A Zinc Solvation-Tailored Deep Eutectic Electrolyte for High-Performance Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) are gaining attention as safe and cost-effective alternatives to lithium-ion batteries; however, their performance is fundamentally limited by parasitic reactions such as hydrogen evolution (HER), dendrite growth, and surface passivation, which result from the high reactivity of water. In this study, we report a novel nonhydrated deep eutectic electrolyte (DES), termed OUD-122, formulated from Zn(OTf)₂, urea, and dimethyl sulfoxide (DMSO) in a 1:2:2 molar ratio. In this ternary system, DMSO acts as a coordinating ligand to Zn²⁺, resulting in a well-defined solvation structure and an extended hydrogen-bond network among Zn(OTf)₂, urea, and DMSO. This coordination environment effectively suppresses parasitic reactions, prevents byproduct accumulation and electrode corrosion, and significantly expands the electrochemical stability window. As a result, Zn||Zn symmetric cell exhibits exceptional lifespan exceeding 3000 h without short-circuiting, while Zn||Cu asymmetric cells maintain an average Coulombic efficiency of 98.4% over 400 cycles. Furthermore, Zn||Prussian Blue full cells deliver a discharge capacity of 82.5 mAh g^-1 over 5000 cycles at room temperature and maintain 89.6 mAh g^-1 after 800 cycles at 50 °C, demonstrating robust electrochemical performance and thermal resilience.