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Supercapacitors are energy storage devices that can cleanly and efficiently meet the growing energy demand. The presentwork describes the synthesis of nanoparticles of cobalt ferrite (CoFe2O4) by the combustion method and their use with activated carbon (AC) to manufacture supercapacitors. In order to study the influence of composition on the electrochemical properties, supercapacitors with three different compositions were produced: Fe90 (90% CoFe2O4 and 10% AC), Fe50 (50% CoFe2O4 and 50% AC) and Fe10 (10% CoFe2O4 and 90% AC). Microstructural and morphological analyses were performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electronmicroscopy (TEM), and Raman spectroscopy. Cyclic voltam-metry (CV), galvanostatic charge-discharge (GCD), floating and electrochemical impedance spectroscopy (EIS) tests were performed. XRD, SEM, TEM and Raman results showed that the combustion method was effective for the production of CoFe2O4 nanoparticles. SEM and Raman spectroscopy results showed that the AC has a porous structure and low crystallinity. According to CV, GCD and floating tests, all three supercapacitors presented excellent electrochemical stability. The Fe50 composition yielded the lowest equivalent series resistance, while the Fe10 composition yielded the highest capacitance. The results show that the combination of AC with CoFe2O4 is promising for the use in supercapacitors.

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