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Electrolyte found for room-temperature fluorine-ion batteries

“Fluoride-based battery electrodes can store more ions per site than typical lithium-ion electrodes, which means that this technology has the capability to be much more energy dense,” said Purdue University chemical engineer Brett Savoie,

The key is a liquid electrolyte that can dissolve and carry fluorine ions – a synthesised molecule dubbed BTFE, discovered by researchers at the Jet Propulsion Laboratory, which Savoie modelled, with similar compounds, in relation to fluoride ions.

BTFE’s molecule has two positively charged regions that strongly interact with fluoride, and simulations revealed how these regions lead BTFE molecules to surround fluoride and dissolve it at room temperature.

Savoie’s simulations also provided a mechanism for testing other solvents on fluoride, according to Purdue, such as ‘glyme’ molecules that expand the voltage and stability window of BTFE – making it less likely that a fluoride-ion battery would fail at higher voltages.

Such a cell is far from reality. The next step for the team is to keep the cathode and anode functioning – so far the copper-based cathode has been stabilised so that it doesn’t dissolve in the electrolyte, said Purdue – it is a copper–lanthanum trifluoride core-shell cathode that exhibits reversible partial fluorination and defluorination.

Members of JPL and Purdue are working with researchers from Caltech, the Honda Research Institute, Lawrence Berkeley National Laboratory, the US National Science Foundation and the US Department of Energy Office of Science.