Highly Reversible Aqueous Zinc Batteries enabled by Zincophilic-Zincophobic Interfacial Layers and Interrupted Hydrogen-Bond Electrolytes.
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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 7.6m ZnCl2 aqueous electrolyte with 0.05m SnCl2 additive, which in situ forms a zincophilic/zincophobic Sn/Zn5 (OH)8 Cl2 H2 O bilayer interphase and enables low temperature operation. Zincophilic Sn decreases Zn plating/stripping overpotential and promotes uniform Zn plating, while zincophobic Zn5 (OH)8 Cl2 H2 O top-layer suppresses Zn dendrite growth. The eutectic electrolyte has a high ionic conductivity of 0.8mScm-1 even at -70C due to the distortion of hydrogen bond network by solvated Zn2+ and Cl- . The eutectic electrolyte enables ZnTi half-cell a high Coulombic efficiency (CE) of >99.7% for 200 cycles and ZnZn cell steady charge/discharge for 500h with a low overpotential of 8mV at 3mAcm-2 . Practically, ZnVOPO4 batteries maintain >95% capacity with a CE of >99.9% for 200 cycles at -50C, and retain 30% capacity at -70C of that at 20C.