Hydrothermal and peat-derived carbons as electrode materials for high-efficient electrical double-layer capacitors

Different micro–mesoporous carbons derived from d -glucose (GDC), granulated white sugar (WSDC) and highly decomposed Estonian peat (PDC) were synthesized using hydrothermal carbonization and direct activation methods. The resulting carbonaceous materials were activated using chemical (KOH and ZnCl 2 ) and physical (CO 2 ) activation methods. The electrochemical characteristics of the electrical double-layer capacitors (EDLCs) based on 1 M Et 3 MeNBF 4 solution in acetonitrile and EtMeImBF 4 were measured using two-electrode cells. The EDLCs assembled had specific capacitances from 20 up to 158 ± 18 F g −1 (in EtMeImBF 4 ) and phase angle values from − 65° to − 88° (at low frequencies). The characteristic time constant values vary more than 10 times. Applying constant power discharge method, very high energy and power densities (34 W h kg −1 at 10 kW kg −1 ) for activated carbon powders-based EDLCs have been measured. Fitting of impedance data showed that enhanced mesoporosity reduces the adsorption and mass-transfer resistance values. Graphic abstract