Dual-Nitrogen-Doped Carbon Decorated on Na₃V₂(PO₄)₃ to Stabilize the Intercalation of Three Sodium Ions

Abstract

NASICON-type Na3V2(PO4)3 (NVP) has been regarded as one of the most promising cathode materials for high-voltage sodium-ion batteries (SIBs) because of its high theoretical energy density and stable crystal structure. However, NVP suffers from low electronic conductivity, limiting the utilization of the active material and hampering its rate performance. Herein, a facile one-pot synthesis to construct dual-nitrogen-doped carbon decorated on NVP is proposed to improve the cyclic stability and capacity of NVP. In addition, the pyrolysis of urea at high temperatures produces volatile materials that expand the reduced graphene oxide (rGO) mechanically while doping nitrogen into the carbon layer, creating defects in the carbon layer. Consequently, NVP@C/rGO-U delivers 107, 101, and 87 mAh g–1 at 1C, 5C, and 25C, respectively, and 91% capacity retention after 500 cycles at 5C. Furthermore, even at a higher mass loading, it can still deliver 96 mAh g–1 at 5C with good capacity retention, implying its outstanding electrochemical properties. Additionally, NVP@C/rGO-U shows excellent structure stability and delivers 162 mAh g–1 at 1C when the voltage window increases to 1–4 V. The facile synthesis method provides an alternative insight into industrial production of high-energy-density SIBs with superior fast-charging properties.