Closed-loop upcycling of residual lithium in LiFePO4 into tunable thin lithium metal electrodes

Abstract With the rapid development of electric vehicles, massive quantities of spent lithium iron phosphate batteries are generated, creating an urgent demand for efficient and sustainable recycling. Here we show a redox mediator-assisted strategy that directly converts simulated spent lithium iron phosphate powder into thin lithium metal, reducing energy requirements and enabling regeneration of the redox mediator. The process achieves a 98% final lithium extraction and produces lithium foils with a preformed interphase, tolerating volume changes and resisting air corrosion. The recycled Li (4.14 mAh cm −2 ) enables Li | |Li cells to cycle over 1,200 h at the test condition of 1 mA cm −2 / 1 mAh cm −2 and shows stable interfacial resistance with reduced electrolyte decomposition. When paired with NCM811, the cells retain 91.4% capacity over 400 cycles at 0.2 C/0.3 C. This closed-loop process couples lithium recovery with designed electrode fabrication, providing an alternative pathway for sustainable battery recycling and negative electrode design.