The research tracks in real-time how internal structural damage to batteries evolves and can spread to neighbouring batteries.
The results have been released in the same week that international air-safety experts are meeting in Montreal, Canada, under the auspices of the United Nations, to consider proposals to restrict lithium batteries carried as cargo by commercial jets.
Lithium batteries, packed tightly together, can overheat or catch fire if they are damaged or experience short circuits and have been implicated in fires that have brought down two cargo jets in the past decade. Although battery failure is rare, three airlines have already declared plans to no longer carry bulk shipments of lithium-ion batteries in their cargo planes following US Federal Aviation Administration tests found overheating batteries could cause major fires.
The research results have been published in Nature Communications and the first author of the study, UCL PhD student Donal Finegan (UCL Chemical Engineering), said: “We combined high energy synchrotron X-rays and thermal imaging to map changes to the internal structure and external temperature of two types of Li-ion batteries as we exposed them to extreme levels of heat. We needed exceptionally high speed imaging to capture 'thermal runaway' – where the battery overheats and can ignite. This was achieved at the ESRF beamline ID15A where 3D images can be captured in fractions of a second thanks to the very high photon flux and high speed imaging detector.”