Lithium-ion batteries, which have been driving electric mobility for years, are beginning to show limitations. This is especially true in sectors such as aviation, maritime, and rail transport, where weight is a determining factor.
A team of researchers from the Massachusetts Institute of Technology (MIT) has developed an innovative fuel cell based on liquid sodium metal. This development could transform these sectors by offering high energy efficiency and fast recharging.
How the sodium-air cell works
Unlike traditional batteries, which require electrical recharging, this cell operates with liquid sodium metal as fuel and common air as a source of oxygen.
In between, a solid ceramic membrane allows the passage of sodium ions, while a porous air-oriented electrode generates the chemical reaction that produces electricity.
Tripling energy efficiency and electric mobility
During laboratory tests, the prototype achieved an energy density of over 1,500 Wh/kg. This translates to over 1,000 Wh/kg in complete systems, tripling the capacity of current electric vehicle batteries (300 Wh/kg).
According to Professor Yet-Ming Chiang, reaching 1,000 Wh/kg could make regional electric aviation viable, representing 80% of domestic flights and 30% of sector emissions.
Security and sustainability benefits
- Increased safety: The physical separation of the most dangerous reagents prevents uncontrolled reactions, reducing risks compared to compact batteries.
- Zero CO₂ emissions: The sodium hydroxide generated in the chemical reaction captures atmospheric CO₂, turning it into sodium bicarbonate, which can help reduce marine acidification.
Reuse and scalability
The cell operates with rechargeable cartridges, where the molten sodium (which melts at 98°C) is replenished after use.
Sodium is cheap and abundant, extracted from common salt, and has been mass-produced before, with records of 200,000 tons per year in the U.S. alone.
Prototypes and next steps
The team has developed two prototypes:
- H-type vertical model.
- Tray-type horizontal design, with ceramic membrane and humid air, ensuring cleaner and more efficient reactions.
They plan to launch a functional brick-sized prototype with a capacity of 1,000 Wh, enough to power a large agricultural drone.
The development is being carried out under the startup Propel Aero, incubated at MIT, with a view to commercializing and expanding this technology.
