First-principles study of the chemical bonding and conduction behavior of LiFePO4

The electronic structure and chemical bonding of LiFePO4 were calculated using maximally-localized Wannier functions within the framework of the first-principles method. Comparison of the shifts in Wannier centers between LiFePO4 and delithiated reference (FePO4)r structures demonstrated the unstable chemical bonding of Fe–O1 and Fe–O2 during delithiation. The contribution of each orbital to the small-polaron polarization field was discussed in detail. The small polaron hopping is accompanied by a very small polarization field with the value of 0.049 C/m2. Results of our calculations showed that the chemical bonding of Fe–O3 has an important function in the low-temperature conductivity of LiFePO4.