Molecular Dynamics Simulations of Poly(ethylene oxide)/LiI Melts. 1. Structural and Conformational Properties

Abstract

Molecular dynamics (MD) simulations of PEO/LiI melts at 363 and 450 K for the ether oxygen (EO)/LiI compositions 48:1, 15:1, and 5:1 have been performed. An explicit atom quantum-chemistry-based force field developed in our previous work was used. The Li+ cation environment from our MD simulations was found to be in good agreement with neutron diffraction isotopic substitution (NDIS) experiments performed on the EO/Li = 5:1 system. Cation complexation was found to be strongly temperature dependent. The Li+ cations have a tendency to be coordinated by six or more contiguous EO from a single chain at the lower temperature (363 K), but as temperature increases, coordination by shorter contiguous ether oxygen atom sequences becomes increasingly probable. The number of “free” ions was found to decrease with increasing temperature, consistent with results from Raman spectroscopy experiments on similar polymer electrolyte systems. The strong temperature dependence of the cation environment indicates the importan...