温度对水热反萃法合成锂离子电池正极材料LiFePO_4的影响

Effect of Temperature on LiFePO_4 as a Cathode Material for Lithium-Ion Battery by Hydrothermal Stripping Technique

采用水热反萃法合成了锂离子电池正极材料LiFeP04，重点研究了温度对LiFeP04结构、形貌和电化学性能的影响．分别采用X射线衍射仪（XRD）、扫描电子显微镜（SEM）、循环伏安（CV）、交流阻抗（EIS）及恒电流充放电测试对样品的结构、形貌和电化学性能进行了表征．结果表明：在140～250℃范围内水热反萃法可以合成纯相的LiFeP04．用制备的LiFeP04作为电池的正极材料，其电化学测试表明：250℃合成的样品极化最小，同时具有最小的电荷转移阻抗和最大的Li‘扩散系数，0．1C下首次放电比容量为151．7mA·h／g，较高倍率下循环40次再采用0．1C时的放电比容量可达到161．9mA·h／g，具有良好的倍率循环性能．

A series of LiFePO4 samples have been successfully synthesized by hydrothermal stripping technique at different temperatures, and the influence of temperature on the structure, morphology and electrochemical perform- ances of samples is studied by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, cyclic voltam- metry （CV）, electrochemical impedance spectroscopy （EIS）and constant current charge-discharge tests. The results show that pure LiFePO4 can be synthesized at 140--250 ℃ by hydrothermal stripping technique. The cell made by the sample synthesized at 250 ℃ as the cathode material has the minimum polarization, presents the minimum charge-transfer resistance and the biggest lithium-ion diffusion coefficient, and shows good capacity retention and cycle performances. The sample displays the first discharge capacity of 151.7 mA ~ h/g at 0.1 C and 161.9 mA h/g after 40 cycles of higher rates.