Direct regeneration of spent LiFePO4 cathode using a reduction agent of natural amino acid

In recent years, the recycling of spent lithium iron phosphate (LFP) batteries has garnered significant attention as an important strategy to alleviate resource scarcity and advance resource circularity. Among different recycling technologies for spent LFP batteries, emerging direct regeneration technology represents a sustainable recycling approach capable of restoring LFP cathode materials without compromising their olivine crystal structure. In our study, we proposed an environmentally friendly and efficient one-step hydrothermal regeneration strategy to achieve synergistic structural and functional restoration of spent LFP in the presence of lithium supplement. Lithium hydroxide (LiOH) serves as the lithium precursor, with the natural amino acid l -serine (C 3 H 7 NO 3 ) used as a green reducing agent. The primary alcohol group of l -serine can provide a reducing environment, enabling the reduction of Fe 3+ ions and alleviating the Li-Fe inversion defect. Concurrently, nitrogen atoms from the amino group of l -serine were incorporated into the carbon coating, enhancing the electrochemical performance of the material. Consequently, the regenerated LFP exhibited exceptional electrochemical property and outstanding cycling stability. The specific discharge capacity reached 140.6 mAh g −1 at 1C rate, demonstrating 86.13% capacity retention over 1000 cycles. Crucially, the material maintains a capacity retention of 84.44% over 1000 cycles even at a high rate of 5C. Such a strategy can effectively regenerate LFP cathode with a restored superior electrochemical property, offering a viable pathway for scalable recycling of spent LFP in the future.