Impedance-based study of capacitive porous carbon electrodes with hierarchical and bimodal porosity

• Published in: Journal of power sources 2013-11, Vol.241, p.266-273
• Main Authors: Suss, Matthew E., Baumann, Theodore F., Worsley, Marcus A., Rose, Klint A., Jaramillo, Thomas F., Stadermann, Michael, Santiago, Juan G.
• Format: Article
• Language: English
• Subjects: Applied sciences; Capacitive deionization; Capacitors; Capacitors. Resistors. Filters; Carbon; Carbon aerogel; Electrical engineering. Electrical power engineering; Electrochemical impedance spectroscopy; Electrodes; Energy; Energy storage; Energy use; Energy. Thermal use of fuels; Exact sciences and technology; Hierarchical carbon; Ion storage; Nanostructure; Porosity; Supercapacitor; Transport and storage of energy; Various equipment and components
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2013.03.178

Porous electrode capacitors are used extensively in systems which store energy, harvest mixing energy, or desalinate water. These electrodes can possess a hierarchical pore structure with larger macroscale pores allowing for facile ion and fluid transport, and smaller, nanometer-scale pores enabling significant ion storage. We here present a combined theoretical (linear circuit model) and experimental (electrochemical impedance spectroscopy) study of porous carbon electrode capacitors which integrate nanoscale pores into a micron-scale porous network. Our experiments are performed on a set of custom-fabricated hierarchical carbon aerogel electrodes with varying pore structure, including electrodes with sub-nanometer (sub-nm) pores. Our combined theory and experimental approach allows us to demonstrate the utility of our model, perform detailed characterizations of our electrodes, study the effects of pore structure variations on impedance, and propose hierarchical electrode design and characterization guidelines. Further, we demonstrate that our approach is promising toward the detailed study of ion storage mechanisms in sub-nm pores. •Novel framework for characterizing hierarchical and bimodal supercapacitor electrodes.•First detailed characterization of hierarchical carbon aerogel monolith electrode set.•Novel measurements and analysis of an HCAM electrode with sub-nanometer sized pores.