Tailoring porous carbon from optimized coal blends for high-performance supercapacitor electrodes

Porous carbon was fabricated by carbonization of blended coal in air with the assist of K 2 CO 3 /KCl. K 2 CO 3 -based DES electrolyte was synthesized and assembled supercapacitor exhibited high energy density and wide temperature operating range. • Porous carbon was prepared by carbonization of coal with different rank in air. • Material yield and performance could be regulated by adjusting coal mixing ratio. • The capacitor showed high energy density and wide operating temperature range. In the realm of supercapacitor technology, identifying appropriate precursors and designing a simple method for fabricating porous carbon electrodes pose a significant challenge. This study successfully synthesized porous carbon from blended Naomaohu (NMH) and Heishan (HS) coals with different degrees of metamorphism by utilizing K 2 CO 3 /KCl to assist in carbonization process in air. The carbonization mechanism of the blended coal under air conditions and the flame-retardant and activation mechanisms of the composite salt were elucidated. The properties of the porous carbon materials are contingent upon the type and blend ratio of the two coals. Moreover, K 2 CO 3 was used to prepare deep eutectic solvent (DES) electrolyte, and the symmetric supercapacitor assembled with the fabricated porous carbon and DES electrolyte demonstrates a high energy density (28 Wh kg −1 ) and a broad temperature applicability range (−25 to 120 °C). This work develops a simple and effective approach to preparing porous carbon, and it is anticipated that more varieties of coal can be blended and used to fabricate carbon materials with more diverse compositions and structures, along with excellent electrochemical performance.