Dynamic heterogeneity in polymer electrolytes. Comparison between QENS data and MD simulations

We have investigated the dynamics of poly(ethylene oxide) (PEO) lithium-based salt electrolytes (PEO-LiBETI) using quasi-elastic neutron scattering (QENS). Measurements were carried out on the spectrometer NEAT (HMI, Berlin) above the melting temperature of PEO (T_m˜65°C). The experimental data fully support the Molecular Dynamics (MD)-derived model of a heterogeneous dynamics in dilute PEO-salt electrolytes. In agreement with MD simulations carried out on PEO-LiPF₆, we find evidences for the existence of two dynamic processes: (a) a faster process that is described in terms of the pure PEO dynamics and (b) a second component which we identify with the slower motion of the PEO chains involved in PEO-Li⁺ complexes. At this stage, due to the differences in PEO molecular weight and the anion chemical nature, the agreement with MD simulations is qualitative. © 2001 Elsevier Science B.V.