Hydroxyl Defects in LiFePO Cathode Material: DFT+ and an Experimental Study.

Lithium iron phosphate, LiFePO, a widely used cathode material in commercial Li-ion batteries, unveils a complex defect structure, which is still being deciphered. Using a combined computational and experimental approach comprising density functional theory (DFT)+ and molecular dynamics calculations and X-ray and neutron diffraction, we provide a comprehensive characterization of various OH point defects in LiFePO, including their formation, dynamics, and localization in the interstitial space and at Li, Fe, and P sites. It is demonstrated that one, two, and four (five) OH groups can effectively stabilize Li, Fe, and P vacancies, respectively.