Nitrogen-doped carbon/graphene hybrid anode material for sodium-ion batteries with excellent rate capability

Nitrogen-doped carbon/graphene (NCG) hybrid materials were prepared by an in-situ polymerization and followed pyrolysis for sodium-ion batteries. The NCG has a large interlayer distance (0.360 nm) and a high nitrogen content of 7.54 at%, resulting in a high reversible sodium storage capacity of 336 mAh g^-1 at 30 mA g^-1. The NCG shows a sandwich-like structure, i.e. nitrogen-doped carbon nanosheets closely coated on both sides of graphene. The carbon nanosheets shorten the ion diffusion distance, while the sandwiched graphene with high electronic conductivity guarantees fast electron transport, making the NCG exhibit excellent rate capability (94 mAh g^-1 at 5 A g^-1). It also exhibits good cycle stability with a capacity retention of 89% after 200 cycles at 50 mA g^-1.