Ionic Liquid Water Pocket for Stable and Environment-Adaptable Aqueous Zinc Metal Batteries

The strong reactivity of water in aqueous electrolytes toward metallic zinc (Zn), especially at aggressive operating conditions, remains the fundamental obstacle to the commercialization of aqueous zinc metal batteries (AZMBs). Here, a water-immiscible ionic liquid diluent 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide (EmimFSI) is reported that can substantially suppress the water activity of aqueous electrolyte by serving as a water pocket, enveloping the highly active H2O-dominated Zn2+ solvates and protecting them from parasitic reactions. During Zn deposition, the cation Emim(+) and anion FSI- function respectively in mitigating the tip effect and regulating the solid electrolyte interphase (SEI), thereby favoring a smooth Zn deposition layer protected by inorganic species-enriched SEI featuring high uniformity and stability. Combined with the boosted chemical/electrochemical stability endowed by the intrinsic merits of ionic liquid, this ionic liquid-incorporated aqueous electrolyte (IL-AE) enables the stable operation of Zn||Zn0.25V2O5 center dot nH(2)O cells even at a challenging temperature of 60 degrees C (>85% capacity retention over 400 cycles). Finally, as an incidental but practically valuable benefit, the near-zero vapor pressure nature of ionic liquid allows the efficient separation and recovery of high-value components from the spent electrolyte via a mild and green approach, promising the sustainable future of IL-AE in realizing practical AZMBs.

Automated summary

The use of water-immiscible ionic liquid diluent EmimFSI can suppress the reactivity of water in aqueous electrolytes toward metallic zinc and protect the zinc solvates, which is beneficial for the commercialization of aqueous zinc metal batteries. The ionic liquid diluent plays a role in regulating the reaction during zinc deposition, resulting in a highly uniform and stable zinc deposition layer. In addition, the low vapor pressure nature of the ionic liquid allows for efficient separation and recovery of high-value components from the spent electrolyte, promising a sustainable future for aqueous zinc metal batteries.