Lithium Ion-based batteries are among the most efficient and widely used battery technologies. However, electrolyte batteries mainly contain carbonated organic solvents, considered highly flammable by a small temperature window. To ensure that they do not burn out while working at high temperatures, engineers must build safe electrolytes that not only burn but also be able to operate at a wide range of temperatures.
Researchers at the University of California San Diego’s group Shirley Meng and the Army Research Laboratory recently developed new liquid gas electrolytes that can be used to produce lithium-metal batteries that can safely operate from 60 to 55 C. These electrolytes have a unique structure, described in a paper published in Nature Energy, enabling them to extinguish fires.
“Liquefied gas electrolyte (LGE) was first considered by our research team in a paper published in Science in 2017 and developed over five years,” said Yijie Yin, one of the researchers working in the field of Prof. Meng. , told TechXplore. “It contains a variety of fluorocarbon gases, which when put under pressure, liquefies to form a strong chemical environment, a low-freezing point, a low-cost electrolyte.”
Compared with the many state-of-the-art electrolytes introduced in previous papers, YIN-designed LGEs and their counterparts are more compatible with lithium metal batteries. An initial experiment with Li anode found 99.6% performance Coulombic (C.E.) efficiency over 500 cycles and was able to rotate 18650 cells under extreme conditions.
The first team-designed LGEs were based on fluoromethane (F.M.) and difluoromethane (DFM). Despite their advantages, these electrolytes were still burning under moderate operating pressure.
“In order to overcome the safety issues revealed in our previous experiments, we have emphasized the safety features of LGEs by incorporating clean fire extinguishers into their design, power differs from LGE systems only,” Yin explained. “1,1,1,2 tetrafluoroethane (TFE) and pentafluoroethane (PFE) solvents are fire extinguishers, but also maintain a low cooling, low cost of vapor reduction.”
The new LGE introduced in the group’s latest paper has been made chiefly (i.e., more than 80% of its volume) of pure, fire-retardant components TFE and PFE. This dramatically increases their safety, reducing the risk that lithium-metal batteries will catch fire at high temperatures.