Emerging intertwined nanofibers stabilized two-dimensional sodium vanadium pyrophosphate network for high-potential electrode in sodium-ion storage

Metal pyrophosphates compounds with high conductivity and excellent redox properties are promising electrode materials for sustainable energy storage. So, the binder-free 1D stacked 2D Na₇V₃(P₂O₇)₄ (NVPO) nanosheets were grown on a carbon fiber cloth (C) (NVPO@C) through a two-step hydrothermal process followed by phosphorization under controlled atmospheric conditions. The binder-free 350-NVPO@C electrode exhibits an emergent architecture of intertwined nanofibers stabilizing over 2D enlarged nanosheets, providing enhanced ion transport pathways, improved conductivity, and expanded electroactive areas to boost sodium ion storage efficiency. It achieves a maximum gravimetric capacitance of 362 F g⁻¹ (257 F cm⁻³) at 4 A g⁻¹ with an excellent rate capability of ~76 % in a 1 M NaClO₄/acetonitrile. Theoretical calculations suggest that (P₂O₇)⁴⁻ plays a vital role in enhancing structural stability, facilitating ion diffusion, modifying the electronic structure, and boosting the adsorption energy of Na⁺. A 350-NVPO@C-based symmetric device with a broad electrochemical voltage of 2 V, delivering a maximal gravimetric energy density of 39 Wh kg⁻¹ (25.5 Wh cm⁻³) at a minimal gravimetric power density of 2005 W kg⁻¹ (1311 W cm⁻³), while maintaining an excellent capacity retention of ~89 % over 10,000 consecutive GCDs at 5 A g⁻¹. These findings highlight NVPO@C nanosheets as highly efficient electrodes for next-generation energy storage.