Structural study of the T#2-LixCoO2 (0.52 < x ≤ 0.72) phase

The metastable O-2-LiCoO2 phase undergoes several reversible phase transitions upon lithium deintercalation. The first transition leads to an unusual oxygen stacking in such layered compounds. This stacking is found to be stable for 0.52 < x less than or equal to 0.72 in LixCoO2 and is called T(#)2. We studied this phase from a structural viewpoint using X-ray and neutron diffraction (ab initio method). The new stacking derives from the O-2 one by gliding every second CoO2 slab by ((1)/(3), (1)/(6), 0). The lithium ions are found to occupy very distorted tetrahedral sites in this structure. We also discuss the possibility of this T(#)2 phase to exhibit stacking faults, whose amount depends on the method used to prepare this deintercalated phase.