Hot stuff: The NRC pioneers leading-edge lithium-ion battery safety assessment tool

Good things come in small packages – and a tiny lithium-ion battery (Li-ion) heater developed by the NRC and Transport Canada proves the point. As a realistic, reproducible and minimally invasive approach, the thermal runaway initiation mechanism (TRIM) is expected to become a global standard for Li-ion battery safety testing.

The TRIM heater sends a powerful jolt of heat onto a single lithium cell, triggering a self-sustaining exothermic reaction (an exothermic reaction is one that releases energy). The aim is to gauge the cell's ability to resist failure from cascading to other cells within a larger battery pack (phenomena known as 'thermal runaway' and 'thermal propagation'). While the current failure rate of Li-ion batteries is less than 1 in 10 million, recent safety incidents in electric vehicles, as well as aerospace and consumer electronics, have pointed to a need for better understanding of Li-ion safety. In addition, soaring electric vehicle sales and increasing energy densities in lithium-ion battery packs are raising new safety concerns. By 2040, the world could see 530 million electric vehicles—up from 2 million in 2018—all using lithium-ion batteries.

Small element, big impact

The NRC's Vehicle Propulsion Technologies program helps its partners to develop the technologies needed to be leaders in the growing supply chains associated with vehicle electrification. From this perspective, TRIM is an ideal tool for alleviating potential safety concerns in an environment where regulators everywhere want a reliable test for evaluating compliance of battery pack safety systems. But developing the technology posed a unique technical challenge for the multidisciplinary team at the NRC. Scaling down the technology and transferring heat from the miniature element to a battery cell had custom heating manufacturers scratching their heads.

"We started by hand shaping the elements ourselves to determine the proper characteristics," says NRC researcher Steven Recoskie. "After several design revisions over the past 5 years, we're now able to mass produce a working product."

The NRC battery testing and optimization team has decades of experience in battery safety and performance testing in a range of industries including the military, consumer products, and industrial sectors. The development of TRIM provides a prime example of their capacity to address specific issues of concern, in this case an issue that has been highlighted by global regulators. TRIM results can be used to identify how packaging materials, cell spacing, and thermal management strategies can be deployed to reduce failures.

"While we can perform tests to specific standards, our specialty is in creating customized solutions," underscores Recoskie. "In collaboration with international safety working groups, our goal is to study and improve detection and mitigation strategies for lithium-ion battery failures – and ultimately maintain the excellent safety record of electric vehicles."

A hot market

Transport Canada's Kyle Hendershot, Senior Regulatory Development Engineer, adds that the NRC's expertise in this field is showcased in the new United Nations Economic Commission for Europe Global Technical Regulations (GTR) for electric vehicle safety.

"The NRC's work on developing the test procedure and the mechanism is definitely world leading," says Hendershot. "Their support and technical skills have been invaluable in helping the GTR discuss issues associated with electric vehicles – and have positioned Canada as a driver in some aspects of global technical regulations."

The team recently performed a full-scale TRIM test on an electric vehicle while it was fully operational. "This is the first time such an assessment was done on a global stage and shared with the world," adds Hendershot, noting that the NRC's work in this area is currently years ahead of anyone else.

In addition to Canada, several other countries are actively participating in the development of the GTR under the framework of a larger international agreement that includes 38 signatories, along with the European Union. The NRC has received numerous requests for the TRIM technology from researchers and industry, with potential industry partners in the United States and China having expressed interest. It is already being used in Europe, while licence agreements for agencies in Japan, Germany, and southern Ontario have recently been signed.

"TRIM is recognized internationally as the most reliable research tool for testing thermal runaways in lithium-ion cells," says Hendershot. "While it was created for the automotive industry, it has applications in other sectors as well, since thermal runaway can occur in any Li-ion cell."

And in this hot market, TRIM is set to be a runaway success.