Engineering coordination interactions and conversion layers for enhanced performance of aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) show promise for future energy storage due to affordability and safety. However, industrial application is hindered by parasitic reactions and zinc dendrites. We address this by adding 1-ethyl-3-methylimidazolium dicyandiamide ([Emim][DCA], or ED) to the electrolyte, suppressing water reduction and Zn dendrite growth. The strong coordination between zinc and nitrogen-containing ligands leads to DCA − anion adsorption on the zinc anode, forming a dense Zn(DCA) 2 layer. This layer aids zinc ion desolvation and isolates water molecules, enabling water-free deposition and facilitating reversible plating/stripping. Additionally, in the water-poor double electric layer, zinc cations introduce triflate anions to the zinc electrode surface, forming an in-situ fluorine-based SEI layer. This layer separates zinc electrodes from water, inhibiting corrosion, and hydrogen evolution. With ED additives, Zn||Zn symmetric cells maintain a cycle life of over 2500 h at 0.5 mA cm −2 and 0.5 mAh cm −2 . Zn||Ti asymmetric cells achieve 99.4 % Coulombic efficiency. The Zn||PANI full cell lasts for 1000 cycles at 4 A g −1 without a significant decrease in specific capacity.