Selectively “Size-Excluding” Water Molecules to Enable Highly Reversible Zinc Metal Anode

Abstract

Significant water-related side reactions hinder the development of highly safe, low-cost aqueous zinc metal batteries (AZMBs) for grid-scale energy storage. Herein, by regulating the length of alkyl chains, we successfully adjust the interstitial voids between the polymer chains of metal soap interface between 1.48 Å (size of zinc ion) and 4.0 Å (size of water molecule). Therefore, water molecules are selectively “size-excluded”, while smaller zinc ions are permitted to pass through. Consequently, water-related side reactions (including hydrogen evolution, corrosions) could be effectively inhibited. Furthermore, the abundant zinc ion tunnels accompanied with zincophilic components facilitate the homogenization of Zn2+ flux thus preventing dendrite growth. Therefore, the Zn symmetric cell shows a lifespan of approximately 10000 cycles at 20 mA cm-2 and 1 mA h cm-2, and the Zn//Na5V12O32 (NVO) full cell delivers much better cycling stability with much higher capacity retention around 93% after 2000 cycles at 2 A g-1 compared to the counterpart of bare Zn (19%). This work provides valuable insights for the utilization of metal soap interfaces and the regulation for their channel size between perpendicular alkyl chains to realize precise water shielding, not only applicable in ZMBs, but also in other aqueous batteries.