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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 synthesizing LiFePO4 with Li2CO3, FePO4 and glucose as reaction system was investigated by temperature-programmed XRD. The effects of LiFePO4 synthesis on the carbon content and the homogeneity of raw materials were investigated by XRD, SEM and sulfur-carbon analysis. In the process of Li3Fe2 (PO4) 3, Li3PO4, Li0.5Fe2.5O4 and other heterogeneous causes. The results show that the reason for the heterogeneity of Li3Fe2 (PO4) 3, Li3PO4 and Li0.5Fe2.5O4 is mainly caused by the uneven distribution of Li2CO3 and glucose in the precursor, rather than the amount of glucose added as reductant. Li2CO3 The distribution uniformity in the precursor affects the diffusion of Li + into FePO4 during synthesis of LiFePO4. The uniformity of the distribution of glucose in the precursor determines whether the Li2CO3 and FePO4 synthesize LiFePO4 can provide a reducing atmosphere that satisfies the reaction. By pretreatment of raw materials to optimize the particle size distribution of raw materials to improve the raw material dispersion and mixing uniformity of the method effectively reduce or eliminate the formation of impurity components, improve the process of preparation of LiFePO4 / C prepared prior to improving the process of LiFePO4 obvious electrical properties The initial charge capacity was 149.4 mAh.g-1 at 0.1 C and the discharge capacity was 140.1 mAh.g-1.