To what extent do anions affect the electrodeposition of Zn?

Zinc metal, with its high theoretical capacity and low cost, stands out as a promising anode material for affordable high energy-density storage technologies in rechargeable batteries. However, obtaining a high level of reversibility in zinc electrodeposition, which is pivotal for the success of rechargeable zinc-metal-based batteries, remains a significant challenge. A critical factor in this regard is the physicochemical characteristics of the electrolyte solution. Previous studies have indicated that adjusting the electrolyte solutions' composition with additives or co-solvents, along with fine-tuning concentrations and pH levels, can enhance the reversibility and kinetics of Zn deposition/stripping. However, the precise impact of Zn salts counter anions in the electrolyte solutions on these processes is not fully understood yet. Aiming to focus on the key fundamental aspects related to the electrolytes' influences on the Zn electroplating, we delve into the impact of anions on this process. Using advanced in situ and ex situ analytical methods, we reveal the role of the anions in the electrolyte solutions in zinc deposition/dissolution processes. Computational simulations shed light on the electrolytes' solvation structure, establishing a clear relationship between deposition behavior and the molecular variations specific to the different anions. These findings pave the way for new design principles aimed at optimizing the composition of electrolyte solutions for zinc metal batteries, potentially enhancing their performance and efficiency. Achieving reversible zinc deposition/stripping necessitates careful optimization of the electrolyte composition. This study offers detailed insights into the impact of various anionic species (chloride, sulfate, perchlorate) on this process.