Homogeneous Spinel FeMn 2 O 4 Precursor Enables LiMn 0.67 Fe 0.33 PO 4 as Durable High‐Rate Lithium‐ion Cathode

ABSTRACT Lithium manganese iron phosphate (LiMn x Fe 1‐ x PO 4 , LMFP) offers higher energy density than LiFePO 4 but suffers from sluggish kinetics and unfavorable cycling stability caused by Fe/Mn segregation and severe Jahn‐Teller distortion of Mn 3+ . Herein, a precursor‐engineered strategy is proposed using a homogeneous spinel FeMn 2 O 4 precursor synthesized via solution combustion. Molecular‐level chelation and rapid combustion pre‐lock Fe and Mn cations into a uniform solid‐solution framework, enabling the formation of LiMn 0.67 Fe 0.33 PO 4 with highly homogeneous cation distribution and reduced lattice distortion. As a result, the LMFP cathode exhibits markedly reduced polarization (38 mV and 101 mV for Fe and Mn plateaus), enhanced Li + diffusion coefficients (up to 6.75 × 10 −12 cm 2 s −1 ), and excellent rate capability, delivering ∼76 mAh g −1 at 10 C. Superior cycling stability is achieved with 89.2% capacity retention after 1000 cycles at 5 C. This work demonstrates precursor‐level cation organization as an effective route to overcoming the kinetic and stability bottlenecks of manganese‐based olivine cathodes.