Interfacial regulation of zinc plating/stripping via cation engineering in acetate-based ionic liquid electrolyte additives for durable zinc anode.

Irreversible Zn anode behaviour during cycling is a critical challenge in aqueous Zn-based batteries, driven by dendrite formation and hydrogen evolution reactions. By optimizing the local environment such as Zn2+ ions solvation structure and adsorption of different species on the surface, the non-homogeneity at the Zn anode can be controlled. In this work, influence of different cations of acetate based ionic liquids such as 0.1 M 1-ethyl-3-methylimidazolium acetate, 0.1 M tetra methyl ammonium acetate, 0.1 M choline acetate and 0.1 M piperidin-1-ium acetate as an electrolyte additive with 1 M zinc acetate aqueous solution is investigated. Different cations tune the nucleation behaviour of Zn2+ deposition which can help in limiting the dendrite formation and hydrogen evolution reaction. Molecular dynamics simulations further elucidate the role of cations in Zn2+ ion solvation and intermolecular structuring. The Zn2+ ion density and binding free energy (ΔGbind) calculations reveal that electrolyte additive such as 1-ethyl-3-methylimidazolium acetate facilitate enhanced 3D diffusion of Zn2+ ion, leading to homogeneous deposition on the thermodynamically stable crystal plane. As a result, 0.1 M 1-ethyl-3-methylimidazolium acetate deliver a cycle life span surpassing 1000 h in Zn||Zn symmetrical cell under constant circumstances of 1 mA cm-2 and 1 mAh cm-2 and also retain 98% coulombic efficiency in Zn||Cu asymmetrical cell at 0.5 mA cm-2 and 0.5 mAh cm-2 upto more than 600 h. This work facilitates a promising direction towards exploration of ionic liquid electrolyte additives for stable Zn anode.