Selective electrodeposition has been used to recover cobalt and nickel from commercially available lithium nickel manganese cobalt – NMC – oxide battery electrodes.
The method, developed by a team led by University of Illinois Urbana-Champaign chemical and biomolecular engineering professor Xiao Su, is said to produce final product purities of approximately 96.4 per cent and 94.1 per cent for cobalt and nickel, respectively, from spent NMC electrode wastes.
Published in Nature Communications, the new method could make spent batteries a highly sustainable secondary source of the two metals.
According to Su, cobalt and nickel have similar electrochemical properties – or standard reduction potentials – making it challenging for chemists to recover pure forms of each metal from battery electrodes.
“There are a variety of methods available for the recovery of cobalt and nickel from battery electrodes, but they have drawbacks,” Su said in a statement. “Most require energy-intensive high-temperature processes or strong solvents that present disposal challenges. The industry demands methods that will not cause additional problems like high energy consumption or toxic waste.”
UIUC state that the unique aspect of this study is the development of a tuneable liquid electrolyte and polymer coating on the electrodes.
In the laboratory, the researchers combined the electrolyte-polymer method with dismantled, leached and liquefied components of fully discharged NMC battery electrodes. By adjusting the salt concentrations of the electrolyte and the thickness of the polymer coating, researchers noted that distinct deposits of cobalt and nickel accumulated on the electrode surfaces through sequential electrodeposition. By the end of the process, the electrode had collected high-purity coatings of the two metals.
An economic analysis of the new approach showed that it was competitive with current Li-battery recycling methods once material revenue, material cost and energy consumption were all considered, the study reported.
“There’s further engineering optimisation of the process that will be needed going forward, but this first proof-of-concept study confirms that low-temperature cobalt and nickel electrochemical recovery is possible,” Su said. “We’re very excited because the study shows a great example of sustainable electrically driven separations being used to recycle electrochemical batteries.”