As the need for lithium-ion batteries rises due to the growing use of mobile devices, electric cars, and even medical devices like pacemakers, the extraction of essential materials, such as cobalt, raises serious ethical and environmental issues. Recently, researchers have developed a safer and more sustainable approach to extract cobalt from ores or recycled sources using precipitation methods.
Researchers at the University of Pennsylvania have led a collaborative initiative to create a safer, more sustainable process for isolating key elements essential to battery technologies, opening avenues to extract value from materials typically seen as waste.
Siddarth Kara’s book, “Cobalt Red: How the Blood of Congo Powers Our Lives,” highlights the challenges associated with cobalt sourcing, a vital element found in lithium-ion batteries used in numerous modern technologies, from smartphones to electric vehicles and pacemakers.
“Many of us understand how crucial lithium-ion batteries are for storing energy,” states Eric Schelter, the Hirschmann-Makineni Professor of Chemistry at the University of Pennsylvania. “However, the methods used to extract the materials for these batteries are often fraught with ethical and environmental issues.”
Schelter points out that cobalt mining in the Democratic Republic of Congo, which provides roughly 70% of the world’s cobalt, poses risks due to environmental degradation and poor labor conditions. Furthermore, large-scale mining activities disrupt ecosystems, potentially contaminating water supplies and causing lasting environmental harm. With the increasing demand for battery technologies, he emphasizes that a potential cobalt shortage could strain global supply chains.
His lab is actively researching ways to separate essential battery metals like nickel and cobalt. In a recent publication in the journal Chem, Schelter’s team, along with collaborators from Northwestern University, introduced a “simpler, more sustainable, and cost-effective method for extracting these metals from materials that would otherwise be discarded.”
“Our methodology is appealing because it’s straightforward, efficient, and effectively separates nickel and cobalt—a challenging task in the field,” Schelter explains. “This solution provides two significant advantages: it enhances the production capacity of purified cobalt from mining operations with minimal environmental impact and finds value in discarded batteries by efficiently separating nickel and cobalt.”
The right ingredients for selective separation
The researchers typically encounter cobalt as a byproduct in nickel mining through hydrometallurgical processes such as acid leaching and solvent extraction, which can be energy-intensive and produce considerable hazardous waste.
The new method developed by Schelter and his team uses a chemical-separation technique that capitalizes on the differing charge density and bonding properties of two molecular complexes: cobalt (III) hexammine and nickel (II) hexammine.
“Separation chemistry focuses on manifesting the differences in the substances you wish to divide,” Schelter remarks. “In this instance, we discovered conditions under which ammonia—a relatively simple and affordable reagent—binds differently to the nickel and cobalt hexammine complexes.”
By adding a specific negatively charged molecule, or anion, like carbonate to the reaction, they produced a molecular solid structure that facilitates the precipitation of cobalt out of the solution while keeping nickel dissolved. Their research showed that the carbonate anion engages selectively with the cobalt complex, forming strong “hydrogen bonds” to create a stable precipitate. After precipitation, the cobalt-rich solid can be isolated through filtration, then washed with ammonia and dried. The remaining solution can be processed to extract nickel separately.
“This method not only achieves high purity levels for both metals—99.4% for cobalt and over 99% for nickel—but it also eliminates the use of harmful organic solvents and aggressive acids common in traditional separation processes,” explains first author Boyang (Bobby) Zhang, a graduate student at Penn’s School of Arts & Sciences and a Vagelos Institute for Energy Science and Technology Graduate Fellow. “It’s a fundamentally simple and scalable technique that provides both environmental and economic benefits.”
Techno-economic and life cycle analyses
The research team, led by Marta Guron, assessed the practical application of their new technique through a techno-economic analysis and a life-cycle assessment. The analysis indicated a production cost of $1.05 per gram of purified cobalt, significantly lower than the $2.73 per gram associated with traditional separation methods.
“We aimed to reduce chemical costs while utilizing readily available reagents, positioning our method as competitive against current technologies,” Schelter stated.
The life-cycle analysis revealed that removing volatile organic compounds and hazardous solvents significantly lowers environmental and health risks. Metrics such as Smog Formation Potential and Human Toxicity by Inhalation Potential demonstrated that their process performed dramatically better than conventional methods.
“This translates to fewer greenhouse gas emissions and reduced hazardous waste, which is a substantial achievement for both the environment and public health,” Zhang added.
Cleaner path forward
Given their innovative separation method, Schelter highlights that a fascinating aspect of their research could lead to various new applications in metal separation challenges.
“With the unique molecular recognition principles we’ve uncovered, I believe we can explore this work in diverse directions,” he mentioned. “We could adapt it for other metal separation challenges, ultimately fostering broader innovation in sustainable chemistry and materials recovery.”
Eric Schelter is the Hirschmann-Makineni Professor of Chemistry in the Department of Chemistry at the School of Arts & Sciences at the University of Pennsylvania.
Boyang (Bobby) Zhang is a Vagelos Institute for Energy Science and Technology Graduate Fellow in the Schelter Group at Penn Arts & Sciences.
Marta Guron is an adjunct lecturer in the Department of Chemistry and a project manager in the Office of Environmental and Radiation Safety.
Other contributors include Andrew J. Ahn, Michael R. Gau, and Alexander B. Weberg from Penn and Leighton O. Jones and George C. Schatz from Northwestern University.
This research was funded by the Vagelos Institute for Energy Science and Technology at Penn, the Vagelos Integrated Program in Energy Research at Penn, the National Science Foundation Center (Award CHE-1925708), the Center for Advanced Materials for Energy Water Systems through the U.S. Department of Energy (Grant 8J-30009-0007A), and the Research Corporation for Science Advancement (Award #CS-SEED-2024-022).
