Inhibition of side reactions and dendrite growth using a low-cost and non-flammable eutectic electrolyte for high-voltage and super-stable zinc hybrid batteries

Electrolytes are important for long-life high-voltage aqueous zinc ion batteries (ZIBs) and dendrite-free Zn anodes. Here, we report a low-cost eutectic electrolyte composed of acetate and urea that expands the electrochemical stability window to >3.5 V with extremely low water contents and intrinsic non-flammability. Benefiting from the water-starved solvation structure, the Zn anode was protected from dendrite growth through the 3D diffusion of zinc ions and reduced parasitic side reactions. Besides, a wide electrochemical window enables zinc-based batteries with high operating voltage. Therefore, the assembled Zn//LiMn2O4 battery achieved a high discharge plateau (similar to 1.9 V) and excellent capacity retention upon cycling. The optimized eutectogel perfectly inherits the advantages of liquid eutectic electrolytes while obtaining excellent mechanical properties, additionally fulfilling the application of quasi-solid-state flexible batteries under deformation conditions. The eutectic electrolyte has potential applications in high-voltage aqueous ZIBs which integrate performance, low cost, safety, and sustainability.