Fluorine May Replace Lithium For Rechargeable Batteries

on December 28, 2020

With increased use of rechargeable batteries to power modern technology, particularly electric vehicles, researchers have been looking for alternative materials for lithium-ion in rechargeable batteries. Modern batteries use lithium and cobalt, but these have a very limited supply.

Interestingly, the fluoride ion is the mirror opposite of the lithium ion, having the strongest attraction for electrons, which allows it to easily carry out electrochemical reactions.

Researchers in Japan are also testing fluoride-ion batteries as possible replacements for lithium-ion batteries in vehicles. They say these batteries could allow electric vehicles to run 1,000 kilometers (621 miles) on a single charge. However, current fluoride-ion batteries have poor cyclability, which means they tend to degrade rapidly with charge-discharge cycles.

In their new work, the researchers adopted a different approach to fluoride-ion battery design, identifying two materials that easily gain or lose fluoride ions while undergoing small structural changes to enable good cyclability.

The new battery materials are both layered electrides, says Rohan Mishra, assistant professor of mechanical engineering and materials science at Washington University in St. Louis.

Electrides are a relatively new class of materials that researchers have known about in principle for about 50 years, but it wasn’t until the past 10 to 15 years that their properties were better understood, Mishra says.

While these materials conduct electrons like ordinary metals, unlike the “sea of electrons” in metals where the electrons are delocalized throughout the crystal, in electrides, the electrons reside at specific interstitial sites within the crystal structure, similar to an ion.

“We predict that these interstitial electrons can be easily replaced with fluoride ions without significant deformations to the crystal structure, thus enabling cyclability,” Mishra says. “The fluoride ions can also move or diffuse fairly easily due to the relatively open structure of the layered electrides.”

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Fractal Energy Storage ConsultantsFluorine May Replace Lithium For Rechargeable Batteries