Understanding Stable Zinc Anodes in a Wide Temperature Range: Molecular Simulations Reveal Key Mechanisms

Furthermore, molecular-level simulations were conducted to explore the underlying mechanisms of stable zinc anodes over a broad temperature range, based on the solvent structure. Urea molecules contain two amino (-NH2) groups, which possess strong polarity and exhibit a higher tendency to adsorb onto the surface of the zinc metal electrode in comparison to water molecules (Fig). This leads to the promotion of uniform zinc deposition and the prevention of uneven growth of zinc dendrites.

The diffusion barriers of water molecules in various electrolytes were calculated in the optimized solvent structure obtained from simulations. It can be observed that the initial energy of the solvent structure in DES-3 electrolyte is lower and the diffusion barrier is higher, resulting in the formation of a uniform and dense Zn deposition layer on the anode surface.

In conclusion, Fig 4c and 4d depict the Zn2+ solvation structure and the interface reaction between Zn metal and the electrolyte. Active free water and the surrounding dissolved water of Zn2+ exist in the aqueous solution. As a result, electrochemically driven parasitic reactions, including dendritic growth, passivation formation, hydrogen evolution, and zinc metal corrosion, spontaneously occur. Conversely, in the DES electrolyte, the number of free water molecules is significantly diminished, and the coordination of Urea with Zn2+ reduces the attraction between water and Zn2+. This solvation structure is beneficial for suppressing side reactions and enabling smooth zinc deposition.