Regulating porous structure of coal-derived carbon materials by a dual-activation for high performance supercapacitors

Porous carbon plays an important role in supercapacitors with its favorable electrical conductivity, highly porous structure and superior chemical stability. However, the deep and tortuous ultramicropores in porous carbon greatly restricts the transport and transfer of electrolyte ions, resulting in the inferior electrochemical performance. Therefore, we propose a facile and green chemical activation method that uses KHCO3 and Zn(CH3COO)2·2H2O as dual activators to modulate the porous carbon structure. The synergistic activation between KHCO3 and Zn(CH3COO)2·2H2O endows the obtained porous carbons with hierarchical porous structure, honeycomb-like morphology and large specific surface area (1282 m2 g−1). In the three-electrode system, the optimal sample displays superior rate performance (70 % capacitance retention @ 50 A g−1) and high specific capacitance (321 F g−1 @ 1 A g−1). Symmetric two-electrode configurations were tested in 6 M KOH electrolyte, splendid cycling stability was observed (100 % capacity maintained after 10,000 cycles at 5 A g−1). Moreover, the symmetric supercapacitor assembled with neat EMIM BF4 as the electrolyte reveals a high energy density of 33 Wh kg−1 @ 624.6 W kg−1. This work offers new insights to manipulate the morphology and pore structure of coal-derived porous carbon for high performance supercapacitor electrode.