Higher voltage and safer operation for Li-ion batteries

Researchers from The University of Tokyo have found a way to improve the performance and safety of lithium-ion batteries, increasing not only the battery’s voltage delivery but also its ability to suppress dangerous conditions. Their findings, published in the journal Nature Energy, could lead to longer journeys in electric vehicles and to the creation of a new generation of home energy storage, both with improved fire safety.

As explained by Professor Atsuo Yamada, “A battery’s voltage is limited by its electrolyte material. The electrolyte solvent in lithium-ion batteries is the same now as it was when the batteries were commercialised in the early 1990s.

“We thought there was room for improvement, and we found it. Our new fluorinated cyclic phosphate solvent (TFEP) electrolyte greatly improves upon existing ethylene carbonate (EC), which is widely used in batteries today.”

EC is notoriously flammable and is unstable above 4.3 V. TFEP, on the other hand, is nonflammable and can tolerate voltages of up to 4.9 V. This extra voltage capacity means the batteries can last longer before they need another charge. As lithium-ion-powered electric vehicles proliferate, this extra range and safety would prove extremely useful.

“We’re proud of this development and its effectiveness came as a bit of a surprise,” Prof Yamada said. “This is because the way we came up with TFEP was novel in itself, thanks in part to our collaboration with organic chemist Professor Eiichi Nakamura.

“Most research on electrolytes is a bit trial and error, with slight alterations to the basic chemistry rarely offering any advantage. Our approach came from a theoretical understanding of the underlying molecular structures. We predicted the safe, high-voltage properties before we experimentally verified them. So it was a very pleasant surprise indeed.”

Image caption: Different parts of the TFEP molecule account for different improvements. Image© 2020 Yamada et al.

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Originally published here.