Electrochemical Double-Layer Capacitors: Comparative Evaluation of Carbon Nanotube Electrodes

Abstract

Electrochemical double-layer capacitors (EDLCs), also known as supercapacitors, stand out as promising energy storage devices due to their high power capability, fast charge–discharge response, and long cycle life. The performance of these devices strongly depends on the surface area and electrical conductivity of the electrodes employed. In this work, a comparative evaluation of carbon nanotube electrodes obtained by two different routes was carried out: chemical vapor deposition (CVD) and the application of carbon nanotube-based conductive ink. The electrodes were characterized by scanning electron microscopy (SEM) and Raman spectroscopy, while the electrochemical performance was analyzed by cyclic voltammetry and galvanostatic charge–discharge tests. SEM images revealed vertically aligned growth of nanotubes in the CVD electrodes, whereas electrodes produced by conductive ink exhibited a more irregular morphology with the formation of agglomerates. The electrochemical results indicated higher total capacitance for the devices with CVD electrodes (7.9 mF) compared to those with conductive ink electrodes (3.3 mF). The observed differences were attributed to the structural organization of the nanotubes and to the influence of the polymeric matrix present in the ink, which contributes to higher internal resistance. The results demonstrate that although the CVD technique provides better electrochemical performance, conductive ink offers advantages in terms of simplicity and scalability potential, highlighting the importance of selecting the fabrication method according to the intended application.