Pyrrolidinium-based polymeric ionic liquids as mechanically and electrochemically stable polymer electrolytes

A new family of polymeric ionic liquids having pyrrolidinium cation pendant units was synthesized from commercially available poly(diallyldimethylammonium) chloride. A simple anion exchange procedure was applied to the poly(diallyldimethylammonium) chloride using different salts such as LiTFSI, KPF6, LiBF4 and NaDBSA. The anion exchange reaction was quantitative as confirmed by NMR, FT-IR and titration experiments. Among these polymers, poly(diallyldimethylammonium) bis(trifluoromethanesulfonyl)imide (TFSI) showed excellent performance as polymer matrix for polymer electrolyte compositions together with pyrrolidinium ionic liquid and lithium salt having a similar TFSI counter-anion. In this sense, free standing mechanically stable transparent polymer films showing an ionic conductivity higher than 10−4 S cm−1 at room temperature were prepared and characterized. Furthermore, the polymer electrolytes presented a wide electrochemical stability window (7.0 V) which makes them interesting candidates for solid-state lithium batteries.