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

Abstract

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 Li_1.024Co_0.976O_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_1.00CoO₂. We also showed that for the stoichiometric Li_1.00CoO₂ the deintercalation process is more complex than already reported, with the formation of an intermediate structure between H1-3 and O1.