In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. 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 of ES (476 references).

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A review of electrode materials for electrochemical supercapacitors

Li-ion battery materials: present and future

Worldwide commercial interest in carbon nanotubes (CNTs) is reflected in a production capacity that presently exceeds several thousand tons per year. Currently, bulk CNT powders are incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters. Advances in CNT synthesis, purification, and chemical modification are enabling integration of CNTs in thin-film electronics and large-area coatings. Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.

/pdf/carbon-nanotubes-present-and-future-commercial-applications-1nhq3xy4hh.pdf

Carbon Nanotubes: Present and Future Commercial Applications

Electrochemical energy storage technology is based on devices capable of exhibiting high energy density (batteries) or high power density (electrochemical capacitors). There is a growing need, for current and near-future applications, where both high energy and high power densities are required in the same material. Pseudocapacitance, a faradaic process involving surface or near surface redox reactions, offers a means of achieving high energy density at high charge–discharge rates. Here, we focus on the pseudocapacitive properties of transition metal oxides. First, we introduce pseudocapacitance and describe its electrochemical features. Then, we review the most relevant pseudocapacitive materials in aqueous and non-aqueous electrolytes. The major challenges for pseudocapacitive materials along with a future outlook are detailed at the end.

https://hal.archives-ouvertes.fr/hal-01171774/document

Pseudocapacitive oxide materials for high-rate electrochemical energy storage

Electrospinning is a highly versatile method to process solutions or melts, mainly of polymers, into continuous fibers with diameters ranging from a few micrometers to a few nanometers. This technique is applicable to virtually every soluble or fusible polymer. The polymers can be chemically modified and can also be tailored with additives ranging from simple carbon-black particles to complex species such as enzymes, viruses, and bacteria. Electrospinning appears to be straightforward, but is a rather intricate process that depends on a multitude of molecular, process, and technical parameters. The method provides access to entirely new materials, which may have complex chemical structures. Electrospinning is not only a focus of intense academic investigation; the technique is already being applied in many technological areas.

Electrospinning: A Fascinating Method for the Preparation of Ultrathin Fibers

An easy approach to control the carbon nanotube (CNT) array selectivity on Si/SiO2 in the floating chemical vapor deposition (CVD) method by adjusting the operation temperature is demonstrated. Aligned CNTs can be obtained directly on Si using a standard procedure at a relatively low temperature. After analyzing the temperature influence on different substrates, an attempt to grow an ultra-long CNT forest at the optimized temperature and without any feedstock diffusion limitation is discussed.

Temperature effect on the substrate selectivity of carbon nanotube growth in floating chemical vapor deposition

The confined growth of double-walled carbon nanotubes in porous catalysts by chemical vapor deposition

The crystallographic pore sizes of zeolites are substantially smaller than those inferred from catalytic transformation and molecular sieving capabilities, which reflects flexible variation in zeolite opening pores. Using in situ electron microscopy, we imaged the straight channels of ZSM-5 zeolite with benzene as a probe molecule and observed subcell flexibility of the framework. The opening pores stretched along the longest direction of confined benzene molecules with a maximum aspect change of 15%, and the Pnma space group symmetry of the MFI framework caused adjacent channels to deform. This compensation maintained the stability and rigidity of the overall unit cell within 0.5% deformation. The subcell flexibility originates mainly from the topologically soft silicon-oxygen-silicon hinges between rigid tetrahedral SiO4 units, with inner angles varying from 135° to 153°, as confirmed by ab initio molecular dynamics simulations. Description Benzene stretches zeolite channels The pores of zeolites allow for selective adsorption of molecules based on their size and shape. The pore sizes that are calculated based on their structure are smaller than what is expected from their absorption and chemical reaction properties, which implies that the frameworks must have inherent flexibility. Xiong et al. used environmental transmission electron microscopy to image the straight channels of ZSM-5 zeolite with adsorbed benzene (see the Perspective by Willhammar and Zou). The pores stretched along the longest direction of the confined benzene molecules by up to 15%. This large change was compensated for by adjacent channels so that the overall deformation of the original unit cells was less than 0.5%. —PDS Transmission electron microscopy reveals that benzene stretches channels of ZSM-5 zeolite and deforms empty adjacent channels.

Weizhong Qian

Papers

Temperature effect on the substrate selectivity of carbon nanotube growth in floating chemical vapor deposition

The confined growth of double-walled carbon nanotubes in porous catalysts by chemical vapor deposition

In situ imaging of the sorption-induced subcell topological flexibility of a rigid zeolite framework

High-yield production of aromatics from methanol using a temperature-shifting multi-stage fluidized bed reactor technology

Ionic liquid coated single-walled carbon nanotube buckypaper as supercapacitor electrode