Molecular dynamics simulation of the structure of an ion-conducting PEO-based solid polymer electrolyte

Proton-conducting solid polymer electrolyte containing poly(ethylene oxide) sulfonic acid anions (PEO) cations and 35 wt% of water is constructed by atomistic molecular modelling. The structure of the PEO sulfonic acid anions and PEO was studied by calculating the dihedral angle distributions, intramolecular pair correlation functions between the carbon atoms and ether oxygen atoms and by performing the conformational triads population analysis and dimension analysis. The results were compared with the results obtained for similar non-conducting systems and for the system containing only one PEO sulfonic acid anion in water. Some differences were found in the structures. However, the differences in the structures of the polymers were not able to explain the conductivity behaviour of the systems. Instantaneous coordination of cations was studied to get a detailed view of the local environment of the cations. The local environment of the cations shows many variations in the studied systems. Small microphase separation in the conducting system was found.