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article imageFuture batteries could include built-in fire extinguishers

By James Walker     Jan 16, 2017 in Technology
Researchers have developed a lithium-ion battery that includes its own fire extinguisher capable of preventing a device from bursting into flame. It comes in the wake of Samsung's Galaxy Note 7 smartphone disaster, potentially preventing future incidents.
Lithium-ion batteries power most modern mobile devices. Over the past decade, developments in lithium-ion tech have delivered longer-lasting cells that can charge to 80 percent in just half an hour. They are also a recognised fire hazard though, carrying an inherent risk that isn't desirable for consumer technology.
Although it's rare for a properly charged battery to explode, Samsung's Note 7 catastrophe brought the potential dangers of lithium-ion cells into the public eye. A few months later, a team of researchers have designed a new battery that could prevent a similar incident occurring again in the future.
The team from Stanford University placed the flame retardant substance triphenyl phosphate (TPP) inside a shell within the battery electrolyte fluid. When the battery temperature rises above 150C (302F), the protective shell melts and releases the chemical compound. This quenches the flames, preventing the fire from getting established. In tests, the system extinguished fires 0.4 seconds after they began.
TPP has already been investigated as a potential way to stop batteries catching fire. However, previous efforts have dissolved the substance directly into the electrolyte fluid. This reduces the performance of the battery. The key to the team's success was developing the battery shell. This separates the two substances until the battery reaches "thermal runaway," at which point a fire is inevitable unless the temperature is reduced.
"The encapsulation of a flame retardant inside a protective polymer shell has prevented direct dissolution of the retardant agent into the electrolyte, which would otherwise have negative effects on battery performance," the team said. "During thermal runaway of the lithium-ion battery, the protective polymer shell would melt, triggered by the increased temperature, and the flame retardant would be released, thus effectively suppressing the combustion of the highly flammable electrolytes."
With lithium-ion batteries seemingly here to stay, efforts to reduce their susceptibility to bursting into flame could make a significant impact on smartphone safety. There's no word yet on when this technology could be ready for commercial use though.
Issues that need to be resolved include questions around durability. The researchers found TPP began to leak into the electrolyte after just 360 battery charge cycles. Most modern cells survive 1,000 charges before performance is noticeably degraded.
Samsung is now expected to reveal the conclusion of its investigation into the Galaxy Note 7 explosions later this month. The company has already determined defective batteries were at the heart of the problems, according to local media reports that have not been verified. Samsung said it's working "diligently" to provide a comprehensive report into what went wrong.
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