In-situ X-ray diffraction of Li intercalation in sol-gel V2O5 films

We have performed an electrochemical and in-situ X-ray diffraction study of Li intercalation in crystalline V2O5 thin films to find out if these films , prepared by the sol-gel route using vanadium oxo-isopropoxide as precurso r, show different LixV2O5 phases than V2O5 prepared by other techniques. Fo r x = 0.0 and x = 0.4 the results are identical. The phases found can be de scribed as alpha-V2O5 (x = 0.0) and epsilon-LixV2O5 (x = 0.4). However, for a larger degree of intercalation some noticeable differences became appare nt. First, the phase for x = 0.8 showed an elongated c-axis compared to eps ilon-LixV2O5 (x = 0.8). Moreover, it is probably monoclinic. Second, the el ectrochemical and structural data do not provide evidence for the formation of delta-LiV2O5 (x = 1.0). Third, the phase for x = 1.4 bears some resembl ance to delta-LiV2O5. The reason for these differences is sought in the str ucture and chemistry of the present V2O5 films. It is suggested that this i s subtly different from that of 'standard' crystalline material, owing to t he low-temperature sol-gel preparation route. (C) 1999 Elsevier Science B.V . All rights reserved.