Nitrogen-Doped Hollow Amorphous Carbon Spheres@Graphitic Shells Derived from Pitch: New Structure Leads to Robust Lithium Storage

Nitrogen-doped mesoporous hollow carbon spheres (NHCS) consisting of hybridized amorphous and graphitic carbon were synthesized by chemical vapor deposition with pitch as raw material. Treatment with HNO3 vapor was performed to incorporate oxygen-containing groups on NHCS, and the resulting NHCS-O showed excellent rate capacity, high reversible capacity, and excellent cycling stability when tested as the anode material in lithium-ion batteries. The NHCS-O electrode maintained a reversible specific capacity of 616 mAh g−1 after 250 cycles at a current rate of 500 mA g−1, which is an increase of 113 % compared to the pristine hollow carbon spheres. In addition, the NHCS-O electrode exhibited a reversible capacity of 503 mAh g−1 at a high current density of 1.5 A g−1. The superior electrochemical performance of NHCS-O can be attributed to the hybrid structure, high N and O contents, and rich surface defects.