Performance and structure of Mg~(2+) doped lithium iron phosphate prepared by chemical precipitation methode

In order to improve the performance of LiFePO_4,Li_(1-x)Mg_xFePO_4 was prepared by co-precipitation method,where x,the mol 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 LiFePO_4 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 LiFePO_4,and Li_(0.95)Mg_(0.05)FePO_4 has better performance than the others,which discharge capacity is higher 20mAh/g than LiFePO_4.Rietveld refinement indicates that doped metal atoms randomly substitute for Li atom in the LiFePO_4 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 LiFePO_4,which increases the electrical conductivity of LiFePO_4.