LiFePO4/C电极材料。运用X-射线衍射(XRD)、扫描电子显微镜(SEM)、热重-差热(TG-DTA)和循环伏安(CV)等方法对样品进行了表征。结果显示,当加入H2O2时溶液的pH在1.6~2.0之间,可得到由200 nm左右的一次颗粒构成的球状FePO4?2H2O粉末。由纳米结构FePO4前驱体合成得到粒径为1 μm左右的球形LiFePO4/C,其在1.0 mol/L Li2SO4水溶液中显示良好的电化学性能。

FePO4?2H2O powders with various morphologies and structures were prepared in a solution of 1.0 mol/L FeSO4 and 1.0 mol/L H3PO4 without any additives, by adjusting pH of the solutions during oxidation of Fe2+ ions. LiFePO4/C electrode materials were synthesized using the FePO4·2H2O precursor, Li2CO3 and sucrose by the carbothermic reduction method at 700?C for 10 h. The powders were analyzed with X-ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetric-differential thermal analysis (TG-DTA) and cyclic voltammetry (CV) methods. The results show that the spherical FePO4·2H2O agglomerates of primary particles about 200 nm can be obtained in the solution of pH controlled within 1.6 - 2.0 when adding H2O2 for oxidation of Fe2+ ions. The spherical LiFePO4/C materials with particles size about 1 μm were synthesized from the nanostructural FePO4 precursors. The LiFePO4/C materials show favorable electrochemical performance in 1.0 mol/L Li2SO4 aqueous solution.