New layered structure obtained by electrochemical deintercalation of the metastable LiCoO2 (O2) variety

LiCoO2(O2) obtained by ion exchange reaction from Na0.70CoO2 has been electrochemically deintercalated. The original lamellar structure with an ABCBA oxygen stacking is called O2. During the deintercalation process two structural transitions occur. A solid solution LixCoO2 (O2∗) (0.71 ⩽ x ⩽ 0.85) with the same stacking as the starting phase is obtained first. At higher voltage (4.3 volt vs. Li) a O2∗ → 06 transition due to sheet gliding occurs. The structure of the new material Li0.62CoO2 (O6) with a six sheet stacking had never been observed before. The O2∗ → O6 transition is discussed from electrostatic considerations. The behavior of the system is compared to that of LixCoO2 (O3) previously reported.