Aqueous alkaline–acid hybrid electrolyte for zinc-bromine battery with 3V voltage window

Considerable efforts have been devoted to the development of zinc (Zn) batteries with new battery chemistries (eg. Zn-ion battery, Zn-halogen battery, Zn-alkaline battery, Zn-air battery) that are alternatives to Li-ion technology. Unfortunately, the progress of Zn batteries is hindered by their limited operating voltages (<1.8 V). To enhance the operating voltage, in this study, a new aqueous zinc-bromine (Zn-Br2) battery is demonstrated using alkaline–acid hybrid electrolytes. The alkaline–acid hybrid electrolytes provide a wide potential window from −1.6 to 1.4 V vs. saturated calomel electrode (SCE). The fabricated Zn-Br2 battery delivers an average operating voltage of 2.1 V, which is the highest reported value among all Zn batteries, including Zn-ion battery, Zn-halogen battery, Zn-alkaline battery and, Zn-air battery etc. Significantly, the as-developed aqueous Zn–Br2 battery also exhibited a long-term lifespan (2000 cycles) and ultrahigh specific capacity by combining battery-like and capacitive charge storage. This demonstration of a high-voltage aqueous Zn-Br2 battery configuration represents a significant new development of this class of aqueous electrochemical energy storage device.