A new battery made of abundant and inexpensive materials could solve a big problem for renewable energy, its creators have said.

Developed by researchers at the Massachusetts Institute of Technology (MIT) and others, the low-cost battery could store electricity for when renewable sources have stopped generating – when the wind is no longer blowing, for example.

Made of aluminium, sulphur and a molten salt electrolyte, the new device could “fill that gap” for renewables, the researchers said – one which they claimed lithium-ion batteries are still too expensive to fill.

“I wanted to invent something that was better, much better, than lithium-ion batteries for small-scale stationary storage, and ultimately for automotive,” said MIT professor Donald Sadoway, who worked with others at MIT and in China, Canada, Kentucky and Tennessee.

Aluminium and sulphur were picked for their low cost and abundance, making up the two electrodes.

For the electrolyte, Sadoway was keen to avoid the “volatile, flammable organic liquids” that can sometimes lead to fires. The team explored using some polymers but ended up looking at a variety of molten salts with relatively low melting points, close to the boiling point of water. At lower temperatures it becomes practical to make batteries that do not require special insulation and anticorrosion measures, Sadoway said.

In its experiments, the team showed the battery cells could endure hundreds of cycles at ‘exceptionally high’ charging rates, with a projected cost per cell of about one-sixth of comparable lithium-ion cells. The charging rate was highly dependent on the working temperature, with 110ºC 25-times faster than 25ºC. The required heat is produced by the charging and discharging of the battery.

The molten salt was found to be very good at preventing dendrite formation, allowing for “very rapid charging,” according to Sadoway. “We did experiments at very high charging rates, charging in less than a minute, and we never lost cells due to dendrite shorting.”

The new battery formulation would be ideal for installations of the size needed to power a single home or a small-to-medium business, Sadoway said, providing a few dozen kilowatt-hours of storage capacity. Their small scale could also make them practical for uses such as EV charging stations, he added.

The technology is already the basis for a new spinoff company called Avanti, which has licensed the patents to the system. “The first order of business for the company is to demonstrate that it works at scale,” Sadoway said. It would then be run through a series of stress tests, including hundreds of charging cycles.

Extracted from IMechE website - read more here

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