Non-Newtonian fluids could lead the way to fire-proof batteries
Scientists have come up with a way to stop damaged lithium-ion batteries catching fire. The batteries effectively harden on impact, preventing the electrodes making contact and starting a fire.
Lithium-ion batteries now dominate consumer electronics thanks to their superior performance compared to other batteries. They're the most popular choice for portable devices including phones and laptops, and gaining ground in more heavy-duty applications like electric vehicles.
However, damaged lithium-ion batteries are at risk of catching fire, and it's this risk the research seeks to address. As well as causing personal injury, lithium-ion fires are known to have caused house fires and even an airplane crash – that of a UPS Boeing 747 in 2010.
"In a lithium-ion battery, a thin piece of plastic separates the two electrodes," lead researcher Gabriel Veith says in a press release. "If the battery is damaged and the plastic layer fails, the electrodes can come into contact and cause the battery's liquid electrolyte to catch fire."
By using an additive with a conventional electrolyte, the research team at Oak Ridge National Laboratory has effectively come up with an impact-resistant electrolyte. Upon impact, this modified electrolyte solidifies preventing the electrodes from touching. When used in a battery, the chances of a fire resulting from damage are much reduced.
Remarkably, Veith hit upon the idea when playing with his children. They were playing with Oobleck, the non-Newtonian mixture of cornstarch and water which behaves like a liquid until it's struck, when it will adopt the properties of a solid. (Things get even weirder if you put some on a speaker cone). Oobleck is named for the fictional green matter in Dr. Seuss' 1949 book, Bartholomew and the Oobleck.
Previous approaches have been expensive due to the work required to redesign the current battery production process. But Veith's method neatly avoids this by simply injecting the additive to the battery before the electrolyte is added and the battery sealed – an approach for which the team is seeking a patent.
The additive used here is perfectly spherical, 200-nanometer-wide particles of silica suspended in common liquid electrolytes forming a colloid – the battery's very own Oobleck.
The team is initially targeting the drone market where the risk of significant battery damage in the event of a crash (or your drone being shot down) is more severe. But the researchers would like to expand to the automotive and military markets in the future. Remarkably, they think the battery technology could double as body armor for soldiers in the field.
"The battery would function as their armor, and that would lighten the average soldier by about 20 pounds (9 kg)," explains Veith. Currently a soldier may have to carry 20 pounds of batteries on top of their 20 pounds of body armor.
The team hopes to build on the work so that the hardening affects only the damaged area so the rest of the battery, and the gear it's powering, can work as normal.
The research is backed by the US Department of Energy's Advanced Research Projects Agency-Energy and Oak Ridge National Laboratory. It's being presented this week at the 256th National Meeting & Exposition of the American Chemical Society in Boston, Massachusetts.
Source: American Chemical Society
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