Investigation of inorganic compounds on the surface of cathode materials using Li and O K-edge XANES

Inorganic compounds on the surfaces of the cathode materials LiNi0.80Co0.15Al0.05O2 and LiCoO2 were studied using Li and O K-edge X-ray absorption near edge structure (XANES) measurements. Rietveld analysis revealed that the LiNi0.80Co0.15Al0.05O2 sample contained 2% Li2CO3, while the LiCoO2 sample was single-phase. The Li and O K-edge XANES spectra indicated that the surface of LiCoO2 was almost free of residual Li2CO3. In contrast, the presence of both residual Li2CO3 and an additional cubic phase were observed, respectively, on and near the surface of LiNi0.80Co0.15Al0.05O2. These results demonstrate that the XANES technique, using a combination of the total electron yield and fluorescence methods, is an effective tool for probing the surfaces of cathode materials.