无水溶胶-凝胶法制备LiFePO_4／C电极材料及其结构和电化学性能

Synthesis and Performance of LiFePO_4/C Prepared by Nonaqueous Sol-Gel Method

以乙二醇为溶剂,采用溶胶-凝胶法合成了LiFePO_4/C.采用X射线衍射、扫描电镜、透射电镜和电化学阻抗谱等分析测试方法,研究了600～750℃范围内合成的LiFePO_4/C的微观结构特征、在不同放电倍率下的循环稳定性和放电容量等电化学性能.研究结果表明,合成温度对LiFePO_4的结晶状况及LiFePO_4/C电极的电化学性能有着显著的影响.700℃烧结的产物结晶完整,颗粒细小(～150nm)均匀,电化学性能有了显著的提高,0.5C的放电容量达到150mAh/g,1C的放电容量仍有141mAh/g,经200个循环,放电容量基本保持不变.

LiFePO4/C was synthesized by a sol-gel method using glycol as solvent. X-ray diffraction and scanning electron microscope were used for the phase identification and the structural observation of the synthesized LiFePO4 products. The electrochemical properties including the cycle stability, the discharge capacity under different discharge rates of LiFePO4 synthesized at 600-750℃ were investigated by means of electrochemical impedance spectroscope and other methods. The results show that the crystallization and electrochemical performance of LiFePO4/C are affected remarkably by the sintering temperature. LiFePO4/C sintered at 700℃ is well crystallized and has an even distribution of gain with size of around 150nm, exhibiting excellent electrochemical properties. Its discharge capacity reaches 150mAh/g at 0.5C and the discharge capacity still reaches 141mAh/g at 1C. The discharge capacity of the LiFePO4/C is almost reserved after 200 cycles.