The group developed a battery that uses a silicon nanoparticle composite material on the negatively charged side of the battery and a new way of holding the composite together.
“This work is particularly new to self-healing materials research because it is applied to materials that store energy,” said Scott White, professor of aerospace engineering. “It’s a different type of objective altogether. Instead of recovering structural performance, we’re healing the ability to store energy.”
The negatively charged electrode, or anode, inside the lithium-ion batteries are typically made of a graphite particle composite. These batteries work well, but it takes a long time for them to power up, and over time, the charge does not last as long as it did when the batteries were new. “Silicon has such a high capacity, and with that high capacity, you get more energy out of your battery, except it also undergoes a huge volume expansion as it cycles and self-pulverizes,” said materials science Prof Nancy Sottos.
Past research found that battery anodes made from nanosized silicon particles are less likely to break down, but suffer from other problems as the silicon particles start to break away from the binder. To combat this problem, the researchers further refined the silicon anode by giving it the ability to fix itself on the fly. This self-healing happens through a reversible chemical bond at the interface between the silicon nanoparticles and polymer binder.
“This dynamic re-bonding process essentially holds the silicon particles and polymer binder together, significantly improving the long-term performance of the electrode,” said Sottos.
The researchers tested their new battery against one that does not use the reversible chemical bonding and found that it retains 80 percent of its initial capacity after a typical 400 cycles. These batteries also have a much higher energy density, meaning that they can store more electricity than a graphite-anode battery of the same size.
Future studies will include looking at how this self-healing technology can work with solid-state batteries.
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