Entropy-enhanced multi-cation engineering of Na3V2(PO4)3 cathodes for accelerated sodium-ion transport and high-rate performance

Na 3 V 2 (PO 4 ) 3 (NVP) is a promising cathode material for NIBs because of its robust sodium (Na) super ionic conductor (NASICON) framework and relatively high theoretical capacity. However, the toxicity of vanadium and the limited versatility of single-cation redox chemistry have motivated compositional modification strategies to create more flexible local environments for Na + storage and transport. In this study, multi-cation substitution of Fe, Mn, and Ti at the V sites is achieved through a spray pyrolysis method, which enables homogeneous multi-element mixing at the precursor level. This uniform compositional distribution introduces entropy-enhanced local coordination environments, inducing local charge redistribution and broadened valence characteristics that modulate the Na-site energetics and facilitate Na + diffusion kinetics. As a result, the multi-cation-substituted Na 3 V 1 Fe 0.5 Mn 0.25 Ti 0.25 (PO 4 ) 3 (NVFMTP) cathode exhibits excellent cycling stability, delivering a discharge capacity of 85.3 mA h g −1 over 1000 cycles at 1.0C. Compared with Na 3 V 1 Fe 1 (PO 4 ) 3 and Na 3 V 1 Fe 0.5 Mn 0.5 (PO 4 ) 3 , NVFMTP demonstrates superior Na + transport behavior, retaining 69.6% capacity of its capacity at 20C, while maintaining high Na + diffusion coefficients and structural integrity. Furthermore, in situ XRD and DFT analyses demonstrate that entropy-driven compositional disorder induces a solid-solution-type reaction mechanism and band gap narrowing, providing fundamental insights into enhanced Na + transport kinetics.