Porous spherical Na3V2 (PO4)3/C composites synthesized via a spray drying -assisted process with high-rate performance as cathode materials for sodium-ion batteries

Porous spherical Na3V2(PO4)3/C composites were synthesized by a spray drying-assisted approach combined with microwave calcinations, and then characterized as cathode materials for sodium-ion batteries. The effect of carbon content on Na3V2 (PO4)3/C were investigated by X-ray diffraction, scanning electron microscopy, Brunauer-Emmet-Teller method, charge-discharge test, cyclic voltammetry and electrochemical impedance spectra measurements. The results demonstrate that the Na3V2(PO4)3/C composite with 5wt.% carbon exhibits the best electrochemical performance among the as-prepared three Na3V2 (PO4)3/C samples. It delivers the discharge capacity of 97.9 mAh g− 1, 93.5 mAh g− 1 at 0.2 C and 5 C, respectively. Furthermore, 97.9% of its initial capacity is remained after 500 cycles at a high rate of 5 C. The superior electrochemical performance can be ascribed to the improvement of electronic and ionic conductivity by carbon coating and porous spherical structure.