Rationally designed CuCo2O4@Ni(OH)2 with 3D hierarchical core-shell structure for flexible energy storage.

ABSTRACT

Composite electrodes that possess both rational structures and appropriate integration are needed to deliver high electrochemical performance in energy storage devices. In this paper, a flexible and binder-free electrode material based on a heterogeneous core-shell structure of CuCo2O4@Ni(OH)2 nanosheets grown on carbon cloth was fabricated by a simple method. The unique three-dimensional hierarchical structure gives the electrode a large specific surface area, which enables rapid response and increases of specific capacitance. The CuCo2O4@Ni(OH)2/carbon fiber cloth (CFC) composite electrode exhibited a specific capacitance of 2160 F g-1 at 1 A g-1 and a good rate capability energy of 82.7% at 20 A g-1. A flexible all-solid-state asymmetric supercapacitor (FAASC) was assembled with the CuCo2O4@Ni(OH)2/CFC electrode as the positive electrode, and activated carbon (AC)/CFC as the negative electrode. This device showed both a high energy density and power density (58.9 W h kg-1 at a power density of 400 W kg-1), and good long-term cycling stability. Furthermore, the assembled CuCo2O4@Ni(OH)2/CFC//AC/CFC devices were capable of driving a blue light-emitting diode after a short charge. The remarkable performance of this CuCo2O4@Ni(OH)2/CFC electrode indicates that this heterogeneous structure has great potential for applications in flexible high-performance energy storage devices.