Construction of Supercapacitor-Based Ionic Diodes with Adjustable Bias Directions by Using Poly(ionic liquid) Electrolytes.

The newly emerging supercapacitor-diode (CAPode), integrating the characteristics of a diode into an electrical-double-layer capacitor, can be employed to extend conventional supercapacitors to new technological applications and may play a crucial role in grid stabilization, signal propagation, and logic operations. However, the reported CAPodes have only been able to realize charge storage in the positive-bias direction. Here, bias-direction-adjustable CAPodes realized by using a polycation-based ionic liquid (IL) or a polyanion-based IL as electrolyte in an asymmetric carbon-based supercapacitor architecture are proposed. The resulting CAPodes exhibit charge-storage function at only the positive- or negative-bias direction with a high rectification ratio (≈80% for rectification ratio II, RRII ) and an outstanding cycling life (4500 cycles), representing a crucial breakthrough for designing high-performance capacitive ionic diodes.