Biomass-derived renewable carbon materials for electrochemical energy storage

TL;DR: In this article, the authors proposed a method of biocharring these plants and insects derived products that could help us regain this carbon and nitrogen in the form of bio-charred energy materials, which could open up new avenues of business for silk and jute farmers of the world.

TL;DR: In this paper, the authors present a kind of novel energy storage devices with long cycle stability and high power density, which are called supercapacitors, and select the materials selection is one of the key factors that affect the properties of su...

TL;DR: Researchers developed a water-soluble, conductive composite binder (SA-CR) for recyclable LiFePO4 cathodes, exhibiting improved electrochemical performance, with a specific capacity of 118.8 mAh/g and 92.1% capacity retention at the 100th cycle.

TL;DR: The direct synthesis of large-scale graphene films using chemical vapour deposition on thin nickel layers is reported, and two different methods of patterning the films and transferring them to arbitrary substrates are presented, implying that the quality of graphene grown by chemical vapours is as high as mechanically cleaved graphene.

TL;DR: Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density.

Abstract: Graphene is the name given to a two-dimensional sheet of sp2-hybridized carbon. Its extended honeycomb network is the basic building block of other important allotropes; it can be stacked to form 3D graphite, rolled to form 1D nanotubes, and wrapped to form 0D fullerenes. Long-range π-conjugation in graphene yields extraordinary thermal, mechanical, and electrical properties, which have long been the interest of many theoretical studies and more recently became an exciting area for experimentalists. While studies of graphite have included those utilizing fewer and fewer layers for some time,1 the field was delivered a jolt in 2004, when Geim and co-workers at Manchester University first isolated single-layer samples from graphite (see Figure 1).2 This led to an explosion of interest, in part because two-dimensional crystals were thought to be thermodynamically unstable at finite temperatures.3,4 Quasi-twodimensional films grown by molecular beam epitaxy (MBE) are stabilized by a supporting substrate, which often plays a significant role in growth and has an appreciable influence on electrical properties.5 In contrast, the mechanical exfoliation technique used by the Manchester group isolated the two-dimensional crystals from three-dimensional graphite. Resulting singleand few-layer flakes were pinned to the substrate by only van der Waals forces and could be made free-standing by etching away the substrate.6-9 This minimized any induced effects and allowed scientists to probe graphene’s intrinsic properties. The experimental isolation of single-layer graphene first and foremost yielded access to a large amount of interesting physics.10,11 Initial studies included observations of graphene’s ambipolar field effect,2 the quantum Hall effect at room temperature,12-17 measurements of extremely high carrier mobility,7,18-20 and even the first ever detection of single molecule adsorption events.21,22 These properties generated huge interest in the possible implementation of graphene in a myriad of devices. These include future generations of high-speed and radio frequency logic devices, thermally and electrically conductive reinforced composites, sensors, and transparent electrodes for displays and solar cells. Despite intense interest and continuing experimental success by device physicists, widespread implementation of graphene has yet to occur. This is primarily due to the difficulty of reliably producing high quality samples, especially in any scalable fashion.23 The challenge is really 2-fold because performance depends on both the number of layers present and the overall quality of the crystal lattice.19,24-26 So far, the original top-down approach of mechanical exfoliation has produced the highest quality samples, but the method is neither high throughput nor high-yield. In order to exfoliate a single sheet, van der Waals attraction between exactly the first and second layers must be overcome without disturbing any subsequent sheets. Therefore, a number of alternative approaches to obtaining single layers have been explored, a few of which have led to promising proof-ofconcept devices. Alternatives to mechanical exfoliation include primarily three general approaches: chemical efforts to exfoliate and stabilize individual sheets in solution,27-32 bottom-up methods to grow graphene directly from organic precursors,33-36 and attempts to catalyze growth in situ on a substrate.37-43 Each of these approaches has its drawbacks. For chemically derived graphene, complete exfoliation in solution so far requires extensive modification of the 2D crystal lattice, which degrades device performance.31,44 Alternatively, bottom-up techniques have yet to produce large and uniform † Department of Chemistry and Biochemistry and California NanoSystems Institute. ‡ Department of Materials Science and Engineering and California NanoSystems Institute. Chem. Rev. 2010, 110, 132–145 132

TL;DR: This tutorial review provides a brief summary of recent research progress on carbon-based electrode materials forsupercapacitors, as well as the importance of electrolytes in the development of supercapacitor technology.