Activated graphene oxide/reduced graphene oxide electrodes and low viscous sulfonium cation based ionic liquid incorporated flexible gel polymer electrolyte for high rate supercapacitors

Abstract

High rate performance of symmetrical electrical-double layer capacitors (EDLCs) constructed with activated graphene oxide (ac-GO)/activated reduced graphene oxide (ac-RGO) electrodes and ionic liquid (triethylsulfonium bis(trifluoromethylsulfonyl)imide, incorporated plastic crystal succinonitrile (SN) based flexible gel polymer electrolytes (GPE) have been reported. The 3D architecture with predominantly meso-porous character of the ac-RGO, in combination with SN-based high ion conducting GPE, renders it a high rate electrode with high value of knee frequency, fk (∼966 Hz), low response time τ0 (∼20 ms) and high pulse power P0 (∼111 kW kg−1) as compared to the ac-GO-electrode that exhibits the corresponding values: fk (∼215 Hz), τ0 (∼60 ms) and P0 (∼58 kW kg−1). The ac-RGO based EDLCs offer higher specific power (∼118 kW kg−1) than that for ac-GO-based EDLC (∼41 kW kg−1), as evaluated from GCD studies. However, due to the additional pseudo-capacitance arising from leftover oxygen functional groups, the ac-GO-electrodes exhibit higher values of specific capacitance and specific energy (∼88–96 F g−1 and 25 Wh kg−1, respectively) as compared to the ac-RGO based EDLCs with specific capacitance ∼66–72 F g−1 and specific energy ∼18 Wh kg−1). Both the EDLC cells exhibit stable capacitive performance up to ∼11,000–13,000 GCD cycles.