Journal
CHEMISTRY OF MATERIALS
Volume 20, Issue 5, Pages 1916-1923Publisher
AMER CHEMICAL SOC
DOI: 10.1021/cm702979k
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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 LixV2O5 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 E-type phase, whose interlayer distance continuously increases with x, is clearly evidenced all along the Li insertion process: lithium ions rapidly produce an orthorhombic E 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 Both modes are consistent with the local structure of the c lithium-rich phase called is an element of ' 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.
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