Lithium batteries are set to power the world—and pose new fire risks

But the very traits that make lithium game changing for energy storage can pose overpowering challenges should the batteries ever catch fire. Incidents involving lithium-battery fires are becoming more common around the world, raising safety concerns.

Water isn’t always an effective combatant for certain types of lithium-battery fires, leaving little option other than waiting things out or using costly suppressants, firefighting experts say. Combating fires involving lithium-batteries can be difficult due to the emission of toxic gases. Then there is the heat: the lithium produces searing temperatures more akin to a welding torch than a typical blaze, capable of slicing through protective gear or an extremity.

The world saw the risks of lithium-battery fires on Monday in South Korea, where at least 23 workers died in one of the country’s worst industrial accidents in recent memory. Local investigators are still determining the blaze’s exact cause. Some 35,000 battery cells were thought to have been stored on-site—and video footage of the fire showed occasional flashes that produced thunderous booms like a detonated bomb.

On Tuesday, Park Soon-kwan, chief executive of the battery maker Aricell, apologized for the incident. He added the company had complied with all required safety precautions and training, and would cooperate fully with authorities. Later in the day, local police charged Park, along with four other company officials, for causing death and injury due to occupational or gross negligence. Aricell didn’t have an immediate comment.

Kim Young-suk, who owns a beef-bone soup restaurant across the street from the Aricell factory, heard a loud explosion around 10:30 a.m. Monday, followed by a whoosh of heat lashing through the vicinity. Thick smoke hurled toward the skies. Metal debris flew off the two-story building. The windows of the neighboring fishing-appliance store got smashed.

Kim rushed to turn off the restaurant’s gas valves, locked the door and fled the site. She didn’t reopen on Tuesday. “It was so extremely, extremely scary," she said. “We couldn’t stay there because of the fire."

Battery fires are a growing concern for firefighters worldwide, prompting calls for regulation and public-education campaigns. So-called “lithium-ion" batteries are rechargeable and widely used in smartphones, PCs and EVs—and are the subject of the bulk of such fires, often due to overheating. But the South Korean factory fire involved “primary lithium" batteries that aren’t rechargeable and are typically used in smart-grid electricity networks and military equipment.

For instance, extinguishing a lithium-ion battery fire for an EV takes longer and about three times as much water than a regular vehicle, on top of the exposure to carcinogenic chemicals, said Greg McConville, the national secretary of the United Firefighters Union of Australia. The fire’s ignition is more intense than an oxy-acetylene torch, which can be roughly 5,000 degrees Fahrenheit or more, or about five times hotter than many house fires.

“It will literally cut through a firefighters’ protective clothing and their leg if it’s coming out from underneath their vehicle," McConville said.

Sometimes the safest option is to let a battery fire burn. That was in the case in 2021, when a Tesla battery caught fire while being installed at an Australian power storage facility. The fire spread to another battery. Responders allowed the blaze to burn out over six hours, while keeping nearby units cool. No one was injured.

Water, in some cases, could even worsen a battery fire, as it could produce explosive chemical reactions because lithium metals react violently to moisture, said Sunnie Haam, a professor of fire-protection engineering at the University of Seoul. Coolants, such as liquid nitrogen, could be used instead of water, but it is very expensive for every fire station to purchase in big volumes and to deploy them in sufficient quantities to quell a large-scale fire, Haam said.

“I don’t think there is any fire station in the world with sufficient supplies," Haam said.

In her evaluation of South Korea’s response Monday, Haam thought it was a wise choice to wait for the flames to burn out on their own. Firefighters used water once it was deemed safe to do so, and then quickly started rescue operations, Haam said.

Lithium is widely viewed as a key future energy source, given its outstanding ability to retain high amounts of energy compared with other metals, said Tak Yong-sug, a chemical engineering professor at South Korea’s Inha University who specializes in battery-materials research. The properties of lithium that make it suitable for energy storage also pose risks, but the metal in its various forms has been harnessed to operate safely for a variety of uses, Tak said.

“Lithium is a coveted resource, and countries worldwide are making efforts to ensure access to lithium supply," Tak said.

Stuart Condie contributed to this article.

Write to Jiyoung Sohn at jiyoung.sohn@wsj.com