Liquified Gas Electrolytes Lessen the Risk of Fire for Lithium Metal Batteries

Our society relies on smart devices to get us through the day. While those technologies continue to evolve, the Lithium-ion batteries we use to power them have remained largely stagnant. To meet those demands, Lithium-ion technology will require dramatic improvements in energy density, safety, temperature resilience, and environmental sustainability to handle the type of green future society envisions. Researchers from the University of Chicago have brought us one step closer to that future by developing liquified gas electrolytes that provide a pathway to lessen fire risks, increase energy density, provide a wide voltage range and can be recycled.

"In 2017, a team of UC San Diego nanoengineers discovered hydrofluorocarbon molecules that are gasses at room temperature and will liquefy under a certain pressure," explains Ph.D. student Yijie Yin. "They then invented a new type of electrolyte, which is called 'Liquefied Gas Electrolyte' (LGE)."

That liquified gas broadens the choice of electrolyte molecules for sustainable, rechargeable batteries. The screened fluoromethane and difluoromethane molecules provide a low melting point, fast kinetics, and wide voltage range. This combination of co-solvents offers characteristics that make these liquefied gas electrolytes exhibit superior low-temperature performance (< -60°C), Li metal Coulombic efficiency (>99.8%), and high performance of high-voltage cathodes.

Of course, the LGE electrolyte isn't a perfect solution, as the saturated vapor pressure of those molecules is high, meaning it's still flammable. That said, other fluorinated molecules with longer carbon chains, such as tetrafluoroethane and pentafluoroethane, maintain the inherent advantages of liquefied gasses, including a low melting point, low viscosity, and maintain a particular polarity. Moreover, the same molecules are used in fire extinguishers, meaning the gases can provide fire extinguishing properties.