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Shash, N. M., M. M. Rashad, M. G. El-Shaarawy, M. H. Maklad i F. A. Afifi. "The Effect of Nano-SiO2 on the Structural, Electrical and Magnetic Properties of SiO2-LiFe5O8 Glass–ceramics Prepared by Sol Gel Auto-combustion Processing". Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42712.
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The glass–ceramic with the composition x(LiFe5O8)/(100 – x) SiO2 (x = 20, 30, 40, 50, 100 wt. % ) were prepared by sol gel auto-combustion method. The influence of the SiO2 ratio in the glass-ceramics strucure prepared was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Crystalline phases (LiFe5O8, SiO2, Fe2O3) were observed by X-ray powder diffraction in the glasses annealed at 800°C
for 2h. The crystallite size was found to increase from 27.29 nm (x = 20%) to 91.48 nm(x = 100 %). The microstructure of the formed powders was SiO2 ratio dependent. Increasing the SiO2 ratio was found to inhibit the grain growth of the formed ferrite. The electrical conductivity of glass-ceramics samples were raised with increasing the concentration of SiO2 ratio as the result of increasing the hopping of electrons between
Fe2+ and Fe3+ ions. The magnetic characteristics of the prepared glass ceramics were performed using a vibrating sample magnetometer in function of the magnetic field. The samples heat -treated at 800°C for 2h present a ferrimagnetic behavior. Alongside, the formed crystalline silicate lithium ferrite had good magnetic properties. High saturation magnetization (51.9 emu/g) was attained the formed ferrite sample of x = 100 % ratio annealed at 800°C for 2h.
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Dargaville, Steven. "Mathematical modelling of LiFePO4 cathodes". Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/60800/4/Steven_Dargaville_Thesis.pdf.
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LiFePO4 is a commercially available battery material with good theoretical discharge capacity, excellent cycle life and increased safety compared with competing Li-ion chemistries. It has been the focus of considerable experimental and theoretical scrutiny in the past decade, resulting in LiFePO4 cathodes that perform well at high discharge rates. This scrutiny has raised several questions about the behaviour of LiFePO4 material during charge and discharge. In contrast to many other battery chemistries that intercalate homogeneously, LiFePO4 can phase-separate into highly and lowly lithiated phases, with intercalation proceeding by advancing an interface between these two phases.
The main objective of this thesis is to construct mathematical models of LiFePO4 cathodes that can be validated against experimental discharge curves. This is in an attempt to understand some of the multi-scale dynamics of LiFePO4 cathodes that can be difficult to determine experimentally. The first section of this thesis constructs a three-scale mathematical model of LiFePO4 cathodes that uses a simple Stefan problem (which has been used previously in the literature) to describe the assumed phase-change. LiFePO4 crystals have been observed agglomerating in cathodes to form a porous collection of crystals and this morphology motivates the use of three size-scales in the model. The multi-scale model developed validates well against experimental data and this validated model is then used to examine the role of manufacturing parameters (including the agglomerate radius) on battery performance.
The remainder of the thesis is concerned with investigating phase-field models as a replacement for the aforementioned Stefan problem. Phase-field models have recently been used in LiFePO4 and are a far more accurate representation of experimentally observed crystal-scale behaviour. They are based around the Cahn-Hilliard-reaction (CHR) IBVP, a fourth-order PDE with electrochemical (flux) boundary conditions that is very stiff and possesses multiple time and space scales. Numerical solutions to the CHR IBVP can be difficult to compute and hence a least-squares based Finite Volume Method (FVM) is developed for discretising both the full CHR IBVP and the more traditional Cahn-Hilliard IBVP. Phase-field models are subject to two main physicality constraints and the numerical scheme presented performs well under these constraints.
This least-squares based FVM is then used to simulate the discharge of individual crystals of LiFePO4 in two dimensions. This discharge is subject to isotropic Li+ diffusion, based on experimental evidence that suggests the normally orthotropic transport of Li+ in LiFePO4 may become more isotropic in the presence of lattice defects. Numerical investigation shows that two-dimensional Li+ transport results in crystals that phase-separate, even at very high discharge rates. This is very different from results shown in the literature, where phase-separation in LiFePO4 crystals is suppressed during discharge with orthotropic Li+ transport.
Finally, the three-scale cathodic model used at the beginning of the thesis is modified to simulate modern, high-rate LiFePO4 cathodes. High-rate cathodes typically do not contain (large) agglomerates and therefore a two-scale model is developed. The Stefan problem used previously is also replaced with the phase-field models examined in earlier chapters. The results from this model are then compared with experimental data and fit poorly, though a significant parameter regime could not be investigated numerically. Many-particle effects however, are evident in the simulated discharges, which match the conclusions of recent literature. These effects result in crystals that are subject to local currents very different from the discharge rate applied to the cathode, which impacts the phase-separating behaviour of the crystals and raises questions about the validity of using cathodic-scale experimental measurements in order to determine crystal-scale behaviour.
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Карпов, Михайло Анатолійович. "Модуль балансування акумулятора LiFePO4 для електромобіля". Master's thesis, Київ, 2018. https://ela.kpi.ua/handle/123456789/25849.
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Актуальність теми. Розробка нової ідеї застосування акумулятора в сфері електромобілів.
Мета дослідження. Метою МД є дослідження процесу балансування напруги на комірках акумулятора при використанні різних за точністю модулів захисту комірок від перезаряду.
Для досягнення поставленої мети необхідно виконати такі задачі:
– Експериментальна модель комірки батареї;
– Розробка алгоритму балансування комірок;
– Розробка методики дослідження;
Об’єкт дослідження – модуль для балансування комірок акумулятора.
Предмет дослідження - дослідження затраченого часу на повну зарядку акумулятора від заданої точності модуля захисту комірки.
Методи дослідження: для вирішення завдань роботи були застосовані наступні методи: експериментальне моделювання зарядної характеристики та моделювання алгоритму балансування комірок за допомогою Excel.
Наукова новизна одержаних результатів. Отриманні результати демонструють характеристику заряду акумулятора за розробленим алгоритмом балансування, за рахунок якого можливо створити акумулятор з великою кількістю комірок, які будуть рівномірно збалансовані після заряду, при цьому кожна комірка матиме просту схему контролю.
Практичне значення одержаних результатів роботи полягає у можливості порівняти затрачений час зарядки для акумулятора з різними по точності схемами контролю перезарядки. Та оцінити доцільність використання більш точніших схем контролю перезарядки.Relevance of the topic. Developing a new service of using the battery for electric vehicles. The aim of the study is study the process of balancing voltage on battery cells when using different precisely modules for protecting cells To achieve this goal, you must accomplish the following tasks: - Experimental model of battery cell; - Development of algorithm of balancing of cells; - Development of research methodology; Object of research: is a module for balancing battery cells. Subject of research: is the study of the time taken to fully charge the battery from the given accuracy of the recharge circuit protection circuit. Research methods: the following methods were used to solve the tasks: experimental simulation of charge characteristics and simulation of the algorithm of balancing cells using Excel. Scientific novelty of the obtained results. The results show the characteristics of the battery charge based on the developed algorithm of balancing, due to which it is possible to create a battery with a large number of cells, which will be evenly balanced after the charge, with each cell will have a simple control circuit. The practical value of the results obtained is the ability to compare the charging time spent on the battery with different precision circuitry for recharging. But assess the feasibility of using more accurate recharge control schemes.
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Busson, Christophe. "Etude et optimisation de revêtements de collecteurs de courant en aluminium pour électrode positive, en vue d’augmenter les densités d’énergie et de puissance, et la durabilité de batteries lithium-ion". Thesis, Nantes, 2017. http://www.theses.fr/2017NANT4103.
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La recherche de batteries lithium-ion de hautes performances est nécessaire pour assurer nos besoins croissants en mobilité électrique. L’optimisation des matériaux d’électrodes et des électrolytes sont des voies très explorées. Par ailleurs, les collecteurs de courant jouent un rôle clé vis-à-vis des performances et de leur maintien au cours du cyclage en raison des problématiques d’adhésion, de résistance de contact électrique, et de corrosion, à l’interface électrode/collecteur. Dans ce but, des revêtements conducteurs et protecteurs pour collecteurs de courant en aluminium d’électrode positive ont été développés. Les phénomènes à l’interface entre l’électrode, de type LiFePO4 – PVdF, et le collecteur de courant ont été étudiés. Le mouillage de cette interface par l’électrolyte est apparu comme une origine majeure de la résistance de contact, probablement par la formation d’une double couche électrochimique. La sélection des matériaux utilisés dans la formulation des revêtements a permis de protéger la surface d’aluminium de ce contact avec l’électrolyte. Les conséquences sont très bénéfiques : diminution de la résistance de contact, augmentation des densités de puissance et d’énergie à hauts régimes, et protection de l’aluminium contre la corrosion dans un électrolyte de type LiTFSI. Il a notamment été montré qu’une des principales limitations d’une électrode de type LiFePO4 est sa résistance de contact avec le collecteur de courant, et qu’un revêtement performant permet d’éliminer totalement la part de carbone conducteur dans cette électrode tout en conservant de très bonnes performancesPerformance improvement is necessary in order to fulfill our increasing needs in electric mobility. Electrode and electrolyte materials optimization are privileged research directions. Furthermore, current collectors have a key role in the performance and their preservation, associated with electrode delamination, electrical contact resistance and corrosion issues at the current collector/electrode interface. To this end, conductive and protective coatings for aluminum current collectors have been developed. Interactions between a LiFePO4 – PVdF type electrode and current collectors were studied. The electrolyte wettability of this interface appeared to be a major contact resistance contribution, probably due to the formation of the electrochemical double layer. Protection of this interface was achieved through coatings’ material selection. Performance improvements have been observed: contact resistance decrease, higher power and energy densities at high rates and corrosion protection of aluminum substrates in LiTFSI-based electrolyte. It has been demonstrated that the contact resistance with current collectors is one of the major drawback of LiFePO4 electrodes, and an effective coating can allow the suppression of the electrode’s conductive carbon additives whereas performance are preserved
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Мухін, В. В., i М. М. Суслов. "LiFePO4 в якості катодного матеріалу в ЛІА". Thesis, Київський національний університет технологій та дизайну, 2018. https://er.knutd.edu.ua/handle/123456789/11749.
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Jüstel, Manuela [Verfasser]. "Synthese und Modifikation von Lithiumeisenphosphat (LiFePO4) / Manuela Jüstel". Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2013. http://d-nb.info/1034032283/34.
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Мухін, В. В. "Застосування LiFePO4 в якості електродного матеріалу в ХДС". Thesis, КНУТД, 2016. https://er.knutd.edu.ua/handle/123456789/4549.
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Hanžl, Ondřej. "Nabíječka 14,6 V 100 A pro LiFePO4 akumulátor". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2020. http://www.nusl.cz/ntk/nusl-412974.
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This thesis deals with a design, construciton and testing of a switch-mode power supply (SMPS) which is working as a LiFEPO4 battery charger with output current up to 100~A and output voltage up to 14,6~V. The output voltage and current can be regulated by the operator from zero to maximum value. For this SMPS Half-bridge asymmetrical forward converter with two transformers and common output inductor topology is chosen. The control circuits are run by the IC SG3525. Cascaded regulation of output voltage and current is implemented by two discrete operational amplifiers. Undervoltage protection of the control circuits and independent overcurrent protection on the primary side is also implemented.
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Zhang, S. C., G. R. Liu, X. Wei i X. Lu. "Surfactant Assisted Synthesis of LiFePO4 Nanostructures via Hydrothermal Processing". Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35206.
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LiFePO4 is a potential cathode candidate for of secondary lithium batteries due to its low-cost, out-standing thermal stability and innocuity. In this paper, pure LiFePO4 obtained by hydrothermal method using cetyltrimethyl ammonium bromide (CTAB) as surfactant. LiFePO4 particles produced without any surfactant showed typical morphologies of perfect octahedral with size of ~1μm. For products prepared with addition CTAB, the amount of surfactant controlled the growth of LiFePO4 crystals, with which dif-ferent morphologies of plate, grains and flower-like structures were produced. Plate products displayed a capacity of 145.70 mAh•g-1 at 0.1C, which was superior to others. The results indicated the electrochemical performance depends crucially on the size and structure of active materials.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35206
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Roscher, Michael [Verfasser]. "Zustandserkennung von LiFePO4-Batterien für Hybrid- und Elektrofahrzeuge / Michael Roscher". Aachen : Shaker, 2011. http://d-nb.info/1098039602/34.
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Channagiri, Samartha A. "Multiscale characterization of aging mechanisms in commercial LiFePO4 battery cathodes". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1468233768.
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Vilhelm, Ondřej. "Kompozitní elektrodové materiály pro lithium-iontové akumulátory na bázi LiFePO4". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219028.
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Presented work investigates the problem of secondary lithium-ion cells and the different available cathode materials. We have prepared samples of LiFePO4 with the addition of different kinds of carbon materials such as Super P, Vulcan and expanded graphite. We have always created the sample with and without surfactant. Developed samples were compared by measuring electrochemical methods (cyclic voltammetry, charge and discharge cycles and impedance spectroscopy). We also modeled the three-point cell for measuring electrochemical electrode materials.
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Krejčí, Pavel. "Elektrochemická příprava grafen oxidu a jeho využití v elektrodových kompozitech s LiFePO4". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-376908.
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This work deals with issues of application of the graphene material in the field of electrochemical energy storage. It includes basic graphene properties, the overview of methods for the production of lithium-iron-phosphate/graphene composites and results of different research approaches. The general aim is to present growing opportunity of application of graphene based composites in the electrochemical energy storage field. In the experimental part of this work, a electrochemical exfoliation of graphite and a production of LFP/G composites with different amount of graphene material and with different types of graphene material are carried out. This work includes also x-ray diffraction spectroscopy measurements and the evaluation of impacts of graphene additives on final properties of the electrochemical energy storage.
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Robert, Donatien. "Etude multi-échelle des mécanismes de (dé)lithiation et de dégradation d'électrodes à base de LiFePO¤ et silicium pour accumulateurs Li-ion". Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENY025/document.
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Ces travaux ont permis d'approfondir les mécanismes de (dé)lithiation et de vieillissement dans des électrodes à base de silicium et de LiFePO4 pour accumulateurs Li-ion à partir d'observations multi-échelles. Des cartographies de phases, autant à l'échelle de la particule qu'à l'échelle de l'électrode, ont été menées par microscopie électronique mettant en évidence de fortes hétérogénéités. Pour le silicium, la mise en place de cartographie unique par STEM/EELS, s'appuyant sur une base de données des pertes faibles d'alliages sensibles à l'air et au faisceau d'électrons, a permis de comprendre les mécanismes de lithiation à l'échelle du nanomètre. L'étude de la première lithiation a montré des différences de mécanismes de réaction avec le lithium suivant deux facteurs : la taille des particules et les défauts au sein de celles-ci. Il a été observé une composition d'alliage LixSi plus faible pour les nanoparticules que pour les microparticules. Les défauts dus notamment au broyage constituent des sites préférentiels de lithiation. En vieillissement, les nanoparticules subissent de profonds changements structuraux et morphologiques, passant d'un état sphérique cristallin (50 nm) à un réseau de fils amorphe (5-10 nm d'épaisseur) contenu dans une matrice de SEI. Pour le LiFePO4, il a été clairement montré, par la combinaison de plusieurs techniques de microscopies électroniques (diffraction des électrons en précession, EFSD : Electron Forward Scattering Diffraction, EFTEM), que les particules de taille nanométrique (100-200 nm) étaient soit entièrement lithiées soit entièrement délithiées à l'équilibre thermodynamique. De fortes hétérogénéités ont été observées dans les électrodes fines comme dans les électrodes épaisses. A l'échelle des particules, l'analyse statistique de plus de 64000 particules a montré que les plus petites particules se délithient en premier. A l'échelle de l'agglomérat, les cartographies de phases ont révélé un mécanisme « cœur-coquille » : la réaction débute de la surface vers le centre des agglomérats. A l'échelle de l'électrode, le front de propagation de phase se déplace suivant des chemins préférentiels de plus grandes porosités de la surface de l'électrode vers le collecteur de courant. La conductivité ionique au sein de nos électrodes est le facteur limitantThis work aimed at better understanding the (de)lithiation and aging mechanisms in LiFePO4 and silicon-based electrodes for Li-ion batteries from multiscale investigations. Phase mapping was performed by electron microscopy at the particle scale and at the electrode scale. This highlights some strong heterogeneities. The silicon study has shown some different lithium reaction mechanisms following two effects: particle size and crystalline defects. A smaller lithium amount in LixSi alloy was highlighted for the nanoparticles rather than for the microparticles. The defects mainly due to milling are preferential sites for the lithiation. In aging, the nanoparticles have undergone structural and morphological changes. The pristine crystalline spherical shape (50 nm) was transformed into an amorphous wire network (5-10 nm of thickness) contained in a SEI matrix. Thanks to a combination of electron microscopy techniques (precession electron diffraction, Electron Forward Scattering Diffraction, EFTEM), it was clearly shown that the LiFePO4 particles (100-200 nm) are either fully lithiated or fully delithiated at the thermodynamic equilibrium. Strong heterogeneities were observed in the thin and thick electrodes. At the nanoscale, the statistical analysis of 64000 particles unambiguously shows that the small particles delithiate in first. At the mesoscale, the phase maps reveal a core-shell mechanism at the scale of the agglomerates, from the surface to the center of these agglomerates. At the electrode scale, the phase front would move following preferential paths into the higher porosity from the surface in contact with electrolyte toward the current collector. The electrode ionic conductivity is the limiting parameter
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Popovic, Jelena. "Novel lithium iron phosphate materials for lithium-ion batteries". Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5459/.
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Conventional energy sources are diminishing and non-renewable, take million years to form and cause environmental degradation. In the 21st century, we have to aim at achieving sustainable, environmentally friendly and cheap energy supply by employing renewable energy technologies associated with portable energy storage devices. Lithium-ion batteries can repeatedly generate clean energy from stored materials and convert reversely electric into chemical energy. The performance of lithium-ion batteries depends intimately on the properties of their materials. Presently used battery electrodes are expensive to be produced; they offer limited energy storage possibility and are unsafe to be used in larger dimensions restraining the diversity of application, especially in hybrid electric vehicles (HEVs) and electric vehicles (EVs).
This thesis presents a major progress in the development of LiFePO4 as a cathode material for lithium-ion batteries. Using simple procedure, a completely novel morphology has been synthesized (mesocrystals of LiFePO4) and excellent electrochemical behavior was recorded (nanostructured LiFePO4). The newly developed reactions for synthesis of LiFePO4 are single-step processes and are taking place in an autoclave at significantly lower temperature (200 deg. C) compared to the conventional solid-state method (multi-step and up to 800 deg. C). The use of inexpensive environmentally benign precursors offers a green manufacturing approach for a large scale production. These newly developed experimental procedures can also be extended to other phospho-olivine materials, such as LiCoPO4 and LiMnPO4. The material with the best electrochemical behavior (nanostructured LiFePO4 with carbon coating) was able to delive a stable 94% of the theoretically known capacity.Konventionelle Energiequellen sind weder nachwachsend und daher nachhaltig nutzbar, noch weiterhin langfristig verfügbar. Sie benötigen Millionen von Jahren um gebildet zu werden und verursachen in ihrer Nutzung negative Umwelteinflüsse wie starke Treibhausgasemissionen. Im 21sten Jahrhundert ist es unser Ziel nachhaltige und umweltfreundliche, sowie möglichst preisgünstige Energiequellen zu erschließen und nutzen. Neuartige Technologien assoziiert mit transportablen Energiespeichersystemen spielen dabei in unserer mobilen Welt eine große Rolle. Li-Ionen Batterien sind in der Lage wiederholt Energie aus entsprechenden Prozessen nutzbar zu machen, indem sie reversibel chemische in elektrische Energie umwandeln. Die Leistung von Li-Ionen Batterien hängen sehr stark von den verwendeten Funktionsmaterialien ab. Aktuell verwendete Elektrodenmaterialien haben hohe Produktionskosten, verfügen über limitierte Energiespeichekapazitäten und sind teilweise gefährlich in der Nutzung für größere Bauteile. Dies beschränkt die Anwendungsmöglichkeiten der Technologie insbesondere im Gebiet der hybriden Fahrzeugantriebe. Die vorliegende Dissertation beschreibt bedeutende Fortschritte in der Entwicklung von LiFePO4 als Kathodenmaterial für Li-Ionen Batterien. Mithilfe einfacher Syntheseprozeduren konnten eine vollkommen neue Morphologie (mesokristallines LiFePo4) sowie ein nanostrukturiertes Material mit exzellenten elektrochemischen Eigenschaften hergestellt werden. Die neu entwickelten Verfahren zur Synthese von LiFePo4 sind einschrittig und bei signifikant niedrigeren Temperaturen im Vergleich zu konventionellen Methoden. Die Verwendung von preisgünstigen und umweltfreundlichen Ausgangsstoffen stellt einen grünen Herstellungsweg für die large scale Synthese dar. Mittels des neuen Synthesekonzepts konnte meso- und nanostrukturiertes LiFe PO4 generiert werden. Die Methode ist allerdings auch auf andere phospho-olivin Materialien (LiCoPO4, LiMnPO4) anwendbar. Batterietests der besten Materialien (nanostrukturiertes LiFePO4 mit Kohlenstoffnanobeschichtung) ergeben eine mögliche Energiespeicherung von 94%.
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Pečko, Aleksej. "Ličio geležies fosfato baterijų iškrovimo proceso tyrimas". Master's thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20130313_093936-82852.
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Darbe yra pateikti ličio geležies fosfato baterijų iškrovimo prie įvairių temperatūrų proceso tyrimai. Išanalizuotos įvairių rūšių baterijos ir nustatytos tinkamiausios baterijos panaudojimui elektra varomame transporte. Mokslinių straipsnių analizė, leido nustatyti ličio geležies fosfato baterijų trūkumus ir pranašumus bei išanalizuoti jų savybes ir ypatumus. Suprojektuotas eksperimentinių tyrimo stendas, pateikta tyrimo metodika ir atlikti ličio geležies fosfato baterijų iškrovimo prie skirtingų temperatūrų tyrimai. Išanalizuoti eksperimentinių tyrimų rezultatai, pateiktos išvados ir rekomendacijos.In this work a research of lithium iron phosphate batteries discharge process at different temperatures has been carried out. Different types of batteries have been analyzed and the most suitable battery type for electric transport is chosen. Scientific publication analysis allowed to identify the limitations of lithium iron phosphate batteries and to analyze the characteristics and peculiarities of this battery type. A battery testing stand has been designed, a research methodology has been presented and discharge tests of lithium iron phosphate batteries at normal and low temperatures have been performed. The results have been analyzed and findings together with recommendations have been presented.
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Huang, Jing-Yao, i 黃敬堯. "Microstructure and magnetoelectric properties of LiFe5O8 thin films prepared by pulsed laser deposition". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/847y45.
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碩士國立交通大學
電子物理系所
108
In this experiment, we successfully grew LiFe5O8(LFO) thin film on SrTiO3 (100) substrate by pulsed laser deposition (PLD) at 580 ℃. X-ray diffraction (XRD) showed that the obtained LFO films were phase pure with typical spinel structure. However, the films were predominantly (100)-oriented mottling with minor (111)-and(110)-oriented grains. XRD rocking curve showed that full width at half maximum of the (400) diffraction peak was ~0.06°, indicating excellent crystallinity of the films. Scanning electron microscope (SEM) analysis showed that surface morphology of the films was non-uniform with significant out growth, featuring a three-dimensional growth mode presumably due to the large lattice mismatch between film and substrate. The film thickness revealed by crossectional SEM image was about 40 nm. The temperature-dependent magnetic susceptibility was measured by superconducting quantum interference device (SQUID) using both field-cooled and zero field-cooled schemes. The results indicated that there was no magnetic phase transition between 2~300 K. However, a spin-glass-like behavior was observed. Magnetic hysteresis measurements showed that the coercive field was higher with a lower saturation magnetization when the field was applied in plane. This may be due to the fact that magnetic moments tend to align in plane by the compressive in plane strain. The capacitance measurements showed an anomaly at ~50 K when an external field of ~3500 Oe was applied, suggesting a possible magneto-electric coupling at this temperature.
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Mali, Bhawana. "Tuning of Spin Reorientation and Compensation Transitions in Ferrites". Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5206.
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Ferrites have attracted the attention of scientists and engineers in the last few years because of a combination of ferrimagnetic and insulating character. This makes them suitable for high frequency devices in telecommunication and radar systems. The subsets of orthoferrites and spinel ferrites form the focus in this thesis. Magnetic interactions between 4f and 3d electrons of rare earth and transition metal based perovskite oxides give rise to several exciting properties, such as magnetoelectric effect, multiferroicity, spin-reorientation transition, magnetic compensation, magnetization reversal, and spin switching. Perovskite structure of orthoferrites allows a great deal of flexibility for doping in the A and B sites. By choosing a suitable dopant with optimum concentration, many properties of the parent compound can be tuned. We were motivated to raise the spin reorientation transition temperature of RFeO3 to as near as the room temperature by doping either sites. In this study, several interesting phenomena of doped orthoferrites will be discussed. Alongside, multifunctional spinel ferrites offering novel electrical and magnetic properties are explored. Their structural and magnetic properties were tuned by varying the cation distribution which has an influence on many magnetic properties and magnetic compensation phenomena.
The work presented in this thesis is broadly divided into three parts. In the first part, B-site doping (50% Cr) and its effect on the magnetic properties of orthoferrites have been detailed, especially changes in the spin reorientation transition temperature of TbFeO3 (TbFe0.5Cr0.5O3). A clear evidence of Griffiths phase was observed which was presumably due to short range spin fluctuations. This was later confirmed from the results of neutron diffraction and thermal conductivity measurement. Further, a signature of spin-phonon coupling was observed in the Raman spectroscopy data. In the second part, variations in the magnetic properties of SmFeO3 single crystal have been illustrated by doping the A-site with Yttrium. SmFeO3 has the highest spin reorientation transition temperature (420 K–460 K) and it is known to reorient from Γ4 to Γ2 magnetic spin configuration. When doped with a non-magnetic element as Yttrium, not only was this transition temperature brought to room temperature but also a new spin configuration was induced (Γ3) that was not observed in any of the parent RFeO3 compounds. The third and final part of the thesis discusses the results of a spinel ferrite LiFe5O8 whose cation distribution has been mapped in the octahedral and tetrahedral sites. A study of the effect of Cr doping in LiFe5O8 and the distribution of the dopant ions in tetrahedral and octahedral sites has resulted in interesting magnetic transitions which are highlighted here.UGC
19
Jheng, Yuan-Ruei, i 鄭元瑞. "Reactive sputtering of LiFePO4-xNy". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/35450119904270968767.
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碩士逢甲大學
材料科學與工程學系
101
Rechargeable lithium ion batteries have emerged as one of the important power sources for various mobile devices such as cellular phones, cameras, and notebook computers due to high energy density and excellent cyclic performance. In order to reduce weights and volumes for mobile devices, the demands of lighter and thinner batteries are increasing. As the sizes of batteries are scaled down to micrometer/nanometer rang, the concept of thin film batteries have become inevitable. Lithium ion batteries has been commercialized for a long time. It can be observed that lithium ion batteries was lively used in mobile phone and notebook. The cathode materials for these lithium ion batteries is usually used LiCoO2 due to its stable electrochemical performance, simply process. Therefore, it is good choice to used LiCoO2 for the cathode of lithium ion batteries. However, because Co is expensive and unfriendly to environment, many researchers were used the other materials to replace LiCoO2. LiFePO4 is a popular cathode materials for lithium ion batteries due to good electrochemical performances, low cost, high safety. However, it is nearly an electronic insulator with conductivity as low as 10−9 Scm−1, and also shows low Li ion transport rate over the LiFePO4/FePO4 two-phase boundary during the charge-discharge process. By improving the preparation processes, the electrochemical properties of LiFePO4 can be enhanced. Recently, many researchers have been demonstrated that improvement of LiFePO4 electronic conductivity, such as coating carbon and doping transition metal. Lithium iron phosphate (LiFePO4) thin films have been synthesized by reactive magnetron sputter deposition process. In order to increase the conductivity of LiFePO4 thin films, nitrogen gas has been introduced during deposition, which results in nitrogen doping of LiFePO4 thin films. The LiFePO4-xNy thin films deposited under various nitrogen/argon ratios were characterized. The surface morphology and microstructures of as-deposited thin films were observed by scanning electron microscope (FESEM). The film crystallography and electronic conductivity was characterized by grazing angle X-ray diffraction (XRD) , Raman spectroscopy and four point probe. And confirmed by X-ray Photoelectron Spectrum and Fourier transform infrared spectroscopy nitrogen have successfully doped into LiFePO4. The results showed that the conductivity of the LiFePO4 thin films have been significantly improved by nitrogen doping. Under optimal condition, the LiFePO4-xNy thin films are able to sustain a current density as high as A/g (45 C-rate) during charge-discharge process, and Discharge plateau can be maintained over 3.2V. The capacity at A/g (10 C-rate) is higher than 100 mAh/g. All of these results nitrogen-doped can improve the electrochemical performance of LiFePO4 films.
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Su, Jian-Han, i 蘇建翰. "AC impedance study of LiFePO4 battery". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/63220811237042527132.
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碩士國立中興大學
物理學系所
100
Batteries using LiFePO4 as cathode, graphite as anode, and PAN/ EC/DMC/LiClO4 as gelled electrolyte were assembled. Thin films polycarbonate infiltrated with gelled electrolyte were also used as electrolytes. The interfaces between cathode/electrolyte, anode/electrolyte, and the assembled battery were studied by ac impedance analyzer. The complex impedance is fitted with equivalent circuit. The parameters of the battery such as resistance of the electrolyte, resistances of the electrode/electrolyte interfaces, the diffusion resistance, and the impedance of charge transfer were obtained. The charge-discharge characteristics of the battery were also studied.
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Liao, Kuo-Hung, i 廖國宏. "Study of LiFePO4 for Cathode Application". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/61750723096906618692.
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碩士國立暨南國際大學
應用化學系
92
Lithium iron phosphate (LiFePO4) as cathode material of secondary lithium battery has attracted wide attention in last few years. The major obstacles of LiFePO4 application are the low intrinsic conductivity and protecting environment required to stabilize the +2 valence state. Solid state sintering, carbon-mixed sintering, solution co-precipitation and chemical substitution methods were utilized to synthesize LiFePO4 and LiMnyFe1-yPO4. Properties of electrical conductivity, particle size and the y value of LiMnyFe1-yPO4 correlated with the charged/discharged performance were studied. Samples prepared by different methods will affect the purity and particle size of LiFePO4 while the carbon-mixed sintering displays a most significant improvement of electrical conductivity. The nonconclusive charged/discharged data of the manganese-substituted compounds may result from the complicated valence state of manganese. Details characterization associated with band structure study turn out to be crucial in finding an effective way to enhance the valence stability and electrical conductivity of LiMnyFe1-yPO4.
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Wu, Kuei-Chao, i 吳貴兆. "A study of LiFePO4 powder synthesis". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/40556772563826054587.
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碩士國立清華大學
材料科學工程學系
99
LiFePO4 powders were synthesized by the semi-solid-state method. Different from the traditional solid state method, this method combined a precipitation method with a post heat treatment. The self-assembled Fe precursor precipitates had a specialized morphology, which was unique. The mixture obtained by uniformly mixed the Fe precursor with sucrose was heat treated under 600-800℃ for the synthesis of LiFePO4/C. To optimize the carbon coating in the LiFePO4 powders, various amounts of carbon was added to the mixture prior to the high temperature treatment. It was found that sample with 15% sucrose addition sintered at 750℃ for 3 hours had a better carbon coating. Carbon here acted as a reducing agent to prevent divalent iron ions from oxidation, and the carbon coating on the LiFePO4 particles enhance the electronic conductivity. Moreover, carbon could suppress particles from growing at high temperature. LiFePO4/C doped with metal (eg. Mg doping) can also increase the electronic conductivity. In addition, it had higher surface area than LiFePO4/C without doping.
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Mathewson, Scott. "Experimental Measurements of LiFePO4 Battery Thermal Characteristics". Thesis, 2014. http://hdl.handle.net/10012/8378.
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A major challenge in the development of next generation electric and hybrid vehicle technology is the control and management of heat generation and operating temperatures. Vehicle performance, reliability and ultimately consumer market adoption are integrally dependent on successful battery thermal management designs. It will be shown that in the absence of active cooling, surface temperatures of operating lithium-ion batteries can reach as high as 50 °C, within 5 °C of the maximum safe operating temperature. Even in the presence of active cooling, surface temperatures greater than 45 °C are attainable. It is thus of paramount importance to electric vehicle and battery thermal management designers to quantify the effect of temperature and discharge rate on heat generation, energy output, and temperature response of operating lithium-ion batteries. This work presents a purely experimental thermal characterization of thermo-physical properties and operating behavior of a lithium-ion battery utilizing a promising electrode material, LiFePO4, in a prismatic pouch configuration.
Crucial to thermal modeling is accurate thermo-physical property input. Thermal resistance measurements were made using specially constructed battery samples. The thru-plane thermal conductivity of LiFePO4 positive electrode and negative electrode materials was found to be 1.79 ± 0.18 W/m°C and 1.17 ± 0.12 W/m°C respectively. The emissivity of the outer pouch was evaluated to enable accurate IR temperature detection and found to be 0.86.
Charge-discharge testing was performed to enable thermal management design solutions. Heat generated by the battery along with surface temperature and heat flux at distributed locations was measured using a purpose built apparatus containing cold plates supplied by a controlled cooling system. Heat flux measurements were consistently recorded at values approximately 400% higher at locations near the external tabs compared to measurements taken a relatively short distance down the battery surface.
The highest heat flux recorded was 3112 W/m2 near the negative electrode during a 4C discharge at 5 °C operating temperature. Total heat generated during a 4C discharge nearly doubled when operating temperature was decreased from 35 °C to 5 °C, illustrating a strong dependence of heat generation mechanisms on temperature. Peak heat generation rates followed the same trend and the maximum rate of 90.7 W occurred near the end of 5 °C, 4C discharge rate operation. As a result, the maximum value of total heat generated was 41.34 kJ during the same discharge conditions. The effect of increasing discharge rate from 1C to 4C caused heat generation to double for all operating temperatures due to the increased ohmic heating.
Heat generation was highest where the thermal gradient was largest. The largest gradient, near negative electrode current collector to external tab connection and was evaluated using IR thermography to be 0.632 °C/mm during 4C discharge with passive room temperature natural convection air cooling. Battery designs should utilize a greater connection thickness to minimize both electrical resistance and current density which both drive the dominant mode of heat generation, ohmic heating. Otherwise cooling solutions should be concentrated on this region to minimize the temperature gradient on the battery.
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Peng, Huai-ai, i 彭懷皚. "Lithiated perfluorosulfonate ionomer modified graphene/LiFePO4 Cathode". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/vn9w8c.
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碩士逢甲大學
材料科學所
100
In past, Lithium ion battery was usually used in mobile phone, digital camera, notebook, and other portable electronic product. Rapid development of electric vehicle industries pushes the Li-ion battery industry towards research and development of large-scale power batteries. LiFePO4 has been commercially employed as an important cathode active material, because of high theoretical specific capacity, excellent cycle stability, low cost, environment benignity. However LiFePO4 has the drawbacks of low Li-ion diffusion rate and poor electronic conductivity. In this study, lithiated perfluorosulfonate ionmer (LiNafion) was used as the binder and graphene as the conducting agent to modify LiFePO4 cathode. The results reveal that LiFePO4 electrodes with LiNafion binder show a stable chemical stability after cycling, and are capable of charging/discharging at 10 C rate. LiNafion can replace the traditional commercial adhesive PVdF binder, and act as an additional ionic conductor as well as a dispersion agent for graphene. The surface morphology observed by field emission scanning electron microscope (FE-SEM) shows that graphene can be distributed evenly between LiFePO4 particles and from 2-D conductive network, due to the high flexibility of graphene. LiFePO4/G-LiNafion electrode can be discharged at a rate as high as 10 C, because the charge transfer resistances are reduced by the graphene with a 2-D conducting network.
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Chien, Yung-Tang, i 簡詠堂. "Effects of Conductive Carbon for LiFePO4 Cathode". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/u87zh5.
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碩士國立臺南大學
綠色能源科技學系碩士班
103
Olivine-structured LiFePO4 has the advantages of high specific capacity, good safety attribute. However, poor electronic conductivity and low lithium ion diffusion coefficient are still the main obstacles that limit the electrochemical intercalation/extraction of lithium ions and cause a fast decay in charge/discharge capacities at high rates. Conductive carbon were used as the substrate with excellent conductivity and a well conductive network. A conductive carbon as a performance-improved LiFePO4 cathode material for lithium-ion batteries, Super P nano carbon spheres/KS6 flake graphite/CCB-S3 nano hollow carbon spheres, three kinds of conductive carbon use in as experimental design ternary mixture design method. The conductive carbon feature and electrochemical property of LiFePO4 cathode was investigate by scanning electron microscopy (SEM), and electrochemical methods. The KS6-25% and CCB-S3-75% conductive carbon has a good conductive network for LiFePO4 cathode and protrudes the higher good cell performance of the cycle life.
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Cheng-ChangOu i 歐承昌. "Synthesis and Characterization of LiFePO4 Cathode Material". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/09263384519400256820.
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碩士國立成功大學
化學工程學系碩博士班
98
LiFePO4 has been actively investigated as cathode material for Li ion secondary batteries. LiFePO4 has attracted great interest due to its low cost , thermal stability, and environment benignity of its element. The major obstacles of LiFePO4 are two intrinsic conductivity. Improving the conductivity have two methods to solve via two main techniques; One is the reduction of the grain size, it is achieved by solution methods make LiFePO4. In this study, we synthesize LiFePO4 by sol-gel method for cathode material of secondary Li ion batteries, and use ascorbic acid as reducing agent; Two is the manufacture of LiFePO4 coated with high conductivity material; like organic material of carbon source and electronically metal. In this study, we aid fructose and try to find out the best synthetic condition by various thermal treatment. The grain size of LiFePO4 is increasing with the thermal treatment temperature. We also find that the optimum particle size (32-38nm) are sintered at 500℃ and the lower DC electrical resistivity is at 600℃ in this experiment. From this experiment, when sintered temperature approximately (500-700℃) increase , the crystalline strength and grain size also increase with temperature. In the conductive substance addition, the source of carbon which is fructose or ascorbic acid added to LiFePO4 that could increase conductivity of materials obviously, and decrease particle size. The conductivity increasing limit to the quantity of additions.
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Tu, Heng-Shin, i 杜恒欣. "Micelle Synthesis of Carbon Supported LiFePO4 Nanoparticles". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/10994641280598808648.
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碩士國立暨南國際大學
應用化學系
94
Lithium iron phosphate (LiFePO4) as cathode material of secondary lithium battery has attracted wide attention in last few years. The major problem of LiFePO4 is its low intrinsic conductivity which will reduce the charge/discharge ability in high current and decrease the life cycle. The required protecting environment to stabilize the +2 valence state is resulting the process complexity and high running cost for mass production. In this thesis, a reverse micelle system is designed and developed to cover the LiFePO4 precursor. In the following high temperature sintering, carbonized micelle structure provides the advantages in preventing air oxidation of iron（ion）, restricting grain growth and limiting the diffusion length in nano-scale. The resulting LiFePO4 compound generates the unique properties of high conductivity and nano-scale particle size. This work demonstrates a novel reverse micelle process for mass production. The correlation of electrochemical property, conductivity and fine structure are systematic studied.
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吳孟哲. "Optical studies of LiFePO4 and LiMnPO4 nanoparticles". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/36081074697155188208.
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碩士國立臺灣師範大學
物理學系
102
We present x-ray powder diffraction, Raman-scattering, and spectroscopic ellipsometry measurements of LiMPO4 (M = Fe, Mn) nanoparticles. Our goal is to explore the influence of finite-size effects on the lattice dynamics and electronic structures in these materials by optical spectroscopy. At room temperature, x-ray powder diffraction data show that the lattice constants of nanoparticles are slightly larger than those of bulk samples. Raman-scattering spectra of LiFePO4 and LiMnPO4 nanoparticles show eleven and seven phonon modes. The phonon modes are observed at about 145 cm-1, 158 cm-1, 197 cm-1, 444 cm-1, 584 cm-1, 630 cm-1, 658 cm-1, 950 cm-1, 996 cm-1, 1068 cm-1, and 1140 cm-1 for LiFePO4 nanoparticles. Similarly, the phonon modes appear at about 93 cm-1, 142 cm-1, 437 cm-1, 585 cm-1, 948 cm-1, 1005 cm-1, and 1066 cm-1 for LiMnPO4 nanoparticles. They are red shifted in frequency by 1 ~ 2 cm-1 compared with that of bulk counterpart. This slight redshift observed in the Raman phonon modes of nanoparticles can be attributed to the combination effect of strain induced by amorphous layer and v phonon confinement. Furthermore, with decreasing temperature, no anomaly of phonon parameters was observed near the antiferromagnetic ordering temperature in both LiFePO4 single crystal and nanoparticles. Additionally, the frequencies of Raman phonon modes in Li0.5FePO4 and LiFePO4 nanoparticles are close, however, their intensities differ. The absorption spectra determined from spectroscopic ellipsometry analysis of LiFePO4 and LiMnPO4 show several absorption bands in the spectral range from 3.8 to 6.4 eV. Their assignments are based on the predictions of first-principles calculations. Finally, the values of direct band gap of LiFePO4 single crystal and nanoparticles are estimated to be about 3.80 ± 0.1 eV and 3.45 ± 0.1 eV. The 3.75 ± 0.1 eV and 4.80 ± 0.1 eV band gap are obtained for LiMnPO4 bulk and nanoparticles.
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Tsai, Tsung-Rung, i 蔡宗榮. "High Frequency Discharging Characteristics of LiFePO4 Battery". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/47308527379854566262.
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碩士國立中山大學
電機工程學系研究所
98
This thesis investigates the high frequency discharging characteristics of the lithium iron phosphate battery. The investigation focuses on effects of the high-frequency current on the dischargeable capacity of the battery. Included are the current profiles of triangle, saw-tooth, and trapezoidal waves, which are produced from commonly used DC-DC converters. Experimental results show that the current with the higher frequency has less dischargeable capacity. On the other hand, the converter current resonating into and out from the battery results the additional losses. The possible reasons that affect the discharged capacities are explained by the equivalent circuit of the battery.
30
Syue, Zong-Wei, i 薛宗偉. "Study of SOC Estimation for LiFePO4 Battery". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/96945572412159894970.
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碩士雲林科技大學
電機工程系碩士班
98
This thesis studies the charging and discharging characteristics of LiFePO4 battery and SOC method. The charging and discharging characteristics of LiFePO4 battery are investigated and analyzed, the experimental results can be used to design or exploit a quick charger. The measurement of residual capacity is based on the improved coulomb counting method and open-circuit voltage method, the accuracy of the measurement of residual capacity can be improved. The control strategy is implemented in a DSP. The effectiveness of the designed battery charger is verified by experimentation.
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Liu, Hsin-yen, i 劉炘彥. "The Preparation and Characterization of α-LiFeO2-based and Goethite-type LiFeO2-based Cathode Materials". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/35323092365360575215.
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碩士大同大學
材料工程學系(所)
94
Abstract α-LiFeO2-based and goethite-type LiFeO2 powders were prepared with ion-exchanging method by using β-FeOOH and α-FeOOH as precursors those were derived from the hydrolysis of FeCl3 and FeCl2 in aqueous solutions, respectively. Among the lithium salts those are soluble in ethanol; LiOH had been proved as the most effective ion-exchanging salt. The composition, the crystalline structure, and the morphology of the prepared powders are determined with ICP, XRD, and SEM, respectively. The electrochemical properties, reaction occurred, and structure change upon cycling are investigated with capacity retention study, cyclic voltammetry, in-situ XANES, and in-situ XRD. The nano-sized α-LiFeO2-based powders prepared in the study are electrochemical active and exhibit reversible capacities ranging between 50 and 80 mAh/g due to the reaction of Fe2+/Fe3+ redox couple. Nano-sized α-FeOOH and goethite-type LiFeO2-based powders prepared by having α-FeOOH ion-exchanged with LiOH in ethanol solution exhibit poor cycleability and low specific capacity in Fe2+ ⇋ Fe3+ redox reaction, respectively.
32
Chen, Yun-Geng, i 陳運庚. "Electrochemical Properties of LiFePO4 Prepared Via Ball-milling". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/48788537085535752372.
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碩士國立中央大學
化學工程與材料工程研究所
96
LiFePO4 cathode materials with distinct particle sizes were prepared by a planetary ball-milling method. The effect of particle size on the morphology, thermal stability and electrochemical performance of LiFePO4 cathode materials was investigated. The ball-milling method decreased particle size, thereby reducing the length of diffusion and improving the reversibility of the lithium ion intercalation/deintercalation. It is worth noting that the small particle sample prepared using malonic acid as a carbon source achieved a high capacity of 160 mAh g-1 at a 0.1 C-rate and had a very flat capacity curve. However, the large particle sample decayed more dramatically in capacity than the small particle size samples at high C- rates. The improvement in electrode performance was mainly due to the nanometric fine particles, the small size distribution of the product, and the increase in electronic conductivity as a result of carbon coating. The structure and morphology of LiFePO4 samples were characterized with XRD, FE-SEM, TEM, EDS, and DSC techniques.
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Hsiao, Wei-Cheng, i 蕭維誠. "Microprocessor Based Capacity Estimating System for LiFePO4 Battery". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/95091246784289885524.
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碩士國立高雄應用科技大學
電機工程系博碩士班
102
The charging/discharging current of LiFePO4 battery is larger than lead-acid battery. LiFePO4 is a potential energy storage devices and has high energy density, and the variation of each cell voltage is small during the charge and discharge process. Therefore, comparing with the laed-acid battery, the capacity of the LiFePO4 battery will not reduce sharply under large current discharging. Therefore, the LiFePO4 battery has opportunity to replace the laed-acid battery in the future. The purpose of this thesis is to apply the technologies of battery capacity measurement, microprocessor/hardware, and web based programming to develop a prototype of Battery Management System (BMS). The main goal of this thesis contains establishment and analysis of battery charging/discharging curve, close loop load voltage associated with look up table method to estimate the battery residual capacity. Meanwhile, the column method is adopted to measure and calculate the incremental battery capacity during charging period. Voltage/current extracting circuit and microprocessor based module are developed to integration and testing. Finally, this web based BMS is designed to communicate with microprocessor via Modbus protocol and display battery information on its Graphical User Interface (GUI). The practicality of the proposed system has been justified by the proposed system testing.
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Lin, Chien-Ting, i 林建霆. "On Adaptive SoH Equalization for LiFePO4 Battery Packs". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/89678228716231097488.
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碩士國立交通大學
電控工程研究所
102
Equalizing SoH between batteries is a critical information for Battery Power System. It can not only decrease the SoH deviation between batteries, but also increase total available charge until end of life. To address this issue, this thesis proposes “On Adaptive SoH Equalization for LiFePO4 Battery Packs.” In temperature difference distribution of ≦5℃ from module to module, our SoH equalizer uses controlled DoD to slow the rate of capacity fading. By realizing adaptive control loop, we don’t need exact cycle-life model to determine DoD value. The appropriate control proportion K is determined by our adaptive control algorithm. Our controller can increase 14.0% available charge in simulation case with different temperature. Moreover, it can also increase 13.3% available charge in simulation case with both different temperature and capacity. The implementation includes SoH equalizer and battery management system. The platform provides both complete SoH equalization and Battery Power System protection. Experimental results that cycled an aged module and three fresh modules indicated that SoH gap between each module didn’t reduce. Other controlled experiment cycled 4 fresh modules, and result showed the SoH gap between each module was narrowed.
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Zhou, Bo-Hao, i 周博豪. "Fading mechanism of LiFePO4/MCMB lithium ion battery". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/86602969783412288395.
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碩士大同大學
材料工程學系(所)
103
500 mAh LiFePO4/MCMB pouch-type cells with various anode to cathode (A/C) loading ratios are prepared for the study. The effects of the loading ratio on the cycling performance are investigated by capacity retention and EIS studies. From the postmortem analysis with XRD, SEM, ATR-FTIR studies for the cycled cathodes and anodes, and the capacity retention and EIS studies for the coin cells assembled with cycled cathodes and anodes, respectively, the mechanism of the capacity fade of the LiFePO4/MCMB cells prepared with various A/C loading ratios are investigated. Lithium plating was found to be the main cause for the capacity loss at A/C ratio lower than 1, while the irreversible lithium loss and Li trapped in voids of anode material cause the capacity lowering at high A/C loading ratio. Furthermore, cells prepared with A/C loading ratios of 0.9 and 1.3 manifest higher charge transfer resistance than that with A/C ratio of 1.1. In addition to the factors, iron loss and severe lithium loss from LiFePO4 accerlate the capacity fade of LiFePO4/MCMB cell upon cycling at 60oC.
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Lai, Huang-Tsung, i 賴黃宗. "A study of the magnetic measurement of LiFePO4". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/55891718979856864014.
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碩士國立交通大學
理學院碩士在職專班網路學習學程
97
Lithium-ion betteries which are used more widly in our daily life have been an important electric storage equipment because of its property of high energy density and reuse. LiFePO4 has been considered to be one of the most promising candidates for the next generation lithium ion batteries cathode materials. There are many different impurities in LiFePO4 with different methods for preparation. These impurities will affect the electric perfomance of Li-ion betteries. We hope to know how many impurities there are in our LiFePO4 samples and the influence of these impurities on the electric performance of Li-ion betteries. We analyzed the magentization curves, M(H), M(T), and hysteresis, of the LiFePO4 samples. We found steeply up lines at low fields in M(H) curves that shows the saturate magenitization of maghemite, and loops in hysteresis curves that shows the magnetism of Fe2P impurities which is ferromagnetic. We can use the characteristics of these curves to predict the electric performance of Li-ion betteries which use LiFePO4 as cathod materials. This mathod can be a tool to check the quality of LiFePO4 materials primarily.
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林孟令. "Study of Characteristics for LiFePO4 and LiFexMyPOz Batteries". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/95024885112290079273.
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碩士國立彰化師範大學
電機工程學系
100
ABSTRACT The main object of this thesis is to study the characteristics of LiFePO4 and LiFexMyPOz batteries with constant voltage / constant current charging strategy. Several experiments with different charging currents are carried out and corresponding information of temperature, stored charge and stored energy variations are all measured and recorded by a testing platform composed of a personal computer, a power supply, an electrical load and a digital meter. From the experimental results, it is seen that LiFexMyPOz batteries has highest 96 % energy efficiency with 0.1 C charging and also can store 55.9 % charge (Ah) and 47.3 % energy (Wh) higher than LiFePO4 batteries. Although the charging time can be reduced with higher charging current, the temperature would also become higher.
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Yeh, Shun-Mao, i 葉順茂. "Synthesis LiFePO4/C Composited through the Electrospinning Method". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/14446712162542349735.
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碩士國立高雄大學
電機工程學系-工業技術整合產業研發碩士專班
100
The single crystal nano-scale LiFePO4/C was successfully synthesized through an electrospinning method. LiFePO4/C nanowire materials were synthesized by using a electrospinning and sol-gel method. The mixture of the polyvinyl alcohol (PVA) and precursor of LiFePO4 was used as the electronspinning material. The desired characteristics were obtained by different setting parameters of the electron spinning conditions (injection rate, sintered temperature and concentration). The nano-scale size were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The outer nano-scale layer of amorphous carbon was successfully synthesized using the electrospinning method. TEM micrographs show amorphous carbon layer which was evenly coated on the LiFePO4 and would not influence the crystallization of LiFePO4. The XRD results show that crystallization of LiFePO4 proceeded after sintering ( 500°C、600°C、700°C) and free of impurity. The SEM analysis reveals that the LiFePO4 /PVA nano-structure was successfully synthesized. Decrease in the PVA concentration decreased the thickness of carbon coating layer.
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CHANG, CHIH-YUAN, i 張智淵. "A Fast Charging Balancing Circuit for LiFePO4 Battery". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/t27ay9.
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碩士國立虎尾科技大學
電機工程系碩士班
106
In this thesis, a fast charging balancing circuit for LiFePO4 battery is proposed to tackle the voltage imbalance problem among lithium battery string. During the lithium battery charging process, the occurrence of voltage imbalance will activate the fast balancing mechanism. The expected balancing circuit includes the following features:(1) handling the maximum voltage difference between the odd-numbered and even-numbered battery string without extra energy storage device, thus promoting the working efficiency; (2) requiring only one converter to complete the energy transfer for voltage balance, thus making the circuit structure simple; (3) bi-directional energy flow and electrical isolation; (4) using active power switches to complete the balance control switching, thus free from mechanic switching limitation and shrinking the circuit size; (5) applying single chip control technology and measuring the voltage of every single battery, to achieve the maximal effectiveness resulting from balanced charging. Finally, the practical application of fast balancing experiments on LiFePO4 battery pack 28.8V/2.5Ah, the experimental results verification of the balancing circuit attached fast balancing function.
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Feng, Hai. "A novel co-precipitation method for carbon-free LiFePO4 and investigation into potential LiFEPO4-C cathode materials for lithium-ion batteries". Thesis, 2015. http://hdl.handle.net/1959.7/uws:34599.
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Lithium iron phosphate (LiFePO4) is a promising cathode material for lithium-ion batteries. In the past few years many improvements have led to consistent cycling capabilities, even at high rates. LiFePO4 is being commercialized as a cathode material in batteries for power tools, and is a serious candidate for the future batteries of hybrid-electric or electric vehicles. It can also be commercialized for other applications requiring a low-cost and safe battery, but its low intrinsic electrical conductivity and low Li-ion diffusion are two major disadvantages. Many groups have shown that battery performance can be enhanced by addition of carbon, during synthesis or post-synthesis carbon coating through various techniques to improve electrical conductivity. Simplification or even minimization of carbon-coating methods is one area of improvement which could help to reduce cost and increase efficiency. These carbon additives can cause multiple effects on purity, crystallinity and the electrochemical performance of the final cathode material (LiFePO4) and therefore makes it difficult to optimise the quantity and specific type of carbon that needs to be added during the synthesis of LiFePO4. All synthetic procedures reported in the literature, however, show that carbon is always present in some form in the final product. In this thesis study, in order to evaluate the effect of various carbon additives unambiguously, a novel one-step co-precipitation method was developed for synthesis of carbon-free LiFePO4. A series of LiFePO4/Carbon composites were prepared where the composites were synthesised at 550, 650 and 750°C containing 5, 10 or 20 wt% carbons. Two forms of carbon additives were tested; single wall carbon nanotubes (SWCNT) and carbon black (CB). These carbons were added at one of two different stages; (1) during pre-synthesis, mixed with the LiFePO4 precursors, or (2) in post-synthesis, during the electrode preparation. This approach helped to investigate the effect that the carbon type, carbon content, mode of mixing (pre synthesis or post synthesis) and temperature have on the electrochemical performance of the active component. The topic of electron conductivity and Li-ion diffusion LiFePO4 is also very relevant, especially since this material is now touted as an important high-rate capability cathode. To investigate these effects, cyclic voltammetry, charge-discharge and electrochemical impedance spectroscopy measurements were performed. It was found that the cell discharge capacity, rate capacity and electronic conductivity of the electrode depended on the type of carbon used. The use of a 5 wt. % loading of SWCNTs as conductive additive to LiFePO4 composites prepared at 750 °C was found to improve the electrochemical performance of cells compared to cells containing CB additives. The LiFePO4 with 5 wt. % SWCNTs mixed pre-synthesis and then synthesised at 750 °C demonstrates a smaller resistance to charge-transfer (RCT = 59Ω) and good kinetic behaviour (2.9 x 10-8 cm2/s), and has the highest specific capacity (93 mAh/g and 48 mAh/g at C/20 and C/5 respectively) than any other sample except for the one with 10 wt% SWCNT. The latter demonstrates slightly improved specific capacity at C/20 (94 mAh/g) and better Li-ion kinetic behaviour (3.3 x 10-7 cm2/s) but a worse specific capacity at C/5 (46 mAh/g), probably because the charge-transfer resistance is significantly higher (RCT = 239 Ω). Therefore, the optimisation of cell performance involves optimisation of Li-ion and electron transport and the charge transfer at the electrode/electrolyte interface. Therefore, it is important to note that the material synthesised according to the novel, single-step, co-precipitation procedure described in this thesis can be applied to many other LiFePO4-carbon composite cathode materials, to compare and evaluate the effect of various carbon additives on the electrochemical performance of cathode materials.
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Hsu, Yu-Cheng, i 許郁承. "Preparation of LiFePO4/C Cathode Materials by Hydrothermal Mathod". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/y44rf4.
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碩士明志科技大學
化學工程系碩士班
103
In this study, carbon-coated lithium iron phosphate (LiFePO4) cathode materials were synthesized by hydrothermally from LiOH, FeSO4 and H3PO4 as raw materials in aqueous solution at 180 °C for 3 h followed by being annealed at 600 °C for 10 h under a 95%Ar+5%H2 atmosphere. Then, the glucose aqueous solution was mixed with LiFePO4 powders and dried at 120 °C for 12 h. The dried powders were annealed at 600 °C for 10 h to obtain the lithium iron phosphate/carbon (LiFePO4/C) cathode composites. The structural, morphological and electrochemical properties were investigated by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Raman scattering spectra, and constant current charge–discharge cycling test. The results show that the specific discharge capacities at 0.1C is 94 mAh/g. And the spray drying was applied in the carbon-coating process, the specific discharge capacities at 0.1C can be promoted to 139 mAh/g.
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Lee, CHIH-HAO, i 李志豪. "Application and development of LiFePO4 Batteries in Automotive Industry". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/3jaur4.
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碩士國立臺北科技大學
車輛工程系所
99
Due to high oil prices and global wide high inflation, there are attempts to increase the oil production in order to contain the raise of oil prices from time to time. However these acts also accelerate the consumption of Earth’s precious resources. Under the premise of difficulty in maintaining high crude oil reserves, countries around the world are likely to shift their focuses from amount of crude oil reserves to alternative energy sources such as battery reverses. Generally speaking, there are two types of batteries, one of them is called battery which is applied in electrical energy storage, and the other type is called cell which is used for power generation. Both of them can improve the energy reused from the natural sources. For example solar cells, fuel cells, and etc. can be used as alternative energy sources to reduce fossil fuel emissions. By improving the efficiency of energy conversion, rechargeable batteries can achieve effective energy conservation. This study will focus on the new generation of lithium battery, LiFePO4, which is regarded as the most promising development in the future. There is trend for the automotive to be powered by electric; therefore there will be countless opportunities in developing effective electrical motor, battery system, electric car chassis, power control and other crucial components such as electrical compressor, electrical break system, fast battery charger system and etc. This thesis will prolog with LiFePO4 batteries in comparisons of different alternative technologies and their pros. and cons.; then expand to the analysis and discussions of its industrial value chains; and observe the positioning and development trends of LiFePO4 batteries in automotive industry.
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Liang, Yi-Min, i 梁翊民. "On-line State-of-Health Estimation for LiFePO4 Battery". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/sp3q7x.
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碩士國立中山大學
電機工程學系研究所
104
The demand of batteries for electric vehicle (EV) and Energy Storage System (ESS) is increasing. After battery has been used for a long time, the actual available capacity of battery will decrease, so State-of-Health (SOH) estimation is important in EV and ESS operations. An on-line SOH estimation method is proposed in the thesis. It is different from the conventional off-line estimation methods that need to remove battery from the system and connect to other devices. The key component in the proposed SOH estimation procedure is to obtain aging indicators according to the data from aging experiment performed off-line, and then use the indicators, including model parameters in a battery equivalent circuit to estimate SOH. Test data are used to determine the model parameter values during different battery ages by least square error method. The battery characteristic parameters computed at each age of the battery are then used in an Artificial Neural Network (ANN) to train and setup the automatic SOH estimator. In the proposed procedure, a regression model is used to determine the relationship of battery open-circuit voltage with State-of-Charge (SOC) and SOH. An on-line SOH estimation can be achieved after the battery open-circuit voltage and the equivalent circuit model parameters are calculated real time and fed into the ANN model. Test results indicate that the average absolute error of the proposed SOH estimator under different usage scenarios is 1.7732% based on 5 LiFePO4 batteries.
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Chen, Cheng-lun, i 陳正倫. "Substrate effect induced microstructural evolution of LiFePO4 thin films". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/82341184438681442825.
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碩士逢甲大學
材料科學所
97
Current, digital cameras, i-phone, notebook computers and netbooks have become the global mainstreams of electronic industries. As the weight and volume of these portable devices continuously decrease, the search for smaller, lighter, and higher power density power sources have never stopped. In order to meet these requirements, the concept of Thin Film Batteries (TFB), or all solid state micro-batteries, has therefore been of great interest. With only a few micron meters of thickness or less, thin film batteries are compatible with micron electro-mechanical devices, and can be the back-up power for SRAM, as well. This research used pure LiFePO4 thin films as the cathode materials for thin film batteries. Based on previous studies of our laboratory, that interdiffusion occurs between thin films and substrates, the substrate effects and interdiffusion between cathodes and substrates were investigated. The results indicate significant microstructural evolution of LiFePO4 thin films, and improved electrochemical performances. In this study, Carbon-free LiFePO4 thin films was deposited onto different substrates(Si3N4, Ti/Si3N4, Ag/Si3N4 and Ag/S.S.). The LiFePO4 films were annealed at 700 ℃ with Joule heating and radiation heating, respectively. X-ray diffraction (XRD) revealed that the films with radiation heating were well crystallized, free of second phases, may be textured with a (011) orientation. Comparing the properties of these thin films indicated a relationship between the microstructures and the types of substrates. The conductivity of thin films were greatly improved by the diffusion of Ag. The distribution of Ag in the LiFePO4 thin films were investigated by using a X-ray photoelectron spectroscope (XPS) and a transmission electron microscope (TEM). The thin film (LiFePO4/Ag/S.S.) showed a typical discharge voltage of LiFePO4 at 3.4 V.
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Lin, Bo-Shun, i 林柏勳. "Rf magnetron sputter deposition of LiFePO4/C thin films". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/83944845425040391200.
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碩士逢甲大學
材料科學所
94
Secondary lithium batteries have been the primary power supply components for various portable electronic devices, such as cell phones and notebook computers. However, as the weight and volume of the portable devices continuously decrease, the search for smaller, lighter, and higher power density power sources has never stopped. In order to meet these requirements, the concept of Thin Film Batteries (TFB), or all solid state micro-batteries, has therefore been of great interest. With only a few micron meters of thickness or less, thin film batteries are compatible with micron electro-mechanical devices, and can be the back-up power for SRAM, as well. This research uses LiFePO4/C as cathode material of thin film batteries. Through substrate bias assist sputtering LiFePO4/C thin film, then control the energy of ion bombard to achieve in-situ modification. Moreover, it also uses vacuum annealing treatment to develop high capacity and high discharge voltage cathode materials, and increases electric conductivity of thin film effectively. The result shows that adding the titanium under layer can increase the crystalline of LiFePO4/C, and after anneal treatment, the LiFePO4/C thin film and titanium under layer have diffusion reciprocal, and adding the titanium under layer can have better cycle life and adhesion，but capacity lower then non-adding titanium under layer thin film.
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Lin, Yu-Chi, i 林育吉. "A Study on the Synthesis and Characteristics of LiFePO4". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/20913285419916029394.
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碩士國立屏東教育大學
應用物理系
101
Lithium iron phosphate (LiFePO4) has many merits as cathode material of secondary lithium battery which has been popular in last few years. However, the major drawbacks of LiFePO4 are slow lithium ion diffusion and poor electronic conductivity. In the study, lithium iron phosphate powders were prepared by a facile hydrothermal reaction under a nitrogen atmosphere or an air atmosphere. The particle characteristics and electricity properties of the LiFePO4 powders were also investigated. The XRD analysis indicated that the single phase of LiFePO4 can be achieved through the hydrothermal synthesis route in the study. It is found that the formation of Fe3+-containing impurity phases can be prevented in the hydrothermal reaction by adding a reducing agent or under nitrogen atmosphere. In addition, the control of both the purity and the particle size can also be carried out through the preparation conditions of LiFePO4. The experimental results show that the use of a polymer additive to the precursors in the synthesis of LiFePO4 can also prevent the abnormal particle growth but increase the electric conductivity of the samples. Therefore, it is very important to find a best LiFePO4/C ratio with hope to get the lithium ion battery of a high capability.
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Chung, Pao-Chia, i 鍾嘉寶. "Preparation of LiFePO4 Composite Cathode Material and Performance Analysis". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/31716386724887233983.
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碩士國立新竹教育大學
應用科學系碩士班
99
In this project, we use ferrous sulfate / hydrogen peroxide and phosphoric acid / ammonia as the starting materials to produce iron phosphate precipitates under pH value in 2. After mixing with lithium carbonate in a certain percentage, the precursors were sintered at 700℃ in nitrogen. Then we obtained the crystal-like good olivine lithium iron phosphate. We also added different dispersants / iron phosphate coating agent in the precipitation process, to study the influence of electric properties of products. The results indicated: the selected dispersant, can achieve a well dispersion, particle size in 100nm for all products. When adding PEI as the coating agent, the electric capacity of products can be improved. But if adding PEI coating agent with the dispersant in the same time, they did not necessarily obtain a better effect. Only in case of NSFC with PEI can be best, capacitance up to 141 mAh/g.
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Ke, Wei-Hsin, i 柯惟馨. "STUDY ON IMPROVING ELECTROCHEMICAL PROPERTIES OF LiFePO4 CATHODE MATERIALS". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/12652322916220502508.
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博士大同大學
材料工程學系(所)
97
Among several materials under development for use as cathodes in lithium ion batteries, orthophosphates LiMPO4 (M = Mn, Fe, Co, Ni) structure to olivine are intensively studied as lithium insertion compounds. Among the LiMPO4, lithium iron phosphate LiFePO4 have been recognized as a promising candidate for Li-battery cathode due to the low cost, environmental benignity, cycling stability, and high theoretical capacity of 170 mAhg-1. However, the poor conductivity, resulting from the low lithium-ion diffusion rate and low electronic conductivity in the LiFePO4 phase, has posed a bottleneck for commercial applications. In this study, pure olivine LiFePO4 has been successfully prepared with co-precipitation, solid-state, emulsion-drying, microwave assisted synthesis and solution method. In the aspect of co-precipitation, small-size and homogeneous synthesized powders with electronically conductive coatings could be fabricated to improve the poor conductivity of the powders. The cell containing the LiFePO4 cathode prepared by coprecipitation method can achieve high specific capacity (143mAhg-1) even after the 100th cycle with 1C charge/discharge rate at 50�aC. LiFePO4 powders prepared by solution method were also investigated in this work. The LiFePO4 particles with carbon coating synthesized from different carbon precursors are attempted to improve electrochemical performance. This result reveals LiFePO4/C prepared from PVA precursor exhibits superior electrochemical performance. The carbon coating synthesized from PVA pyrolysis can provide moderate carbon content and high graphitized pyrolysis carbon. Moreover, displacement ions (M= Mg2+, Ni2+, Al3+, or V3+) with ionic radius similar to or smaller than that of Fe2+ will be attempted to displace Fe2+ into the Fe-site to form LiFe0.95M0.05PO4 samples to improve electrochemical performance. The mean particle size of all samples, independent of doping species, is about 6 �b 0.5�慆. All samples with carbon content of about 3wt.% carbon coating in this study have similar BET surface area (about 18~20.5 m2g-1). It can be found that the synergetic effect of the supervalent doping and lattice expansion is beneficial to the electrochemical performance of cathode materials, especially under high C rate. Hence the powder (LiFe0.95V0.05PO4) with the V doping of trivalence and largest volume of unit cell (longest Li-O bond length) exhibits highest discharging capacity 152 mAh/g and 136 mAh/g at C/10 and 1C rates.
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Huang, Kai-Pin, i 黃楷斌. "A simple, cheap carbonthermal reduction method to synthesize LiFePO4". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/47089805312846729814.
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碩士國立中央大學
化學工程與材料工程研究所
97
Olivine-structured lithium iron phosphates (LiFePO4) become a promising cathode material because of its low cost, low toxicity, remarkable thermal stability and long operation life. However, it was hard to scale up and reported that this cathode has very low electronic conductivity and diffusion-controlled kinetics. To overcome the problems, various methods have been widely used such as lattice metal doping, surface carbon coating and optimizing the particle size. In order to cut down the synthesis cost, simplify the synthesis technology and enhance the specific capacity of the material, we introduced a carbothermal reduction (CTR) method based on the presence of PEG to synthesize well-carbon-network LiFePO4 by using industrial raw materials and chose ferric oxide as staring material. From our results, a required amount of acetone was added to the starting materials for the ball milling process and the precursor was sintered at 700 ℃ for 8 h to form crystalline phase LiFePO4 with greater electronic conductivity (4.42×10-4 S cm-1). The structure and morphology of the carbon coated LiFePO4 samples have been characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and differential scanning calorimetry (DSC), cyclic voltammetry (CV), and raman spectroscopy, and so on.. Electrochemical measurements show that the LiFePO4/C composite cathode delivered an initial discharge of 150 mAh g-1 at a 0.2 C-rate between 4.0-2.8 V, and almost no capacity loss was observed up to 50 cycles
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Tseng, Yu-An, i 曾宥銨. "Performance of Waterborne Adhesives Used in LiFePO4/C Batteries". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/22222720762580616739.
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碩士萬能科技大學
材料科學與工程研究所在職專班
102
As the focus on environmental protection and energy saving and carbon reduction, that accelerated growth of the electric vehicle,Electric car battery has an important position like a conventional car engines.The battery prices also accounted for nearly one-third to two-thirds of the vehicle's cost, the main material of the battery is divided into four parts, namely, 1. cathode electrode material, 2. Anode material, 3. Electrolyte 4 Separator and other items. In this thesis, the carbon-coated lithium iron phosphate (LiFePO4 / C) as the cathode , graphite as the anode, And environmentally friendly non-toxic water-based adhesive (Aquare Binder) were used in the cathode electrode coating and anode electrode coating as the binder.And to explore the X-Ray diffraction of the sample (XRD) in the test, the powder particle size distribution (PSD), impedance analysis, carbon and sulfur analysis, scan electron microscopy (SEM), elements analysis(EDS), the tap density (Tap Density), massive resistance (volume resistivity), adhesive strength test, and plate bending test, and electrochemical analysis (charge-discharge analysis) and other features.