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MIT Team Releases Tempting Report On Electric Aircraft Technology

New tech could triple the energy density of current lithium-ion batteries.

Mark Phelps

·Wednesday, May 28, 2025

 

Credit: Massachusetts Institute of Technology

The Massachusetts Institute of Technology (MIT) announced research results today into a new fuel cell technology that could triple the energy density of electric vehicles. The report singled out aviation as a likely beneficiary of the advanced tech, since weight savings are a key component in electric aircraft propulsion systems.

The new technology is described as similar to a battery, but with the difference that it can be “refueled rather than recharged.” Rather than fossil fuel or hydrogen, these fuel cells are powered by inexpensive and widely available liquid sodium metal. The reactive side of the fuel cell is simply air. In between is a layer of solid ceramic material that fills the role of electrolyte, “allowing sodium ions to pass freely through” along with a porous air-facing electrode that helps the sodium to react to the oxygen in the air and produce electricity. Compared with lithium-ion battery technology, which has seemed to plateau in development, the new fuel-cell based concept could triple lithium-ion’s energy density.

The team’s findings were published today in Joule, an MIT journal. With refreshing candor, team member Yet-Ming Chiang (Material Science and Engineering professor) said, “We expect people to think that this is a totally crazy idea. If they didn’t, I’d be a bit disappointed because if people don’t think something is totally crazy at first, it probably isn’t going to be that revolutionary.”

Aviation’s weight sensitivity is clearly on the MIT team’s radar. Chiang noted, “The threshold that you really need for realistic electric aviation is about 1,000 watt-hours per kilogram.” That contrasts with lithium-ion batteries’ current top end of approximately 300 watt-hours per kilogram.

Chiang acknowledged that even 1,000 watt hours would not be sufficient for practical transcontinental or transatlantic air travel. But he asserted that the 1,000 watt-hour threshold would be practical for regional electric aviation, “which accounts for about 80% of domestic flights and 30% of the emissions from aviation.”

Another important advantage for the sodium-metal technology is safety. Noting the fire danger in high-energy-density battery systems due to the reactive chemicals being so close to each other, Chiang pointed out that with this system, one side of the battery would be just air. He noted that the air is “dilute and limited,” adding that the new technology would not have two concentrated reactants right next to each other. “If you’re pushing for really, really high energy density,” he said, “you’d rather have a fuel cell than a battery for safety reasons.”