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.