Electrochemical Properties of Hybrid Supercapacitor with Nanosized Fe_3O_4/activated Carbon as Electrodes

The supercapacitor using nano-structured Fe_3O_4 and activated carbon(AC)as electrode materials was developed.Fe_3O_4 magnetic nanoparticles with average particle size of 36nm were synthe- sized by microwave method using FeSO_4·7H_2O and ammonia as the precipitator.Three kinds of super- capacitors,Fe_3O_4/KOH/Fe_3O_4,AC/KOH/AC,Fe_3O_4/KOH/AC,were prepared using 6mol/L KOH as electrolyte.Cyclic voltammetry(CV),galvanostatic charge-discharge and electrochemical impedance spectroscopy were used to study the performance of the electrodes and the supercapacitors.The results show that the operating voltage of Fe_3O_4/KOH/AC hybrid supercapacitor is 1.2V.When the current density is 0.2mA/cm~2 and the weight ratio of active materials(Fe_3O_4/AC)is 1.5,the energy density of hybrid supercapacitor is 9.25Wh/kg,which is 53.4% higher than that of AC/KOH/AC capacitor with the same electrolyte.