Batteries in e-cars have a critical weak point: cold. Most drivers of Teslas and other electric vehicles have already noticed that the battery drains much faster in winter than in warmer seasons. Of course, this has a negative effect on the range (we reported). Now, a team at the US Department of Energy’s Argonne and Lawrence Berkeley National Laboratories has developed a new chemical solution designed to protect batteries from the cold and allow optimal charging at any time of year, reports Science Daily.
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Electrolyte protects battery from cold
According to the researchers, the main problem with current lithium-ion batteries is the liquid electrolyte. This key component of the battery transfers ions between the two electrodes of the battery. It ensures that the battery is charged and discharged. However, at temperatures below freezing, the liquid begins to freeze. This condition severely limits the effectiveness of charging. The research team has now developed a fluorine-containing electrolyte that is said to work well even at sub-zero temperatures.
“Not only did our team find an antifreeze electrolyte that doesn’t lose its charging capacity at minus four degrees Celsius, but we also found out at the atomic level what makes it so effective,” explains Zhengcheng Zhang, a senior chemist and group leader in the Department of Chemicals Science and Technology of Argonne. This low-temperature electrolyte is promising for batteries in electric vehicles and for energy storage in power grids, smartphones and computers.
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Function analyzed at the atomic level
The team studied several fluorine-containing solvents. They were able to identify the composition that exhibited the lowest energy barrier for the release of lithium ions from the clusters at sub-freezing temperatures. They also determined at the atomic level why this particular composition worked so well. It depended on the position of the fluorine atoms in each solvent molecule and their number.
In laboratory cell tests, the team’s fluorinated electrolyte maintained a stable energy storage capacity for 400 charge/discharge cycles at minus four degrees Celsius. Even at this sub-zero temperature, the capacity was equivalent to that of a cell with a conventional carbonate-based electrolyte at room temperature. “Thus, our research has shown how to tailor the atomic structure of electrolyte solvents to develop new electrolytes for sub-zero temperatures,” says Zhang.
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Team patents solution and is looking for industrial partners
According to the researchers, the antifreeze electrolyte has an additional advantage: it is much safer than the carbonate-based electrolytes currently used because it cannot catch fire. “We are patenting our low-temperature and safety electrolyte and are now looking for an industrial partner to adapt it to one of his lithium-ion battery designs,” Zhang announced.