High-performance supercapacitors based on flower-like FexCo3-xO4 electrodes

Through hydrothermal method and thermal treatment, the spinel FexCo3-xO4 (CoFe2O4 and FeCo2O4) has been synthesized successfully as supercapacitors. The morphology of CoFe2O4 is uniform flower-like (400-500 nm) consisted of multi-sheets (thickness, 10-20 nm); while the FeCo2O4 s is irregular cluster-like (250-400 nm) assembled by porous lamellar nanoparticles. Both CoFe2O4 and FeCo2O4 show high discharge specific capacitances (>900 F g(-1)) at the low current density (12 A g(-1)). However, after comparison, the CoFe2O4 specific capacitance decreases slower than FeCo2O4's with the current density increasing; and the long-term stability of CoFe2O4 is also better than FeCo2O4's. Remarkably, the discharge specific capacitance of CoFe2O4 can retain at 82.6% after 6000 cycles. Through further evaluating CoFe2O4 and FeCo2O4 after a long-cycling test via XRD and XPS, it is shown that the electrochemical reversibility and phase stability of CoFe2O4 may be much superior to FeCo2O4's, which matches well with CoFe2O4's excellent cycling performance and enhanced rate capability. (C) 2017 Elsevier B.V. All rights reserved.