磷铁和碳酸锂配比对LiFePO_4晶体结构和性能的影响

Influence of Matching Ratio of Fe-P to Li_2CO_3 on the Crystal Structure and Performance of LiFePO_4

以磷化工副产物磷铁为原料成功合成了晶型较好的LiFePO4材料,讨论了磷铁与碳酸锂的配料比对产物晶体结构和电化学性能的影响规律。用XRD、SEM、恒流充放电法和电化学阻抗谱对产物的组成、结构、形貌和电化学性能进行了分析。SEM结果表明LiFePO4产物的颗粒粒径分布比较均匀,XRD和电化学性能测试结果表明锂含量的增加会导致LiFePO4的(020)面优先生长,(121)与(111)面的相对峰强比对LiFePO4的晶型和电化学性能有较大的影响。磷铁与Li2CO3的质量比为2.17/1时制备的LiFePO4的电化学性能最好,放电容量高达129 mA h g 1,经过8次循环容量仍保持127 mA h g 1,电荷转移阻抗最低,为38.68。

LiFePO4 with good crystal structure was synthesized successfully by using the Fe-P by-product from phosphorus chemical industry as raw material. The effects of the mass ratio of Fe-P to Li2CO3 on the crystal structure and the electrochemical performance of the products were studied. The properties, including component, structure, morphology and electrochemical performance, of the products were characterized by XRD, SEM, galvanostatic charge/discharge method and electrochemical impedance spectroscopy, respectively. SEM images indicate that the particle size distribution is uniform. XRD and electrochemical performance testing results show that increase of lithium content can enhance the preferential growth of （020） plane of the synthesized LiFePO4, and the relative peak intensities of （121） plane to （11 1） plane play an important role in determining the crystal structure and the electrochemical performance of the LiFePO4. When the mass ratio of Fe-P to Li2CO3 is 2.17/1, the synthesized LiFePO4 has the best electrochemical performance, its discharge capacity can reach 129 mA.h.g-1, and can still remain 127 mA.h.g^-1 after 8 cycles at 0.1 C, and the charge transfer resistance is the lowest which is about 38.68 Ω.