In 2019, the "CAPode" was proposed, in which diodic properties are implemented into an electrochemical capacitor (EC) realizing an asymmetric capacitive-analogue of the semiconductor-based diode. The working principle in the original CAPode concept is based on the unidirectional charging of the electrical double-layer capacitor (EDLC; one type of EC) due to the selection of two carbon materials with different pore sizes together with an electrolyte with highly asymmetric ion sizes (Figure ). Due to defined microporosity of the sieving carbon (d < 0.9 nm) only the anions smaller than the respective pore size can enter the pores, while larger cations are excluded leading to a unidirectional charging only under "open" (chargeable) polarization (forward bias direction).