Optimizing shear-dominant stripping with controlled stress for efficient recovery of cathode active materials from spent lithium-ion batteries

During the recovery of spent lithium-ion batteries, the stripping process plays a critical role in determining the extent of cathode active materials (CAMs) recovery. However, traditional physical methods, characterized by an impact-dominant force, can only pulverize both CAMs and aluminum (Al) foil together, resulting in low stripping efficiency and high impurity content. In this study, a shear-dominant stripping method is proposed to control the stress exerted on the cathode. The stress calculation result shows that the shear-dominant force can apply stress levels higher than the ultimate tensile stress of the CAMs coating but lower than that of the Al foil. Contrasting different physical methods, the vertical agitating mill processing with shear-dominant force achieved a remarkable stripping efficiency and low impurity content. Then, the impeller structure in the mill was redesigned and optimized using the discrete element method (DEM). Results show that the blade ribbon impeller promotes full contact between the particles while enhancing shear actions significantly. Using the designed impeller structure, the stripping efficiency and purity of the CAMs reached 98.98% and 99.92%, respectively. This method presents a notable advantage over traditional physical methods, positioning it as a promising and viable technology for industrial applications in spent LIBs recovery.