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Keywords:

  • supercapacitors;
  • energy density;
  • porous carbon;
  • graphene;
  • ionic liquids

Abstract

As electrical energy storage and delivery devices, carbon-based electrical double-layer capacitors (EDLCs) have attracted much attention for advancing the energy-efficient economy. Conventional methods for activated carbon (AC) synthesis offer limited control of their surface area and porosity, which results in a typical specific capacitance of 70–120 F g−1 in commercial EDLCs based on organic electrolytes and ionic liquids (ILs). Additionally, typical ACs produced from natural precursors suffer from the significant variation of their properties, which is detrimental for EDLC use in automotive applications. A novel method for AC synthesis for EDLCs is proposed. This method is based on direct activation of synthetic polymers. The proposed procedure allowed us to produce ACs with ultrahigh specific surface area of up to 3432 m2 g−1 and volume of 0.5–4 nm pores up to 2.39 cm3 g−1. The application of the produced carbons in EDLCs based on IL electrolyte showed specific capacitance approaching 300 F g−1, which is unprecedented for carbon materials, and 5–8% performance improvement after 10 000 charge–discharge cycles at the very high current density of 10 A g−1. The remarkable characteristics of the produced materials and the capability of the fabricated EDLCs to operate safely in a wide electrochemical window at elevated temperatures, suggest that the proposed synthesis route offers excellent potential for large-scale material production for EDLC use in electric vehicles and industrial applications.