30 Jul 2026

 

A real-time look inside molten salts showed how carbon dioxide can be converted into the critical mineral graphite. Researchers hope the process could eventually provide a new source of graphite for battery manufacturing.

 

Graphite, the carbon center of your humble #2 pencil, is also an essential component in technologies such as batteries, smartphones, laptops, and industrial power equipment. Today, nearly all of this critical mineral has to be mined and processed and, in the United States, imported.

But now, researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), UC Berkeley, and Estonia’s National Institute of Chemical Physics and Biophysics have shown a promising way to convert waste carbon pulled from the air into graphite, opening up a potential alternative to mining. The work was published recently in the journal Nature Communications.

Researchers built a custom microscope setup to watch a process known as molten-salt electrolysis, which uses electricity and hot liquid salts to turn carbon dioxide into solid carbon. For the first time, researchers were able to watch the process in real time inside the corrosive, 500-degree-Celsius molten salts while the system was running.

The observations answered a decades-old question about how the reaction actually occurs at the molecular level, revealing an unexpected two-step process. The researchers also found that the basic chemical reaction remained the same even when they changed the materials used for the electrodes and molten salts. Because different materials produce different carbon structures, scientists should be able to tune the process to make valuable carbon products, with an end goal of making battery-grade graphite. 

“This is a major win in a larger effort of synthesizing critical materials and battery materials using molten salts,” said Mike Whittaker, a Berkeley Lab scientist who worked on the project. “If you could run this process at low temperatures with really cheap salts, you could have it in a lot of places, and you could generate enough graphite that you could feed into battery supply chains.”

The team’s approach demonstrates a powerful new way to study chemistry inside molten salts, an environment that has been historically difficult to probe directly because of its harsh conditions. The next step is determining the optimal combinations of molten salts, electrode materials, temperatures, and voltages to make graphite and other carbon materials. Researchers will also need to scale up the approach to produce industrially useful amounts.

 

[Image]

(A) Graphite is a critical mineral used in batteries, laptops, and smartphones. 

(B) A close-up shows the inner experimental set-up to study how carbon dioxide transforms into solid carbon in molten-salt electrolysis. Gray electrodes provide the electricity and serve as the site of chemical reactions with a salt sample (center).