Simple Preparation of Porous FeCo2O4 Microspheres and Nanosheets for Advanced Asymmetric Supercapacitors

Transition metal oxides (TMOs) can serve as advanced electrode materials and have attracted extensive attention in the past decade. Herein, porous FeCo2O4 microspheres (FeCo2O4 MSs) and FeCo2O4 nanosheets (FeCo2O4 NSs) have been successfully synthesized in different solvent systems, accompanied by a corresponding annealing treatment of precursors. The FeCo2O4 MSs and NSs possessed a mesoporous structure, and the BET surface areas reached 40.9 and 38.5 m2 g–1, respectively. The electrochemical studies were performed in a KOH aqueous electrolyte, and such FeCo2O4 MSs delivered 231.5 C g–1 at 1 A g–1 and exhibited a good long-term cycling performance during 5000 cycles with 71.3% capacity retention. In contrast, the FeCo2O4 NSs delivered a higher capacity of 339.0 C g–1 at 1 A g–1 and exhibited a better rate capability with 73% capacity retention at 13 A g–1. Furthermore, the assembled FeCo2O4 NSs//AC ASC could preserve 100.5% specific capacity after 5000 cycles and exhibited a high energy density of 37.1 W h kg–1 at 928.0 W kg–1, while the FeCo2O4 MSs//AC ASC possessed a relatively low energy density with 26.2 W h kg–1 at 965.5 W kg–1. The outstanding electrochemical behavior of FeCo2O4 NSs and MSs makes them promising electrode materials in electrochemical storage devices. Additionally, this current synthetic strategy possesses some advantages such as simple handling, low maintenance cost, and environmental friendliness; thus, it can be employed for synthesizing other TMOs with superior electrochemical properties.