Researchers have discovered what they claim is a potential solution to stop lithium-ion device batteries, such as those found in smartphones, from combusting.
A number of devices, including laptop computers and smartphones have undergone product recalls as a result of dangerous batteries - most notably Samsung's Galaxy Note 7, which had to be recalled and scrapped due to a battery fault that caused a number of devices to either explode or go up in flames.
However, after studying practical and inexpensive ways to help prevent device battery fires, scientists from the Oak Ridge National Laboratory and the University of Rochester claim to have devised a solution.
Instead of using a non-flammable, solid electrolyte to make lithium-ion batteries safer, as some researchers have tried to do, the researchers mixed an additive into the conventional electrolyte to create an impact-resistant electrolyte.
"In a lithium-ion battery, a thin piece of plastic separates the two electrodes," said lead researcher of the study, Gabriel Veith.
"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."
According to Veith, this solidifies on impact and prevents the electrodes from touching if the battery is damaged during a fall or crash. Put simply, if the electrodes don't touch each other, the battery shouldn't catch fire.
"Even better, incorporating the additive would require only minor adjustments to the conventional battery manufacturing process," he added.
This idea came to Veith when he and his children were playing with a mix of corn starch and water known as 'oobleck'.
"If you put the mixture on a cookie tray, it flows like a liquid until you start poking it, and then it becomes a solid," Veith explained. "After the pressure is removed, the substance liquefies again."
Veith then realised that it might be possible to exploit this reversible 'shear thickening' behaviour to make batteries safer. To do this, he and his colleagues used silica suspended in common liquid electrolytes for lithium-ion batteries.
On impact, the silica particles clumped together and blocked the flow of fluids and ions.
For this experiment, the researchers used perfectly spherical, 200-nanometer-diameter particles of silica, which basically looked like superfine sand.
"If you have that very uniform particle size, the particles disperse homogeneously in the electrolyte, and it works wonderfully," Veith added.
He continued: "If they're not [the same size], then the liquid becomes less viscous on impact, and that's bad."
In future, the researchers plan to enhance the battery prototype so the part of the battery that's damaged in a crash would remain solid, while the rest of the battery would go on working.
The team is now looking for applications, such as drone batteries, but are also looking at the automotive market where crashes of electric vehicles have frequently led to fires.
They also plan to make a bigger version of the battery, which would be capable of stopping a bullet, they said.
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