Batteries research aims to design safety tests for lithium-ion batteries

We use lithium-ion batteries in a variety of electronic devices on a daily basis. Increasingly, we demand more batteries that charge more quickly, and store more energy. This makes it extremely important to understand what can happen in the worst-case scenario when a cell fails; although these occurrences are rare, there have been high profile cases of battery malfunction, resulting in fire.

A team of researchers from University College London, together with NASA, have been exploring this question for a while. They have used the ESRF’s beamlines for the last 5 years to find out how batteries degrade and fail, under a broad range of ‘accelerated stress tests’. “We started off using ID15 but then moved onto ID19 to use its super fast X-ray imaging capabilities”, explains Paul Shearing, Professor of Chemical Engineering at UCL. On the beamline they combined X-rays with the information provided by a calorimeter, a tool that measures in detail the temperature profiles of a cell. “By combining the data of the beamline with the information from the calorimeter we get a unique insight into how failure starts and can spread from one battery to another”, he adds.

New safety tests

Historically safety tests for battery qualification have included the nail penetration test, where a hydraulically-driven nail pierces the battery and creates a short circuit. “We have realised that those tests are not as reliable as previously thought”, says Shearing. NASA have developed a device that short circuits the battery in a more controlled way: the so-called ‘internal short circuiting’ device, combined with the high speed X-ray imaging at ESRF, is providing a new gold-standard for battery safety testing.

Text and video by Montserrat Capellas Espuny

Reference:

Finegan, D. P, et al, Journal of Power Sources Volume 417, 31 March 2019, Pages 29-41.​ https://doi.org/10.1016/j.jpowsour.2019.01.077

Top image: A battery charging in a mobile phone.