Electrochemical study on the recovery of LiFePO4 battery cathode material in fluoride molten salt

Developing environmentally benign and efficient recycling strategies remains a critical challenge confronting the battery recycling field. High-temperature molten salt electrolysis is a promising method for recovering lithium iron phosphate. The electrochemical behaviors of Fe(III) and P(V) ions on a tungsten working electrode in the NaF-AlF 3 -LiFePO 4 /Fe 2 O 3 /Li 3 PO 4 system were investigated using cyclic voltammetry (CV) and square wave voltammetry (SWV), respectively. Results reveal that both Fe(III) and P(V) undergo two-step electron transfer reduction pathways: Fe(III) → Fe(II) → Fe(0) and P(V) → P(III) → P(0). The reduction oxidation process of Fe is a quasi-reversible process controlled by diffusion, while the process of P is an irreversible process. The reduction potential range of Fe and P does not overlap, and Fe will be reduced first. By controlling the potential, different reduction products of iron and phosphorus are obtained separately. At −1.0 V, Fe is preferentially reduced, and the deposited product is iron powder. At −1.8 V, P and Fe were simultaneously reduced, and they were collected in the form of P 4 and Fe 3 P products, respectively. The remaining lithium can be stored in fluoride molten salts to form lithium containing electrolytes, which are important additives in the aluminum electrolysis industry and can be directly used. The recycling of spent lithium iron phosphate batteries through molten salt electrolysis not only achieves harmless treatment of Fe and P elements, but also provides a new solution for the scarce Li resources in other industries.