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Boffins hose down fiery Li-ion batteries with industrial lubricant

Non-flammable electrolyte found hiding in plain sight

Tesla fire

As Boeing and Tesla both know, if you mistreat a lithium-ion battery, it can start a fire – which puts a premium on the search for non-flammable components. Now, US researchers say they've found a candidate electrolyte in an unexpected place.

When they're overcharged or overheated, the electrolyte in lithium-ion batteries can burn. However, it's hard to find a non-flammable electrolyte that doesn't degrade battery performance.

As the University of North Carolina at Chapel Hill explains, the chemical, perfluoropolyether, is already known to the world as a coating to stop marine life sticking to the bottom of ships.

They're proposing using perfluoropolyether (or PFPE) as a replacement electrolyte because it's both non-flammable and has good ion transport properties, the university says.

Also familiar as an industrial lubricant, PFPE came to the attention of a UNC chemist, Joseph DeSimone, who noticed that it has a “chemical structure to a polymeric electrolyte commonly studied for lithium-ion batteries” (from their abstract in PNAS, that electrolyte is alkyl carbonate). When his group also found that lithium salts could be dissolved in PFPE, and it remained non-flammable, “that's when we decided to roll with it”.

The PFPE electrolytes up to 200°C, the researchers say, have good electrolytic properties when coupled with the right electrodes (LBNL's Nitash Balsara worked on electrodes for this paper), and have a good cycling lifetime. ®

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