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在惰性气氛下,以Li2CO3、FeC2O4·2H2O和NH4H2PO4为原料,用高温固相方法合成了橄榄石型LiFePO4材料.利用不同升温速率的热重及差热分析研究了固相合成LiFePO4的反应动力学.研究表明,LiFePO4的高温固相合成过程可分为三个步骤,利用Doyle-Ozawa法和Kissinger法分别计算了各个反应阶段的表观活化能.用Kissinger法确定每个反应阶段的反应级数和频率因子,并给出了各个阶段的动力学方程.根据动力学研究的结果,采用优化的固相分段法合成了碳包覆改性的LiFePO4正极材料.利用X射线衍射、扫描电镜及恒流充放电对材料进行了物性表征及性能测试.结果表明,该材料具有单一的橄榄石结构,颗粒尺寸细小均匀,0.1C倍率放电时表现出良好的电化学性能.
In an inert atmosphere, LiFePO4 was synthesized from Li2CO3, FeC2O4 · 2H2O and NH4H2PO4 by high temperature solid-state method. The reaction kinetics of solid-phase synthesis of LiFePO4 was investigated by TG and DTA at different heating rates The results show that the high temperature solid phase synthesis of LiFePO4 can be divided into three steps, and the apparent activation energy of each reaction stage is calculated by Doyle-Ozawa method and Kissinger method respectively.The reaction order of each reaction stage is determined by Kissinger method And the frequency factor, and gives the kinetic equation of each phase.According to the results of kinetic study, the carbon-coated LiFePO4 cathode material was synthesized by the optimized solid phase segregation method.Using X-ray diffraction, scanning electron microscopy The material was characterized by means of constant current charge and discharge and the performance test was carried out.The results show that the material has a single olivine structure with small and uniform particle size and good electrochemical performance when discharged at 0.1C rate.