Computational Investigation on the Effect of Alumina Hydration on Lithium Ion Mobility in Poly(ethylene oxide) LiClO4 Electrolytes

Improving ionic conductivity and lithium ion mobility in polymer electrolytes is important for their practical use for polymer electrolytes. In this study, a combination of molecular dynamics and Monte Carlo simulations were used to bring insight into lithium ion transport in poly(ethylene oxide) LiClO4 polymer electrolytes next to both acidic and basic treated model alumina solid surfaces at 323, 348, and 373 K. The acidic treated system had hydrogens present on its surface, while the basic treated system did not. The results found reduced ion mobility near the surfaces and little change to overall conductivity away from the surface. However, ion diffusion was somewhat enhanced for the acidic treated system at 323 K in comparison with systems without any surface present, despite that close to the surface it was reduced. This was linked to long-ranged structural ordering of ions in the system brought on by strong interactions with the surface, which resulted in oscillations in lithium and ClO4- densities that were out of phase, reducing ion binding and enhancing diffusivities.