Synthesis and characterization of Mg and Ti ions co-doped lithium iron phosphate and its lithium-ion batteries

Mg and Ti ions co-doped (Li _0.98Mg _0.01)(Fe _0.98Ti _0.01)PO ₄/C cathode material for lithium-ion batteries was prepared by a solid-state method under N ₂ atmosphere. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and galvanostatic charge-discharge test. Results indicated that Mg and Ti ions co-doping remarkably improved the electrochemical performance of LiFePO ₄, including rate capacity, temperature behavior, and cycling stability. Discharge capacities of 154.7 and 146.9 mAh·g ^-1 were obtained at the rates of 0.2C and 1C for half-cell tests, respectively. For 60 Ah full-cell tests, 100% of 1C capacity was maintained even at 3C rate, 89.7% and 63.1% of initial capacity at room temperature were retained at 0 and -20 °C, respectively. 89% capacity retention remained after 2000 cycles at room temperature, presenting excellent cycle stability. This investigation suggests that the present co-doping material and the resulting battery possess large discharge capacity and excellent cycling performance, making it applicable in electric vehicle (EV)/hybrid electric vehicle (HEV) and energy storage systems on a large scale.