The complex impedance of carbon ultracapacitor electrodes is reviewed. The equivalent circuit of an ultracapacitor electrode consists of a distribution of ionic resistance and double-layer capacitance down a linear ladder network. This model is extended to electroactive porous intercalation electrodes. Under some circumstances these intercalation electrodes yield complex impedance spectra identical to those of the ultracapacitor electrodes except that the capacitance of the intercalation electrode is not related to its double-layer capacitance, but to the finite diffusion process that limits the charge transfer reaction.
展开▼
