Enabling Solid-Electrolyte Interphase Formation Prior to Water Reduction in Aqueous Zinc Batteries by Mild Protic...

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous zinc batteries (AZBs) face challenges like hydrogen evolution reaction (HER) and zinc anode dendrite formation, hindering practical application.
• These issues stem from the lack of an effective passivating solid-electrolyte interphase (SEI) that can prevent water decomposition.
• In situ SEI construction prior to water reduction is crucial for stable AZB operation.

Purpose of the Study:

• To investigate the potential of protic solid-electrolyte interphase (SEI) chemistry for aqueous zinc batteries.
• To introduce 2-mercapto-1-methylimidazole (MMI) as a precursor for forming a protective SEI on zinc anodes.
• To evaluate the effectiveness of the MMI-derived SEI in suppressing side reactions and improving zinc anode stability.

Main Methods:

• Thermodynamic prediction of reduction potentials for mild protic compounds.
• Electrochemical evaluation of 2-mercapto-1-methylimidazole (MMI) reduction prior to water.
• Analysis of the SEI composition (organic compounds and Zn(OH)2) formed from MMI reduction on zinc anodes.
• Corrosion current measurements to assess the passivating effect of the MMI-derived SEI.

Main Results:

• 2-mercapto-1-methylimidazole (MMI) was found to reduce before water due to its higher proton activity, forming an SEI via a ring cleavage mechanism.
• The MMI-derived SEI significantly reduced the corrosion current of zinc anodes by two orders of magnitude (from 1170 to 13.6 μA cm⁻²).
• The SEI effectively suppressed hydrogen evolution reaction (HER) and ensured dendrite-free zinc deposition.

Conclusions:

• The MMI-derived SEI provides a superior passivating effect, crucial for stable zinc anodes in AZBs.
• This protic SEI strategy effectively suppresses detrimental side reactions like HER and dendrite formation.
• The study demonstrates a promising approach for developing high-performance and reversible zinc anodes for AZBs.