Abstract
By combining first-principles calculations and experimental x-ray photoemission (XPS) spectroscopy measurements, we investigate the electronic structure of potential Li-ion battery cathode materials LiPO (, Fe, Co, Ni) to uncover the underlying mechanisms that determine small hole polaron formation and migration. We show that small hole polaron formation depends on features in the electronic structure near the valence-band maximum and that, calculationally, these features depend on the methodology chosen for dealing with the correlated nature of the transition-metal -derived states in these systems. Comparison with experiment reveals that a hybrid functional approach is superior to in correctly reproducing the XPS spectra. Using this approach, we find that LiNiPO cannot support small hole polarons, but that the other three compounds can. The migration barrier is determined mainly by the strong- or weak-bonding nature of the states at the top of the valence band, resulting in a substantially higher barrier for LiMnPO than for LiCoPO or LiFePO.
- Received 21 November 2011
DOI:https://doi.org/10.1103/PhysRevB.85.115106
©2012 American Physical Society