Electronic structure, x-ray spectra, and magnetic properties of the LiCoO2−δ and NaxCoO2 nonstoichiometric oxides

This paper reports on a study of the magnetic susceptibility, x-ray photoelectron, and x-ray emission spectra of the LiCoO2−δ and NaxCoO2 nonstoichiometric oxides. The valence-band structure of LiCoO2 was analyzed. The hole concentration in the oxygen 2p band of LiNiO2 and LiCoO2 was derived from measurements of the O Kα emission spectra. Measurements of Co 2p and Co 3s photoelectron spectra showed that the Co3+ ions reside in the low-spin state with S=0. The deficiency of oxygen in the LiCoO2−δ reduced oxides gives rise to the formation of divalent cobalt ions. The deficiency of the alkali metal in NaxCoO2 initiates the formation of holes in the oxygen 2p band while not changing the electronic configuration d 6 of the cobalt-ion ground state.