Synthesis of homogeneous porous CuO nanowire@nickel cobalt sulfide core-shell structured nanoarrays on copper foam as high-performance electrode materials for supercapacitors

Abstract

In recent years, due to serious environmental pollution, energy shortages, and growing awareness of environmental protection, the demand for long cycle life, high power density, good rate capability, environmental friendliness, and short charge and discharge time of energy storage devices is increasing. Thus, fuel cells, batteries and supercapacitors (SCs) have gradually become the focus of attention. SCs compared with conventional capacitors and secondary rechargeable batteries have greater specific capacity, higher energy density, higher power density and longer cycle life. 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, and the material and structure of the electrode are key factors. 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 report, we have successfully synthesized a three-dimensional (3D) homogeneous porous CuO nanowires@nickel cobalt sulfide core-shell structured nanosheet arrays (CuO NWAs@Ni-Co-S) on copper foam (CF) as high-performance electrode for supercapacitors (SCs). A potentiostatic deposition technique was used in this preparation process. The unique hierarchical porous three-dimensional (3D) nanostructure was rationally synthesized through a facile two-step procedure. On the CuO nanowire backbones, the CuO NWAs core was completely wrapped by vertically grown nickel cobalt sulfide (Ni-Co-S) nanosheets. The open space between neighboring Ni-Co-S nanoflakes and neighboring CuO NWAs@Ni-Co-S core-shell nanostructures not only achieved a high specific surface area but also increased the electroactive sites of the electrode, which promoted the transmission of ions and faradic reactions during the energy conversion process. When the electric current density was 2 A·g-1, the specific capacitance (Cs) of the CuO NWAs@Ni-Co-S reached 4332 F·g-1. And the CuO NWAs@Ni-Co-S revealed a very high rate capability of 70.5%. Moreover, the CuO NWAs@Ni-Co-S electrode showed excellent cycling stability. After 6000 cycles, the CuO NWAs@Ni-Co-S electrode maintained a very high specific capacitance retention rate of 87% at 50 A·g−1. Choosing an excellent active material and designing a unique nanostructure may be a new strategy for achieving high performance SCs.