In-situ growth of Ni-Co LDH/ZnCu₂O₄ nanostructure arrays on Ni foam as electrode material for high areal-capacitance supercapacitor

In this work, a nanoarray electrode consisting of ZnCu2O4 nanoparticles (ZnCu2O4 NPs) and Ni-Co layered double hydroxide (Ni-Co LDH) nanoparticles supported on Ni foam (NF) is successfully achieved by an in situ growth route. The pre-formed ZnCu2O4 nanoparticles on Ni foam operate as a substrate and then guide the Ni-Co LDH nanoparticles on their surface by facile hydrothermal method. Electrochemical performances of the Ni-Co LDH/ZnCu2O4 nanoparticles are evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge techniques (GCD), electrochemical impedance spectroscopy (EIS), and cycle life measurements in 2 mol L-1 KOH electrolyte. The Ni-Co LDH/ZnCu2O4 electrode achieves a maximum capacity of 3511.77 F g(-1) at 1 A g(-1) with raising cycling stability of 99.84% capacitance retention after 5000 cycles at 8 A g(-1), together with similar to 100% Coulombic efficiency. In addition, an asymmetric supercapacitor is fabricated using Ni-Co LDH/ZnCu2O4 NPs on Ni foam (Ni-Co LDH/ZnCu2O4 NPs/NF) as the positive electrode, and activated carbon on Ni foam (AC/NF) as the negative electrode, which shows an operation voltage of 1.15 V, and high specific energy of 103.16 Wh kg(-1) at a specific power of 824.97 W kg(-1) with good cycling stability of 97.88% capacitance retention after 5000 cycles at 2 A g(-1). Moreover, the asymmetric device displays improved low self-discharge behavior by charging it at an optimal current density and time, and the self-discharge is severely suppressed due to the presence of a 3D network of Ni-Co LDH/ZnCu2O4 NPs grown on nickel foam. The unique core-shell configuration of Ni-Co LDH/ZnCu2O4 can make full use of the synergistic effects of two components, provide sufficient electroactive sites, as well as facilitate the charge transport process because of their considerable electrochemical properties, making it a potential choice for electrochemical energy storage.