Exploring the chemistry of “Organic/water-in-salt” electrolyte in graphene-polypyrrole based high-voltage (2.4V) microsupercapacitor

Abstract

Aqueous electrolytes are facing substantial barriers for their all-around use in electrochemical energy storage applications due to their limited operating voltage window. To overcome this issue, “Water-in-salt” electrolyte is known to be the best finding to deal with the electrochemical stability window (ESW). The present work demonstrates the fabrication of laser-irradiated graphene (LIG)-polypyrrole (PPy) hybrid material with enhanced effective surface area, electrical and electrochemical properties, which was further used to build a symmetrical metal-free microsupercapacitor (MSC) with greater electrochemical performances. The attractive feature of this work is the incorporation of a pseudocapacitive material (i.e., PPy) in LIG to increase the electrochemical storage capacity of the device in “Acetonitrile/water-in-salt” electrolyte (AWIS) accompanying higher ESW up to 2.4 V. Moreover, the changes in the electrolyte solvation structure with salt concentration and different solvent mixture ratios were studied via Raman analysis in support with 1H NMR measurements. The resulting symmetrical metal-free LIG-PPyAWIS MSC yields high specific capacitance of 124 mF cm−2, the energy density of 99.2 μWh cm−2 and a power density of 47.75 mW cm−2, shows significant progress among other graphene based MSCs. The designed LIG-PPy module attains a large voltage of 20 V by integrating only nine devices in series combination which provides the future scope of the material in high voltage energy applications.