Development of a Cost-Effective Process for the Regeneration of Graphite from Spent LIBs without High-Temperature and Acid Treatments

Abstract

The rapid growth of the lithium-ion battery (LIB) industry has led to a surge in end-of-life batteries. However, current recycling methods mainly target cathode materials, and graphite anodes, despite supply- chain risks, receive little attention, increasing environmental impacts and disposal costs. Recycling methods for spent graphite rely on acid leaching or high-temperature treatments, which raise concerns about chemical use, energy consumption, and sustainability. To address these challenges, this study develops an acid-free regeneration process that recovers high- performance graphite from hydrometallurgically treated recycling residues. Metallic impurities in spent graphite (SG) are first removed using optimized ultrasonic treatment and ball milling, where controlled fragmentation detaches and exposes embedded contaminants. This process reduces the ash content from 7.1 wt% to 0.5 wt% with a 72% yield, and ICP–OES analysis confirms that most metallic impurities are reduced to near or below detection limits. Residual organic species from binders and SEI are decomposed by annealing at 500 °C under Ar, as confirmed by TGA, TEM, and F 1s XPS. Moreover, XRD and Raman analyses indicate that the graphite crystal structure is preserved and that surface contamination is significantly reduced. To restore particle morphology, purified graphite is granulated with pitch and then carbon-coated, producing regenerated graphite (RG) with spherical particles and a tap density comparable to that of commercial graphite. In half-cells, RG delivers a reversible capacity of 351 mAh g⁻¹, an initial Coulombic efficiency of 92%, and maintains 98% of its capacity over 400 cycles, outperforming commercial graphite in long-term stability. Furthermore, pouch-type NCM622‖RG full cells (2.5 mAh cm⁻²) show an initial Coulombic efficiency of 86% and retain 93% of their capacity after 200 cycles. Finally, life-cycle assessment shows that the proposed process reduces energy consumption and global warming potential by about 90% compared with artificial graphite and by over 60% compared with natural graphite. Taken together, these results show that acid-free impurity removal and morphological reconstruction offer a practical, environmentally favorable path to closing the loop on graphite anodes in next-generation LIB recycling.