In situ Raman microspectrometry investigation of electrochemical lithium intercalation into sputtered crystalline V2O5 thin films

We report here the first in situ Raman microspectrometry study of the electrochemical lithium insertion and de-insertion reaction into crystalline sputtered LixV2O5 thin films (0 ≤ x ≤ 0.94) in liquid electrolyte. We show that the orthorhombic Pmmn symmetry of the pristine material is kept upon lithium intercalation in the LixV2O5 film (0 ≤ x ≤  0.94). In fact, a subsequent and unexpected solid solution behaviour is evidenced, leading to the typical Raman fingerprint of the ɛ-LiV2O5 phase for the Li0.94V2O5 composition. After the charge, a complete recovery of the local structure is found, in good accord with the excellent electrochemical reversibility exhibited by these thin films. Such limited structural changes differ from that usually observed for the bulk material, which emphasizes the key role of the microstructure and morphology on the nature and magnitude of the structural rearrangements induced by the lithium insertion process.