Sustainable FeOCl-driven interfacial reconstruction for upcycling spent graphite anodes

The accelerating deployment of lithium-ion batteries (LIBs) has triggered a massive influx of spent cells. Recycling spent graphite from end-of-life LIBs is imperative for mitigating environmental burdens, averting safety hazards, securing a sustainable supply of critical materials, and significantly reducing the carbon footprint across the entire industry chain through full-lifecycle reuse. Herein, we report for the first time a facile, eco-friendly, and cost-effective upcycling strategy that achieves synchronous deep purification and in situ interfacial engineering of spent graphite anodes using a FeCl 3 -ethylene glycol-based deep eutectic solvent. This dual-functional process effectively eliminates recalcitrant impurities, including PVDF binders and SEI components, while simultaneously anchoring flower-like FeOCl nanocrystal clusters onto the graphite surface. Mechanistically, this engineered architecture unlocks a synergistic three-fold effect: (i) the expanded graphite interlayer spacing significantly lowers the energy barrier for rapid Li + diffusion kinetics; (ii) the anchored FeOCl clusters serve as highly active species, providing abundant extra sites for multi-electron reaction capacity; and (iii) the robust graphite skeleton effectively mitigates the structural strain arising from Li + intercalation over prolonged cycling, ensuring structural integrity. Consequently, the upcycled graphite (FG-3) demonstrates exceptional electrochemical performance, delivering a high discharge capacity of 418 mAh g −1 , which notably exceeds the theoretical limit of pristine graphite (372 mAh g −1 ). Furthermore, it exhibits a robust capacity retention of 96.5% following a 100-cycle endurance test under 0.1 A g −1 . This work provides a sustainable and practical avenue for regenerating spent graphite, offering profound economic, strategic, and environmental value toward a net-zero, low-carbon battery lifecycle.