Room-temperature cycling of metal fluoride electrodes: Liquid electrolytes for high-energy fluoride ion cells

Room-temperature cycling of metal fluoride electrodes: Liquid electrolytes for high-energy fluoride ion cells

Victoria K. Davis Christopher M. Bates Kaoru Omichi Brett M. Savoie Nebojša Momčilović Qingmin Xu William J. Wolf Michael A. Webb Keith J. Billings Nam Hawn Chou Selim Alayoglu Ryan K. McKenney Isabelle M. Darolles Nanditha G. Nair Adrian Hightower Daniel Rosenberg Musahid Ahmed Christopher J. Brooks Thomas F. Miller III Robert H. Grubbs Simon C. Jones

Science 2018

Fluoride ion batteries are potential “next-generation” electrochemical storage devices that offer high energy density. At present, such batteries are limited to operation at high temperatures because suitable fluoride ion–conducting electrolytes are known only in the solid state. We report a liquid fluoride ion–conducting electrolyte with high ionic conductivity, wide operating voltage, and robust chemical stability based on dry tetraalkylammonium fluoride salts in ether solvents. Pairing this liquid electrolyte with a copper–lanthanum trifluoride (Cu@LaF3) core-shell cathode, we demonstrate reversible fluorination and defluorination reactions in a fluoride ion electrochemical cell cycled at room temperature. Fluoride ion–mediated electrochemistry offers a pathway toward developing capacities beyond that of lithium-ion technology.

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