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Cen, Yinjie. "Si/C Nanocomposites for Li-ion Battery Anode." Digital WPI, 2017. https://digitalcommons.wpi.edu/etd-dissertations/468.
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The demand for high performance Lithium-ion batteries (LIBs) is increasing due to widespread use of portable devices and electric vehicles. Silicon (Si) is one of the most attractive candidate anode materials for the next generation LIBs because of its high theoretical capacity (3,578 mAh/g) and low operation potential (~0.4 V vs Li+/Li). However, the high volume change (>300%) during Lithium ion insertion/extraction leads to poor cycle life. The goal of this work is to improve the electrochemical performance of Si/C composite anode in LIBs. Two strategies have been employed: to explore spatial arrangement in micro-sized Si and to use Si/graphene nanocomposites. A unique branched microsized Si with carbon coating was made and demonstrated promising electrochemical performance with a high active material loading ratio of 2 mg/cm2, large initial discharge capacity of 3,153 mAh/g and good capacity retention of 1,133 mAh/g at the 100th cycle at 1/4C current rate. Exploring the spatial structure of microsized Si with its advantages of low cost, easy dispersion, and immediate compatibility with the prevailing electrode manufacturing technology, may indicate a practical approach for high energy density, large-scale Si anode manufacturing. For Si/Graphene nanocomposites, the impact of particle size, surface treatment and graphene quality were investigated. It was found that the electrochemical performance of Si/Graphene anode was improved by surface treatment and use of graphene with large surface area and high defect density. The 100 nm Si/Graphene nanocomposites presented the initial capacity of 2,737 mAh/g and good cycling performance with a capacity of 1,563 mAh/g after 100 cycles at 1/2C current rate. The findings provided helpful insights for design of different types of graphene nanocomposite anodes.
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Deng, Haokun. "Nanostructured Si and Sn-Based Anodes for Lithium-Ion Batteries." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/612405.
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Lithium-ion batteries (LIBs) are receiving significant attention from both academia and industry as one of the most promising energy storage and conservation devices due to their high energy density and excellent safety. Graphite, the most widely used anode material, with limitations on energy density, can no longer satisfy the requirements proposed by new applications. Therefore, further improvement on the electrochemical performance of anodes has been long pursued, along with the development of new anode materials. Among potential candidates, Si and Sn based anodes are believed to be the most promising. However, the dramatic volume expansion upon Li-intercalation and contraction upon Li de-intercalation cause mechanical instability, and thus cracking of the electrodes. To overcome this issue, many strategies have been explored. Among them the most efficient strategies include introduction of a nanostructure, coupled with a buffering matrix and coating with a protective film. However, although cycling life has been significantly increased using these three strategies, the capacity retention still needs improvement, especially over extensive charge-discharge cycles. In addition, more efforts are still needed to develop new fabrication methods with low costs and high efficiency. To further improve mechanical stability of electrodes, understanding of the failure mechanisms, particularly, the failure mechanisms of Si and Sn nanomaterials is essential. Therefore, some of the key factors including materials fabrication and microstructural changes during cycling are studied in this work. Hollow Si nanospheres have proved to be have a superior electrochemical performance when applied as anode materials. However, most of fabrication methods either involve use of processing methods with low throughput, or expensive temporary templates, which severely prohibits large-scale use of hollow Si spheres. This work designed a new template-free chemical synthesis method with high throughput and simple procedures to fabricate Si hollow spheres with a nanoporous surface. The characterization results showed good crystallinity and a uniform hollow sphere structure. The substructure of pores on the surface provides pathways for electrolyte diffusion and can alleviate the damage by the volume expansion during lithiation. The success of this synthesis method provides valuable inspiration for developing industrial manufacturing method of hollow Si spheres.3D graphene is the most promising matrix that can provide the necessary mechanical support to Sn and Si nanoparticles during lithiation. 2D graphene, however, results in Sn/graphene nanocomposites with a continuous capacity fade during cycling. It is anticipated that this is due to microstructural changes of Sn, however, no studies have been performed to examine the morphology of such cycled anodes. Hence, a new Sn/2D graphene nanocomposite was fabricated via a simple chemical synthesis, in which Sn nanoparticles (20-200 nm) were attached onto the graphene surface. The content of Sn was 10 wt.% and 20 wt.%. These nanopowders were cycled against pure Li-metal and, as in previous studies, a significant capacity decrease occurred during the first several cycles. Transmission and scanning electron microscopy revealed that during long term cycling electrochemical coarsening took place, which resulted in an increased Sn particle size of over 200 nm, which could form clusters that were 1 m. Such clusters result in a poor electrochemical performance since it is difficult for complete lithiation of the Sn to occur. It is hence concluded that the inability of Sn/2D graphene anodes to retain high capacities is due to coarsening that occurs during cycling. In addition to using forms of carbon to buffer the Sn expansion, it has been proposed to alloy Sn with S, which has a low redox potential vs Li⁰/Li⁺. Therefore, another new anode proposed here is that of SnS attached to graphite. The as prepared powders had a flower-like structure of the SnS alloy. Electrochemical cycling and subsequent microstructural analysis showed that after electrochemical cycling this pattern was destroyed and replaced by Sn and SnS nanoparticles. Based on the electron microscopy and XRD analysis, it was concluded that selective leaching of S occurs during lithiation of SnS particles, which results into nano SnS and Sn particles to be distributed throughout the electrolyte or SEI layer, without being able to take part in the electrochemical reactions. This mechanism has not been noted before for SnS anodes and indicates that it may not be possible to retain the initial morphology of SnS alloy during cycling, or the ability of SnS to be active throughout long term cycling. To conclude it should be stated that the goal and novelty of this thesis was (i) the fabrication of new Si, Sn/graphene and SnS/C nanostructures that can be used as anodes in Li-ion batteries and (ii) the documentation of the mechanisms that disrupt the initial structural stability of Sn/2D graphene and SnS/C anodes and result in severe capacity loss during long term cycling (over 100 cycles). These systems are of high interest to the electrochemistry community and battery developers.
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Sun, Xida. "Structured Silicon Macropore as Anode in Lithium Ion Batteries." Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1316470033.
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Trevisan, Henrique. "Structure and functionality of sequence-controlled copolymers in aqueous dispersion and Li-ion anode composites." Electronic Thesis or Diss., Université Paris sciences et lettres, 2022. http://www.theses.fr/2022UPSLS018.
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La sélection de couples de monomères, assurant des rapports de réactivité proches de zéro est une stratégie efficace pour induire une copolymérisation spontanée selon une séquence alternée. La conception de monomères et le réglage des interactions solvant-monomère ouvrent la voie à des copolymères fonctionnels présentant un auto-assemblage moléculaire en relation avec leur structure amphipathique régulière. Dans ce travail, nous analysons les relations existantes entre la structure primaire de copolymères et leur fonctionnalité, dans le domaine colloïdal et dans la formulation de composites pour la partie anodique de batteries Li-ion.Tout d'abord, est rapportée la formation spontanée de nanoparticules par des interactions solvant/non-solvant en utilisant la méthode de basculement de solvant encore appelée ''effet ouzo''. Ainsi, la partie du diagramme ternaire décrivant l'effet ouzo a été construite pour déterminer la fenêtre d'opération via l'auto-assemblage, dans des suspensions aqueuses, de copolymères alternés constitués d'unités vinylphénol et maléimide portant de longs groupes alkyl-pendants (C12H25 ou C18H37). La taille et la structure des nanoparticules se sont avérées être déterminées par au moins trois facteurs : la balance lipo/hydrophilie du copolymère, l'affinité solvant/eau et la diffusivité du solvant qui interviennent pendant le processus de basculement de solvant. Dans l'ensemble, nous présentons ici l'effet ouzo spontané comme une méthode simple pour produire des nanoparticules de copolymères alternés stables dans l'eau sans l'ajout d'agents stabilisants.Ensuite, est abordé dans ce travail le lien entre la structure et fonctionnalité des copolymères et le fonctionnement en tant que liant dans des anodes de Si. Le silicium s'avère prometteur en tant que matériau anodique dans les batteries Li-ion (LIBs) en raison de sa capacité de stockage exceptionnelle par formation d'alliages. Néanmoins, les matériaux d'anode à base de Si ont tendance à s'effondrer rapidement au cyclage et c'est un défi majeur dans lequel la conception de nouveaux polymères pourrait apporter des solutions. Dans ce travail, nous avons examiné les performances en tant que liant de copolymères statistiques ou alternés comportant des motifs phénoliques, l'idée étant que la liaison hydrogène pourrait jouer un rôle. Nous montrons que le greffage de groupes catéchol sur une structure PAA selon un ordre aléatoire est une stratégie très efficace pour améliorer la performance électrochimique des composites anodiques à base de nano-/microparticules de Si. Finalement, des copolymères à séquence contrôlée comportant plus ou moins d'unités vinylphénol ont été expérimentés comme liants d'électrodes de Si. L'analyse du cyclage met en évidence un lien, cette fois-ci négatif, entre la structuration mésoscopique (lié à fonctionnalité du copolymère) et le fonctionnement en tant que liant d'anodes de Si. En effet, la présence d'unités phénoliques induit un auto-assemblage du copolymère sous forme de micelles vermiculaires qui se maintient à l'intérieur du composite d'anode, conduisant à une structure hiérarchique, finalement préjudiciable à la longévité de l'anode et à l'accommodation des changements de volume de SiThe selection of monomer couples, ensuring reactivity ratios close to zero is an effective strategy to induce spontaneous copolymerization in an alternating sequence. The design of monomers and the customisation of solvent-monomer interactions open the way to functional copolymers exhibiting molecular self-assembly in relation to their regular amphipathic structure. In this work, we analyse the existing relationships between the primary structure of copolymers and their functionality, in the colloidal domain and in the formulation of composites for the anode part of Li-ion batteries.First, the spontaneous formation of nanoparticles by solvent/non-solvent interactions is reported using the solvent-shifting method, also called as "ouzo effect". Thus, the part of the ternary diagram describing the ouzo effect was constructed to determine the window of operation via the self-assembly, in aqueous suspensions, of alternating copolymers consisting of vinylphenol and maleimide units bearing long alkyl-pendant groups (C12H25 or C18H37). The size and structure of the nanoparticles were found to be determined by at least three factors: the lipo/hydrophilic balance of the copolymer, the solvent/water affinity, and the solvent diffusivity involved during the solvent-shifting process. Overall, we present here the spontaneous ouzo effect as a simple method to produce stable alternating copolymer nanoparticles in aqueous dispersion without the addition of stabilizing agents.Next, the link between the structure and functionality of the copolymers and their function as a binder in Si anodes is addressed in this work. Silicon enlightens its promise as anode material in Li-ion batteries (LIBs) due to its exceptional storage capacity through alloy formation. Nevertheless, Si-based anode materials tend to collapse rapidly upon cycling, and this is a major challenge in which the design of new polymers could provide solutions. In this work, we have examined the performance as a binder of random or alternating copolymers with phenolic units, the idea being that hydrogen bonding might play a role. We show that grafting catechol groups onto a PAA structure in a random order is an effective strategy to improve the electrochemical performance of Si nano-/micro particle based anode composites. Finally, sequence-controlled copolymers with more or less vinyl phenol units were tested as Si electrode binders. Cycling analysis shows a link, negative this time, between the mesoscopic structuring (linked to the functionality of the copolymer) and the role as Si anode binder. Indeed, the presence of phenolic units induces a self-assembly of the copolymer in the form of vermicular micelles which is maintained inside the anode composite, leading to a hierarchical structure, which is detrimental to the longevity of the anode and to the accommodation of Si volume changes
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Yoon, Dong-hwan [Verfasser]. "Analysis of aging behavior of Si alloy-based anode in lithium-ion batteries / Dong-hwan Yoon." Ulm : Universität Ulm, 2020. http://d-nb.info/1219577723/34.
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Fan, Jui Chin. "The Performance of Structured High-Capacity Si Anodes for Lithium-Ion Batteries." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5467.
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This study sought to improve the performance of Si-based anodes through the use of hierarchically structured electrodes to provide the nanoscale framework needed to accommodate large volume changes while controlling the interfacial area – which affects solid-electrolyte interphase (SEI) formation. To accomplish this, electrodes were fabricated from vertically aligned carbon nanotubes (VACNT) infiltrated with silicon. On the nanoscale, these electrodes allowed us to adjust the surface area, tube diameter, and silicon layer thickness. On the micro-scale, we have the ability to control the electrode thickness and the incorporation of micro-sized features. Treatment of the interfacial area between the electrolyte and the electrode by encapsulating the electrode controls the stabilization and reduction of unstable SEI. Si-VACNT composite electrodes were prepared by first synthesizing VACNTs on Si wafers using photolithography for catalyst patterning, followed by aligned CNT growth. Nano-layers of silicon were then deposited on the aligned carbon nanotubes via LPCVD at 200mTorr and 535°C. A thin copper film was used as the current collector. Electrochemical testing was performed on the electrodes assembled in a CR2025 coin cell with a metallic Li foil as the counter electrode. The impact of the electrode structure on the capacity at various current densities was investigated. Experimental results demonstrated the importance of control over the superficial area between the electrolyte and the electrode on the performance of silicon-based electrodes for next generation lithium ion batteries. In addition, the results show that Si-VACNT height does not limit Li transport for the range of the conditions tested.
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Fan, Jui Chin. "The Impact of Nanostructured Templates and Additives on the Performance of Si Electrodes and Solid Polymer Electrolytes for Advanced Battery Applications." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7568.
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The primary objectives of this research are: (1) use a hierarchical structure to study electrode materials for next-generation lithium-ion batteries (LIBs) and (2) understand the fundamentals and utility of solid polymer electrolytes (SPEs) with the addition of halloysite nanotubes (HNTs) for battery applications. Understanding the fundamental principles of electrode and electrolyte materials allows for the development of high-performance LIBs. The contributions of this dissertation are described below. Encapsulated Si-VACNT Electrodes. Two hurdles prevent Si-based electrodes from mass production. First, bulk Si undergoes volume expansion up to 300%. Second, a solid-electrolyte interphase (SEI) forms between the interface of the electrolyte and electrode, which consumes battery capacity and creates more resistance at the interface. Si volume changes were overcome by depositing silicon on vertically-aligned carbon nanotubes (VACNTs). Encapsulating the entire Si-VACNT electrode surface with carbon was used to mitigate SEI formation. Although SEI formation was reduced by the encapsulation layer, capacity fade was still observed for encapsulated electrodes, indicating that SEI formation was not the primary factor affecting capacity fade. Additionally, the impact of the encapsulation layer on Li transport was examined. Two different transport directions and length scales were relevant””(1) radial transport of Li in/out of each Si-coated nanotube (~40 nm diameter) and (2) Li transport along the length of the nanotubes (~10 µm height). Experimental results indicated that the height of the Si-VACNT electrodes did not limit Li transport, even though that height was orders of magnitude greater than the diameter of the tubes. Simulation and experimental data indicated that time constant for Li diffusion into silicon was slow, even though the diffusion distance was short relative to the tube height. Other factors such as diffusion-induced stress likely had a significant impact on diffusion through the thin silicon layer. Solid Polymer Electrolytes. A thorough understanding of the relationships between physical, transport, and electrochemical properties was studied. HNT addition to polyethylene oxide (PEO) electrolytes not only improved the physical properties, such as reduction of the crystallinity of PEO, but also enhanced transport properties like the salt diffusivity. The processing steps were important for achieving enhanced properties. Moreover, HNTs were found to stabilize the interfacial properties of the SPE films during cycling. Specifically, HNT-containing SPE films were successfully cycled at room temperature, which may have important implications for SPE-based batteries.
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Aslanbas, Özgür Verfasser], Rüdiger-A. [Akademischer Betreuer] [Eichel, Joachim [Akademischer Betreuer] Mayer, and Egbert [Akademischer Betreuer] Figgemeier. "Synthesis and characterization of Al-Si alloys for anode materials of metal-air batteries / Özgür Aslanbas ; Rüdiger-A. Eichel, Joachim Mayer, Egbert Figgemeier." Aachen : Universitätsbibliothek der RWTH Aachen, 2021. http://d-nb.info/1240765541/34.
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Vanpeene, Victor. "Étude par tomographie RX d'anodes à base de silicium pour batteries Li-ion." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI023/document.
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De par sa capacité spécifique théorique dix fois plus élevée que celle du graphite actuellement utilisé comme matériau actif d'anode pour les batteries Li-ion, le silicium peut jouer un rôle important dans l'augmentation de la densité d'énergie de ces systèmes. La réaction d'alliage mise en place lors de sa lithiation se traduit cependant par une forte expansion volumique du silicium (~300 % contre seulement ~10 % pour le graphite), conduisant à la dégradation structurale de l'électrode, affectant notablement sa tenue au cyclage. Comprendre en détail ces phénomènes de dégradation et développer des stratégies pour limiter leur impact sur le fonctionnement de l'électrode présentent un intérêt indéniable pour la communauté scientifique du domaine. L'objectif de ces travaux de thèse était en premier lieu de développer une technique de caractérisation adaptée à l'observation de ces phénomènes de dégradation et d'en tirer les informations nécessaires pour optimiser la formulation des anodes à base de silicium. Dans ce contexte, nous avons utilisé la tomographie aux rayons X qui présente l'avantage d'être une technique analytique non-destructive permettant le suivi in situ et en 3D des variations morphologiques s'opérant au sein de l'électrode lors de son fonctionnement. Cette technique a pu être adaptée à l'étude de cas du silicium en ajustant les volumes d'électrodes analysés, la résolution spatiale et la résolution temporelle aux phénomènes à observer. Des procédures de traitement d'images adéquates ont été appliquées afin d'extraire de ces analyses tomographiques un maximum d'informations qualitatives et quantitatives pertinentes sur leur variation morphologique. De plus, cette technique a pu être couplée à la diffraction des rayons X afin de compléter la compréhension de ces phénomènes. Nous avons ainsi montré que l'utilisation d'un collecteur de courant 3D structurant en papier carbone permet d'atténuer les déformations morphologiques d'une anode de Si et d'augmenter leur réversibilité en comparaison avec un collecteur de courant conventionnel de géométrie plane en cuivre. Nous avons aussi montré que l'utilisation de nanoplaquettes de graphène comme additif conducteur en remplacement du noir de carbone permet de former un réseau conducteur plus à même de supporter les variations volumiques importantes du silicium. Enfin, la tomographie RX a permis d'étudier de façon dynamique et quantitative la fissuration et la délamination d'une électrode de Si déposée sur un collecteur de cuivre. Nous avons ainsi mis en évidence l'impact notable d'un procédé de "maturation" de l'électrode pour minimiser ces phénomènes délétères de fissuration-délamination de l'électrodeBecause of its theoretical specific capacity ten times higher than that of graphite currently used as active anode material for Li-ion batteries, silicon can play an important role in increasing the energy density of these systems. However, the alloying reaction set up during its lithiation results in a high volume expansion of silicon (~300% compared with only ~10% for graphite) leading to the structural degradation of the electrode, which is significantly affecting its cycling behavior. Understanding in detail these phenomena of degradation and developing strategies to limit their impact on the functioning of the electrode are of undeniable interest for the scientific community of the field. The objective of this thesis work was first to develop a characterization technique adapted to the observation of these degradation phenomena and to draw the necessary information to optimize the formulation of silicon-based anodes. In this context, we have used X-ray tomography which has the advantage of being a non-destructive analytical technique allowing in situ and 3D monitoring of the morphological variations occurring within the electrode during its operation. This technique has been adapted to the case study of silicon by adjusting the analyzed electrode volumes, the spatial resolution and the temporal resolution to the phenomena to be observed. Appropriate image processing procedures were applied to extract from these tomographic analyzes as much qualitative and quantitative information as possible on their morphological variation. In addition, this technique could be coupled to X-ray diffraction to complete the understanding of these phenomena. We have shown that the use of a carbon paper structuring 3D current collector makes it possible to attenuate the morphological deformations of an Si anode and to increase their reversibility in comparison with a conventional copper current collector of plane geometry. We have also shown that the use of graphene nanoplatelets as a conductive additive to replace carbon black can form a conductive network more able to withstand the large volume variations of silicon. Finally, the X-ray tomography allowed studying dynamically and quantitatively the cracking and delamination of an Si electrode deposited on a copper collector. We have thus demonstrated the significant impact of a process of "maturation" of the electrode to minimize these deleterious phenomena of cracking-delamination of the electrode
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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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Kaspar, Jan [Verfasser], Ralf [Akademischer Betreuer] Riedel, and Gian Domenico [Akademischer Betreuer] Sorarù. "Carbon-Rich Silicon Oxycarbide (SiOC) and Silicon Oxycarbide/Element (SiOC/X, X= Si, Sn) Nano-Composites as New Anode Materials for Li-Ion Battery Application / Jan Kaspar. Betreuer: Ralf Riedel ; Gian Domenico Soraru." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2014. http://d-nb.info/1110902336/34.
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Brumbarov, Jassen [Verfasser], Julia [Akademischer Betreuer] Kunze-Liebhäuser, Peter [Gutachter] Müller-Buschbaum, and Julia [Gutachter] Kunze-Liebhäuser. "Si on conductive self-organized TiO2 nanotubes – A safe high capacity anode material for Li-ion batteries : Synthesis, physical and electrochemical characterization / Jassen Brumbarov ; Gutachter: Peter Müller-Buschbaum, Julia Kunze-Liebhäuser ; Betreuer: Julia Kunze-Liebhäuser." München : Universitätsbibliothek der TU München, 2021. http://d-nb.info/1232406198/34.
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Kang, Chi Won. "Enhanced 3-Dimensional Carbon Nanotube Based Anodes for Li-ion Battery Applications." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/955.
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A prototype 3-dimensional (3D) anode, based on multiwall carbon nanotubes (MWCNTs), for Li-ion batteries (LIBs), with potential use in Electric Vehicles (EVs) was investigated. The unique 3D design of the anode allowed much higher areal mass density of MWCNTs as active materials, resulting in more amount of Li+ ion intake, compared to that of a conventional 2D counterpart. Furthermore, 3D amorphous Si/MWCNTs hybrid structure offered enhancement in electrochemical response (specific capacity 549 mAhg-1). Also, an anode stack was fabricated to further increase the areal or volumetric mass density of MWCNTs. An areal mass density of the anode stack 34.9 mg/cm2 was attained, which is 1,342% higher than the value for a single layer 2.6 mg/cm2. Furthermore, the binder-assisted and hot-pressed anode stack yielded the average reversible, stable gravimetric and volumetric specific capacities of 213 mAhg-1 and 265 mAh/cm3, respectively (at 0.5C). Moreover, a large-scale patterned novel flexible 3D MWCNTs-graphene-polyethylene terephthalate (PET) anode structure was prepared. It generated a reversible specific capacity of 153 mAhg-1 at 0.17C and cycling stability of 130 mAhg-1 up to 50 cycles at 1.7C.
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Jin, Yanting. "Understanding the solid electrolyte interphase formed on Si anodes in lithium ion batteries." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/288372.
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The main aim of this thesis is to reveal the chemical structures of the solid-liquid interphase in lithium ion batteries by NMR spectroscopy in order to understand the working mechanism of electrolyte additives for achieving stable cycling performance. In the first part, a combination of solution and solid-state NMR techniques, including dynamic nuclear polarization (DNP) are employed to monitor the formation of the solid electrolyte interphase (SEI) on next-generation, high-capacity Si anodes in conventional carbonate electrolytes with and without fluoroethylene carbonate (FEC) additives. A model system of silicon nanowire (SiNW) electrode is used to avoid interference from the polymeric binder. To facilitate characterization via one- and two-dimensional NMR, ^13C-enriched FEC was synthesized and used, ultimately allowing a detailed structural assignment of the organic SEI. FEC is found to first defluorinated to form soluble vinylene carbonate (VC) and vinoxyl species, which react to form both soluble and insoluble branched ethylene-oxide-based polymers. In the second part, the same methodology is applied to study the decomposition products of pure FEC or VC electrolytes containing 1 M LiPF_6. The pure FEC/VC system simplifies the electrolyte solvent formulation and avoids the interaction between different solvent molecules. Polymeric SEIs formed in pure FEC or VC electrolytes consist mainly of cross-linked PEO and aliphatic chain functionalities along with additional carbonate and carboxylate species. The presence of cross-linked PEO-type polymers in FEC and VC correlates with good capacity retention and high Coulombic efficiencies of the SiNWs anode. Using ^29Si DNP NMR, the interfacial region between SEI and the Si surface was probed for the first time with NMR spectroscopy. Organosiloxanes form upon cycling, confirming that some of the organic SEI is covalently bonded to the Si surface. It is suggested that both the polymeric structure of the SEI and the nature of its adhesion to the redox-active materials are important for electrochemical performance. Finally, the soluble decomposition products of EC formed during electrochemical cycling have been thoroughly analyzed by solution NMR and mass spectrometry, in order to explain the capacity-fading of Si anodes in a conventional EC-based electrolyte and address questions that arose when studying the additive-containing electrolytes. The detailed structures for the EC-degradation products are determined: a linear oligomer consist of ethylene oxide and carbonate units is observed as the major degradation product of EC.
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Tian, Yuan. "Fabrication and characterization of active and stable Ti/Si/BDD anodes for electro-oxidation /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?EVNG%202004%20TIAN.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 89-99). Also available in electronic version. Access restricted to campus users.
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MARONI, FABIO. "Synthesis and characterization of advanced materials for Li-ion batteries : 1. Si/RGO nanocomposite anodes. 2. V2O5 gel cathodes." Doctoral thesis, Università degli Studi di Camerino, 2015. http://hdl.handle.net/11581/401727.
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Lithium-ion batteries represent the state-of-the-art of electrochemical energy storage. However, with the advance of microelectronic technology for portable devices and the progressive introduction into the automotive market of Electrical Vehicles (EVs.), a breakthrough in Li-ion materials is needed to overcome known issues related to cost, higher energy densities, safety and cycle life. Moreover, steps forward are also needed from a sustainability point of view, in order to reduce both costs and environmental impact during battery manufacturing. On the anode side, research in next-generation materials, capable of replacing the industry-standard graphite, are now underway. In this PhD thesis, a novel high capacity Silicon/Reduced Graphene Oxide (Si/RGO) nanocomposite has been synthesized, thoroughly characterized and evaluated under an electrochemical point of view. The electrode preparation has been optimized using an alternative binder and eco-friendly solvent like ethanol. The composite shows a good stability and capacity retention over prolonged cycling. On the cathode side, next-generation materials should have higher capacities in order to increase the energy density of the future batteries. In this PhD thesis, Vanadium Pentoxide (V2O5) - has been studied both in its amorphous (aerogel) and crystalline form as next generation Li-ion cathode materials. Also in this case materials were prepared, characterized and electrochemically tested. A green and eco-friendly approach during electrode processing was used also in this case. The data resulting from this PhD thesis were subject of the following publications and proceedings of congresses: - F. Maroni, R. Raccichini, A. Birrozzi, G. Carbonari, R. Tossici, F. Croce, R. Marassi, F. Nobili Graphene/silicon nanocomposite anode with enhanced electrochemical stability for lithium-ion battery applications, J. Power Sources, 2014; Vol. 269; 873 882. doi:10.1016/j.jpowsour.2014.07.064 - A. Moretti, F. Maroni, F. Nobili, S. Passerini, V2O5 electrodes with extended cycling ability and improved rate performance using polyacrylic acid as binder, J. Power Sources, 2014, In Press. doi : 10.1016/j.jpowsour.2014.09.150 - A. Moretti, F. Maroni, I. Osada, F. Nobili, S. Passerini, V2O5 aerogel as a versatile cathode material for lithium and sodium batteries, ChemElectroChem, 2014, In Press. - F. Nobili, F. Maroni, R. Raccichini, R. Tossici, R. Marassi, A Silicon/Graphene Composite Anode for High-Efficiency Lithium Batteries, 17th International Meeting on Lithium Batteries, June 10/14 2014, Cernobbio (CO) Italy, Abstract #361. - F. Nobili, F. Maroni, R. Raccichini, R. Tossici, R. Marassi, Graphene/Silicon nanocomposite anode with enhanced electrochemical stability for Li-ion battery applications, Green Lion European Project Workshop, October 28-29 2014, Ulm, Germany Abstract #20. - Si/RGO nanocomposite development was carried out within the ENEA project ''Ricerca di materiali anodici per batterie litio ione operanti in elettroliti organici convenzionali di pia'¹ elevata energia rispetto a quelle sul mercato'' and reported in the following documents: - R. Marassi, F. Nobili, R. Tossici, M. Marinaro, A. Birrozzi, R. Raccichini, RdS 2012 - A. Birrozzi, F. Maroni, G. Carbonari, R. Tossici, F. Nobili, R. Marassi, RdS 2013
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Dölle, Janis [Verfasser], Robert [Akademischer Betreuer] Schlögl, Martin [Akademischer Betreuer] Lerch, and Christina [Akademischer Betreuer] Roth. "Investigation of Si/C-based anodes for Li-Ion batteries / Janis Dölle. Gutachter: Robert Schlögl ; Martin Lerch ; Christina Roth. Betreuer: Robert Schlögl." Berlin : Technische Universität Berlin, 2014. http://d-nb.info/106738720X/34.
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Desrues, Antoine. "Matériaux composites Si@C nanostructurés pour anodes de batterie Li-ion à haute densité d’énergie. Relations entre structure/morphologie et mécanismes de dégradation." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS279.
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Un des enjeux de la transition énergétique est de disposer de systèmes de stockage denses en énergie, abordables, et conservant une bonne capacité pendant de nombreux cycles, afin d’aider à la décarbonation des transports. A l’anode des systèmes Li-ion, le silicium (Si) est un bon candidat pour le remplacement du graphite commercial grâce à sa capacité 10 fois plus élevée. Les mécanismes de dégradation du Si empêchent le déploiement à grande échelle. L’objectif de ce travail est d’optimiser les caractéristiques des matériaux pour la réalisation d’anodes performantes. Deux voies d’optimisation sont suivies : la réduction de la taille des particules et le dépôt d’une couche de carbone en surface du Si. La technique de synthèse employée est la pyrolyse laser à double étage, une technique de synthèse souple qui permet d’optimiser facilement les conditions de la réaction. Une gamme de tailles de particules comprise entre 29 nm et 107 nm est obtenue et les particules de 53 nm présentent les meilleures performances. Des nanoparticules de morphologie cœur-coquille (Si@C) de 29 nm sont obtenues en une étape par le dépôt d’une coquille de carbone en surface à des quantités maximales de 19 m%. Le carbone permet une meilleure rétention de capacité puisque 81 % de la capacité est conservée au bout de 50 cycles pour Si@C, contre 72 % pour Si. Une étude fondamentale par SIE et XPS a permis d’identifier que la composition chimique plus organique de la couche d’interface de Si@C, comparé à Si, permet la meilleure rétention de capacité observée pour Si@C. Une autre stratégie de stabilisation consiste à créer des alliages SiGe pour tirer parti de la meilleure stabilité du germanium. Plusieurs compositions d’alliages ont été synthétisées par pyrolyse laser. Elles montrent toute la formation d’une structure de type SiGe@Si. Les capacités obtenues sont supérieures à l’état de l’art pour une composition d’alliage proche de Si₀,₅Ge₀,₅Performing energy storage devices need to be developed in the context of Energy transition. Such systems have to maintain high energy density during a large number of cycles, to meet the challenge of clean transportation. Silicon (Si) is a good candidate for Li-ion systems anodes’ with its capacity which is 10 times higher than commercial graphite. However, silicon degradation mechanisms impede wide commercial deployment. The objective of this work is to optimize characteristics of Si to obtain performing anodes. Two strategies are employed to achieve this goal: the size reduction of Si particles and the deposition of a carbon coating on the silicon surface. The synthesis technique in this work is double stage laser pyrolysis which allows the tunable synthesis of nanoparticles. A wide range of nanoparticles, with diameters from 29 nm to 107 nm, is obtained and the best trade-off on performance is obtained for 53 nm particles. Nanoparticles with core@shell morphology (Si@C), with 29 nm diameter are obtained in one-step, the carbon representing 19 % of the total mass. The carbon coating allows a better capacity retention as 81 % of the capacity is conserved for Si@C compared to 72 % of the capacity conserved for Si particles. A fundamental study by EIS and XPS enlightens the role of the more organic chemical composition of the interphase between the solid and the electrolyte for the stabilization of the Si@C particles. Another strategy for stabilization is the design of SiGe nanostructured alloys to take advantage of the germanium stability in anodes. Several alloy compositions have been synthetized by laser pyrolysis. All alloy composition exhibit an original SiGe@Si core-shell structure which may explain the better performance obtained, compared with the state of the art
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Pan, Ke. "A Systematic Methodology for Characterization and Prediction of Performance of Si-based Materials for Li-ion Batteries." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1578038345015173.
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Reddi, Rahul. "In-situ characterization of Li-ion battery electrodes using atomic force microscopy." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524215477787917.
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Wen-YaChung and 鍾玟雅. "Si / C composite as anode material for lithium ion batteries." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/khm225.
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Ku, Chia-Hao, and 古家豪. "Employing Si-doped GaZnO transparent conductive film as anode in OLEDs." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/87903384921770765001.
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碩士元智大學
光電工程學系
105
Since the organic light-emitting diodes (OLEDs) with phosphorescent emitters have high internal quantum efficiency, more and more researchers focused on the development of high-efficiency OLEDs. However, OLED structure is constructed by several thin films which possess different refractive indices. Thus, the light generated in the device will produce reflection, refraction, absorption, optical waveguiding, the re-emission and other optical effects, so that the ratio of the external radiation will be only up to about 25%.Therefore, the surface plasma mode, the waveguide mode and the substrate mode should be decreased to further improve the ratio of the external radiation mode. Herein, we propose a new device structure with a composite transparent electrode, aiming to increase the radiation mode. We develop a new transparent conducting oxide, Si-doped GZO (SGZO), which possess low refractive index and adequate electrical properties. The SGZO film could be fabricated by using RF sputtering. Blue phosphorescent OLEDs employing the SGZO as anode could achieve the maximum efficiency of 22.5% (52.5 lm/W). Furthermore, a SGZO film was used to combine with a MGZO film to construct a composite transparent electrode for OLEDs. The refractive index of MGZO is evaluated to be about 2.0, while the SGZO film has the refractive index of about 1.6. The optical simulation indicated that the out-coupling efficiency of OLEDs equipped with a SGZO/MGZO anode could be enhanced by a 1.5~2.0 fold. By varying the thickness of the composite electrode, the external quantum efficiency of blue-emitting OLEDs could be fine-tuned. The maximum external quantum efficiency of OLEDs was up to 140%, which was much higher than those of devices with single MGZO or SGZO anode.
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Yin, Zhong-Xuan, and 尹忠璿. "High Performance AlGaN/GaN-On-Si Lateral Schottky Barrier Diodes with Dual Anode Recess and Double Anode Field Plate." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/2h84ed.
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碩士國立交通大學
工學院半導體材料與製程設備學程
108
In response to the needs of mankind, communication technology is gradually moving toward the era of 5G, and the emerging materials that are currently considered to meet this demand are mainly silicon carbide and gallium nitride compound materials, and GaN materials are more economical. The gallium nitride material has a faster electron mobility and a higher breakdown electric field than the silicon material, and has a faster switching speed and a higher forward current than the silicon material during voltage conversion, but in aluminum nitride. The production of the schottky diode on AlGaN / GaN will cause a large reverse leakage current, so it is our research goal. In this study, a AlGaN / GaN material was used to fabricate the Schottky diode. We used a second anode etch technique to achieve low reverse leakage current and low forward onset voltage. Low power Inductively-Coupled Plasma (ICP) with chlorine gas for dry etching can accurately control the etching rate, achieve nano level etching depth, and effectively improve component characteristics. Finally, a double-layer anode electric field plate is plated to increase the breakdown voltage and to withstand high voltage components. As a result, a high performance SBD device (Gate Width 1mm, Gate Length 10 µm) with a VT of 0.42V (1 mA/mm), a VF of 1.26 V (100 mA/mm), a leakage current of 12 nA/mm and a breakdown voltage of 1140V (1mA/mm) is successfully manufactured.
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Wei-Ren, Liu. "Preparation and Characterization of Si-based Anode Materials for Lithium-Ion Batteries." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2906200613403700.
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Liu, Wei-Ren, and 劉偉仁. "Preparation and Characterization of Si-based Anode Materials for Lithium-Ion Batteries." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/51569604669114910142.
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博士國立臺灣大學
化學工程學研究所
94
Silicon is a very promising candidate to replace graphite as an anode material in Li-ion batteries because of its high theoretical capacity. However, the main obstacles to commercialization are dramatic volume changes for lithium insertion/extraction and intrinsically poor conductivity of bare silicon, bring mechanical instability and poor rechargeability during cycling. From the view point of stabilizing electrode structure, the effects of Si particle size and the content of conductive additives (CA) on the performance of the Si anode are investigated. It is found that CA content has a profound effect on the cycle life of the electrode, which increases with increasing CA content. Reducing Si particle size, on the other hand, effectively facilitates the charging/discharging kinetics. A cycle life, for instance, exceeding 50 cycles with >96% capacity retention at the charge capacity of 600 mAh/g-Si has been demonstrated by adopting the combination of 30 wt. % of CA and 3-um Si particles. In addition, the choice of binder is also very crucial issue. The cycle-life of the particulate electrode of Si, either with or without carbon coating, has significantly been improved by using a modified elastomeric binder containing Styrene-Butadiene-Rubber (SBR) and Sodium-Carboxyl-Methyl- cellulose (SCMC). Compared with poly-vinylidene-fluoride (PVdF), the (SBR+SCMC) mixture binder shows smaller moduli, a larger maximum elongation, stronger adhesion strength on Cu current collector, and much smaller solvent-absorption in organic carbonate. There are demonstrated cycle lives of > 50 cycles for bare Si at 600 mAh/g or carbon-coated Si at 1000 mAh/g, as contrast to < 8 cycles for PVdF-bound electrode in all cases. The capacity fading and lithiation mechanisms of Si and C-coated Si particulate have also been studied in this study by cycling tests and electrochemical impedance spectroscopy (EIS) analyses, respectively. The capacity versus cycle number plot was found to serve as a useful guide to elucidating two fading modes, including a local mode arising from loss of electronic contact between individual particles and the conductive network of the electrode and a global mode that results from failure of the entire electrode structure. EIS revealed a core-shell lithiation mechanism of Si. C-coating not only exerts remarkable favorite effects against both fading modes, but also serves as a conduit for Li ions to the reaction with Si particles. Porous NiSi/Si particles having a pore size distribution peaked at 200 nm and an intra-particle porosity of nearly 40% have been synthesized by high-energy ball milling of mixture of Ni and Si and subsequent dissolution of un-reacted Ni, and the material has been characterized for its microstructures and electrochemical properties for Li ion battery application. The preset intra-particle voids have been shown to help to accommodate volume expansion arising from alloying of the Si component. As a result, upon charge/discharge cycling, the composite electrode exhibits much reduced thickness expansion, as compared with pure Si electrode, and hence significantly reduced capacity fading rate. In-situ synchrotron XRD further indicates that the NiSi component of the composite is active toward Li alloying, and it undergoes reversible transformation to Ni2Si during charge/discharge cycling. Apart from Si, Si/C, and NiSi/Si composites, the fundamental studies and preliminary electrochemical tests of other active materials, such as Si/ZrO2, Si/TiO2/C, Nano-Si/TiO2/C, SiO, SiO/C, and Nano-SiO/ZrO2/C composite are providing in chapter 6. It is believed that these novel anode composites potentially have opportunities to be promising candidates as anode materials for Li-ion batteries in the future.
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Chen, Ming-Hong, and 陳旻宏. "Preparation of Si/C Composite as Anode Materials for Lithium-Ion Batteries." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/51702951940437482223.
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碩士國立臺灣大學
化學工程學研究所
100
The main purpose of this research is to explore new anode materials based on silicon for lithium-ion battery. Due to the high theoretical capacity of silicon (~3500 mAh/g), it has the potential to replace graphite (372 mAh/g) as anode materials. However, Si has the dramatic volumetric variation (400%) problem during cycling and its low conductivity. This limits the application in commercial. Si/C composite materials are prepared by two different methods to overcome the problems just mentioned. One is carbon coating on Si particle, and the other one is Electrospinning method to produce Si@C nanofiber structure. Carbon-coated Si materials have been prepared by thermal treatment in air atmosphere, and then put the composite to the quartz tube through calcination in inert gas at high temperature to form the homogeneous carbon layer onto the surface of Si particle. Research shows that the calcination process contributes to the significantly proved cycling performance. Si@C nanofiber with high specific surface area and its average diameter after calcination is about 200 nm have been prepared by Electrospinning process. During the cycling tests, it seems the Si@C nanofiber structure electrode is not stable while charging/discharging because of the bad connection of fibers and the severe exposedness of Si particle after calcination.
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Chang, Yung-Wei, and 張永蔚. "Study of C/Si composites as anode materials of lithium-ion batteries." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/23205446458043978257.
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碩士國立臺灣大學
化學工程學研究所
100
Abstract Due to the invention of hybrid electric vehicles and electric vehicles in recent years, the commercialized batteries cannot make effort of loading. So we need lithium –ion batteries beneficial for their high energy density. But lithium-ion batteries with graphite used as anode materials were not efficient for the operations, so a lot of researchers began to investigate the improvement of electrode materials, components of full-scale batteries, etc.., to construct new lithium-ion batteries with higher energy density for the loading. In aspect of research of anode materials, many researchers started to investigate silicon to be a new one by its nature of semiconductor, good specific capacity, and lithium-insertion capacity. However, because the volume expansion occurs during operation, resulting mechanical cracking, further losing electric contact with electrolytes and shrinking the cyclability, they found more ways to resolve this disadvantage. One of them was to coat carbonaceous materials on the surface of silicon to form a carbon/silicon composite. This study was based the effect of different particle-size of silicon (commercial available micron-scale and nano-scale ones), with different processing temperature and holding time to perform the batch pyrolysis of silicon-glucose mixture, followed by analysis of Raman spectrometer to find the coated carbonaceous materials, enhancing mechanical properties of materials, disordered carbons were all detected in various conditions; analysis of X-ray diffractometer to find the existence of crystalline phase, in which the disappearance of specific crystalline phases was observed except for those obtained under 500℃; measurement of thermal differential analyzer to determine the amount of carbonaceous materials, and the amount of carbons of was higher above 50% under the preparation of processing temperature of 300℃ and 400℃; analysis of scanning electron microprobe to observe the morphology, the coating was checked to be well-defined. Then, aqueous SCMC(sodium carboxymethylcellulose) solution was used to bind graphene and pyrolyzed-carbon/silicon composites by mortar. Eventually, assembly half-cell to test the specific capacity of materials with galvanostatic mode by a battery automatic tester for the purpose of investigating the effect of particle size of silicon as anode materials on the performance of Li-ion batteries. By pristine-silicon-based electrodes, nano-Si-based electrode had better performance, its initial discharge capacity was 600mAh/g, charge capacity was 575.24mAh/g; composite-electrodes by the silicon with coating, the one pyrolyzed at 400℃ for 4 hours had better performance, initial discharge capacity was 601.05mAh/g; charge capacity was 420.66mAh/g.
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Jen-Hao, Wang. "Synthesis and Characterization of Si-Cu Composite Anode Materials for Lithium-ion Batteries." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2806200619515100.
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Wang, Jen-Hao, and 王仁壕. "Synthesis and Characterization of Si-Cu Composite Anode Materials for Lithium-ion Batteries." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/04082376176473922573.
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碩士國立臺灣大學
化學工程學研究所
94
The main purpose of this study is to explore new anode materials based on silicon for lithium-ion battery. Although silicon possesses a higher theoretical capacity (~3000 mAh/g) than graphite (372 mAh/g), the dramatic volumetric variation during cycling and intrinsic low conductivity, which resulted in structural instability and poor cyclability, obstruct its commercial application. Si-Cu composite materials are developed by two different methods to overcome the inherent problems of silicon. One is fluidized-bed type reduction (FB-reduction) with the precursor of CuCl powder, and the other is electroless plating in which formaldehyde was served as a reducing agent. Copper has been successfully reduced by both synthesized routes; however, the quality of coating was not satisfactory for FB-reduction and only a “Si + Cu” mixture was formed. Poor electrochemical performance hence has been observed for Si-Cu composites by FB-reduction due to inability to tolerate the volume expansion of silicon, in spite of the enhancement of electrode conductivity. Contrarily, scanning electron microscope (SEM) images show that more conformity and uniformity of coating can be achieved by using electroless plating and the cyclability, as compared with pure Si electrode, has been thereby improved. To enhance mechanical strength of the copper layer, fluidized-bed chemical vapor deposition (FB-CVD) technique has been carried out to coat a further carbon film on Si-Cu composites. Results show that the electrode made by electroless plating and heat treatment, comparing with Si electrode (<8 cycles), can be greatly improved to 60 cycles without fading at the discharge capacity of 1000 mAh/g. A new material copper silicide (Cu3Si) is found for Si-Cu composites after heat treatment in FB-CVD. In-situ X-ray diffraction shows that Cu3Si is a partially inactive material in the reaction of lithium. Moreover, electrochemical performance of single phase Cu3Si electrode has been studied.
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Hsu, Ming-lin, and 許銘麟. "Applications of PAN on Si/C Composite Anode Material for Lithium Ion Battery." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/82833292148163925802.
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碩士國立臺灣大學
化學工程學研究所
102
Lithium ion batteries have been dominating the market for mobile electronic devices for decades. Commercial anode graphite material has advantage of low working voltage, high reversibility and low cost. However, the major disadvantage is its low theoretical capacity of 372 mAh/g. Silicon is the most promising alternative material for its high theoretical specific capacity(~3500mAh/g) and low alloying potential versus Li. However, low electronic conductivity and dramatic volume expansion upon lithiation hinder the commercialization of Si-based anode. In this study, the main objective is to find new Si-based anode materials for lithium-ion battery. According to previous studies, the Si/C composites have overcome some cycle-life problems of silicon. We use solution coating method to coat porous Si/C composites with a thin Polyacrylonitrile (PAN) layer. Capacities and cycle performance were enhanced after PAN-coating. Moreover, FEC was added into EC/ EMC electrolyte to enhance cycle performance. The results showed overall coulombic efficiency and capacity after cycling were increased compared to previous PAN-coated Si/C composites electrode. Finally, the pre-lithiation approach was adopted to enhance the coulombic efficiency in the first cycle. First cycle coulombic efficiency was increased after pre-lithiation approach. This result indicated that this approach is effective and has the potential for practical use.
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Huang, Yao-Sheng, and 黃堯聖. "Preparation and characterization of Si-based composite anode materials for Lithium ion batteries." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/94015381441973464485.
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碩士中原大學
化學工程研究所
102
In this study, we used the pitch as the carbon source and Si/SiC as the active material, made the carbon layer coating on the surface of Si/SiC, to restrain the volume expansion of Si/SiC from outside. And also added the flake graphite before coating process, to buffer volume expansion of Si/SiC from inside. The characterization of the composite were carried out by XRD, FE-SEM, TEM and Raman, and electrochemical analysis were used to investigate the effect of operating parameters. For improvement of the cycle ability, we used the sodium alginate to replace the CMC as a new binder, and added the FEC (Fluoroethylene Carbonate) in our electrolyte, try to improve the cycle ability of Si-base anode material. At first, the effect of the conductive additives (CA) content, 30 wt%, 40 wt% and 50 wt% is checked and it was found that CA content has a profound effect on the cycle life of the electrode, which increased with increasing CA content. Then, we coated diffrenet ratio of carbon content on the surface of Si/SiC. The resulte is, if increased the content of carbon-coating layer on surface of Si/SiC, the volume expansion scale of Si/SiC would be smaller, after 100 cycles the capacity retention still had 32%. Hoping the capacity retention can be improved, we added the flake graphite with Si/SiC, and coated the carbon layer on these two materials' surface. After experiment, 4 (Si / SiC): 3 (flake graphite) is the best ratio that the capacity retention after 100 cycles improved to 60%. In carbonization temperature test, 1000℃ can make the degree of carbonization more completely. On the choice of binder, high porosity construct of sodium alginate's can buffer volume expansion of Si/SiC more effective than CMC-SBR. At last, the FEC addition is added in electrolyte, it was successful that improved the capacity retention to 90% after 160 cycles.
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Li, Yi-jin, and 李奕縉. "Mixture design of Si/PA/C composites as an anode lithium-ion battery." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/46077382234253029689.
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碩士國立臺南大學
綠色能源科技研究所碩士班
99
Lithium-ion (Li-ion) batteries are currently the most widely applied power source in personal electronics. Recently, higher energy density large size batteries have been required in the fields as HEV and EV. The development of alternative anode materials than current graphite/carbon anodes is thus of critical importance. Silicon can be intercalated to a maximum o f 4.4 lithium atoms per silicon atom and the crumbling rate may be slower if the silicon host particles are smaller, it is our idea that the benefits of carbon-silicon composite materials. In this study, we prepare Si/PA/C composite by sol-gel, the material was pyrolyzed at 750◦C and the resulting powder made into an anode. The effects of binders, electrode densities, and conductive carbon on the electrochemical and cycling performance of the Si/PA/C composites were investigated. Finally, ternary organic material consisting of Si, Polymer A (PA), and FMGP (carbon) were prepared using the methodology of mixture design to find the optima formula of Si/PA/C composite by coin cell test. The results were fitted by empirical regression equation and then plotted as the contour diagrams. The data show that the most stable cycle at point, in which materials consisted of Si/PA/C (4.5: 12.5: 83 w/w/w). The Si/PA/C composite exhibited 1st good reversible capacity of 395.4 mAh/g, and its capacity was higher than another experimental grade’s capacity of 359 mAh/g. On the other hand, the Si/PA/C composite was excellent cycle life.
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Chen, Po-Kun, and 陳伯坤. "Carbon-coated Si/Graphite/AlN Composites as Anode Materials for Lithium Ion Batteries." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/32608688483963872725.
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碩士中華技術學院
機電光工程研究所碩士班
95
Abstract Silicon/ graphite/aluminum nitride (AlN) composites with different precursor atomic ratio mixed proportion for anode materials of Li-ion battery. The silicon/graphite/AlN composites with different proportions of weight separately and coating 40 wt.% furan resin after milling in 8 hours are measured with charge and discharge test. The inactive AlN working as a buffer matrix successfully prevents silicon large volume change during charge and discharge electrochemical test. The composites show excellent cycling performance with a reasonable value of the first irreversible capacity to 10%. The capacity is retained about 700mAh/g after 5cycles. Depending on Raman spectroscopy, XRD and SEM analysis, it is found that the silicon/graphite/AlN composites are mixed through milling. The first irreversibility will obviously be reduced. The capacity decade of carbon-coated silicon composites with furan resin will be comparatively steady and the circulation stability will be also improved.
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Yu-Chan, Yen. "Synthesis and Characterization of C-coated Si Composite Anode Materials for Lithium-ion Batteries." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2007200605323100.
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Yen, Yu-Chan, and 嚴佑展. "Synthesis and Characterization of C-coated Si Composite Anode Materials for Lithium-ion Batteries." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/8vewg7.
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碩士國立臺灣大學
化學工程學研究所
94
The main purpose of this research is to explore new anode materials based on silicon for lithium-ion battery. Silicon possesses a high theoretical capacity (~3500 mAh/g) compared to graphite (372 mAh/g), however, the dramatic volumetric variation during cycling and intrinsic low conductivity, which result in structural instability and poor cyclability, block its commercial application. Si-C composite materials are developed by two different methods to overcome the inherent problems of silicon. One is carbon coating on Si powder, and the other is spray drying method to produce porous-structured Si-C secondary particles. Carbon-coated Si materials have been synthesized by a fluidized-bed chemical vapor deposition (FBCVD) method or a thermal pyrolysis process. Research reveals that both the FBCVD process and the pyrolysis reaction give the important contribution to the significantly improved morphology stability. As a ductile matrix, the disordered carbon coated from the CVD process could effectively buffer the volume change of Si particles during charge/discharge cycling. On the other hand, the dense-structured carbon coating obtained from the pyrolysis reaction could reduce the volume expansion of Si particles upon cycling. Porous Si-C particles having a pore size distribution peaks at 300 nm and an intra-particle porosity of nearly 50% have been synthesized by spray drying process. It is expected that the preset intra-particle voids can help accommodate volume expansion arising from alloying of the Si component; nevertheless, the results demonstrate that the porous-structured secondary Si and Si-C particles can not stabilize the electrode architecture during cycling.
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Chao, Sung-Chieh, and 趙崧傑. "Synthesis and Characterization of Porous NiSi-Si Composite Anode Materials for Lithium-Ion Batteries." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/54028936786038767469.
Full textAbstract:
碩士國立臺灣大學
化學工程學研究所
95
The main objective of this research is to explore new materials based on silicon for lithium-ion battery. In the last decade, silicon has attracted much attention because it has the highest specific capacity (~3600 mAh/g) for any of anode materials studied to date. However, Si undergoes a dramatic volume change during cycling and possesses intrinsically poor conductivity, resulting in the mechanical instability and poor cyclability, retard its commercial application. From the view point of stabilizing electrode structure and increasing the conductivity, porous NiSi-Si composite anode material has been synthesized by high-energy ball milling, of mixture of Ni and Si and subsequent dissolution of un-reacted Ni. The preset intra-particle voids have been shown to help to accommodate volume expansion arising form the alloying of Si. Furthermore, Synchrotron XRD indicates that the NiSi component is active toward Li alloying, and Ni2Si is formed during Li alloying. Both preset intra-particles void and presence of Ni2Si help to maintain the integrity of the electrode, resulting in much reduced thickness expansion, as compared with pure Si electrode. In addition, the morphology and composition of SEI layer formation on Si or C-Si anode using LiPF6 in EC/EMC as electrolyte have been carried by means of SEM and XPS analysis. Superficial deposition is vivid even after only one cycle because of the existence of –OH/H2O bounded on SiO2 surface. After coating carbon on Si surface, the formation of Si oxide is reduced.
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Hsu, Hsiang-Yao, and 徐祥耀. "The Macroscopic and Microscopic Simulation of the Carbon-Coated Si Anode Lithium-ion Batteries." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/52046357928711846466.
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碩士國立臺灣大學
化學工程學研究所
101
Lithium-ion batteries have the characteristics of high energy densities, high operate voltage, large output power, and high cycle life. In addition, the low self-discharge rates and the long storage life, making lithium-ion batteries well suited for 3C applications and stationary applications. The mathematical modeling of lithium-ion battery has been developed in this study, based on electrochemistry, combined with thermodynamics, transport phenomena, ohm’s law, and electrochemical kinetics, the model systems was simulated by computer-aided software engineering. The one-dimensional (flow) model was solved by COMSOL 4.3a software, and the Butler–Volmer equation was solved by MATLAB. The results were compared to the P2D model in COMSOL and the experiments which were performed on CR2032 Li-ion cell with various negative electrode materials (KS-6 graphite, Silicon, C-coated Si, and KS-6/Si). Two different approaches have employed to model the insertion of lithium ions into an negative electrode particle: the Fick''s second law and the nonlinear diffusion model considering the vacancy effect. Then, the model system was then scaled up to a cylindrical 18650 lithium cobalt oxide cell. By changing the manufacturing parameters, various effects on the batteries performance would be investigated. Using small particles, increasing the diffusion coefficient of lithium in solid state, and less electrode porosity could increase the discharge capacity. The model involving SEI formation has been developed to simulate the capacity fade of 18650 Li-ion batteries in first few cycles. The largest capacity losses due to solid electrolyte interphase (SEI) growth have been found in the first cycle, and were steady in the next several cycles.
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Hsieh, Yu-Chienms, and 謝雨蒨. "Binder Effects and Architecture Design of Si-based Composite Anode for Li-ion Batteries." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/39505248917101512371.
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碩士中原大學
化學工程研究所
103
The purpose of this research is to explore new anode materials based on silicon for lithium-ion battery. The active material is Si/SiC which is obtained from the waste powder of solar cell. Due to the low cost of anode materials, silicon is a good material in Li-ion batteries because of its high capacity. However, the volume of silicon changes dramatically and the poor conductivity of bare silicon. Moreover, the first cycle of irreversibility resulted from the formation of solid electrolyte interphase (SEI). Firstly, due to the large amount of SiO2 on surface, which would presumably result in the significantly loss of irreversible capacity in the first cycle. Therefore, we discussed the amount of native oxide. we measured the ratio of oxygen on surface of Si/SiC by EDS. The efficiency in the first cycle was slightly improved with 85% coulombic efficiency with the less native oxide sample and 76% with the higher native oxide sample. Secondly, coal tar pitch was prepared from different ratio, and the quantity of coating on Si/SiC would form a layer of amorphous carbon firm. The optimum result appeared on the sample coated by 28 wt.% of coal tar pitch. The value of the retention was 82% and the discharge capacity showed 490 mAh/g after 100 cycles. Although the 28 wt.% carbon-coated could be higher retention, the capacity was too low. So we wanted to design three dimensional polymeric network as a promising binder for silicon through in-situ interconnecting alginate chains by additive divalent cations. As a result, Si/SiC with 3D binder network exhibited high reversible capacity and much prolonged cycle life. It still retained 600 mAh/g after 100cycles. Consequently, the 3D alginate binder was successfully applied for restraining the volume of silicon.
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Lin, Chia Sheng, and 林家聲. "Fabrication of different dimensional Si/C nanocomposites as anode materials for lithium ion battery." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/39270916522819171635.
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碩士國立清華大學
生醫工程與環境科學系
104
Lithium ion batteries (LIBs) play an important role in our daily life. It has been used for cell phone, ipad, laptop and battery electric vehicle. It is one of the richest topics to improve the battery performance in nowadays. Silicon is present in the earth’s crust at 27.7 % of the total and, after oxygen, is the second most abundant element. In addition, Silicon has been widely used as the anode material for lithium ion batteries (LIBs) because of the huge theoretical capacity (~4200 mAh/g) compared with commercial carbon material (~372 mAh/g) and relatively low discharge potential (~0.5V VS. Li/Li+). However, the large volume expansion (~ 400%) after charge-discharge processes hampers the application of silicon to LIBs. In this study, we have synthesized successfully that the combination of Si with different dimensional carbon materials including carbon nanotubes (1D), graphenes (2D), and mesoporous carbons (3D) can minimize the volume expansion, resulting in the enhancement of electrochemical performance of silicon-based electrodes. After 100 cycles, the capacity of 1D, 2D and 3D nanocomposites are ~800 mAh/g, ~1000 mAh/g and ~1300 mAh/g respectively. The coulomb efficiency is above 97% remarkably. It shows our different dimensional carbon materials can be maintained structure after charge-discharge and excellent electrochemical stability. In the future, it can provide the method to improve materials which have the large volume expansion after charge-discharge processes, for example Sn, Sb, Mg and Al.
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WU, YU-HSIEN, and 吳昱賢. "Investigation of Dopamine Modified Si-based Material as Anode Electrodes for Lithium ion Battery." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/k7u58v.
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Li, Kai. "A Study on Nano-Si/Polyaniline/Reduced Graphene Oxide Composite Anode for Lithium-Ion Batteries." Thesis, 2013. http://hdl.handle.net/10012/7495.
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Because of its high theoretical specific capacity (4200mAh/g) and natural abundance (2nd most abundant element on earth), silicon is considered a promising anode candidate for high energy density lithium-ion batteries. However, the dramatic volume changes (up to 400%) that occur during lithiation/delithiation and the relative low electrical conductivity of silicon prevent the implementation of this material. In this work, a nano-silicon/polyaniline/reduced graphene oxide composite was synthesized via a two-step process: in-situ polymerization of polyaniline (PANi) in the presence of nano-silicon followed by combination of the prepared n-Si/PANi binary composite with reduced graphene oxide (RGO), to form a n-Si/PANi/RGO composite. Electron microscopy reveals the unique nano-architecture of the n-Si/PANi/RGO composite: silicon nanoparticles are well dispersed within a PANi matrix, which in turn is anchored to the surface of RGO sheets. The n-Si/PANi/RGO ternary composite delivered an initial capacity of 3259 mAh/g and 83.5% Coulombic efficiency. The new composite displayed better rate performance and capacity recovery than either nano-Si or n-Si/PANi. Structural and morphological studies combined with AC impedance analysis suggest that the n-Si/PANi/RGO composite has higher electrical conductivity than the other two component materials, yielding better performance at high current densities or C rates. The good rate performance, high initial specific capacity and stable Coulombic efficiency of n-Si/PANi/RGO make it a promising anode material for high energy density lithium-ion batteries.
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Li, Ken-Yen, and 黎根延. "Studies on Si/C and SiO/C Composites as Anode Materials in Lithium Ion Battery." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/c59ntg.
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碩士國立中正大學
化學工程研究所
103
Lithium ion battery (LIB) is considered the most promising energy storing device in the next decade. Due to the 3C product development in recent years, the demand for more capacity in lithium ion battery is now higher than ever. New materials in 4A group possess higher capacity than graphite. Among them, Si attracts researcher’s attention due to its high gravimetric capacity (3579mAh/g) when forming Li15Si4. On the other hand, SiO can also react with Li+ and form Li2O, Li4SiO4, Si and provide high capacity. However, Si and SiO suffer from low conductivity and severe volume expansion during lithiation, which induce low coulombic efficiency and fast capacity fading during cycling.To improve the electrochemical performance of Si and SiO, this study prepared mechanical milled Si/C and SiO/C composites as anode materials. Our result shows that the 1st cycle reversible capacity of C-12.5wt%Si composite reaches 640mAh/g, which is approximately 170% of graphite anode, 88% capacity retention after 50 cycles is observed. Besides mechanical mixing, pyrolysis method is also performed for the Si/C composite preparation. The coal tar pitch is used here as carbon precursor. In this part, we discuss the performance and physical properties of pyrolysised Si/C composite. After process optimization, the 1st cycle coulombic efficiency reaches 77%, and remains 90% capacity retention at the 40th cycle.SiO/C anode is also studied in this work. Although the irreversible reduction of SiO lowered the 1st cycle coulombic efficiency(55%), the reversible capacity of SiO reached 956mAh/g at the 1st cycle, 92% retention is also observed after 50 cycles, which shows great potential and excellent electrochemical performance of SiO. To reduce the irreversible capacity, this study put an effort on the reduction of SiO. Three substances had been tried as reducing agent. Result shows that SiO can be reduced into Si and inactive material. The coulombic efficiency has therefore risen to over 75%. It is worth mention that porous silicon particle can be attained by removing inactive material. Compare to all relevant studies, we provide one of the most simple way to prepare porous silicon material for LIB anode.
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Hsieh, Yi Chen, and 謝宜真. "Microwave-Assisted Exfoliated Graphene for High Performance Si/Graphene Anode in Secondary Lithium Ion Battery." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/99903428236906454159.
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碩士國立清華大學
材料科學工程學系
104
Owing to its high specific capacity (3579 mAh/g), silicon has become one of the most promising anode material candidates for use in lithium ion batteries. However, a 400% volume change during alloying is currently the biggest challenge toward their commercial application. The addition of graphene offers one potential method to overcome this problem. Due to its excellent mechanical properties, graphene is well suited to act as a buffer layer between silicon facilitating its large volume expansion. Hence, a facile route toward the optimization of graphene reduction is required. In this work, we demonstrate two different approaches leading to more efficient and low cost processes in order to exfoliate and reduce graphene oxide simultaneously within a few minutes. The difference between the two methods is the starting materials. First, the proposed method, so-called “dry exfoliation method” utilizes silicon carbide as an efficient microwave susceptor heat source. The second method, called “wet exfoliation method” uses graphene oxide solution with the addition of a reducing agent. In both cases, under microwave radiation, graphene oxide undergoes a rapid heating and reduction to graphene. To characterize our materials, we utilize Fourier transform infrared spectroscopy (FTIR) and X-Ray photoelectron spectroscopy (XPS), the loss of C=O peaks and OH peaks confirm the reduction of graphene oxide after treatment. Scanning Electron Spectroscopy (SEM) and Transmission Electron Microscopy (TEM) are used to morphologically characterize the material we synthesized. The cell performances of two different method of reducing graphene oxide are compared, showing capacity values of 1200mAh/g after 150 cycles for r-GO prepared from wet exfoliation method. Furthermore, by using the wet exfoliation method, additional precursors such as copper nanowires can be easily combined into the solution for further material enhancement. We believe this work presents a highly promising technique toward the low-cost production of reduced graphene oxide suitable for future Si based Li-ion battery applications.
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Chia-ChunWu and 伍家均. "Investigation of Si-based Nanocomposite Anode Materials Utilizing Electroless Nickel Plating for Lithium-ion Batteries." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/qk53au.
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YU, SZU-MIN, and 尤斯民. "Enhanced Capacity of Si Anode for Li-Ion Batteries by Using Self-healing Polymer Binder." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/v4jtac.
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碩士明志科技大學
化學工程系碩士班
104
The Lithium battery embraces a boom in the world, and the current estimate shows 53.7 billion dollars in 2020. The commercial Lithium battery has problem about low capacity so the Lithium battery of high capacity will be research in the future. However, most of research will focus promoting the performance of cathode. Although the capacity of lithium ion battery has been enhanced, the theory capacity make consequent limit. The theory capacity of Silicon (4200mAh/g) is not only higher than traditional graphite electrodes (372mAh/g) but also the best anode for developing new generation Lithium ion battery. However, using silicon anode for Lithium ion battery leads expand in charge-discharge and caused by electrode cracks. In this study, biology silicon material: rice husk not only have nano-structure but also have porosity when using magnesiothermic reduction with salt, and it’s efficient to reduce expand when charge-discharge in Lithium ion battery. Further, self healing polymer (SHP) will be design in this research to avoid electrode cracks and damage. We designed the SHP have three function to healed spontaneously when charge-discharge in Lithium ion battery. One is hydrogen bond that can make binder combine again when charge-discharge of battery caused by damage, another is amorphous structure that make sure no crystallization when SHP binder is healing, and the other is low glass transition temperature (Tg) function that means molecular of SHP binder will rearrange and it will be healed when low temperature. Solving this problem to provide Lithium ion battery of high capacity in the future.
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Jhan-Yi, You, and 游展亦. "High Performance AlGaN/GaN-On-Si Lateral Schottky Barrier Diodes with Two-Step Gated Anode." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/jj75rh.
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碩士國立交通大學
光電系統研究所
107
With the coming of the AIot and the increasing demand of transistors worldwide, it is a global goal to make energy consumption in transistors more efficient. For future power electronic components, we require not only higher efficiency and lower cost, but we also need them to have higher current density and higher breakdown voltage. Therefore, wide-bandgap semiconductor materials, such as SiC and GaN, may appear to be promising candidates for next-generation power electronic devices. GaN semiconductor materials, compared to Si, has higher electron mobility and higher breakdown electric field. Thus, with the same bias, GaN-based devices have higher forward current and higher switching speed and could then enhance the transformation efficiency of power converters. However, GaN-based Schottky barrier diodes (SBD), commonly used in power converters, still face leakage issues, which may strongly deteriorate the device performance. In this work, we demonstrated an AlGaN/GaN Schottky barrier diode with a two-step gated anode technology, which not only could suppress the leakage current and could also decrease the turn-on voltage (VT) and the forward voltage (VF). In this experiment, the CF4 plasma etching technology is used to replace the conventional Cl-based plasma etching technology, which has extraordinary etching performance with precise nanoscale etching and could optimize the surface roughness to improve device performances. Furthermore, we discovered that the removal of fluorine ions could be obtained by rinsing in a 36% NH4OH solution after O2 plasma oxidation. As a result, a high performance TSGA-SBD device (Total Width 100 um, Length 10 um) with a VT of 0.55V (1 mA/mm), a VF of 1.68 V (100 mA/mm), a leakage current of 48 nA/mm and a breakdown voltage of 993V (1mA/mm) is successfully manufactured.
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Lai, Chien Ming, and 賴建銘. "Bilayer Prelithiated Ge/Cu and Si/Cu Nanowire Fabric as an Anode for Lithium Ion Capacitors." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/zj73x8.
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碩士國立清華大學
化學工程學系
104
At present, due to the development of portable device and electric vehicles, high energy density isn’t the only purpose required. Possessing high power density is another issue which needs to be considered. An electrical device containing both high energy density and high power density will be the most wanted result. As a result, a lithium ion capacitor has been designed by using pre-lithiated germanium/copper and silicon/copper nanowire fabric for negative electrodes with activated carbon for positive electrodes. For germanium, the performance is 200 F g-1 at 0.1 A g-1. And at high current density of 100 A g-1, the capacitance can still hold about 50 F g-1. The LIC have 108 W kg-1, when the energy density is 180 W h kg-1. While low energy density, the LIC would have ultrahigh power density of 110kW kg-1. For silicon, the performance of this LIC at 0.1 g-1 is 220 F g-1, which is approximated twice of capacitance of AC in EDLCs. Even at high current density of 50 A g-1, the capacitance can still hold about 80 F g-1. At a low power density of 170 W kg-1, the energy density is as high as 208 W h kg-1. The power density increases to 75 kW kg-1, which is much higher than most results in lithium ion capacitors, while the energy density still remains at 43 W h kg-1. As a result, we believe that this device can be used in numerous applications such as electrical vehicles (EVs) and hybrid electrical vehicles (HEVs).
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Yueh-TingShih and 施岳廷. "The Electrochemical Properties and Structural Characteristics of Si-xAl Thin Film Anode at Room Temperature and 55℃." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/27689346305049955406.
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碩士國立成功大學
材料科學及工程學系碩博士班
100
In this study, Al was added into Si matrix as the buffer (Si-8Al, Si-23Al, Si-43Al) by RF magnetron sputtering to prevent the dramatic volumetric expansion of pure Si thin film anode during lithiation and delithiation. The electrochemical properties and structural characteristics of Si-xAl films at room temperature and high temperature (55℃) were investigated. As the addition content of Al in Si matrix increase, lithium ions react with Al only instead of both Al and Si. At 55℃, the higher lithiation and delithiation quantity accompanied a dramatic volumetric expansion which increased the capacity but degraded the stability, besides the Si-23Al thin film was occurred crystallization during charge-discharge. According to the EIS results, the resistances against electrochemical reactions of Si-8Al and Si-23Al are controlled by diffusion of lithium ions in the anode materials at high temperature while charge transfer process at room temperature.
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Fang, Man-Jyun, and 房蔓君. "Hydrothermal syntheses of highly porous anode materials for lithium battery1. TiO2—reduced graphene oxide；2. Si—TiO2 nanowire." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/34604726625771559867.
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碩士國立中興大學
化學系所
105
TiO2 related nanomaterials are considered as promising candidate materials rather than traditional graphite materials for lithium-ion battery anodes. Nevertheless, the intrinsically poor electrical conductivity and low theoretical specific capacity of TiO2 would lead to severely limit its commercial utility. Herein, we report the synthesis of TiO2-reduced graphene oxide composite (termed as T/PrGO) via hydrothermal route. T/PrGO shows a remarkable capacity of 150 mAhg-1 after 500 cycles at a charge rate of 1 C (168 mA g-1) with a high cyclability of 88% because of the enhanced electrical conductivity by reduced graphene oxide. The morphological and structural characterizations were investigated by FE-SEM、FIB、EDS、XRD、Raman、FTIR and WBCS3000 cyclic system.
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Liao, Cheng-Hung, and 廖晟宏. "Single Ion Conducting Block Copolymer for Protective Coating of Graphite and Si@G Anode of Lithium Ion Batteries." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/y7uvzq.
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碩士國立臺灣大學
材料科學與工程學研究所
107
This work employed lithium sulfonate (SO3-Li) tethered poly(styrene-block-(ethylene-ran-butylene)-block-styrene) (SSEBS), obtained from sulfonation of commercial available triblock copolymer SEBS, to serve as the protective coating on the active graphite and active Si@G (silicon on graphite) of the anode in a lithium ion battery (LIB). The protective coating should prevent direct contact of liquid electrolyte with the graphite and Si@G, thus to avoid the negative effects of the liquid electrolyte such as exfoliation of graphite and undesired SEI formation, and therefore improve the long term stability of the LIB. In SSEBS, the SO3-Li groups are grafting onto polystyrene to allow the sulfonated polystyrene domains having lithium ion conducting capability of lithium ion, while the poly(ethylene-ran-butylene) segment provide the ductility and flexibility of the coating layer to accommodate the volume change of graphite and Si@G during charging and discharging cycles. Moreover, the π-π interaction between the aromatic ring of PS and the graphite surface should provide strong adhesion of SSEBS to the graphite. In this work, we systematically varied the amount of SSEBS on the graphite/Si@G to optimize the battery performance. It is demonstrated that the protective coating could effectively improve the electrochemical stability of the anode without sacrificing the battery performance.