Raman Microspectrometry Study of Electrochemical Lithium Intercalation into Sputtered Crystalline V2O5 Thin Films

• Published in: Chemistry of materials Vol. 20; no. 5; pp. 1916 - 1923
• Main Authors: Baddour-Hadjean, R, Pereira-Ramos, J. P, Navone, C, Smirnov, M
• Format: Journal Article
• Language: English
• Published: American Chemical Society 11.03.2008
• Subjects: Characterization of Materials; Electrochemistry; Structural Characterization (including AFM, NMR, X-ray Diffraction, etc.)
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm702979k

Raman microspectrometry has been used to investigate the local structural changes induced by the electrochemical lithium intercalation reaction in crystalline sputtered V2O5 thin films in a liquid electrolyte. Contrary to usual composite electrodes made of a mixture of active material and conductive and binding agents, the use of a pure V2O5 thin film allows a homogeneous Li insertion in the material and a high quality of Raman signatures to be obtained. The Raman spectra of Li x V2O5 compounds for 0 < x < 1 are examined as a function of the lithium content and discussed in relation with the X-ray diffraction data pertinent to these h00-oriented thin films and literature data. An assignment of all Raman bands is proposed, and the Raman fingerprint of the ϵ-type phase, whose interlayer distance continuously increases with x, is clearly evidenced all along the Li insertion process: lithium ions rapidly produce an orthorhombic ϵ phase characterized by a vanadyl stretching mode at 984 cm−1 for 0 < x < 0.5, and further Li accommodation induces a splitting into two stretching modes, the first one shifting from 984 to 975 cm−1, the second from x = 0.7 located at a fixed wavenumber of 957 cm−1. Both modes are consistent with the local structure of the ϵ lithium-rich phase called ϵ′ and reflect the existence of two different lithium sites. This work illustrates that the structural changes, in terms of long-range order and local structure, are strongly dependent on the microstructure and morphology of the material.