Electrochemical properties and structure of LiFePO_4/C with Co-doping in Fe-site and Li-site

摘要

LiFePO_4/C compounds of co-doping in Li-site and Fe-site were synthesized with traditional solid state reaction. The electrochemical and physical properties of these samples were characterized by XRD, SEM and EA. The substitution in Li-site and Fe-site led to the modifications of the structure and electrochemical performance such as initial capacity, capacity fading and polarization. The lattice constants and electrochemical performance of Sr-doped sample were larger and poorer than these of other doping samples. The co-doping samples with 1% M (Mo~(6+) and Nd~(5+)) and 3% Mn~(2+) exhibited excellent electrochemical performance, especially in high rate. Moreover, the co-doping samples with 6% Mn~(2+) exhibited mild capacity fading. From these results, it was suggested that the appropriate co-doping in Li-site and Fe-site could improve both electronic and ionic conductivities of LiFePO_4, which may pose to some modifications of its electrochemical performance.