High‐Entropy Doping Strategy Enabling LiMn 0.8 Fe 0.2 PO 4 Cathode with High‐Rate Capability and Long Cycle Life for Lithium‐Ion Batteries

Lithium iron manganese phosphate (LiMn 0.8 Fe 0.2 PO 4 , LMFP) cathode for lithium‐ion batteries (LIBs) shows great potential in terms of safety, power density, and cost‐effectiveness. However, the inherent Jahn–Teller distortion, phase transformation stress, and active Mn dissolution lead to poor rate capability and cycle stability. To tackle these formidable issues, we herein pioneer the integration of the high‐entropy (HE) concept into the olivine‐type LMFP framework and successfully develop a multication synergistically doped cathode, i.e., LiMn 0.7 Ni 0.02 Cu 0.02 Ca 0.02 Zn 0.02 Mg 0.02 Fe 0.2 PO 4 (denoted as HE‐LMFP), via a scalable solid‐state synthesis method. Thanks to the integrated advantages from HE‐doping and conductive carbon coating, HE‐LMFP is endowed with a robust lattice structure with enhanced lithium‐ion diffusion kinetics, preventing detrimental Jahn–Teller distortion inherent to Mn 3+ , reducing charge‐transfer resistance, and mitigating active Mn loss. Accordingly, our HE‐LMFP demonstrates enhanced electrochemical properties, particularly in terms of higher initial reversible capacity (154.5 mAh g −1 at 0.1 C), prolonged cycling stability (98.4% capacity retention after 350 cycles at 1 C), and excellent high‐rate capability (101.2 mAh g −1 at 10 C). This work establishes a feasible HE doping strategy to develop high‐rate, long‐life LMFP cathodes, offering new insights for advancing high‐energy‐density LIBs.