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

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.