Researchers say ‘salty’ sodium battery as good as lithium-ion

Battery researchers from Washington State University (WSU) say they have created an “extra salty” sodium-ion battery that could deliver a much cheaper alternative to powering electric cars, smartphones and other electronic devices.

One factor slowing down the switch to clean, electric mobility is the high price of the lithium-ion batteries that power them.

Working out ways to make cheaper batteries that can be discharged and recharged thousands of times is high on the agendas of battery researchers around the world.

By making cheaper batteries, the price of electric vehicles would also drop and subsequently speed up the adoption of zero-emissions transport.

It is expected that electric car pioneer Tesla will reveal how its research team, led by Canadian Dalhousie academic Jeff Dahn, have worked out how to make cheaper battery cells and packs at the upcoming Battery Day, that will likely now be conducted in two events – one online and one with a live audience – in coming months.

It is understood that Tesla has also applied to use cheaper, no-cobalt, lithium iron phosphate batteries made by China’s CATL in its Made-in-China Model 3, the packs for which will reportedly cost 20% less to make than the $US100/kWh needed to bring electric car prices in line with petrol and diesel cars.

But the new research from WSU could, if commercialised, result in ridiculously cheap batteries, because sodium-ion negates the use of expensive materials such as lithium and cobalt, and instead use one of the most abundant materials on the planet.

“This is a major development for sodium-ion batteries,” said Dr. Imre Gyuk, director of Energy Storage for the US Department of Energy’s Office of Electricity who supported the work, according to WSU Insider.

“There is great interest around the potential for replacing Li-ion batteries with Na-ion in many applications.”

While they promise to be much cheaper, sodium-ion batteries have been considered of limited use in the past because they have lower energy density than lithium-ion batteries, and also have trouble being recharged because an inactive layer of sodium builds up on the cathode surface with each recharge, eventually stopping the flow of ions altogether.

“The key challenge is for the battery to have both high energy density and a good cycle life,” WSU Insider quoted Junhua Song, who is lead author on the paper and a WSU PhD graduate who is now at Lawrence Berkeley National Laboratory, as saying.

According to the paper published by the WSU team, this problem has been solved by using extra salt – or rather, sodium ions – in the liquid electrolyte that had improved interaction with the cathode.

The result is a sodium-ion battery that holds as much energy as lithium-ion batteries and can cycle 1,000 times before degrading to 80% its original energy density.

“Our research revealed the essential correlation between cathode structure evolution and surface interaction with the electrolyte,” Lin was quoted as saying.

“These are the best results ever reported for a sodium-ion battery with a layered cathode, showing that this is a viable technology that can be comparable to lithium-ion batteries.”

Next steps for the researchers are, according to WSU Insider, to better understand the improved interaction between the electrolyte and cathode, and work towards excluding the use of cobalt in the battery chemistry.

“This work paves the way toward practical sodium-ion batteries, and the fundamental insights we gained about the cathode-electrolyte interaction shed light on how we might develop future cobalt-free or low cobalt cathode materials in sodium-ion batteries as well as in other types of battery chemistries,” Song was quoted as saying.

“If we can find viable alternatives to both lithium and cobalt, the sodium-ion battery could truly be competitive with lithium-ion batteries.

“And, that would be a game-changer,” he added.

Citation: https://doi.org/10.1021/acsenergylett.0c00700

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