Redox-Additives in Aqueous, Non-Aqueous, and All-Solid-State Electrolytes for Carbon-Based Supercapacitor: A Mini-Review

Abstract

Herein, we deliver a brief discussion on the classification, state-of-the-art progress, challenges, and perceptions of the redox-additive materials in the aqueous, nonaqueous, and solid-state electrolytes for high-performance supercapacitors. For the performance of electrochemical capacitors, electrolytes are found to be influential components, governing vital parameters including the voltage window, power, and energy density. To improve the electrolyte performance, the inclusion of redox additive species is counted as the best method where the redox reaction that occurs at the electrode−electrolyte interface mainly contributes to the overall enhancement of the device in terms of energy and power as well as stability. The method of preparation and utilization is quite simple, safe, and cost-effective in comparison with some active electrode materials. Hence, the chemistry behind redox additives seems to be of special interest, and the identification of novel redox additives is believed to be a hotspot in the area of supercapacitor electrode materials. In this, we focus on the interaction between carbon-based electrode materials in different redox-additive electrolytes and their challenges and propose different perspectives that concisely intend to enhance energy density without compromising other merits that are inherent.

Polypyrrole and Graphene Nanoplatelets Inks as Electrodes for Flexible Solid-State Supercapacitor

“…Over the past few decades, there has been an increasing research interest in the field of energy storage systems and, among them, a great deal of attention has been focused on supercapacitors [1][2][3][4]: devices that combine a high power density and a fast charging rate with a simple design that enables them to be flexible, stretchable, and bendable [5][6][7], qualities that make them particularly suited for wearable electronic applications [8][9][10]. Supercapacitors, which consist of a couple of electrodes impregnated with an electrolyte and spaced by an ion-permeable separator, have performances, electric behavior, and even working principles that change depending on the nature of the electrodes, of the medium interposed between the electrodes, and of the electrolyte.…”

A graphdiyne oxide composite membrane for active electrolyte enhanced supercapacitors with super long self-discharge time

“…Compared to the research studies on the modification of electrode materials, active electrolyte enhanced supercapacitors (AEESCs), 5 prepared by adding redox active substances into the capacitor to store additional energy through electrochemical reactions, is simple, safe, and favorable for large-scale preparation. 6,7 Currently, redox active species are usually divided into organic and inorganic additives. Organic additives mainly include p -phenylenediamine, 8,9 hydroquinone, 10 and methylene blue, 11 while inorganic additives are KI, 12 CuS, 13 CuSO 4 , 5 and FeSO 4 .…”

In situ synthesis of nanostructured Fe3O4@TiO2 composite grown on activated carbon cloth as a binder-free electrode for high performance supercapacitors

“…physically store charges via reversible ion adsorption on electrode/electrolyte interfaces for energy storage. [7][8][9][10] Enhanced specic surface area, low cost and compatibility with various electrolytes make EDLCs suitable candidates for commercial supercapacitors. In order to achieve higher capacitance than EDLCs, electrochemically active materials are also developed for supercapacitors applications, which are categorized as pseudocapacitors (PCs).…”