Eco-friendly choline acetate/propionate ionic liquids as novel green electrolytes for high performance supercapacitors

Ionic liquids (ILs) stand out due to the characteristic negligible vapor pressure and molecular design ability, along with several intriguing features like a highly ionized environment, good thermal/chemical stability, and universal solubility/affinity, to satisfy the high-energy request for creating better supercapacitors (SCs). In this context, the ILs of choline acetate ([Ch]Ac) and choline propionate ([Ch]Pr) were synthesized. In the ambient temperature, significant features including viscosity, and electrochemical tests were investigated. The SCs with choline-based ILs electrolytes display exceptional electrochemical stability at a maximum voltage of up to 3.9 V. At room temperature, the specific capacitance of the electrolyte containing IL [Ch]Ac was obtained to 106.52 F/g with an energy density of 47.93 Wh/kg and power density of 450 W/kg at 1 A/g. In addition, the SC made using IL [Ch]Ac retained 90.94% of its capacity up to 3000 cycles at 2 A/g. The findings have significant ramifications for extending the use of eco-friendly, non-toxic, and affordable electrolytes for high-performance SCs with broad voltage windows and improved longevity.