【摘要】 以三价铁盐为铁源,采用多元醇还原法在低温下制备出了具有不同长径比的棒状LiFePO4材料.通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、循环伏安(CV)、交流阻抗谱(EIS)和恒电流充放电测试等手段分析了不同回流反应时间下制备出的前驱体和最终的LiFePO4/C样品.结果表明:回流反应时间对LiFePO4的形貌和特性有明显的影响.通过把回流反应时间从4 h延长至16 h,材料的形貌由不规则的短棒状颗粒变为规则的长棒状颗粒,且棒的直径明显变小.当回流反应时间为10 h时,样品复合了多种形貌,有利于电子的传输,在低倍率下具有优秀的性能,0.1C放电比容量为163 mAh g-1;当回流反应时间为16 h时,样品具有最大的长径比,有利于锂离子的扩散,在高倍率下具有良好的性能,1C、3C、5C、10C、20C倍率下放电比容量分别为135、125、118、110、98 mAh g-1,循环性能良好,几乎无衰减.更多还原

【Abstract】 Rod-like LiFePO4 /C particles with different aspect ratios were synthesized by controlling the reflux reaction time in polyol medium at a low temperature, using an Fe3 +salt as the iron source. The precursors and final LiFePO4 /C samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), and galvanostatic charge-discharge test. The results show that the reflux reaction time has a significant effect on the characteristics of the LiFePO4 precursors and electrochemical performance of the final LiFePO4 /C samples. The morphology of the precursors is transformed from irregular short rod-like particles into regular long rod-like particles, and the aspect ratios of the rods increase with increasing reflux reaction time from 4 to 16 h. At a reflux reaction time of 10 h, the material contains multifarious morphologies, which is beneficial to the electron transmission, and displays an excellent electrochemical performance at low discharge rates, the discharge capacity is 163 mAh g-1at 0.1C rate. Extension of the reflux reaction time to 16 h, the material reveals the biggest aspect ratio, which is conducive to the diffusion of lithium ions, and gives good electrochemical performance at high discharge rates, the discharge capacities are measured to be 135, 125, 118, 110, and 98 mAh g-1at 1C, 3C, 5C, 10C, and 20C rates, respectively, revealing good cycling performance and little capacity fading.更多还原