Effects of nitrogen doping on the structure and performance of carbon coated Na3V2(PO4)3 cathodes for sodium-ion batteries

Na3V2(PO4)3 (NVP) is a promising cathode material for sodium ion batteries due to the good electrochemical performance in terms of cycling stability and rate capability. However, in order to access this performance a carbon coating is required to enhance the intrinsically poor material's conductivity. Herein, we systematically investigate the role of N-doped carbon (NC) coatings on both the structural and electrochemical properties of NVP materials. NC-coated NVP materials with various nitrogen contents have been rationally synthesized by a novel solid-state method allowing the selective N-doping of the carbon coating. In fact, the N-doping changes the disorder and graphitic character of the carbon layer, strongly impacting the electrochemical performance of the NVP/C composite materials. Results suggest that the appropriate N-doping amount of the carbon leads to highly decreased electrode polarization and excellent cycling stability at high rate, enabling the NVP materials with high energy and power efficiencies.