In a study published today in Nature Communications, a group of European researchers pushed two different lithium ion batteries to the breaking point so they could observe what happens when they fatally overheat. Why? For science, of course!
As it turns out, battery overheating is actually a pretty big problem. Lithium ion batteries can be found in everything from cellphones to electric vehicles, and on rare occasions they can fail due to “thermal runaway,” a process in which increased temperatures kick off a chain reaction that makes the battery get hotter and hotter — sometimes indeed causing it to explode. This type of failure is thought to have contributed to a fire that led to a fatal plane crash back in 2010 — and it’s out of concern for this risk that some airlines will soon cease bulk shipments of lithium ion batteries.
Not much is known about the mechanisms that lead to thermal runaway, so to gain some insight on the process, the researchers did what any reasonable scientist would do — they blew up some batteries. To trigger the failure, they aimed a concentrated heat gun at over 200 degrees Celsius (392 Fahrenheit) on a pair of rotating batteries, and used “high-speed synchrotron X-ray computed tomography and radiography, in conjunction with thermal imaging, to track the evolution of internal structural damage and thermal behavior” during the experiment.
In other words, they blasted two different batteries with a ray gun until they died, and filmed the whole thing with a CT scanner and an infrared camera. The results were pretty revealing: In the first battery, which had built-in internal support, the material inside the cell got so hot that it eventually sprayed molten liquid and superheated gas out of its top. In the second battery (which didn’t have an internal support) the cell ended up literally blowing its lid.
Thanks to the footage, the researchers were able to gain major insights into “key degradation modes including gas-induced delamination, electrode layer collapse, and propagation of structural degradation.” The hope is that this information will lead to major improvements in the design of lithium ion batteries that enhance their safety.
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