Parameters influencing the capacitive behavior of carbon composite electrodes: composition, morphology, electrical conductivity, and surface chemistry

The interplay and overlapping of several factors determine the capacitive behavior of carbon composite electrodes for capacitive energy storage application. General guidelines and, hopefully, design principles would be useful for inspiring further development work in this area, beyond a purely empirical approach. The present work attempts to give a contribution in this direction, through a systematic study of the effect of the composition on the behavior of electrodes prepared via a paste-casting method in three composite classes: AC--CNT, AC--RGO, and AC--CNT--RGO. Fundamental properties of individual materials, such as pore structure, specific surface area, and surface chemistry, or of the electrode pastes, such as the electrical conductivity, were characterized by suitable techniques and linked to the observed electrochemical behavior, which was systematically evaluated as a function of the composition. Basic properties, such as conductivity and surface area, have an overwhelming and interlaced influence and should be taken as prerequisites of the pristine materials. Morphology and dimensionality of individual components determine composition thresholds above which the full exploitation or the synergistic enhancement of the properties of individual components may be effectively achieved. Expectedly, since addressing different performance requirements does not necessarily results in a single composite composition, the appropriate content of any constituent should be adjusted based on the target performance demands.