In all three bias stages, the WE (Cmicro; red markers) shows a very asymmetric capacitance distribution due to its ion sieving characteristics while CE (Cmeso; blue markers) is charging symmetrical with the typical rectangular CV shape. The ion mixing region was distinguished based on the gradually increasing capacitance of WE, which indicates the gradual penetration of small BF4 -anions into Cmicro. In the "no bias" state, the WE and CE are operating mainly in potential region of ions exchange and in region where only cations are adsorbed. However, when a small Ubias is applied (-0.1 V; second row in Figure ), the operating potential of CE and WE is highly shifted to positive values (to meet the small voltage difference to the GE). This potential shift enabling the WE to operate (under "open" polarization) in the region that corresponds mainly to the adsorption of anions. In this potential range, the number of adsorbed cations on Cmeso is much greater than in the "no bias" state. The greater number of adsorbed cations is balanced by the greater number of adsorbed anions on Cmicro. Consequently, the system capacitance increases. Note, that the charge accumulation of WE in the "open" direction is balanced by both CE and GE both cycling in a more negative potential region (GE is not depicted in the graph). The described phenomena (matching potential distribution for a more efficient attraction of anions) can additionally contribute to a higher achievable capacitance even when small Ubias are applied. When higher Ubias are applied (e.g. -1 V), both WE and CE are shifted to more positive potentials (third row in Figure ) mainly contributing to an attraction of anions during cycling while the charge is compensated by GE (cycling in the negative potential region).