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Chang, Xiao. "Supercapacitor based energy storage system." Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25509.
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The supercapacitor, as a recently developed electrochemical energy storage device, offers extremely high capacitance per unit volume. Due to its unique double-layer structure and electrostatic charge mechanism, the supercapacitor has a much higher power density than the battery, and a much higher energy density than the conventional capacitor. It also benefits from a long cycle life, and wide temperature range. However, limited by a low cell voltage of 2.7V and high equivalent series resistance, the supercapacitor may be inefficient for high power grid level applications. Characteristic analysis of the supercapacitor shows that the efficiency reduces to 54.7% at peak current conditions. Based on supercapacitor modelling studies, two parameter identification methods are proposed, which are realised by a simple experiment, with an acceptable accuracy. A parallel combined supercapacitor and electrolytic capacitor energy storage system is proposed to improve high power application performance, which offers efficiency improvements in excess of 10%. A detailed description of such parallel capacitor systems are included in this thesis, where a design guide is developed to achieve an optimal design in terms of system efficiency, power capability, and volume. The capacitor based energy storage technique is suited to distributed generation applications where low-voltage ride through and grid code compliance are important considerations. A supercapacitor based static synchronous compensator is proposed, which is able to manipulate both active and reactive power exchange with the power system. Steady-state and transient responses are studied based on simulation of a test power system. A system frequency based control algorithm is used for active power control, which has a better stabilised system frequency than with conventional voltage control. The parallel hybrid capacitor technique is employed, which greatly improves the system performance in terms of efficiency, thermally, costs, and volume, compared with a system that only uses supercapacitors.
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Srithorn, Phinit. "Control of a statcom with supercapacitor energy storage." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/13839/.
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STATCOM (STATic COMpensator) has been used in electrical power systems as a shunt-connected compensator for voltage support and to improve power quality. Compared with the conventional compensators such as the synchronous condenser and the SVC (Static Var Compensator), the STATCOM has a faster speed of response to deal with dynamic and transient impacts. Although the STATCOM is capable of reactive power support to improve power quality, the ability to support real power is limited due to the insufficient energy storage capability of the conventional DC-link capacitor. Therefore, the application of the STATCOM to improving power system stability has been limited. This thesis proposes a solution to enhance the performance of the STATCOM by adding supercapacitor energy storage to the DC-link of the conventional STATCOM. With the fast charge/discharge characteristics of the supercapacitors, the enhanced STATCOM can absorb and inject real power to the ac power grid virtually instantaneously. The control design of the STATCOM based on a vector control strategy is presented, including the design of an instantaneous reactive power controller based on a small-signal model of the ac power system. The control design of the supercapacitor energy storage system (SCESS) based on small-signal models of the de-to-de converter is documented. The STATCOM and the SCESS are controlled together using a feed-forward control technique. In addition, this thesis also proposes that the enhanced STATCOM can be applied to reduce instability and tripping due to the rate of change of frequency (ROCOF) protection devices caused by large load impacts. The amount of the energy required for the enhanced STATCOM to maintain the stability of the system is also discussed.
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Yang, Hao. "Graphene-based Supercapacitors for Energy Storage Applications." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1376918924.
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Wang, Chaojun. "Graphene composites for fiber supercapacitors." Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/22363.
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Fiber supercapacitors (FSCs) are promising energy storage devices for emerging wearable electronics due to their unique advantages, such as good flexibility, weaveability and integratablity. Graphene materials with high surface area and excellent conductivity have been explored as electrode materials for fabricating FSCs. However, there are some many challenges to be resolved before they can be used in practical devices. This thesis focuses on three critical issues. First, when graphene materials are assembled as graphene hydrogel fibers, they shrink significantly during drying accompanied by complex internal structural transforms, which affect their energy storage performance significantly. However, the vital drying process has been largely ignored in previous studies. Second, when assembling graphene nanosheets into graphene electrodes, they often stack together uncontrollably due to strong van der Waals interactions between adjacent nanosheets, which significantly compromise their energy storage performance, This phenomenon has limited the applications of graphene fibers, even though they have high theoretical specific capacitance. Third, although graphene material based electrodes often deliver high power and long cycle life, their energy storage capacity based on the electrochemical double-layer capacitance is often limited. How to efficiently incorporate pseudocapacitive materials into graphene fibers to increase energy storage density is still unclear. To address these three issues, first, a comprehensive study was conducted to investigate the effects of drying conditions of graphene fibers on their porous structures and electrochemical properties. Graphene fibers were dried systematically under five different representative drying conditions. It was found that (1) the d-spacing of graphene nanosheets is determined during their reduction in hydrothermal assembly; (2) pore structures of dried graphene fibers are significantly influenced by solvent removal rates during drying; (3) the interconnection of pores in graphene fibers can be retained if non-volatile solvents are trapped in hydrogel fibers and (4) the graphene fibers dried under different conditions show significantly different specific volumetric capacitance and rate capability in capacitive energy storage. These findings can guide the synthesis of 1D fibers from 2D materials for FSCs and beyond. Second, a 2D-covalent organic framework (2D-COF) with a thickness of around 2 nm was explored as a nano-spacer to prevent the stacking of reduced graphene oxide (rGO) nanosheets during their assembly. The 2D-COF was selected because its mesopores can serve as an efficient “highway” for ion diffusion. The rGO/COF hybrid delivered a high gravimetric capacitance of 321 F g–1, corresponding to an ultrahigh graphene utilization rate (74%) related to theoretical gravimetric capacitance of graphene. Further, its practical applications were demonstrated in both thin-film supercapacitors and FSCs. They delivered a high specific energy density of 10.3 Wh kg−1 (thin-film supercapacitors) or 7.9 mWh cm−3 (FSCs), respectively. The 2D-COF shows good potential to enhance the energy storage performance of graphene or other 2D materials. Third, a novel method was demonstrated to uniformly incorporate ruthenium oxide (RuO2) nanoparticles with an ultra-high mass loading of 42.5 wt.% into holey graphene oxide (HGO) fibers. The HGO fibers were first prepared by the hydrothermal assembly. Next, Ru3+ ions were incorporated into wet HGO fibers before drying. The resulting composite fibers exhibited an ultrahigh volumetric capacitance of 1054 F cm−3. Solid-state FSCs fabricated by these fibers showed an ultrahigh energy density of 27.3 mWh cm−3. This method has the general applicability to incorporate different pseudocapacitive materials into graphene fibers to increase their energy storage capacity. Forth, to further increase the electrical conductivity of hybrid fibers containing pseudocapacitive materials, a core-sheath fiber comprised of a graphite fiber core and a MoS2 nanosheet intercalated HGO sheath was designed and synthesized by the hydrothermal assembly. MoS2 was selected due to its high pseudocapacitance and conductivity. The graphite fiber core served as a faster electron transfer highway. The core-sheath fiber showed a high volumetric capacitance up to 421 F cm−3. It was found that more than half of the capacitance of the fiber can be retained when the scan rate increases from 2 to 100 mV s–1. The assembled solid-state FSC delivered a high energy density of 8.2 mWh cm−3 at the power density of 40 mW cm−3. Overall, this thesis has provided new fundamental understandings of the assembly of graphene materials. Several innovative methods were demonstrated to produce high-performance graphene-based electrodes for FSCs. These results will help to realize of various potential practical applications of FSCs based on graphene materials
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Ghosh, Sujoy. "EFFECT OF 1-PYRENECARBOXYLIC ACID SURFACE FUNCTIONALIZATION OF GRAPHENE ON CAPACITIVE ENERGY STORAGE." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/656.
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In this work we have investigated supercapacitor electrodes prepared from pure and 1-pyrenecarboxylic acid (PCA)-functionalized graphene flakes obtained from liquid phase chemical exfoliation method. The performances of the supercapacitor devices fabricated using the graphene electrodes were tested using cyclic voltammetry, constant current charging-discharging and by electrochemical impedance spectroscopy (EIS) The specific capacitances obtained (using 6M KOH aqueous solution as an electrolyte) were found to be ~ 30 F/g and ~ 200 F/g for pure graphene and PCA functionalized graphene electrodes respectively. A comprehensive understanding of the effect of surface fictionalization on the electrochemical double layer capacitance was obtained in the light of equivalent circuit modeling and EIS data analysis. Information obtained from the EIS spectrum analysis revealed the possibility of occurrence of pseudocapacitance due to the presence of surface functional groups on the graphene flakes. Further, the wettability by KOH significantly increases upon functionalizing the graphene surfaces. These results shows PCA functionalized graphene membrane electrodes have the potential for high performance as supercapacitor electrode material.
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Källquist, Ida. "Lithium titanium oxide materials for hybrid supercapacitor applications." Thesis, Uppsala universitet, Strukturkemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-301977.
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The objective of this thesis was to investigate the suitability of some different Li4Ti5O12 materials as a negative electrode in hybrid supercapacitors. A hybrid supercapacitor is a combination of a battery and an electric double-layer capacitor that uses both a battery material and a capacitor material in the same device. The target for these combination devices is to bridge the performance gap between batteries and capacitors and enable both high energy and power density. To achieve this, materials with high capacity as well as high rate capability are needed. To improve the rate of the commonly slow battery materials nanosizing has been found to be an effective solution. This study shows that Li4Ti5O12 has a significantly higher experimental capacity than the most common capacitor material, activated carbon. The capacity remained high even at high discharge rates due to a successful nanostructuring that increased the accessibility of the material and shortened the diffusion distance for the ions, leading to a much improved power performance compared with the bulk material. The use of a nanostructured Li4Ti5O12 material in a hybrid device together with activated carbon was estimated to double the energy density compared to an electric double-layer capacitor and maintain the same good power performance. To further increase the energy density also improved materials for the positive electrode should be investigated.
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Jiang, Meng. "Processing and properties of nanostructured thin film energy storage devices." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:e651c635-6d92-4217-8442-43b2619c9c82.
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A spray deposition manufacturing route has been developed for the fabrication of carbon nano-structured and micro-structured energy storage devices in a thin film format, with controlled film thickness, homogeneous film surface morphology and high electrochemical performance for both supercapacitors and lithium ion battery anodes. Three types of low cost commercially available carbon materials (graphite, activated carbon and carbon black) have been investigated, and electrodes characterised in terms of surface morphology, surface chemistry, microstructure and electrochemical properties. By using ball milling, CO2 activation and adding suitable carbon conductive additives, nano-graphite-based film electrodes (one meter long and ~ 3 µm thickness) have been fabricated, with excellent ion transport and low electrical resistance (< 1.8 Ω). Specific capacitance of 110 F/g at a scan rate of 100 mV/s in 1 M H2SO4 was achieved. The high rate performance of activated carbon-based electrodes ( ~2 µm thickness) has been enhanced by reducing the contact resistance of electrode/current collector interface and building a well-interconnected and hierachical meso/macro-porous structure. A specific capacitance of over 120 F/g at a scan rate of 600 mV/s or 20 A/g current density in 1 M H2SO4 was achieved. The performance of carbon black-based electrodes (~4 µm thickness) in different electrolytes has been studied in both two- and three-electrode cells. High specific capacitances of 260 F/g at 1 A/g was achieved in 6 M KOH, together with energy and power densities of 21 kW/kg and 18 Wh/kg in 1 M Na2SO4. Finally, graphite-based electrodes for rechargeable lithium-ion batteries have also been fabricated with controlled film thickness from ~ 900 nm to ~ 40 µm and 98% capacity retention of 371 mA/g after 20 cycles. Spray deposition has been demonstrated to have the potential for scalability in the manufacture of carbon-based thin film electrodes with competitive properties.
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Tevi, Tete. "Enhancement of Supercapacitor Energy Storage by Leakage Reduction and Electrode Modification." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6148.
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Supercapacitors have emerged in recent years as a promising energy storage technology. The main mechanism of energy storage is based on electrostatic separation of charges in a region at the electrode-electrolyte interface called double layer. Various electrode materials including carbon and conducting polymers have been used in supercapacitors. Also, supercapacitors offer high life cycle and high power density among electrochemical energy storage devices. Despite their interesting features, supercapacitors present some disadvantages that limit their competitivity with other storage devices in some applications. One of those drawbacks is high self-discharge or leakage. The leakage occurs when electrons cross the double layer to be involved in electrochemical reactions in the supercapacitor’s electrolyte. In this work, the first research project demonstrates that the addition of a very thin blocking layer to a supercapacitor electrode, can improve the energy storage capability of the device by reducing the leakage. However, the downside of adding a blocking layer is the reduction of the capacitance. A second project developed a mathematical model to study how the thickness of the blocking layer affects the capacitance and the energy density. The model combines electrochemical and quantum mechanical effects on the electrons transfer responsible of the leakage. Based on the model, a computational code is developed to simulate and study the self-discharge and the energy loss in hypothetical devices with different thicknesses of the blocking layer. The third research project identified the optimal amount of a surfactant (Triton-X 100) that had a significant effect on the double layer capacitance and conductivity of a spin-coated PEDOT:PSS (poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)) electrode. The effect of the concentration of the surfactant was investigated by measuring the electrochemical properties and the conductivity of different electrodes. The electrodes were fabricated with different concentrations of the surfactant. Scanning electron microscopy characterizations confirmed the structural change in the PEDOT:PSS that contributed to the capacitance and conductivity enhancement. A final research project proposed an approach on how to utilize the modified PEDOT:PSS added to different photoactive dyes to design a photoactive supercapacitor. The new approach showed the possibility of using a supercapacitor device as an energy harvesting as well as a storage device.
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Agbedahunsi, Alex Taiwo. "Frequency control for microgrids using enhanced STATCOM and supercapacitor energy storage." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13307/.
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The face of electricity generation, transmission and distribution is changing due to economic, technology and environmental incentives. Recently, interactive and intelligent electricity grid structures which consist of interconnected small/medium sized generators, power electronic technologies and energy storage elements have been developed to address the major shortcomings of the traditional electricity grid structure. Microgrids are key elements of these emerging grid structures. Although microgrids are accepted as possible solutions to power quality and power stability issues in ac power systems, the uncertainty in the ability of microgrids to cope with severe fluctuating load and fault conditions is a major concern in the operation of these new grid structures. This project was aimed at improving frequency control within a microgrid. Four objectives were identified and addressed to meet this aim. I. A weak microgrid network using an emulated internal combustion engine generator and associated loads was modelled. The emulation of a diesel generating set was achieved with a vector controlled induction motor driving a synchronous generator. The diesel engine emulation was achieved by incorporating a single delay into the speed control loop of the vector controlled induction motor. The modelled microgrid network is a very useful tool for the development of novel control schemes for frequency control within a microgrid. II. Simulation studies were carried out to investigate how a weak power system can be strengthened through the use of enhanced STATCOM and Supercapacitor energy storage. This assisted in understanding the limitations and performances of the novel algorithms proposed for frequency control improvement. III. Novel open and closed loop control algorithms for frequency control within a microgrid were proposed. The advantage of the open loop control scheme is its simplicity but the functionality of the control action is limited with the knowledge of the diesel engine transfer function and load current being important requirements. A closed loop control scheme was employed to address the limitations of the open loop control scheme. IV. A laboratory prototype of the microgrid network was developed and used in validating the novel control schemes proposed. The thesis describes the novel algorithms for frequency control using an intelligent STAtic COMpensator (STATCOM) and SuperCapacitor Energy Storage System (SCESS). The benefits and effectiveness of the proposed algorithms are given in the simulation and experimental results.
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Kulsangcharoen, Ponggorn. "Characterization and emulation of a new supercapacitor-type energy storage device." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13143/.
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The work in this thesis focuses on the characterization, modeling and emulation of both the supercapacitor and the new supercapattery energy storage device. The characterization involves the selection of dynamic models and experimental methodologies to derive model parameters. The characterizing processes focus on predicting short-term device dynamics, energy retention (self-discharging) and losses and round-trip efficiency. A methodology involving a pulse current method is applied for the first time to identify a model parameter to give fast device dynamic characteristics and a new constant power cycling method is used for evaluating round-trip efficiency. Experimental results are shown for a number of supercapacitor and supercapattery devices and good results are obtained. The derived models from the characterization results are implemented into the emulator system and the emulator system is used to mimic the dynamic characteristics of a scaled-up 1kW supercapattery device. The thesis also addresses voltage equalizing circuits and reports a study that investigates efficiency, a cell voltage deviation and voltage equalizing time for different control methods.
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Faisal, Shaikh Nayeem. "Nanomaterials Embedded Nitrogen-Doped Graphene for Advanced Energy Storage and Conversion." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/16795.
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A facile synthesis of nitrogen-doped graphene with high atomic percentage of Nitrogen (9.2 at%) including high ratio of pyridinic N and graphitic N has been reported via thermal annealing of graphene oxide with uric acid. The resultant material shows efficient electrochemical properties for capacitances and bifunctional electrocatalysis of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In spite of its remarkable electrochemical properties, the major limitation of the two-dimensional graphene like materials for device fabrication or commercial applications is the restacking nature of the layers. Designing a three-dimensional nanostructure via inserting metal nanoparticles or one-dimensional carbonaceous nanomaterials inside the graphene layers can prevent the restacking of the layers and hence enhance the electrochemical properties of the composites by providing higher electroactive surface area for electrolyte permeation, charge storage as well as active sites for electrocatalysis. To enhance the electrocatalytical activity of the synthesized nitrogen-doped graphene, a hybrid of nickel embedded nitrogen-doped graphene is developed. The composite shows superior noble-metal-free quadrafunctional electrocatalysis of oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER) and hydrogen peroxide oxidation reaction (HPOR) compared to commercial electrocatalysts of Pt/C and Ru/C. Alternatively, the insertion of carbon nanotubes inside the graphene layers and fabricating a lamellar three-dimensional nanostructure exhibit excellent supercapacitor behavior as fabricated as solid-state supercapacitor and high-rate capable anode for Li-ion battery as well as metal-free bifunctional electrocatalysis of ORR and OER. In addition, the decoration of copper nanoparticles in the three-dimensional nanostructured nitrogen-doped graphene/carbon nanotube composite further improves the conductivity and electrochemical properties via interconnecting network of copper nanoparticles and carbon nanotubes with the graphene layers and have been evaluated for high performance metal-ion battery applications. The resultant composites show promising electrochemical performances for developing as electrode materials for next generation energy storage and conversion devices like solid-state supercapacitor, metal-ion battery, metal-air battery and rechargeable fuel cells.
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Lin, Ziyin. "Functionalized graphene for energy storage and conversion." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51871.
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Graphene has great potential for energy storage and conversion applications due to its outstanding electrical conductivity, large surface area and chemical stability. However, the pristine graphene offers unsatisfactory performance as a result of several intrinsic limitations such as aggregation and inertness. The functionalization of graphene is considered as a powerful way to modify the physical and chemical properties of graphene, and improve the material performance, which unfortunately still being preliminary and need further knowledge on controllable functionalization methods and the structure-property relationships. This thesis aims to provide in-depth understanding on these aspects. We firstly explored oxygen-functionalized graphene for supercapacitor electrodes. A mild solvothermal method was developed for graphene preparation from the reduction of graphene oxide; the solvent-dependent reduction kinetics is an interesting finding in this method that could be attributed to the solvent-graphene oxide interactions. Using the solvothermal method, oxygen-functionalized graphene with controlled density of oxygen functional groups was prepared by tuning the reduction time. The oxygen-containing groups, primarily phenols and quinones, reduce the graphene aggregation, improve the wetting properties and introduce the pseudocapacitance. Consequently, excellent supercapacitive performance was achieved.
Nitrogen-doped graphene was synthesized by the pyrolysis of graphene oxide with nitrogen-containing molecules and used as an electrocatalyst for oxygen reduction reactions. We achieved the structural control of the nitrogen-doped graphene, mainly the content of graphitic nitrogen, by manipulating the pyrolysis temperature and the structure of nitrogen-containing molecules; these experiments help understand the evolution of the bonding configurations of nitrogen dopants during pyrolysis. Superior catalytic activity of the prepared nitrogen-doped graphene was found, due to the enriched content of graphitic nitrogen that is most active for the oxygen reduction reaction.
Moreover, we demonstrated a facile strategy of producing superhydrophobic octadecylamine-functionalized graphite oxide films. The long hydrocarbon chain in octadecylamine reduces the surface energy of the graphene oxide film, resulting in a high water contact angle and low hysteresis. The reaction mechanism and the effect of hydrocarbon chain length were systematically investigated. In addition to the researches on graphene-based materials, some results on advanced carbon nanomaterials and polymer composites for electronic packaging will also be discussed as appendix to the thesis. These include carbon nanotube-based capacitive deionizer and gas sensor, and hexagonal boron nitride-epoxy composites for high thermal conductivity underfill.
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Yang, Hao. "Graphene-based Materials for Electrochemical Energy Storage." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1512095146429831.
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Nyström, Gustav. "Nanocellulose and Polypyrrole Composites for Electrical Energy Storage." Doctoral thesis, Uppsala universitet, Nanoteknologi och funktionella material, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-168664.
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To meet the predicted increase in demand for energy storage in tomorrow's society, the development of inexpensive, flexible, lightweight and sustainable energy-storage materials is essential. In this respect, devices based on electroactive organic molecules, such as conducting polymers, are highly interesting. The aim of this thesis was to evaluate the use of nanocellulose as a matrix material in composites of cellulose and the electroactive polymer polypyrrole (PPy), and the use of these composites in all-polymer paper-based energy-storage devices. Pyrrole was polymerized using FeCl3 onto cellulose nanofibers in the form of a hydrogel. The resulting PPy-coated fibers were washed with water and dried into a high surface area, conductive paper material. Variations in the drying technique provided a way of controlling the porosity and the surface area of wood-based cellulose nanofibers, as the properties of the cellulose were found to have a large influence on the composite structure. Different nanocellulose fibers, of algal and wood origin, were evaluated as the reinforcing phase in the conductive composites. These materials had conductivities of 1–6 S/cm and specific surface areas of up to 246 m2/g at PPy weight fractions around 67%. Symmetrical supercapacitor devices with algae-based nanocellulose-PPy electrodes and an aqueous electrolyte showed specific charge capacities of around 15 mAh/g and specific capacitances of around 35 F/g, normalized with respect to the dry electrode weight. Potentiostatic charging of the devices was suggested as a way to make use of the rapid oxidation and reduction processes in these materials, thus minimizing the charging time and the effect of the IR drop in the device, and ensuring charging to the right potential. Repeated charging and discharging of the devices revealed a 10–20% loss in capacity over 10 000 cycles. Upon up-scaling of the devices, it was found that an improved cell design giving a lower cell resistance was needed in order to maintain high charge and discharge rates. The main advantages of the presented concept of nanocellulose-PPy-based electrical energy storage include the eco-friendly raw materials, an up-scalable and potentially cost-effective production process, safe operation, and the controllable porosity and moldability offered by the nanocellulose fiber matrix. Integrating energy storage devices into paper could lead to un- precedented opportunities for new types of consumer electronics. Future research efforts should be directed at increasing the energy density and improving the stability of this type of device as well as advancing the fundamental understanding of the current limitations of these properties.
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Yu, Feng. "Design and synthesis of materials for supercapacitors with enhanced energy storage performance." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/205903/1/Feng_Yu_Thesis.pdf.
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This thesis aims to increase energy storage performance of supercapacitor devices by improving the energy density of supercapacitors without significantly compromising power density. Different strategies were used in this research, including using battery materials in place of electrodes, increasing the potential window of the supercapacitor, and employing soluble dual-redox additives. These strategies led to the discovery of several high power and high energy density energy-storage technology applications that have the promising potential to be commercialized.
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Zhang, Lu. "Study of Novel Graphene Structures for Energy Storage Applications." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479823012280305.
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Boukhalfa, Sofiane. "Studies of ion electroadsorption in supercapacitor electrodes." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52976.
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Electrochemical capacitors, now often termed supercapacitors, are high power electrochemical energy storage devices that complement or replace high power batteries in applications ranging from wind turbines to hybrid engines to uninterruptable power supplies to electronic devices. My dissertation explores the applications of relatively uncommon techniques for both supercapacitor material syntheses and gaining better mechanistic understanding of factors impacting electrochemical performance of supercapacitors. From fundamental ion electroadsorption studies made possible by using small angle neutron scattering (SANS), to the systematic investigations of coating thickness and microstructure in metal oxide / carbon nanocomposite electrodes realized through the novel use of the atomic layer deposition (ALD) technique, new avenues of material characterization and fabrication have been studied.
In this dissertation I first present the motivation to expand the knowledge of supercapacitor science and technology, and follow with an in-depth literature review of the state of the art. The literature review covers different types of supercapacitors, the materials used in the construction of commercial and exploratory devices, an exploration of the numerous factors which affect supercapacitor performance, and an overview of relevant materials synthesis and characterization techniques The technical objectives for the work performed in this dissertation are then presented, followed by the contributions that I made in this field in my two primary research thrusts: advances to the understanding of ion electroadsorption theory in both aqueous and organic electrolytes through the development of a SANS-based methodology, and advances to metal-oxide carbon nanocomposites as electrodes through the use of ALD.
The understanding of ion electro-adsorption on the surface of microporous (pores < 2 nm) solids is largely hindered by the lack of experimental techniques capable of identifying the sites of ion adsorption and the concentration of ions at the nanoscale. In the first research thrust of my dissertation, I harness the high penetrating power and sensitivity of neutron scattering to isotope substitution to directly observe changes in the ion concentration as a function of the applied potential and the pore size. I have conducted initial studies in selected aqueous and organic electrolytes and outlined the guidelines for conducting such experiments for the broad range of electrode-ions-solvent combinations. I unambiguously demonstrate that depending on the solvent properties and the solvent-pore wall interactions, either enhanced or reduced ion electro-adsorption may take place in sub-nanometer pores. More importantly, for the first time I demonstrate the route to identify the critical pore size below which either enhanced or reduced electrosorption of ions takes place. My studies experimentally demonstrate that poor electrolyte wetting in the smallest pores may indeed limit device performance. The proposed methodology opens new avenues for systematic in-situ studies of complex structure-property relationships governing adsorption of ions under applied potential, critical for rational optimization of device performance.
In addition to enhancing our understanding of ion sorption, there is a critical need to develop novel supercapacitor electrode materials with improved high-energy and high-power characteristics. The formation of carbon-transition metal oxide nanocomposites may offer unique benefits for such applications. Broadly available transition metal oxides, such as vanadium oxide, offer high ion storage capabilities due to the broad range of their oxidation states, but suffer from high resistivities. Carbon nanomaterials, such as carbon nanotubes (CNT), in contrast are not capable to store high ion content, but offer high and readily accessible surface area and high electrical conductivity. In the second research thrust of my thesis, by exploiting the ability of atomic layer deposition (ALD) to produce uniform coatings of metal oxides on CNT electrodes, I demonstrated an effective way to produce high power supercapacitor electrodes with ultra-high energy capability. The electrodes I developed showed stable performance with excellent capacitance retention at high current densities and sweep rates. Electrochemical performance of the oxide layers were found to strongly depend on the coating thickness. Decreasing the vanadium oxide coating thickness to ~10 nm resulted in some of the highest values of capacitance reported to date (~1550 F·g⁻¹VOx at 1 A·g⁻¹ current density). Similar methodology was utilized for the deposition of thin vanadium oxide coatings on other substrates, such as aluminum (Al) nanowires. In this case the VOₓ coated Al nanowire electrodes with 30-50% of the pore volume available for electrolyte access show volumetric capacitance of 1390-1950 F cc⁻¹, which exceeds the volumetric capacitance of porous carbons and many carbon-metal oxide composites by more than an order of magnitude. These results indicated the importance of electrode uniformity and precise control over conformity and thickness for the optimization of supercapacitor electrodes.
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Gee, Anthony. "Design and assessment of a battery-supercapacitor hybrid energy storage system for remote area wind power systems." Thesis, University of Bath, 2012. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.577732.
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Recent advances in innovative energy storage devices such as supercapacitors have made battery-supercapacitor hybrid energy storage systems technically attractive. However the field of hybrid energy storage system control is relatively new, involving the major challenge of developing control techniques optimised for improved battery-life or other performance metrics. This thesis presents the design and analysis of an actively controlled hybrid energy storage system. Detailed information is given regarding the system implementation and dynamic controls developed as a part of the research. Novel use of the sliding-mode or hysteretic current-controlled DC/DC converter is shown to provide a versatile and robust power electronic building block for the power-control hardware implementation. Current state of the art in the field has converged around a frequency-domain approach to the overall power sharing strategy within hybrid energy storage systems employing batteries and high-power, low-energy density storage such as supercapacitors, with benefits in terms of reduced battery current maxima and an (un-quantified) increase in battery life having been reported. This research extends previous studies by considering the frequency-domain approach in further detail and providing quantitative simulation results confirming how an estimated increase in battery cycle-life of ~18% can be achieved. A systematic simulation framework used for the development and assessment of novel hybrid energy storage system control strategies is described and demonstrated in the context of a remote wind power application. The hardware design of all systems considered is described in detail and demonstrated by experiment.
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Soltani, Paniz. "Synthesis of novel carbon materials for supercapacitor applications." Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22368.
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Mestrado em Química - Química Inorgânica e MateriaisMicro-supercapacitors (MSCs) are the key components of miniaturized, portable and wearable electronic devices. Although many advances have been made in this field during the recent years, micro-supercapacitors energy density remains far from those from lithium-ion batteries and electrolyte capacitors. Many efforts have been made to improve MSCs performances such as fabrication of nanostructures and thin-film manufacture technologies. Here, we demonstrated MSCs based on porous carbon and PEDOT: PSS polymer as well as RuO2 and electrochemically exfoliated graphene. Combining materials with pseudo capacitive and electrochemical double layer capacitance ability, the resulting MSCs deliver an area capacitance up to 1mFcm-2 and stack capacitance up to 51 Fcm-3 for graphene based devices and area capacitance up to 203 μFcm-2 and stack capacitance up to 12 Fcm-3 for polymer based devices. Both devices show ability to be operated in ultra-high rates up to 1000 Vs-1 which is around three orders of magnitude higher that of conventional batteries. The high capacitance is generally obtained at low scan rates (~ 10 mVs-1) and 40% of capacitance retention has been observed.
Micro-supercondensadores (MSCs) são os principais componentes de dispositivos eletrónicos miniaturizados, portáteis e utilizáveis no vestuário. Embora muitos avanços tenham sido feitos neste campo nos últimos anos, a densidade de energia dos micro-supercondensadores permanece aquém das baterias de iões de lítio e dos condensadores eletrolíticos. Muitos esforços foram feitos para melhorar os desempenhos dos MSCs, como e fabricação de nanoestruturas e as tecnologias de filmes finos. Neste trabalho estudam-se MSCs baseados em carbono poroso e PEDOT:PSS, bem como de RuO2 e grafeno electroquimicamente exfoliado. A combinação de materiais com capacitância de camada dupla pseudo-capacitiva e eletroquímica permite obter MSCs com uma capacitância até 1 mF.cm-2 e capacidade até 51 F.cm-3 nos dispositivos baseados em grafeno e capacitância até 203 μF.cm-2 e capacitância de 12 F.cm-3 nos dispositivos baseados em polímero. Ambos os dispositivos podem ser operados até 1000 V.s-1, um valor cerca de três ordens de grandeza maior do que o das baterias convencionais. A elevada capacitância foi obtida com baixas taxas de varrimento (~ 10 mV.s-1) com retenção de aproximadamente 40%.
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Chivers, Benjamin William. "Development of Novel PEDOT:PSS Fabrication Techniques for High Performance, Flexible RFID Antennas and Energy Storage Devices." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/20155.
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Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) has been widely studied as either nanometre-scale, transparent films or a conductive, capacitive composite material in electronic devices. While significant effort has been directed towards increasing PEDOT:PSS conductivity in transparent films, very little nanoscale, morphological consideration has been applied to micron-scale PEDOT:PSS materials. As a result, PEDOT:PSS conductivity often decreases in micron-scale materials, and the polymer has been largely overlooked as a high performance material in practical applications. In this thesis, PEDOT:PSS fabrication techniques are optimised to produce high conductivity and high electrochemical performance micron-scale quantities of PEDOT:PSS. The optimised PEDOT:PSS is used to fabricate an RFID antenna with extraordinary radiation efficiency, a high efficiency zinc/bromine flow battery anode, and an ultra-high performance composite-fibre-supercapacitor. A novel fabrication technique was developed to maintain PEDOT:PSS electrical and electrochemical performance in micron-scale applications. By submersion in ethylene glycol, PEDOT:PSS phase separation, conformational changes, stability and PEDOT loading were optimised for a commercially available PEDOT:PSS. Polymer films 40 m thick were reliably produced with over 500 S cm-1. The high performance PEDOT:PSS was fabricated into a 2.45 GHz RFID dipole antenna, achieving 99.7% peak radiation efficiency, a novel result for a non-metal antenna. The same morphologically considerate approach was applied to zinc/bromine flow battery anode design, more than doubling peak charge density. Energy density increased by over 50%, and charge efficiency increased by 9.3%, directly increasing battery efficiency. PEDOT:PSS was composited with reduced graphene oxide to produce a symmetric fibre supercapacitor with very high capacitance, 138 F cm-3 compared to 55 F cm-3 and 14 F cm-3 for PEDOT:PSS and rGO respectively.
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Cakici, Murat. "Highly flexible carbon fibre fabric based nanostructured hybrids for high performance energy storage systems." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/18123.
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Electrochemical supercapacitors (ES), or ultracapacitors, store energy using either reversible adsorption of electrolyte ions (electrochemical double layer capacitors) or fast surface redox reactions on its electrodes (pseuodocapacitors). Currently, they are used together with batteries or fuel cells when high-power delivery or uptake is required. They have exceptional features such as high power density, high cycle efficiency, fast charging-discharging rate, long lifecycle, and safe operation. Therefore, they have attracted tremendous interest as next generation energy conversion and storage systems, ranging from portable wearable electronics to hybrid electric vehicles. However, low energy density is the main drawback to use ES as a stand-alone energy storage system. Thus, their performance should be improved to fulfil the requirements of ever-growing energy demands of progressing global economy and industry. In addition, most of the ES electrodes are fabricated from powders which makes them unsuitable for their potential use as wearable lightweight flexible devices in the future. Considering the requirements of future industrial applications of ES, this thesis focuses on synthesizing high performance, flexible, mechanically stable, lightweight, eco-friendly, and low cost ES electrodes using green, scalable, and inexpensive fabrication methods. To develop highly efficient electrode materials suitable for practical applications in a flexible design, novel synthesis procedures were explored to incorporate pseudocapacitive materials (metal oxides and electrically conductive polymers) into three-dimensional and flexible conductive carbon materials to obtain multicomponent hybrid materials. Therefore, hybrid materials reported in this thesis are binder-/conductive agent-free and also have enhanced three-dimensional nanostructures which promote energy storage. Simplicity of the fabrication methods also enable large scale and economical production of flexible and mechanically stable materials which can be directly used as ES electrodes. First, electrode materials with a unique nanostructure was developed for supercapacitor applications based on carbon fibre fabric (CFF) / MnO2 hybrid materials, in which MnO2 was uniformly coated on the surface of CFF. A green hydrothermal method was used to functionalize CFF with coral-like MnO2 nanostructures to improve the electrochemical performance of the hybrid composites. The morphological, structural, and crystalline properties of composites were analysed by using various techniques to confirm the deposition of coral-like MnO2 on CFF. The electrochemical performance was examined in a three-electrode system and cyclic voltammetry results reveal the superior specific capacitance of 467 F g-1 at a scan rate of 5 mV s-1. The cycling performance test revealed that the capacitance retention was 99.7% and the coulombic efficiency remained as high as 99.3% after 5000 cycles, demonstrating an outstanding electrochemical stability of the coral-like MnO2/CFF composite electrode. Second, synthesis method used in the first study was optimised to obtain three novel nanostructured MnO2 layers on flexible CFF substrates. It was observed that different morphologies of MnO2 could be grown on carbon fibres by adjusting the concentration of precursor solution. The morphological, structural, and crystalline properties of the composites were analysed by using various techniques to confirm that MnO2 nanostructures were successfully anchored on CFF. The electrochemical performances of the nanostructured MnO2/CFF composites were examined in two-electrode symmetric cell configuration in 1 M Na2SO4 electrolyte. Among three different morphologies, nanoplate type MnO2/CFF electrode had the best electrochemical performance (528 F g-1 at 0.5 A g-1 current density). In addition, binder and conductive agent free, flexible MnO2/CFF composite electrode had excellent cycling stability and coulombic efficiency. Finally, activated CFF (ACFF) / reduced graphene oxide (RGO)/polyaniline (PANI) composite flexible electrodes were prepared by in-situ polymerization method. Polymerization of aniline was optimized by adjusting aniline concentration to obtain PANI nanowire arrays on the three-dimensional flexible carbon based substrate. Electrochemical performance of ACFF/RGO/PANI composite was compared with ACFF and ACFF/RGO electrodes in two-electrode symmetrical cell configuration in 1 M H2SO4 electrolyte. The results indicated that ACFF/RGO/PANI exhibited outstanding area normalized capacitance due to synergistic effect between ACFF, RGO, and PANI. The facile synthesis method of the composite electrode using textile based substrate enables the possibility for fabrication of high-performance flexible energy storage devices.
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Okafor, Patricia A. "Processing and Characterization of Graphene/Polyimide-Nickel Oxide Hybrid Nanocomposites for Advanced Energy Storage in Supercapacitor Applications." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479823253057854.
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Borgohain, Rituraj. "PHYSICOCHEMICAL MODIFICATIONS AND APPLICATIONS OF CARBON NANO-ONIONS FOR ELECTROCHEMICAL ENERGY STORAGE." UKnowledge, 2013. http://uknowledge.uky.edu/chemistry_etds/24.
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Carbon nano-onions (CNOs), concentrically multilayered fullerenes, are prepared by several different methods. We are studying the properties of two specific CNOs: A-CNOs and N-CNOs. A-CNOs are synthesized by underwater arc discharge, and N-CNOs are synthesized by high-temperature graphitization of commercial nanodiamond. In this study the synthesis of A-CNOs are optimized by designing an arc discharge aparatus to control the arc plasma. Moreover other synthesis parameters such as arc power, duty cycles, temperature, graphitic and metal impurities are controlled for optimum production of A-CNOs. Also, a very efficient purification method is developed to screen out A-CNOs from carboneseous and metal impurities. In general, A-CNOs are larger than N-CNOs (ca. 30 nm vs. 7 nm diameter). The high surface area, appropriate mesoporosity, high thermal stability and high electrical conductivity of CNOs make them a promising material for various applications. These hydrophobic materials are functionalized with organic groups on their outer layers to study their surface chemistry and to decorate with metal oxide nanoparticles. Both CNOs and CNO nanocomposites are investigated for application in electrochemical capacitors (ECs). The influences of pH, concentration and additives on the performance of the composites are studied. Electrochemical measurements demonstrate high specific capacitance and high cycling stability with high energy and power density of the composite materials in aqueous electrolyte.
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Falola, Bamidele Daniel. "TRANSITION METAL COATINGS FOR ENERGY CONVERSION AND STORAGE; ELECTROCHEMICAL AND HIGH TEMPERATURE APPLICATIONS." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/dissertations/1354.
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Energy storage provides sustainability when coupled with renewable but intermittent energy sources such as solar, wave and wind power, and electrochemical supercapacitors represent a new storage technology with high power and energy density. For inclusion in supercapacitors, transition metal oxide and sulfide electrodes such as RuO2, IrO2, TiS2, and MoS2 exhibit rapid faradaic electron–transfer reactions combined with low resistance. The pseudocapacitance of RuO2 is about 720 F/g, and is 100 times greater than double-layer capacitance of activated carbon electrodes. Due to the two-dimensional layered structure of MoS2, it has proven to be an excellent electrode material for electrochemical supercapacitors. Cathodic electrodeposition of MoS2 onto glassy carbon electrodes is obtained from electrolytes containing (NH4)2MoS4 and KCl. Annealing the as-deposited Mo sulfide deposit improves the capacitance by a factor of 40x, with a maximum value of 360 F/g for 50 nm thick MoS2 films. The effects of different annealing conditions were investigated by XRD, AFM and charge storage measurements. The specific capacitance measured by cyclic voltammetry is highest for MoS2 thin films annealed at 500°C for 3h and much lower for films annealed at 700°C for 1 h. Inclusion of copper as a dopant element into electrodeposited MoS2 thin films for reducing iR drop during film charge/discharge is also studied. Thin films of Cu-doped MoS2 are deposited from aqueous electrolytes containing SCN-, which acts as a complexing agent to shift the cathodic Cu deposition potential, which is much more anodic than that of MoS2. Annealed, Cu-doped MoS2 films exhibit enhanced charge storage capability about 5x higher than undoped MoS2 films. Coal combustion is currently the largest single anthropogenic source of CO2 emissions, and due to the growing concerns about climate change, several new technologies have been developed to mitigate the problem, including oxyfuel coal combustion, which makes CO2 sequestration easier. One complication of oxyfuel coal combustion is that corrosion problems can be exacerbated due to flue gas recycling, which is employed to dilute the pure O2 feed and reduce the flame temperature. Refractory metal diffusion coatings of Ti and Zr atop P91 steel were created and tested for their ability to prevent corrosion in an oxidizing atmosphere at elevated temperature. Using pack cementation, diffusion coatings of thickness approximately 12 and 20 µm are obtained for Ti and Zr, respectively. The effects of heating to 950°C for 24 hr in 5% O2 in He are studied in situ by thermogravimetric analyses (TGA), and ex situ by SEM analyses and depth profiling by EDX. For Ti-coated, Zr-coated and uncoated P91 samples, extended heating in an oxidizing environment causes relatively thick oxide growth, but extensive oxygen penetration greater than 2.7 mm below the sample surface, and eventual oxide exfoliation, are observed only for the uncoated P91 sample. For the Ti- and Zr-coated samples, oxygen penetrates approximately 16 and 56 µm, respectively, below the surface. In situ TGA verifies that Ti-and Zr-coated P91 samples undergo far smaller mass changes during corrosion than uncoated samples, reaching close to steady state mass after approximately four hours.
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Wang, Teng. "Nickel based nanomaterials for renewable energy conversion and storage application." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/119163/8/Teng_Wang_Thesis.pdf.
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This research focuses on the synthesis and development of new functional nanomaterials with tailored morphology for high performance supercapacitors and hydrogen generation through electrolysis of water splitting in order to alleviate the energy crisis and environmental problems. A series of nickel based nanomaterials have been synthesized and their electrochemical properties were thoroughly studied. Ultrafine amorphous barium nickel phosphate nanofibers, and Ni-Co and NiCu layered double hydroxide (LDH) nanosheet arrays directly grown on carbon fibre clothes (CFC) demonstrated excellent performance for supercapacitors while NiCoFe LDH nanosheet arrays on CFC showed high catalytic activity for oxygen evolution reaction for water splitting.
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Blumer, Ari Nathan. "Few-layer MoS2 Flakes and Carbon Quantum Dots as Supercapacitor Electrode Materials." Ohio University Honors Tutorial College / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1524839175902206.
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Li, Wenqi. "LIGNIN-DERIVED CARBON AND NANOCOMPOSITE MATERIALS FOR ENERGY STORAGE APPLICATIONS." UKnowledge, 2019. https://uknowledge.uky.edu/bae_etds/68.
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With a growing demand for electrical energy storage materials, lignin-derived carbon materials have received increasing attention in recent years. As a highly abundant renewable carbon source, lignin can be converted to a variety of advanced carbon materials with tailorable chemical, structural, mechanical and electrochemical properties through thermochemical conversion (e.g. pyrolysis). However, the non-uniformity in lignin structure, composition, inter-unit linkages and reactivity of diverse lignin sources greatly influence lignin fractionation from plant biomass, the pyrolysis chemistry, and property of the resulting carbon materials.
To introduce a better use of lignocellulosic biomass to biofuels and co-products, it is necessary to find novel ways to fractionate lignin and cellulose from the feedstock at high efficacy and low cost. Deep eutectic solvent (DES) was used to extract lignin from high lignin-content walnut and peach endocarps. Over 90% sugar yields were achieved during enzymatic hydrolysis of DES pretreated peach and walnut endocarps while lignins were extracted at high yields and purity. The molecular weights of the extracted lignin from DES pretreated endocarp biomass were significantly reduced. The native endocarp lignins were SGH type lignins with dominant G-unit. DES pretreatment decreased the S and H-unit which led to an increase in condensed G-units, which may contribute to a higher thermal stability of the isolated lignin.
Lignin slow pyrolysis was investigated using a commercial pyrolysis–GC/MS system for the first time to link pyrolysis chemistry and carbon material properties. The overall product distributions, including volatiles and solid product were tracked at different heating rates (2, 20, 40 ℃/min) and different temperature regions (100-200, 200-300 and 300-600 ℃). Results demonstrate that changes in reaction chemistry as a factor of pyrolysis conditions led to changes in yield and properties of the resulting carbon materials. Physical and chemical properties of the resulting carbon material, such as porosity, chemical composition and surface functional groups were greatly affected by lignin slow pyrolysis temperature and heating rate.
Lignin-derived activated carbons (AC) were synthesized from three different lignin sources: poplar, pine derived alkaline lignin and commercial kraft lignin under identical conditions. The poplar lignin-derived ACs exhibited a larger surface area and total mesopore volume than softwood lignin-derived AC, which contribute to a larger electrochemical capacitance over a range of scan rates. The presence of oxygen-containing functional groups in all lignin-derived ACs, which participated in redox reaction and thus contributed to an additional pseudo-capacitance. By delineating the carbonization and activation parameters, results from this study suggest that lignin structure and composition are important factors determining the pore structure and electrochemical properties of the derived carbon materials.
A 3-dimensional, interconnected carbon/silicon nanoparticles composite synthesized from kraft lignin (KL) and silicon nanoparticles (Si NPs) is shown to have a high starting specific capacity of 2932 mAh/g and a retaining capacity of 1760 mAh/g after 100 cycles at 0.72 A/g as negative electrode in a half-cell lithium-ion battery (LIB) test. It was found the elemental Si and C of the C/Si NPs were most likely linked via Si-O-C rather than direct Si-C bond, a feature that helps to alleviate the mechanical degradation from Si volume change and assure a sound electronic and ionic conductivity for enhanced electrochemical performance. EGA-MS and HC-GC/MS analyses suggest that the interaction of the Si, O and C can be tailored by controlling pyrolysis conditions.
This study systematically investigated the interconnecting aspects among lignin source, pyrolysis chemistry, characteristics of the derived carbon materials and electrochemical performance. Such knowledge on the processing-structure-function relationships serves as a basis for designing lignin-based carbon materials for electrochemical energy storage applications.
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Abass, Monsuru A. "Boron nitride nanotube-modified silicon oxycarbide ceramic composite: synthesis, characterization and applications in electrochemical energy storage." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/35423.
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Master of ScienceDepartment of Mechanical and Nuclear Engineering
Gurpreet Singh
Polymer-derived ceramics (PDCs) such as silicon oxycarbide (SiOC) have shown promise as an electrode material for rechargeable Li-ion batteries (LIBs) owing to the synergy between its disordered carbon phase and hybrid bonds of silicon with oxygen and carbon. In addition to their unique structure, PDCs are known for their high surface area (~822.7 m² g⁻¹), which makes them potential candidates for supercapacitor applications. However, low electrical conductivity, voltage hysteresis, and first cycle lithium irreversibility have hindered their introduction into commercial devices. One approach to improving charge storage capacity is by interfacing the preceramic polymer with boron or aluminium prior pyrolysis. Recent research has shown that chemical interfacing with elemental boron, bulk boron powders and even exfoliated sheets of boron nitride leads to enhancements in thermal and electronic properties of the ceramic. This thesis reports the synthesis of a new type of PDC composite comprising of SiOC embedded with boron nitride nanotubes (BNNTs). This was achieved through the introduction of BNNT in SiOC pre-ceramic polymer at varying wt.% loading (0.25, 0.5 and 2.0 wt.%) followed by thermolysis at high temperature. Electron microscopy and a range of spectroscopy techniques were employed to confirm the polymer-to-ceramic transformation and presence of disordered carbon phase. Transmission electron microscopy confirmed the tubular morphology of BNNT in the composite. To test the material for electrochemical applications, the powders were then made into free-standing paper-like electrodes with reduced graphene oxide (rGO) acting as support material. The synthesized free-standing electrodes were characterized and tested as electrochemical energy storage materials for LIBs and symmetric supercapacitor applications. Among the SiOC-BNNT composite paper tested as anode materials for LIBs, the 0.25 wt.% BNNT composite paper demonstrated the highest first cycle lithiation capacity corresponding to 812 mAh g⁻¹ (at a current density of 100 mA g⁻¹) with a stable charge capacity of 238 mAh g⁻¹ when asymmetrically cycled after 25 cycles. On the contrary, the 0.5 wt.% BNNT composite paper demonstrated the highest specific capacitance corresponding to 78.93 F g⁻¹ at a current density of 1 A g⁻¹ and a cyclic retention of 86% after 185 cycles. This study shows that the free carbon content of SiOC-BNNT ceramic composite can be rationally modified by varying the wt.% of BNNT. As such, the paper composite can be used as an electrode material for electrochemical energy storage.
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Wu, Ding. "Control of a super-capacitor based energy storage system." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/control-of-a-supercapacitor-based-energy-storage-system(e43378a8-22ec-442a-bc87-df4adb5fb3cb).html.
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The increasing use of electrical technologies within on-board (aircraft, road vehicle, train and ship) power systems is resulting in complex and highly dynamic networks in which energy storage devices have an important role to play, for example to resolve the instantaneous mismatch between load demand and power availability or to provide the flexibility to optimise overall performance. In this thesis, a multi-level controller for a super-capacitor based energy storage system (ESS) is designed, simulated, emulated and validated experimentally to show its effectiveness in smoothing load and managing state-of-charge of the energy storage system. This thesis first investigates the low level control of the dual-interleaved converter, particularly at light load where seven discontinuous conduction modes (DCMs) appear. A thorough analysis of these operating modes is given and validated by simulations and experiments. Based on the analysis, an inverse-model-based feed-forward current controller is implemented, offering a low level converter control interface which serves the high level supervisory controller within the energy storage system. Two supervisory control methods have been proposed in this thesis, both producing a super-capacitor current reference for the low level controller. The first supervisory control not only manages the energy within the ESS but also shields the primary power source from rapid load transients , which has been examined through an emulated ESS in the Intelligent Electrical Power Network Evaluation Facility (IEPNEF). A more advanced supervisory controller is then proposed which in addition to the benefits of the first control, regulates the rate-of-change in power that is drawn from the primary power source in the system. The proposed second control method is implemented within a real super-capacitor energy storage system in IEPNEF, with both simulation and experimental results successfully demonstrating and validating its operation.
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Gao, Hongyan. "Nano/Submicro-Structured Iron Cobalt Oxides Based Materials for Energy Storage Application." TopSCHOLAR®, 2017. https://digitalcommons.wku.edu/theses/2057.
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Supercapacitors, as promising energy storage devices, have been of interest for their long lifespan compared to secondary batteries, high capacitance and excellent reliability compared to conventional dielectric capacitors. Transition metal oxides can be applied as the electrode materials for pseudocapacitors and offer a much higher specific capacitance. Co3O4 is one of the most investigated transition metal oxides for supercapacitor. Besides simple monometallic oxides, bimetallic transition oxides have recently drawn growing attention in electrochemical energy storage. They present many unique properties such as achievable oxidation states, high electrical conductivities because of the coexistence of two different cations in a single crystal structure.
This study focuses on the bimetallic iron cobalt oxide based materials for the application of energy storage. We selected iron as the substituent in spinel Co3O4, by virtue of its abundant and harmless character. Four types of iron cobalt oxides based electrode materials with different morphologies and components have been synthesized for the first time. The hydrothermal method was the main strategy for the synthesis of iron cobalt based materials, which achieved the control of morphology and ratio of components. Multiple characterization methods, including SEM, TEM, XRD, XPS, TGA, BET, have been applied to study the morphologies and nano/submicron structures. The electrochemical properties of as-fabricated samples were performed by electrochemical workstation. In addition, in order to investigate the practical application of electrode materials, asymmetric supercapacitors have been assembled by using as-prepared samples as the positive electrodes and activated carbon as the negative electrodes.
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Si, Wenping. "Designing Electrochemical Energy Storage Microdevices: Li-Ion Batteries and Flexible Supercapacitors." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-160049.
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Die Menschheit steht vor der großen Herausforderung der Energieversorgung des 21. Jahrhundert. Nirgendwo ist diese noch dringlicher geworden als im Bereich der Energiespeicherung und Umwandlung. Konventionelle Energie kommt hauptsächlich aus fossilen Brennstoffen, die auf der Erde nur begrenzt vorhanden sind, und hat zu einer starken Belastung der Umwelt geführt. Zusätzlich nimmt der Energieverbrauch weiter zu, insbesondere durch die rasante Verbreitung von Fahrzeugen und verschiedener Kundenelektronik wie PCs und Mobiltelefone. Alternative Energiequellen sollten vor einer Energiekrise entwickelt werden. Die Gewinnung erneuerbarer Energie aus Sonne und Wind sind auf jeden Fall sehr wichtig, aber diese Energien sind oft nicht gleichmäßig und andauernd vorhanden. Energiespeichervorrichtungen sind daher von großer Bedeutung, weil sie für eine Stabilisierung der umgewandelten Energie sorgen. Darüber hinaus ist es eine enttäuschende Tatsache, dass der Akku eines Smartphones jeglichen Herstellers heute gerade einen Tag lang ausreicht, und die Nutzer einen zusätzlichen Akku zur Hand haben müssen. Die tragbare Elektronik benötigt dringend Hochleistungsenergiespeicher mit höherer Energiedichte. Der erste Teil der vorliegenden Arbeit beinhaltet Lithium-Ionen-Batterien unter Verwendung von einzelnen aufgerollten Siliziumstrukturen als Anoden, die durch nanotechnologische Methoden hergestellt werden. Eine Lab-on-Chip-Plattform wird für die Untersuchung der elektrochemischen Kinetik, der elektrischen Eigenschaften und die von dem Lithium verursachten strukturellen Veränderungen von einzelnen Siliziumrohrchen als Anoden in einer Lithium-Ionen-Batterie vorgestellt. In dem zweiten Teil wird ein neues Design und die Herstellung von flexiblen on-Chip, Festkörper Mikrosuperkondensatoren auf Basis von MnOx/Au-Multischichten vorgestellt, die mit aktueller Mikroelektronik kompatibel sind. Der Mikrosuperkondensator erzielt eine maximale Energiedichte von 1,75 mW h cm-3 und eine maximale Leistungsdichte von 3,44 W cm-3. Weiterhin wird ein flexibler und faserartig verwebter Superkondensator mit einem Cu-Draht als Substrat vorgestellt. Diese Dissertation wurde im Rahmen des Forschungsprojekts GRK 1215 "Rolled-up Nanotechnologie für on-Chip Energiespeicherung" 2010-2013, finanziell unterstützt von der International Research Training Group (IRTG), und dem PAKT Projekt "Elektrochemische Energiespeicherung in autonomen Systemen, no. 49004401" 2013-2014, angefertigt. Das Ziel der Projekte war die Entwicklung von fortschrittlichen Energiespeichermaterialien für die nächste Generation von Akkus und von flexiblen Superkondensatoren, um das Problem der Energiespeicherung zu addressieren. Hier bedanke ich mich sehr, dass IRTG mir die Möglichkeit angebotet hat, die Forschung in Deutschland stattzufindenHuman beings are facing the grand energy challenge in the 21st century. Nowhere has this become more urgent than in the area of energy storage and conversion. Conventional energy is based on fossil fuels which are limited on the earth, and has caused extensive environmental pollutions. Additionally, the consumptions of energy are still increasing, especially with the rapid proliferation of vehicles and various consumer electronics like PCs and cell phones. We cannot rely on the earth’s limited legacy forever. Alternative energy resources should be developed before an energy crisis. The developments of renewable conversion energy from solar and wind are very important but these energies are often not even and continuous. Therefore, energy storage devices are of significant importance since they are the one stabilizing the converted energy. In addition, it is a disappointing fact that nowadays a smart phone, no matter of which brand, runs out of power in one day, and users have to carry an extra mobile power pack. Portable electronics demands urgently high-performance energy storage devices with higher energy density. The first part of this work involves lithium-ion micro-batteries utilizing single silicon rolled-up tubes as anodes, which are fabricated by the rolled-up nanotechnology approach. A lab-on-chip electrochemical device platform is presented for probing the electrochemical kinetics, electrical properties and lithium-driven structural changes of a single silicon rolled-up tube as an anode in lithium ion batteries. The second part introduces the new design and fabrication of on chip, all solid-state and flexible micro-supercapacitors based on MnOx/Au multilayers, which are compatible with current microelectronics. The micro-supercapacitor exhibits a maximum energy density of 1.75 mW h cm-3 and a maximum power density of 3.44 W cm-3. Furthermore, a flexible and weavable fiber-like supercapacitor is also demonstrated using Cu wire as substrate. This dissertation was written based on the research project supported by the International Research Training Group (IRTG) GRK 1215 "Rolled-up nanotech for on-chip energy storage" from the year 2010 to 2013 and PAKT project "Electrochemical energy storage in autonomous systems, no. 49004401" from 2013 to 2014. The aim of the projects was to design advanced energy storage materials for next-generation rechargeable batteries and flexible supercapacitors in order to address the energy issue. Here, I am deeply indebted to IRTG for giving me an opportunity to carry out the research project in Germany. September 2014, IFW Dresden, Germany Wenping Si
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K, C. Bibek. "Impact of a Hybrid Storage Framework Containing Battery and Supercapacitor on Uncertain Output of Wind and Solar Power Systems." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2618.
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Renewable energy resources (RES) are becoming more popular for electricity generation due to their easy installation, flexibility, low cost, environmental compatibility, etc. However, their fluctuating nature is a major drawback, which decreases the power quality and makes them less trusty in the power system. To mitigate this problem, battery energy storage (BES) has been widely used with renewable energy sources. Because batteries are designed to handle “steady fluctuations” of power, the “sudden and peak” fluctuating power levels of renewable energy sources may cause shorter life spans for them, which may cause dramatic economic loss or negatively impact the power quality. Also, even though batteries have been used as a backup for RES, high power quality cannot be guaranteed when there is a rapid and peak fluctuations on source/load.
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Andres, Britta. "Paper-based Supercapacitors." Licentiate thesis, Mittuniversitetet, Avdelningen för naturvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-22410.
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The growing market of mobile electronic devices, renewable off-grid energy sources and electric vehicles requires high-performance energy storage devices. Rechargeable batteries are usually the first choice due to their high energy density. However, supercapacitors have a higher power density and longer life-time compared to batteries. For some applications supercapacitors are more suitable than batteries. They can also be used to complement batteries in order to extend a battery's life-time. The use of supercapacitors is, however, still limited due to their high costs. Most commercially available supercapacitors contain expensive electrolytes and costly electrode materials. In this thesis I will present the concept of cost efficient, paper-based supercapacitors. The idea is to produce supercapacitors with low-cost, green materials and inexpensive production processes. We show that supercapacitor electrodes can be produced by coating graphite on paper. Roll-to-roll techniques known from the paper industry can be employed to facilitate an economic large-scale production. We investigated the influence of paper on the supercapacitor's performance and discussed its role as passive component. Furthermore, we used chemically reduced graphite oxide (CRGO) and a CRGO-gold nanoparticle composite to produce electrodes for supercapacitors. The highest specific capacitance was achieved with the CRGO-gold nanoparticle electrodes. However, materials produced by chemical synthesis and intercalation of nanoparticles are too costly for a large-scale production of inexpensive supercapacitor electrodes. Therefore, we introduced the idea of producing graphene and similar nano-sized materials in a high-pressure homogenizer. Layered materials like graphite can be exfoliated when subjected to high shear forces. In order to form mechanical stable electrodes, binders need to be added. Nanofibrillated cellulose (NFC) can be used as binder to improve the mechanical stability of the porous electrodes. Furthermore, NFC can be prepared in a high-pressure homogenizer and we aim to produce both NFC and graphene simultaneously to obtain a NFC-graphene composite. The addition of 10% NFC in ratio to the amount of graphite, increased the supercapacitor's capacitance, enhanced the dispersion stability of homogenized graphite and improved the mechanical stability of graphite electrodes in both dry and wet conditions. Scanning electron microscope images of the electrode's cross section revealed that NFC changed the internal structure of graphite electrodes depending on the type of graphite used. Thus, we discussed the influence of NFC and the electrode structure on the capacitance of supercapacitors.
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Weber, Christian [Verfasser], Jens [Gutachter] Pflaum, and Jean [Gutachter] Geurts. "Electrochemical Energy Storage: Carbon Xerogel-Manganese Oxide Composites as Supercapacitor Electrode Materials / Christian Weber. Gutachter: Jens Pflaum ; Jean Geurts." Würzburg : Universität Würzburg, 2016. http://d-nb.info/1111785198/34.
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Khasawneh, Hussam Jihad. "Sizing Methodology and Life Improvement of Energy Storage Systems in Microgrids." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429638668.
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Farhadi, Mustafa. "Hybrid Energy Storage Implementation in DC and AC Power System for Efficiency, Power Quality and Reliability Improvements." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2471.
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Battery storage devices have been widely utilized for different applications. However, for high power applications, battery storage systems come with several challenges, such as the thermal issue, low power density, low life span and high cost. Compared with batteries, supercapacitors have a lower energy density but their power density is very high, and they offer higher cyclic life and efficiency even during fast charge and discharge processes. In this dissertation, new techniques for the control and energy management of the hybrid battery-supercapacitor storage system are developed to improve the performance of the system in terms of efficiency, power quality and reliability.
To evaluate the findings of this dissertation, a laboratory-scale DC microgrid system is designed and implemented. The developed microgrid utilizes a hybrid lead-acid battery and supercapacitor energy storage system and is loaded under various grid conditions. The developed microgrid has also real-time monitoring, control and energy management capabilities.
A new control scheme and real-time energy management algorithm for an actively controlled hybrid DC microgrid is developed to reduce the adverse impacts of pulsed power loads. The developed control scheme is an adaptive current-voltage controller that is based on the moving average measurement technique and an adaptive proportional compensator. Unlike conventional energy control methods, the developed controller has the advantages of controlling both current and voltage of the system. This development is experimentally tested and verified. The results show significant improvements achieved in terms of enhancing the system efficiency, reducing the AC grid voltage drop and mitigating frequency fluctuation.
Moreover, a novel event-based protection scheme for a multi-terminal DC power system has been developed and evaluated. In this technique, fault identification and classifications are performed based on the current derivative method and employing an artificial inductive line impedance. The developed scheme does not require high speed communication and synchronization and it transfers much less data when compared with the traditional method such as the differential protection approach. Moreover, this scheme utilizes less measurement equipment since only the DC bus data is required.
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Korenblit, Yair. "Zeolite templated carbons: investigations in extreme temperature electrochemical capacitors and lead-acid batteries." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/47643.
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Porous carbons are versatile materials with applications in different fields. They are used in filtration, separation and sequestration of fluids and gases, as conductive additives in many energy storage materials, as coloring agents, as pharmaceutical and food additives, and in many other vital technologies. Porous carbons produced by pyrolysis and activation of organic precursors commonly suffer from poorly controlled morphology, microstructure, chemistry, and pore structure. In addition, the poorly controlled parameters of porous carbons make it challenging to elucidate the underlying key physical parameters controlling their performance in energy storage devices, including electrochemical capacitors (ECs) and lead-acid batteries (LABs). Zeolite-templated carbons (ZTCs) are a novel class of porous carbon materials with uniform and controllable pore size, microstructure, morphology, and chemistry. In spite of their attractive properties, they have never been explored for use in LABs and their studies for ECs have been very limited. Here I report a systematic study of ZTCs applications in ECs operating at temperatures as low as - 70 C and in LABs. Greatly improved power and energy performance, compared to state of the art devices, has been demonstrated in the investigated ECs. Moreover, the application of ZTCs in LABs has resulted in a dramatic enhancement of their cycle life and power and energy densities.
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Areir, Milad. "Development of 3D printed flexible supercapacitors : design, manufacturing, and testing." Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/16659.
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The development of energy storage devices has represented a significant technological challenge for the past few years. Electrochemical double-layer capacitors (EDLCs), also named as supercapacitors, are a likely competitor for alternative energy storage because of their low-cost, high power density, and high fast charge/discharge rate. The recent development of EDLCs requires them to be lightweight and flexible. There are many fabrication techniques used to manufacture flexible EDLCs, and these methods can include pre-treatment to ensure more efficient penetration of activated carbon (AC) patterns onto the substrate, or those that utilise masks for the definitions of patterns on substrates. However, these methods are inconvenient for building cost-effective devices. Therefore, it was necessary to find a suitable process to reduce the steps of manufacture and to be able to print multiple materials uniformly. This research work describes the first use of a 3D printing technology to produce flexible EDLCs for energy storage. In this research work, the four essential elements for the EDLCs substrate, current collector, activated electrode, and gel electrolyte were investigated. The AC powder was milled by ball milling to optimise the paste deposition and the electrochemical performance. A flexible composite EDLC was designed and manufactured by 3D printing. The electrochemical performance of the flexible composite EDLCs was then examined. Being highly flexible is one of the critical demands for the recent development of EDLCs. Therefore, highly flexible EDLCs were designed and manufactured by only one single extrusion process. The 3D highly flexible EDLC maintains significant electrochemical performance under a mechanical bending test. To meet the power and energy requirements, the EDLCs were connected and tested in series and parallel circuits. A supercapacitor based on printed AC material displays an area specific capacitance of 1.48 F/cm2 at the scan rate of 20 mV/s. The coulombic efficiency for the flexible EDLC was found to be 59.91%, and the cycling stability was achieved to be 56% after 500 cycles. These findings indicate that 3D printing technology may be increasingly used to develop more sophisticated flexible wearable electronic devices.
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Lé, Tao. "Fundamental insights into dynamic ionic exchange in vertically-oriented nanostructured materials via fast electrogravimetric methods. Applications to energy storage mechanisms." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS202.
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Une meilleure compréhension des mécanismes d’échanges ioniques au sein de matériaux d’électrode de supercondensateurs peut être obtenue en couplant les méthodes de caractérisation électrochimique avec des mesures de microbalance à quartz. Parmi les matériaux d’électrodes en cours de développement, une grande amélioration des performances ont été obtenues avec des nanostructures verticales, cependant la technique de microbalance à quartz électrochimique n’a pas encore été employée sur ce type d’électrodes. L’objectif de cette thèse est d’appliquer les méthodes de caractérisation par microbalance à quartz électrochimique à des électrodes de supercondensateurs nanostructurées verticalement. Les nanostructures étudiées au cours de cette thèse sont les nanofils de silicium, les nanofils de PEDOT, les nanofils hybrides silicium/PEDOT ainsi que les voiles de graphène orientés verticalement (VOGNs). La croissance de ces nanostructures a été obtenue directement sur la surface de la microbalance en minimisant les effets sur la qualité de cette dernière. L’effet de l’amortissement de la résonance par ces nanostructures a été étudié dans différents types d’électrolytes. Les échanges ioniques dynamiques ayant lieu au sein d’électrodes à base de VOGNs et de nanofils de PEDOT ont pu être dévoilés. Ces premières avancées dans l’application des mesures électrogravimétriques à des nanostructures verticales ont montré l’étendue des possibilités pour la caractérisation de supercondensateurs à électrodes nanostructurées. Les limites de ces techniques dues aux amortissements hydrodynamiques ont également été montrées pour les architectures plus épaissesA better understanding of the ionic exchange mechanisms within supercapacitor electrode materials can be obtained by coupling classical electrochemical techniques with microbalance measurements. Using vertically-oriented nanostructures, supercapacitor devices can be greatly enhanced, however microbalance measurements had not yet been performed with such electrodes. The aim of this Ph.D. thesis is to perform electrochemical quartz crystal microbalance measurements on vertically-oriented nanostructured electrodes for supercapacitors. The nanostructured materials studied throughout this work are silicon nanowires, PEDOT nanowires, hybrid PEDOT-silicon nanowires and vertically-oriented graphene nanosheets (VOGNs). The growth of these nanostructures was obtained directly on the surface of a microbalance while minimizing the effects on it’s quality. The effect of resonance damping with the nanostructures was studied in various electrolytes. The ionic exchange dynamics in VOGN and PEDOT nanowires have been unveiled. These first microbalance results on vertically-oriented nanostructures pave the way to characterizing other nanostructured electrodes for supercapacitors
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Daun, Kevin. "Impact of energy storage technologies in a distribution grid : An analysis of Key Performance Indicators relating to a local grid’s performance characteristics." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-55367.
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The energy system is undergoing a transformation on a never before witnessed scale. The changes are driven by global market forces and technological advancements, improving on a seemingly exponential scale. This in turn has led to the price of both renewables and the accompanying technology decrease over time, making the transition into renewables more economically viable. The drawback of variable renewable energy is that it is variable and dependent on the surrounding environment. Therefore, storing the energy during hours of production, to be used at a later stage when energy demand is higher is becoming ever more important and an attractive option. The purpose of this degree project is to, from a set of performance indicators, evaluate three different energy storage technologies and their respective impact on a distribution grid. The examined storage technologies are: Batteries, Capacitators and a H2 Fuel cell. A literature study was performed in order to find out how grid performance is evaluated, and how the different storage technologies operate. The obtained literature comes from scientific reports, and papers, found by utilizing Mälardalens University library-database. A model representing a Swedish grid with a connection point to the distribution side was created. The model is taken from previous credited work, and customized to fit the operational parameters of a Swedish grid. It was decided that the key indicators for evaluating the state of a grid was to look at the: voltage- and frequency variations, load factor, capacity factor and the overall system efficiency. The simulation is a discrete time simulation that utilizes parameters indicative of one full day of data. The results showed that, from a technological standpoint, the supercapacitor performed better in more categories than the Li-ion battery and H2 fuel cell. However, the Li-ion battery reduced the peaks of the frequency measurements which is a key metric when deciding on grid health. Also, there is the added benefit of the battery and fuel cell of having a longer operational time before the state of charge is depleted. This increases the flexibility of the technology and could therefore be more beneficial in other applications where power supply is more scarce.
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Zhang, Yu. "Small-Signal Modeling and Analysis of Parallel-Connected Power Converter Systems for Distributed Energy Resources." Scholarly Repository, 2011. http://scholarlyrepository.miami.edu/oa_dissertations/551.
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Alternative energy resources (such as photovoltaics, fuel cells, wind turbines, micro-turbines, and internal combustion engines) and energy storage systems (such as batteries, supercapacitors, and flywheels) are increasingly being connected to the utility grid, creating distributed energy resources which require the implementation of an effective distributed power management strategy. Parallel-connected power converters form a critical component in such a distributed energy resources system. This dissertation addresses small-signal modeling and analysis of parallel-connected power converter systems operating in distributed energy environments. This work focuses on DC-DC and DC-AC power converters. First, this work addresses the small-signal modeling and analysis of parallel-connected power converters in a battery/supercapacitor hybrid energy storage system. The small-signal model considers variations in the current of individual energy storage devices and the DC bus voltage as state variables, variations in the power converter duty cycles as control variables, and variations in the battery and the supercapacitor voltages and the load current as external disturbances. This dissertation proposes several different control strategies and studies the effects of variations in controller and filter parameters on system performance. Simulation studies were carried out using the Virtual Test Bed (VTB) platform under various load conditions to verify the proposed control strategies and their effect on the final states of the energy storage devices. Control strategies for single DC-AC three-phase power converters are also identified and investigated. These include a novel PV (active power and voltage) control with frequency droop control loop, PQ (active power and reactive power) control, voltage control, PQ control with frequency droop control, and PQ control with voltage and frequency droop control. Small-signal models of a three-phase power converter system with these control strategies were developed, and the impact of parameter variations on the stability of a PV controlled converter were studied. Moreover, a small-signal model of parallel-connected three-phase DC-AC power converters with individual DC power supplies and network is proposed. The simulations carried out in stand-alone and grid-connected modes verify the combined control strategies that were developed. In addition, a detailed small-signal mathematical model that can represent the zero-sequence current dynamics in parallel-connected three-phase DC-AC power converters that share a single DC power source is presented. The effects of a variety of factors on the zero-sequence current are investigated, and a control strategy to minimize the zero-sequence current is proposed. Time-domain simulation studies verify the results. Simulations of a parallel-connected DC-AC power converter system with nonlinear load were carried out. The active power filter implemented in this system provides sharing of harmonic load between each power converter, and reduces harmonic distortion at the nonlinear load by harmonic compensation.
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Rowlands, Stephen E. "Electrochemical supercapacitors for energy storage applications." Thesis, De Montfort University, 2002. http://hdl.handle.net/2086/4077.
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Ertas, Merve. "Dioxypyrrole based supercapacitors for energy storage." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024365.
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Morossi, Ilaria. "Modellazione e analisi in frequenza di celle a supercondensatore." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Find full textAbstract:
Tra le diverse tipologie di sistemi di accumulo energetico, i supercondensatori, grazie alla
elevata densità di potenza, alla scarsa manutenzione richiesta e alla lunga vita utile in termini di
numero di cicli, vedono grande flessibilità e possibilità di applicazione in molteplici settori del
mercato, sia in utilizzo esclusivo sia all’interno di sistemi ibridi, dove vengono affiancati ad
un'altra tecnologia di accumulo con caratteristiche complementari in grado di migliorarne le
performance.
Nell’ottica di estendere le applicazioni e ottimizzare il progetto e le prestazioni dei sistemi a
supercondensatore è fondamentale lo sviluppo di modelli efficaci, in grado di simulare in
maniera fedele il comportamento reale. L’elaborazione di modelli permette di eseguire test e
simulare diverse condizioni operative, anche estreme, contenendo i costi e senza generare
situazioni di pericolo.
In questa tesi vengono esposti i principali modelli elettrici di celle a supercondensatore (SCs)
presenti in letteratura e ne viene proposta l’implementazione in ambiente Matlab-Simulink,
avvalendosi anche degli strumenti forniti dalle librerie Stateflow e Simscape.
La procedura di stima dei parametri viene condotta attraverso la apposita toolbox di Simulink e
i risultati dei modelli ottimizzati vengono confrontati con i profili sperimentali, ricavati da test
eseguiti in laboratorio su un supercondensatore Maxwell Technologies BCAP3000.
Infine, vista la possibilità offerta dai SC di sopportare veloci cicli di carica e scarica, viene
eseguita un’analisi della risposta in frequenza, sempre in ambiente Simulink, in cui si realizza
il diagramma complesso di impedenza nel range di frequenza da 1 mHz a 100 kHz. Tale analisi
consentirà di individuare i valori di frequenza limite oltre i quali il supercondensatore non risulta
più efficiente e sarà completata da un’interpretazione sia elettrica circuitale, sia fisica dei grafici
di impedenza.
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Gaboriau, Dorian. "Nanostructures de silicium par croissance chimique catalysée : une plate-forme pour des applications micro-supercondensateurs." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAV073/document.
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Les supercondensateurs sont des dispositifs de stockage électrochimique de l’énergie ayant été récemment mis au point et possédant des performances intermédiaires entre les condensateurs diélectriques et les batteries. Leurs intéressantes valeurs de densité d’énergie et de puissance, conjuguées à leur excellente durée de vie et à leur miniaturisation facilité rendent ces composants prometteurs pour des micro-dispositifs électroniques, tels des micro-capteurs autonomes ou des implants médicaux.Le silicium nanostructuré par CVD a prouvé être un remarquable matériau d’électrode de supercondensateur, pour des applications miniaturisées, lors de récents travaux. L’excellent contrôle de la morphologie et des propriétés électroniques permis par la synthèse montante de nano-fils et nano-arbres de silicium, ainsi que la grande stabilité électrochimique et thermique de ce matériau font des nanostructures de silicium obtenues par synthèse montante une excellente plate-forme pour des micro-supercondensateurs.La présente thèse s’attache à explorer plusieurs voies d’amélioration et d’utilisation des nano-fils et nano-arbres de silicium. Une étude systématique de l’optimisation des nanostructures a été conduite, permettant d’améliorer largement les performances précédemment établies. Ensuite, une fonctionnalisation par des couches minces d’alumines utilisant la technique d’ALD a permis d’accroitre largement la plage de tensions d’utilisation des supercondensateurs, et d’augmenter leur stabilité électrochimique. Enfin, la croissance « sur-puce », ainsi que l’étude de la stabilité en température des dispositifs ont été effectuées, laissant entrevoir d’importantes perspectives d’applicationsSupercapacitors are electrochemical energy storage devices which have been recently developed, and possess intermediate performances between dielectric capacitors and batteries. These components exhibit interesting power and energy densities, combined with an exceptional cycle life and an easy miniaturization. Supercapacitors are thus envisioned as energy storage solutions for electronic micro-devices, such as autonomous micro-sensors or implantable medical devices.In recent studies, CVD nanostructured silicon proved to be an excellent electrode material candidate for micro-supercapacitor applications. Bottom-up synthesis allows an exceptional control of the morphology and electrical properties of the obtained silicon nano-wires and nano-trees. Moreover, the nanostructured electrodes possess superior electrochemical and temperature stability. These arguments lead to consider silicon as an excellent platform for micro-supercapacitors applications.This PhD thesis details various ways to improve and use silicon nano-wires and nano-trees. The nanostructures have been subjected to a systematic optimization study, yielding a significant increase of the electrochemical performances of the electrodes, compared to previously published studies. In addition, surface functionalization using thin ALD alumina layers permitted a considerable increase of the supercapacitor voltage window and an improved electrochemical stability. Finally, “on-chip” nanostructure growth, and temperature stability studies of the device were conducted, opening a broad field of improvements and potential uses for these silicon nanostructures
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Coustan, Laura. "Matériaux pseudo-capacitifs pour supercondensateurs flexibles." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS169/document.
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Les supercondensateurs sont des dispositifs de stockage de l'énergie électrique particulièrement intéressants pour les applications de puissance. Les rendre flexibles permet de considérer de nouvelles possibilités d'intégration. Néanmoins, l'optimisation de la densité d'énergie, point faible de ces dispositifs, passe par la recherche et l'étude de nouveaux matériaux d'électrode et d'électrolytes. Dans ce but, ce travail de thèse s'est orienté vers des matériaux pseudo-capacitifs, avec l'utilisation d'électrodes à base de MnO2, et d'électrolytes à base de liquide ionique fonctionnalisé de type biredox. Afin de conserver le caractère flexible des électrodes, le dioxyde de manganèse a d'abord été synthétisé pour la formulation d'encres à pulvériser sur substrat flexible. A cette occasion, l'influence de dispersants sur les performances a été étudiée. Les performances de matériaux nanocomposites à base de fibres de carbone et de graphène décorés par MnO2 ont ensuite été évaluées. Les contributions faradiques et surfaciques à la capacité développée par MnO2 ont ensuite été déterminées par une étude électrochimique fine. Enfin, l'étude d'un nouveau liquide ionique fonctionnalisé utilisé dans un dispositif carbone/carbone a confirmé l'attractivité de ces phénomènes faradiques dans les performances électrochimiques d'un supercondensateurSupercapacitors are attractive electrical energy storage devices for power applications. As flexible devices new integration opportunities can be consider. Nevertheless, the optimization of the energy density, weak point of these devices, proceeds through the search and the study of new electrode materials and electrolytes. In this aim, this thesis work is turned towards so called pseudo-capacitive materials, with the use of MnO2-based electrodes, and biredox Ionic Liquid electrolytes. To preserve the flexible behavior of the electrodes, the manganese dioxide was, at first, synthesized for the formulation of an ink to be sprayed on flexible substrates. The influence of dispersing agents on the electrochemical performances was evaluated. Performances of nanocomposite materials prepared with carbon nanofibers and graphene oxide sheets were also studied. Faradaic and surface contributions to the capacity developed by MnO2 electrode material were then determined by an advanced electrochemical study. Finally, the study of a new Ionic Liquid used in a symmetrical carbon/carbon supercapacitor confirmed the attractiveness of these Faradaic phenomena for the enhancement of the supercapacitor electrochemical performances
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Žák, Jaromír. "Návrh a optimalizace senzorických systémů využívajících malovýkonových napájecích generátorů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-234527.
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Dissertation thesis is focused on using alternative energy sources called energy harvesting. This thesis offers a solution to problems with autonomous powering of sensor networks if primary power source recovery is impossible. In these cases, energy of the external power (e.g. temperature, light, motion) should be used. Proposed solution should be especially used in the field of medical applications (e.g. cochlear implants, pacemakers, insulin pumps). Long time monitoring of the personal health status is also possible when employing automated sensor systems. In this work, there is state of art review relating to the low power energy sources for an alternative powering of sensor systems. It was observed that existing systems are almost prepared for the implementation of energy harvesting power sources. The energy harvesting power sources have been developed by numerous researcher teams around the world, but there are only a few variants of power management circuits for effective energy gaining, storing and using. This area has a huge potential for the next research. The issues regarding to the distribution of gained energy are solved on the complex level in the thesis. For these purposes, a new simulation model of the whole system (fully implantable artificial cochlea) including its subcircuits was developed in the SPICE environment. It connects independent subcircuits into a single comprehensive model. Using this model, a few novel principles for energy distribution (e.g. Charge Push Through technique) was developed. In the near future, these techniques are also applicable to the design of versatile sensor systems.
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Mourad, Eléonore. "De la chimie moléculaire,supramoléculaire, et macromoléculaire des liquides ioniques vers les dispositifs de stockage de l’énergie électrochimique." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT200/document.
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Le concept central de cette thèse est de mettre en avant trois grandes propriétés du liquide ionique, c'est à dire ses propriétés structurées et structurantes qui sont complémentaires à leurs propriétés usuelles (conductivité ionique, stabilité thermique, stabilité électrochimique), mais il ne s’agit là que d’une facette du travail. En effet, la synthèse des liquides ioniques rédox est l’un des ancrages fort de ce travail : ainsi des liquides ioniques biredox (porteur de groupements redox à la fois sur l’anion et le cation) ont pu être synthétisés pour la première fois. Cette électro-activité apporte un éclairage nouveau dans le développement d'électrolytes pour les supercondensateurs dont nos capacités spécifiques sont deux à cinq fois plus grandes que les valeurs de la littérature dans le domaine. Parallèlement, des liquides ioniques redox ont été associés à des nanotubes de carbone; les composites obtenus (nommé bucky Gel redox) ont été mis en œuvre avec succès comme matériaux d’électrode pour l’étude des dynamiques des cascades de transferts électroniques et ioniques. Outre l’obtention de ces résultats électrochimiques, les liquides ioniques ont été structurés par synthèse supramoléculaire. Ainsi des liquides ioniques polymérisés ont été obtenus et mis en forme par électrofilage puis testés en tant qu’électrolyte solide dans un dispositif supercondensateur. Les propriétés électrochimiques de l’ensemble de ces objets liquides ioniques ont fait l’objet d’études approfondies par voltammétrie cyclique, spectroscopie d’impédance électrochimique, cyclages galvanostatiques et microscopie électrochimique à balayage. Les résultats obtenus valident totalement le concept de départ dans le fait jouer sur les chimies moléculaire, supramoléculaire et macromoléculaire des liquides ioniques pour améliorer les dispositifs de stockage électrochimique de l’énergieThe central concept of this project is to highlight three major ionic liquid properties. It lies on the control of the structured and structuring properties that are considered as complementary to the usual ionic liquids properties (ionic conductivity, thermal stability, electrochemical stability). However, this is a relatively small part of this work. The strong key point is the synthesis of redox ionic liquids. In this work a new biredox ionic liquids (contaning redox moieties both on the anion and the cation constituting the ionic liquid) have been successfully synthesized for the first time. This electro-activity opens the development of electrolytes for supercapacitors whose the specitific capacity is between two and five times larger than the values found in the literature. Meanwhile, redox ionic liquids have been associated with carbon nanotubes; the obtained composites were implemented as electrode materials for the study of dynamic electron transfer and ionic transfer. Besides these results, ionic liquids have been structured by supramolecular chemistry. Polymerized ionic liquids were obtained, shaped by electrospinning and tested as a solid electrolyte in a supercapacitor system. The electrochemical properties of these components (electrolyte materials or electrode materials) have been extensively studied by cyclic voltammetry, electrochemical impedance spectroscopy, galvanostatic cycling and scanning electrochemical microscopy. The results completely validate the original concept to take advantage of molecular, supramolecular and macromolecular chemistries of ionic liquids to improve electrochemical energy storage devices
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Lannelongue, Pierre. "Oxydes polycationiques pour supercondensateurs à haute densité d'énergie volumique." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS146/document.
Full textAbstract:
Les supercondensateurs sont des dispositifs de stockage électrochimique de l’énergie très intéressants lorsque des pics de puissance sont mis en jeu. Toutefois, leur densité d’énergie volumique est la principale limite pour leur intégration, en particulier, dans des systèmes de transport terrestre. L’utilisation de matériaux d’électrode ayant un comportement pseudocapacitif et des masses volumiques élevées permettrait d’améliorer la densité d’énergie volumique des supercondensateurs. Avec cet objectif, des dispositifs à base des matériaux de la famille Ba0,5Sr0,5CoxFe1-xO3-δ, nommés BSCFs, ont été développés dans le cadre de cette thèse. Plusieurs compositions de cette famille d’oxydes ont été préparées par un procédé glycine-nitrate et ont été testés comme matériau actif d’électrode positive en milieu aqueux neutre. La capacité volumique de ces matériaux s’avère être beaucoup plus élevée que celle des carbones activés utilisés dans les supercondensateurs commerciaux. Elle a montré également dépendre de la composition en cobalt et en fer, du régime de charge, de la nature de l’électrolyte… Le mécanisme de stockage de charges dans ces matériaux a été exploré grâce à des techniques in situ (absorption des rayons X) et operando (diffraction des rayons X) effectuées aux synchrotrons SOLEIL (France) et SPring-8 (Japon). Enfin, des dispositifs associant une électrode positive à base de BSCF et du carbone activé ou FeWO4 en tant qu’électrode négative ont démontré l’intérêt d’intégrer de tels matériaux pour améliorer la densité d’énergie volumique des supercondensateursSupercapacitors are attractive electrochemical energy storage devices for high power applications. However, volumetric energy density is the main limitation for their integration in such applications as terrestrial transport systems. The use of high density pseudocapacitive oxides as electrode material could lead to a volumetric energy density improvement. With this aim, materials from Ba0,5Sr0,5CoxFe1-xO3-δ family, so called BSCFs, have been studied. Several compositions have been prepared and evaluated as positive electrode materials in aqueous neutral electrolyte. Volumetric capacitances have shown to be greater than those of activated carbons, already used in marketed supercapacitors. They have also shown to depend on cobalt and iron ratio, charge rate, electrolyte composition... The study of the charge storage mechanism in these materials has been investigated thanks to in situ (X-Ray absroption spectroscopy) and operando (X-Ray diffraction) technics performed at SOLEIL (France) and SPring-8 (Japan) synchrotron facilities. Finally, devices coupling BSCF based positive electrode material with activated carbon or FeWO4 based negative electrode materials have demonstrated the added value of such materials to improve the volumetric energy density of supercapacitors
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Jensen, Jasmine R. "Transition metal layered double hydroxides for energy storage." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/83674/1/Jasmine_Jensen_Thesis.pdf.
Full textAbstract:
Various types of layered double hydroxides, a type of clay, were synthesised. They were then electrochemically tested to determine whether the samples would be suitable to store energy as supercapacitors. A manganese aluminium layered double hydroxide was electrochemically tested for the first time and found to have a large capacitance.