Battery plant fire caused by 'thermal runaway' explosion: Expert

The central and regional governments carried out inspections of battery-making facilities after Monday's blaze was attributed to the "thermal runway" phenomenon that can affect lithium batteries.

Kang Kyung-sung, the first vice minister of trade, industry and energy, inspects safety management system and manufacturing facilities of Vitzrocell, a domestic lithium battery company in Dangjin, Chungnam on Tuesday. [YONHAP]

Korea’s central and regional governments have launched emergency safety inspections of battery-making facilities nationwide Tuesday, alarmed by the latest fire calamity at a battery cell plant that experts attributed to a phenomenon called "thermal runaway."

Given that the apparent cause is a common risk factor at battery cell-making factories, the government is trying to prevent a recurrence. Thermal runaway occurs when the temperature of a lithium battery escalates uncontrollably, triggering a chain reaction that may lead to a fire or an explosion characterized by rapid expansion.

The Monday blaze in Hwaseong, Gyeonggi, claimed over 20 lives, most of whom were Chinese nationals, working at Aricell, a Kosdaq-listed maker of lithium batteries.

The Ministry of Trade, Industry and Energy inspected Vitzrocell, the country’s largest manufacturer of single-use lithium batteries located in Dangjin, South Chungcheong, in cooperation with the National Fire Agency.

The ministry will extend the scope of the probe to include more lithium battery makers and operators of energy storage systems, while the city governments of Hwaseong, Gwangju and Busan also started their own inspections of battery makers in their respective regions.

The blaze originated from an explosion of lithium batteries on the second floor of Building 3 at the Aricell factory, according to fire authorities. This factory was used to inspect and package batteries for military clients. Some 35,000 batteries, including cylindrical ones measuring 45 centimeters (18 inches) in height and 30 centimeters in diameter, were stored in the facility.

Lithium batteries are commonly used in devices such as smart grid meters, an electronic device that records consumption of electricity and provides detailed usage data. Aricell's single-use units are primarily used as power sources for smart meters and remote metering devices in smart grids.

Lithium battery fires typically result from the "thermal runaway" phenomenon. The batteries consist of an anode, cathode, separator and electrolyte. If the separator is damaged, the anode and cathode can come into contact, causing overheating that may worsen to combustion or an explosion. This uncontrolled energy release can amplify temperatures and trigger a chain reaction of explosions.

"We heard crackling sounds followed by loud bangs for about an hour," eyewitnesses at the scene said, while also reporting seeing sparks fly from the burning factory like fireworks.

"When a lithium battery fire occurs, the temperature can rise to between 600 degrees Celsius [1,112 degrees Fahrenheit] and 1,000 degrees Celsius, making it difficult to extinguish," said Baek Dong-hyun, an honorary professor of fire and disaster prevention at Gachon University.

As lithium batteries burn, they emit large amounts of flammable gases such as oxygen and hydrogen, making it difficult to extinguish the outbreak with water, powder or extinguishers. Although the fire authorities prepared sand and expanded vermiculite, the batteries had already combusted by the time firefighters arrived.

Workers there initially attempted to use fire extinguishers to control the blaze, but the standard extinguishers proved to be ineffective.

"CCTV footage showed white smoke emerging from the battery before it ignited and fire engulfed the entire workspace in about 15 seconds. Workers, panicking, tried to put it with extinguishers, but to no avail," Cho Sun-ho, Gyeonggi fire official, said.

Firefighters prevented the blaze from spreading to nearby factories using water and suppression agents to control the flames.

"While the blaze kept erupting, the radiant heat continued to affect adjacent buildings, creating the potential for additional fires. We worked to cool the area with water to stop the spread," Kim Jin-young, the head of the fire prevention department at Hwaseong Fire Station, said.

The release of toxic gases, such as benzene and hydrogen fluoride, during the explosions further exacerbated the damage.

The emission of toxic gases and the risk of building collapse prevented firefighters from dispatching rescue teams into the building until 2:30 p.m., more than four hours after the blaze started. After completing a safety assessment, search operations began around 3 p.m.

The National Fire Agency and National Police Agency plan to conduct a joint investigation on Tuesday to determine the exact cause.

"We are investigating the cause of the fire based on testimonies that it started explosively from a single battery cell," the Hwaseong Fire Station's Kim noted.

"While lithium battery fires can have various causes, they are particularly prone to ignition when exposed to high temperatures, high pressure or high humidity, owing to the battery's high reactivity," said Nam In-ho, a professor of chemical engineering at Chung-Ang University.

BY LEE BO-RAM, PARK EUN-JEE, CHOI HAE-JIN [choi.haejin@joongang.co.kr]