Fast Li-Ion Dynamics in Stoichiometric Li2S-Ga2Se3-GeSe2 Glasses

The temperature dependence of Li-ion transport is explored in novel stoichiometric chalcogenide glasses in the ternary system Li2S-Ga2Se3-GeSe2 using electrochemical impedance spectroscopy (EIS) and Li-7 nuclear magnetic resonance (NMR) spectroscopy. The dc conductivity in these glasses monotonically increases with Li2S content with the highest room-temperature conductivity being similar to 10(-4) S/cm in the glass of composition: 50% Li2S-10% Ga2Se3-40% GeSe2 with an activation energy of 0.37 eV. Analysis of the Li-7 NMR central transition line shape reveals that Li ions are randomly distributed in the structure of these glasses and their rapid hopping transport is responsible for the electrical conductivity. The excellent agreement between the experimentally measured dc conductivity and that calculated from the Li-ion hopping frequency obtained from EIS and NMR implies that the ionic transference number in all glasses is close to unity and these glasses behave as strong electrolytes.