Ionic liquid-based electrolyte in supercapacitors

As the number of industries and people around the globe continues to rise, so do energy demands, necessitating the use of renewable energy sources. One of the long-term energy storage devices being developed by participants in the competition is a supercapacitor with a high power density and an extended life cycle. To expand the applications of supercapacitors, however, a greater energy capacity is required, necessitating the development of high-performance, secure, and environmentally favorable supercapacitors. Ionic liquids (ILs) can be used as electrolytes due to the presence of organic cations and anions, as well as their excellent ionic conductivity, strong temperature stability, and broad potential window. Consequently, ILs can be used as electrolytes in supercapacitors, enabling them to store more energy while remaining safe to use. Electrolytes serve as an insulator between positive and negative electrodes and conduct electricity by transporting ions. However, ILs have a high viscosity, which could be an advantage because they can be solid electrolytes, allowing supercapacitors to be widely used in promising energy storage systems with specific energy as high as 710.526 Wh.kg-1, specific power as high as 51000 W.kg-1, and an operating voltage as high as 3.4 V. This paper will discuss the performance of ILs as electrolytes in supercapacitors, the various types of ILs as electrolytes, and the outlook for the development of supercapacitors.