Solid-to-Solid Zn Anode and Interhalogen Iodine Cathodes for High-Voltage Fluoride-Ion Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Room-temperature fluoride ion batteries (FIBs) typically exhibit low output voltages (< 0.5 V).
• This limitation stems from the scarcity of reversible electrode materials compatible with liquid electrolytes.
• Developing high-voltage, stable FIBs is crucial for next-generation energy storage.

Purpose of the Study:

• To report a novel high-voltage aqueous fluoride ion battery system.
• To overcome the low voltage limitations of conventional FIBs.
• To demonstrate a stable and long-lasting FIB using new electrode and electrolyte strategies.

Main Methods:

• Coupled a zinc/zinc hydroxyfluoride (Zn↔ZnOHF) anode with an iodine cathode.
• Utilized a reversible I⁻↔I₂F⁻ interhalogen conversion at the cathode.
• Employed an NH₄F-based methanol/water hybrid electrolyte to enhance kinetics and suppress side reactions.

Main Results:

• Achieved a high output voltage of approximately 1.3 V.
• The ZnOHF/Zn anode demonstrated exceptional durability (> 1100 h at 1 mA cm⁻²).
• The Zn/I₂ cells delivered a specific capacity of 168 mAh g⁻¹ at 2 A g⁻¹, retaining 81% capacity after 2500 cycles.

Conclusions:

• Interhalogen chemistry and electrolyte-regulated solid-state fluorination are effective strategies for high-voltage FIBs.
• The developed system offers a promising pathway towards high-voltage, long-life fluoride ion batteries.
• This work significantly advances the potential of fluoride ion battery technology for practical applications.