Assembly of high-performance hybrid supercapacitors using FeCo2O4 microflowers as battery-type cathode materials

In this work, FeCo2O4 microflowers (MFs) and microparticles (MPs) were respectively prepared at different temperatures via a wet chemical method, along with a post annealing treatment in air. These MFs and MPs exhibited huge specific surface area and a large number of mesopores. Several electrochemical tests were conducted in a three-electrode configuration. The FeCo2O4 MFs delivered a specific capacity of 301.3C g−1, higher than 253.9C g−1 for FeCo2O4 MPs. A hybrid supercapacitor (HSC) device was assembled with FeCo2O4 as cathode and activated carbon (AC) as anode to investigate the practical applications in electrochemical energy storage. The FeCo2O4 MFs//AC HSC delivered a capacity of 107.2C g−1 at 1 A g−1 and an energy density (Ed) of 25.7 W h kg−1 at 862.6 W kg−1, respectively, while the FeCo2O4 MPs//AC HSC showed an Ed of 23.8 W h kg−1 at the power density (Pd) of 878.9 W kg−1. The two HSCs showed little capacity decay after 3000 cycles at 6 A g−1. The capacity of FeCo2O4 MFs and the obtained Ed of HSC were in a high status among those of transition metal oxides (TMOs)-based electrodes reported earlier. The current synthetic strategy can be used as a reference to the synthesis of other similar electrochemical materials for HSC electrodes.