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

The vibrational spectra of various nickel-cobalt oxides used as positive el ectrode 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 compound s LiNi1-yCoyO2 were examined. The local environment of cations with respect to neighboring oxygen atoms was determined by considering the polyhedral u nits forming the lattice. Structural modifications induced by the intercala tion-deintercalation process, by cation substitution, or by the low-tempera ture preparation route were examined using Raman and infrared spectra and f actor group analysis of the vibrational modes for the layered (R (3) over b arm) and the spinel (Fd (3) over barm) structure models. (C) 2000 Elsevier Science B.V. All rights reserved.