Thermal runaway is a dangerous, self-perpetuating process, where heat builds on heat and reaches very high temperatures. Researchers at Guangdong University of Technology in China, and their associates have conducted experiments triggering battery thermal runaway. This has broadened our understanding of the mechanisms behind lithium-ion battery fires.
Triggering Lithium-Ion Battery Thermal Runaway
Lithium-ion batteries may enter thermal runaway, even though this is a rare event. When they do, the results can be catastrophic. The Guangdong University scientists investigated three types of abuse that can cause this phenomenon. These triggers are mechanical, electrical, and thermal in nature.
When the team started their research, the associations between these triggers and battery thermal runaway were incomplete. The first phase of their study involved triggering battery runaway, under two different thermal and mechanical abuse scenarios:
- They examined the impact of different degrees of heat, and different nail penetrations and depths, at different levels of battery charge.
- They observed how voltage and temperature gradients, and the rate of temperature increases, relate to thermal runaway reactions.
What the Study of Thermal Runaway Revealed
- The thermal runaway temperature measured at the safety valve could be as high as 464 °C/ 867 °F.
- Smoking began 3 seconds after they nail-penetrated the battery 10 mm from the positive electrode. This took 7 times longer when they nail-penetrated the same distance from the negative electrode.
- The battery burst into flame twelve seconds after they nail-penetrated 10 mm from the positive electrode. This took 2.3 times longer when they nail-penetrated the same distance from the negative electrode.
- The peak temperatures were higher when they nail-penetrated deeper at the center of the battery, and the two positions we mention above.
- The damage to the battery was more severe after thermal abuse, than the nail penetration tests when observed under a microscope.
These findings are valuable inputs to the ongoing process of enhancing lithium-ion battery thermal safety. And eventually reducing the thermal disasters in new-energy vehicles, according to the researchers.
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