Na3V2(PO4)3(NVP) is a promising cathode candidate for aqueous sodium-ion batteries (ASIBs), while the practical application of NVP is severely hindered by vanadium dissolution in aqueous electrolytes and electrochemical performance degradation. Herein, a high-entropy strategy was innovatively employed to synthesize Na3V1.0(Ti,Cr,Mn,Fe,Nb)1.0(PO4)3 (HE-NVP-1.0) cathode material via a facile sol-gel method. In situ X-ray diffraction confirms that high-entropy doping markedly alters the Na+ (de)intercalation mechanism, transforming the typical two-phase reaction between Na3V2(PO4)3 and Na1V2(PO4)3 into a continuous solid-solution reaction involving a series of stable intermediate phases, which effectively mitigates lattice strain and structural deterioration and results in a minimal unit cell volume change of merely 0.34% during cycling. Ex situ X-ray photoelectron spectroscopy elucidates the reversible valence transitions of V3+/V4+/V5+ and Mn2+/Mn3+ during charge/discharge, while Cr3+, Ti4+, and Nb5+ remain electrochemically inactive, constituting a stable lattice skeleton. Consequently, HE-NVP-1.0 delivers a reversible specific capacity of 56.2 mA h g-1 at 0.1 A g-1, exhibits an excellent rate capability of 80.7% at 5.0 A g-1, and retains 91.4% of its capacity after 5000 cycles. This work not only provides a novel high-entropy modification strategy to address vanadium dissolution in NVP but also opens new avenues for performance optimization of polyanion-type energy storage materials.
Luo et al. (Wed,) studied this question.