LG Chem’s platform technology research and development team developed a temperature-responsive Safety Reinforced Layer, a material designed to suppress thermal runaway.
The material was analyzed in collaboration with Professor Lee Minah’s team from the department of battery science at the Pohang University of Science and Technology. The safety verification was conducted in partnership with LG Energy Solution.
Those research findings were published online in the September edition of Nature Communications, one of the world’s leading scientific journals. The paper is titled Thermal Runaway Prevention through Scalable Fabrication of Safety Reinforced Layer in Practical Li-ion Batteries.
The thermal runaway suppression material developed by LG Chem is a composite material that changes its electrical resistance based on temperature. It acts as a fuse that blocks the flow of electricity in the early stages of overheating.
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The research team created this thermal runaway suppression material in the form of a thin layer, just 1 micrometer thick — about 1/100th the thickness of a human hair — positioned between the cathode layer and the current collector (an aluminum foil that acts as the electron pathway) in the battery. When the battery’s temperature rises beyond the normal range, between 90°C and 130°C, the material reacts to the heat, altering its molecular structure and effectively suppressing the flow of current.
This thermal runaway suppression material is highly responsive to temperature. Its electrical resistance increases by 5,000 ohms for every 1°C rise in temperature. The material’s maximum resistance is more than 1,000 times higher than at normal temperatures.
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It also works in reverse. That means that once the temperature drops, the resistance decreases and returns to its original state, allowing the current to flow normally again.
Thermal runaway is a leading cause of electric vehicle battery fires. It occurs when the cathode and anode inside the battery unintentionally come into direct contact, causing a short circuit and generating heat. Within seconds, the temperature can rise to nearly 1,000°C, leading to a fire.
The thermal runaway suppression material is expected to be effective in preventing fires by quickly blocking the reaction path at the early stages of overheating.
In both battery impact and penetration tests, the batteries equipped with the thermal runaway suppression material either did not catch fire at all or extinguished the flames shortly after they appeared, preventing a full-blown thermal runaway event.
In a penetration test involving mobile lithium cobalt oxide batteries, where a nail was used to puncture the battery, only 16% of regular batteries did not catch fire. However, none of the batteries with the thermal runaway suppression material experienced any fire.
In an impact test on nickel cobalt manganese batteries for electric vehicles, a 10-kg weight was dropped onto the batteries. All the standard batteries caught fire. In contrast, 70% of the batteries equipped with the thermal runaway suppression material did not ignite at all; the remaining 30% saw flames, but they were extinguished within seconds.
While previous methods involved placing temperature-responsive materials inside the battery cell, they often faced issues with slow reaction times or reduced energy density. LG Chem, however, has developed a material that resolves such issues.
LG Chem has completed safety verification tests for the thermal runaway suppression material in mobile batteries and plans to continue safety testing for large-capacity electric vehicle batteries through next year.
Lee Jong-gu, CTO of LG Chem, said, “This is a tangible research achievement that can be applied to mass production in a short period of time. We will enhance safety technology to ensure customers can use electric vehicles with confidence and contribute to strengthening our competitiveness in the battery market.”
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