pH值和螯合剂复合作用对正极材料Li3V2(PO4)3/C性能的影响

摘要

The Li3V2(PO4)3/C composite cathode material was synthesized via sol-gel method using three different chelating agents (citric acid,salicylic acid and polyacrylic acid) at pH value of 3 or 7.The crystal structure,morphology,specific surface area and electrochemical performance of the prepared samples were investigated by X-ray diffraction (XRD),scanning electron microscopy (SEM),cyclic voltammetry (CV),electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge test.The results show that the effects of pH value on the performance of the prepared materials are greatly related to the chelating agents.With salicylic acid or polyacrylic acid as the chelating reagent,the structure,morphology and electrochemical performance of the samples are greatly influenced by the pH values.However,the structure of the materials with citric acid as the chelating agent does not change as pH value changes,and the materials own uniform particle size distribution and good electrochemical performance.It delivers an initial discharge capacity of 113.58 mA·h/g at 10C,remaining as high as 108.48 mA·h/g after 900 cycles,with a capacity retention of 95.51％.%使用不同的螯合剂(柠檬酸、水杨酸和聚丙烯酸)在不同的pH值条件下,采用溶胶-凝胶法合成Li3V2(PO4)3/C正极材料.通过X射线衍射(XRD)、扫描电镜(SEM)、循环伏安(CV)、电化学阻抗谱(EIS)以及恒流充放电测试等方法,研究材料的结构、形貌及电化学性能.结果表明,pH值对材料性能的影响与所采用的螯合剂有很大的关系.当采用水杨酸和聚丙烯酸为螯合剂时,升高pH值对材料的结构、形貌和电化学性能有较大的负面影响.而采用柠檬酸为螯合剂时,材料结构无变化且颗粒分布更均匀,高倍率放电性能和循环性能也得到改善,10C首次放电容量为113.58 mA·h/g,循环900次后容量保持率为95.51％.