Hierarchical design of nitrogen-doped porous carbon nanorods for use in high efficiency capacitive energy storage

We report a novel synthesis route for creating 3D interconnected hierarchical porous nitrogen-doped carbon nanorods (3D-IPCRs) using 1D polyaniline nanorods as a precursor and SiO₂ as a porogen. The 1D carbon nanorod/SiO₂ composites initially formed during carbonization further act as raw materials for a KOH activation process. After subsequent removal of the templates, as-prepared 3D-IPCRs exhibit a high specific surface area (1765 m² g^-1), a large total pore volume (1.06 cm³ g^-1), an interconnected porous structure, and a moderate nitrogen doping (2.63 wt%). This interconnectivity is beneficial to improving ion diffusion properties and electrolyte wettability. The resulting carbon exhibits a much lower impedance resistance and smaller contact angle, compared with conventional mesoporous carbon, and thus has better electric double layer performance. As obtained 3D-IPCR electrodes achieve a high specific capacitance of 302 F g^-1 at a current density of 0.05 A g^-1 in 6 M KOH (two-electrode system), high coulombic efficiency (99.8%) and excellent cycling stability (92.8% of capacitance retention after 10 000 cycles) even with a high mass loading (11 mg cm^-2) and thick electrode film (300 μm). Furthermore, the energy density of 3D-IPCRs reaches 23 W h kg^-1, and the power density can be as high as 18.2 kW kg^-1 when the energy density remains at 9.11 W h kg^-1 in an organic electrolyte.