Electrochemical Recovery of Critical Metals from Lithium-Ion Battery Waste

Critical metals found in lithium-ion batteries (LIBs), nickel and cobalt, need to be recovered from LIB waste to maintain a circular economy of these critical metals in the United States. Current approaches to critical metal recovery are energy-intensive, environmentally taxing, and have limitations on which metals they recover from LIB waste. This study aims to find an electrochemical method to selectively recover metals from LIB waste using an environmentally friendly solvent, a deep eutectic solvent (DES). A 1:2 molar ratio of choline chloride to urea DES was used to dissolve the LIB waste. Ni and Co have very similar electrochemical properties when dissolved in DES and have issues selectively electroplating onto a substrate. In lower applied potentials, both Ni and Co electroplate onto the substrate together. To facilitate this issue, cyclic voltammetry was utilized to calculate the diffusion coefficient for Ni and Co. It was found that Ni has a higher diffusion coefficient in DES than Co, therefore it moves through solution faster. By applying a potential in short increments, with a method called “pulse”, Ni was selectively electroplated (98.8% selectivity) from LIB waste dissolved in DES onto a copper foil, the substrate of choice.