Vibrational spectroscopic and electrochemical studies of the low and high temperature phases of LiCo(1-x)M(x)O(2) (M=Ni or Ti)

A spinel structure with the space group Fd3m is unambiguously assigned to LiCoO2 synthesized at 400 degrees C, according to Raman and infra-red spectra of LT-LiCoO2 and factor group analysis of the vibrational modes for the layered (R (3) over bar n) and the spinel (Fd3m) structure models. The vibrational modes involving significant motion of lithium atoms are observed at 536 and 271 cm(-1) for HT-LiCoO2, and at 451 and 267 cm(-1) for LT-LiCoO2 in the infra-red spectra. Although solid solutions could be prepared for HT-LiCo(1-x)M(x)O(2) (M = Ni, 0<x<1; M = Ti, x<0.2) and LT-LiCo1-xNixO2 (x<0.2) some impurities were observed in LT-LiCo1-xTixO2. The nickel or titanium-doped LT-LiCo(1-x)M(x)O(2) (M = Ni and Ti, x<0.2) cathodes exhibit smaller capacities than does their parent compound LT-LiCoO2.