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

Abstract

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.

Recent progress and challenges of co‐based compound for aqueous Zn battery

“…It would be attractive if a highly efficient and low cost method is exploited to fabricate a high‐performance Co(OH) 2 cathode material. [ 160 ] To solve this issue, Lu and his coworkers applied a facile ultrasound‐assisted method to synthesize a Co(OH) 2 nanosheet onto a Co foam (CF) (shown in Figure 7A). [ 160 ] The oxidation of CF was initiated by HCl treatment under ultrasound, generating Co 2+ ions on the active layers, which reacted with surface water and air to form Co(OH) 2 .…”

“…[ 160 ] To solve this issue, Lu and his coworkers applied a facile ultrasound‐assisted method to synthesize a Co(OH) 2 nanosheet onto a Co foam (CF) (shown in Figure 7A). [ 160 ] The oxidation of CF was initiated by HCl treatment under ultrasound, generating Co 2+ ions on the active layers, which reacted with surface water and air to form Co(OH) 2 . This synthetic route was simple, scalable and inexpensive, potentially producing 3D electrode materials in large scale.…”

“…C, Areal capacity collected from GCD curves. Reproduced with permission: Copyright 2020, American Chemical Society [ 160 ]…”

Ultrafast Co0.8Al0.2-Layered Double-Hydroxide Nanosheets Cathode for High-Performance Co–Zn Battery

“…Benefiting from the polyvalent states and good electrical conductivity of Co-based compounds (e.g., Co 3 O 4 , NiCo 2 O 4 , Co­(OH) 2 ), − Co–Zn batteries have attracted extensive attention. ,− For instance, a CoSe 2– x //Zn battery based on activating the Co 3+ /Co 4+ redox pair can deliver a high voltage of 1.9 V . A Co 3 O 4 //Zn battery is capable of having a 241 Wh kg –1 energy density with 80% capacity maintained after 2000 cycles .…”

Iron decorated ultrathin cobaltous hydroxide nanoflakes with impressive electrochemical reactivity for aqueous Zn batteries

“…To tackle this issue, a series of cobalt-based compounds, such as cobalt oxides, sulfides and hydroxides have been developed. 6–10 For instance, Zhi et al constructed a Co 3+ rich-Co 3 O 4 cathode via hydrothermal synthesis and calcination, which delivered a capacity of 0.22 mA h cm −2 . 5 Zeng et al introduced surface phosphate-ions and oxygen-vacancies into NiCo 2 O 4 by annealing the pristine NiCo 2 O 4 nanosheets in the presence of sodium dihydrogen phosphate at 300 °C, achieving an areal capacity of about 0.24 mA h cm −2 at 2 mA cm −2 (0.18 mA h cm −2 at 4 mA cm −2 ).…”