Influence of polarizability on the ion transport mechanism of polymeric ionic liquid*

In the current study, we compared the prediction of three different implementations of force field, namely, the original full partial charge system, the scaled partial charge system and the Drude oscillator polarizable force field on the structural and dynamic properties of poly(1-butyl-3-methyl-imidazolium hexafluorophosphate) by atomistic simulations. We found that both the scaled and the polarizable force field models are comparable in prediction of structural and dynamic properties, although the scaled charge model artificially lowers the first-neighbor peak of the radial distribution function and therefore leads to a slight reduction in density. The full charge model is not suitable for prediction of the dynamic properties, but it could reproduce the structural properties. With the refined analysis method for the ion hopping mechanism, we found that all three methods could produce very similar conclusions, namely that the mobile anion is naturally associated with three cations from two distinct polymer chains, and the fraction of inter- and intra-molecular hopping events are comparable.