SLAC discovers that cracks in battery materials in extremely cold environments affect battery performance

It is well known that lithium-ion batteries do not perform well in cold weather. This will affect some important applications, such as starting an electric car in a Wisconsin winter and operating a drone on Mars. According to foreign media reports, the U.S. Department of Energy's SLAC National Accelerator Laboratory has discovered an overlooked aspect of this problem: when lithium-ion batteries are stored in an environment below zero degrees Celsius, some parts of the battery will crack and separate from the surrounding materials, thereby reducing the electrical storage capacity.

(Image source: SLAC)

SLAC researchers Yijin Liu and Jizhou Li made the discovery by observing the performance of the cathode in cold weather. When the battery is running, electrons flow into the cathode part. Initial studies found that storing the cathode below zero degrees Celsius caused the battery to lose 5% more capacity after 100 charges, compared to batteries stored in warmer environments.

To understand why, the researchers combined an X-ray analysis method from the Stanford Synchrotron Radiation Light Source with a machine learning technique that Li has been working on for the past few years. This combination allows the identification of individual positive particles. This means the team can study thousands of particles simultaneously, whereas the eye can only identify a few.

Overall, these methods show that cold temperatures are shrinking the meatballs inside the cathode, cracking them in the process or exacerbating existing cracks. And because materials expand and contract differently in response to temperature changes, the extreme cold can also cause the cathode to separate from the surrounding material.

The findings point to some possible solutions. By looking for materials that can better handle temperature, scientists could address the material separation problem. Since all batteries expand and contract when heated and cooled, this could help other batteries, too. By engineering different particle structures within the battery, especially building with smoother, less meatball-like particles, it could help prevent material cracking and boost the long-term capacity of lithium-ion batteries.