Scientists uncover new way to improve performance of next-gen lithium-oxygen batteries

UIC scientists demonstrate at nanometer level that lithium peroxide build up slows battery chemical reactions

Researchers at the University of Illinois have discovered a new way to improve the performance of next-gen lithium-oxygen batteries.

Potentially offering up to five times more energy than the lithium-ion batteries that power electric vehicles and cell phones of today, the lithium-oxygen variety has been in development for some time due to their potential high energy density.

However, what has stopped them getting to market is that they tend to slow down and die after just a few charge and discharge cycles.

But using a new microscopy technique that can visualise chemical reactions occurring in liquid environments, the researchers found why the lithium-oxygen batteries aren't surviving charges.

Reporting their findings in the science journal Nano Energy, the scientists demonstrated at the nanometer level that a chemical called lithium peroxide forms in the battery's liquid electrolyte component, slowing chemical reactions.

The coated electrodes can then no longer function efficiently and chemical reactions that produce energy ultimately stop.

"What we were able to see for the first time is that lithium peroxide develops in the liquid electrolyte of lithium-oxygen batteries, and is a contributor to the slow down and ultimate death of these batteries," said Reza Shahbazian-Yassar, lead author of the paper.

"This is a newly discovered reason why these promising batteries have such a steep drop off in efficiency and yield after relatively few charge [and] discharge cycles."

Because of the finding, the researchers said they can now start to come up with ideas and designs that either prevent this from happening or do something to maintain the proper functioning of the electrolyte so it doesn't interfere with the battery's operation.

"We can use the new liquid microscopy technique to see if we are moving in the right direction," Yassar explained.

Nevertheless, he admitted that despite the discovery, mass-produced lithium-oxygen batteries for public or commercial use are still a long way off.

"There are many problems that need to be overcome with lithium-air batteries before they can get into mainstream use, but knowing exactly what the issues are is a big first step towards the commercialisation of these extremely high energy density batteries," he added.