Protic Poly(Ionic Liquid)/Ionic Liquid Ionogel Electrolyte Sharing the Same Ionic Species for Supercapacitors

Protic ionic liquids are promising to construct proton conductive ionogels, but aprotic polymer frameworks as supports of ionogels deteriorate proton conductivity. Herein, a novel protic ionogel, which is composed of protic poly ionic liquid and ionic liquid sharing the same ionic species, is proposed as a highly conductive and stable electrolyte for supercapacitors. The ionogel is conveniently synthesized by in situ copolymerization of protic 1-vinylimidazolium hydrogen sulfate and bis-vinylimidazolium hydrogen sulfate in protic 1-methylimidazolium hydrogen sulfate. Because the resultant poly ionic liquid network shares the same protic ionic species with the ionic liquid, the ionogel exhibits a high conductivity of 14 mS cm–1 at 140 °C. The ionogel-based supercapacitors constructed from polyaniline and carbon nanotube electrodes deliver a maximum specific capacitance of 1132 mF cm–2 and 96% capacitance retention after 10 000 charge–discharge cycles at 140 °C, respectively. The protic poly ionic liquid/ionic liquid ionogel sharing the same ionic species provides an effective strategy to develop soft proton conductors for high-performance electrochemical devices.