Graphene-Based Supercapacitors Using Eutectic Ionic Liquid Mixture Electrolyte

Compact graphene films were prepared and electrochemically tested at various temperatures in a eutectic of ionic liquid mixture (1: 1 by weight or mole N-methyl-N-propylpiperidinium bis (fluorosulfonyl) imide and N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl) imide) electrolyte. A large temperature window from -30 degrees C to 80 degrees C was achieved together with a large potential window of 3.5 V at room temperature and below. A maximum gravimetric capacitance of 175 F.g(-1) (85 mAh.g(-1)) was obtained at 80 degrees C. 130 F.g(-1) (63 mAh.g(-1)) and 100 F.g(-1) (49 mAh.g(-1)) were still delivered at -20 degrees C and -30 degrees C respectively. Besides, a volumetric capacitance of 50 F.cm(-3) was achieved with a thick graphene film (60 mm). The outstanding performance of such compact graphene film in the eutectic ionic liquid mixture electrolyte makes it a promising alternative to activated carbon for supercapacitor applications, especially under extreme temperature conditions. (c) 2016 Published by Elsevier Ltd.