Raman scattering of LiNi 1− yAl yO 2

Abstract

We measured Raman spectra from LiNiO 2 and LiNi 1− y Al y O 2 positive electrode materials for lithium-ion batteries. LiNiO 2 oxide is unambiguously shown to have a layered rock-salt structure ( R3̄ m space group), which exhibits two Raman bands at 465 and 545 cm −1 assigned to the E g and A 1g species, respectively. Whereas LiNi 1− y Al y O 2 prepared at low temperature (450 °C) using the succinate sol–gel method develops a spinel structure, LiNi 1− y Al y O 2 prepared by the citrate route is a microcrystalline oxide indicating the α-NaFeO 2 structure ( R3̄ m). 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 LiNi 1− y Al y O 2, in good accordance with the X-ray diffraction (XRD) measurements.