Identifying the proper carbon material is one of the key requirements in developing high-performance supercapacitor electrodes. Carbon nanotubes (CNTs), graphene nano-platelets (GNP), and graphite (Gr) are commonly used carbon allotropes for supercapacitor applications. The performance of those materials depends on the electrolyte used and the operating potential window. However, those parameters have rarely been investigated and explained. Herein, we present a roadmap for the proper selection of carbon materials in supercapacitor applications via the investigation of the behavior of CNTs, GNPs, and Gr in different electrolytes using both electrochemical and computational tools. The charge storage mechanism was found to be electrolyte-dependent. In terms of the operating potential window, the best performance was obtained upon the use of Na2SO4 electrolyte, which enabled a potential window between -1 and 0.9 V. While in terms of capacitance, the positive electrodes in H2SO4 electrolyte exhibited the highest capacitance. H2SO4 enabled keto-enol tautomerism in the positive potential window and can enlarge the potential window to 1 V. Quantum capacitance calculations helped to identify the reasons behind the obtained different performances in the negative and positive potential windows. For example, upon the identification of the proper electrolyte and potential window, it was possible to obtain a capacitance as high as 453.60 F/g at 5 mV/s in a potential window of 1 V for CNTs, which are much higher than those reported in the literature. Moreover, the guidelines were successfully used to develop a symmetric device that delivers an energy density of 23.2 Wh/Kg, a power density of 475 W/Kg with stability of 97.8% after 5000 cycles over a potential window of 1.9 V that are much higher than those reported for CNTs-based symmetric devices. Also, we have investigated the higher Fullerene C76 for the first time proving its superior performance and applicability in supercapacitor applications.

Effect of electrolyte and carbon morphology for a high-performance supercapacitor device: Comparative experimental and theoretical insights

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.