According to professor Nancy Sottos, the materials in a battery cell cannot truly expand and contract as they would when unconstrained, which causes mechanical stress. “The stress and strain can actually change the way a battery functions, and usually in a negative way – like the capacity will fade, or it will cause small cracks that cause reactions you don’t expect”.
Chemistry professor, Andrew Gewirth said: “Stress and strain have been measured separately, but no one has even looked at them together before.”
The researchers have dubbed their measurement ‘electrochemical stiffness’, defined as the ratio of stress to strain.
The research has already revealed that there is a spike in stress just before the lithium is taken up by the anode.
“We didn’t expect there would be a barrier or an impediment to the lithiation process,” prof Gewirth said. “First, it shows us where the impediment is for charging. Now that we know where it is, we can work on ways to fix it. Second, it gives us a better idea of how the battery actually works.”
“These experiments are giving insight that it’s not just an electrochemical issue; it’s also a mechanical issue,” prof Sottos said. “We think we are beginning to understand some of the factors that are hindering faster battery charging.”
This may lead to batteries that charge faster and have greater capacity that could boost portable electronic devices and electric cars.