Influence of nanoparticle surface chemistry on ion transport in polymer nanocomposite electrolytes

• Molecular dynamics simulations are used to study the influence of the surface chemistry on the transport of ions in polymer electrolytes containing Alumina nanoparticles.
• With increasing loading of the nanoparticles, we observed reduced ionic mobilities and conductivities compared to pure PEO melt.
• The observed diffusivities of ionic species correlated well with the polymer segmental dynamics with however quantitative deviations apparent for higher particle loadings.
• Quantitative disparities between ionic mobilities and polymer segmental dynamics were justified by invoking the changes in local environment of ions in the electrolyte.

Using atomistic molecular dynamics simulations, we study the ion diffusivities and conductivities of polyethylene oxide polymer electrolytes doped with LiBF4 salt and containing dispersed Al2O3 nanoparticles. We consider nanoparticles of two different surface chemistries: (a) containing acid rich surface sites (α‐Al2O3); (b) containing roughly equal acidic and basic surface sites (γ‐Al2O3). We compare the ionic diffusivities and conductivities of such systems with our earlier results [Mogurampelly et al. Macromolecules 2015, 48, 2773–2786] for systems containing basic surface sites on the nanoparticles (β‐Al2O3). In the presence of α‐Al2O3 and γ‐Al2O3 nanoparticles, we observe a monotonic decrease of ionic conductivities and mobilities with particle loading. These results are consistent with our earlier findings in the context of β‐Al2O3 nanoparticles. Our analysis identifies that the ionic mobilities and conductivities correlate with the combined effects of the changes in polymer segmental dynamics and the modifications in the local environment of ionic species arising from the introduction of nanoparticles.