溶胶机械活化及其溶剂对LiFePO4/C结构和电化学性能的影响

本文在溶胶凝胶法制备碳包覆LiFePO4/C锂离子电池正极材料的基础上,对溶胶进行机械球磨活化以进一步优化LiFePO4/C复合材料的结构和形貌,并通过原位引入Fe2P等方法,提高其高倍率性能。采用XRD、SEM、元素分析等材料结构测试分析方法和恒电流充放电及电化学阻抗谱电化学测试技术,对溶胶机械活化及不同溶胶溶剂对LiFePO4/C材料结构和电化学性能的影响进行了研究。研究结果表明,机械活化能有效减小LiFePO4/C颗粒的尺寸及改善其分散性,并能改变Fe2P相的含量。溶胶机械活化处理后的LiFePO4/C在不同倍率下的放电容量明显增加。相对于蒸馏水,乙醇作为溶胶溶剂获得的LiFePO4/C材料具有更好的倍率性能,其在1C和10C的容量分别达到136mAh/g和90mAh/g。

Effects of Mechanical Activation of Sol and Different Solvents on the Structure and Electrochemical Properties of LiFePO4/C Cathode Materials

Mechanical activation for the sol has been introduced in a sol-gel method to synthesize LiFePO4/C cathode materials used for lithium ion batteries in order to optimize the structure and morphology of LiFePO4/C.By means of the in situ introduction of the high electron conductivity Fe2P phase,the capability of the synthesized LiFePO4/C product has been effectively improved.The effects of the mechanical activation of the sol and different solvents on the structure and electrochemical properties of LiFePO4/C composites have been studied by using X-ray diffractometry(XRD),scanning electron microscopy(SEM),electrochemical impedance spectroscopy(EIS),element analysis and electrochemical testing of galvanostatic charge-discharge etc.The results show that mechanical activation of sol plays an important role in reducing the particle size of LiFePO4 and the agglomeration,and hence,improves the high-rate capability.The amount of Fe2P formed has also been changed by the mechanical activation and the solvents.Compared with distilled water,solvent of ethanol leads to smaller LiFePO4 particles and possess better high-rate capacity and the corresponding LiFePO4/C achieves specific capacities of 136 and 90 mAh/g at the rates of 1C and 10C,respectively.