Hierarchical heterostructured ZnCo2O4@CuCo2O4 nanograss composite electrode for advanced asymmetric supercapacitor applications

Abstract

Binder-free hybrid hierarchical nanocomposite electrodes offer an effective strategy to enhance charge storage kinetics and structural stability in advanced supercapacitors. Herein, a heterostructured ZnCo 2 O 4 @CuCo 2 O 4 nanograss electrode was directly fabricated on flexible stainless steel mesh (FSSM) through a two-step hydrothermal synthesis followed by thermal annealing. In this architecture, the allium flower-like CuCo 2 O 4 nanowires grown on the FSSM substrate act as a robust framework for further conformal growth of ZnCo 2 O 4 . This resulted in forming a porous hierarchical architecture with abundant electroactive sites, enhanced electrolyte accessibility, rapid ion transport, and improved structural integrity. Furthermore, taking advantage of synergistic heterostructure and complementary multivalent redox activity, the ZnCo 2 O 4 @CuCo 2 O 4 /FSSM electrode achieved a high specific capacitance (C sp ) of 2031.1 F g −1 at 2 mA cm −2 and maintained 96.8 % of its initial capacitance after 6000 GCD cycles at 35 mA cm −2 . An asymmetric solid–state supercapacitor (ZnCo 2 O 4 @ CuCo 2 O 4 /FSSM//AC/FSSM) using a PVA–KOH gel electrolyte exhibited a C sp of 226.1 F g −1 at 3 mA cm −2 , a maximum energy density of 80.4 Wh kg −1 at 359.4 W kg −1 , 100 % coulombic efficiency, and 95.5 % capacitance retention after 5000 cycles. These findings highlight the strong promise of the ZnCo 2 O 4 @CuCo 2 O 4 /FSSM nanograss electrode for high-performance energy storage applications.