Water Catchers within Sub‐Nano Channels Promote Step‐by‐Step Zinc‐Ion Dehydration Enable Highly Efficient Aqueous Zinc‐Metal Batteries

Abstract Zinc metal suffers from violent and long‐lasting water‐induced side reactions and uncontrollable dendritic Zn growth, which seriously reduce the coulombic efficiency (CE) and lifespan of aqueous zinc‐metal batteries (AZMBs). To suppress the corresponding harmful effects of the highly active water, a stable zirconium‐based metal‐organic framework with water catchers decorated inside its sub‐nano channels is used to protect Zn‐metal. Water catchers within narrow channels can constantly trap water molecules from the solvated Zn‐ions and facilitate step‐by‐step desolvation/dehydration, thereby promoting the formation of an aggregative electrolyte configuration, which consequently eliminates water‐induced corrosion and side reactions. More importantly, the functionalized sub‐nano channels also act as ion rectifiers and promote fast but even Zn‐ions transport, thereby leading to a dendrite‐free Zn metal. As a result, the protected Zn metal demonstrates an unprecedented cycling stability of more than 10 000 h and an ultra‐high average CE of 99.92% during 4000 cycles. More inspiringly, a practical NH 4 V 4 O 10 //Zn pouch‐cell is fabricated and delivers a capacity of 98 mAh (under high cathode mass loading of 25.7 mg cm −2 ) and preserves 86.2% capacity retention after 150 cycles. This new strategy in promoting highly reversible Zn metal anodes would spur the practical utilization of AZMBs.