Molecular dynamics simulation of lithium ion mobility in a PEO surface

A model for a poly(ethylene oxide) (PEO) host polymer surface, which was developed earlier, is exploited to probe the ionic distribution for Li+ and Cl− ions in the PEO surface for an effective composition LiCl·(PEO)213 at 400 K. The local structural situation around the Li+ ions was analyzed specifically. Two general situations are observed: Li+ ions lying deeper into the bulk tend to be associated with one Cl− and two oxygens; nearer the surface, they coordinate five ether oxygens belonging to the same PEO chain. The ratio between the two cases (Cl−+2O:5O) moves smoothly from ca. 30:70 in the bulk to ca. 45:55 in the surface region.