Effect on the electrochemical performance of lithium iron phosphate by Cr3+ ion doping

Two different methods (mechanical ball-milling and co-precipitation) were applied to prepare lithium iron phosphate (LiFePO4) containing low concentration (1%, mole fraction) Cr3+ ion dopant. The samples were characterized by X-ray diffraction and scanning electron microscope, and their electrochemical performances were investigated including cycling behavior and large current discharging. The results indicate that the Cr3+ ion dopant does not affect the structure of the material but considerably improves its kinetics in terms of capacity delivery and cycle performance. At a low discharging rate (0.1 C), LiFePO4 samples doping via mechanical ball-milling and co-precipitation are capable of delivering reversible specific capacities of 144 mAh . g(-1) and 158 mAh . g(-1) respectively, with fairly stable cycleability. Even at a 2C discharging rate, they can show capacities of 110 mAh g (-1) and 130 mAh . g(-1) respectively, too. The results also confirm that doping via co-precipitation with Fe sources is an effective method to improve the ion doping effect.