Strengthen metal-O interaction toward high ionic mobility on doping LiFePO4

LiFePO4 was widely applied in mobile phones, cars, and other energy fields where ion migration rate was an important performance parameter of the cell, determining the cycling performance and rate performance. However, there were relatively few first-principles calculations on the ionic mobility of lithium iron phosphate. Here, we systematically investigated the mobility of various metal-doped LiFePO4 using density functional theory calculations. MD and NEB methods showed that Ti significantly reduced the diffusion barrier and improved ionic mobility. The crystal structure and electronic structure revealed that Ti doping decreased the p-band center of the O orbital and delocalized the Fe t2g orbital, leading to a strong metal-O bond. Compared with other materials, it was found that the strength metal-O bond could broaden the diffusion channel and increase the ionic mobility, resulting in the highest ionic mobility value of 5.57 × 10−12 cm2s−1 for Ti-doped LiFePO4. Tuning the metal-O bond provided a novel and efficient avenue for elevating migration rates, which was expected to be applied in many metal–oxygen batteries.