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 precursor, show different LixV2O5 phases than V2O5 prepared by other techniques. For x = 0.0 and x = 0.4 the results are identical. The phases found can be described as alpha-V2O5 (x = 0.0) and epsilon-LixV2O5 (x = 0.4). However, for a larger degree of intercalation some noticeable differences became apparent. First, the phase for x = 0.8 showed an elongated c-axis compared to epsilon-LixV2O5 (x = 0.8). Moreover, it is probably monoclinic. Second, the electrochemical 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 resemblance to delta-LiV2O5. The reason for these differences is sought in the structure and chemistry of the present V2O5 films. It is suggested that this is subtly different from that of 'standard' crystalline material, owing to the low-temperature sol-gel preparation route. (C) 1999 Elsevier Science B.V. All rights reserved.