Raman scattering of LiNi1-yAlyO2

We measured Raman spectra from LiNiO2 and LiNi1-yAlyO2 positive electrode materials for lithium-ion batteries. LiNiO2 oxide is unambiguously shown to have a layered rock-salt structure (R (3) over barm space group), which exhibits two Raman bands at 465 and 545 cm(-1) assigned to the E-g and A(1g) species, respectively. Whereas LiNi1-yAlyO2 prepared at low temperature (450degreesC) using the succinate sol-gel method develops a spinel structure, LiNi1-yAlyO2 prepared by the citrate route is a microcrystalline oxide indicating the alpha-NaFeO2 structure (R (3) over barm). The shift of the Raman peak positions suggest that replacement of Ni by Al increases the elementary cell volume and changes the intralayer bond covalency of LiNi1-yAlyO2 in good accordance with the X-ray diffraction (XRD) measurements. (C) 2002 Elsevier Science B.V All rights reserved.