A "Zn2+ in Salt" Interphase Enabling High-Performance Zn Metal Anodes.

ABSTRACT

Zinc metal is a promising anode candidate for aqueous zinc ion batteries due to its high theoretical capacity, low cost, and high safety. However, its application is currently restricted by hydrogen evolution reactions (HER), by-product formation, and Zn dendrite growth. Herein, a "Zn2+ in salt" (ZIS) interphase is in situ constructed on the surface of the anode (ZIS@Zn). Unlike the conventional "Zn2+ in water" working environment of Zn anodes, the intrinsic hydrophobicity of the ZIS interphase isolates the anode from direct contact with the aqueous electrolyte, thereby protecting it from HER, and the accompanying side reactions. More importantly, it works as an ordered water-free ion-conducting medium, which guides uniform Zn deposition and facilitates rapid Zn2+ migration at the interface. As a result, the symmetric cells assembled with ZIS@Zn exhibit dendrite-free plating/striping at 4500 h and a high critical current of 14 mA cm-2. When matched with a vanadium-based (NVO) cathode, the full battery exhibits excellent long-term cycling stability, with 88% capacity retention after 1600 cycles. This work provides an effective strategy to promote the stability and reversibility of Zn anodes in aqueous electrolytes.