A Water-Repellent Ionic Liquid/MOF Protective Layer for Stable Zinc Anodes

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous zinc-ion batteries (AZIBs) are promising for grid-scale energy storage.
• Limited cycle stability of AZIBs is primarily due to zinc anode issues like dendrite formation and parasitic reactions.
• Developing stable zinc anodes is critical for advancing AZIB technology.

Purpose of the Study:

• To enhance the cycle stability of zinc anodes in AZIBs.
• To mitigate dendrite growth and suppress side reactions at the zinc anode.
• To improve the overall performance and longevity of AZIBs.

Main Methods:

• Fabrication of a composite protective layer on zinc anodes.
• The protective layer comprises a zinc metal-organic framework (MOF) infiltrated with a hydrophobic ionic liquid (1-ethyl-3-methylimidazoline bis(trifluoromethyl sulfonyl) imide).
• Electrochemical testing of symmetric cells with the modified anodes.

Main Results:

• The MOF's porous structure promoted uniform zinc plating/stripping by distributing the electric field.
• The ionic liquid effectively shielded the zinc anode from the aqueous electrolyte, inhibiting hydrogen evolution and other side reactions.
• The composite layer suppressed the tip effect, leading to significantly improved anode stability.
• Symmetric cells demonstrated stable cycling for over 2600 hours (0.2 mA cm⁻²/0.2 mAh cm⁻²) and 800 hours (1 mA cm⁻²/1 mAh cm⁻²).
• Lower and more stable overpotentials were observed.

Conclusions:

• The artificial composite protective layer effectively enhances zinc anode stability in aqueous electrolytes.
• This strategy addresses key limitations in AZIBs, paving the way for their practical application.
• The developed protective layer offers a viable solution for durable and high-performance aqueous zinc-ion batteries.