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

Abstract

This paper reports on a study of the magnetic susceptibility, x-ray photoelectron, and x-ray emission spectra of the LiCoO_2−δ and Na_xCoO₂ 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 LiCoO_2−δ reduced oxides gives rise to the formation of divalent cobalt ions. The deficiency of the alkali metal in Na_xCoO₂ initiates the formation of holes in the oxygen 2p band while not changing the electronic configuration d⁶ of the cobalt-ion ground state.