Cambridge, MA, June 2, 2025 – Researchers at the Massachusetts Institute of Technology (MIT) have developed a groundbreaking sodium-air fuel cell that could revolutionize electric aviation. This innovative technology achieves energy densities exceeding 1,500 watt-hours per kilogram (Wh/kg) in laboratory settings, surpassing the critical 1,000 Wh/kg threshold deemed necessary for viable electric regional aircraft.
A Leap Forward in Energy Density
Traditional lithium-ion batteries, commonly used in electric vehicles, offer energy densities around 250–300 Wh/kg, which is insufficient for most aviation applications. The new sodium-air fuel cell developed by MIT researchers delivers over five times that energy density, marking a significant advancement in the field.
The fuel cell operates by combining liquid sodium with oxygen from the air, generating electricity through an electrochemical reaction. Unlike conventional batteries that require recharging, this system can be refueled by replacing the consumed sodium, offering a more practical solution for aviation needs.
Environmental Benefits
Beyond its impressive energy performance, the sodium-air fuel cell offers environmental advantages. The byproduct of the electrochemical reaction is sodium hydroxide, which naturally captures carbon dioxide (CO₂) from the atmosphere, forming sodium bicarbonate. This process not only reduces greenhouse gas levels but also has the potential to mitigate ocean acidification.
Professor Yet-Ming Chiang, a senior author of the study, highlighted the dual benefits: “There’s this natural cascade of reactions that happens when you start with sodium metal. It’s all spontaneous. We don’t have to do anything to make it happen—we just have to fly the airplane.”
From Prototype to Practical Application
The MIT team has constructed two laboratory-scale prototypes of the sodium-air fuel cell. To advance the technology towards commercial use, they have established a startup company, Propel Aero, aiming to develop a brick-sized fuel cell capable of powering large drones. This initial application serves as a stepping stone towards integrating the technology into regional electric aircraft.
Sodium, the primary fuel for the cell, is abundant and inexpensive, derived from common salt. Its availability and cost-effectiveness make it an attractive alternative to lithium, which is more expensive and less environmentally friendly to extract.
The prototypes are small but powerful, achieving performance benchmarks previously thought unattainable with metal-air technology. Propel Aero’s initial focus will be on drone applications, which require high power in a compact form factor, ideal for proving the technology in real-world scenarios before scaling up to larger aircraft.
Implications for the Aviation Industry
Achieving an energy density of 1,000 Wh/kg is considered a pivotal milestone for electric aviation, particularly for regional flights that constitute a significant portion of domestic air travel and associated emissions. The sodium-air fuel cell’s performance not only meets but exceeds this benchmark, positioning it as a viable solution for sustainable aviation.
The development arrives amid growing pressure on the aviation sector to decarbonize. Airlines and manufacturers are investing in hybrid and fully electric solutions to comply with international climate goals and public demand for greener travel options. MIT’s innovation could provide the missing piece that enables longer, zero-emission flights.
While challenges remain in scaling the technology and ensuring safety—given sodium’s reactivity—the research marks a significant step towards cleaner, more efficient air travel. The successful development and implementation of this fuel cell could pave the way for zero-emission flights, contributing to global efforts to combat climate change.
Moreover, the versatility of sodium-air cells could inspire new designs in aviation, including vertical takeoff and landing (VTOL) aircraft and urban air mobility solutions. These applications demand lightweight, high-energy systems that traditional batteries cannot support. With continued development, sodium-air technology could redefine the parameters of electric aviation.
The MIT team envisions a future where electric planes powered by sodium-air fuel cells can travel regional distances without emitting carbon, reducing the industry’s environmental impact significantly. This leap forward demonstrates the potential for science and engineering to solve some of the most pressing challenges of our time.
By Jasmine Clarke, Senior Correspondent