Upcycling Spent LiMn 2 O 4 into High‐Performance LiMn x Fe 1‐ x PO 4 Cathodes Via Synergistic Leaching Followed by Direct Regeneration

ABSTRACT Improper disposal of spent lithium‐ion batteries causes environmental pollution and resource waste. Conventional recycling of low‐cost LiMn 2 O 4 (LMO) involves complex, multi‐step processes including leaching, extraction, separation, precipitation and resynthesis, leading to poor environmental and economic viability. Herein, a novel upcycling strategy is proposed, where spent LMO is directly converted into high‐performance LiMn x Fe 1‐ x PO 4 (LMFP) cathodes through a H 3 PO 4 ‐ascorbic acid synergistic leaching followed by direct regeneration. Concretely, H 3 PO 4 serves as both a leaching agent and phosphorus source, while ascorbic acid acts as an auxiliary leaching agent with reducing and complexing capabilities. Their synergistic action ensures efficient Li/Mn leaching, and the resulted leached solution is subjected to solvothermal synthesis followed by calcination to upcycle olivine‐structured LMFP. By introducing Macrogol 400 as a surfactant, the uniformity of the Fe–Mn precursor is improved, and a 3D conductive carbon network is constructed to accelerate the transportation of lithium‐ion and electron. Consequently, the regenerated LMFP exhibits outstanding electrochemical performance, achieving a specific discharge capacity of 140.72 mAh g −1 at 1 C and 87.31% capacity retention after 1000 cycles. Economic assessment reveals a profit of 4.850$ kg −1 of spent LMO. This study provides a new approach for the green and short upcycling of spent cathode materials.