NRC lithium-ion battery safety test sparks international acclaim

Lithium‑ion batteries will soon be one of the world's most common sources of electrical energy storage. Trillions of cells are already powering everything from tiny electric toothbrushes to massive electric vehicles (EVs) such as transport trucks. These batteries are generally safe, but if they're defective or become damaged, an uncontrolled self-heating state (thermal runaway) in a single cell may spark a chain reaction of fire or explosions.

The good news is these events are rare, you have less chance of seeing a high-quality lithium‑ion battery fail (reports estimate 1 in 40 million) than you do being struck by lightning in your lifetime (1 in 15,300 according to National Oceanic and Atmospheric Administration statistics on how dangerous lightning is). A typical vehicle has thousands of cells, and with EV production growing exponentially and lithium‑ion batteries being used in new applications, safety testing is becoming increasingly critical.

Even better news is that the National Research Council of Canada (NRC) has developed a testing method to study how a single‑cell thermal runaway failure can spread through battery modules and packs. It involves applying a jolt of heat to one cell, and using an NRC-patented mechanism that monitors its cascading effects on a battery pack. Known as trim (for Thermal Runaway Initiation Mechanism), the device tests lithium‑ion batteries against an international safety standard for EVs (ISO 6469-1:2019/AMD 1:2022).

trim can be used by manufacturers to gauge the safety of their designs and products and by researchers to study thermal runaway mechanisms. It can also help regulators develop safety guidelines and best practices as well as owners of commercial EVs to ensure their vehicles meet safety specifications.

The NRC takes battery safety very seriously. "We've invested considerable time and effort building a specialized team dedicated to battery safety and performance. And this unique product has come out of that," says Guillaume Imbleau‑Chagnon, Senior Project Manager with the Clean and Energy-efficient Transportation program.

Containing the threat

At the Battery performance and safety evaluation research facility, trim is ideal for assessing the risk of thermal runaway at a full system level because it can be adapted to all system designs. It uses a tiny heating element to determine how batteries react to rapid external heating and to track how single‑cell thermal runaway failure can spread through a vehicle's battery modules and packs. The trim tool sends a pulse of heat into a single lithium cell without rupturing its wall and damaging adjacent cells.

"While the original mechanism  launched in 2016 worked for 90% of the cases studied, we realized we needed to adapt it to other specialized uses and develop new versions of the heating elements," says the NRC's Steven Recoskie, Research Officer, Battery Testing and Optimization group, Energy, Mining & Environment Research Centre. "The heaters are now thinner and more flexible so can bend around cells and fit into tighter spaces." That means they can be used in a range of industries, including automotive, military, aeronautical, marine and energy storage.

trim also allows researchers to observe an EV's safety response. "The biggest benefit of this technology is that it can be inserted into a fully functional system without affecting a vehicle's operation," he adds. "In several full EV tests, we took out the battery pack, inserted trim, reinstalled the pack, turned on the ignition and could drive the vehicle without triggering any warnings."

Firing up the solution

Demand for the NRC-developed rapid heating method is 'on fire' around the world, particularly since it is now part of the international ISO standard. In addition, the trim tool is recognized as the most robust testing method on the market. It can be used by research institutions, product developers, cell manufacturers, vehicle manufacturers and more.

Kyle Hendershot, Senior Regulatory Development Engineer at Transport Canada, supported the inclusion of the method in the ISO standard. He also heads a Canadian delegation with the United Nations World Forum for Harmonization of Vehicle Regulations (WP.29).

"The National Research Council of Canada's work has been crucial for Canada's position on electric vehicle safety in general and thermal propagation specifically," he says. "The industry has benefitted from a test procedure requiring minimal vehicle modification that can be used for both vehicle development and compliance applications." The improvements in vehicle safety design will also lead to safer EVs on the road.

Imbleau‑Chagnon reports that the demand for trim is increasing as lithium‑ion batteries become more common, and their application is expanding because of the introduction of novel electric vehicles and consumer products. "As the National Research Council of Canada attracts more clients, we're looking to partner with manufacturers and cater to larger orders."