Homogenization-confined-repair regeneration of spent LiFePO₄ cathodes via tunable pre-oxidization and microencapsulation strategy

Abstract

The rapid accumulation of retired lithium-ion batteries demands sustainable recycling technologies, particularly for lithium iron phosphate (LFP) cathodes, to alleviate resource constraints and curb environmental hazards posed by conventional disposal. Here, we propose a tunable pre-oxidization and microencapsulation strategy for the direct regeneration of unhomogenized spent LFP. Through controlled pre-oxidation, heterogeneous spent LFP is converted into a stoichiometric intermediate of Li₃Fe₂(PO₄)₃ and Fe₂O₃, resetting structural heterogeneity and removing binder/carbon residues. Polarity-modified encapsulation spatially confines Li₂CO₃/PVA (polyvinyl alcohol) around intermediates by non-solvent induced phase separation (NIPS), enabling uniform Li replenishment. Subsequently, annealing reconstructs the olivine lattice and concurrently generates an in situ carbon coating. The regenerated LFP exhibits restored crystallinity with Fe-Li antisite defects reduced from 6.1% to 1.41%, and a 5 nm in situ carbon coating, delivering a specific discharge capacity of 161 mAh g⁻¹ at 0.1 C with a ~30% reduction in polarization voltage, exhibiting 82% capacity retention over 1000 cycles at 2 C. This work establishes a facile pathway for LFP recycling by integrating defect correction with carbon coating in a scalable process, offering a viable solution to industrial battery reclamation and the circular economy.

Keywords

lattice remodeling oxidation / lithium iron phosphate regeneration / non-solvent induced phase separation

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