Improving the rate performance of LiFePO4 by Fe-site doping

LiFePO4 doped by bivalent cation in Fe-sites show improved rate performance and cyclic stability. Under 10 C rate at room temperature, the capacities of LiFe0.9M0.1PO4 (M = Ni, Co, Mg) maintain at 81.7, 90.4 and 88.7 mAh/g, respectively, in comparison with 53.7 mAh/g for undoped LiFePO4 and 54.8 mAh/g for carbon-coated LiFePO4 (LiFePO4/C). The capacity retention is 95% after 100 cycles for doped samples while this value is only 70% for LiFePO4 and LiFePO4/C. Such a significant improvement in electrochemical performance should be partially related to the enhanced electronic conductivities (from 2.2 × 10−9 to <2.5 × 10−7 S cm−1) and probably the mobility of Li+ ions in the doped samples.