November 21, 2022


Super-hot salt could be coming to a battery near you: New battery chemistries can help unlock more renewable energy for the grid. (Casey Crownhart, November 17, 2022, MIT Technology Review)

With the mismatch between lithium-ion batteries and our future energy storage needs, it seems like everybody is working on an alternative way to store energy. In just the last year, I've covered iron air and iron flow batteries, plastic ones, and even one startup using compressed carbon dioxide to store energy. 

Now, another technology is making the jump from the lab to the commercial world: molten salt. 

Ambri is a Boston-area startup that's building molten-salt batteries from calcium and antimony. The company recently announced a demonstration project deploying energy storage for Microsoft data centers, and last year it raised over $140 million to build its manufacturing capacity. 

The company says its technology could be 30-50% cheaper over its lifetime than an equivalent lithium-ion system. Molten salt batteries can also exceed 80% efficiency, meaning that a relatively low amount of energy that's used to charge the battery is lost to heat.  

Ambri was founded in 2010 based on research from Donald Sadoway's lab at MIT. The goal was to develop a low-cost product for the stationary storage market, says David Bradwell, the company's founder and CTO. 

The inspiration came from an unlikely place: aluminum production. Using similar chemical reactions to what's used for aluminum smelting, the team built a lab-scale, low-cost energy storage system. But turning this concept into a real product hasn't been so straightforward.

The magnesium and antimony-based chemistry the company started out with proved difficult to manufacture. In 2015, after continuing issues with the batteries' seals, Ambri laid off a quarter of its staff and went back to the drawing board. 

In 2017, the company pivoted to a new approach for its batteries, using calcium and antimony. The new chemistry relies on cheaper materials, and should prove simpler to manufacture, Bradwell says. Since the pivot, the company has worked out technical glitches and made progress on commercialization, going through third-party safety testing and signing its first commercial deals, including the Microsoft one. 

Posted by at November 21, 2022 12:48 AM