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Measurement for our planet

As COP26 approaches, discover how NPL plays a key role in enabling climate action through the delivery of accurate, reliable data that supports decision making and enables low carbon innovation.

Case studies

Preventing lithium-ion battery explosions

We worked with UCL to help prevent costly product failure caused by thermal runaway.

The challenge

Lithium-ion (Li-ion) batteries are used in their billions worldwide as a rechargeable power source. They are used everywhere from smart phones and tablets to cars and planes to medical devices. However, rare cases of catastrophic lithium-ion battery failure, leading to fires or explosions. These safety issues have captured headlines and led to costly product recalls.

Often, explosions arise due to the process of “thermal runaway” in which the temperature of the battery rises too quickly for heat to dissipate. There is an urgent need to understand in detail how this failure mechanism occurs and how to prevent it.

The solution

We collaborated with University College London (UCL), the European Synchrotron Radiation Facility, NASA’s Johnson Space Center, the US Department of Energy’s National Renewable Energy Laboratory, the University of Warwick and Diamond Light Source to investigate thermal runaway mechanisms, using high-speed X-ray tomography and radiography in combination with thermal imaging.

By inserting an internal short circuit device inside a custom-built 18650 cylindrical cell, thermal runaway could be triggered at a pre-determined location within the cell, making it possible to position the X-ray beam in exactly the right place to witness the initiation process. This allowed us to assess the damage in real time and see how thermal runaway spread throughout the battery cells. The cells went from being completely intact to being completely destroyed within around one second.

The impact

This work has yielded unprecedented insight into the evolution of the internal structure of the cell in the milliseconds leading up to explosion and has resulted in high impact publications in Nature CommunicationsPhysical Chemistry Chemical PhysicsEnergy & Environmental ScienceThe Journal of the Electrochemical Society and Advanced Science.

The importance of this work has also been recognised through The Engineer’s 2017 Collaborate to Innovate Award in the Safety & Security category.

The findings show the importance of isolating failing cells to prevent dangerous chain reactions of battery failures, and ultimately, the new imaging techniques developed in this work will support improvements in Li-ion battery reliability and safety. This could help avoid disastrous failures such as the now-discontinued Samsung Galaxy Note 7, whose product recall in 2016 is estimated to have cost the business more than $5 billion.

Find out more about NPL's Electrochemistry research

Important pioneering research that has advanced our understanding of lithium battery failure.

The Engineer Collaborate to Innovate Awards - 2017