Changes in Chemical Bondings by Li Deintercalation in LiMO2 (M=Cr, V, Co and Ni)

Abstract

First principles molecular orbital calculations for LiMO₂ and MO₂ have been carried out using the discrete variational Xα cluster method. Li in LiMO₂ is nearly completely ionized. Strong covalent interaction between M and O is noted. The removal of Li significantly increases the interaction between M and O. This results in the “oxidation” associated with the de-intercalation not of M but of O. The formal redox notation for the de-intercalation, i.e., M(IV)/M(III), is thus far from reality. The difference in the de-intercalation capability among four LiMO₂ compounds is ascribed to the difference in the magnitude of electrostatic repulsion between the oxygen layers in MO₂.