Sodium-Ion\nStorage in Na<sub>4</sub>VMn(PO<sub>4</sub>)<sub>3</sub>/C Porous\nNanorods Electrode

Na<sub>4</sub>VMn(PO<sub>4</sub>)<sub>3</sub> (NVMP) is a prospective\ncathode for sodium-ion batteries (SIBs) due to its low cost and extraordinary\nstructural stability. However, poor conductivity restricts the electrochemical\nperformance of NVMP, which limits its development and application.\nHerein, carbon-encapsulated NVMP porous nanorods are prepared via\na convenient electrospinning method. The prepared one-dimensional\n(1D) structure can effectively accelerate the transmission rate of\nelectrons, and the porous structure of NVMP/C nanorods can increase\nthe contact area between the electrolyte and electrode material, which\ncan enhance the diffusion rate of sodium ions. Owing to this advantageous\nnanoarchitecture, the obtained\nNVMP/C porous nanorods delivered an initial reversible capacity of\n90.9 mA h·g<sup>–1</sup> at 0.2 C and a discharge capacity\nof 68.0 mA h g<sup>–1</sup> at 5.0 C. NVMP/C can also achieve\na good cycling stability with ideal capacity retentions of 90.4% and\n89.8% after 800 cycles at 1 and 3 C, respectively. Moreover, even\nat a temperature of −30 °C at 0.3 C, the discharge capability\nwas up to 40.1% of that at 20 °C, suggesting an impressive low-temperature\ntolerance. In situ X-ray diffraction demonstrated that there was no\ncrystal distortion of the NVMP/C electrode during charge and discharge.\nThis work can provide a high-performance strategy on modification\nof polyanion-positive electrode materials for SIBs.