Fluoride Ion Battery Technologies and Electrochemical Systems

Fluoride-ion batteries (FIBs) represent a promising alternative to lithium-ion chemistries, leveraging the small ionic radius and high electronegativity of fluoride ions to achieve potentially higher theoretical energy densities. Two primary architectures have emerged: all-solid-state configurations employing ceramic fluoride electrolytes and liquid or hybrid systems that enable room-temperature operation. Key challenges include low fluoride-ion conductivity in solid matrices, electrode reversibility, interfacial stability and suppression of parasitic reactions. Research efforts have centred on designing Ruddlesden–Popper and tysonite-type cathode frameworks for reversible fluorination/de-fluorination, engineering composite electrodes to improve contact and ionic pathways, and developing novel solvents or solvent-in-salt formulations to extend electrochemical stability windows above 3 V. The intrinsic absence of dendritic growth and reliance on earth-abundant elements such as magnesium, bismuth and cerium underscore the safety and sustainability advantages. Integrated approaches to electrolyte chemistry, electrode architecture and interface engineering are now essential to translate laboratory prototypes into scalable energy storage solutions for grid stabilisation and electrified transport.

Research from Nature Portfolio

Recent studies have demonstrated an all-solid-state FIB using a Ruddlesden–Popper-type La₂NiO₄+d cathode. Optimising charging conditions preserved cell conductivity, yielding over 220 cycles with coulombic efficiencies between 95 % and 99 %. Fluorination and de-fluorination occur via a multivalent intercalation mechanism in the La₂NiO₄+d lattice, improving cycle life and highlighting intercalation-based high-voltage cathodes as a pathway towards practical solid-state FIBs.

Fluoride Ion Battery Technologies and Electrochemical Systems publication trend

The graph below shows the total number of articles in fluoride ion battery technologies and electrochemical systems across all publications each year (not limited to Nature Index journals).

Technical terms

Fluoride-ion battery (FIB): A rechargeable system in which fluoride ions serve as the mobile charge carriers between electrodes during cycling.

Solid electrolyte: A non-liquid ionic conductor that separates electrodes and facilitates ion transport in solid-state battery architectures.

Solvent-in-salt electrolyte: A highly concentrated solution where the salt functions both as solute and as the primary ion-conducting medium.

Intercalation: The reversible insertion of ions into the layered structure of an electrode material without significant structural collapse.

Coulombic efficiency: The ratio of charge extracted to charge inserted during a cycle, indicating the degree of reversible electrochemistry.

References

1. Recent progress, challenges and prospects of electrolytes for fluoride-ion batteries. Energy Reviews (2024).
2. Solvent-in-Salt Electrolytes for Fluoride Ion Batteries. ACS Energy Letters (2023).
3. High cycle life all-solid-state fluoride ion battery with La2NiO4+d high voltage cathode. Communications Materials (2020).
4. Advancing Fluoride-Ion Batteries with a Pb-PbF2 Counter Electrode and a Diluted Liquid Electrolyte. ACS Energy Letters (2023).