How likely is an electric vehicle battery to spontaneously ignite and explode? According to some analysis, gasoline vehicles are almost 30 times more likely to catch fire than electric vehicles. However, recent incidents of electric vehicles catching fire in the park have raised questions among many consumers and researchers. How can these rare events occur?
Heat leak: a well-known phenomenon
Researchers have long known that high electrical currents can cause a “thermal leak” – a chain reaction that can cause a battery to overheat, catch fire and explode. However, without a reliable method for measuring the currents within a battery at rest, it is not clear why some batteries experience thermal leakage, even when an electric vehicle is parked.
“We are the first to capture real-time 3D images that measure changes in the state of charge at the particle level inside a lithium-ion battery after it has been charged.” – said Nitash Balsara, principal investigator of the Materials Science Department.
New imaging technology makes local flows visible
Using an imaging technique called “X-ray microtomography,” scientists at Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley have shown that the presence of large local currents in resting batteries after fast charging could be one of the causes of the thermal leak.
“The exciting thing about this work is that Nitash Balsara’s group doesn’t just look at images – they use the images to determine how batteries work and change over time.” “This study is the culmination of many years of work,” added co-author Dilworth Y. Parkinson, associate scientist for photon science operations at Berkeley Lab’s Advanced Light Source (ALS).
3D microtomography experiments conducted at the Advanced Light Source allowed researchers to identify particles that produce current densities of up to 25 milliamperes per square centimeter after rapid charging while a battery is at rest. For comparison, the current density required to charge the test battery in 10 minutes was 18 milliamperes per square centimeter. (Source: Nitash Balsara and Alec S. Ho/Berkeley Lab)
synthetic
This study provides surprising evidence of rare occurrences of heat loss within a lithium-ion battery at rest. Researchers found that the local currents within a battery at rest after fast charging were surprisingly large.
These findings could help develop improved safety protocols for electric vehicle batteries. However, much remains to be done before this approach can be used for this purpose.
Main lessons
| Important lessons | details |
|---|---|
| Fire hazard with electric vehicles | Gasoline vehicles are almost 30 times more likely to catch fire than electric vehicles. |
| Thermal leak | High electrical currents can cause a “thermal leak” – a chain reaction that can cause a battery to overheat, catch fire and explode. |
| Imaging technology | An imaging technique called “X-ray operand microtomography” was used to measure currents inside a stationary battery. |
| Local currents | The presence of significant local currents in the batteries at rest after fast charging could be one of the causes of the thermal leak. |
| Implications | These findings could help develop improved safety protocols for electric vehicle batteries. |
For better understanding
1. What is “thermal leakage” in an electric vehicle battery?
“Thermal leak” is a chain reaction that can cause a battery to overheat, catch fire and explode. It can be caused by high electrical currents.
2. Why do some electric vehicles catch fire when parked?
Large local currents within the batteries at rest after fast charging could be one of the causes of the thermal leak.
The researchers used an imaging technique called “X-ray operando microtomography” to measure currents within a resting battery.
4. What is “X-ray operando microtomography”?
It is an imaging technique that captures 3D images in real time and measures changes in the state of charge at the particle level inside a lithium-ion battery after it has been charged.
5. What are the implications of this discovery?
These findings could help develop improved safety protocols for electric vehicle batteries. However, much remains to be done before this approach can be used for this purpose.
The information in this article comes from a study by scientists at Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley, published in the journal ACS Nano.
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