Local cationic environment in lithium nickel-cobalt oxides used as cathode materials for lithium batteries

The vibrational spectra of various nickel-cobalt oxides used as positive electrode materials for advanced Li-ion batteries were investigated. Studies were carried out by Raman and FTIR spectroscopies. LiCoO2 and LiNiO2, which are lithiated compounds with a layered structure, and their mixed compounds LiNi1-yCoyO2 were examined. The local environment of cations with respect to neighboring oxygen atoms was determined by considering the polyhedral units forming the lattice. Structural modifications induced by the intercalation-deintercalation process, by cation substitution, or by the low-temperature preparation route were examined using Raman and infrared spectra and factor group analysis of the vibrational modes for the layered (R (3) over barm) and the spinel (Fd (3) over barm) structure models. (C) 2000 Elsevier Science B.V. All rights reserved.