While electric vehicles have become part of daily life, there is still no news of electric airplanes being commercialized. The aviation industry continues to rely on fossil fuels, accounting for about 3% of global greenhouse gas emissions. If electric airplanes come to market, it would help achieve carbon neutrality.
American scientists have developed a new power source that could accelerate the arrival of the electric airplane era. The lithium-ion batteries used in electric vehicles have limitations in capacity for use in aircraft. While cars simply stop when their batteries run out, aircraft could lead to crash accidents. This new power source is expected to resolve such issues, offering significantly larger capacity than existing batteries.
A research team led by Yet-Ming Chiang, a professor of materials science at the Massachusetts Institute of Technology (MIT), announced on the 27th (local time) in the international journal Joule that they have developed a new fuel cell that can store more than three times the energy per weight than existing lithium-ion batteries. It is a fuel cell capable of supplying power to cargo trucks, ships, and airplanes.
A fuel cell is a device that converts the chemical energy of fuel directly into electrical energy through electrochemical reactions. While it operates on the same principle as a battery, the difference lies in that the fuel for the chemical reaction is injected from outside. Lithium-ion batteries contain lithium as the fuel inside. When the power runs out, lithium batteries are charged, whereas fuel cells are replenished with fuel.
The fuel cells developed by the MIT research team use liquid sodium as fuel. Sodium can primarily be obtained from salt and is cheaper and more readily available worldwide than lithium used in electric vehicle batteries. Large-scale production of sodium is also feasible. The researchers noted that in the past, sodium was produced in the U.S. at a scale of 200,000 tons per year for manufacturing lead octane additives.
The research team has developed a fuel cell in the form of a sealed cartridge filled with liquid sodium. Once the fuel is depleted, the cartridge can be refilled. The other electrode of the fuel cell allows air in to supply oxygen. Sodium ions move between the electrodes, reacting chemically with oxygen to generate electric current.
Experimental results show that sodium fuel cells can store more than three times the energy per weight compared to existing lithium-ion batteries. Professor Chiang explained, "The critical threshold for electric flight is about 1,000 watt-hours (Wh) per kilogram, but current lithium-ion batteries for electric vehicles only reach 300 watt-hours, which is far from adequate. We confirmed that the newly developed fuel cell can exceed 1,000 watt-hours in testing."
While some corporations are challenging the electric airplane sector, there are companies actively pursuing this goal. Heart Aerospace, invested by Bill Gates, is developing a 19-passenger aircraft that operates purely on electricity. Currently, they are working on a hybrid approach that combines existing engines with lithium batteries for a 30-passenger aircraft. The American startup Wright Electric is developing electric motors for aircraft. To commercialize electric airplanes, it is essential to replace the engine with a motor.
Although several corporations are involved, electric airplanes remain a challenging goal to achieve. MIT Technology Review, a U.S. technology media outlet, pointed out that "current battery technology can only provide power to the lightest aircraft due to energy density, and the issue is how much energy can be stored in the limited space within the aircraft."
The MIT research team has also planned to commercialize fuel cell technology. They have already established a startup named Propel Aero. This company is currently based in the MIT startup incubator.
The research team plans to create a prototype of a 1,000 watt-hour fuel cell capable of powering large drones (unmanned aircraft) within a year. They stated that following this, they intend to validate the concept using fuel cells for electric airplanes for practical purposes.
References
Joule (2025), DOI: https://doi.org/10.1016/j.joule.2025.101962