Lately, LG Chem introduced an interesting new material that suppresses battery thermal runaway. It is a composite substance whose electrical resistance changes depending on the temperature. In the early stages of overheating, it acts as a fuse, cutting off the electrical flow. The new material has already been verified as safe for application in mobile batteries and is ready to be tested in electric vehicle batteries. In today’s FOCUS ON, we will take a closer look at this thermal runaway suppression material.

Blocks electrical flow when temperature rises!

LG Chem’s Foundation Technology Research Center, a CTO-affiliated organization, announced on October 1, 2024, that they have developed a thermal runaway suppression material that can prevent EV battery fires. The material’s official name is ‘Safety Reinforced Layer (Hereafter referred to as SRL)’. SRL is a composite substance whose electrical resistance changes with temperature. Positioned between the battery’s cathode layer and the current collector, which serves as the electron pathway, the material reacts to temperatures above the normal range (from 90°C to 130°C) and changes its structure. This increases its electrical resistance and blocks the current, much like a fuse. This action helps prevent thermal runaway by cutting off the electrical flow in the early stages of overheating.

Thermal runaway, considered the primary cause of EV battery fires, is known to occur when the battery’s cathode and anode unintentionally come into contact, leading to a short circuit and heat buildup. During this process, the temperature can rise to 1,000°C within seconds, escalating into a fire. This has sparked high expectation for SRL, which can quickly block the reaction path in the early stages of overheating.

The material takes the form of a thin layer, just 1um (micrometer) thick, which is about 1/100th of a human hair. It features quick response to temperature, with its electrical resistance increasing by 5,000 Ω (ohms) for every 1°C rise. When the temperature goes down, its electrical resistance also drops, allowing the current to flow again. This characteristic is known as reversibility*.

*Reversibility: The property of a material that allows it to return to its original state after undergoing a change.

SPEC of SRL Verified Through Tests

LG Chem conducted battery impact and penetration tests to verify the safety of SRL. In the battery impact test, a 10 kg weight disc was dropped onto an NCM (Nickel, Cobalt, Manganese) battery for EVs. The results showed that all the batteries without this typical material caught fire, while 70% of the batteries in which SRL was applied did not catch fire. The remaining 30% experienced sparks, but these extinguished within a few seconds.

Next, in the battery penetration test, a nail was used to puncture a LCO (Lithium, Cobalt, Oxide) battery for mobiles. In the case of the regular batteries, 84% of them caught fire, while no fires occurred in those applied with SRL.

Continuous, Ongoing Development of Thermal Runaway Delay Materials

LG Chem’s development of the thermal runaway suppression material was not achieved overnight. Since 2009, the company has been steadily conducting research on the material. In 2022, LG Chem developed a battery pack plastic material that delays thermal runaway in EV batteries for the longest duration in the world. It is a flame-retardant engineering plastic with excellent heat resistance, and when applied to EV battery pack covers, it can block heat for a longer period than regular flame-retardant plastics. Additionally, it has superior dimensional stability, maintaining its shape during temperature changes. This is a 45 times better performance than existing flame-retardant plastics.

In 2023, the company, in collaboration with LX Hausys, developed a ‘Special flame-retardant thermoplastic continuous fiber composite material (Special Flame-retardant CFT)’. Let’s say we apply pressure and heat of over 1,500°C to this battery thermal runaway delay material. Even after 20 minutes, the battery will not melt or form holes, boasting the industry’s highest level of flame-blocking performance. Furthermore, it is rigid and shows minimal deformation under stress, making it suitable for use in larger battery components, such as the top and bottom covers of EV battery packs. This can effectively delay the spread of flames during fire, providing crucial time for driver evacuation and fire suppression efforts.

Safety Tests, the Final Step Before Mass-Production!

Other materials that respond to temperature changes have been incorporated inside battery cells. However, they displayed slow reaction speeds or low energy density. The newly developed SRL addresses these drawbacks.

In the future, SRL will be applied to mobile batteries for safety verification tests, followed by safety tests for large-capacity EV batteries. To ensure that it becomes a game-changer for the battery and EV industries, LG Chem will leverage their expertise in material design and patents to quickly move toward mass production.

Today, we looked at SRL, LG Chem’s thermal runaway suppression material which prevents heat generation by blocking electrical currents in the early stages overheating. It is an important technology that enhances safety, allowing EV users a more secure use of batteries. Let’s look forward to the material’s future, as it contributes to strengthening LG Chem’s battery competitiveness.