[PDF] Performance Of Aqueous Ion Solution Tube Super Dielectric Material Based Capacitors As A Function Of Discharge Time eBook
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The discharge time dependence of key parameters of electrostatic capacitors employing a dielectric composed of the oxide film formed on titanium via anodization, saturated with various aqueous ion solutions, that is tube-super dielectric materials (T-SDM), was thoroughly documented for the first time. The capacitance, dielectric constant, and energy density of novel paradigm supercapacitors (NPS) based on T-SDM saturated with various concentrations of NaNO3, NH4Cl, or KOH were all found to roll-off with decreasing discharge time in a fashion well described by simple power law relations. In contrast, power density, also well described by a simple power law, was found to increase with decreasing discharge time, in fact nearly reaching 100 W/cm3 for both 30 wt% KOH and NaNO3 solution-based capacitors at 0.01 s, excellent performance for pulsed power. For all capacitors, the dielectric constant was tested, which was greater than 105 for discharge times >0.01 s, confirming the materials are in fact T-SDM. The energy density for most of the capacitors was greater than 80 J/cm3 of dielectric at a discharge time of 100 s, once again demonstrating that these capacitors are competitive for energy storage not only with existing commercial supercapacitors but also with the best prototype carbon-based supercapacitors.
This edited volume Supercapacitors: Theoretical and Practical Solutions is a collection of reviewed and relevant research chapters, offering a comprehensive overview of recent developments in the field of electronic devices and materials. The book comprises single chapters authored by various researchers and is edited by a group of experts. Each chapter is complete in itself but united under a common research study topic. This publication aims at providing a thorough overview of the latest research efforts by international authors on electronic devices and materials and opens new possible research paths for further novel developments.
This book provides a comprehensive overview of the latest developments and materials used in electrochemical energy storage and conversion devices, including lithium-ion batteries, sodium-ion batteries, zinc-ion batteries, supercapacitors and conversion materials for solar and fuel cells. Chapters introduce the technologies behind each material, in addition to the fundamental principles of the devices, and their wider impact and contribution to the field. This book will be an ideal reference for researchers and individuals working in industries based on energy storage and conversion technologies across physics, chemistry and engineering. FEATURES Edited by established authorities, with chapter contributions from subject-area specialists Provides a comprehensive review of the field Up to date with the latest developments and research Editors Dr. Mesfin A. Kebede obtained his PhD in Metallurgical Engineering from Inha University, South Korea. He is now a principal research scientist at Energy Centre of Council for Scientific and Industrial Research (CSIR), South Africa. He was previously an assistant professor in the Department of Applied Physics and Materials Science at Hawassa University, Ethiopia. His extensive research experience covers the use of electrode materials for energy storage and energy conversion. Prof. Fabian I. Ezema is a professor at the University of Nigeria, Nsukka. He obtained his PhD in Physics and Astronomy from University of Nigeria, Nsukka. His research focuses on several areas of materials science with an emphasis on energy applications, specifically electrode materials for energy conversion and storage.
The storage of electrical charge in electrochemical double layer capacitors (EDLCs) is ideal for short-term energy storage in stationary and mobile or portable applications in which intermittent power demands and reliability are of prime importance. A significant limitation of the currently employed EDLC technology is the low energy density, whereby a promising approach towards increasing the energy content of present EDLC systems is a widening of the operational voltage window. However, a significant reduction of the device lifetime is observed under elevated voltage conditions. In the present work, the contribution of interfacial charge transfer towards charge storage in and aging of EDLCs based on non-aqueous electrolyte solutions at elevated voltages is considered. The possible charge transfer mechanisms are thus conveniently classified as ionic or electronic. Through an improved understanding of these processes, possible routes for optimizing charge storage and avoiding aging at elevated voltages may be developed. A coconut shell derived activated carbon was selected as electrode material in non-aqueous solutions of 1 M Et4NBF4 in acetonitrile (AN) and in propylene carbonate (PC). Through an electrochemical characterization of these systems via cyclic voltammetry, the potential regions of essentially ideal polarizability could be identified and separated from the regions in which irreversible charge transfer took place. The region of ideal polarizability was characterized by in situ Raman spectroscopy, electrical resistance measurements and electrochemical dilatometry. The results are discussed in the context of those obtained on single-walled carbon nanotubes (SWCNTs) in order to establish a comparison with a high surface area electrode material of well-defined geometric and electronic structure. Fundamental differences in the reversible doping behavior of the two materials were observed, indicating that a conceptual representation of the carbonaceous framework of the activated carbon must take into account the presence of significant disorder and deviations from the idealized assembly of graphene fragments. Differences in the capacitive charging behavior could be attributed to the different electronic density of states of the materials, thus highlighting the importance of the electronic structure of carbonaceous electrodes for the storage of charge in EDLCs. In order to investigate the possibility of ionic charge transfer in EDLC systems, the contribution of ion insertion processes to the charge storage and electrode degradation of both graphitic and activated carbon electrodes was studied using in situ electrochemical dilatometry, X-ray diffraction and small-angle X-ray scattering. It was found that the insertion of ions into graphite proceeds via well-defined intercalation sites, with the electrochemical intercalation of BF4– leading to staging and solvent cointercalation for both AN- and PC-based electrolytes. Further, the crystallinity of the graphitic electrodes was found to degrade markedly in the direction perpendicular to the graphene sheets, which could largely be attributed to the electrochemical decomposition of intercalated electrolyte species, i.e. a combination of ionic and electronic charge transfer. On the the other hand, ion insertion processes in activated carbon could be attributed to the accumulation of ions within the confined insertion sites offered by micropores during charging. The steric requirements of these ions result in a macroscopically observable, reversible electrode expansion. A comparison with the expansion of entangled SWCNT electrodes and an expanded graphite electrode proved that the occupation of insertion sites depends directly on the electrode potential and the accessibility of the insertion site. As a particular example of this behavior, it was shown that the interstitial porosity of SWCNT bundles can be made accessible by electrochemical polarization, leading to an intrinsic capacitance enhancement. As an important conclusion, the accessibility of such sites must be evaluated in situ in order to determine their possible contribution to charge storage within the stability limits of the electrolyte solution. Studies of the electronic charge transfer contribution towards the aging of EDLCs in the present work emphasized the possible formation of insoluble solid electrolyte degradation products. Systematic aging experiments using laboratory-scale test cells at elevated voltages enabled to distinguish between the loss of electrochemical performance and physicochemical modification of the activated carbon electrodes on the single electrode level. The rapid rate of aging at elevated voltages was found to depend notably on the solvent. In the AN-based electrolyte solution, the performance loss at a cell voltage of 3.5 V could be primarily attributed to the blockage of porosity at the positive electrode by the formation of solid degradation products within the porous structure of the activated carbon, most likely due to the oxidation of AN. This aging mechanism is promoted by the defluorination of the polymeric binder at the negative electrode, which results in unfavorable potential window shifts during aging. Preliminary studies regarding aging in the PC-based electrolyte indicated a different primary aging mechanism, likely due to reductive processes involving PC at the negative electrode. Notably, the detrimental effects of electrolyte degradation on the EDLC performance appeared to be significantly more pronounced than the contribution of ion insertion processes to aging. Finally, suggestions for future research are made in order to deepen and exploit the insights gained regarding the insertion of ions in carbonaceous electrodes as well as the aging of EDLCs at elevated voltages. Patrick Ruch was born in Atlanta, USA, in 1981 and studied Materials Science at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland, followed by a dissertation at the Paul Scherrer Institut in the field of electrochemical energy storage. His academic and scientific efforts have been rewarded with the Willi Studer Prize of the ETH Zurich (2005), the Empa Research Award (2005), the Alu-Award of the Swiss Aluminium Association (2006) and the Young Author Award of the Oronzio and Niccolò De Nora Foundation (2008). The research interests of Dr. Ruch include materials engineering, renewable energy as well as energy conversion and storage.
In general, a dielectric is considered as a non-conducting or insulating material (such as a ceramic or polymer used to manufacture a microelectronic device). This book describes the laws governing all dielectric phenomena. · A unified approach is used in describing each of the dielectric phenomena, with the aim of answering "what?", "how?" and "why" for the occurrence of each phenomenon;· Coverage unavailable in other books on ferroelectrics, piezoelectrics, pyroelectrics, electro-optic processes, and electrets;· Theoretical analyses are general and broadly applicable;· Mathematics is simplified and emphasis is placed on the physical insight of the mechanisms responsible for the phenomena;· Truly comprehensive coverage not available in the current literature.
With its inclusion of the fundamentals, systems and applications, this reference provides readers with the basics of micro energy conversion along with expert knowledge on system electronics and real-life microdevices. The authors address different aspects of energy harvesting at the micro scale with a focus on miniaturized and microfabricated devices. Along the way they provide an overview of the field by compiling knowledge on the design, materials development, device realization and aspects of system integration, covering emerging technologies, as well as applications in power management, energy storage, medicine and low-power system electronics. In addition, they survey the energy harvesting principles based on chemical, thermal, mechanical, as well as hybrid and nanotechnology approaches. In unparalleled detail this volume presents the complete picture -- and a peek into the future -- of micro-powered microsystems.
The first model for the distribution of ions near the surface of a metal electrode was devised by Helmholtz in 1874. He envisaged two parallel sheets of charges of opposite sign located one on the metal surface and the other on the solution side, a few nanometers away, exactly as in the case of a parallel plate capacitor. The rigidity of such a model was allowed for by Gouy and Chapman inde pendently, by considering that ions in solution are subject to thermal motion so that their distribution from the metal surface turns out diffuse. Stern recognized that ions in solution do not behave as point charges as in the Gouy-Chapman treatment, and let the center of the ion charges reside at some distance from the metal surface while the distribution was still governed by the Gouy-Chapman view. Finally, in 1947, D. C. Grahame transferred the knowledge of the struc ture of electrolyte solutions into the model of a metal/solution interface, by en visaging different planes of closest approach to the electrode surface depending on whether an ion is solvated or interacts directly with the solid wall. Thus, the Gouy-Chapman-Stern-Grahame model of the so-called electrical double layer was born, a model that is still qualitatively accepted, although theoreti cians have introduced a number of new parameters of which people were not aware 50 years ago.
Materials for Supercapacitor Applications provides a snapshot of the present status of this rapidly growing field. It covers motivations, innovations, ongoing breakthroughs in research and development, innovative materials, impacts, and perspectives, as well as the challenges and technical barriers to identifying an ideal material for practical applications. This comprehensive reference by electro-chemists explains concepts in materials selection and their unique applications based on their electro-chemical properties. Chemists, chemical and electrical engineers, material scientists, and research scholars and students interested in energy will benefit from this overview of many important reference points in understanding the materials used in supercapacitors. Provides an overview of the formulation for new materials and how to characterize them for supercapacitor applications Describes all the information on the available materials for supercapacitor applications Outlines potential material characterization methods Discusses perspectives and future directions of the field
Making innovative products for energy generation that decrease carbon footprints are the need of the hour. This book describes innovations in porous materials for energy generation and storage applications that can have applications in developed as well as developing countries. It provides a comprehensive account of porous materials for potential new applications, such as catalysts for gas storage and energy efficient transformations, which engineers and scientists working in the areas of solar cells, batteries, supercapacitors, fuel cells, etc. will find to be of immense interest.