Zwitterionic Bifunctional Layer for Reversible Zn Anode

A Zn metal anode suffers from severe dendrite issues and passive byproducts, which restrict the practical application of Zn-ion batteries. Herein, a bifunctional poly zwitterionic ionic liquid (PZIL) is designed as a new ion-migration layer to suppress Zn dendrites and side reactions. On one hand, the zwitterionic functional groups on the PZIL layer guide the Zn ion distribution to regulate the deposition behavior of Zn. On the other hand, the tight bond between zwitterionic groups and water molecules can build an H2O-poor interface on the surface of the Zn anode to avoid side reactions. Based on the above two functions, a symmetrical cell with the PZIL-layer-modified Zn exhibits a stable plating/stripping performance (2600 h at 1 mA cm–2) with low reversible deposition potential (∼50 mV). The concept of a zwitterionic bifunctional layer will open up a new avenue for reversible anodes for Zn-ion batteries as well as other battery systems.