The techniques of 7Li stimulated-echo nuclear magnetic resonance and classical relaxation nuclear magnetic resonance were used jointly for the first time in a comprehensive investigation of Li diffusion in layer-structured Li0.7TiS2. A single 2-dimensional Li diffusion process was probed over a dynamic range of almost 10 orders of magnitude. This was the widest dynamic range so far directly measured by 7Li nuclear magnetic resonance spectroscopy, without the help of a specific theoretical model. The jump rates were found to obey a strict Arrhenius law,

r (/s) = 6.3 x 10-12 exp[-0.41(eV)/kT]

and ranged from 10-1 to 7.8 x 108/s, at 148 to 510K. Ultra-slow Li jumps in the kHz to sub-Hz range were directly measured by recording 7Li spin-alignment correlation functions. The temperature and frequency dependences of the relaxation rates agreed fully with the results expected for 2-dimensional diffusion.

From Ultraslow to Fast Lithium Diffusion in the 2D Ion Conductor Li0.7TiS2 Probed Directly by Stimulated-Echo NMR and Nuclear Magnetic Relaxation. M.Wilkening, W.Küchler, P.Heitjans: Physical Review Letters, 2006, 97[6], 065901 (3pp)