An aqueous zinc‐ion battery working at −50°C enabled by low‐concentration perchlorate‐based chaotropic salt electrolyte

Abstract Rechargeable aqueous zinc‐ion batteries (ZIBs) have been considered as a promising candidate for the large‐scale energy storage device owing to their low cost and high safety. However, the practical application of aqueous ZIBs at low temperature environment is hindered by the freezing aqueous electrolytes, which leads to a sharp drop in ionic conductivity, and thereby a rapid deterioration of battery performance. Herein, a chaotropic salt electrolyte based on low concentration aqueous Zn(ClO4)2 with superior ionic conductivity under low temperature (4.23 mS/cm at −50°C) is reported. The anti‐freezing methodology introduced here is completely different from conventional freeze‐resistant design of using “water‐in‐salt” electrolyte, cosolvents, or anti‐freezing agent additives strategy. Experimental analysis and molecular dynamics simulations reveal that the as‐prepared Zn(ClO4)2 electrolyte possesses faster ionic migration compared with other commonly used Zn‐based salts (i.e., Zn(CF3SO3)2 and ZnSO4) electrolyte. It is found that Zn(ClO4)2 electrolyte can suppress the ice crystal construction by forming more hydrogen bonds between solute ClO4− and solvent H2O molecules, thus leading to a superior anti‐freezing property. The fabricated ZIBs using this aqueous electrolyte exhibits a dramatically enhanced specific capacity, remarkable rate capability, and great cycling stability over a wide temperature range, from −50 to 25°C. The aqueous ZIBs also exhibit an outstanding energy density of 238.4 Wh/kg without compromising the power density (7.9 kW/kg) under −20°C. Moreover, the assembled aqueous ZIBs can also cycle stably over 1000 cycles at an ultra‐low −50°C. The high‐safety and cost‐effective chaotropic salt electrolyte presented here is a promising strategy for low temperature energy storage application.