Potassium batteries have been a twinkle in the eye of energy storage researchers for long enough, and now they are starting to emerge out of the lab and into the sunlight. In the latest development on that score, the startup Group1 has just announced itself as the “world’s first company to commercialize cathode materials for novel Potassium-ion batteries.”
What’s The Big Deal About Potassium Batteries?
Potassium batteries for EVs and other applications have sailed across the CleanTechnica radar here and there, one recent example being a cellulose-enabled version developed at the University of Bristol.
Potassium is a tricky thing, though. Back in 2020 our friends over at IEEE Spectrum took a close look at the application of potassium batteries to grid-scale energy storage and rendered this observation:
“People have historically shied away from potassium because the metal is highly reactive and dangerous to handle. What’s more, finding electrode materials to hold the much heftier potassium ions is difficult.”
On the other hand, considering the supply chain issues bedeviling the lithium-ion energy storage field, something’s got to give.
“Some battery researchers are taking a fresh look at lithium’s long-ignored cousin, potassium, for grid storage,” explained reporter Prachi Patel. “Potassium is abundant, inexpensive, and could in theory enable a higher-power battery.”
“However, efforts have lagged behind research on lithium and sodium batteries,” Patel noted. “Yet a flurry of reports in the past five years detail promising candidates for the cathode. Among the leaders are iron-based compounds with a crystalline structure similar to Prussian blue particles, which have wide open spaces for potassium ions to fill.”
If Prussian blue rings a bell, you may be thinking of sodium-ion research spinning out from the lab of legendary energy storage innovator John Goodenough of the University of Texas at Austin, who just celebrated his 100th birthday last year.
“A group from the University of Texas at Austin led coinventor of the lithium-ion battery and a winner of the 2019 Nobel Prize in Chemistry, has reported Prussian blue cathodes with an exceptionally high energy density of 510 watt-hours per kilogram, comparable to that of today’s lithium batteries,” Patel noted in his 2020 piece.
Here Comes Potassium Batteries From Group1
The report cited by Patel is a study published in the Journal of the American Chemistry Society back in January of 2017, the authors of which are listed as Leigang Xue, Yutao Li, Hongcai Gao, Weidong Zhou, Xujie Lü, Watchareeya Kaveevivitchai, Arumugam Manthiram, and John B. Goodenough.
That brings us to the newly announced Group1 news. Listed among the startup’s leadership are battery innovator Alexander Girau, Chief Science Officer Dr. Yakov Kutsovsky (formerly of Cabot Corporation), and Dr. Leigang Xue.
An embargoed press release describes Dr. Leigang Xue as the “inventor of KPW [Potassium Prussion White] cathode materials in 2017 at Professor Goodenough’s laboratory at University of Texas at Austin,” so it’s a good guess this is the same person.
“Unlike LIBs [lithium-ion batteries], raw materials used by Group1 to create KIBs [potassium-ion batteries] are sustainable, in that they are widely available both in the United States and internationally,” Group1 explains. “The potassium used in Group1’s KPW cathode materials is 1,000 times more abundant in the earth than lithium, as well as 20 times more affordable.”
“KIBs produced with Group1’s KPW cathode materials will deliver safety benefits over LIBs based on the use of safer electrolytes and oxygen-free materials,” they add. “Further, KIBs are more efficient and faster charging than LIBs, as potassium ions in electrolytes have a smaller size and higher mobility when compared to lithium ions.”
What Is This Potassium Prussian White Of Which You Speak?
Circling back around to that thing about Prussian Blue, that’s the connection between sodium and potassium batteries. A recent study published in the American Chemistry Society’s Applied Energy Materials journal provides this explainer (break added):
“Prussian blue (PB) and its analogues are promising materials for sodium-ion battery cathodes because of their high working potentials, high theoretical capacity, and low toxicity.
“Prussian white (PW), which is the fully reduced and sodiated form of PB, could significantly improve the manufacturability of commercial batteries as it circumvents the requirement of a reactive sodium-loaded anode in cell assembly.”
For an explainer on the potassium version of Prussian White, we turn to another ACS publication, ACS Energy Letters.
A 2017 study published in Energy Letters refers to “nonaqueous potassium-ion batteries” as “possible low-cost alternatives to Li-ion batteries for large-scale energy storage, owing to their ability to use graphitic carbon as the negative electrode.”
“Positive electrode materials remain a challenge,” the authors explain, and that’s where potassium comes in.
“Here, we report control of the crystal dimensions of the Prussian white hexacyanoferrate (HCF), K1.7Fe[Fe(CN)6]0.9, using solution chemistry to obtain either nano, submicron, or micron crystallites. We observe a very strong effect of crystallite size on electrochemical behavior,” they note.
Potassium Batteries For Electric Vehicles?
Yes, what about them? Potassium batteries for electric vehicles are not the same thing as grid scale energy storage. We’ll know more about Group1’s intentions once they get the ball rolling, so stay tuned for more on that.
Meanwhile, back in 2020 researchers over at Columbia Engineering took a look at potassium batteries from the electric vehicle angle, that being a solution to the dendrite problem.
Dendrites are feathery structures that form in lithium-ion batteries and interfere with performance. There are a variety of workarounds, and Columbia Engineering zeroed in on potassium as one of them.
“Researchers at Columbia Engineering report today that they have found that alkali metal additives, such as potassium ions, can prevent lithium microstructure proliferation during battery use,” the school reported. “They used a combination of microscopy, nuclear magnetic resonance (similar to an MRI), and computational modeling to discover that adding small amounts of potassium salt to a conventional lithium battery electrolyte produces unique chemistry at the lithium/electrolyte interface.”