Nitrogen-doped porous carbon coated on graphene sheets as anode materials for Li-ion batteries.

A hierarchical structure of nitrogen-doped porous carbon coated on graphene sheets (GNC) has been successfully synthesized via a facile method. Notably, nitrogen-doped porous carbon (NC) was prepared by direct calcinations of sodium citrate and urea without aid of any additional carbon source and template. The porous structure arises from the decomposition of sodium citrate and the formative Na₂CO₃ is the hard template during the annealing process. To our pleasure, the 3D architecture is derived from the graphene sheets as skeleton to support porous carbon, which avoids the agglomeration of graphene and enlarges the specific surface area of porous carbon. Besides, using urea as resource of N element promotes a high N-doping level (3.33 atom %) and improves electrical conductivity and lithium storage sites. Thus, the obtained GNC-700 °C as an anode material delivers a high-reversible capacity of 842.7 mAh g⁻¹ at 0.1 A g⁻¹ and good cycling performances (431.4 mAh g⁻¹ at 0.5 A g⁻¹ after 200 cycles). The distinguished carbon anode material demonstrates an appealing development for Li-ion batteries. [ABSTRACT FROM AUTHOR]