Complex capacitance analysis on rate capability of electric-double layer capacitor (EDLC) electrodes of different thickness

• Published in: Electrochimica acta 2005-04, Vol.50 (11), p.2255-2262
• Main Authors: Yoon, Songhun, Jang, Jong H., Ka, Bok H., Oh, Seung M.
• Format: Article
• Language: English
• Subjects: Applied sciences; Capacitors. Resistors. Filters; Complex capacitance analysis; Electric double-layer capacitors (EDLC); Electrical engineering. Electrical power engineering; Exact sciences and technology; Impedance analysis; Porous carbon; Transmission line model; Various equipment and components
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2004.10.009

The complex capacitance analysis is utilized to examine the thickness-dependent rate capability of electric double-layer capacitor (EDLC) electrodes. Based on the transmission line model, the theoretical imaginary capacitance is derived for porous carbon electrodes, where the resistance relevant to ion transport in pores of carbon particles (intra-particle pores) and within electrode layer (inter-particle pores) is assumed to be the major component for equivalent series resistance (ESR). The use of hexagonal mesoporous carbon (HMC) as the EDLC electrode material, which has a well-defined pore structure, allows us to estimate the number of intra-particle pores in the composite electrodes such that the two resistance components are separately analyzed as a function of electrode thickness. As the theoretical derivation suggests, the time constant for intra-particle pores is invariant against the electrode thickness, whereas the time constant for inter-particle pores becomes larger for thicker electrodes. The poorer rate capability observed in the thicker electrodes is thus ascribed to a larger time constant for inter-particle pores.