Quantifying the effects of local structure and dynamics on ion transport in polymer electrolytes

Polymer electrolytes can boost the performance and safety of lithium-ion batteries relative to liquid electrolytes. However, the presence of interfaces between microphase-separated domains can introduce complexities in the local ion transport, as competing effects (e.g., interfacial segmental mixing vs. chain stretching) can increase or decrease local mobility. We present a framework to account for the effects of polymer architecture, segmental mixing, chain stretching, and confinement on the dynamics of poly(oligo-oxyethylene methacrylate) (POEM)-based electrolytes, and we validate this framework through techniques such as nuclear magnetic resonance spectroscopy measurements on solid‑state electrolyte samples. Notably, we found that a mobility-onset temperature that captures the heterogeneous dynamics along the POEM side chain is a better predictor of segmental mobility than the POEM thermal glass transition temperature. Additionally, our framework explains the mobility gradient across nanostructured domains when we combine segmental mixing effects with chain stretching and confinement information, especially at the higher segregation strengths. This quantitative link between local and global dynamics can facilitate the design of next‑generation electrolytes.