Relaxation processes in the ns time regime in deuterated pure PEO and two different concentrations of PEO-LiTFSI electrolytes show a stretched exponential behavior identifiable with translational motions of the chain segments. The time scale of the dynamics is slowed by factors of 3 and 10 as a result of adding lithium salt at EO:Li concentrations of 7.5 and 3, respectively, presumably due to the increased rigidity of the lattice caused by inter- and intrachain cross-linking by the Li ions. At the same time the stretching parameter is reduced by 35% and 50%, respectively. Measurements of the Q dependence show that both the relaxation time and the stretching parameter have a positive correlation with S(Q).