Alkaline Earth Bismuth Fluorides as Fluoride-Ion Battery Electrolytes

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• Fluoride-ion batteries offer potential advantages over lithium-ion batteries.
• Development of suitable electrolytes with high anion conductivity and material compatibility is crucial for fluoride-ion battery advancement.
• Synthesizing single-crystal fluoride compounds can be challenging, often requiring indirect methods like topotactic chemistry from oxide precursors.

Purpose of the Study:

• To synthesize crystalline alkaline earth bismuth fluoride films.
• To characterize the ionic conductivity of these novel fluoride materials.
• To demonstrate their potential as electrolytes for fluoride-ion battery applications.

Main Methods:

• Oxide molecular beam epitaxy was used to create thin films of BaBiF5 and SrBiF5.
• Topotactic fluorination techniques were employed to convert oxide precursors into crystalline fluoride films.
• Ionic conductivity measurements were performed to evaluate electrolyte performance.
• Epitaxial synthesis of BaBiF5 on BaF2 substrates was achieved.

Main Results:

• Crystalline BaBiF5 and SrBiF5 films were successfully synthesized using molecular beam epitaxy and topotactic fluorination.
• The synthesized fluoride films exhibited measurable ionic conductivities, indicating their potential as battery electrolytes.
• Epitaxial growth of BaBiF5 on BaF2 substrates was demonstrated, paving the way for thin-film device fabrication.

Conclusions:

• The study successfully created novel crystalline alkaline earth bismuth fluoride films.
• These materials demonstrate promising ionic conductivity for potential use as electrolytes in fluoride-ion batteries.
• The demonstrated epitaxial synthesis provides a viable route for developing thin-film fluoride-ion battery devices.