Nitrogen-Doped Mesoporous Carbons for Supercapacitor Electrodes with High Specific Volumetric Capacitance

To pursue the miniaturization of supercapacitors in practical use, it is critical to construct an efficient but limited porosity of a nanocarbon-based electrode for simultaneously obtaining a high utilization of energy storage places and high coating density. However, current studies dominantly focus on the enhancement of specific mass capacitance (C_m) by increasing the pore volume and surface area, leading to a low coating density and, thereby, resulting in a low specific volumetric capacitance (C_V). We report herein the fabrication of a nitrogen-doped mesoporous carbon (NNCM), whose tunable pore volume coupled with the fixed mesopore size offers us the possibility to control the coating density, thus optimizing the C_V and C_m for different application purposes. As a result, NNCM with the highest pore volume and surface area of 2.11 cm³ g^-1 and 663 m² g^-1 demonstrates the highest C_m (190 F g^-1) but lowest C_V (124 F cm^-3) because the overhigh porosity reduces the coating density greatly. NNCM with moderate pore volume and surface area of 1.22 cm³ g^-1 and 489 m² g^-1 shows the highest C_V of 200 F cm^-3, although it presents a low C_m of 147 F g^-1. These results may raise concerns about constructing a suitable porosity to realize a target-oriented use, particularly those targeting miniaturized devices.