Towards compatible natural resources-derived carbon electrodes with safer electrolytes for supercapacitors

The growing interest for energy storage devices, both batteries and capacitors, pushes to-17 wards improving electrochemical properties such as extended charge/discharge cycles, high specific 18 capacitance, and power density. Furthermore, the use of easily available raw materials for the pro-19 duction of carbon electrodes arouses interest due to the criticality of the resources related to the 20 current technologies for the high performance capacitors. The present article reviews carbon-21 based materials for supercapacitors having appropriate characteristics in terms of specific surface 22 area, electrical conductivity and charge/discharge stability but coming from affordable coal deposits 23 or crop waste. In addition, the substitution of organic liquids electrolytes with less dangerous solu-24 tions, such as aqueous electrolytes containing high salt concentration, is a valuable strategy dis-25 cussed herein for the design of green devices. Finally, the present article reviews the electrochemical 26 performance of supercapacitors based on carbon electrodes obtained from various natural resources 27 and their compatibility with safer and cheaper electrolytes.