Phase diagrams guided design of low-temperature aqueous electrolyte for Zn metal batteries

Aqueous Zn batteries are promising for large-scale energy-storage because of low cost and high energy density. It also has inherent advantages under low temperatures and high rate circumstances because of low viscosity and high safety. However, a large number of H-bonds lead to the freezing of aqueous electrolyte below 0 °C, which limits its batteries' performance under extreme environment. Inspired by temperature-component phase diagrams, we rationally design low-temperature aqueous electrolytes by modulating electrolyte structure to break the original H-bond network (LTAE-BH), leading to a low freezing point. This electrolyte renders reversible Zn plating/stripping under an ultra-low temperature −50 °C. Full-cells based on this electrolyte are robust delivering 86 mA h g−1 over 10,000 cycles at −50 °C with 99.92 % Coulombic efficiency (CE). This work provides a simple, green and cheap salts strategy to design high-performance aqueous Zn batteries under low-temperature environment.