Stabilized Rechargeable Aqueous Zinc Batteries Using Ethylene Glycol as Water Blocker

Addressing the cost concerns and safety of zinc metal has stimulated research on mild aqueous Zn‐metal batteries. However, their application is limited by dendrite formation and H2 evolution on the Zn anode. Here, ethylene glycol (EG) is proposed as additional water blocker to form localized high‐concentration electrolyte for aqueous Zn batteries. This unique solvation structure inhibits hydrate formation and facilitates close association of Zn2+ and SO42−, which alleviates undesired H2 evolution and enables dendrite‐free Zn plating/stripping. Accordingly, a Zn//PQ‐MCT (phenanthrenequinone macrocyclic trimer) full cell with such electrolyte exhibits a very long cycling life (more than 8000 cycles). Furthermore, this EG‐based aqueous electrolyte is non‐flammable and inexpensive and prevents evaporation of water when open to the atmosphere, endowing aqueous Zn batteries with excellent safety performance and easy operability in practical applications. It′s not watered down: Ethylene glycol (EG) is used as water blocker to form localized high‐concentration aqueous Zn electrolyte, which alleviates the undesired H2 evolution and dendrite formation reaction on a Zn anode. A Zn‐organic cell with such electrolyte exhibits excellent cycling stability. Furthermore, this EG‐based aqueous electrolyte exhibits nonflammability, low cost, and effective water retention in the open atmosphere, endowing aqueous Zn batteries with excellent safety performance and easy operability.