Lithium-ion batteries produce faint sounds as they charge, discharge, and degrade. But until now, nobody could interpret those sounds to detect when a battery might be about to lose power, fail, or burst into flames.
Now, MIT engineers have found a way to do that, even with noisy data. The findings could provide the basis for relatively simple, totally passive, and nondestructive devices that could continuously monitor the health of battery systems like those in electric vehicles or grid-scale storage facilities.
“Through some careful scientific work, our team has managed to decode the acoustic emissions,” says Martin Z. Bazant, a professor of chemical engineering and mathematics. They were able to classify them as coming from gas bubbles generated by side reactions or from fractures caused by expansion and contraction of the active material, two primary mechanisms of degradation and failure.
The team coupled electrochemical testing of working batteries with recordings of their acoustic emissions, using signal processing to correlate sound characteristics with voltage and current. Then they took the batteries apart and studied them under an electron microscope to detect fracturing.
With Oak Ridge National Laboratory researchers, the team has also shown that acoustic emissions can warn of gas generation before thermal runaway, which can lead to fires. As Bazant says, it’s “like seeing the first tiny bubbles in a pot of heated water, long before it boils.”