Development of Fluoride-Ion Primary Batteries: The Electrochemical Defluorination of CFx

• Published in: Journal of physical chemistry. C 2024-08, Vol.128 (34), p.14195-14205
• Main Authors: Robinson, Loleth E., Wang, Jonah, Asare, Harrison, Andrews, Jessica L., Tripathi, Balram, Katiyar, Ram, Melot, Brent C., Messinger, Robert J., Jones, Simon C., West, William C.
• Format: Article
• Language: English
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.4c03412

The lithium–carbon monofluoride (Li-CF x ) couple has the highest specific energy of any practical battery chemistry. However, the large polarization associated with the CF x electrode (>1.5 V loss) limits it from achieving its full discharge energy, motivating the search for new CF x reaction mechanisms with reduced overpotential. Here, using a liquid fluoride (F)-ion conducting electrolyte at room temperature, we demonstrate for the first time the electrochemical defluorination of CF x cathodes, where metal fluorides form at a metal anode instead of the CF x cathode. F-ion primary cells were developed by pairing CF x cathodes with either lead (Pb) or tin (Sn) metal anodes, which achieved specific capacities of over 700 mAh g –1 and over 400 mAh g –1 , respectively. Solid-state 19 F and 119 Sn{ 19 F} nuclear magnetic resonance (NMR), X-ray diffraction (XRD), Raman, inductively coupled plasma (ICP), and X-ray fluorescence (XRF) measurements establish that upon discharge, the CF x cathode defluorinates while Pb forms PbF 2 and Sn forms both SnF 4 and SnF 2 . Technological development of F-ion metal-CF x cells based on this concept represents a promising avenue for realizing primary batteries with high specific energy.