Switchable Supercapacitors with Transistor‐Like Gating Characteristics (G‐Cap)

Abstract

A novel three-electrode electrolyte supercapacitor (electric double-layer capacitor [EDLC]) architecture in which a symmetrical interdigital "working" two-electrode micro-supercapacitor array (W-Cap) is paired with a third "gate" electrode that reversibly depletes/injects electrolyte ions into the system controlling the "working" capacity effectively is described. All three electrodes are based on precursor-derived nanoporous carbons with welldefined specific surface area (735 m 2 g −1 ). The interdigitated architecture of the W-Cap is precisely manufactured using 3D printing. The W-Cap operating with a proton conducting PVA/H 2 SO 4 -hydrogel electrolyte and high capacitance (6.9 mF cm −2 ) can be repeatedly switched "on" and "off ". By applying a low DC bias potential (−0.5 V) at the gate electrode, the AC electroadsorption in the coupled interdigital nanoporous carbon electrodes of the W-Cap is effectively suppressed leading to a stark capacity drop by two orders of magnitude from an "on" to an "off " state. The switchable micro-supercapacitor is the first of its kind. This general concept is suitable for implementing a broad range of nanoporous materials and advanced electrolytes expanding its functions and applications in future. The integration of intelligent functions into EDLC devices has extensive implications for diverse areas such as capacitive energy management, microelectronics, iontronics, and neuromodulation.

A Review: Ion Transport of Two-Dimensional Materials in Novel Technologies from Macro to Nanoscopic Perspectives

“…Examples include the capacitive behavior of metallic electrodes and of two-dimensional (2D) materials such as graphite, graphene and transition metal dichalcogenides (TMDs) family. These concepts should assist the development of the electrochemical devices (also refer to the electrochemical system) i.e., energy storages [6,25,26], capacitive deionization [27], 2D-based membrane (electrochemical ions sieving) [9,[28][29][30], and ion transport controls [31][32][33].…”

“…Although microsupercapacitors with in-plane interdigitated configuration have been intensively researched for on-chip energy storage [112,[115][116][117][118], exploration of their use for novel functionalities is still in an early stage. Over the past five years, researchers have gained increased attention through their investigation of such functionalities for novel applications, such as direct visualization of the energy storage state [119], light-induced energy storage and photodetection [120] and ion transport control [31]. These functions are enabled by the stimulus-responsive behavior of the microsupercapacitors, in which properties such as color and capacitance can be tuned via an external stimulus [31,119,120].…”

“…Over the past five years, researchers have gained increased attention through their investigation of such functionalities for novel applications, such as direct visualization of the energy storage state [119], light-induced energy storage and photodetection [120] and ion transport control [31]. These functions are enabled by the stimulus-responsive behavior of the microsupercapacitors, in which properties such as color and capacitance can be tuned via an external stimulus [31,119,120]. In the following sections, we will show how the stimulus-responsive microsupercapacitors can be used in those applications.…”

“…In 2020, Lochmann et al developed the first switchable microsupercapacitor with inplane interdigitated configuration based on the architecture of a field effect transistor (FET), Figure 15a, with capacitance-tuning capability governed by the control of ion transport (Figure 15c) [31].…”

Green Precursors and Soft Templating for Printing Porous Carbon‐Based Micro‐supercapacitors

“…In the field of MSCs, aw ide range of materials and various structuring approaches have been investigatedi nr ecent years. Appropriate electrode materials supplyingh ighly active surface areas and good electrical conductivities are activated carbons, [16][17][18][19] conducting polymers, [20] MXenes, [21,22] or metal oxides( RuO 2 ,M nO 2 ). [23] The use of various composite materials is also widely established.…”