University of Tokyo researchers, who explore the physical and chemical properties of electrical energy storage, have found a new way to improve lithium-ion batteries. They successfully increased not only the voltage delivery of a lithium-ion battery but also its ability to suppress dangerous conditions that affect the current range of batteries. This improved lithium-ion battery could make longer journeys in electric vehicles possible and lead to the creation of a new generation of home energy storage, both with improved fire safety.

Different parts of the TFEP molecule account for different improvements. Image Credit: © 2020 Yamada et al. Click image for the largest view.

The research paper describing the new chemistry has been published in Nature Energy.

Batteries power pretty much every device that isn’t plugged into the wall, maybe even your car. However, despite their usefulness, most people only pay attention to them when they run out of power. But there are safety issues with current lithium-ion batteries that can damage equipment and have been known to start fires. Researchers at the Graduate School of Engineering and Graduate School of Science at the University of Tokyo came up with a way to improve safety and provide more charge.

Professor Atsuo Yamada explained, “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 commercialized 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 volts; TFEP, on the other hand, is nonflammable and can tolerate greater voltages of up to 4.9 volts. This extra voltage in an otherwise identically sized package can mean the batteries can last longer before they need another charge. As lithium ion-powered electric vehicles proliferate, this extra range and safety would no doubt prove extremely useful.

Yamada said, “We’re proud of this development and its effectiveness came as a bit of a surprise. 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.”

This development may have large effects on lithium ion batteries and the performance consumers might expect. Now mass produced lithium ion batteries deliver about 3.5 volts so bumping voltage to 4.9 would increase the watts available by 40%, which would be quite an accomplishment. If cycle life, weight, volume, and costs are comparable or better, the lithium ion segment of the battery market is in for a major improvement.


3 Comments so far

  1. Roseland67 on April 15, 2020 9:43 AM

    Are they sure that charging won’t be needed as often?
    As I understand the article, the voltage is increased,
    not the current carrying capacity or storage?

    If only voltage increases, power output will increase linearly,
    indicating you can go quicker, but not longer?
    But how do they know Energy density increases,
    unless it’s just not in the article.

  2. Sia on April 24, 2020 1:45 AM

    If I would receive $1 per article I read on the advancement of li-ion technology, I would be a millionaire!

    Fact is that there has been almost no improvement in commercially available li-ion cells for the past 5 years (some say 10 years). We are stuck at 250 Wh/kg for the best (and most expensive) cells available. There is a lot of talk (solid state li-ion, lithium-sulfur, etc.) but nobody is delivering. It has become rather tedious to follow this field anymore.

    The next breakthrough should have happened by now. But it is not happening. Maybe in another 5 to 10 years it will happen?

  3. Brian Westenhaus on April 24, 2020 9:10 AM

    Agreed. Industry is complacent unless it saves money. The major disruption hasn’t appeared.

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