Synthesis of hierarchical porous CuO Nanowire@NiCo-layered double hydroxide core-shell structured nanoarrays on copper foam for high-performance supercapacotor

Abstract

Supercapacitors (SCs) are a new type of energy storage device that have performance that falls between those of an electrolytic capacitor and a battery. Compared to conventional capacitors, SCs have greater specific capacity and higher energy density. Compared to secondary rechargeable batteries, SCs have higher power density and longer cycle life. SCs have attracted much attention in recent decades due to their fast-dynamic response, high power density, long cycle life, high reliability, and environmentally friendly nature. Thus, SCs have become promising energy storage devices for a wide range of applications, including portable/flexible electronics, large industrial equipment, hybrid electric vehicles, space vehicles, and military devices. The electrode is a very important for SCs, where the material and structure of the electrode is a key factor. Therefore, the research and development of electrode materials with good electrochemical performance and excellent nanostructure plays a crucial role in the development of SCs. In this work, a facile potentiostatic deposition technique was used to fabricate a three-dimensional (3D) core-shell structured nanoarray composed of hierarchical porous CuO nanowires@NiCo layered double hydroxide nanosheets (CuO NWAs@NiCo-LDH) on copper foam (CF). The hierarchical NiCO-LDH nanosheets were grafted vertically along the CuO nanowire backbones. The synthesized material was used as a binder-free electrode material for high-performance supercapacitors. This unique microstructure provided ultrafast electrolyte transport and electron transfer. Groups of holes and splits present in the CuO NWAs@NiCo-LDH arrays served as ion-reservoirs (i.e., they hosted electrolyte ions). This well-designed 3D core−shell structure provided both efficient contact between electrolyte and active materials and facilitated electron and ion transportation. High specific capacitance, excellent cycling stability, and fast redox reactions were observed due to the unique core–shell structure of the material. The CuO NWAs@NiCo-LDH electrode showed a great specific capacitance of 2453F∙g-1 at 2A∙g-1. Rate retention values as high as 80.5% were observed, and 95.8% of the capacitance was retained after 10,000 cycles at 50A∙g-1 in a 6 M KOH aqueous solution. The rational design of 3D core-shell nanostructure might provide new strategies for fabricating promising electrode materials for supercapacitors.