Gradient Mg and Uniform Ti Co‐Doping Suppresses Jahn–Teller Effect in LMFP via Optimized Ion‐Transport Kinetics and Interfacial Reactions

ABSTRACT

LiMn _0.6 Fe _0.4 PO ₄ (LMFP), an olivine‐type cathode material, is gaining attention in high‐energy‐density lithium‐ion batteries due to its high operating voltage and cost‐effectiveness. However, its practical use is limited by slow Li ⁺ diffusion, poor electronic conductivity, and structural degradation caused by Jahn–Teller distortion from Mn ³⁺ . To tackle these challenges, we have developed a dry‐and‐wet synthesis method to produce Mg/Ti co‐doped LMFP (Mg/Ti‐LMFP). This approach ensures uniform Ti ⁴⁺ doping at Fe sites and gradient Mg ²⁺ doping at Li sites. Ti ⁴⁺ strengthens the structural stability by forming M─O bonds, reducing Jahn–Teller distortion. Additionally, surface‐enriched Mg ²⁺ creates a protective layer, preventing manganese dissolution and electrolyte decomposition. The optimized structure and chemistry enhance Li ⁺ transport kinetics, stability, electronic conductivity, and cycling durability. Mg/Ti‐LMFP demonstrates 88.7% capacity retention after 200 cycles at 1C (25°C) and 88.2% after 100 cycles at 1C (55°C). This study lays a solid foundation for designing high‐performance co‐doped olivine‐type cathode materials, guiding the development of future energy storage solutions.