MIT Group May Have Solved The Liquid Sodium Battery Conundrum

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If battery researchers were rock stars, Donald Sadoway of MIT would be Mick Jagger (or John Mayer if you are a Millennial). Sadoway has been toiling away, trying to find next generation batteries that are cheap to build, long lasting, and don’t burst into flames under stressful situations. Now he thinks he and his team may be near the end of their long quest.

liquid sodium battery MIT
Credit: Illustration modified from an original image by Felice Frankel. Via Science Daily

A battery that uses a liquid sodium electrode was first proposed in 1968. While revolutionary in theory, in practice it required a specialized membrane manufactured from ultra thin ceramic material to keep the components of the battery separated. Not only was the ceramic membrane expensive to manufacture, it was also exceedingly brittle, making it impractical for real world use. Researchers from General Electric spent a decade trying to solve the sodium battery’s weaknesses but eventually gave up in frustration.

As so happens in scientific research, the answer was discovered quite by accident. In a paper published on January 22 by the journal Nature Energy, Sadoway and his team report they found a way to replace the delicate ceramic membrane with one made of far more ordinary metal mesh.

While experimenting with various molten metal-based batteries, Sadoway says his team was surprised by the results they got from one test using lead compounds. “We opened the cell and found droplets” inside the test chamber, which “would have to have been droplets of molten lead,” he says. But instead of acting as a membrane, as expected, the compound material “was acting as an electrode,” actively taking part in the battery’s electrochemical reaction.

“That really opened our eyes to a completely different technology,” Sadoway says. The membrane had performed its role — selectively allowing certain molecules to pass through while blocking others — in an entirely different way, using its electrical properties rather than the typical mechanical sorting based on the sizes of pores in the material, according to a report in Science Daily.

That’s when the researchers began experimenting with a membrane made from ordinary steel mesh coated with a solution of titanium nitride and found it could do everything the ceramic membrane did without the brittleness and fragility. “I consider this a breakthrough,” Sadoway says. For the first time in 50 years, the theoretical advantages of a liquid sodium battery — cheap, abundant materials, safe operation, and the ability to cope with many charge/discharge cycles without degrading — could be translated into a commercially viable product.

Sadoway says the new steel mesh membrane could work with a wide variety of molten electrode battery chemistries, which could make many new battery designs possible. The new technology is too heavy and bulky for use in electric vehicles or laptop computers, but it would be ideal for grid scale battery storage. And that could overcome the argument Energy Secretary Rick Perry likes to makes that we need more coal and nuclear generating facilities because renewables are not reliable sources of baseload electricity. That would certainly qualify as a breakthrough, indeed.


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Steve Hanley

Steve writes about the interface between technology and sustainability from his home in Florida or anywhere else The Force may lead him. He is proud to be "woke" and doesn't really give a damn why the glass broke. He believes passionately in what Socrates said 3000 years ago: "The secret to change is to focus all of your energy not on fighting the old but on building the new."

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