LG Chem announced that its Platform Technology R&D team has developed a temperature-responsive Safety Reinforced Layer (SRL), a material designed to suppress thermal runaway. In collaboration with Professor Lee Minah’s team from the Department of Battery Engineering at POSTECH, the material was analyzed, while safety verification was conducted in partnership with LG Energy Solution.
The open access research findings are published in Nature Communications.
The thermal runaway suppression material developed by LG Chem is a composite material that changes its electrical resistance based on temperature, acting as a “fuse” that blocks the flow of electricity in the early stages of overheating.
The research team created this thermal runaway suppression material in the form of a thin layer 1 micrometer (1μm) positioned between the cathode layer and the current collector 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, with its electrical resistance increasing by 5,000 ohms (Ω) for every 1 °C rise in temperature. The material’s maximum resistance is more than 1,000 times higher than at normal temperatures, and it also features reversibility, meaning the resistance decreases and returns to its original state, allowing the current to flow normally again once the temperature drops.
Thermal runaway, a leading cause of electric vehicle battery fires, 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 (LCO) 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 incidents.
In an impact test on Nickel Cobalt Manganese (NCM) batteries for electric vehicles, where a 10kg weight was dropped onto the batteries, all of the standard batteries caught fire. In contrast, 70% of the batteries equipped with the thermal runaway suppression material did not ignite at all, while 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 successfully developed a material that resolves such issues, backed by their expertise and patented material design, allowing for rapid application in mass production processes.
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.