@AlfredCentauri I think that this means that I was referring to a physical capacitor, which "approximates $$i_C = C \frac{dv_C}{dt}$$ under certain operating conditions." In an electrochemical capacitor, (counter)ions in the electrolyte migrate toward a charged electrode, forming a so-called "electric double layer." Conceptually, an electrochemical capacitor contains two electric double layers -- one at each electrode.

@AlfredCentauri Thanks for your time. I am a chemist, and I am not extremely well versed in the physics and engineering of electronics. When I said "ideal capacitor," I was referring to a capacitor not exhibiting pseudocapacitance. Pseudocapacitance occurs when an electrochemical capacitor acts almost like a battery; Faradaic redox reactions occur between an electrode (e.g., carbon) and the electrolyte sandwiched between the electrodes. So by "ideal capacitor," I meant a capacitor whose capacitance obeys $$C = \frac{Q}{V}$$ and that does not undergo chemical reactions.