Smartly tailored Co(OH)2-Ni(OH)2 heterostucture on nickel foam as binder-free electrode for high-energy hybrid capacitors

Abstract

Heterostructured materials composed of nickel and cobalt hydroxides exhibit impressive prospect in aqueous-based supercapacitors owing to their unique layered frameworks. Herein, a series of Co(OH)2-Ni(OH)2 heterostructures are prepared on nickel foam as binder-free electrodes (denoted as NCN-x) via a simple two-step electrodeposition method, where Co(OH)2 serves as the interlayer and Ni(OH)2 serves as the out layer. By tuning the deposition charge quantities of these two kinds of hydroxides, different electrode architectures with various mass ratios of α-Ni(OH)2 to β-Co(OH)2 are obtained. Among these electrodes, the smartly tailored NCN-3 electrode representing 1.0 C and 0.75 C deposition charges separately for Co(OH)2 and Ni(OH)2 exhibits particular core-shell nanosheet-like microstructure, possessing large surface area and short ion/electron transportation pathways. As a result, it delivers good cycling performance of ∼75.8% capacitance retention after 1000 cycles at 5 A g−1. Moreover, the hybrid capacitor consists of NCN-3 cathode and AC anode realizes high energy and power densities (32.6 Wh kg−1 at 465.7 W kg−1 and 25.5 Wh kg−1 at 7061.5 W kg−1). This work can serve as a guide for designing other heterostructured electrodes by electrochemical method.