Electronic structure of defective lithium cobaltites Li (x) CoO2

Abstract

X-ray absorption, resonant X-ray emission, and X-ray photoelectron spectroscopical methods have been applied for the study of the electronic structure of defective lithium cobaltites Li (x) CoO2 (0.6a parts per thousand currency signxa parts per thousand currency sign1.0). Resonant O K alpha X-ray emission spectra of LiCoO2 showed localized excitonic states due to a dd transition between occupied and unoccupied Co 3d states. On the base of measurements of Co 3s X-ray photoelectron, Co 2p, and O 1s X-ray absorption spectra, it was established that in defective cobaltites the electronic holes are localized mainly in O 2p states. An evidence of phase separation in Li (x) CoO2 has been found. It was shown that the semiconductor-to-metal transition in Li (x) CoO2 (x < 0.76) at about 160 K is not accompanied by changes in the Co 3d electronic configuration which remains 3d (6).