Solvation-Site and Dielectric Control of Ion Conduction in Polymer Electrolytes

Solid polymer electrolytes have the promise of improving safety and performance in energy storage devices. Metal cation-containing polymers provide a path to effective electrolytes, with dynamic metal-ligand interactions allowing mechanical properties and ionic conductivity to be widely and separately tuned. A modular synthetic platform based on thiol-ene click chemistry is presented that allows polymers to be post-functionalized with a variety of metal-binding ligands. This well-controlled model system has enabled the study of factors known or suspected to influence ionic conductivity, including segmental dynamics, dielectric constant, solvation site density, and ligand identity. Design rules based on this model platform have been developed by combining experimental results with field-theory–based simulations. The results underscore that low dielectric constant is not necessarily detrimental to ionic conductivity, especially in systems where the resulting ion aggregates form percolating domains.