Synthesis of N-Doped Porous Carbon/Carbon Micro-Nanotubes/NixCoyOz Nanosheets as a High-Capacity Electrode Material for Supercapacitors

The N-doped porous carbon (NPC) /carbon micro-nanotubes (CMNT) /NixCoyOz nanosheets with rich mesopores and 1.37 wt% nitrogen doping are successfully synthesized by a pyrolysis-ionization-precipitation combination process, using coal-based polyaniline and nickelocene as original materials. Therein, most of the CMNT are upright CMTs and worm-like curved CNTs, and a few are bamboo-like tubes or carbon nanofibers. Moreover, many flower-like aggregates assembled by spinel NiCo2O4 nanosheets are anchored on the surface of the NPC and CMNT. The NPC/CMNT/NixCoyOz exhibits a high specific capacitance and cycling stability, attributed to the large BET specific surface area (485 m(2)/g), suitable BET average pore size (2.3 nm), good hydrophilicity and wettability, and synergistic effects among three components. The assembled NPC/CMNT/NixCoyOz//AC asymmetric supercapacitor also demonstres a high specific capacitance of 120 F g(-1) at a current density of 1 A g(-1) and a high energy density of 16.7 Wh kg(-1) at a power density of 500 W kg(-1).