High-loading electrodes are particularly crucial for the practical application of Na-ion batteries (NIBs) in large-scale energy storage systems. To enable high-power long-lifetime NIBs, cathode materials with rapid Na-ion diffusion and structural stability must be developed. In this study, a novel vanadium-based phosphate heterostructure cathode material of Na8V5(P2O7)2.925(PO4)3.75 (N8VPP) was synthesized by the spray-drying method with a unique dual-phase heterostructure comprising Na7V4(P2O7)4(PO4) and Na3V2(PO4)3 in a molar ratio of 0.725:1. The P2O74-/PO43- polyanionic hybrid heterostructure shows a pronounced increase in the number of electronic states near the Fermi level. This resulting electronic feature lowers the Na+ migration energy barrier and promotes charge transfer, as confirmed by density functional theory (DFT) calculations. Under high-loading conditions (10 mg cm-2), the N8VPP cathode delivers remarkable capacities of 90.51 mAh g-1 and 41.88 mAh g-1 at 0.1 A g-1 and 10 A g-1, respectively. Additionally, the capacity retention ratio is 71.8% with 64.3 mAh g-1 after 1000 cycles at 2 A g-1, demonstrating excellent cycling stability and power capability. Furthermore, a Na-ion full battery of N8VPP//NaTi2(PO4)3 achieves an excellent capacity and outstanding cycling life of 73 mAh g-1 at 5 A g-1 and 3000 cycles at 2 A g-1, respectively. This study offers key design insights for high-performance N8VPP cathodes toward practical sodium-ion energy storage.
Pi et al. (Sun,) studied this question.