Selective Interfacial Repair Enables Low‐Energy Regeneration of Spent LiFePO 4 to High‐Performance Cathode

ABSTRACT Recycling degraded LiFePO 4 (LFP) cathodes via conventional pyro‐(pyrometallurgy) or hydro‐ (hydrometallurgy) is energy‐intensive, generates toxic emissions, and yields meagre profits. Here, we report a low‐energy oxidation‐reduction (O‐R) strategy that bypasses element separation: air pre‐oxidation (500°C) removes carbon/binder, converting lithium‐deficient olivine into Li 3 Fe 2 (PO 4 ) 3 /Fe 2 O 3 intermediates; hydrothermal treatment with ascorbic acid enables selective Fe 3+ reduction (adsorption energy −2.98 eV) and concurrent Li + replenishment. This reconstructs the lattice, halves Fe‐Li antisite defects (4.38% to 2.00%) and lowers Li + migration activation energy to 54.48 kJ mol −1 . Regenerated OR‐LFP delivers an initial capacity of 155.7 mAh g −1 at 0.1 C and 147.1 mAh g −1 at 1 C, retains 94.5% capacity after 500 cycles at 1 C and 93.8% at 5 C, and shows superior rate capability. Technology‐economic analysis reveals O‐R requires only 5.87 MJ kg −1 (less than half the energy of hydro‐ or pyro‐) and yields ≈$0.80 kg −1 profit, over tenfold higher than conventional routes, with minimal CO 2 emission. The process uses existing hydrothermal reactors and moderate‐temperature furnaces, enabling feasible industrial scaling. This work bridges high‐performance cathode regeneration with circular‐economy viability for sustainable LIB recycling.