Tuning the Electrode–Electrolyte Interface via Hydrogen Bond Donor Structure in Deep Eutectic Solvents for Long-Life Zinc Batteries

To address the issues of poor interfacial compatibility, severe corrosion, and dendrite growth that hinder the further application of aqueous zinc-ion batteries (AZIBs), three amide-based deep eutectic solvents (DESs) were designed and synthesized using formamide, acetamide, and propionamide as hydrogen bond donors (HBDs), and caprolactam (CPL) as the hydrogen bond acceptor (HBA). These DESs were blended with zinc trifluoromethanesulfonate (ZFT) baseline electrolyte to prepare modified electrolytes, aiming to investigate the differences in interfacial adsorption layer formation when amide-based DESs with various hydrogen bond donor structures were applied in electrolytes. XPS results revealed that the propionamide-based modified electrolyte (PDES-1) forms a denser interfacial adsorption layer, which not only improves interfacial wettability and suppresses interfacial corrosion but also guides the uniform deposition of Zn along the (002) plane. Benefiting from such excellent interfacial stability, the PDES-1 electrolyte enables an ultralong cycle life of over 4000 h in Zn//Zn symmetric cells and nearly 300 h under extreme testing conditions. In Zn//V2O5 full cells, it exhibits a capacity retention of 92% after 1200 cycles at 1 A·g–1. This study enhances interfacial stability at the molecular level, providing a new strategy for achieving long-cycling performance in AZIBs.