Abstract: 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 2 C 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.

Key words: Lithium iron phosphate, Co-precipitation, Ion doping, Electronic conductivity, Lithium intercalation capacity, Positive electrode material