Synergistic cathode-anode modulation via a multifunctional ionic liquid additive for high-performance zinc‑iodine...

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous zinc-iodine batteries (ZIBs) offer safe and cost-effective large-scale energy storage.
• Key challenges include zinc anode dendrite growth, hydrogen evolution, and cathode polyiodide shuttle.
• These issues limit the commercial viability and long-term stability of ZIBs.

Purpose of the Study:

• To introduce a multifunctional ionic liquid additive, 1-hydroxyethyl-3-methylimidazolium trifluoromethylsulfonate ([HEMIM][OTf]), for synergistic interfacial stabilization in ZIBs.
• To investigate the additive's impact on both zinc anode and iodine cathode performance.
• To demonstrate enhanced cycling stability and capacity retention in ZIBs.

Main Methods:

• Computational and experimental investigations were combined to analyze the additive's mechanism.
• The study examined the role of the [HEMIM][OTf] cation and anion in modulating electrode interfaces.
• Performance was evaluated using Zn║Zn symmetric cells and Zn║I2 full cells under various conditions.

Main Results:

• The OTf- anion modified the Zn2+ solvation sheath, suppressing side reactions.
• The HEMIM+ cation formed a water-lean layer on the Zn anode, mitigating hydrogen evolution and corrosion.
• In situ formed ZnF2-rich layer inhibited dendrite growth, enabling uniform Zn deposition.
• HEMIM+ anchored I3- at the cathode, reducing polyiodide shuttling and enhancing active material utilization.
• Zn║I2 cells achieved 120.5 mAh g-1 after 4100 cycles at 2.0 A g-1 with 90.5% retention.

Conclusions:

• The [HEMIM][OTf] additive effectively enhances ZIB performance by simultaneously stabilizing both electrodes.
• This ionic liquid additive strategy offers a promising approach for developing high-performance and durable ZIBs.
• The findings provide a new pathway for synergistic interfacial optimization in aqueous metal-ion batteries.