Ti-, Al-, and Cu-Doping Induced Gap States in LiFePO[sub 4]

Abstract

We studied the changes in the electronic structure of induced by Ti-, Al-, and Cu-doping. The technique used in the study was Fe 2p and O X-ray absorption (XAS) spectroscopy. XAS spectra were analyzed using atomic multiplet and band structure calculations. Fe 2p XAS spectra show that the Fe ions in are in a divalent high-spin state, and that the Fe ions remain in this state in the Ti-, Al-, and Cu-doped materials. O XAS spectra present relatively weak transitions to mixed states at threshold (the transitions to states appears at higher energies due to the larger hybridization). O XAS spectra of the doped materials show additional absorption intensity just below threshold. These features correspond to transitions to doped states in the bandgap of the compound.