中文摘要：

为提高LiFePO4的充放电性能，用化学沉淀法制备了镁离子掺杂的磷酸铁锂，用电化学方法测量了Li1-xMgxFePO4（x=0．00、0．02、0．05、0．07、0．10和0．20，摩尔分数）的充放电性能，用X射线衍射（XRD）和里特沃尔特（Rietveld）方法表征了掺杂对LiFePO4的晶体结构的影响。结果表明少量镁离子掺杂能有效地提高LiFePO4比容量和循环性能，其中Li0.05Mg0．05FePO4具有更好的电化学性能，放电比容量高出LiFePO4约20mAh／g，镬离子掺杂提高了LiFePO4中Fe^3＋／Fe^2＋共存态的浓度，使材料具有更好的导电能力。

英文摘要：

In order to improve the performance of LiFePO4, Li1-x MgxFePO4 was prepared by co-precipitation method, where x,the tool fraction of Mg^2＋ , is 0.00, 0.02, 0.05, 0.07, 0.10 and 0.20. Crystal structure and charge/discharge performance of doped LiFePO4 were investigated by X-ray diffraction with the Rietveld method and electrochemical measurement, respectively, The results show that Mg^2＋ doping with low concentration can increase the capacity and cycle performances of LiFePO4 ,and Li0.95 Mg0.05 FePO4 has better performance than the others, which discharge capacity is higher 20mAh/g than LiFePO4. Rietveld refinement indicates that doped metal atoms randomly substitute for Li atom in the LiFePO4 structure, Because Mg^2＋ doping not only causes the change of atomic position and distance and the shrinkage of crystal cell, but also increases the concentration of coexisted Fe^3＋/Fe^2＋ in LiFePO4, which increases the electrical conductivity of LiFePO4.