Novel Upcycling of Mixed Spent Cathodes Toward High Energy Density LiMn_xFe_1−XPO₄ Cathode Material

Abstract Sustainable recycling of lithium‐ion batteries (LIBs) is essential for resource conservation and supporting the development of renewable energy. However, the conventional recycling approaches face significant challenges due to the mismatch between the limited energy density of regenerated batteries and the increasing demand for high‐performance LIBs, necessitating a shift toward upcycling strategies. Herein, an innovative upcycling strategy is demonstrated that transforms mixed spent LiFePO₄ (LFP) and LiMn₂O₄ cathodes into high‐performance cathode materials. Through advanced methodologies for reaction pathway control and rational design of metal coordination complexes, spent lithium‐ion batteries are recovered and converted into a solid solution characterized by homogeneously distributed manganese and iron elements. The regenerated LiMn_0.6Fe_0.4PO₄ cathode material, fabricated using this solid solution as a precursor, delivers a remarkable discharge capacity of 160.7 mA g⁻¹ at 0.2C and retains an impressive 93.1% capacity retention after 500 cycles at 1C. The LiMn_0.6Fe_0.4PO₄ (3.85 V vs Li⁺/Li and 558.9 Wh kg⁻¹) achieves a significant voltage increase of 0.49 V and a 19.7% enhancement in energy density compared to commercial LFP (3.36 V vs Li⁺/Li and 466.8 Wh kg⁻¹). This strategy offers a sustainable pathway for both the recycling of mixed spent lithium‐ion batteries and the production of high energy density cathode materials.