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New battery discovery overturns decades of false assumptions

07 October 2015

New findings at Oregon State University (OSU) have overturned a scientific dogma by showing that potassium can work with graphite in a potassium-ion battery.

Graphic outlining the electrical capacity of a newly developed potassium-ion battery (courtesy of Oregon State University)

The last time this possibility was explored was when Herbert Hoover was president. "For decades, people have assumed that potassium couldn't work with graphite or other bulk carbon anodes in a battery," says OSU's Xiulei Ji. "That assumption is incorrect."

The findings are of considerable importance, researchers claim, because they open some new alternatives to batteries that can work with well-established and inexpensive graphite as the anode. Lithium can do that, as the charge carrier whose ions migrate into the graphite and create an electrical current.

Aside from its ability to work well with a carbon anode, however, lithium is quite rare, found in only 0.0017 percent, by weight, of the Earth's crust. Because of that it's comparatively expensive, and it's difficult to recycle. Researchers have yet to duplicate its performance with less costly and more readily available materials, such as sodium, magnesium, or potassium.

"The cost-related problems with lithium are sufficient that you won't really gain much with economies of scale," Ji says. "With most products, as you make more of them, the cost goes down. With lithium the reverse may be true in the near future. So we have to find alternatives."

That alternative may be potassium, which is 880 times more abundant in the Earth's crust than lithium. The new findings show that it can work effectively with graphite or soft carbon in the anode of an electrochemical battery. At the moment, batteries based on this approach don't have performance that equals those of lithium-ion batteries, but Ji believes improvements in technology should narrow the gap.

"It's safe to say that the energy density of a potassium-ion battery may never exceed that of lithium-ion batteries," he says. "But they may provide a long cycling life, a high power density, a lot lower cost, and be ready to take the advantage of the existing manufacturing processes of carbon anode materials."


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