Organic acid-assisted vapor phase reduction for high-dense defects of retired graphite for high-performance lithium-ion batteries

Recycling and reusing anode graphite from spent lithium-ion batteries are now essential strategies to achieve green sustainability and clean-energy storage. However, viable and affordable regeneration methods of anode have become a significant obstacle for the recovery procedure. Hydrometallurgy has shown efficiency and sustainability in the recovery of critical materials from LIBs, and heat treatment is confirmed to be required to reconstruct the structure of graphite. In this study, oxalic acid is used as the leaching agent and subsequent heat treatment is conducted to repair the graphite structure. The leaching results showed that oxalic acid has a higher leaching rate of lithium ions (96.10%). Interestingly, CO₂ or CO-diffusion from oxalic acid thermal decomposition can be controlled rationally by nanoconfined structures in spent graphite, resulting in carbon defects. Electrochemical performance test results reveal that the recovered graphite exhibits improved specific capacity and stability, retaining 356.45 mAh g⁻¹ at 0.1C after 300 cycles and a coulombic efficiency of over 97%. Its performance is comparable to that of artificial graphite and superior to most reported acid-leaching-based recycled graphite. Thus, the outcomes point to a viable technique for recovering and reusing spent graphite anode.