As lithium-ion (Li-ion) batteries continue to gain global popularity for energy storage and power supply units for equipment and electric vehicle systems, our industry is responsible for ensuring their safety through rigorous testing and protection systems. Since many of these batteries are used for safety-critical applications, developing methodologies for monitoring and assessing their safety has become a significant challenge.

FM Global recently published the results from its testing of the effectiveness of an off-gas detection system in an IEEE paper. Their testing aimed to evaluate the potential for off-gas detection systems capable of detecting battery solvent electrolyte vapors to provide early warning of Li-ion cells’ thermal runaway (TR). Sujit Purushotham, FM Global, published the results recently in a paper entitled “Evaluation of Off-Gas Detection in Li-ion Battery Energy Storage Systems.”

This testing is essential because when subjected to external electrical, mechanical, or thermal stress, a Li-ion battery may fail to operate within its intended electrical characteristics. It may experience a voltage and current anomaly, temperature rise, or a gas venting phenomenon. Monitoring these parameters could help detect incipient stages of TR and mitigate failure scenarios, even though there are practical limitations.

The primary aim of the testing was to assess the effectiveness of an off-gas detection system in providing early warning for the mitigation of TR in Li-ion battery systems. This was demonstrated through single-cell, battery pack, and battery rack tests. The tests involved applying electrical and thermal abuse to cells, and the system’s ability to prevent TR was evaluated by detecting the off-gas event and manually ending the abuse condition.

Overall, off-gas detection was found to provide an early warning signal that can be used to prevent TR in Li-ion battery systems under thermal or electrical abuse under realistic application conditions. Extreme abuse conditions, like mechanical damage, overcharging at a high C-rate, or rapid overheating, might not provide an adequate time window for the off-gas detection system; however, the paper concludes that the use of off-gas detectors in Li-ion battery systems will reduce the likelihood of thermal runaway.

“We are pleased to see an increased emphasis placed on electrolyte vapor detection in lithium-ion battery systems,” said Steve Cummings, director of Nexceris’ sensor business unit, which makes Li-ion Tamer. “It provides more validation for the layer of protection provided by off-gas detection systems, emphasizing detection and early warning. Our products are not the only solution, but they are a part of the overall strategy for lithium-ion battery safety.”

FM Global’s paper on Off-Gas Detection in Li-ion Battery Energy Storage Systems can be purchased from the IEEE Xplore website.