Direct Construction of a LiF-Rich Interphase for Sustainable Regeneration of Spent Graphite Electrodes via In Situ Decarbonization-Fluorination Strategy

Recycling graphite anodes is critical due to the high economic and environmental costs of producing battery-grade graphite. However, traditional recycling primarily regenerates graphite powder through complex steps like separation and purification. In spent graphite anode materials, the primary cause of electrochemical failure is the surface formation of a thick, poorly conductive solid electrolyte interphase (SEI) layer. Herein, a decarbonization-fluorination strategy is developed to directly regenerate spent graphite electrodes. The process can convert the poorly conductive SEI layer into a highly conductive LiF-rich layer by reacting Li₂CO₃ present in the SEI with an NH₄F solution. This reconstructed interface boosts ionic conductivity, lowers interfacial resistance, and creates a fast pathway for lithium ions. The regeneration graphite electrode exhibits a high specific capacity of 303.9 mAh g⁻¹ at 0.5 C and a capacity retention of 92.3% after 500 cycles. The LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811)//regenerated graphite pouch cell (550 mAh) shows a 92% capacity retention after 200 cycles at 1 C. Furthermore, its areal capacity is 4.9 times higher than that of a spent graphite pouch cell. The techno-economic analysis indicates cost reductions ≈78% compared to conventional approaches. This work lays the foundation for a more sustainable technology for the direct recovery of graphite electrodes. © 2025 Wiley-VCH GmbH.