Sustainable Transformation of Spent LiFePO4 Cathodes into High-Voltage Olivine LiMnxFe1-xPO4 via Solvothermal Upcycling Strategy for Next-Generation Cathode Material

With the retirement of a large number of lithium-ion batteries, how to efficiently recycle cathodes, especially for spent LiFePO₄ (S-LFP) olivine materials with low content of valuable elements, has become a research focus. Moreover, upcycling S-LFP to high-voltage olivine LiMn_xFe_1-xPO₄ (LMFP) is crucial for advancing next-generation cathode materials. Herein, this study proposes a solvothermal upcycling strategy that achieves complete elemental recovery and converts S-LFP into high-voltage LMFP. The resulting LMFP exhibits a uniform elemental distribution, attributed to the atomic-level miscibility of Fe and Mn. As a result, the regenerated LMn_0.5Fe_0.5PO₄ exhibits remarkable cycle stability with 83.8% capacity retention after 2500 cycles at 5 C and a 40% improvement in energy density (561 Wh kg^-1) over that of S-LFP (402 Wh kg^-1). This study presents an effective, direct upcycling route for the large-scale production of next-generation, high-performance olivine cathode materials while achieving sustainable reutilization of S-LFP through closed-loop life cycle management.