Influence of the Initial Li/Co Ratio in LiCoO2 on the High-Voltage Phase-Transitions Mechanisms.

The influence of the initial Li/Co stoichiometry in LiCoO2 (LCO) (1.00 ≤ Li/Co ≤ 1.05) on the phase-transition mechanisms occurring at high voltage during lithium deintercalation ( V > 4.5 vs Li+/Li) was investigated by in situ X-ray diffraction. Even if the excess Li+ in Li1.024Co0.976O1.976 does not hinder the formation of the H1-3 and O1 phases, the latter are obtained at higher voltages and exhibit larger c parameters compared with their analogues formed from Li1.00CoO2. We also showed that for the stoichiometric Li1.00CoO2 the deintercalation process is more complex than already reported, with the formation of an intermediate structure between H1-3 and O1.