LG stops EV battery fires with new thermal runaway prevention material that can be produced en masse

While Tesla's statistics bust the popular myth that EV battery fires are a common occurrence, there is no denying that once they happen, the pack is very hard to put out.

It takes many times more gallons of water to extinguish a fire caused by an electric vehicle battery, as the packs go into spontaneous combustion mode because of the thermal runaway that no regular fire extinguisher can deal with.

Before Hurricane Helene hit the Florida coast, for instance, Governor DeSantis warned citizens with electric cars to take them to higher grounds. In the aftermath, the Dunedin Fire Rescue department tweeted "if your electric vehicle came in contact with flood water, don’t charge or start it," advising that flooded EVs should be inspected by firefighters first.

As if to prove the point, the battery pack of one such flooded Model X ignited after coming into contact with the corrosive saltwater as it was sitting in the garage, and burned the whole structure down. Previous hurricanes have also led to a disproportionate number of electric vehicles catching fire, and one Tesla even self-combusted months after being flooded and brought to a junkyard. It took dunking the burning Model S into a pool of water to extinguish the flames, all because of the thermal runaway that can spread the short-circuiting of electrodes in isolated cells to the whole pack.

Thermal runaway is precisely what a new material from LG Chem nips in the bud. LG's researchers have created a composite that can quickly respond to temperature fluctuations by drastically altering its electrical resistance. The material can be rolled into a thermal runaway prevention layer that is only 1μm thick. It sits between the cathode and the aluminum foil that serves as a current collector for the electrons in a lithium battery to travel.

The safety reinforced layer is made of polythiophene that has been designed to change its molecular structure at temperatures above the typical 90°C - 130°C battery operating range.

The rising temperature brings a rapid onset of electrical resistance increase to the tune of 5,000 ohms for each 1°C change. The maximum that the temperature-sensitive material can hit is 1,000 times the resistance during normal battery operating temperatures, effectively shutting off the electric current during ignition. The layer thus acts as a viable fuse for each individual cell that stops the flow of electricity and prevents thermal runaway, hence EV battery fire, from catching on and spreading.

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.

The LG Chem researchers put the new battery safety material to the test by puncturing and dropping weights on batteries with or without it. None of the cells made with the modified polythiophene layer went into a full thermal runaway state, whereas all the regular batteries in the drop test, and 84% of those in the puncture trial, burned out completely.

The icing on the battery fire prevention cake is that the new material can be quickly scaled up for roll-to-roll mass production. LG has already exited the safety verification stage for phone batteries made with the protective layer, and is planning to certify it for use in larger electric vehicle packs next year.

"This is a tangible research achievement that can be applied to mass production in a short period of time," said the CTO of LG Chem, rejoicing that the material invention will "enhance safety technology to ensure customers can use electric vehicles with confidence."