Graphite Recycling from the Spent Lithium-Ion Batteries by Sulfuric Acid Curing–Leaching Combined with High-Temperature Calcination

Recycling graphite from spent lithium-ion batteries plays a significant role in relieving the shortage of graphite resources and environmental protection. In this study, a novel method was proposed to regenerate spent graphite (SG) via a combined sulfuric acid curing, leaching, and calcination process. First, we conducted a sulfuric acid curing–acid leaching experiment and systematically investigated the effects of various operation conditions on the removal of impurities. Regenerated graphite was obtained after a sequential calcination at 1500 °C, and its morphology and structure were characterized by using X-ray diffraction, Raman spectroscopy, and spherical aberration electron microscopy analysis. The results show that the impurity removal efficiency by sulfuric acid curing–acid leaching is much higher than that by direct acid leaching, and the purity of the regenerated graphite can reach 99.6%. Additionally, the regenerated graphite displays favorable characteristics in morphology and structure, which are close to that of a commercial unused material. The regenerated graphite exhibits good electrochemical performance in charge capacity and cycle. The initial charge capacity and retention rate are 349 mA h/g and 98.8%, respectively. This recycle method has the advantages of low energy consumption and low waste acid discharge and can be performed by easily available equipment, so it may have great prospect for the industrial-scale recycling of SG.