固相烧结法制备锂离子电池正极材料Li_(2)FeP_(2)O_(7)及其电化学性能研究

Synthesis of Li_(2)FeP_(2)O_(7)Cathode Material at Different Temperatures and Its Electrochemical Performance for Lithium Ion Batteries

介绍了一种先冷冻干燥后固相烧结制备正极材料Li_(2)FeP_(2)O_(7)的方法.利用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和傅里叶变换红外光谱(FTIR)对材料的组成和形态进行表征,并通过循环伏安曲线(CV)和电化学阻抗谱(EIS)研究了Li_(2)FeP_(2)O_(7)材料的电化学性能.研究发现,合成Li_(2)FeP_(2)O_(7)的最佳温度为590℃,此温度下反应较完全且产物杂质较少,1.6C倍率下的放电比容量达到55 mA·h·g^(‒1),明显高于其它温度下合成样品的放电比容量.该温度下合成的Li_(2)FeP_(2)O_(7)还具有低阻抗和较大的交换电流密度,说明这种合成方式有利于提高锂离子在Li_(2)FeP_(2)O_(7)中的扩散.

The cathode material Li_(2)FeP_(2)O_(7)was synthesized via freeze-drying and followed by solid state sintering method.X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and Fourier transform infrared spectroscopy(FTIR)were used to characterize the struc ture,composition and morphology of the material.In addition,the electrochemical performance of the Li_(2)FeP_(2)O_(7)material was investigated by cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS).It was found that the greatest particle quality could be acquired when the synthesis temperature of Li_(2)FeP_(2)O_(7)was 590℃.The discharge specific capacity reached 55.0 mA·h·g^(‒1)at 1.6C,which was much higher than that of the samples synthesized at other temperatures.The Li_(2)FeP_(2)O_(7)synthesized at 590℃had a low im pedance and a large exchange current density,which facilitated the diffusion of lithium ions and improved the electrochemical performance.