A kinetic study of the insertion of Li+ ions, into the crystal lattice of materials where x was equal to 0.50 or 0.70, was performed by using current pulse methods. The Li insertion reaction, for both oxides, consisted of 2 main stages. In the first stage, for LixNb1.3V0.7O5 (where x ranged from zero to unity), the chemical diffusion coefficient for Li was found to be of the order of 10-11cm2/s. However, in the second step (where x ranged from 1 to 1.7) the coefficient increased to between 10-9 and 10-10cm2/s. On the other hand, in the case of LixNb1.5V0.5O5 (when x was between 0 and 2), the coefficient was usually of the order of 10-11cm2/s. The self-diffusion coefficient, which was deduced from the chemical diffusion coefficients, was found to be of the order of 10-12cm2/s in both oxides. The Li was inserted into the lattice while maintaining the original arrangement. The largest unit-cell volume (0.9409nm3) was found for Nb1.3V0.7O5, and increases in cell volume (upon Li insertion) were related to a higher Li diffusivity in the lattice.

N.Kumagai, Y.Kikuchi, K.Tanno: Solid State Ionics, 1990, 40-41, 978-81