前驱体FePO_4的制备工艺及其对流变相法合成LiFePO_4/C正极材料的影响

以FeSO4·7H2O,NH4H2PO4,H2O2和NH3·H2O为原料,采用均相沉淀法制备前驱体FePO4·2H2O,再通过流变相法制得LiFePO4/C复合材料,研究了反应温度、搅拌速度和pH值等反应条件对合成LiFePO4/C的影响。采用XRD、SEM和恒流充放电方法表征了材料的结构、形貌和电化学性能。结果表明:当反应温度为60℃,搅拌速度为800 r/min,pH值为2.5时,合成的LiFePO4/C为纯相,且粒度均匀,粒径约为200 nm,在0.1 C充放电倍率下,其首次放电比容量达137 mAh/g。

Effects of FePO4 Reaction Conditions on Electrochemical Properties of LiFePO4/C by Rheological Phase Method

FePO4·2H2O precursor was prepared from FeSO4·7H2O, NH4H2PO4, NH3·H2O and H2O2 as the oxidizing agent by liquid precipitation route, then LiFePO~jC was synthesized by rheological phase method using obtained FePO4 as precursor. Effects of reaction temperature, stirring speed and pH value on the synthesis of LiFePO4/C composites were studied. The structure, morphology and electrochemical performance of the samples are characterized by the XRD, SEM, and galvanostatic charge-discharge methods. The results show that no impurities exist in the LiFePO4/C under the optimal conditions as follows, such as reaction temperature is 60 ℃, stirring speed is 800 r/min and pH value is 2.5. Moreover, samples prepared possess uniform particle size of 200 nm, and the first discharge capacity of obtained LiFePO4/C can be up to 137 mA·h/g at 0.1 C charge-discharge rate.