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

Highlights: • Amorphous nanostructured fishscale-like FeOOH is deposited on the Ni foam. • Amorphous flower-like Co–Ni double hydroxides are grown on the Ni foam. • The fabrication process is facile, scalable, and cost-effective. • The FeOOH and Co–Ni double hydroxides show great pseudocapacitive performances. • The asymmetric supercapacitor delivers high energy and power densities. 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.