Enhanced Li+ Conduction Within Single-Ion Conducting Crosslinked Gel via Reduced Cation-Polymer Interaction

The development of advanced electrolytes compatible with lithium metal and lithium-ion batteries is crucial for meeting ever growing energy storage demands. One such class of materials, single-ion conducting polymer electrolytes (SIPEs), prevents the formation of ion concentration gradients and buildup of anions at the electrode surface, improving performance. One of the ongoing challenges for SIPEs is the development of materials that are conductive enough to compete with liquid electrolytes. Presented herein is a class of gel SIPEs based on crosslinked poly(tetrahydrofuran) diacrylate that present enhanced room temperature conductivities of 3.5 × 10^-5 S/cm when gelled with lithium metal relevant 1,3-dioxolane/dimethoxyethane, 2.5 × 10^-4 S/cm with carbonate solutions, and approaching 10^-3 S/cm with dimethyl sulfoxide. Remarkably, these materials also demonstrate high conductivity at low temperatures, 1.8 × 10^-5 S/cm at -20 °C in certain solvents. Most importantly however, when contrasted with identical SIPEs formulated with poly(ethylene glycol) diacrylate, the mechanisms responsible for the enhanced conductivity are elucidated: decreasing Li⁺-polymer interactions and gel solvent-polymer interactions leads to an increase in Li⁺ mobility, improving the ionic conductivity. These findings are generalizable to various SIPE chemistries, and can therefore be seen as an additional set of design parameters for developing future high conductivity SIPEs.