New battery concept: potassium instead of lithium

08.10.2015
Potassium instead of lithium: is it a better alternative? (Photo: pitopia)
Potassium instead of lithium: is it a better alternative? (Photo: pitopia)

For decades, it has been regarded as a scientific fact: A potassium-ion battery cannot be built because potassium is incompatible with graphite and other carbon electrodes. New research at the Oregon State University has now refuted this dogma and thrown the door wide open for new electrochemical energy storage systems that will be much cheaper to manufacture than lithium-ion batteries.

The error in the field of chemistry persisted for 83 years. That is, until Xiulei (David) Ji, assistant professor of chemistry at the College of Science at Oregon State University decided to examine the evidence one more time with support from the U.S. Department of Energy. His research group's results have now been published in the Journal of the American Chemical Society (J. Am. Chem. Soc., 2015, 137 (36), pp 11566–11569). An application for a patent on the new technology has already been submitted.

Potassium is almost as good as lithium in batteries, but it is considerably cheaper

What exactly did Ji discover? Graphite is a widely-used, inexpensive material for the production of anodes for batteries. Lithium ions function as carriers and move within the graphite electrode, thus producing an electrical current. But lithium has major drawbacks. Not only is it highly reactive and hard to recycle; it is also extremely rare. The amount present in the earth's crust (by weight) is a mere 0.0017%. This makes the material very expensive.

"The cost problems that exist with lithium are enough to prevent an economy-of-scale effect from boosting profits," Ji said. "In the case of most products, the cost declines when production quantities increase, but with lithium, the exact opposite might happen in the near future. For this reason, we need to find alternatives."

Potassium is 880 times more common than lithium

During their search for low-cost alternatives to lithium, the researchers focused on sodium and potassium. All three of these chemical elements belong to the group of alkaline metals. Potassium is 880 times more common in the earth's crust than lithium, and contrary to popular scientific doctrine, it actually does work in suitable carbon and graphite electrodes. The performance of potassium-ion batteries is still lower than that of lithium-ion batteries.

However, Ji is convinced that further technical developments can narrow down the performance gap. "One can say for certain that the energy density of potassium-ion batteries will never exceed that of lithium-ion batteries. Nevertheless, they are capable of achieving a long life cycle, have high power density, lower cost, and they can also benefit from the advantages of existing manufacturing processes for carbon anodes."

The Oregon State University is now looking for support to continue its research and make the new technology commercially viable.

Volker Buddensiek

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