A review on carbon material-metal oxide-conducting polymer and ionic liquid as electrode materials for energy storage in supercapacitors

In recent years, supercapacitors have gained importance as electrochemical energy storage devices. Those are attracting a lot of attention because of their excellent properties, such as fast charge/discharge, excellent cycle stability, and high energy/power density, which are suitable for many applications. Further development and innovation of these devices depend on the production of suitable, inexpensive, environmentally friendly, and widely available materials for use as active materials in electrodes and electrolytes. Different materials (such as activated carbon, metal oxides, graphene, conducting polymers, and ionic liquids) have recently been used to fabricate powerful symmetric or asymmetric supercapacitor electrodes. This paper presents the advantages and disadvantages as well as the electrochemical parameters of different electrodes based on a detailed literature review. The focus is particularly on ionic liquids, which are used as electrode materials. Finally, the future development and perspectives of supercapacitors based on ionic liquids are discussed.