Design of nitrogen doped graphene grafted TiO2 hollow nanostructures with enhanced sodium storage performance

Nitrogen doped graphene supported TiO2 hollow nanostructures varying from 10 to 15 nm were designed for sodium ion battery anode applications, which were obtained by a two-step technique hydrothermalcalcining process with urea as an inhibitor and a nitrogen source. The active nitrogen modified graphene matrix supported hollow hierarchical-pore nanoarchitectures, possessing high surface area, massive pores including micro-, meso- and macro-pores, and excellent structural stability, which are highly desirable for application in sodium ion batteries. Its interconnected carbon network ensures good conductivity and fast electron transport; the micro-, meso-, and macroporous nature effectively shortens the sodium ion diffusion path and provides the room necessary for volume expansion. The large specific surface area is beneficial for better contact between the electrode materials and the electrolyte. Such material exhibits excellent performance as anode materials for sodium ion batteries with a high reversible capacity, excellent cycle stability and superior rate capability. Besides, nitrogen and graphene play a crucial role in controlling the formation of the TiO2 hollow nanocrystals.