Sustainable Upcycling of Spent Graphite Anodes via Concentrated Sulfuric Acid

As the application of lithium-ion batteries (LIBs) becomes increasingly widespread, the amounts of spent batteries are rising year by year. The recycling of LIBs is essential for environmental protection, battery safety and resource sustainability. However, the recycling of graphite anodes is overlooked due to its relatively lower economic value compared to the valuable metal resources of cathodes. Herein, a simple, eco-friendly and low-cost upcycling strategy that simultaneously accomplishes the restoration and modification of spent graphite anodes via concentrated sulfuric acid is presented, which can thoroughly remove impurities, introduce oxygen-containing functional groups and facilitate the carbonization of residual organic components to form an amorphous carbon coating. The upcycled graphite demonstrates high specific capacity, excellent rate capability and stable cyclability. The reversible specific capacity is as high as 391 mAh g^-1 and ≈100% capacity retention after 100 cycles at 0.2 C, which is even higher than the theoretical capacity of graphite (372 mAh g^-1). Furthermore, the concentrated sulfuric acid can be reused for at least 5 times, demonstrating the technical and economic feasibility of concentrated sulfuric acid in regeneration process. This work provides a sustainable integrated approach to regenerate and upcycle spent graphite anodes with significant economic, strategic and ecological values.