Developing improved electrolytes for aqueous zinc-ion batteries to achieve excellent cyclability and antifreezing ability.

Due to their low cost, high safety, environmental friendliness, and impressive electrochemical performances, aqueous zinc-ion batteries are considered promising alternative technologies to lithium-ion batteries for use in large-scale applications. However, existing aqueous zinc-ion batteries usually suffer from poor cyclability and cannot operate at subzero temperatures. Herein, to solve these problems, the electrolyte in aqueous zinc-ion batterie is optimized by adding the appropriate amounts of diethyl ether and ethylene glycol. Results show that the addition of 1% diethyl ether contributes to the best cyclability at 25 °C. Furthermore, the addition of 30% ethylene glycol results in the best electrochemical performances at 0 and - 10 °C. This significant performance improvement at low temperatures is ascribed to the high ionic conductivity of the modified electrolyte and the low charge transfer impedance of the battery with the modified electrolyte at 0 and -10 °C. It is also shown that the modified electrolyte can decrease the nucleation overpotential of zinc plating, enhance the interfacial stability between the zinc metal and electrolyte, suppress the zinc dendritic growth and side reactions, and decrease the self-corrosion rate of the zinc anode. This work offers a facile strategy to realize aqueous zinc-ion batteries with excellent cyclability and antifreezing ability and may inspire research on other aqueous energy storage systems.