Redox additive/active electrolytes: a novel approach to enhance the performance of supercapacitors

Currently, supercapacitors (SCs) are a promising field in the area of energy storage devices. In the last few decades, different types of carbon based materials with suitable surface modifications, metal oxides, metal hydroxides, conducting polymers and their various composites have been used as electrodes to improve the energy performance of SCs. In addition, different technologies like asymmetric and hybrid systems have also been introduced. Interestingly, another alternative approach has been proposed recently by a few research groups, wherein electrolytes (liquid and polymer) can enhance the performance of the SCs via redox reactions at the electrode–electrolyte interface, by introducing redox additives or mediators in the electrolytes. The main advantage of this new technique is its simple and safe preparation method, along with cost effectiveness compared to the preparation of some active electrode materials. Hence it is believed that identification of suitable redox additives or species in electrolytes will be a hotspot in the field of SCs in the coming years.