According to Kim, workers who fled the blaze said the fire broke out when a single battery cell caught fire, triggering a series of explosions among some of the 35,000 lithium battery cells stored on the second floor of the factory.
Lithium batteries can cause fires when the internal layers are compressed, causing a short circuit. The layers can be compressed by a sudden impact, such as during a vehicle collision, or by the gradual swelling of the batteries due to regular use.
Lithium is a metal that can store large amounts of energy in a small space, which is why it is attractive as a battery material. But that also means there is a lot of energy available that can be converted into heat and even flame in the event of a short circuit. Lithium battery fires have been a growing problem in the United States and elsewhere and are an industry-wide concern for battery manufacturers.
Aricell, which owns the Hwaseong plant, produces batteries often used to power electricity grids and other utilities.
On Monday, intense flames, toxic smoke and the risk of further explosions hampered firefighters’ efforts to search for missing workers. Television footage of the blaze showed large flames and thick clouds of smoke rising from the factory. Footage taken after the fire was extinguished showed the building burned out, with its roof collapsed.