Researchers at the Massachusetts Institute of Technology (MIT) have unveiled a sodium fuel cell technology that offers three times the energy density of current lithium-ion batteries, potentially transforming electric aviation and other transport industries. The research team has also launched a startup, Propel Aero, to advance commercial development.
Unlike conventional batteries, the sodium fuel cell uses liquid sodium, sourced from abundant materials such as sea salt, as a fuel, which is replenished at about 98 degrees Celsiusâthe boiling point of waterârather than recharged electrically. The system operates by chemically reacting sodium with oxygen from the air, separated by a solid ceramic electrolyte that allows sodium ions to pass through and generate electricity.
Professor Yet-Ming Chiang, a lead researcher in materials science and engineering at MIT, highlighted the significance of the innovation for aviation, where weight constraints have limited electric aircraft development. âThe threshold that you really need for realistic electric aviation is about 1,000 watt-hours per kilogram,â Chiang said. âTodayâs electric vehicle lithium-ion batteries top out at about 300 watt-hours per kilogram â nowhere near whatâs needed. Even at 1,000 watt-hours per kilogram, that wouldnât be enough to enable transcontinental or trans-Atlantic flights.â
The fuel cellâs energy density is comparable to hydrogen fuel cell technology, which is mostly practical for regional flights, a segment accounting for roughly 80% of domestic flights and 30% of aviation emissions, according to MIT. The researchers also see potential applications in trucking, marine, and rail transportâsectors that require high energy density and cost efficiency.
An important technical advancement reported by the team is the role of humidity in the air, which facilitates efficient electrochemical reactions and results in liquid rather than solid discharge products, improving performance. Doctoral researcher Karen Sugano explained, âThe key was that we can form this liquid discharge product and remove it easily, as opposed to the solid discharge that would form in dry conditions.â
The sodium fuel cell emits sodium oxide, which reacts naturally with atmospheric moisture and carbon dioxide to form sodium bicarbonate, commonly known as baking soda. MIT suggests this could potentially aid in ocean deacidification. âThereâs this natural cascade of reactions that happens when you start with sodium metal,â Chiang said. âItâs all spontaneous. We donât have to do anything to make it happen, we just have to fly the airplane.â
The researchers plan to build a prototype fuel cell roughly the size of a brick that can deliver around 1,000 watt-hours of energy, suitable for powering large drones, with a demonstration expected within a year. Propel Aero, currently housed in MITâs startup incubator The Engine, is working on scaling the technology to commercial sizes.
The breakthrough presents a promising alternative to lithium-ion batteries, leveraging sodiumâs abundance and lower cost to support future decarbonization efforts in aviation and beyond.
Source: news.mit.edu