Bean dregs-based activated carbon/copper ion supercapacitors

Bean dregs-based activated carbon/copper ion redox active electrolytes supercapacitors (BDACCIS) were prepared by combining bean dregs-based activated carbon with copper ion redox active electrolytes, which were prepared by introducing NH₄NO₃ (NN) auxiliary electrolytes into Cu(NO₃)₂ (CN) solutions. The physical properties of obtained activated carbon materials are characterized by scanning electron microscopy, powder X-ray diffraction, nitrogen adsorption/desorption isotherm measurements. The electrochemical properties of the constructed supercapacitor are studied by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and cycle life tests. The bean dregs-based activated carbon materials exhibit interestingly well-interconnected porous structure with the large specific surface area of 2905 m² g⁻¹. As-prepared BDACCIS presents a high specific capacitance (492 F g⁻¹ at 1 A g⁻¹) and high rate performance (285 F g⁻¹ at 20 A g⁻¹). Simultaneously, it also shows the low equivalent series resistance (R_s) and charge-transfer resistance (R_ct) of 1.05 and 0.75 Ω, considerable energy and power densities of 51.3 W h kg⁻¹and 855.1 W kg⁻¹, and satisfactory cycling stability with 81.4% capacitance retention after 10000 cycles at 1 A g⁻¹ in 2 M CN + NN redox active electrolyte, demonstrating that the BDACCIS would be a promising supercapacitor.