Study of Li1+xV3O8 by band structure calculations and spectroscopies

In order to precisely characterize the charge transfer during lithium insertion in the title compound, electronic structure calculations and spectroscopies in the X-ray range (XAS, EELS and XPS) have been combined. The good convergence between calculations and experimental data, especially the XAS ones, proves the validity of the calculations. EELS experiment proves that oxygen orbitals are clearly taking part in the charge transfer. The changes occurring in the chemical bond have been analyzed and demonstrate a clear increase in the ionicity of the V-O bond upon lithium insertion. XPS results show the coexistence, for some lithium contents, of three different vanadium oxidation state and the proportions of these oxidation states do not follow a classical reduction process. These experimental results are explained by the electronic structure calculations, in considering the three different non-equivalent atomic positions of vanadium, which do not behave the same way versus the electron transfer. (c) 2006 Elsevier Ltd. All rights reserved.