Supercapacitors (electrochemical capacitors, ultracapacitors) possess the huge ability to store a superior power density that is one order of magnitude larger than lithium-ion batteries, and an impressive energy density that is two orders of magnitude higher than the traditional electrolytic capacitors. More importantly, supercapacitors are able to harvest energy in very short periods arranging from minutes to seconds, and to subsequently offer the remarkable peak power and sufficient energy when they are used in portable electronics, automotive and stationary systems. Although supercapacitors are now commercially available, they still require further improvements, especially for increasing energy density through the fundamental understanding of their structure-property relationship and exact operating principles, improvement of electrode materials, selection of suitable electrolytes from aqueous, organic, ion liquids to solid-state type, and interfacial integration of different device components in systems.
Recently, micro-supercapacitors represent one class of the newly developed miniaturized electrochemical energy storage devices. By far, the most notable progress has been significantly advanced by fabricating nanostructured materials, developing thin-film manufacture technologies and device architectures. Nevertheless, ffurther improvement of their energy and power densities is still a pressing needing.
High-Energy Supercapacitors. We are exploring a wide range of synthetic graphene and graphene-like 2D materials for the new generation of electric double layer capacitors, pseudocapacitors, and hybrid supercapacitors. Especially a strong emphasis is placed on the design and reasonable construction of high-energy devices, including asymmetric supercapacitors, lithium ion supercapacitors, and high-voltage supercapacitors in organic and ion liquid electrolytes.
New-Concept Supercapacitors. New-concept smart energy-storage systems with greatly integrated functionality of thinness, flexibility, scalability, and light weight, represent enormous potential as the compatible power source for miniaturized transistors, flexible displays, sensors, radio frequency identification, and organic light-emitting diodes. Graphene and other 2D nanosheets with ultrathin flexibility, excellent electrical conductivities, high surface area, and outstanding electrochemical properties are expected to fill these requirements and thereby considered as such electrode material for the construction of these new-concept smart supercapacitors and micro-supercapacitors with the integrated flexible, foldable, stretchable, transparent features.
On-Chip Micro-Supercapacitors. To promote on-chip energy-oriented applications, we aim at fabricating uniform and conductive thin-film electrodes of graphene and other 2D materials with a high accessible electrochemically activated surface area, excellent electrical conductivity, and constructing superior interfacial integrity of the main components (electrode, separator, electrolyte, current collector, and substrate) into one single device with an elaborated geometry and short ion diffusion pathways, which can achieve unprecedented performance to address the fundamental limits of traditional devices and open up completely new paradigms for various energy-related electronics applications.
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