New ‘Blue-Green’ Solution for Recycling World’s Batteries

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At 180 degrees Celsius (356 degrees Fahrenheit), the solvent extracted nearly 90 percent of lithium ions, and up to 99 percent of cobalt ions from the powder when certain conditions were satisfied.

The researchers built small prototype batteries and cycled them 300 times before exposing the electrodes to the same conditions. The solvent proved adept at dissolving the cobalt and lithium while separating the metal oxides from the other compounds present in the electrode.

The blue-green color of solutions reveals the presence of cobalt taken from spent lithium-ion batteries through a new process developed at Rice University. (Photo by Jeff Fitlow/Rice University)Long Description

Image Caption: The blue-green color of solutions reveals the presence of cobalt taken from spent lithium-ion batteries through a new process developed at Rice University. Photo by Jeff Fitlow

They found that cobalt could be recovered from the eutectic solution through precipitation or even electroplating to a steel mesh, as this latter method potentially allowed for the deep eutectic solvent itself to be reused.

“We focused on cobalt,” said Rice alumnus Marco Rodrigues, now a postdoctoral researcher at Argonne National Laboratory. “From a resource standpoint, it’s the most critical part. The battery in your phone will surely have lots of it. Lithium is very valuable too, but cobalt in particular is not only environmentally scarce but also, from a social standpoint, hard to get.”

He noted the Department of Energy is mounting new efforts to advance battery recycling technologies and recently announced a center for Li-ion battery recycling.

The path forward will require continued efforts.

“It’s likely we won’t be able to recycle and replace mining completely,” Tran said. “These technologies are relatively new, and there is a lot of optimization that needs to be done, such as exploring other deep eutectic solvents, but we truly believe in the potential for greener ways to do dirty chemistry. Sustainability is in the heart of the work I do and what I want to do for the rest of my career.”

Graduate student Keiko Kato is a co-author of the paper. Ajayan is the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of chemistry.

The National Science Foundation supported the research through its Graduate Research Fellowship Program.

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