Graphene-based materials for flexible supercapacitors

Abstract

The demand for flexible/wearable electronic devices that have aesthetic appeal and multi-functionality has stimulated the rapid development of flexible supercapacitors with enhanced electrochemical performance and mechanical flexibility. After a brief introduction to flexible supercapacitors, we summarize current progress made with graphene-based electrodes. Two recently proposed prototypes for flexible supercapacitors, known as micro-supercapacitors and fiber-type supercapacitors, are then discussed. We also present our perspective on the development of graphene-based electrodes for flexible supercapacitors.

High quality reduced graphene oxide flakes by fast kinetically controlled and clean indirect UV-induced radical reduction

“…Next, we found that the addition of 1 wt% of acetone also accelerates the phototransformation of GO -the reaction time has been shortened to 1 h (Table 1). This 4-fold acceleration effect is most likely due to the scavenging of e CB − by acetone (6). Here, an acetone radical anion is formed which should promptly be protonated giving a strongly reducing alkyl radical (CH 3 ) 2 C • (OH), the same as generated via reaction (4) with 86% yield.…”

“…The reasons for this are the unique properties of graphene such as very high electrical and thermal conductivity, ultra-high carrier mobility, optical transparency, high mechanical, chemical and physical stability and many more. The most promising applications of graphene are nano-electronic devices, [1][2][3][4][5] supercapacitors, 6 solar cells, 7,8 gas sensors, 9 energy-storage materials, 10,11 in bioapplications 7,8,[12][13][14] or as a new membrane material. 15 High purity graphene obtained by mechanical exfoliation of graphite, chemical vapor deposition growth from carbon precursors or epitaxial growth on silicon carbide could not be used for large-scale applications due to its high costs.…”

Recent progress in carbon-based nanoarchitectures for advanced supercapacitors

“…Graphene, a 2D periodic honeycomb lattice structure stacked by carbon monolayers consisting of hexatomic ring, belongs to the large family of 2D carbon forms [106,107]. Owing to its intriguing characteristics of superb electrical and thermal conductivities, large specific surface area, and mechanical property, graphene has been developed as a new but competitive candidate for applying in electrochemical energy storage devices [108,109].…”

“…Theoretically, the parallel plates could offer enormous paths through which electrolyte ions can easily approach the surface of each graphene layers with reduced diffusion resistance. The excellent conductivity of graphene layers could omit the use of conductive additives, making graphene-based electrodes show improved energy density [107]. Owing to the strong cohesive van der Waals energy and intensive π-π interaction between the planar basal planes, however, graphene layers exhibit the strong tendency to restack together, which arises at stages in both electrode manufacture and cycling, and this may significantly decrease the ion-accessible surfaces and limit ion and electron transport due to narrower channels, strongly reducing the practical surface available for charge storage [106,111,112].…”

“…Therefore, to explore the approaches for the mitigation of these detrimental effects is essential. Hitherto, numerous strategies have been explored to impede the aggregation of graphene layers so as to increase surface area, reduce the inner resistance, and facilitate the dispersal of electrolyte to the internal part of the electrode when assembled to a SC [107,111].…”