In-situ synthesis of SnO2/CoFe2O4/Fe3O4 nanograss array composite: A redox-active electrode material for battery-type supercapacitors

Abstract

Nanocomposites containing mixed transition metal oxides demonstrate significant promise as materials for supercapacitors, specifically due to their enhanced surface area, synergistic effect of multiple metal cations, excellent electrical conductivity, and improved electrochemical properties. In this study, we synthesized a nanocomposite with a nanograss array morphology consisting of SnO2/CoFe2O4/Fe3O4 using an in-situ sol-gel method. For comparison, we synthesized a composite (CoFe2O4/Fe3O4) without SnO2. Through a systematic characterization employing various analytical techniques, we examined the structural, morphological, and textural attributes of the resulting composites. The results reveal that the phase percentages of CoFe2O4, SnO2, and Fe3O4 were 38%, 33%, and 29% in the SnO2/CoFe2O4/Fe3O4 composite. Also, the nanograss array of SnO2/CoFe2O4/Fe3O4 is composed of nano-sized primary particles, while CoFe2O4/Fe3O4 showed spherical-like nanoparticle morphology. The BET surface area of the SnO2/CoFe2O4/Fe3O4 composite was found to be seven times higher than that of CoFe2O4/Fe3O4. We also evaluated the electrochemical performance of the SnO2/CoFe2O4/Fe3O4 composite as a cathode material for battery-type supercapacitors. The synergistic combination of SnO2 and CoFe2O4/Fe3O4 in the SnO2/CoFe2O4/Fe3O4 electrode resulted in a high specific capacity of 465C g−1 at 1 A g−1, which is 2.5 times higher than the CoFe2O4/Fe3O4 electrode. Additionally, the SnO2/CoFe2O4/Fe3O4 electrode exhibited a remarkable rate capability of 87% at 10 A g−1 and excellent cyclic performance with 96% capacity retention after 5000 cycles. A hybrid supercapacitor was fabricated, featuring a cathode composed of a composite electrode consisting of SnO2/CoFe2O4/Fe3O4 and an anode comprising activated carbon (AC). This fabricated SnO2/CoFe2O4/Fe3O4//AC HSC device configuration exhibited impressive performance characteristics, boasting a notable energy density of 38.4 Wh kg−1 at 1468.2 W kg−1. These findings underscore the significant impact of SnO2 on the physio/electrochemical properties of the CoFe2O4/Fe3O4 composite. The outstanding electrochemical performance of this electrode underscores its potential for application in next-generation hybrid supercapacitors.