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 LiCoO 2 (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 Li 1.024 Co 0.976 O 1.976 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 Li 1.00 CoO 2 . We also showed that for the stoichiometric Li 1.00 CoO 2 the deintercalation process is more complex than already reported, with the formation of an intermediate structure between H1–3 and O1.