Gas Detectors Protect Against Thermal Runaway

A significant problem associated with lithium-ion (Li-ion) battery systems is thermal runaway, a process in which a battery undergoes uncontrolled exothermic decomposition.¹ Though thermal runaway in Li-ion batteries is an uncommon issue; it can have severe effects, including the spontaneous combustion of electric vehicles and explosions in stationary energy storage systems.^2,3

Research suggests that the majority of instances of thermal runaway in Li-ion systems happen when there is no known damage to the battery. Such events can, as a result, only be effectively alleviated through the use of robust early detection systems. This is where gas sensor technology is essential.

The Importance of Gas Sensors for Detecting Thermal Runaway

Detecting thermal runaway as rapidly as possible is crucial because it is an uncontrolled chain reaction. A multi-phase process, thermal runaway begins with the failure of a single cell in a battery pack. The cell typically vents evaporated electrolytes at high temperatures when this occurs.

Gases, smoke, and pressure were found to serve as reliable rapid indicators of such a failure, while voltage and temperature often react slowly to this initial venting.⁴

Pressure sensors suffer from several drawbacks that minimize their application in battery systems, though they provide a quick response to cell venting. Pressure sensors typically exhibit a poor signal-to-noise ratio. They are too sensitive to pack volume/venting effects for thermal runaway detection systems, though they are small, durable, and inexpensive.

Gas sensors, on the other hand, offer excellent performance. Hydrogen and carbon dioxide gas have proven to be dependable indicators of such failures, while different battery chemistries result in different chemical signatures during initial venting before thermal runaway.

CO₂ and H₂ sensors offer:

• Rapid response times (5 - 8 seconds for CO₂ and <1 - 3 seconds for H₂)
• Stability for long-term applications
• Strong signal-to-noise ratios
• Excellent specificity (CO₂ sensors have no known cross-sensitivity, and H₂ sensors are only cross-sensitive to helium, which is not present in battery packs)
• Reduced risk of type 1 and type 2 faults

Using Gas Sensor Technology to Develop a Robust Thermal Runway Detection System

Over recent years, industrial CO₂ and H₂ sensor technologies have been developed to provide robust and versatile detection methods for thermal runaway in Li-ion battery systems.

This began with a series of two engineering test platforms comprising various sensors with a digital output. The researchers discovered how to characterize the plumes of ejecta from failing cells to detect when cell failure has occurred when working closely with OEMs.

Using these results, Amphenol has now announced the Robust Early Detection of Thermal Runaway (REDTR) system. In addition to monitoring temperature, pressure, and relative humidity to provide accurate detection of the early signs of thermal runaway in Li-ion battery systems, REDTR relies on H₂ and CO₂ sensors.⁵

Future Research

Gas detectors are not indestructible, even though they can be robust. H₂ and CO₂ detectors will stop working at temperatures above 150-165 °C in a failing battery pack.

These sensors can, however, gather valuable data before this happens, offering OEMs a window into what exactly is happening at the cell level and a powerful diagnostic tool to cause these unexplained thermal runaway events.

The team at Amphenol Advanced Sensors is hopeful that their innovative sensors will offer rapid response and danger mitigation in the event of thermal runaway and ultimately help eliminate the root causes of cell failure and render thermal runaway obsolete.

References and Further Reading

1. Feng, X., Ren, D., He, X. & Ouyang, M. Mitigating Thermal Runaway of Lithium-Ion Batteries. Joule 4, 743–770 (2020).
2. News ·, C. B. C. Despite Île-Bizard explosion, expert says electric cars safer than others | CBC News. CBC https://www.cbc.ca/news/canada/montreal/experts-say-electric-cars-safer-than-others-1.5230969 (2019).
3. UL Firefighter Safety Research Institute, McKinnon, M., DeCrane, S. & Kerber, S. Four Firefighters Injured in Lithium-Ion Battery Energy Storage System Explosion -- Arizona. https://fsri.org/research-update/report-four-firefighters-injured-lithium-ion-battery-energy-storage-system (2020) doi:10.54206/102376/TEHS4612.
4. Koch, S., Birke, K. P. & Kuhn, R. Fast Thermal Runaway Detection for Lithium-Ion Cells in Large Scale Traction Batteries. Batteries 4, 16 (2018).
5. Thermal Runaway Detection in Lithium Ion Batteries - Application Spotlight. https://www.amphenol-sensors.com/en/product-spotlights/3498-thermal-runaway-sensor.

This information has been sourced, reviewed and adapted from materials provided by Amphenol Advanced Sensors.

For more information on this source, please visit Amphenol Advanced Sensors.