STUDY OF AMORPHOUS AND CRYSTALLINE LI1+XV3O8 BY FTIR, XAS AND ELECTROCHEMICAL TECHNIQUES

Crystalline and amorphous Li1+xV3O8 have been compared by electrochemical and spectroscopic investigations. In particular, the behavior of the two materials in cyclic voltammetric experiments at very low scan rate and the Li+ diffusion coefficient have been studied. The cyclic voltammetry of crystalline Li1+xV3O8 shows the existence of well defined site energies, whilst in the amorphous form the sites have a rather broad energy distribution. Higher D(Li+) values have been measured in amorphous Li1+xV3O8, this being in agreement with its higher rate capability. The different electrochemical behavior of the two forms have been explained on the basis of structural information obtained by FTIR and X-ray absorption spectroscopy (XAS). These have shown, in particular, that the V-O distances are more homogeneous in the amorphous form and that a partial amorphization occurs in the crystalline form upon Li+ intercalation.