Challenges for fluoride superionic conductors: fundamentals, design, and applications.

Area of Science:

• Solid-state ionics
• Materials science
• Electrochemistry

Background:

• Ionics, focusing on ion properties, significantly impacts modern technology, exemplified by lithium-ion batteries (LIBs).
• Ionic conduction in solids involves ion flow driven by electrical or chemical gradients.
• Certain solid ionic materials exhibit higher conductivity than liquids, attracting intensive research.

Purpose of the Study:

• To review fluoride-ion conductors as promising charge carriers for future fluoride-ion batteries (FIBs).
• To explore the potential of fluoride ions as alternatives to lithium ions in next-generation batteries.
• To identify challenges and future research directions for room-temperature solid-state FIBs.

Main Methods:

• Comprehensive literature review of fluoride-ion conductors.
• Classification of materials based on type and form.
• Analysis from experimental and theoretical physics viewpoints.

Main Results:

• Fluoride ions are identified as highly promising charge carriers for post-lithium-ion battery technologies.
• The review categorizes fluoride-ion conductors and discusses their properties.
• Current understanding, challenges, and future prospects are outlined.

Conclusions:

• Advancing fluoride-ion conductivity in solids to superionic levels at room temperature is crucial for practical all-solid-state FIBs.
• Further research integrating experimental and theoretical physics is needed to optimize fluoride-ion conductor materials.
• This work provides a roadmap for developing high-performance solid-state fluoride-ion batteries.