Lijuan Luo, Tinghong Gao, Jiayao Chen, T Guo, Wensheng Yang, Q XIE, Yunjun Ruan
Na 3 V 2 (PO 4 ) 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 Na 3 V 1.0 (Ti,Cr,Mn,Fe,Nb) 1.0 (PO 4 ) 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 Na 3 V 2 (PO 4 ) 3 and Na 1 V 2 (PO 4 ) 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 V 3+ /V 4+ /V 5+ and Mn 2+ /Mn 3+ during charge/discharge, while Cr 3+, Ti 4+, and Nb 5+ 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.