Flower-like ZnCo2O4 microstructures with large specific surface area serve as battery-type cathode for high-performance supercapacitors

Abstract

In this work, flower-like ZnCo2O4 microstructures were synthesized through an initial solvothermal method and combined with an extra calcination treatment. The mixed solvent containing glycerol and isopropyl alcohol in different volume ratio played an important role for the formation of MFs with different size, namely the ZnCo2O4 MFs-20/20 and ZnCo2O4 MFs-5/35. These ZnCo2O4 MFs were assembled by many porous nanosheets with thin thickness and exhibited huge specific surface area. Benefitting from this significant feature, these MFs presented outstanding electrochemical properties. Under the current load of 1 A g−1, the ZnCo2O4 MFs-20/20 delivered a specific capacity of up to 373.2C g−1, which was superior to that (315.6C g−1) of ZnCo2O4 MFs-5/35. At the same time, they also demonstrated a good rate performance with 72.4 % and 76.9 % capacity retention under 10 A g−1, respectively. To evaluate the practical application of these MFs in supercapacitor, a hybrid supercapacitor (HSC) was assembled using such ZnCo2O4 MFs as cathode and activated carbon (AC) as anode. The ZnCo2O4 MFs-20/20//AC HSC delivered a high energy density of up to 44.9 W h kg−1 at 1077.7 W kg−1, and the ZnCo2O4 MFs-5/35//AC HSC exhibited an inferior energy density of 37.2 W h kg−1. Both HSCs presented superior cycling property over 5000 cycles at a high current load of 8 A g−1. These electrochemical results suggest that the ZnCo2O4 MFs in this work can serve as advanced cathode for the assembly of high-performance hybrid supercapacitor, and may have brilliant commercial prospect in the field of electrochemical energy storage.