Bio-inspired Hydrated Deep Eutectic Electrolyte Enables Long-lifespan Zinc Anode Across a Broad Temperature Range

Abstract

Aqueous zinc-ion batteries (AZIBs) often suffered from parasitic side reactions associated with the active water and dendrite growth. Herein, motivated by the exceptional hydrophilic properties and the ability to act as a protective barrier for cells of ectoin (ET), a new-type hydrated eutectic electrolyte consisting of Zn(ClO₄)₂·6H₂O, ET, and H₂O in a molar ratio of 1:1:6 (ET-6) was developed for the dendrite-free zinc anodes. The H₂O activity in the electrolyte was reduced by the ET-involved Zn²⁺ solvation structure and the strong hydrogen bond between ET and H₂O, thus inhibiting hydrogen evolution reaction (HER) and corrosion on the zinc anode. The regulated hydrogen bond network enables the electrolyte with an ultralow freezing point of −104.8°C. Moreover, the ET in ET-6 forms a biologically inspired interface protective layer on the surface of the zinc anode. The adsorbed ET molecules effectively capture free H₂O molecules near the zinc surface and promotes the (002)-exposed stripping/plating, thereby enabling the eutectic-based electrolyte, which is plagued by dendrite problems, to achieve a dendrite-free zinc anode. Consequently, this electrolyte enables the zinc anode with long lifespan within a broad temperature range from −40°C to 50°C.