Entropy‐Regulated LiMn _x Fe _{1‐ x} PO ₄ Cathode for Superior High‐Temperature Cycling

ABSTRACT LiMn _x Fe _{1‐ x} PO ₄ (LMFP) is a promising high‐energy‐density, cost‐effective, and safe cathode for lithium‐ion batteries. However, its practical application is hindered by intrinsic limitations, including low electronic/ionic conductivity, Jahn‐Teller distortion, and Mn dissolution, which become more severe at high temperatures. To overcome these challenges, we propose a novel configurational entropy (CE) regulation strategy, synthesizing a Li(Mn _0.6 Fe _0.4 ) _0.97 (MgCoNi) _0.03 PO ₄ /C (CE‐LMFP/C) composite. The multi‐cation incorporation of Mg ²⁺ , Co ²⁺ , and Ni ²⁺ effectively increases the configurational entropy of the system and profoundly enhances charge transfer kinetics. Crucially, it effectively suppresses Jahn‐Teller distortion and Mn dissolution by strengthening Mn─O bonding and regulating the charge compensation mechanism. Furthermore, this strategy promotes a phase transition characterized by an extended solid‐solution region and reduced unit cell volume change. Consequently, CE‐LMFP/C delivers an impressive discharge capacity of 151.84 mAh g ⁻¹ at 0.2 C and maintains 134.14 mAh g ⁻¹ at an ultra‐high rate of 20 C. Remarkably, it exhibits outstanding stability under demanding conditions, retaining 82.64% of its initial capacity and 75.33% of its initial energy density after 400 cycles at 50°C. Detailed kinetics analysis and post‐cycling characterization confirm rapid Li ⁺ diffusion and exceptional structural integrity. This configurational entropy approach provides a powerful and novel pathway for designing high‐performance Mn‐based polyanionic cathodes.