Li <sup>+</sup> Conduction in Glass-Forming Single-Ion Conducting Polymer Electrolytes with and without Ion Clusters
Jiacheng Liu, Jennifer L. Schaefer
Abstract
Single-ion conducting polymer electrolytes have been studied for their advantages for rechargeable battery applications. However, amorphous poly(ethylene oxide) (PEO) and related electrolytes are limited by their ion transport rate that is coupled with −EO– segmental motion. Simulations have suggested that fast ion transport may occur within the ion clusters in polymer electrolytes. In this contribution, we report on single-ion conducting polymers with varying polymer backbone types that contain delocalized tethered anions (−sulfonyl(trifluoromethylsulfonyl)imide (−TFSI – )). The homopolymers were prepared from side-chain monomers capable of free-radical polymerization. The polymer backbone type is found to have strong implications for ion aggregation and nanoscale morphology. A new side-chain ionic polymer with a nonpolar backbone (polystyrene derivative) is found to self-assemble with lamellar ordering of nanoscale ionic domains. Meanwhile, side-chain ionic polymers with polar backbones (polyacrylate and polymethacrylate derivatives) are found to be less ordered. We show that regardless of the ion aggregation morphology, the bulk ionic conductivity is related to the ionic group relaxation although there are varying degrees of decoupling between thermal glass transition and dielectric relaxation.