Inner workings of a battery revealed

Researchers using an electron microscope have seen the inner workings of a battery electrode while it is bathed in wet electrolytes, mimicking real-world conditions.

Previously researchers studied batteries under dry conditions, which is easier and cheaper to do. Until now they haven't been able to study the hard-to-find solid electrolyte interphase layer, a coating that appears on the electrode and affects the performance of the battery.

"The liquid cell gave us global information about how the electrodes behave in a battery environment," said materials scientist Chongmin Wang of the Department of Energy's Pacific Northwest National Laboratory. "And it will help us find the solid electrolyte layer. It has been hard to directly visualize in sufficient detail."

The research published in the journal Nano Letters.

Wang and her colleagues used the microscopes to see this flow of electrons and positive ions as it happens in wet conditions. They found that when the positive ions move to the negative electrode it swells up, which is a known phenomenon.

But they found the swelling to be similar to when the same is simulated in dry conditions, thereby proving that testing a battery under dry conditions is similar to testing it under wet conditions.

"We have been studying battery materials with the dry, open cell for the last five years," said Wang. "We are glad to discover that the open cell provides accurate information with respect to how electrodes behave chemically. It is much easier to do, so we will continue to use them."

But they weren't able to see this elusive layer on the electrodes and Wand said that they were trying to halve the thickness of the electrolyte used in order to capture and see this layer.

[Northwest National Laboratory] [Nano Letters]