原位包覆导电聚吡咯的Li_(1.26)Fe_(0.22)Mn_(0.52)O_(2)富锂铁锰基正极材料的制备及电化学性能的提高

Preparation and Improvement of Electrochemical Performance of Li_(1.26)Fe_(0.22)Mn_(0.52)O_(2)Fe-Mn Based Li-Rich Cathode Materials in-Situ Coated with Conductive Polypyrrole

采用化学氧化聚合的方法成功合成了导电聚吡咯(PPy)包覆的纳米尺寸Li_(1.26)Fe_(0.22)Mn_(0.52)O_(2)(LFMO)正极材料。通过X射线衍射(XRD)检测样品的晶体结构,并通过扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察材料形态和微观结构。元素映射和傅里叶变换红外光谱结果表明,PPy导电网络存在于复合材料中,并且PPy均匀分布在LFMO颗粒上。通过恒流充放电测试和电化学阻抗谱(EIS)分析研究了所有样品的电化学性能,结果表明表面上的PPy显著降低了LFMO的电荷转移电阻。包覆PPy质量分数为2%的LFMO-2%PPy表现出极好的倍率性能和良好的循环稳定性,其在1C倍率下首次放电容量为206 mAh·g^(-1),首圈库仑效率为87%,在1C和2C分别循环50圈后,其容量分别稳定在131和139 mAh·g^(-1)。

Nano-sized Li_(1.26)Fe_(0.22)Mn_(0.52)O_(2)(LFMO)cathode material coated with conducting polypyrrole(PPy)was successfully synthesized by simple chemical oxidative polymerization.The crystal structure of the sample was examined by X-ray diffraction(XRD),and the morphology and micro-structure were observed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The elemental mapping and Fourier transform infrared spectrometer results demonstrated that the conductive network of PPy was present in the composites and PPy was uniformly distributed on the LFMO particles.The electrochemical properties of all of the samples were investigated by galvanostatic charge-discharge test and electrochemical impedance spectroscopy(EIS)analysis,which showed that the PPy on the surface significantly decreased the charge-transfer resistance of LFMO.LFMO coated with mass ratio of 2%PPy(LFMO-2%PPy)exhibited excellent rate performance and good cycle stability.The initial discharge capacity was 206 mAh·g^(-1)at the 1C rate,and the initial coulombic efficiency was 87%.After 50 cycles at 1C and 2C,the capacity stabilized at 131 and 139 mAh·g^(-1),respectively.