Supercapattery-Diode:\nUsing Layered Double Hydroxide\nNanosheets for Unidirectional Energy Storage

The supercapacitor-diode (CAPode) is a device that integrates\nthe\nfunctionality of an ionic diode with that of a conventional supercapacitor.\nThe unique combination of energy storage and rectification properties\nin CAPodes is relevant for iontronics, alternate current rectifiers,\nlogic operations, grid stabilization, and even biomedical applications.\nHere, we propose a novel aqueous-phase supercapattery-diode with excellent\nenergy storage [total specific capacity (<i>C</i><sub>T</sub>) = 162 C g<sup>–1</sup>, energy density = 34 W h kg<sup>–1</sup> at 1.0 A g<sup>–1</sup>] as well as rectifying properties\n[rectification ratio I (RR<sub>I</sub>) of 23, and rectification ratio\nII (RR<sub>II</sub>) of 0.98]; the unidirectional energy storage is\nachieved by the utilization of an ion-selective redox reaction of\nbattery-type layered double hydroxide (LDH) nanosheets serving as\nthe electroactive material as well as asymmetric device configuration\nof supercapattery-diode in the KOH electrolyte. This work expands\nthe types of CAPodes and importantly exemplifies the significance\nof integrating battery-type LDH and their redox chemistry, allowing\na simultaneous increase in charge storage and rectification properties.