Copyright Interesting Engineering
Iron, one of Earth’s most common and unassuming metals, has just surprised scientists. A Stanford-led team has discovered how to push iron into a higher-energy state than ever seen before, a feat that could reshape the future of lithium-ion batteries and other energy technologies. The breakthrough shows that iron can release and reabsorb more electrons than previously thought possible, potentially enabling batteries that are both more powerful and far cheaper than today’s cobalt- or nickel-based versions. The finding could also influence other technologies that rely on magnetic and electronic properties, from MRI machines to maglev trains and even superconductors. The discovery was achieved by three Stanford PhD students — Hari Ramachandran, Edward Mu, and Eder Lomeli, leading a 23-member team across several U.S. universities, national laboratories, and international partners in Japan and South Korea. Together, they found a way to coax iron into a state once considered unreachable. Their key innovation lies in fine-tuning the structure of a compound made from lithium, iron, antimony, and oxygen. When arranged at the nanoscale, the material allowed iron atoms to repeatedly give up and reabsorb five electrons, well beyond the usual two or three. Bending without breaking When Ramachandran and Mu began their research in 2021, their early samples kept collapsing during charging cycles. The team realized the solution was to make the material’s particles extremely small. “Making the particles very small – just 300 to 400 nanometers, or billionths of a meter, in diameter, about 40 times smaller than before – turned out to be a challenge,” said Ramachandran. Eventually, the duo figured out how to grow their crystals from a carefully mixed liquid solution. “In our electrochemical tests, the material seemed to get iron to reversibly give up and later take back five electrons while the crystal structure remained stable,” Mu said. To verify what was happening inside, Lomeli teamed up with his advisor, Tom Devereaux, who specializes in modeling X-ray spectra. Lomeli’s analysis confirmed that the additional electrons were not just coming from the iron atoms alone but with crucial help from oxygen. “It’s too simple to say that iron is the hero or oxygen is the hero,” he said. “The atoms in this very nicely arranged material behave like a single entity.” The new iron age Iron’s comeback in battery science marks a turning point. Once dismissed as too low-voltage for advanced energy storage, iron-based cathodes are now emerging as sustainable alternatives to cobalt, which is expensive and often mined under hazardous conditions. “A high-voltage, iron-based cathode could avoid the tradeoff between higher voltage and higher-cost metals that previously dominated cathode materials,” Mu said. The idea traces back to 2018, when former Stanford PhD student William Gent theorized that iron could be pushed to higher oxidation states if neighboring atoms were carefully spaced apart. Gent never got the chance to complete the experiment, but the new team did. At Stanford’s SLAC-Stanford Battery Center, early tests showed that the lithium–iron–antimony–oxygen compound stayed structurally intact, bending slightly rather than breaking during charge cycles.
