High-speed homogenization and fluorine surface modification enable direct regeneration of spent LiFePO4 cathodes with enhanced cycling stability

Direct regeneration of spent LiFePO 4 (LFP) cathodes faces two critical challenges: inhomogeneous contact between repair agents and degraded particles, and insufficient cycling stability of regenerated materials. Here, we address both issues through a two-step powder-level regeneration strategy combining high-speed slurry homogenization with fluorine-source treatment. The spent LFP powder, comprising mixed LiFePO 4 and FePO 4 phases, is fully restored to phase-pure olivine LiFePO 4 after thermal annealing. Replacing conventional stirring with high-speed homogenization significantly improves the distribution of LiOH·H 2 O and melamine precursors around LFP particles, boosting the initial discharge capacity from 135.88 to 152.38 mAh·g −1 at 0.1C. Subsequent fluorine treatment using LiF or NH 4 F introduces uniformly distributed fluorine species on particle surfaces, as confirmed by SEM-EDS mapping. Although fluorination slightly reduces the initial capacity (to ∼142 mAh·g −1 ), it substantially enhances long-term cycling stability, with capacity retention at 1C after 400 cycles increasing from 87.74% for the non-fluorinated sample to 93.85% for LiF-RLFP and 92.63% for NH 4 F-RLFP. The fluorine-treated materials retain ∼90% capacity after 100 cycles in LFP||graphite full cells, while further analyses indicate improved kinetics and reduced accumulation of electrolyte-derived interfacial species. This work offered a simple and scalable route for spent LFP direct regeneration.