Ion-Conducting PolymersBased on Photocurable AcrylicNetworks: The Role of Sulfur-Based Moieties

In this work, the synthesis and in-depth characterization of three sets of ultraviolet (UV)-curable diacrylate poly­(ethylene glycol) (PEG) monomers containing sulfide/thioether, sulfoxide–sulfone, and methyl sulfonium groups are reported. Three series of solid polymer electrolytes are obtained by photopolymerization of each diacrylate monomer incorporating lithium bis­(fluorosulfonyl) imide (LiFSI). The effect of the polymeric nature on the ionic conductivity was investigated. All polymer electrolytes exhibit an electrochemical stability of up to 4 V vs Li⁺/Li. This is extended to 4.3 V vs Li⁺/Li in polymer-containing methyl sulfonium groups, which possess the highest ionic conductivity (2·10^–4 S cm^–1 at 70 °C) and lowest plating–stripping overpotentials (≈0.1 V vs Li⁺/Li). However, polymer electrolytes containing thioether groups show not only high ionic conductivity but also oxidation in sulfoxide/sulfone between 4 and 4.5 V vs Li⁺/Li. The polymer electrolyte containing sulfoxide–sulfone moieties highlights the lowest ionic conductivity and poorest Li interfacial stability. This work provides useful insights into sulfur-containing solid polymer electrolytes for high-performance lithium batteries and energy storage devices.