High-Power and Long-Lifetime Na-Ion Batteries Enabled by High-Loading Vanadium-Based Phosphate Heterostructure Cathodes

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 Na 8 V 5 (P 2 O 7 ) 2.925 (PO 4 ) 3.75 (N 8 VPP) was synthesized by the spray-drying method with a unique dual-phase heterostructure comprising Na 7 V 4 (P 2 O 7 ) 4 (PO 4 ) and Na 3 V 2 (PO 4 ) 3 in a molar ratio of 0.725:1. The P 2 O 7 4– /PO 4 3– 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 N 8 VPP 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 N 8 VPP//NaTi 2 (PO 4 ) 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 N 8 VPP cathodes toward practical sodium-ion energy storage.