The electrochemical behavior of common electrode materials used in ECs and related devices will be discussed in terms of capacitive, pseudocapacitive  and Faradic charge-storage mechanisms, as well as recommended methods with which such electrodes should be characterized. The distinctions between carbon-based capacitive electrodes  that are commonly found in commercial ECs, and pseudocapacitive electrodes such as RuO2 [5,6], or MnO2[7,8], that have the electrochemical signature of a capacitive electrode but express different charge-storage mechanisms, will be highlighted. Finally, the important distinctions between high-power battery-type electrodes and pseudocapacitive electrodes will be described. New emerging concepts such as extrinsic pseudocapacitance  or intercalation pseudocapacitance  will be discussed at the light of recent results in the field.
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