Structural changes of Nb2O5 and V2O5 as rechargeable cathodes for lithium battery

The structural changes of T-Nb₂O₅ and V₂O₅ cathodes with discharge and recharge were investigated by X-ray photoelectron spectroscopy (ESCA) and X-ray diffractometory etc.ESCA spectra of the discharge products shows that M⁵⁺ is reduced to a lower valence state such as M⁴⁺ on the discharge, and the chemical bond between Li⁺ inserted into the oxide and O^2? of the oxide exhibits a higher ionic character than that of Li₂O. X-ray diffraction measurement shows that T-Nb₂O₅ gives the reversible structural change accompanying the disorder and order of the atomic arrangement on the charge-discharge cycling. On the other hand, V₂O₅ takes two discharge steps, within the 1st step of which it gives the reversible lattice change along b-axis caused by the intercalation of Li⁺ into the oxide layer, whereas within the 2nd step it is considered that the reaction in the charge-discharge takes place in the vicinity of the surface of the oxide particle. In both oxides, ternary phases such as Li_xM₂O₅ are produced as discharge products, where x is at least 2 for Nb₂O₅ and x is at least 3 for V₂O₅.