A Stable Aqueous Zinc‐Thiocyanogen Battery at −30 °C

Aqueous zinc‐ion batteries have attracted wide attention in energy storage due to their inherent high safety and environmental friendliness. However, they normally operate at room temperature and show unsatisfactory performance under low temperatures. As aqueous electrolytes tend to solidify below the ice point, this leads to rapid capacity degradation in low‐temperature environments. Herein, a Zn‐(SCN)2 battery with a water‐in‐salt electrolyte of low freezing point (−89 °C) is reported, where both Li+ and Zn2+ ions coordinate with water molecules to retard the freezing of water and thus improve the low‐temperature performance of the battery. As a result, the Zn‐(SCN)2 battery can be stably cycled for 2300 times at −30 °C with a capacity retention rate of 99.7%. Moreover, the battery also exhibits a high areal specific capacity (984.2 μAh cm−2) and energy density (1.18 mWh cm−2) at 0 °C, shedding new light on the development of stable aqueous zinc‐ion batteries for low‐temperature applications.