Matching of Porous Carbon and Adsorbed Ions for High-Specific-Energy Asymmetric Supercapacitors

Abstract

In order to improve the energy density and stable operating voltage of the supercapacitor, asymmetric supercapacitors (ASCs) are designed utilizing mesoporous carbon (MC) as the anode, activated carbon (AC) as the cathode, and 1 mol kg⁻¹ (1 m) tetraethylammonium tetrafluoroborate/propylene carbonate (TEA-BF₄/PC) as the electrolyte. In ASCs, the MC anode provides broad ion transport channels and significant charge storage capacity for TEA⁺, while the AC cathode, with its large specific surface area, offers numerous adsorption sites for BF₄⁻. Benefiting from the different porous materials matched with adsorbed ions, ASCs significantly enhance the rate performance and high-voltage stability of the device. Electrochemical testing demonstrates that the AC//MC ASCs exhibit an outstanding discharge capacitance of 121 F g⁻¹ at a current density of 0.1 A g⁻¹ at 3.2 V, which is sustained at about 65% at 10 A g⁻¹. Additionally, the device achieves a remarkable energy density of 43.3 Wh kg⁻¹ and largest power density of 7.3 kW kg⁻¹. This work provides theoretical direction for the design of electrode materials and process optimization in high-specific-energy double-layer capacitors.