Progress on recycling graphite cathode from spent lithium-ion batteries

The rapid development of the new energy vehicle industry promotes the achievement of “dual-carbon” goals. Graphite has become the mainstream cathode material because of its high conductivity, capacity, and stability. Demand for graphite and the importance of end-of-life issues have grown rapidly with the booming of the Li-battery vehicle industry. Waste graphite cathodes are important resources of valuable materials, including Li, Cu, and graphite. However, they are also classified as solid wastes and cause potential environmental issues owing to the presence of binders, electrolytes, fluoride, etc. Hence, efficient and clean recycling of spent graphite has recently attracted considerable attention. In this review, the global distribution of mineral resources and the consumption structure of graphite are introduced. The graphite mineral reserve in China is quite abundant, approximately 15.7% of the world’s reserves. Meanwhile, the production and consumption of graphite in China is 65.4% and 86.6% of the global total, respectively. Its use in batteries as anodic materials is increasing. To improve the recycling technology of graphite cathodes, the progress in recycling them from spent lithium-ion batteries is reviewed systematically. Recycling methods, including physical separation, hydrometallurgical leaching, pyrometallurgy, and other methods, are elaborated. Graphite modification methods (e.g., element doping, carbon coating, and material compositing) used to enhance the electrochemical properties of regenerated graphite are summarized. Furthermore, the preparation of new functional materials from waste graphite has attracted considerable attention, for example, its reuse as graphene and graphene oxide, capacitors, adsorbents, and catalysts. However, because of the differences in graphite anode material manufacturers and various situations of failures and damage levels, obtaining uniform high-performance graphite products is highly challenging. The environmental issues arising from the disposal of electrolytes, organic binders, and hazardous metal ions in wastewater cannot be ignored. Currently, recovery technologies are complex and can only achieve a single goal, such as the purification of graphite by acid leaching. Therefore, a short, low-cost, and efficient process must be developed to achieve high-performance graphite products. More importantly, for graphite anode regeneration and reuse, the corresponding product standard system must be established to promote the industrial application of waste graphite anode recycling.