Entropy Engineering Accelerating the Phase Transformation Dynamics of Phosphate Cathode for Ultra‐High Rate Capability

Abstract NASICON‐type Na 3.5 V 1.5 Mn 0.5 (PO 4 ) 3 (NVMP) is a cost‐effective cathode candidate for sodium‐ion batteries (SIBs). Nevertheless, its practical deployment is hindered by sluggish reaction kinetics and severe structural degradation. Herein, by incorporating synergistic dopants (Al, Ni, Zr) into transition metal sites, a Na 3.5 V 1.35 Mn 0.5 Al 0.05 Ni 0.05 Zr 0.05 (PO 4 ) 3 /C (NVMANZP) is constructed. This multi‐cation substitution increases configurational entropy, fundamentally altering the inherent biphasic reaction (in pristine NVMP) to a predominantly solid‐solution‐like mechanism in NVMANZP, which reduces the Na + migration barrier and accelerates reaction kinetics. Moreover, this entropy‐stabilized mechanism minimizes Jahn–Teller lattice strain, enhancing cycling stability. Consequently, NVMANZP delivers 118.3 mAh g −1 at 0.2C (1C = 110 mA g −1 ), retains 77.3 mAh g −1 at 100C (vs. 52.4 mAh g −1 for pristine), and maintains 80.76% capacity retention after 4,000 cycles at 10C. The full cell achieves 378 Wh kg −1 at 0.2C (based on mass of cathode). This work establishes NVMANZP as a high‐rate, long‐life SIB cathode and reveals how entropy‐driven mechanisms tailor NASICON reaction kinetics.