Advances and challenges in anode graphite recycling from spent lithium-ion batteries

Spent lithium-ion batteries (LIBs) have been one of the fast-growing and largest quantities of solid waste in the world. Spent graphite anode, accounting for 12-21 wt% of batteries, contains metals, binders, toxic, and flammable electrolytes. The efficient recovery of spent graphite is urgently needed for environmental protection and resource sustainability. Recently, more and more studies have been focused on spent graphite recycling, while the advance and challenges are rarely summarized. Hence, this study made a comprehensive review of graphite recycling including separation, regeneration, and synthesis of functional materials. Firstly, the pretreatment of graphite separation was overviewed. Then, the spent graphite regeneration methods such as leaching, pyrometallurgy, their integration processes, etc. were systematically introduced. Furthermore, the modification strategies to enhance the electrochemical performance were discussed. Subsequently, we reviewed in detail the synthesis of functional materials using spent graphite for energy and environmental applications including graphene, adsorbents, catalysts, capacitors, and graphite/polymer composites. Meanwhile, we briefly compared the economic and environmental benefits of graphite regeneration and other functional materials production. Finally, the technical bottlenecks and challenges for spent graphite recycling were summarized and some future research directions were proposed. This review contributes to spent LIBs recycling more efficiently and profitably in the future.