The exponential Lipari Szabo decay assumes normal translational diffusion and a random orientation of the local environment with respect to the magnetic field. This assumption holds for glasses or polymer solutions which have a random distribution of environments either due to the amorphous nature of the material or due to the tumbling motion of the polymer in a liquid . In an ideal liquid with fast diffusion, the stretching factor is 1.0, and the exponential decays to 0. However, in complex solids, some memory of previous sites may be retained during the decay and averaging might not be complete, and therefore the exponential decays to a constant value and < 1 occurs e.g. for cases of subdiffusion as in a diffusion-trap model . From the SAE decay time, ⌧ SAE , the effective Li hopping rate is then given by ⌧ 1 SAE .