Electric planes, trains, and ships may soon become a reality thanks to a new type of energy system developed by researchers at MIT and other institutions.
Instead of using traditional batteries, the team created a prototype sodium-air fuel cell—a device that stores much more energy than today’s lithium-ion batteries and could be the key to electrifying heavy transportation systems.
Unlike batteries, which need to be recharged, fuel cells can be quickly refueled.
This makes them ideal for vehicles that need to travel long distances without stopping for hours to recharge.
In this new design, the fuel is liquid sodium metal—a cheap, abundant material—and the oxidizer is plain air.
A solid ceramic layer in the middle allows sodium ions to pass through, while a special electrode reacts with oxygen from the air to produce electricity.
The team’s prototype showed that the cell could store over three times the energy per kilogram compared to current lithium-ion batteries. That kind of performance is crucial for electric aviation, where every bit of weight counts.
Current batteries don’t store enough energy to power most flights, especially longer ones. But this new sodium-air cell could reach the energy density needed for short to medium-range flights, which make up the majority of domestic air travel.
One reason this system works so well is that it avoids the technical roadblocks that have plagued previous sodium- or lithium-air battery efforts.
These older designs were hard to recharge and suffered from buildup of solid waste products inside the battery.
Instead, the new device works as a fuel cell, where energy-carrying materials can be added and removed during operation. That sidesteps the recharging issue altogether.
The researchers built two types of small prototype cells, both of which used controlled humidity in the air to improve efficiency. When air with just the right amount of moisture flows into the cell, it helps turn the waste product—sodium oxide—into a liquid form that is easier to manage and doesn’t clog up the system.
As the fuel cell runs, it creates sodium oxide, which eventually turns into sodium bicarbonate—yes, baking soda—when it reacts with moisture and carbon dioxide from the air. This byproduct not only avoids greenhouse gas emissions but could also help reduce ocean acidification if it ends up in seawater. In other words, the plane’s exhaust could actually help the environment.
There’s also a safety advantage. While sodium metal is reactive and must be handled carefully, the fuel cell keeps the reactants separated, lowering the risk of explosive reactions. That makes it a safer option for high-energy applications.
The team now plans to develop a larger version of the fuel cell, roughly the size of a brick, to power large drones. They hope to demonstrate this within a year through their new startup, Propel Aero. Because sodium is abundant and comes from common salt, scaling up the technology should be possible and much cheaper than today’s battery systems.
This breakthrough could mark the beginning of a new era for electric transportation—one where planes don’t just fly cleaner, but might even clean the air as they go.
