Optimization of graphite anode delamination and contaminant separation via electrical pulsed discharge for direct recycling

This study investigated the direct recycling of graphite anode materials from spent lithium-ion batteries using electrical pulsed discharge (EPD). High-speed imaging showed that direct arc discharge into copper (Cu) foil enabled the efficient delamination of graphite through vapor bubble expansion and shock wave generation. The optimization of sample positioning and discharge pulses influences the discharge behavior, separation efficiency, and material integrity of the samples. Under optimized conditions, over 95% delamination was achieved while maintaining graphite structural integrity, confirmed by XRD, TG-DTA, Raman spectroscopy, and direct observations from optical microscopy and SEM images. ICP-OES and SEM-EDS analyses revealed iron and Cu contaminants from electrode erosion and the anode’s Cu foil. The Cu particles exhibited two morphologies: foil-like fragments from mechanical detachment and spherical particles from arc-induced melting. Post-EPD separation methods, including wet sieving, elutriation, and acid leaching, were evaluated for contaminant removal from the concentrates. Wet sieving isolated low-contamination fractions, whereas elutriation recovered high-purity graphite fractions. Acid leaching reduced the Cu concentrations, particularly in the fine fractions containing porous spherical Cu particles. The results show that the optimized EPD conditions, strategic positioning, and sequential separation processes enable the recovery of intact, high-purity graphite for the direct recycling of spent anodes.

[Keywords]

Lithium-ion batteries; Contaminant separation; Recycling; Structural integrity; Elutriation.