LiFe_(1-x)Mg_xPO_4/C的制备和性能研究(英文)

Synthesis and Characterization of LiFe_(1-x)Mg_xPO_4/C Composite Cathode Materials

以乙酸镁为掺杂元素、蔗糖为碳源,采用固相反应法制备镁掺杂磷酸铁锂包覆碳复合材料LiFe_(1-x)Mg_xPO_4/C(x=0.01,0.02,0.03,0.04)。利用X射线衍射(XRD)分析其结构,扫描电镜(SEM)观察其形貌,恒电流法测定其电化学性能。研究结果表明镁离子掺杂没有影响材料的结构,而是提高了其放电容量和循环性能。在这些样品中,LiFe_(0.98)Mg_(0.02)PO_4/C的容量最高,首次放电达到140.0mAh/g;并且在80次循环后容量没有衰减反而增加到148.6mAh/g左右。

To improve the performance of LiFePO_4,single phase LiFe_(1-x)Mg_xPO_4/C(x=0,0.01,0.02,0.03,0.04) cathodes were synthesized by two-step solid-state method.The samples were characterized by X-ray diffraction(XRD)、scanning electron microscopy (SEM) and charge-discharge test.The results indicate that the prepared samples have ordered olivine structure and doping of the low concentration Mg^(2+) does not affect the structure of the samples.The electrochemical capabilities evaluated by charge-discharge test show that the sample with 2%(molar fraction) Mg^(2+) has good electrochemical performance delivering about an initial specific capacity of 149.32 mAh/g at 0.2 C-rate.And after 50 cycles,its retains 138.37 mAh/g.