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 Na 3 V 2 (PO 4 ) 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 Na 3 V 2 (PO 4 ) 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 Na 3 V 2 (PO 4 ) 3 /C composite with 5wt.% carbon exhibits the best electrochemical performance among the as-prepared three Na 3 V 2 (PO 4 ) 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.