Na3V2(PO4)3/C nanocomposites are synthesized by an oleic acid-based surfactant-assisted method. XRD patterns reveal high-purity samples, whereas Raman spectroscopy evidence the highly disordered character of the carbon phase. Electron micrographs show submicron agglomerates with a sea-urchin like morphology consisting of primary nanorods coated by a carbon phase. The electrode material was tested in half and full sodium cells. The electrochemical performance is clearly improved by this optimized morphology, particularly at high C rates. Thus, 76.6 mA h g(-1) was reached at 40C for Na3V2(PO4)3/C nanorods. In addition, 105.3 and 96.7 mA h g(-1) are kept after 100 cycles at rates as high as 5 and 10C. This exceptional Coulombic efficiency can be ascribed to the good mechanical stability and the low internal impedance at the electrode-electrolyte interphase.
Keywords: NASICON; oleic; phosphate; sodium-ion batteries; surfactant.