Li_2CO_3,FePO_4和葡萄糖合成LiFePO_4的机制研究

Mechanism of Synthesizing LiFePO_4 with Li_2CO_3,FePO_4 and Glucose

通过变温XRD对以Li2CO3,FePO4和葡萄糖为反应体系合成LiFePO4材料的反应机制进行了研究,采用XRD、SEM、硫碳分析等测试方法,从碳含量和原料分散混合均匀性角度探讨了在LiFePO4合成过程中Li3Fe2(PO4)3,Li3PO4,Li0.5Fe2.5O4等杂相的产生原因。结果表明Li3Fe2(PO4)3,Li3PO4,Li0.5Fe2.5O4等杂相的产生原因主要是Li2CO3和葡萄糖在前驱体中的分布不均造成的,而非作为还原剂的葡萄糖加入量的问题,Li2CO3在前驱体中的分布均匀性影响合成LiFePO4过程中Li+向FePO4中的扩散,葡萄糖在前驱体中的分布均匀性决定了Li2CO3与FePO4合成LiFePO4时能否提供满足反应进行的还原性气氛。通过对原料预研磨优化原料粒径分布、提高原料分散混合均匀性的方法有效地减少或消除了杂质组分的生成,改善工艺后制备的LiFePO4/C较改善工艺前制备的LiFePO4电性能有明显提高,在0.1C的条件下首次充电容量为149.4 mAh.g-1,放电容量为140.1 mAh.g-1。

The reaction mechanism of Li2CO3,FePO4 and glucose at high temperature was researched by using different-thermo system X-ray diffraction.By using XRD,SEM and sulfur-carbon analytical methods,the causes of impurity phases,such as Li3Fe2(PO4)3 and Li0.5Fe2.5O4 were discussed.The results showed that these impurities were caused by the asymmetric distribution of raw materials in the precursor,but not by glucose added into the precursor.Li2CO3 distribution state had great influence on the process of Li+ diffusio...