One-Pot Molten-Salt Strategy for Simultaneous Separation and Regeneration of Spent LiFePO4 Cathodes

Abstract

The sustainable recycling of spent lithium iron phosphate (LiFePO4) cathodes is essential for developing circular economy strategies for lithium-ion batteries (LIBs). Herein, we report a low-temperature one-pot molten-salt strategy based on a eutectic NaNO3-KNO3 system for the simultaneous separation, purification and regeneration of spent LFP cathodes. Unlike conventional recycling routes requiring multistep delamination and material separation, the intact spent cathode is directly treated in the molten salt without prior removal of the aluminum current collector. The molten-salt medium provides a chemically selective reaction environment that enables efficient decomposition of polymeric binder, oxidation of conductive carbon, removal of residual Al impurities, and clean separation of the active material from the aluminum substrate while preserving the olivine LiFePO4 framework. ICP-OES analysis confirms a reduction in residual Al content from 0.155 to 0.087 wt %, indicating effective purification of the regenerated material. Simultaneously, the high ionic mobility of the molten-salt system facilitates crystallographic repair, the suppression of Fe/Li antisite defects, and restoration of electrochemically accessible Li-ion diffusion pathways without external lithium supplementation. R-LFP delivers a discharge capacity of 115.3 mAh g–1 at 100 mA g–1 with 99.4% capacity retention after 300 cycles, representing a 20.3% improvement over S-LFP. Furthermore, R-LFP ∥ graphite full cells maintain a discharge capacity of 43.2 mAh g–1 at 1000 mA g–1 after 500 cycles. This work demonstrates a potentially scalable and energy-efficient one-pot molten-salt separation and purification strategy for the selective recovery and regeneration of LFP from spent cathodes, providing a practical pathway toward simplified and sustainable closed-loop recycling of LIBs.