Li−Fe−P−O 2 Phase Diagram from First Principles Calculations

We present an efficient way to calculate the phase diagram of the quaternary Li−Fe−P−O2 system using ab initio methods. The ground-state energies of all known compounds in the Li−Fe−P−O2 system were calculated using the generalized gradient approximation (GGA) approximation to density functional theory (DFT) and the DFT+U extension to it. Considering only the entropy of gaseous phases, the phase diagram was constructed as a function of oxidation conditions, with the oxygen chemical potential, μO2 , capturing both temperature and oxygen partial pressure dependence. A modified Ellingham diagram was also developed by incorporating the experimental entropy data of gaseous phases. The phase diagram shows LiFePO4 to…