Graphite is one of those quiet, unassuming materials that sit at the foundation of modern life. It’s the slippery dark core of a pencil, yes, but far more consequentially, it is the workhorse anode material inside the lithium-ion batteries that power smartphones, laptops, electric vehicles, and grid-scale energy storage.
It also plays an essential role in industrial power equipment, lubricants, and steelmaking. Yet despite its centrality to the clean energy transition, the United States has almost no domestic production capacity: nearly all graphite consumed in the country today is mined abroad and imported, a supply-chain vulnerability that has long troubled policymakers and industry strategists alike.
Now, a team of researchers spanning two continents has demonstrated a promising route toward flipping that equation. Scientists from the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), the University of California, Berkeley, and Estonia’s National Institute of Chemical Physics and Biophysics (KBFI) have shown how to take carbon dioxide — a waste gas pulled straight from the atmosphere or captured from industrial exhaust — and transform it into solid graphite through a process known as molten-salt electrolysis.
Their work, published recently in the journal Nature Communications, marks the first time anyone has been able to watch this conversion unfold in real time at the molecular level.
A decades-old puzzle
Molten-salt electrolysis is not itself a new idea. For years, researchers have understood, at least in broad strokes, which passing an electric current through hot liquid salts loaded with dissolved carbon dioxide could yield solid carbon.
But the precise chemical pathway — the step-by-step choreography of atoms and electrons — had remained stubbornly opaque. The reason is straightforward: molten salts are an extraordinarily hostile environment for instrumentation. At 500 degrees Celsius (roughly 932 degrees Fahrenheit), the electrolyte is both scorching and corrosive, chewing through conventional probes and shattering most optical windows.
The Berkeley-led team solved this problem by building a custom microscope setup from the ground up. The apparatus was specifically engineered to survive and observe inside a working molten-salt electrolysis cell, allowing the researchers to perform operando Raman spectroelectrochemistry — a mouthful of a phrase that essentially means they could shine a laser into the bubbling, 500-degree bath and read the vibrational fingerprints of the molecules in real time without ever pausing the reaction.
What they found upended the prevailing model. Instead of a single-step electrochemical reduction, the reaction proceeds through a two-step mechanism. First, carbon dioxide is converted into a peroxide intermediate at the electrode surface.
Only then does that intermediate get further reduced to deposit solid carbon. Identifying the peroxide middleman resolved a decades-old debate about how molten carbonate electrolysis actually works at the molecular scale.
Why the two-step discovery matters
Understanding a reaction’s mechanism might sound like a purely academic indulgence, but in electrochemistry the pathway determines the product. When you reduce carbon dioxide, you can theoretically end up with a sprawling family of outcomes: amorphous carbon, carbon nanotubes, graphene-like flakes, or — if the conditions are just right — crystalline graphite. The structure you get dictates the value of what you’ve made.
Critically, the researchers found that the basic two-step mechanism remained consistent even when they swapped out the electrode materials and changed the composition of the molten salts. That chemical robustness is a major practical advantage. It means that by tuning the electrode surface and the salt mixture, scientists should be able to steer the reaction toward whichever carbon product they want, without breaking the underlying chemistry.
The goal at the top of that list is battery-grade graphite. Graphite destined for a lithium-ion anode needs a highly ordered crystalline structure, with carbon atoms arranged in neat, stacked sheets that lithium ions can slip between during charging and discharging. Synthesising such precise order from a hot electrochemical bath is a formidable challenge, but the new ability to watch the process as it happens gives researchers an unprecedented tool for solving it.
“This is a major win in a larger effort of synthesising 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 path from a successful benchtop experiment to a factory floor is long, and the researchers are candid about the work ahead. The immediate next steps involve systematically screening the parameter space: identifying the optimal combinations of molten salt formulations, electrode materials, operating temperatures, and applied voltages that yield the most valuable carbon products at the highest efficiency.
The temperature question is particularly important. Five hundred degrees Celsius is hot, but it is not intractably so in industrial terms. If the team can demonstrate the process using inexpensive, widely available salts at temperatures that do not demand exotic containment materials, the economic proposition becomes compelling.
A distributed network of moderate-scale reactors, sited near sources of captured carbon dioxide and fed by renewable electricity, could become a new kind of manufacturing infrastructure: one that turns a waste gas into a strategic material.
Scaling up also means addressing engineering challenges that the microscope experiment was never designed to answer. Continuous operation, carbon product collection, electrolyte regeneration, and the long-term durability of electrodes under corrosive conditions are all open questions.
But these are, in the language of the field, “known unknowns” — the kind of practical hurdles that follow naturally from a fundamental breakthrough rather than blocking it.
Critical minerals strategy
This research was conducted under the MINerals for Energy Storage Synthesis (MINES) program, funded by the Department of Energy’s Basic Energy Sciences portfolio. MINES sits within a broader constellation of federally supported efforts to reimagine the supply chains for energy-critical materials.
The logic is straightforward: if the energy transition is going to require vast quantities of lithium, cobalt, nickel, manganese, and graphite, then relying on a handful of foreign mining operations — often concentrated in geopolitically sensitive regions — is a strategic risk.
Graphite is a case study in that vulnerability. China currently dominates every stage of the graphite supply chain, from mining and processing to the production of the spherical, coated graphite that battery manufacturers require.
The US Geological Survey lists natural graphite on its critical minerals roster, and the 2022 Inflation Reduction Act included provisions specifically aimed at building domestic battery-material production. A process that converts captured COâ‚‚ directly into battery-grade graphite aligns with all of these policy priorities simultaneously: it reduces import dependence, it consumes a greenhouse gas, and it does so using electricity that can come from renewable sources.
Beyond the specific promise of synthetic graphite, the team’s custom microscope apparatus represents a methodological leap that could ripple across multiple fields. Molten salts are used in a wide variety of industrial electrochemical processes — from aluminum smelting to nuclear fuel reprocessing — and yet the chemistry inside them has often been inferred rather than observed.
A robust operando spectroscopy platform that can withstand the temperatures and corrosivity of these environments opens the door to studying reaction mechanisms that have resisted direct interrogation for decades.
Sander Ratso, the paper’s first author and a researcher affiliated with both KBFI and the Berkeley team, noted that the ability to detect intermediates in real time transforms the way scientists can approach molten-salt chemistry. Instead of running a reaction, cooling everything down, and trying to reconstruct what happened from the products left behind — a process akin to inferring a conversation from a transcript — researchers can now listen in while the chemical dialogue is still unfolding.