Poly(Ionic Liquid)-Based Composite Electrolyte Membranes: Additive Effect of Silica Nanofibers on Their Properties

Poly(ionic liquids) (PILs) show great promise as a new class of solid electrolytes for energy applications, including high-temperature polymer electrolyte fuel cells, owing to their combination of the unique electrochemical properties of ionic liquids and macromolecular architecture. In this study, we prepared and characterized PIL-based composite polymer electrolyte membranes containing silica nanofibers (SiO₂NFs). The SiO₂NFs were prepared via electrospinning, followed by calcination, and were used as a thermally and mechanically stable, porous substrate. The crosslinked protic PIL was synthesized via in situ radical polymerization of imidazolium hydrogensulfate-based reagents (one monomer and one crosslinker). It was then used as the membrane matrix. The prepared freestanding PIL membranes remained thermally stable at temperatures of up to 180 °C. Furthermore, the PIL/SiO₂NF composite electrolyte membranes demonstrated improved mechanical properties due to reinforcement by the NF framework. These composite membranes also exhibited relatively high proton conductivity (approximately 0.1 to 1 mS/cm) in the 100-150 °C temperature range.