Electrochemical Lithium Compensation Enables Sustainable Regeneration of Spent LiFePO₄ Cathodes

Direct regeneration of spent LiFePO₄ (S-LFP) cathodes presents a sustainable method for reclaiming battery materials with low energy and chemical requirements. However, existing direct regeneration techniques usually involve excessive lithium supplementation and uneven composition restoration due to the random distribution of solid lithium sources during reaction. Here, an efficient lithium compensation strategy is reported to regenerate S-LFP cathodes through electrochemical reduction followed by heat treatment. An aqueous Zn||S-LFP cell with LiCl electrolyte is well constructed for lithium compensation. During the galvanostatic discharge, the impure FePO₄ (FP) is reduced in conjunction with lithium compensation, as observed through in situ X-ray diffraction analysis (in situ XRD). The subsequent heat treatment aims to eliminate Li-Fe anti-site defects. The regenerated LiFePO₄ (R-LFP) demonstrates a well-defined olivine crystal structure. The R-LFP cathode exhibits a high capacity of 158.4 mAh g^-1 at 0.2C and retains a high capacity retention of 97.5% after 1000 cycles at 5C. Economic analysis reveals that the direct recycling method generates a profit of $1.92 per kg^-1 of S-LFP, significantly surpassing the profitability of both hydrometallurgical and pyrometallurgical methods. The work proposes a scalable and efficient regeneration method for recycling spent batteries, ensuring economic viability and environmental sustainability for practical applications.