A New Sodium Metal Fuel Cell Could Help Clean Up Transportation

Arthur T Knackerbracket has processed the following story:

Fuel cells powered with the metal could provide a new source of electric power that's far more energy-dense than lithium-ion batteries.

A new type of fuel cell that runs on sodium metal could one day help clean up sectors where it's difficult to replace fossil fuels, like rail, regional aviation, and short-distance shipping. The device represents a departure from technologies like lithium-based batteries and is more similar conceptually to hydrogen fuel cell systems.

The sodium-air fuel cell was designed by a team led by Yet-Ming Chiang, a professor of materials science and engineering at MIT. It has a higher energy density than lithium-ion batteries and doesn't require the super-cold temperatures or high pressures that hydrogen does, making it potentially more practical for transport. I'm interested in sodium metal as an energy carrier of the future," Chiang says.

The device's design, published today in Joule, is related to the technology behind one of Chiang's companies, Form Energy, which is building iron-air batteries for large energy storage installations like those that could help store wind and solar power on the grid. Form's batteries rely on water, iron, and air.

One technical challenge for metal-air batteries has historically been reversibility. A battery's chemical reactions must be easily reversed so that in one direction they generate electricity, discharging the battery, and in the other electricity goes into the cell and the reverse reactions happen, charging it up.

When a battery's reactions produce a very stable product, it can be difficult to recharge the battery without losing capacity. To get around this problem, the team at Form had discussions about whether their batteries could be refuelable rather than rechargeable, Chiang says. The idea was that rather than reversing the reactions, they could simply run the system in one direction, add more starting material, and repeat.

[...] Chiang and his colleagues set out to build a fuel cell that runs on liquid sodium, which could have a much higher energy density than existing commercial technologies, so it would be small and light enough to be used for things like regional airplanes or short-distance shipping.

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