In today’s modern world, batteries power almost everything that can’t be plugged in. We can’t live without batteries, but we don’t often think about what happens to them when they run out of juice. The popular lithium-ion batteries have safety issues, with devices sometimes catching fire. Now researchers at the Graduate School of Engineering and Graduate School of Science at the University of Tokyo how found a way to improve the safety and longevity of these batteries. Their research is presented in Nature Energy.
The researchers were able to increase the voltage delivery while reducing some of the dangerous conditions that make lithium-ion batteries catch fire. According to 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 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 known to be flammable and is highly unstable over 4.3 volts. TFEP, however, is not flammable and can remain stable up to 4.9 volts. The researchers managed to fit this extra voltage into the same size battery, meaning that it can last longer between charges. This could have applications in lithium-ion powered cars, meaning that people could drive further between charges and do it more safely.
"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”, continued Yamada. "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."