To create the images, two batteries were heated to 250 degrees Celsius (around 482 degrees Fahrenheit) and observed what happened using a thermal camera and a powerful synchrotron X-ray. The object was to trace how faults arise and spread. The researchers acknowledged that the conditions to which the batteries were subjected to were “extreme”; nonetheless they were keen to see where the fault lines are. The long-term aim is to create improved, more robust batteries.
The researchers were mindful that more people are walking about with more lithium-ion batteries plugged into more technological devices than ever before. Given the pace of technological development batteries are required to do more and more. There is a risk, albeit small, that batteries under extreme strain could explode. With the type of batteries studied, lithium ions move from the negative electrode to the positive electrode during discharge and back when charging.
For the study, BBC Science reports, standard batteries, found in household appliances, were taken to the European Synchrotron Research Facility in Grenoble, France. Using a massive particle accelerator, which produces strong X-rays, the scientists were able to look inside the batteries as the batteries were subject to conditions that exceeded the manufacturer’s safety instructions. This was achieved by applying an intense heat gun to the batteries. What happened next is shown in the video below:
The effect observed was called a “thermal runaway” where pockets of gas appear. Here, so much heat was produced to the extent that it caused an escalating chain reaction. It took 161 seconds to reach this point inside one battery, and 217 seconds in the other battery. The second battery actually blew its top off.
The research has been published in the journal Nature Communications. The paper, where the full range of images can be viewed for free, is titled “In-operando high-speed tomography of lithium-ion batteries during thermal runaway.”
In related news, scientists have created tiny “sandwiches” made of nanosheets. These are the basis of a new generation of long-lasting rechargeable batteries.
