Forming an Amorphous ZnO Nanosheet Network by Confined Parasitic Reaction for Stabilizing Zn Anodes and Reducing Water Activity

Rechargeable aqueous zinc-ion batteries (ZIBs) hold great promise for future applications in large-scale energy storage systems. However, the rampant dendrite growth and undesired hydrogen gas evolution over the Zn anode are key issues that make the current ZIB technology immature. Herein, we demonstrate the use of a zeolitic imidazolate framework (ZIF)-derived composite coating on Zn foil for simultaneously suppressing the dendrite growth and H₂ evolution when operated in ZnSO₄ electrolytes. The polyhedral ZIF-8 granules are converted into mesoporous N-doped carbon (NC) decorated with ZnS nanoparticles, and this ZnS/NC composite is coated onto Zn foil. For comparison, bare Zn anodes and Zn foils coated with other ZIF-derived materials including ZnS nanocrystals and NC frameworks are also used to make half or full cells. The Zn@ZnS/NC anode shows the best performance in terms of superb cycling stability, suppressed dendrite growth, and reduced H₂ evolution. At the interface between ZnS/NC coating and Zn foil, confined parasitic reactions result in a layer of an amorphous ZnO nanosheet network, which has a positive effect on reducing water activity. The role of this amorphous ZnO byproduct in reducing H₂ evolution is discussed in detail. This work sheds light on a strategy for making practical ZIBs.