Overcoming secondary thermal damage in spent LiFePO4 regeneration via interface-selective lithium anchoring

Thermal pretreatment is a key step for purifying spent LiFePO 4 (LFP) cathode materials by removing surface residues, but the microstructural damage in the spent LFP powder has been rarely studied. In this work, we found that thermal pretreatment inflicts severe secondary damage by forming inert Fe 2 P 2 O 7 phases and introducing a large number of Fe/Li antisite defects; this damage is further confirmed as the root cause of the intrinsic failure of conventional lithium-replenishment strategies in LFP regeneration. To eliminate the thermal damage induced by pretreatment, an interface-selective lithium anchoring (ISLA) strategy is proposed based on the newly identified mechanism. The ISLA strategy constructs functionalized interfaces in which abundant functional groups act as selective sites to anchor and disperse lithium, thereby enabling in situ reconversion of Fe 2 P 2 O 7 to LiFePO 4 and effective reduction of Fe/Li antisite defects. The regenerated LFP exhibits high-rate capability, delivering 121.8 mA h g -1 at 10 C, and excellent cycling stability, retaining 72.7% of its capacity after 1500 cycles. This work provides a scalable and sustainable route for regenerating spent LFP cathode materials with reduced energy demand and carbon footprint.