Synthesis and charge/discharge performances of titanium doped lithium iron phosphate

Element doping is one of the main ways to improve the charge/discharge performances of lithium iron phosphate (LiFePO₄) cathode materials. In this paper, modified LiFePO₄ was synthesized by a high-temperature solid-state reduction method using TiO₂ as a titanium source. The structural composition, micro-morphology, and physicochemical properties of titanium-doped LiFePO₄ were characterized by XRD, XPS, SEM, and BET, and further, the relationship between composition-structure and charge/discharge performances was carefully studied. The results indicate that the first discharge-specific capacity of titanium doped LiFePO₄ respectively reaches the maximum of 161.9 and 150.8 mAh/g at 0.1 C and 1 C rate, which is 4.72% and 7.48% higher than LiFePO₄ without titanium doping, and the capacity retention rate achieves as high as 98.54% after 150 cycles at 1 C rate. This is mainly attributed to the substitution of Fe²⁺ by Ti⁴⁺ into LiFePO₄ lattice, which stabilizes the crystal structure and inhibits the secondary growth of crystalline grains, leading to a decrease in Li⁺ extraction/insertion paths and an increase in migration efficiency, thereby improving the discharge specific capacity, rate, and cycle performances of LiFePO₄.