"Anions-in-Colloid" Hydrated Deep Eutectic Electrolyte for High Reversible Zinc Metal Anodes

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Zinc metal anodes in aqueous batteries face challenges like dendrite formation, side reactions, and limited electrochemical stability.
• Existing electrolytes struggle to provide the necessary stability for high-performance aqueous zinc batteries.

Purpose of the Study:

• To design and investigate a novel hydrated deep eutectic electrolyte (ACDE-3) for improved zinc anode stability.
• To explore the unique 'anions-in-colloid' structure and its impact on electrolyte properties and electrochemical performance.

Main Methods:

• Formulation of ACDE-3 using Zn(ClO4)2·6H2O, β-cyclodextrin (β-CD), and H2O.
• Analysis of the electrolyte's hydrogen-bond network, solvation shell, and anion restriction via β-CD micelles.
• Electrochemical testing of Zn//Zn symmetric cells, Zn//Cu half cells, and full batteries with a poly(1,5-NAPD) cathode.

Main Results:

• ACDE-3 exhibits an 'anions-in-colloid' structure that restricts anion movement, leading to a high Zn2+ transference number (0.84).
• The electrolyte effectively suppresses zinc dendrites, anion-related side reactions, and hydrogen evolution reaction (HER), widening the electrochemical stable window (ESW) to 2.32 V.
• Zn//Zn symmetric cells achieved 900 hours of stability, Zn//Cu half cells showed 97.9% average Coulombic efficiency, and full batteries cycled stably for 200 cycles.

Conclusions:

• The 'anions-in-colloid' hydrated deep eutectic electrolyte (ACDE-3) offers a promising solution for stabilizing zinc anodes in aqueous batteries.
• ACDE-3 demonstrates excellent performance across a wide temperature range (-40°C to 40°C), enhancing battery safety and applicability.
• This electrolyte design opens new avenues for developing high-performance and durable aqueous zinc batteries.