A hybrid material of vanadium nitride and nitrogen-doped graphene for lithium storage

Abstract

Vanadium nitride and nitrogen-doped graphene nanosheet (G) hybrid materials were prepared by a facile sol–gel method combined with a thermal treatment at 800 °C under ammonia atmosphere. It was found that VN nanoparticles adhered to the surface of nitrogen-doped graphene nanosheets and/or were embedded in the graphene layers of the hybrid material (VN-G). This nanostructured material promises an efficient electronic and ionic conducting network, which exhibits dramatically increased specific capacities after rate capability test in comparison to the original value under the same current density. The most probable explanations for these distinct characteristics are deduced from observations by advanced transmission electron microscopy together with X-ray diffraction and electron energy-loss spectroscopy, which illustrate a gradual activation of nitride during lithiation/delithiation processes, owing to slow kinetics of VN reaction with lithium. The electrochemical results demonstrate that the weight ratio of VN to G has a significant effect on the performance and related kinetics of the materials.