Supercapacitor Electrodes of Blended Carbon Nanotubes with Diverse Conductive Porous Structures Enabling High Charge/Discharge Rates

Electrically conductive porous structures are required to design high-performance supercapacitor electrodes; however, the sophisticated control has been challenging. We propose a facile fabrication method of blended carbon nanotube (CNT) electrodes with diverse conductive porous structures. By blending mildly dispersed aggregate structures of the single type of CNTs, we successfully obtained the CNT films composed of the mutually intertwining network structures, which modulated both meso- and macroporosity (the total pore volume, 1.10–3.81 cm3/g) and electrical conductivity (6–358 S/cm). The electrodes were characterized with an aqueous electrolyte under direct current (DC) and alternating current (AC) conditions, demonstrating the blended CNTs with several-fold higher power densities and smaller relaxation time constants than the singles, namely, higher charge/discharge rating operation. Among them, the pair of high-conductivity/low-pore volume CNTs and low-conductivity/high-pore volume CNTs led to the prominent advancement securing higher pore volumes which the single CNTs did not reach. These improvements stem from both conductivities and pore volumes in meso- and macropore regions, clarified by a heat mapping approach to visualize the relationship. These findings can guide us to structurize supercapacitor electrode materials and present the significance of conductivity and porous structures for high-rate operation capability.