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

Abstract

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.

Structural modifications of LixV2O5 in a composite cathode (0≤x < 2) investigated by Raman microspectrometry

“…[35] Because all valence V-O bonds are oriented along coordinate axes, a qualitative characterisation of the normal vibrations of the V 2 O 5 lattice can also be done in terms of atomic displacements. [28] Most of the low wavenumber modes can be described in terms of external modes of V 2 O 5 units. They have been derived from the relative motions of two V 2 O 5 units belonging to the unit cell, three of them generating displacements of vanadium atoms along the x-axis (195 cm −1 ), y-axis (147 cm −1 ) and z-axis (105 cm −1 ).…”

“…It has been recently and successfully applied to follow the structural changes occurring in a Li x V 2 O 5 thinfilm electrode. [28,32,34] In this paper, a detailed description of the structural modifications induced in a Li x V 2 O 5 composite cathode during lithium electrochemical intercalation in the 4-2.15 V potential range is provided for the first time.…”

The Influence of Colloidal Opal Template and Substrate Type on 3D Macroporous Single and Binary Vanadium Oxide Inverse Opal Electrodeposition

“…For the orthorhombic phase of V 2 O 5 with a space group Pmmn and D 2h point symmetry, the Raman spectra are now well-established. 63,64 Specifically, to compare the ED crystal structures, we refer to the known Raman active modes for the Pmmn space group that are modified compared to bulk V 2 O 5 because of the crystallization of the electrodeposited IO structured V 2 O 5 . [65][66][67][68] The Raman data for IO ED on FTO-coated glass and the SS substrate showed near identical crystal structure -all dominant modes are observed.…”

“…63,64 Specifically, to compare the ED crystal structures, we refer to the known Raman active modes for the Pmmn space group that are modified compared to bulk V 2 O 5 because of the crystallization of the electrodeposited IO structured V 2 O 5 . [65][66][67][68] The Raman data for IO ED on FTO-coated glass and the SS substrate showed near identical crystal structure -all dominant modes are observed. In each case, the sharpest peak at the 993 and 997 cm −1 mode indicates the stretching mode associated with the short vanadyl (V = O) bond, with some broad low intensity peaks showing V-O-V stretching vibrations between 300-750 cm −1 .…”

Lithium transition metal (Ti, Nb, V) oxide mesoporous thin films: Contrasting results when attempting direct synthesis by evaporation-induced self assembly

“…This suggests that lithium and vanadium are intimately mixed in the inorganic network. However, the coexistence of phases with various Li-V molar ratios [38][39][40] points to a degree of inhomogeneity in the Li-V distribution.…”