Supercapattery-Diode: Using Layered Double Hydroxide Nanosheets for Unidirectional Energy Storage

The supercapacitor-diode (CAPode) is a device that integrates the functionality of an ionic diode with that of a conventional supercapacitor. The unique combination of energy storage and rectification properties in CAPodes is relevant for iontronics, alternate current rectifiers, logic operations, grid stabilization, and even biomedical applications. Here, we propose a novel aqueous-phase supercapattery-diode with excellent energy storage [total specific capacity (C_T) = 162 C g^-1, energy density = 34 W h kg^-1 at 1.0 A g^-1] as well as rectifying properties [rectification ratio I (RR_I) of 23, and rectification ratio II (RR_II) of 0.98]; the unidirectional energy storage is achieved by the utilization of an ion-selective redox reaction of battery-type layered double hydroxide (LDH) nanosheets serving as the electroactive material as well as asymmetric device configuration of supercapattery-diode in the KOH electrolyte. This work expands the types of CAPodes and importantly exemplifies the significance of integrating battery-type LDH and their redox chemistry, allowing a simultaneous increase in charge storage and rectification properties.