Radical Anion-Driven Electron-Ion Coupled Repair Chemistry for Direct Regeneration of Degraded LiFePO₄ Cathodes

Direct regeneration of spent LiFePO₄ (LFP) cathodes is a sustainable alternative to conventional recycling methods. However, poor remediation efficiency and complex processes limit its application. Here, we develop a room-temperature liquid-phase strategy based on a deep green lithium naphthalenide (Li-Naph) solution. This strategy utilizes radical anion-driven electron-ion coupling remediation chemistry to integrate electron donors, lithium transport, and surface reconstruction within a single solution-phase platform. The strongly reducing naphthalene radical anion enables spontaneous electron transfer at ambient conditions, efficiently converting Fe³⁺ back to Fe²⁺, while promoting surface lithium enrichment through coupled electron-ion interactions. Subsequent annealing allows the enriched lithium to diffuse into lithium vacancies, while the organic residues undergo in situ carbonization into a conformal conductive shell, achieving synergistic bulk repair and surface reconstruction. This chemistry fully restores the olivine framework, suppresses Fe-Li anti-site defects, and markedly enhances Li⁺ transport kinetics. The regenerated cathode delivers a high initial capacity of 140.1 mAh g^-1 and retains 92% capacity after 650 cycles at 1C, even maintaining excellent stability at a high rate of 5C. Importantly, the strategy remains effective for severely degraded cathodes, highlighting the broad applicability of radical-anion-driven repair chemistry.