Na3V2(PO4)3 coated by N-doped carbon from ionic liquid as cathode materials for high rate and long-life Na-ion batteries

Abstract

A facile and simple hydrothermal assisted sol–gel route was developed to prepare nitrogen doped carbon coated Na₃V₂(PO₄)₃ nanocomposites (denoted as NVP@C–N) as cathodes for sodium ion batteries (NIBs). An ionic liquid (EMIm-dca) was used as the nitrogen doped carbon source. The optimized N-doped carbon coated Na₃V₂(PO₄)₃ (denoted as NVP@C–N150) displays a very thin and uniform N-doped carbon coating layer (thickness: ∼2 nm), showing an excellent sodium storage performance (85 mA h g⁻¹ at 20 C after 5000 cycles) and high rate capability (71 mA h g⁻¹ at 80 C). Such a superior sodium storage performance derives from the nitrogen doping carbon coating, triggering amounts of extrinsical defects and active sites in the N-doped amorphous carbon layer, which highly accelerates Na-ion and electron transport. This approach is simple, facile and shows easy scale-up. It could be extended to other materials for energy storage.