7Li and 51V NMR study on Li+ ionic diffusion in lithium intercalated LixV2O5

LixV2O5 (0.4 < x < 1.4) prepared by solid-state reaction were studied by 7Li and 51V NMR spectroscopy. 7Li NMR spectra showed a narrowing of the line width in relation to Li+ionic diffusion. Analysis of LixV2O5 using a Debye-type relaxation model showed a low activation energy ∼0.07 eV in the sample of x = 0.4 below room temperature, and revealed a Li+ionic diffusion with larger activation energy ∼0.5 eV above 450 K in lithium-rich samples. The latter is ascribed to the existence of a multi-phase system comprising stable ɛ- and γ-phases, resulting from complicated phase transitions at high temperature. These shapes and shifts enable the classification of the β-, ɛ-, δ-, and γ-phases. The ionic diffusion of Li+ ions is discussed in relation to the complicated phase transitions.