Direct hydrothermal regeneration and high value-added utilization of spent lithium iron phosphate for priority lithium extraction from acidic leachate.

To address the global lithium shortage, direct regeneration of degraded cathodes via lattice reconstruction offers an eco-efficient strategy for recycling spent lithium-ion batteries (LIBs). However, industrial adoption is hindered by residual defects and insufficient lithium replenishment. Here, we propose a groundbreaking high-value reuse pathway, repurposing regenerated lithium iron phosphate (LFP) as an acid-stable adsorbent for priority lithium extraction from acidic leachate. Thermodynamic and electrochemical analyses suggested the stronger reductant facilitate the lattice reconstruction. The regenerated LFP, processed via a 2-hour hydrothermal repair at 220 °C using ascorbic acid, exhibited an exceptional lithium extraction capacity of 38.5 mg/g without electrode dissolution, selectively reducing residual lithium to < 20 ppm. By simultaneously enabling high-value utilization of spent LFP and priority lithium extraction, this paradigm bridges economic viability with circular economy principles, offering a blueprint for upcycling spent LIB materials.