Designing Ion ‘Highway Systems’ for Batteries

  • Since the early 1970s, lithium has been the most popular element for batteries, though it is highly flammable.
  • Researchers have married two traditional theories, opening the door for a new class of batteries.
  • Combining the Self-Consistent Field Theory and Liquid State Theory provides a new way of exploring nano-channel systems.

Since the early 1970s, lithium has been the most popular element for batteries: it’s the lightest of all metals and has the greatest electrochemical potential. 

But a lithium-based battery has a major disadvantage: it’s highly flammable, and when it overheats, it can burst into flames. For years, scientists have searched for safer battery materials that still have the same advantages as lithium. While plastics (or polymers) seemed like an obvious choice, researchers never fully understood how the material would change when an ion charge was introduced. 

Now a McCormick team has married two traditional theories in materials science that can explain how the charge dictates the structure of the material. This opens the door for many applications, including a new class of batteries.

 “There is a huge effort to go beyond lithium in a flammable solvent,” says Monica Olvera de la Cruz, materials science and engineering, and senior author of the paper. “People have been looking at alternatives that are not explosive, like plastics. But they didn’t know how to compute what happens when you put in a charge.”

The team looked at plastics known as block copolymers (BCPs) that are two types of polymers stuck together. They are a leading material for use as ion conductors because they self-assemble into nanostructures that both enable ion charge transport and maintain structural integrity. BCPs innately have nano-channels through which the ion can travel, but the charges themselves manipulate the shape of the channels. To use the material in batteries, researchers must find a way to control the shape of the nano-channels, so that the charge moves well.

“If you can optimize the ability of the charge to move through the system, then you can optimize the power that actually comes out of the battery,” says Charles Sing, a postdoctoral fellow in Olvera de la Cruz’s lab and first author of the paper.

The team hopes their finding will guide experimentalists as they test materials. It will give researchers more information about the physical concepts underlying BCP systems.

McCormick School of Engineering
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