Ion States Impact Charge Transport and Dielectric Constant for Poly(ethylene oxide)-Based Sulfonylimide Lithium Ionomers

Understanding dielectric response and charge transportin ion-containingpolymers is essential for the design and implementation of these materialsin energy-related applications. Our previous study identified thesignificant impacts of anion chemical composition on ion conductionfor poly(ethylene oxide)-based lithium ionomers with polymer-fixedsulfonylimide (MTLi) and sulfonate anions (J. Mater. Chem.C, 2022, 10, 14569). In thisstudy, we further explore the dielectric response and Li+ conduction in the context of different ion states using DFT. Themost relevant ion states impacting the dielectric response and Li+ conduction are represented with a four-state model. DFT calculationusing the cluster-continuum solvation model captures the local solvationeffects of poly(ethylene oxide) and reveals low cluster dissociationenergy between neutral and charged states. Low cluster dissociationenergy explains the weakly aggregated morphology with low aggregationnumber based on X-ray scattering and implies that Li+ rapidlyexchanges between different ion states. Consequently, Li+ can hop along aggregates for high ion content MTLi, which resultsin its significant dielectric response, comparable conductivity, andlower Haven ratio despite stronger aggregation than the low ion contentcounterparts. Different from typical ionomers where raising ion contentis detrimental to the ion transport and dielectric response, the understandingsbased on different ion states for MTLi offer new insights to promoteion conduction and dielectric response for single-ion conducting ionomers.

Automated summary

Understanding the dielectric response and charge transport in ion-containing polymers is crucial for their application in energy-related fields. In this study, the impact of anion chemical composition on ion conduction in poly(ethylene oxide)-based lithium ionomers was investigated using a four-state model. DFT calculations with the cluster-continuum solvation model revealed low cluster dissociation energy and explained the weakly aggregated morphology, indicating rapid exchange of Li+ between different ion states. These findings offer new insights for promoting ion conduction and dielectric response in single-ion conducting ionomers.