Abstract
Electrolyte composition is a crucial factor determining the capacitive properties of a supercapacitor device. However, its complex influence on the energy storage mechanisms has not yet been fully elucidated. For this purpose, in this study, the role of three different types of electrolytes based on a propylene carbonate (PC) solution containing tetrabutylammonium perchlorate (TBAClO4), lithium perchlorate (LiClO4) and butyltrimethylammonium bis(trifluoromethylsulfonyl)imide (N1114TFSI) ionic liquid on vertically-oriented graphene nanosheet electrodes has been investigated. Herein, in situ electrochemical quartz crystal microbalance (EQCM) and its coupling with electrochemical impedance spectroscopy (EIS), known as ac-electrogravimetry, have allowed the dynamic aspects of the (co)electroadsorption processes at the electrode-electrolyte interface to be examined. A major contribution of ClO4− anions (TBAClO4) was evidenced, whereas in the PC/N1114TFSI mixture (50:50 wt%) both anions (TFSI−) and cations (N1114+) were symmetrically exchanged during cycling. In the particular case of LiClO4, solvation of Li+ cations in PC was involved, affecting the kinetics of electroadsorption. These results demonstrate the suitability of dynamic electrogravimetric methods to unveil the interfacial exchange properties of mobile species for the conception of new high performance energy storage devices.
Highlights
In recent years, the emerging miniaturization technologies have transformed key manufacturing and processing concepts to design an unlimited range of new products by leveraging skills from across many domains, conceiving new product–market paradigms and future innovative products ranging from biomedicine, robotics, and smart watches to wireless sensors
In this study, the role of three different types of electrolytes based on a propylene carbonate (PC) solution containing tetrabutylammonium perchlorate (TBAClO4), lithium perchlorate (LiClO4) and butyltrimethylammonium bis(trifluoromethylsulfonyl)imide (N1114TFSI) ionic liquid on vertically-oriented graphene nanosheet electrodes has been investigated
In the particular case of LiClO4, solvation of Li+ cations in PC was involved, affecting the kinetics of electroadsorption. These results demonstrate the suitability of dynamic electrogravimetric methods to unveil the interfacial exchange properties of mobile species for the conception of new high performance energy storage devices
Summary
The emerging miniaturization technologies have transformed key manufacturing and processing concepts to design an unlimited range of new products by leveraging skills from across many domains, conceiving new product–market paradigms and future innovative products ranging from biomedicine (biomedical implants), robotics, and smart watches to wireless sensors. VOGNs exhibit a non-stacking morphology characterized by the presence of self-organized and interconnected channels perpendicular to the substrate, which favor ion diffusion and wettability of the electrolyte Their high rigidity and 3D inter-network structure leads to a large accessible surface area and high in-plane conductivity [15]. Over the past years, unraveling the phenomena and chemical-physical processes involved at the electrode–electrolyte interface during the charge–discharge cycles of a supercapacitor is key to understand its electrochemical performance [21,22] In this line, advanced modelling techniques based on molecular dynamics and numerical simulation [23,24,25,26] and in situ experimental techniques [27,28] have already provided important insights on the comprehension of energy storage mechanisms in supercapacitors. We take a step forward to provide a complete analysis of the role of different organic and organic/ionic liquid mixture electrolytes (e.g., free solvent, anions, cations and solvated ions), the kinetics of species transferred at the electrode/electrolyte interface and their impact on the capacitive properties of VOGNs through the EQCM and associated methods
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