N-doped carbon coated NaV3O8 cathodes towards high-capacity and ultrafast Na-ion storage.

In this work, nitrogen-doped carbon-coated NaV 3 O 8 (NVO@NC) were successfully synthesized by a simple rheological phase method using melamine as a nitrogen source. X-ray powder diffraction (XRD) and Scanning electron microscopy (SEM) analyses revealed that nitrogen-doped carbon-coated didn't change the crystal structure of NVO but altered the thickness and properties of the surface coating. Among obtained composites, NVO@NC containing a molar ratio of melamine to citric acid of 2.75:1.25 displayed the best electrochemical properties. The electrochemical tests suggested discharge capacity reaching 231.3 mAh g−1 at 150 mA g−1, with discharge capacity remaining at 169.4 mAh g−1 after 100 cycles. Electrochemical impedance spectroscopy (EIS) proved that the coated materials delivered a much lower resistance than that of bulk NVO. Galvanostatic intermittent titration technique (GITT) tests demonstrated sodium ion diffusion coefficient was greatly enhanced after nitrogen-doped carbon coating. In conclusion, nitrogen-doped carbon might increase material conductivity, aid in the formation of SEI films on electrode surfaces, and improve electrode material stability, resulting in NVO materials with high-capacity and ultrafast Na-ion storage. [ABSTRACT FROM AUTHOR]