Universal and Normalized Regeneration of Heterogeneous Spent <scp>L</scp> i <scp>F</scp> e <scp>PO</scp> ₄ via Mechanochemical Delithiation and Flash Relithiation

The global surging demand for lithium iron phosphate batteries necessitates efficient recycling strategies to ensure environmental sustainability and resource conservation. While direct regeneration is considered sustainable, its widespread adoption is hindered by three critical challenges: 1) heterogeneous and unquantifiable lithium loss across waste streams, 2) abnormal particle growth during high‐temperature restoration, and 3) limited economic returns arising from the low‐value elements and complex process. Here, we report a universal and scalable “ x → 0 → 1” normalization strategy. All spent Li x FePO 4 is first reset to Li‐free olivine FePO 4 ( x → 0) via mechanochemical delithiation, eliminating batch‐specific variability. Benefiting from the olivine FePO 4 with pre‐existing Li + diffusion channels and nonequilibrium kinetics, subsequent ultrafast heating resynthesis (UHR) restores stoichiometric lithium iron phosphate (0 → 1) in just 35 s, effectively suppressing particle coarsening while cutting energy/time consumption by &gt;99% compared to furnace sintering. This approach accommodates diverse degradation levels and their mixture, yielding regenerated lithium iron phosphate with consistent capacity, superior rate capability (84.3 mAh g −1 at 10 C) and cycling stability (89.1% retention after 1000 cycles at 10 C), outperforming fresh commercial lithium iron phosphate (73.3 mAh g −1 , 66.6%). Beyond regeneration, flash upcycling to lithium manganese iron phosphate further enhances energy density to 549 Wh kg −1 . Techno‐economic analysis confirms strong profitability (lithium iron phosphate: 4.86 $ kg −1 cell, lithium manganese iron phosphate: 10.98 $ kg −1 cell), low energy demand (6.56 MJ kg −1 cell), and reduced emissions (2.95 kg CO 2 ‐eq kg −1 cell). Our strategy therefore establishes a general and robust platform for closed‐loop cathode recycling and upcycling.