What is Thermal Runaway? A Closer Look at the Causes and Solutions That Protect Occupants

As the automotive industry accelerates toward an all-electric future, the engineering focus has expanded beyond range and horsepower to a more critical metric: occupant safety during a thermal runaway event. Central to this conversation is a phenomenon known as thermal runaway.

For OEMs and battery engineers, mitigating this risk is not just a regulatory hurdle—it is a fundamental requirement for the mass adoption of EVs.

What is Thermal Runaway?

Thermal runaway is a chain reaction within a lithium-ion battery cell where an internal or external failure causes temperatures to rise uncontrollably. This heat triggers further exothermic chemical reactions, creating a self-sustaining loop that leads to the rapid release of energy. Today’s battery packs are evolving quickly, utilizing different chemistries to speed up charging speeds or extending either theoretical range. With thes new battery chemistries, come new thermal runaway and mechanical cell pressure management challenges.

When a single cell fails, the intense heat and flame can transfer to neighboring cells. This “domino effect,” known as cell-to-cell (C2C) propagation, can compromise the entire battery pack, leading to the venting of toxic gases, smoke, and fire. These events are often self sufficient and can fuel a fire for hours and even days. Responding firefighters have had to get creative in their approach to putting out these fires, replying on special equipment, various chemicals, and tactics to ensure an EV fire is out and safe to move.

The Catalysts of Propagation

Thermal runaway typically stems from one of three types of situations:

• Mechanical: Physical damage from a collision or intrusion that punctures the cell.
• Electrical: Overcharging, rapid discharging, or internal short circuits caused by manufacturing defects or battery aging.
• Thermal: Exposure to extreme external heat or failure of the vehicle’s battery cooling system or increased temperature while charging

The Standard for Protection: Why Aerogel Barriers?

To meet stringent global safety standards—such as China’s GB38031 and the UN’s ECE/TRANS/180/Add.20—manufacturers must ensure that occupants have sufficient time to exit the vehicle safely. While traditional materials like mica or ceramic blankets have been used, next-generation battery architectures, cell chemistries, and pack longevity concerns require a more advanced solution: PyroThin^® aerogel thermal barriers.

Here is how our Aerogel Technology Platform^® outperforms conventional materials and other aerogels to protect vehicle occupants:

1. Stopping Propagation at the Source

Unlike materials that merely delay heat, PyroThin has proven that thermal propagation can be stopped at the cell-to-cell level. By acting as a nearly impenetrable thermal wall between cells, it contains the single failed cell from propagating into a pack-wide event.

2. Dual-Functionality: Thermal & Mechanical

One of the unique advantages of our aerogel technology is its ability to perform two roles simultaneously. It acts as both a thermal fire barrier and a mechanical compression pad.

Thermal: It provides industry-leading insulation even under the extreme pressures found within a battery pack.
Mechanical: Manages the daily stresses of cell swelling during charge/discharge cycles, maintaining the pack’s State-of-Health (SOH) over its entire lifecycle.

3. Maximizing Volumetric Efficiency

In the race for longer range, every millimeter counts. Aerogel barriers are ultrathin and lightweight. This enables engineers to achieve a higher cell-to-pack ratio, packing more energy into the same space without compromising the safety of the occupants.

4. Proven Performance at Scale

Not all aerogels are created equal. Our Aerogel Technology Platform is currently in volume production for major global OEMs, including the GM Ultium battery platform and others. Our engineering and prototyping teams have the knowledge and capabilities to help OEMs and battery pack manufacturers design the best thermal barrier for their unique application.

Conclusion

Thermal runaway is a complex challenge, but with the right materials and partner, it is a manageable one. By integrating PyroThin aerogel barriers, vehicle manufacturers aren’t just adding a cell separator, they are implementing a high-performance safety system designed to protect lives and build trust in the future of electric mobility.

Discover how our technical and prototyping teams can support your battery safety goals with PyroThin. Contact us today!