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Scientists stop thermal runaway in 18650 lithium-ion cells

Tue, 04/13/2021 - 09:59 -- paul Crompton

Scientists in the US and Europe and have developed a method to prevent short-circuits in 18650 lithium-ion batteries during nail penetration tests.

The team found a piece of plastic placed between the aluminum or copper positive electrode was sufficient in every instance to prevent thermal runaway.

18650 cells were experimented on due to their use in electric vehicles and aerospace applications.

The findings were published in the journal Cell Reports Physical Science. The paper was titled: “Prevention of lithium-ion battery thermal runaway using polymer-substrate current collectors.” 

The team consisted of the National Renewable Energy Laboratory (NREL)—working with researchers at NASA and scientists from University College London, The Faraday Institution in Oxford, National Physical Laboratory in London, and The European Synchrotron in France.

The polymer current collector (PCC) was manufactured by Soteria Battery Innovation Group, and the custom 18650 batteries made by Coulometrics.

The scientists' experimented using High-speed X-ray imaging at 2,000 frames per second enabled the researchers to capture what happened inside the batteries with great detail during the nail test.

A battery short can trigger a failure in adjacent batteries and spark fires as the temperature inside has been shown to top 800 degrees Celsius (1,472 degrees Fahrenheit).

Repeated experiments found that as the temperature increased in the shorted battery, the PCC shrank to isolate the nail from the negative terminal and thus shut-down the short circuit.

Donal Finegan, a staff scientist at NREL, said: “It is very rare that batteries fail catastrophically, but when that does happen it can be very damaging.

“Not only just for the safety and health of people involved, but economically as well for a company.”

“When a battery does fail, it fails very quickly, so it can go from being completely intact to being engulfed in flames and completely destroyed within a couple of seconds.

“It's very fast and very difficult to understand what happens in that two seconds. But it's also very important to understand exactly what happens because it is the management of those two seconds that is important for improving the safety of batteries.”

The latest research comes on the heels of NREL’s release of the Battery Failure Databank, a compilation of data generated by hundreds of abuse tests conducted on lithium-ion batteries. 

Finegan said: “Small manufacturers don't always have the time and the resources to test batteries in such a rigorous way that we have over the past five to six years.

“They can, for free, come to the NREL website, download all of this data and make their own assessment of how safe the batteries are that they may or may not choose for their application.”

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