Cornell researchers have developed an electrochemical solution that can regenerate the electrodes of lithium-ion batteries. The recycled batteries could then regain up to 95% of their original power and last longer when reused.
Published in Energy and Environmental Science by lead author postdoctoral researcher Kiwon Kim, the project to recycle lithium-ion batteries was led by Vibha Kalra, the Fred H. Rhodes Professor of Chemical Engineering in the Cornell Duffield College of Engineering.
Co-authors include doctoral student Chenlu Yang and Sabine Gallagher at Argonne National Laboratory, with additional support provided by the Pao-Wang Fellowship.
Subverting the linear “take-make-dispose approach” of batteries
Spent lithium-ion batteries, when they are not causing extremely hot fires in electric vehicles, often end up in landfill, where they leak chemicals into the surrounding environment. As well as this detrimental effect on nature, this approach is in conflict with the limited global supply of critical raw materials like nickel and cobalt, which are needed to manufacture lithium-ion batteries.
“When these lithium-ion batteries came about, nobody was thinking about how these minerals are limited on the Earth’s crust, and you cannot make them forever,” Kalra said. “In recent years, people are realizing you can’t just keep making batteries, because you don’t have enough material. And there’s obviously a lot of geopolitical vulnerabilities, because the U.S. in particular does not have much of the reserves.”
Creating a domestic loop to recycle lithium-ion batteries
The traditional method of recycling lithium-ion batteries involves smelting them at high temperatures to produce an alloy and slag(pyrometallurgy), or crushed and shredded into a powder that is processed with harsh acids (hydrometallurgy) to recover critical elements.
Components have to then be resynthesised and refabricated, a costly and time-consuming process that is lengthened by the US’s lack of extraction infrastructure.
Kalra’s team developed a method called direct electrode-to-electrode regeneration (DEER), in which a spent battery’s individual electrodes are removed while still intact and attached to the current collector and are placed in a separate cell that contains an electrochemical solution: 1,3-dimethyl-2-imidazolidinone. The solution dissolves the thick insulating layer, known as the solid electrolyte interphase, that gradually builds up between the cathode and anode as the battery gets cycled, gradually diminishing its capacity over time.
“We repair them, as is, without shredding or powdering them, and then put them back into a new battery,” said Kalra, the Kathy Dwyer Marble and Curt Marble Faculty Director at the Cornell Atkinson Center for Sustainability, which supported the research. “The dissolution is basically what helps the battery recover its capacity. It shows 95% recovery. So we are shortening the circularity loop immensely.”
Kalra and Kim worked with Shuwen Yue, assistant professor in the R.F. Smith School of Chemical and Biomolecular Engineering and a co-author of the paper, to better understand the solvation dynamics as the interphase gets dissolved out. Then, working with open-source software developed by their research collaborators at Argonne National Laboratory’s ReCell Center, the team performed techno-economic and environmental impact analyses to determine the potential impact of DEER.
The analysis showed it would cut the cost of recycled cell manufacturing by 56% and would reduce harmful air pollutants and water use compared to the pryo- and hydro-based processes.
The next step will be to demonstrate DEER on industrial batteries as well as targeting other forms of battery degradation, such as lithium loss.
“Right now, the spent batteries we are treating have 70-80% state of health, which is typical in electric vehicle applications,” Kalra said. “So we can expand that window if we can address some of these other degradation mechanisms.”