Scalable Production of the Cobaltous Hydroxide Nanosheet Electrode for Ultrahigh-Energy and Stable Aqueous Cobalt–Zinc Batteries

The relatively low energy density and poor cycling durability of aqueous rechargeable Co–Zn batteries are two main bottlenecks impeding their application in next-generation energy storage devices. A traditional solution for this issue is preparing complicated three-dimensional (3D) electrodes on conductive substrates by epitaxial growth, whose active material easily falls off. Herein, an aqueous rechargeable Co–Zn battery with ultrahigh energy density and excellent electrochemical reversibility is constructed by employing an ultrasonic-assisted growth of a Co(OH)2 nanosheet on Co foam (denoted as COHF) as the cathode. Taking advantage of in-situ formed electrochemically active Co(OH)2 and a porous 3D conductive framework, the COHF electrode presents an ultrahigh capacity of 0.265 mA h cm–2, 24-fold higher than that of pristine Co foam. Impressively, a remarkable energy density of 6.09 mW h cm–3 and a peak power density of 1.75 W cm–3 are achieved by the as-fabricated COHF//Zn battery. Moreover, this COHF//Zn battery exhibits an admirable cyclic durability with 83.3% capacity retention after 10 000 cycles.