Electronic structure of the electrochemically delithiated Li 1-xFePO 4 electrodes investigated by P K-edge X-ray absorption spectroscopy

Abstract

P K-edge X-ray absorption spectroscopy (XAS) has been carried out to investigate the electronic structure of the electrochemically delithiated Li 1-xFePO 4 for Li rechargeable batteries. The gradual shift of main edge features to higher energy side showed that P-O bonds become less covalent during delithiation due to the more covalent Fe 3+-O bonds via the inductive effect. A principal component analysis of P K-edge XAS spectra of the electrochemically delithiated Li 1-xFePO 4 reveals that this set of spectra can be well represented by two primary components, in good agreement with a first-order phase transition involving the LiFePO 4 and FePO 4 phases. From the observation of pre-edge peaks, it is concluded that electrochemical delithiation of Li 1-xFePO 4 results in the hybridization of P 3p states with the Fe 3d states. © 2006 The Electrochemical Society.