MIT engineers have created a new battery design using rock salt, sulfur, and aluminum. It’s cheap, resistant to fires, and charges quickly, making it potentially useful for powering buildings or electric cars.
Lithium-ion batteries have dominated the market for the last few decades due to their dependability and high power density. However, lithium has become increasingly expensive and scarcer. Lithium cells can also be dangerous; if broken or misused, they might explode or catch fire because they contain a flammable electrolyte.
Lithium prices have increased by about 500 percent in the past year. Other minerals needed for making Li-ion batteries have also risen in cost, and experts predict that the price of these cells will likely continue to increase. Less costly and safer alternatives are required, particularly as the globe moves toward electric vehicles and renewable energy.
With this in mind, the MIT team created a new kind of rechargeable battery using widely available, affordable materials. After extensively studying the periodic table and experimenting, they finally decided to use aluminum and sulfur as their two electrode materials, together with a molten chloro-aluminate salt electrolyte. Aside from being cheap and common, these ingredients are non-flammable, so there is no danger of a fire or explosion. Donald Sadoway, the study’s lead author, spoke of the electrolyte: “We were not going to use the volatile, flammable organic liquids.”
The scientists conducted tests to demonstrate that the new battery cells can sustain hundreds of cycles at rapid charging rates. For example, some experiments revealed that the aluminum-sulfur battery charged in less than a minute! On top of that, the cost of the cells would be only one-sixth that of a comparable-sized lithium-ion cell.
Sadoway said, “I wanted to invent something that was better, better than lithium-ion batteries for small-scale stationary storage, and eventually for automotive.”
They can operate at scorching temperatures as high as 392°F (200°C). Interestingly, they perform better in higher temperatures; for example, the batteries charged 25 times quicker at 230°F (110°C) than they did at 77°F (25°C). However, the researchers claim that the battery doesn’t require additional energy or special insulation to achieve this high operating temperature. Its regular charging and discharging cycle is sufficient to maintain that elevated temperature.
The researchers chose the molten-salt electrolyte due to its low melting point. Still, it also has another advantage: it naturally prevents the formation of dendrites. Batteries, especially Li-ion cells, face a significant challenge from the tiny metal “tendrils” because they slowly grow between the two electrodes, which decreases the cells’ performance over time and increases the risk of short circuits.
“We did experiments at very high charging rates, charging in less than a minute, and we never lost cells due to dendrite shorting,” Sadoway said.
According to the research team, a few dozen kilowatt-hours, or the amount needed to power a single home with electricity, would be the scale for this battery design. Additionally, they may be beneficial as electric vehicle charging stations due to their quick charging and discharging. They would allow electric cars to be charged without having to install expensive new power lines and could be used in external backup power banks.
Different battery technologies might perform better at grid-scale, such as a recent design using aluminum, molten salt electrolyte, and nickel electrodes.
A spinoff company called Avanti, co-founded by Donald Sadoway, has been granted a license to use the aluminum-sulfur battery patents. The next step will be to build it at scale and put it through stress tests. The research was published in an article titled Fast-charging aluminium–chalcogen batteries resistant to dendritic shorting on August 24, 2022, in the journal Nature.
