Improving battery electrolytes is highly desirable, particularly to increase safety and reduce cost. One class of possible new electrolyte materials is ionomers—polymers with a small number of charged groups covalently bound to the polymer backbone.

A hindrance to high conductivity in ionomer melts is nanoscale ionic clusters that usually form because of the polymer’s low dielectric constant. Understanding these clusters and their effects on material properties is important for improved design.

Recent molecular-dynamics simulations have revealed new details of ion motion in model ionomers. The simulations used a simple, coarse-grained model in order to reach long enough time scales to follow the ion motion. It was found that instead of “hopping” between clusters, as had been believed, the ions move by cluster collisions and rearrangements. Ion motion is thus strongly affected by cluster morphology, which in turn is determined by the underlying molecular architecture of the ionomers.

The simulation results on morphology appeared in the Journal of the American Chemical Society and the dynamics results were just accepted for publication in Macromolecules.

Read the abstract for the Journal of the American Chemical Society article (Macromolecules article is still in press).