Oxygen contribution on Li-ion intercalation-deintercalation in LiAlyCo1-yO2 investigated by O K-edge and Co L-edge X-ray absorption spectroscopy

The electronic structure of the electrochemically Li-ion deintercalated Li1-xAlyCo1-yO2 system has been investigated intensively with compositional x value variation using soft X-ray absorption spectroscopy (XAS) for oxygen K-edge and Co L-II,L-III-edge. To get reasonably good XAS spectra for the electrochemically Li-ion deintercalated LiAlyCo1-yO2 system, we made binder-free LiAlyCo1-yO2 film electrodes using the electrostatic spray deposition technique. The spectral changes of the O K-edge XAS for LiAlyCo1-yO2 during charging are relatively more dramatic than those of the Co L-II,L-III-edge XAS. From the results of the spectral changes of the Co L-edge and O K-edge XAS between LiCoO2 and LiAl0.25Co0.75O2 during charging, it is concluded that the substitution of Al for Co ions in LiCoO2 induces more increased oxygen participation in the charge compensation process during charging. (C) 2002 The Electrochemical Society.