Direct recycling of carbon black and graphite from an aqueous anode slurry of lithium-ion batteries by centrifugal fractionation

Centrifugation is a promising method for direct recycling of lithium-ion battery materials from an aqueous slurry. The present work investigates the continuous fractionation of an aqueous anode slurry into the active material graphite and the conductive carbon black in a decanter centrifuge. To evaluate the separation success, two analytical methods utilizing the different particle sizes and sedimentation velocities of the materials were developed and tested. Both methods can detect graphite separation efficiencies up to 90 % based on centrate samples. The detectability of carbon black in sediment samples is more sensitive for the sedimentation analysis, which can measure carbon black separation efficiencies down to 1 %, in contrast to the particle size analysis, allowing the detection of separation efficiencies down to 10 %. Both methods provide similar results in terms of assessing the separation process in the lab-scale decanter centrifuge. At a centrifugal acceleration of 352 g and a volume flow of 66 l/h, more than 90 % graphite can be separated with a low carbon black deposition between 10 % and 20 %. Thus, a high recovery of graphite and carbon black from an aqueous anode slurry by using a decanter centrifuge is basically possible.