Phase-Field Simulation of a Dynamic Protective Layer for the Inhibition of Dendrite Growth in Zinc Metal Batteries

Metallic zinc (Zn) has been considered one of the most promising anode materials for next-generation aqueous Zn batteries due to its low redox potential and high storage capacity. However, excessive dendrite formation in Zn metal, corrosion, the evolution of hydrogen gas during the cycling process, and the poor Zn-ion (Zn²⁺) transport from the electrolyte to the electrode limit its practical application. One of the most effective strategies to suppress Zn dendrite growth and promote Zn²⁺ transport is to introduce suitable protective layers between the Zn metal electrode and the electrolyte. Herein, we mathematically simulated the dynamic interactions between the Zn deposition on the anode and the resulting displacement of a protective layer that covers the anode, the latter of which can simultaneously inhibit Zn dendrite growth and enhance the Zn²⁺ transport through the interface between the Zn anode and the protective layer. Our simulation results indicate that a protective layer of high Zn²⁺ diffusivity not only improves the deposition rate of the Zn metal but also prevents dendrite growth by homogenizing the Zn²⁺ concentration at the anode surface. In addition, it is revealed that the anisotropic Zn²⁺ diffusivity in the protective layer influences the 2D diffusion of Zn²⁺. Higher Zn²⁺ diffusivity perpendicular to the Zn metal surface inhibits dendrite growth, while higher diffusivity parallel to the Zn metal surface promotes dendrite growth. Our work thus provides a fundamental understanding and a design principle for controlling anisotropic Zn²⁺ diffusion in the protective layer for better suppression of dendrite growth in Zn metal batteries.