All-solid state supercapacitors operating at 3.5 V by using ionic liquid based polymer electrolytes

Abstract

All-solid state supercapacitors (SCs) using Ionic Liquid based Polymer Electrolyte (IL-b-PE) and activated carbon were assembled and characterized electrochemically. IL-b-PE consisted of a binary blend of a polymeric ionic liquid (PIL), poly(diallyldimethylammonium) bis(trifluoromethanesulfonyl)imide (pDADMATFSI), and their corresponding ionic liquid (IL), N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR14TFSI) in a ratio of 40:60,w/w respectively. Assembling of supercapacitors simply consists of facing two impregnated electrodes without the need of additional separator. Several all-solid state SCs with impregnation ratios (IL-b-PE mass/active material mass) ranging from 5 to 18 were characterized. An all-solid state SC with impregnation ratio of 7 showed the best performance with specific capacitance (Cam) and real energy (Ereal) of 100 F g−1 and 32 Wh kg−1, respectively. After increasing temperatures to 60 °C, the performance of SCs further improved exhibiting Ereal values of 42 Wh kg−1 at 1 mA cm−2. These figures of merit are only slightly lower than those obtained for convectional SCs using pure PYR14TFS and much higher as compared with other solid SCs based on conventional polymer electrolytes. This is mainly due to the high electrochemical stability of this IL-b-PE that allows these solid SCs to operate at maximum voltages as high as 3.5 V for the first time.