Building towards Supercapacitors with Safer Electrolytes and Carbon Electrodes from Natural Resources

The growing interest in energy storage devices, both batteries and capacitors, could lead to the improvement of electrochemical properties such as extended charge/discharge cycles, high specific capacitance, and power density. Furthermore, the use of easily available raw materials for the production of carbon electrodes has attracted interest due to the criticality of the resources related to the current technologies of high-performance capacitors. The present article reviews carbon-based materials for supercapacitors derived from affordable coal deposits or crop waste with appropriate characteristics in terms of specific surface area, electrical conductivity, and charge/discharge stability. In addition, the substitution of organic liquids electrolytes with less dangerous solutions, such as aqueous electrolytes containing high concentrations of salt, is a valuable strategy for the design of green devices that is discussed in this review. Finally, the present article reviews the electrochemical performance of supercapacitors based on carbon electrodes obtained from various natural resources and their compatibility with safer and cheaper electrolytes.