Understanding the hydrogen and halogen bonds of ionic liquids in regulating ion solvation and dynamic behaviors of aqueous zinc electrolytes

Despite their low cost and intrinsic safety, aqueous rechargeable zinc-ion batteries suffer from rapid performance deterioration originating from parasitic reactions and inhomogeneous deposition on the Zn anode. Halogen bonds share similarities with hydrogen bonds, yet their unique directionality, strength tunability, and hydrophobicity provide a promising approach for enhancing the reversibility of Zn anodes. Herein, a systematic comparison of ionic liquids with different anions, acetate (Ac⁻) and chloride (Cl⁻), is performed to explore the non-covalent interactions in regulating ion solvation and dynamic behaviors of electrolytes. Different from the Ac⁻ possessing a strong capacity to form hydrogen bonds with water, the Cl⁻-water halogen bonds not only enable the structural diffusion of Zn²⁺ with better diffusion efficiency but also reduce the Zn²⁺ de-solvation energy barrier to promote uniform Zn nucleation. Consequently, the accelerated ions diffusion and homogeneous Zn deposition work in synergy to ensure high reversibility of Zn anode. These fundamental insights highlight the importance of hydrogen and halogen bonds in determining the dynamics and electrochemical behavior of electrolytes, providing theoretical guidance for the rational design of high-performance electrolytes.