Amorphous nanostructured FeOOH and Co-Ni double hydroxides for high-performance aqueous asymmetric supercapacitors

Amorphous fish-scale-like FeOOH and flower-like Co-Ni double hydroxides (Co-Ni-DH) have been synthesized through one-step electrodeposition. The unique nanostructures of the hydroxides provide a large number of surface active sites, while the amorphous nature of the material systems facilitates the diffusion and reaction of electrolyte ions and enables an isotropic charging/discharging process. Because of these advantages, the FeOOH and Co-Ni-DH electrodes exhibit high pseudocapacitances of 1.11 F cm(-2)/867 F g(-1) and 1.48 F cm(-2)/1201 F g(-1), respectively. In addition, high rate capabilities and superior cyclabilities are achieved. By using the FeOOH and Co-Ni-DH as the anode and cathode, respectively, we have assembled an aqueous asymmetric supercapacitor that delivers a high energy density of 86.4 W h kg(-1)/0.723 mW h cm(-3) and a high power density of 11.6 kW kg(-1)/0.973 mW cm(-3). Moreover, the fabrication process presented in this work is facile, scalable, cost-effective, and environmentally benign, offering a feasible solution for manufacturing next-generation high-performance energy storage devices. (C) 2016 Elsevier Ltd. All rights reserved.