ABSTRACT
We report here the Raman spectrum and lattice dynamics study of a well-crystallized ß-V(2)O(5) material prepared via a high-temperature/high-pressure (HT/HP) route, using α-V(2)O(5) as the precursor. Periodic quantum-chemical density functional theory calculations show good agreement with the experimental results and allow one to assign the observed spectral features to specific vibrational modes in the ß-V(2)O(5) polymorph. Key structure-spectrum relationships are extracted from comparative analysis of the vibrational states of the ß-V(2)O(5) and α-V(2)O(5) structures, and spectral patterns specific to the basic units of the two V(2)O(5) phases are proposed for the first time. Such results open the way for the use of Raman spectroscopy for the structural characterization of vanadium oxide-based host lattices of interest in the field of lithium batteries and help us to greatly understand the atomistic mechanism involved in the α-to-ß phase transition of vanadium pentoxide.
ABSTRACT
Raman spectra of the electrochemically lithiated TiO2 anatase are reported. They evidence spectral features induced by Li intercalation in the high-frequency region. Emergence of these lines supports recent hypothesis [M. Wagemaker et al., J. Am. Chem. Sec. 125, 840 (2003)] for formation of short Li-O valence bonds. This suggestion is verified by the lattice dynamics simulation based on the potential model with Li-O force constants extrapolated from known studies of the lithium oxide compounds. The obtained results confirm assumption of multiple Li positions and provide assignment of all the observed spectral features.
