An Adaptive Hydrophobic Interphase for Sustainable Aqueous Zinc Metal Batteries.

Abstract

Aqueous Zn metal batteries (AZMBs) are promising for large-scale energy storage, but their practical deployment is plagued by the issues of Zn anode involving non-uniform plating/stripping, H₂ evolution, and low Zn utilization rate (ZUR). Herein, we report an adaptive hydrophobic interphase enabled by the adsorption/desorption of organic imidazolium cations that circumvent these challenges. Mechanistic studies reveal that typical monovalent inorganic cations (i.e., Na⁺, NH₄ ⁺) with higher hydration energy show considerably weaker electrostatic adsorption at the Zn interface than the selected organic cations, attributed to the charge-screening effect of solvating-water. Among the selected organic cations, imidazolium species outperform quaternary ammonium cations in the interface adsorption, with longer alkyl chains further enhancing this effect. The exemplified 1-propyl-3-methylimidazolium (Pmim⁺) cation creates a water-depleted electric double layer that suppresses interfacial side reactions and homogenizes Zn²⁺ plating. Moreover, Pmim⁺ undergoes electric-field-induced desorption that allows the involvement of H₂O during Zn²⁺ stripping. The resultant dynamic hydrophobic interphase sustains compact Zn deposition and uniform stripping even at 25 mAh cm^-2 (85.9% ZUR). Consequently, the formulated Pmim⁺-containing electrolyte enables the Zn electrode with a prolonged cycling life of 6000 h at 1 mA cm^-2 and robust deep-cycling performance, and supports stable operation of full AZMBs under harsh conditions.