Thermal and Electrical Properties of High-Temperature Proton-Conducting Cellulose Nanofibers Swollen with Protic Ionic Liquid

An attempt to obtain solid-state polymer electrolytes based on cellulose nanofibers (CNF) swollen with a protic ionic liquid (PIL) was successful. We extended previous studies of nanocomposites based on proton-conducting cellulose, and instead of imidazole (Im), we used 1-methylimidazolium bis(trifluoromethylsulfonyl)imide as a conductive filler. We present two manufactured composites with different PIL contents, of which we used the CNF-Im nanocomposite as the base material. The obtained cellulose/PIL composites have demonstrated the highest thermal stability thus far, reaching up to 250 °C. At 220 °C, one of the CNF-Im/PIL composites has a maximum conductivity of 1.3 × 10–1 S/m. That means it is the first cellulose-based composite that exhibits such high ionic conductivity over a high-temperature range under anhydrous conditions.