What if a common element, rather than scarce and expensive ones, became a key component in electric car batteries? A groundbreaking collaboration, co-led by an Oregon State University chemistry researcher, is aiming to ignite a green battery revolution by demonstrating that iron can replace cobalt and nickel as a cathode material in lithium-ion batteries.
The findings, published in Science Advances, hold significant promise for both economic and environmental reasons, as highlighted by Oregon State's Xiulei “David” Ji.
“We've transformed the reactivity of iron metal, the cheapest metal commodity,” Ji explained. “Our electrode can offer a higher energy density than the state-of-the-art cathode materials in electric vehicles. And since we use iron, which costs less than a dollar per kilogram—a small fraction of the price of nickel and cobalt used in current high-energy lithium-ion batteries—the overall cost of our batteries could be much lower.”
Currently, the cathode accounts for 50% of the cost of manufacturing a lithium-ion battery cell. Beyond the economic benefits, iron-based cathodes promise greater safety and sustainability.
As the global production of lithium-ion batteries escalates to support the electrification of transportation, the demand for nickel and cobalt has surged. Ji warns that in a couple of decades, predicted shortages of these metals could hinder battery production as it currently stands.
Moreover, the energy density of these elements is already approaching its maximum limit. Pushing beyond this could lead to the release of oxygen during charging, increasing the risk of battery fires. Additionally, cobalt is toxic and poses significant environmental hazards if it contaminates ecosystems and water sources from landfills.
Given these challenges, the global quest for new, more sustainable battery chemistries is easy to understand.
Batteries store power as chemical energy, converting it to electrical energy needed for vehicles, cellphones, laptops, and many other devices. Despite variations, most batteries function similarly and contain the same basic components: two electrodes (anode and cathode), a separator, and an electrolyte. During discharge, electrons flow from the anode to the cathode through an external circuit.
In lithium-ion batteries, lithium ions carry the charge through the electrolyte from the anode to the cathode during discharge and back again during recharging.
“Our iron-based cathode will not be limited by resource shortages,” said Ji. He noted that iron, the most common element by mass on Earth, is also the fourth-most abundant element in the Earth's crust. “We won't run out of iron until the sun becomes a red giant.”
Ji and his collaborators from multiple universities and national laboratories enhanced iron's reactivity in their cathode by creating a chemical environment with a mix of fluorine and phosphate anions—negatively charged ions. This blend, mixed as a solid solution, enables the reversible conversion of iron powder, lithium fluoride, and lithium phosphate into iron salts, meaning the battery can be recharged.
“We've shown that using anions in material design can break the energy density ceiling for batteries that are more sustainable and cost-effective,” Ji stated. “We're not using more expensive salts—just the same ones the battery industry uses, plus iron powder. To implement this new cathode, nothing else needs to change—no new anodes, production lines, or battery designs. We are simply replacing the cathode.”
While storage efficiency still needs improvement—currently, not all electricity put into the battery during charging is retrievable upon discharge—Ji is optimistic. With advancements, the result will be a superior battery that is more cost-effective and environmentally friendly.
“If there is investment in this technology, it shouldn't take long to become commercially available,” Ji said. “We need industry visionaries to allocate resources to this emerging field. The world can have a cathode industry based on an almost free metal compared to cobalt and nickel. Plus, while recycling cobalt and nickel is challenging, you don't even have to recycle iron—it just rusts.”
The research was co-led by Tongchao Liu of Argonne National Laboratory and included contributions from Oregon State's Mingliang Yu, Min Soo Jung, and Sean Sandstrom, along with scientists from Vanderbilt University, Stanford University, the University of Maryland, Lawrence Berkeley National Laboratory, and the SLAC National Accelerator Laboratory.
Source: Oregon State University