Synthesis and characterization of aryl substituted functionalized graphene sheets and their electrochemical behavior
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ORIGINAL PAPER
Synthesis and characterization of aryl substituted functionalized graphene sheets and their electrochemical behavior Hamidreza Saneifar 1 & Daniel Bélanger 1 Received: 1 April 2020 / Revised: 9 October 2020 / Accepted: 12 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract We report the electrochemical behavior of free-standing functionalized graphene sheet electrode in a potential window corresponding to that of high-voltage cathode of lithium-ion batteries. Electrochemical exfoliation of graphite yielded graphene oxide sheets that were subsequently heat-treated at 300 °C in inert gas atmosphere. Chemical functionalization of resulting graphene sheets with C6H4CF3, C6H4COOH, and C6H4N(C2H5)2 groups was performed using diazonium chemistry. As-prepared graphene oxide and heat-treated unmodified and modified graphene electrodes were characterized by elemental analysis, 4point probe measurements, Raman spectroscopy, X-ray photoelectron spectroscopy, galvanostatic cycling, and cyclic voltammetry. A smaller voltammetric charge was obtained for electrodes made with graphene sheets functionalized with aryl groups compared to that of unmodified graphene. In addition, the irreversible charge (difference between oxidation and reduction charge) for C6H4CF3-functionalized graphene electrode is much smaller than that of unmodified electrode. These observations suggest that substituted aryl groups grafted on graphene sheets surface can mitigate side reactions at the electrode/electrolyte interface, and the resulting materials could be useful as conductive additive of a high voltage composite electrode. Keywords Few-layer graphene . Functionalization . Diazonium . Carbon additive
Introduction Graphene has been investigated as material for electrochemical energy storage applications such as electrochemical capacitors and rechargeable batteries, in which it has been used both as active electrode materials and additive of a composite electrode [1–5]. The presence of graphene in the composite electrode may improve ionic diffusion through the electrode [6, 7] but more importantly leads to an increase of the electronic conductivity of the composite electrode due to its high electronic conductivity and surface area [8, 9]. However, a drawback of the high surface area of graphene, when used as carbon additive Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10008-020-04843-4) contains supplementary material, which is available to authorized users. * Daniel Bélanger [email protected] 1
Département de Chimie, Université du Québec à Montréal, Case Postale 8888, succursale Centre-Ville, Québec H3C 3P8 Montréal, Canada
of a composite cathode of a lithium-ion battery, is associated with a significant electrolyte decomposition at the electrode/electrolyte interface [10, 11]. Additionally, graphene is prone to restacking during electrode preparation and even upon electrochemical cycling [12, 13]. These phenomena can cause polarization, impedanc
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