CoFe₂O₄ nanoparticles as a bifunctional agent on activated porous carbon for battery-type asymmetrical supercapacitor

The low performance of electrode materials is the main obstacle limiting the development of the supercapacitor industry, which can be solved by doping cobalt ferrate nanoparticles (NPs) with carbon materials. Herein, the composites of CoFe₂O₄ based on activated carbon (AC) were successfully prepared using a one-step solvothermal method and subsequently applied in anodes of battery-type asymmetrical supercapacitors. The effect of solvothermal temperature and heating time on the composite characteristic was systematically evaluated. The electrochemical analysis in the three-electrode system revealed that modified activated carbon heated at 140 °C for 24 h (140MAC24) displayed excellent specific capacitance of 571.36 F/g at the current density of 0.2 A/g due to the synergistic effect of the double-layer and faradic capacitance. Moreover, iron and cobalt elements in CoFe₂O₄ could change into the oxide form to accelerate charge in potential range window of-1.0 to-0.2 V and discharge from-0.2 to 0.2 V, respectively. Meanwhile, the result of assessing economic feasibility suggested the splendid availability of 140MAC24 electrodes. Additionally, the assembled supercapacitor displayed the outstanding specific capacitance of 171.31 F/g in the potential window of 1.8 V, energy density of 43.5 Wh/kg at the current density of 0.2 A/g, and capacitance retention rate of 82.49% after 10,000 cycles. The excellent electrochemical properties demonstrated that CoFe₂O₄ could be used as a bifunctional agent for enhancing supercapacitive performance.