Insights into the design of zincophilic artificial protective layers enabling uniform nucleation and deposition for stable dendrite-free Zn anodes

Abstract

Aqueous zinc-ion batteries (AZIBs) are highly attractive as energy-storage systems owing to their inherent safety, low cost, and simple assembly processes. However, the growth of Zn dendrites and side reactions at the Zn metal anode significantly degrade their electrochemical performance. To address these challenges, this study introduces a surface modification that increases the lifespan and cycling stability of AZIBs by constructing an artificial zinc sulfide (ZnS) protective layer on the Zn anode. For the first time, the fundamental mechanism of uniform Zn plating underneath the ZnS protective layer is demonstrated through experiments and density functional theory simulations. In addition, the artificial ZnS protective layer of optimized thickness is formed using a simple, thickness-controllable coating method. Notably, the ZnS protective layer favors Zn atom adsorption while suppressing clustering, enabling uniform Zn deposition. In addition, defects within the thin ZnS coating modulate Zn2+ adsorption and diffusion, which facilitates Zn plating underneath the protective layer. This mechanism promotes uniform Zn nucleation and enhances the kinetics of Zn2+, preventing dendrite formation and side reactions and thereby improving the stability and electrochemical performance of the battery. The resulting Zn@ZnS||Zn@ZnS symmetric cell exhibits a cycle life of over 1600 h and excellent rate performance. Moreover, it maintains a high coulombic efficiency of 99.5 % and capacity retention of 80.1 % after 1500 cycles at a current density of 0.5 A g(-1), demonstrating exceptional long-term cycling stability. These insights into developing effective artificial protective layers that enable uniform nucleation will promote durable, dendrite-free Zn anodes for advanced AZIBs.