Ultrafast Synthesis of High‐Purity LiMn x Fe 1‐x PO 4 With Locked‐Nanosize From Spent LiFePO 4

The impending wave of large‐scale spent LiFePO 4 (S‐LFP) batteries makes the recycling and reuse of their materials an urgent priority. However, materials recovered via existing direct regeneration methods suffer from inferior performance and low added‐value, which directly leads to poor economic viability and hinders the establishment of a closed‐loop recycling process. Herein, we propose an innovative upcycling strategy that directly converts S‐LFP into high‐voltage, high‐energy‐density LiMn x Fe 1−x PO 4 (LMFP) cathode via rapid thermal processing. This method simultaneously accomplishes structural repair and homogeneous Mn doping within seconds, effectively suppressing grain coarsening and lithium sources/carbon loss, and enabling the regeneration of a solid solution with precisely controlled composition. Consequently, the regenerated LMFP delivers a remarkable specific capacity of 161 mAh g −1 at 0.1C, exceptional cycling stability (98% capacity retention after 500 cycles at 1C), and superior rate capability (79% retention at 5C). Notably, this process slashes energy consumption by approximately 30%, to 19.09 MJ kg −1 and promises a high profit of USD 7.17 per kg feedstock, demonstrating both environmental and economic superiority. This work opens a new technical pathway for the low‐carbon and value‐added upcycling of spent LFP batteries.