Lithium Electrochemical Deintercalation from O2-LiCoO[sub 2]

Electrochemical deintercalation of Li from the metastable phase has been investigated up to the composition The single-phase domains that separate the voltage plateaus observed have been characterized by X-ray diffraction. The succession of phases observed upon deintercalation results from reversible sheet gliding or lithium/vacancy ordering, leading to the sequence O2, O6, O2, O2. In particular, the stacking, similar to the T2 phase reported by Dahn and co-workers for the phase, corresponds to oxygen ions not sitting on the three positions of a triangular lattice, hence the # character is used. It exhibits very distorted tetrahedral sites for Li. The O6 stacking exhibits two kinds of octahedra, which might allow ordering in alternate sheets. The most deintercalated phase has never been reported before. Electronic properties and magic-angle spinning nuclear magnetic resonance show a transition to a metallic state for (appearance of the phase with These stacking changes are proposed to result from the minimization of electrostatic repulsion, except for which is believed to result from a Li/vacancy ordering. © 2002 The Electrochemical Society. All rights reserved.