Oxygen contribution on Li-Ion intercalation-deintercalation in LiAl_y Co_1-yo₂ investigated by O K-edge and Co L-edge X-ray absorption spectroscopy

The electronic structure of the electrochemically Li-ion deintercalated Li_1-xAl_yCo_1-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,III-edge. To get reasonably good XAS spectra for the electrochemically Li-ion deintercalated LiAl_yCo_1-yO₂ system, we made binder-free LiAl_yCo_1-yO₂ film electrodes using the electrostatic spray deposition technique. The spectral changes of the O K-edge XAS for LiAl_yCo_1-yO₂ during charging are relatively more dramatic than those of the Co L_II,III-edge XAS. From the results of the spectral changes of the Co L-edge and O K-edge XAS between LiCoO₂ and LiAl_0.25Co_0.75O₂ 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.