Bidentate Coordination Structure Facilitates High-Voltage and High-Utilization Aqueous Zn-I₂ Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous zinc-iodine batteries offer promise for energy storage but face limitations in cathode reaction potential and energy density.
• Activating high-valence iodine cathode reactions is crucial for developing high-voltage zinc-iodine batteries.

Purpose of the Study:

• To design a multifunctional electrolyte additive to stabilize high-valence iodine cathode reactions.
• To enhance the energy density and cycling stability of aqueous zinc-iodine batteries.

Main Methods:

• Design and synthesis of trimethylamine hydrochloride (TAH) as an electrolyte additive.
• Utilizing advanced characterization techniques including synchrotron radiation and in situ Raman spectroscopy.
• Employing Density Functional Theory (DFT) calculations to elucidate reaction mechanisms.

Main Results:

• Achieved a stable high-valence iodine cathode through a unique (TA)ICl bidentate coordination structure, enabling four-electron transfer.
• Demonstrated enhanced zinc anode stability with a maximum areal capacity of 57 mAh cm⁻² and 97% zinc utilization.
• Developed an aqueous Zn-I₂ full cell with 5000 stable cycles at a 2.5 N/P ratio.

Conclusions:

• The multifunctional electrolyte additive TAH successfully stabilizes high-valence iodine cathode reactions.
• The unique bidentate coordination structure is key to achieving high capacity and stable cycling in aqueous zinc-iodine batteries.
• This work paves the way for advanced high-voltage and high-capacity aqueous zinc-iodine energy storage systems.