Hydrated Eutectic Electrolyte Induced Bilayer Interphase for High-Performance Aqueous Zn-Ion Batteries with 100 °C Wide-Temperature Range

The practical implementation of aqueous zinc-ion batteries (AZIBs) encounters challenges such as dendrite growth, parasitic reactions, and severe decay in battery performance under harsh environments. Here, a novel hydrated eutectic electrolyte (HEE) composed of Zn(ClO₄ )₂ ·6H₂ O, ethylene glycol (EG), and InCl₃ solution is introduced to effectively extend the lifespan of AZIBs over a wide temperature range from -50 to 50 °C. Molecular dynamics simulations and spectroscopy analysis demonstrate that the H₂ O molecules are confined within the liquid eutectic network through dual-interaction, involving coordination with Zn²⁺ and hydrogen bonding with EG, thus weakening the activity of free water and extending the electrochemical window. Importantly, cryo-transmission electron microscopy and spectroscopy techniques reveal that HEE in situ forms a zincophobic/zincophilic bilayer interphase by the dissociation-reduction of eutectic molecules. Specifically, the zincophilic interphase reduces the energy barrier for Zn nucleation, promoting uniform Zn deposition, while the zincophobic interphase prevents active water from contacting the Zn surface, thus inhibiting the side reactions. Furthermore, the relationships between the structural evolution of the liquid eutectic network and interfacial chemistry at electrode/electrolyte interphase are further discussed in this work. The scalability of this design strategy can bring benefits to AZIBs operating over a wide temperature range.