Molecular dynamics simulation of the polymer electrolyte poly(ethyleneoxide)∕LiClO4. I. Structural properties

Abstract

Molecular dynamics (MD) simulations of poly(ethylene oxide) (PEO)∕LiClO4 polymer electrolyte have been performed for three different salt concentrations (oxygen atoms of polymer to Li+ cations ratio of 31:1, 16:1, and 8:1) and two temperatures (373 and 500K). A united atom model, in which hydrogen atoms are not considered, has been used for PEO. The PEO model has been validated by comparing the static structure factor S(k) calculated by MD simulations of pure PEO at 363K (32 PEO chains with a molecular weight of 1174) with previous experimental data obtained by neutron scattering spectroscopy. A low wave-vector peak develops in the calculated S(k) when LiClO4 is added in the polymeric matrix, which indicates an extended-range order in PEO∕LiClO4 melts. Contact ionic pairs are observed, which are favored as temperature increases. PEO chain as a whole becomes less extended (smaller radius of gyration) upon addition of LiClO4. Radius of gyration increases with temperature at low salt concentration, but it is only marginally affected by temperature at high concentration.