U.S. Researchers Open Door To Plastics Replacing Hot Lithium In Batteries

Lithium has long been the material of choice for high-performance, long-lasting batteries. It’s the lightest known metal and can hold the most electricity. The downside, as any laptop user knows, is that they can overheat, even to the point of bursting into flames.

For decades, researchers have scoured materials in a search for battery terminals that work as well as lithium but don’t overheat. One obvious choice was plastics, or polymers, but it wasn’t until now that a research team – from Northwestern University’s McCormick School of engineering – has reported that it has combined two theories on plastics to demonstrate how an ion charge shifts the plastic’s structure.

Monica Olvera de la Cruz, a professor of materials science and engineering at McCormick, said her team focused on plastics called block copolymers, or BCPs, a fusion of two kinds of polymers. BCPs are already used to conduct ions because they self-assemble into microscopically small forms known as nanostructures that can transport ions while maintaining the structures’ integrity.

While the ions moving through BCPs don’t affect this integrity, they do affect the shapes of the channels within the nanostructures. The next challenge, de la Cruz explains, is to learn how to control the shape shifting of the nanochannels to improve how ion charges move through them.

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The researchers gained this understanding by combining two traditional theories of polymers. One is known as the self-consistent field theory, which describes how long molecules behave. The other is the liquid state theory, which describes how charges operate on the atomic level.

By combining these two theories for the first time, they learned that inside these nanochannels are both ions and oppositely charged molecules called counter-ions. These two particles automatically combine to create a kind of salt that exerts a force on the nanochannels, changing their structure.

As a result, Olvera de la Cruz explains, further study can lead to predict and therefore even design these nanochannels into what she calls an efficient “highway system” for ions that can make batteries more powerful and efficient.

By Andy Tully of Oilprice.com