Na3V(OH)(HPO4)(PO4): a novel cathode candidate for sodium-ion batteries

In the field of electrochemical energy storage, polyanionic compounds exhibit outstanding electrochemical performance owing to their stable crystal structures and tunable operating potentials. Among these, vanadium-based phosphates stand out and have been extensively investigated. In this work, a novel polyanionic compound, Na 3 V(OH)(HPO 4 )(PO 4 ), was synthesized by a simple one-step hydrothermal method. Its crystal structure, confirmed by Rietveld refinement of the X-ray diffraction data, can accommodate sodium ions and provide open interstitial pathways to facilitate Na + diffusion, suggesting its potential as a cathode material for sodium-ion batteries (SIBs). Bond valence sum analysis and density functional theory calculations further validated the high Na + ion transport efficiency within the framework. Based on these findings, a half-cell was assembled using the as-prepared material as the cathode and metallic sodium as the anode. Electrochemical tests demonstrated excellent reversible cycling stability and rate capability, underscoring the promise of Na 3 V(OH)(HPO 4 )(PO 4 ) as a high-performance cathode candidate for SIBs.