Optimizing the electrochemical performance of aqueous symmetric supercapacitors based on an activated carbon xerogel

• Published in: Journal of power sources 2013-11, Vol.241, p.776-782
• Main Authors: Calvo, E.G., Lufrano, F., Staiti, P., Brigandì, A., Arenillas, A., Menéndez, J.A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Aqueous electrolyte; Capacitors; Capacitors. Resistors. Filters; Carbon; Carbon xerogel; Electrical engineering. Electrical power engineering; Electrode manufacturing process; Electrodes; Electrolytic cells; Exact sciences and technology; Supercapacitor; Supercapacitors; Texture; Various equipment and components; Xerogels
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2013.03.065

A highly porous carbon xerogel was synthesized by means of physical activation. The activated carbon xerogel, which displayed a well-developed porous texture (micro- and meso-porosity), was employed as electrode material in different supercapacitors. In assessing the performance of the supercapacitors, special attention was paid to their dimensions and the type of electrolyte used. Both the method of electrode manufacture (rolling and punching of 1 cm2 pellets vs. casting by means of a film applicator to produce 4 cm2 electrodes) and the type of supercapacitor (Swagelok (R) system vs. cell with graphite plate current collectors) were evaluated. The results reveal that the cells with larger electrodes were able to store higher amounts of energy. In addition to the cells, the electrochemical characteristics in aqueous electrolytes with a different pH were studied (H2SO4, Na2SO4 and KOH, 1 M). The highest capacitance values were achieved with sulphuric acid (196 F g−1 as opposed to 140 and 106 F g−1 for Na2SO4 and KOH, respectively), probably due to its higher ionic conductivity and the basic nature of the oxygen functionalities found on the surface of the carbon xerogel. Nevertheless, because of the corrosive character of sulphuric acid, Na2SO4 would be a more suitable electrolyte. •Highly micro-mesoporous carbon xerogels were used as electrodes in aqueous supercapacitors.•The electrodes preparation procedure significantly affects their electrical and mechanical properties.•The electrolyte pH and the chemical nature of carbon xerogel influence the energy storage.•C values of ∼200 F g−1 were achieved with H2SO4 electrolyte medium which producing higher charge storage.