Structural modifications of Li x V 2 O 5 in a composite cathode (0≤ x < 2) investigated by Raman microspectrometry

The structural behaviour of the Li x V 2 O 5 active material in a composite electrode is determined upon lithium insertion/extraction in the 4–2.15 V potential range (0≤ x < 2) using Raman microspectrometry. For the first time, a detailed description of phase transitions occurring in the V 2 O 5 composite electrode is provided by Raman spectroscopy, on the basis of a complete assignment of the spectra. This approach has been successful because of the knowledge of the Raman fingerprints of the chemically lithiated compounds, combined with a rigorous and systematic deconvolution of the Raman spectra obtained for the electrochemically lithiated materials. The successive emergence of α, ε, δ and γ phases is clearly established, as well as the α/ε, ε/δ and δ/γ biphasic regions corresponding to the 3.4, 3.2 and 2.3 V potential plateaus, respectively. This study shows that Raman spectroscopy constitutes a sensitive and relevant tool to explore the emergence of the various phases governing the electrochemical properties of cathode materials for lithium batteries. Copyright © 2011 John Wiley & Sons, Ltd.