磷酸铁锂性能改性的研究

The effect of carbon adding method on the performance of LiFePO_4 synthesized by aqueous precipitation and carbothermal reduction

以FeSO4·7H2O、NH4H2PO4和H2O2为初始原料,通过液相沉淀法制得前驱体FePO4,然后通过碳热还原制得LiFePO4。我们采用两种加碳方式:a、先制得FePO4,然后加炭黑混合高温合成LiFePO4;b、先把炭黑分散在液相中,然后通过液相沉淀制得含碳的FePO4,再高温合成LiFePO4。SEM(扫描电子显微镜)分析表明:方法b制备的FePO4颗粒比方法a制备的FePO4颗粒细小。在其它条件相同的情况下方法b合成的LiFePO4的电化学性能要优于方法a合成的电化学性能。采用方法b于560℃煅烧12h制备的LiFePO4在0.1C放电倍率下其比容量为149mAh/g,而当放电倍率达到1C时,放电比容量为124mAh/g,且具有良好的循环性能。

Two samples of LiFeP4 were synthesized with different adding methods for carbon. For the first method, carbon is mixed with FePO4 which was prepared by aqueous precipitation of FePO4 from FeSO4·7 H2O and NH4H2PO4 with hydrogen peroxide as the oxidizing agent, then LiFePO4 is synthesized by carbothermal reduction. For the second method, carbon is mixed with FePO4 in liquid during the process of aqueous precipitation, and then LiFePO4 is synthesized with the same condition. It was showed by SEM （ scanning electronic microscopy ） that the particle size of FePO4 prepared by the second method is obvious smaller than that of the first one. The electrochemical second method was much better than that of the first one, which performance of LiFePO4 synthesized at 560℃ for 12 h by the delivered discharge capacity of 149 mAh/g at 0.1 C rate, 124 mAh/g at 1 C rate and exhibited satisfactory capacity retention.