Entropy Engineering Accelerating the Phase Transformation Dynamics of Phosphate Cathode for Ultra-High Rate...

NASICON-type Na_3.5V_1.5Mn_0.5(PO₄)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_3.5V_1.35Mn_0.5Al_0.05Ni_0.05Zr_0.05(PO₄)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.