Highly Reversible Aqueous Zinc Batteries enabled by Zincophilic–Zincophobic Interfacial Layers and Interrupted Hydrogen‐Bond Electrolytes

Aqueous Zn batteries promise high energy density but suffer from Zn dendritic growth and poor low‐temperature performance. Here, we overcome both challenges by using an eutectic 7.6 m ZnCl 2 aqueous electrolyte with 0.05 m SnCl 2 additive, which in situ forms a zincophilic/zincophobic Sn/Zn 5 (OH) 8 Cl 2 ⋅H 2 O bilayer interphase and enables low temperature operation. Zincophilic Sn decreases Zn plating/stripping overpotential and promotes uniform Zn plating, while zincophobic Zn 5 (OH) 8 Cl 2 ⋅H 2 O top‐layer suppresses Zn dendrite growth. The eutectic electrolyte has a high ionic conductivity of ≈0.8 mS cm −1 even at −70 °C due to the distortion of hydrogen bond network by solvated Zn 2+ and Cl − . The eutectic electrolyte enables Zn∥Ti half‐cell a high Coulombic efficiency (CE) of >99.7 % for 200 cycles and Zn∥Zn cell steady charge/discharge for 500 h with a low overpotential of 8 mV at 3 mA cm −2 . Practically, Zn∥VOPO 4 batteries maintain >95 % capacity with a CE of >99.9 % for 200 cycles at −50 °C, and retain ≈30 % capacity at −70 °C of that at 20 °C.