Dissertations / Theses on the topic 'Lithium film'

Thesis (Ph.D.)--Tufts University, 1996.
Adviser: Ronald B. Goldner. Submitted to the Dept. of Electrical Engineering. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.
Includes bibliographical references (p. 147-154).
Electrochemical experiments were performed to investigate the processing-property-performance relations of thin film vanadium pentoxide cathodes used in lithium batteries. Variations in microstructures were achieved via sputtering and anneal treatments, resulting in films with different morphologies, grain size distributions, and orientations. Key findings included (1) grain size distributions largely did not affect the current rate performance of the cathodes. Rather, the film orientation and the ability to undergo rapid phase transformation were more vital to improving performance; (2) interfacial resistance and ohmic polarization were also dominant at the high current rates used (> 600 [mu]A/cm²) in addition to solid diffusion; and (3) optimization of thin film batteries requires that film thickness be < 500 nm to avoid diminishing returns in power and energy densities. Kinetic parameters including the transfer coefficient ([alpha] = 0.90± 0.05) and standard rate constant (k⁰ [approx.] 2 x 10⁻⁶ cm/s) for vanadium pentoxide films were quantified using slow scan DC cyclic voltammetry and AC cyclic voltammetry. The reaction rate was found to be potentially limiting at moderate to high current rates (> 200 [mu]A/cm²).
(cont.) An analysis of the wide variation in current-rate performance for different V₂0₅ architectures (including composite, nanofiber, and thin film) shows a convergence in results when the area of active material has been factored into the metric. This convergence suggests that either the reaction rate or interfacial resistance is limiting in V₂0₅ as opposed to diffusion.
by Simon C. Mui.
Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2007.
Includes bibliographical references (leaves 37-39).
I apply the theory of polar and apolar intermolecular interactions to predict the behavior of combinations of common battery materials, specifically the cathode substrate lithium cobalt oxide (LCO) and the polymer separator poly(ethylene oxide). These predictions were first tested qualitatively using hexane and PTFE, which have well-established surface energies, and then by measuring the contact angles of PEO on LCO in hexane and hexadecane, chosen for their immiscibility in PEO. For better comparison, these experiments were repeated using water instead of PEO, for a total of four systems tested. This data allowed an estimate for the experimental surface energy components of LCO to be derived, resulting in 18.3 ± 1 mJ/m2 for [gamma]LW, 0.22 ± 0.02 mJ/m2 for [gamma]+, and 5.8 ± 1.6 mJ/m2 for [gamma]-, compared to the previously reported values of 40.8 mJ/m2 for [gamma]LW, 0.0008 mJ/m2 for [gamma]+, and 0.21 mJ/m2 for [gamma]-. This variation is probably due to a variety of factors, including instrumental uncertainty in the contact angle measurement, a difference in contact angle measurement procedure, and inevitable contamination by water and other materials. Using this new data, self-assembling electrolyte-cathode systems are predicted, like LCO-polyacrylonitrile-chloroform.
by Christalee Bieber.
S.B.

>Magister Scientiae - MSc
Architecturally enhanced electrode materials for lithium ion batteries (LIB) with permeable morphologies have received broad research interests over the past years for their promising properties. However, literature based on modified porous nanoparticles of lithium manganese phosphate (LiMnPO₄) is meagre. The goal of this project is to explore lithium manganese phosphate (LiMnPO₄) nanoparticles and enhance its energy and power density through surface treatment with transition metal nanoparticles. Nanostructured materials offer advantages of a large surface to volume ratio, efficient electron conducting pathways and facile strain relaxation. The material can store lithium ions but have large structure change and volume expansion during charge/discharge processes, which can cause mechanical failure. LiMnPO₄ is a promising, low cost and high energy density (700 Wh/kg) cathode material with high theoretical capacity and high operating voltage of 4.1 V vs. Ag/AgCl which falls within the electrochemical stability window of conventional electrolyte solutions. LiMnPO₄ has safety features due to the presence of a strong P–O covalent bond. The LiMnPO₄ nanoparticles were synthesized via a sol-gel method followed by coating with gold nanoparticles to enhance conductivity. A magnesium oxide (MgO) nanowire was then coated onto the LiMnPO₄/Au, in order to form a support for gold nanoparticles which will then form a thin film on top of LiMnPO₄ nanoparticles crystals. The formed products will be LiMnPO₄/Mg-Au composite. MgO has good electrical and thermal conductivity with improved corrosion resistance. Thus the electronic and optical properties of MgO nanowires were sufficient for the increase in the lithium ion diffusion. The pristine LiMnPO₄ and LiMnPO₄/Mg-Au composite were examined using a combination of spectroscopic and microscopic techniques along with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Microscopic results revealed that the LiMnPO₄/Mg-Au composite contains well crystallized particles and regular morphological structures with narrow size distributions. The composite cathode exhibits better reversibility and kinetics than the pristine LiMnPO₄ due to the presence of the conductive additives in the LiMnPO₄/Mg-Au composite. This is demonstrated in the values of the diffusion coefficient (D) and the values of charge and discharge capacities determined through cyclic voltammetry. For the composite cathode, D= 2.0 x 10⁻⁹ cm²/s while for pristine LiMnPO₄ D = 4.81 x 10⁻¹⁰ cm2/s. The charge capacity and the discharge capacity for LiMnPO₄/Mg-Au composite were 259.9 mAh/g and 157.6 mAh/g, respectively, at 10 mV/s. The corresponding values for pristine LiMnPO₄ were 115 mAh/g and 44.75 mAh/g, respectively. A similar trend was observed in the results obtained from EIS measurements. These results indicate that LiMnPO₄/Mg-Au composite has better conductivity and will facilitate faster electron transfer and therefore better electrochemical performance than pristine LiMnPO₄. The composite cathode material (LiMnPO₄/Mg-Au) with improved electronic conductivity holds great promise for enhancing electrochemical performances, discharge capacity, cycle performance and the suppression of the reductive decomposition of the electrolyte solution on the LiMnPO₄ surface. This study proposes an easy to scale-up and cost-effective technique for producing novel high-performance nanostructured LiMnPO₄ nanopowder cathode material.

Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Kohl, Paul; Committee Member: Fuller, Tom; Committee Member: Gray, Gary; Committee Member: Liu, Meilin; Committee Member: Meredith, Carson; Committee Member: Rincon-Mora, Gabriel.

Ce travail présente l'étude expérimentale du transfert thermique et de l'hydraulique de films ruisselants de solution aqueuse de LiBr sur une paroi verticale garnie de promoteurs de turbulence ou sur une paroi lisse spiralée à faible pente. Les parois sont en graphite à cause de la corrosion. Le régime hydraulique est laminaire, les régimes thermiques sont l'échauffement et l'évaporation. Pour les deux géométries, les films ruissellent avec des sections d'épaisseur non-uniformes, mais stables et constantes le long de l'écoulement. Ceci est du à l'effet Marangoni pour l'écoulement rectiligne et à la force centrifuge dans l'écoulement spirale. Des modélisations simples permettent de retrouver de manière qualitative le comportement expérimental atypique de ces films. Une modélisation globale est proposée pour permettre un classement des différents types d'évaporateur à film ruisselant sur des critères de puissance thermique, taux d'évaporation et encombrement.

La lumière est incroyable polyvalente pour mesurer toutes sortes de grandeurs physiques : température, champ électrique, déplacement et déformation, etc. Les capteurs photoniques sont des candidats prometteurs pour les développements de nouvelles générations de capteurs en raison de leurs vertus de sensibilité élevée, une grande gamme dynamique, etc. Les capteurs intégrés et ceux placés en bout de fibre sur une couche mince de niobate de lithium seront ici étudiés en explorant l’électro-optique ainsi que les pyro-électronique afin de concevoir des capteurs de champs et de capteurs de température
Light is incredibly versatile for measuring all kinds of physical quantities :temperature, electric field (E-field), displacement and strain etc. Photonic sensors are promising candidates for the new generation of sensors developments due to their virtues of high sensitivity, large dynamic range and compact size etc. Integrated and on-fiber end photonic sensors on thin film lithium niobate (TFLN) exploring the electro-optic (EO) and pyro-electric effects are studied in this thesis in order to design E-field sensors and temperature sensors (T-sensors). These studies aim to develop sensors with high sensitivity and compact size. To achieve that aim, sensors that are made of photonic crystals (PhC) cavities are studied by sensing the measurand through the resonance wavelength interrogation method. In integrated sensor studies, intensive numerical calculations by PWE method, mode solving technique and FDTD methods are carried out for the design of high light confinement waveguiding structures on TFLN and suitable PhC configurations. Four types of waveguide (WG) structures (ridge WG, strip loaded WG, slot WG and double slot WG) are studied with a large range of geometrical parameters. Among them, slot WG yields the highest confinement factor while strip loaded WG is an easier option for realizations. Bragg grating is designed in slot WG with an ultra compact size (about 0.5µm×0.7µm ×6µm) and is employed to design PhC cavity. A moderate resonance Q of about 300 in F-P like cavity where the mirrors are made of PhC is achieved with ER of about 70% of the transmission. Theoretical minimum E-field sensitivity of this slot Bragg grating structure can be as low as 200 µV/m. On the other hand, Si3N4 strip loaded WG is designed with 2D PhC structure and a low resonance Q of about 100 is achieved. Fabrications of nano-metrical WG such as ridge WG Si3N4 strip loaded are demonstrated. However, the realization of nanometric components on LN presents a big challenge.In the on-fiber end sensor studies, guided resonance, oftentimes referred to as Fano resonance due to its asymmetric lineshape, is studied with different PhC lattice types. A Suzuki phase lattice (SPL) PhC presenting a Fano resonance at the vicinity of 1500 nm has been studied and demonstrated as temperature sensor with sensitivity of 0.77 nm/oC with a size of only 25 µm × 24 µm. In addition, guided resonances on rectangular lattice PhC have been systematically studied through band diagram calculations, 2D-FDTD and 3D- FDTD simulations

Le phenomene de la passivation de l'electrode carbone-lithium utilisee comme pole negatif dans la batterie lithium-ion est d'une importance cruciale dans les caracteristiques du fonctionnement de cette electrode. Il en fixe la capacite reversible (ou utile), la duree de vie et le taux d'autodecharge. Ce travail est une contribution a la comprehension des processus chimiques et electrochimiques survenant a la surface de l'electrode au cours de l'echange du lithium avec une solution electrolytique a base d'un ou plusieurs solvant(s) organique(s) et d'un sel de lithium et conduisant a la formation d'un film de passivation. Apres une presentation bibliographique qui situe l'etude dans son contexte national et international, le travail experimental s'adresse dans un premier temps au role des parametres qui influent sur le processus de passivation tels que la nature de l'anion du sel de lithium et celle du materiau carbone ainsi que la composition de l'electrolyte. La caracterisation de ce film obtenu par des methodes chimiques ou electrochimiques utilise une large gamme de techniques : drx, meb, met, microscopie a champ proche (afm), ir-tf, rmn, esca, atg et dsc. Les techniques electrochimiques sont aussi variees : chronoamperometrie, chronopotentiometrie, impedance complexe et voltamperometrie cyclique. Les resultats obtenus sont pour la plupart originaux. Ainsi, les analyses de la composition chimique du film par esca et par ir-tf sont non seulement completes et nouvelles mais mettent en evidence pour la premiere fois le caractere polymere du film. Ce resultat devrait avoir des repercutions importantes sur l'elaboration ex situ du film pour une etude plus approfondie. L'observation du film forme sur un graphite hautement oriente par afm a permis d'obtenir les images les plus precises et les plus claires jamais publiees. L'etude electrochimique est completee par une synthese chimique du film par une methode originale. L'utilisation de ce film comme electrolyte de type plastifie a ete demontree.

The work within this thesis focuses on the study of alloy formation using an active liquid metal electrode for fundamental analysis and for the extraction and separation of the lanthanides and actinides in a pyroprocessing system. The electrochemical work herein is performed in a molten salt of lithium chloride and potassium chloride at its eutectic point (LKE). This salt is a likely candidate for pyroprocessing due to its relatively low melting point and resistance to degradation on exposure to high levels of radiation. The active electrode material under examination is bismuth due to its propensity to alloy with other elements, its relatively low melting point, high density and non-toxicity. The alloying processes studied are those of bismuth-lithium and bismuth-cerium. Lithium is the limiting reduction reaction defining the negative solvent limit in LKE. As a result, understanding the processes that would occur if the electrode were to be pushed to such negative potentials is of significant importance. Cerium is a commonly-used surrogate for plutonium, which is an element of relatively high concentration in waste nuclear fuel and is of significant interest to the nuclear international community in waste fuel recycling. This work examines the alloying processes in terms of which intermetallic compounds are formed and by what mechanisms. This is achieved through the use of co-deposition on a macro tungsten rod, employing a number of electrochemical techniques to extract pertinent information. Lithium electrodeposition and alloying with bismuth (at the negative solvent limit) was found to form BiLim alloy with increasing m at more reducing potentials, followed by the deposition of near pure lithium. Mixing of these two then gave rise to specific bismuth-lithium alloys and the apparent ejection of a lithium metal fog into the molten salt, which resulted in the chemical reduction of Bi3+ and the loss of the bismuth electrodeposition current. When electrodepositing cerium on, and alloying with, bismuth, the formation of intermetallic compounds is governed by potential with a maximum BiCem stoichiometry of m = 1 with equimolar Bi3+ and Ce3+. However, at concentrations of cerium greater than that of bismuth, alloys much richer in cerium were also deposited at more negative potentials. There is evidence that deposited cerium may also escape into solution and chemically react with Bi3+. In-house microelectrodes are also developed and used for this purpose, both through co-deposition and direct alloy formation on a liquid bismuth thin-film microelectrode. This work demonstrates that these devices provide a richness of information due to their highly beneficial microelectrode properties. A means of controllably depositing bismuth from an aqueous plating bath, without dendrite formation, on both platinum and tungsten microelectrodes was devised. This was followed by electrodeposition of bismuth films on these devices in LKE. Platinum was found to be an active electrode material, alloying with bismuth, while tungsten remained inert. Nonetheless, both electrode types produced characteristic microelectrode behaviour, which was successfully used to determine the diffusion coefficient of bismuth in LKE. A comparison of bismuth-cerium and cerium alloying on a thin film liquid bismuth microelectrode found that the latter indicated the formation of BiCe2 where only BiCe had been seen previously during co-deposition in an equivalent salt. This is thought to be due to the thin film liquid bismuth microelectrode configuration with enhanced Ce3+ mass transport. This response was also used to calculate the diffusion coefficient of cerium inside the bismuth film, which was found to be slightly slower than for Ce3+ in LKE.

Les principales évolutions requises pour répondre aux besoins de la microélectronique visent à intégrer une micro-source d’énergie susceptible de fonctionner à plus bas potentiel que les systèmes actuels. Ainsi, en vue de répondre à cette demande, ce travail de recherche s’est focalisé sur l’étude, principalement par spectroscopie photoélectronique à rayonnement X (XPS), de deux matériaux d’électrode positive fonctionnant à 3 V vs Li+/Li : le spinelle LiMn2O4 et le Nasicon Fe2(MoO4)3. Le bismuth, matériau potentiel d’électrode négative susceptible de remplacer le lithium métallique et de subir le procédé de soudure classiquement utilisé en microélectronique (le solder reflow), est également étudié dans le cadre de cette thèse. Avant de caractériser ces matériaux en systèmes tout-solide, la première étape consiste à en étudier les comportements électrochimiques en électrolytes liquides. A cet effet, des couches minces d’une épaisseur d’environ 500 nm sont préparées par pulvérisation cathodique après une étape d’optimisation des paramètres de dépôt (puissance, pression partielle et totale dans l’enceinte de dépôt, température de recuit, …), puis caractérisées sur les plans structural (DRX), morphologique (SEM) et chimique (XPS, RBS, ICP). L’analyse des échantillons par XPS en fin de décharge et de charge a permis de mieux comprendre et d’expliquer les réactions électrochimiques se produisant au sein des matériaux et aux interfaces électrode/électrolyte dans les batteries au lithium. Une étude comparative avec un cyclage face au sodium a également été menée dans le cas du molybdate de fer et du bismuth, ce qui a permis d’identifier des comportements spécifiques lors de l’insertion/désinsertion des deux alcalins. L’homogénéité de la lithiation/sodation des couches minces a également été étudiée à partir de différentes analyses XPS menées après un procédé de décapage permettant de s’affranchir de la couche de passivation formée à l’interface électrode/électrolyte.Cette étude contribue à une meilleure connaissance des matériaux d’électrodes en cyclage pour micro-batteries au lithium et présente des perspectives très intéressantes d’intégration dans des dispositifs « tout solide »
The main evolutions required for microelectronic applications aim to integrate an energy microsource operating at lower potential than current systems. Thus, in order to meet this demand, this research work has been focused on the study, mainly by X-ray photoelectron spectroscopy (XPS), of two positive electrode materials operating at 3 V vs Li+/Li: the spinel-type material LiMn2O4 and the Nasicon-type one Fe2(MoO4)3. The bismuth, a potential negative electrode material likely to replace the metallic lithium and to undergo the soldering process conventionally used in microelectronics (the solder reflow), has also been studied in this work. Before studying these materials in all-solid-state systems, the first step consists in investigating their electrochemical behaviors in liquid electrolytes. For this purpose, 500 nm-thick thin films are prepared by magnetron sputtering after a step of deposition parameters optimization (power, partial and total pressures in the sputtering chamber, annealing temperature, etc.). Physicochemical proprieties of the deposited thin films are then investigated by XRD, SEM, XPS, RBS and ICP analyses. The analyses of the electrodes by XPS at the end of discharge and charge has allowed better understanding of the electrochemical reactions occurring within the electrode materials and at the electrode/electrolyte interfaces in lithium cells. A comparative study with cycling against sodium has also been carried out in the case of iron molybdate and bismuth materials. This has allowed identifying specific behaviors of the thin films during the insertion/extraction of the two alkalis. The homogeneity of the thin films lithiation/sodiation has also been studied from various XPS analyses realized after etching process which allows eliminating the passivation layer formed at the electrode/electrolyte interface.This study contributes to a better knowledge of three potential electrode materials candidates for lithium micro-batteries and presents very interesting perspectives of materials integration in all solid state systems

Les machines à absorption LiBr/H2O, appliquées aux systèmes de rafraîchissement par compression chimique présentent des avantages et des inconvénients à l'heure de leur intégration dans des bâtiments de basse consommation. Grandes tailles et coûts de mise en œuvre élevés les rendent peu attractives. Le développement de modules évapo-absorbeur et desorb-condenseur compacts et multifonctionnels, utilisant des échangeurs à film ruisselants couplés peuvent être une solution pour réduire les coûts de mise en œuvre, et augmenter la compacité et le rendement global du processus d'absorption. L'étude se centre autour de l'absorption de la vapeur d'eau à basse pression au sein d'un film de bromure de lithium qui ruisselle sur des échangeurs à plaques verticales. Les objectifs de la thèse sont le développement d'un modèle théorique simple décrivant le transfert de chaleur et de masse et sa validation à l'aide d'expériences de référence. Le modèle analytique est construit à l'aide des méthodes intégrales mettant en ouvre un écoulement laminaire établit à l'entrée de l'absorbeur et des conditions de saturation à l'interface Nous avons résolu le problème couplé de transfert de masse et de chaleur en prenant en compte couches limites thermiques et diffusives. Une représentation adimensionnelle des transferts à l'aide des nombres de Nusselt et de Sherwood en fonction du nombre de Graetz permet de décrire de manière générale les différentes zones thermiques et diffusives. Les variations de la température et la concentration à l'interface sont prises en compte, en considérant la linéarité des équations de transfert et, en appliquant la théorie des perturbations. Un banc d'essais a été spécifiquement développé pour l'étude de l'absorption de vapeur sur des films ruisselants de bromure de lithium à basse Reynolds (Re < 500). Il permet de fixer l'état de la solution LiBr à l'entrée (température, concentration et débit) ainsi que les conditions aux limites (pression de vapeur, condition adiabatique ou de température imposée à la paroi verticale). Différentes géométries de plaque sont comparées aux résultats du model en vu de quantifier l'impact des effets de bord et des instabilités.

Tese de Doutoramento Programa Doutoral em Engenharia Electrónica e Computadores.
Rechargeable energy storage relies mainly on lithium-ion battery technology, the same that supports most of the mobile world. This technology is under research by many groups around the world and is still considered the best way to store electrical energy from intermittent power sources. However, battery technology is limiting the evolution of many integrated electronics, especially in wearable applications; improvements in terms of energy density, higher number of life cycles, flexibility and safety are still needed. In thin-film batteries, the selection, the design structure, fabrication process and characterization of materials as well as film deposition techniques play an important role in the maximization of the battery performance, durability and reproducibility. This thesis contributes to battery technology in several ways. The use of a typical flexible substrate (Kapton®, by Dupont™) while fabricating all battery materials in the same chamber, including barrier and encapsulation materials, excluding the necessity for extra vacuum and glove-box chambers, was researched. Using only safe solid-state materials, on which no leakage or explosions can occur and replacing metallic lithium (Li) anode for a much more “friendly” material in terms of fabrication and battery cycling, battery energy density benefits. The thin-film lithium phosphorous oxynitride (LiPON) electrolyte is required to have high ionic conductivity, a negligible electrical conductivity and to be stable in contact with the anode and cathode electrodes. LiPON electrolyte was deposited by RF sputtering at different experimental conditions. The highest ionic conductivity of 1 x 10-6 S/cm was measured at ambient temperature of 35 ⁰C for a film deposited with power supply of 150 W, 20 sccm of nitrogen (N2) and a deposition pressure of 3 x 10-4 mbar. Samples with a silicon nitride (Si3N4) barrier layer, a titanium (Ti) adhesion layer and a platinum (Pt) cathode current collector layer (Kapton/Si3N4/Ti/Pt) were prepared for flexibility experiments of Kapton® substrate. Si3N4 Li barrier layer was deposited by RF sputtering deposition technique with an electric resistivity of 9.51 x 1011 Ωcm and a mean breakdown field of 1.67 MV/cm. Thin-films continued attached to the substrate after several bends. Lithium cobalt oxide (LiCoO2) cathode was deposited on top of Kapton/Si3N4/Ti/Pt structure. After LiCoO2 deposition, annealing at 400 ⁰C was performed during 1 hour at different atmospheres (vacuum and air). The films annealed in air atmosphere presented higher crystallinity, especially in the plane (101), the orientation required for batteries with improved performance and durability. Cathode LiCoO2 films were deposited by RF sputtering with a 120 W power supply, pressure of 6 x 10-3 mbar and 17/3 sccm of Ar/O2 gases, respectively. A thin-film flexible Li battery and a thin-film flexible Li-ion battery were successfully fabricated using only physical vapour deposition (PVD) techniques. The anodes of metallic Li (for Li-battery) and germanium (Ge) (for Li-ion battery) were deposited 3 μm thick by thermal evaporation and 300 nm thick by e-beam, respectively. A well-organized battery structure with smooth interfaces and good adhesion was observed by scanning electron microscope (SEM) analysis. A self-discharge was measured and related to a possible thinner electrolyte in some area between the cathode and the anode on both fabricated batteries. A low potential and retention fading along charge/discharge cycles were also measured and related to an amorphous LiCoO2. Despite the low capacity presented by the two batteries, an improvement when the Li anode was changed to Ge is evident (0.35 nAh/cm2 with Li anode, to 46 nAh/cm2 with Ge anode). A battery encapsulation with three sputtered layers: lithium phosphorous oxide (LiPO), LiPON and Si3N4, each 20 nm thick, was fabricated. After these depositions and at atmospheric conditions, an epoxy was applied on the PVD multilayer to complete the encapsulation for long term protection. Research indicates it is possible to fabricate flexible thin-film Li batteries on Kapton® substrate using only PVD deposition techniques, avoiding the necessity of extra vacuum and glove-box chambers.
O armazenamento de energia elétrica recarregável baseia-se principalmente na tecnologia de baterias de iões de lítio, a mesma que suporta a maior parte do mundo móvel. Esta tecnologia está sob investigação por muitos grupos ao redor do mundo e ainda é considerada a melhor forma de armazenar energia elétrica a partir de fontes de energia intermitentes. No entanto, a tecnologia das baterias está a limitar a evolução da eletrônica integrada, especialmente em aplicações portáteis; melhorias em termos de densidade de energia, maior número de ciclos de carga/descarga, flexibilidade e segurança ainda são necessários. Em baterias de filme fino, a seleção, a estrutura, o processo de fabricação e caracterização dos materiais, bem como as técnicas de deposição dos filmes, desempenham um papel importante na maximização do desempenho, durabilidade e reprodutibilidade da bateria. Esta tese contribui para a tecnologia das baterias de várias maneiras. A utilização de um substrato flexível típico (Kapton®, por Dupont™), enquanto todos os materiais da bateria são fabricados na mesma câmara, incluindo os materiais para encapsulamento e barreira, excluindo a necessidade de câmaras de vácuo e câmaras de luvas extra, foi investigada. Utilizando apenas materiais seguros e em estado sólido, em que derramamentos ou explosões não podem ocorrer, e substituindo o ânodo de lítio (Li) metálico por um material muito mais "amigável" em termos de fabricação e de carga/descarga da bateria, a densidade de energia da bateria beneficia. O eletrólito de filme fino de oxinitreto fosfato de lítio (LiPON) deve ter elevada condutividade iónica, condutividade elétrica negligenciável e ser estável em contacto com o ânodo e cátodo. O LiPON foi depositado por pulverização catódica de radio frequência (RF sputtering) em diferentes condições experimentais. A maior condutividade iónica (1 x 10-6 S/cm) foi medida à temperatura ambiente de 35 ⁰C para um filme depositado com 150 W na fonte, 20 sccm de azoto (N2) e 3 x 10-4 mbar de pressão durante a deposição. Amostras com uma camada de barreira, nitreto de silício (Si3N4), uma camada de adesão, titânio (Ti), e uma camada de coletor de corrente do cátodo, platina (Pt), (Kapton/Si3N4/Ti/Pt) foram preparadas para as experiencias de flexibilidade do substrato de Kapton. A camada de barreira aos iões de lítio, Si3N4, foi depositada por RF sputtering com uma resistividade elétrica de 9.51 x 1011 Ωcm e uma tensão média de rotura de 1.67 MV/cm. Os filmes finos continuaram em cima do substrato após várias dobragens do mesmo. O cátodo de óxido de lítio cobalto (LiCoO2) foi depositado no topo da estrutura Kapton/Si3N4/Ti/Pt. Após a deposição do LiCoO2, um recozimento a 400 ⁰C foi realizado durante 1 hora a diferentes atmosferas (vácuo e ar). Os filmes recozidos em atmosfera de ar apresentaram maior cristalinidade, especialmente no plano (101), a orientação necessária para baterias com melhor desempenho e durabilidade. Os filmes de LiCoO2 foram depositados por RF sputtering com 120 W na fonte, 6 x 10-3 mbar de pressão e 17/3 sccm de gases Ar/O2, respetivamente. Uma bateria de Li e uma bateria de Li-ion, flexíveis e em filme fino, foram fabricadas com sucesso usando apenas técnicas de PVD. Os ânodos de Li metálico (para a bateria de Li) e germânio (Ge) (para a bateria de Li-ion) foram depositados com 3 μm de espessura por evaporação térmica e 300 nm de espessura por feixe de eletrões, respetivamente. Uma estrutura bem organizada, com interfaces regulares e boa adesão entre os filmes foram observados na bateria por microscopia eletrónica de varrimento (SEM). Auto-descarga foi medida e relacionada com uma área mais fina entre o eletrólito e o cátodo em ambas as baterias fabricadas. Um baixo potencial e um enfraquecimento na retenção de carga ao longo dos ciclos de carga/descarga também foram medidos e relacionados com o facto de o LiCoO2 ser amorfo. Apesar da baixa capacidade apresentada pelas duas baterias, uma melhoria quando o ânodo de Li foi alterado para o ânodo de Ge é evidente (0.35 nAh/cm2 com ânodo de Li e 46 nAh/cm2 com ânodo de Ge). Um encapsulamento para a bateria com três camadas: óxido fosfato de lítio (LiPO), LiPON e Si3N4, cada uma com 20 nm de espessura, foi fabricado por RF sputtering. Depois destas deposições e em condições atmosféricas, uma epóxi foi aplicada sobre a multicamada fabricada por PVD, para completar o encapsulamento para a proteção a longo prazo. A investigação indica que é possível fabricar baterias de Li em filme fino no substrato flexível Kapton®, utilizando apenas técnicas de deposição por PVD, evitando assim a necessidade de câmaras de vácuo e de luvas suplementares.
Fundação para a Ciência e a Tecnologia (FCT) SFRH/BD/78217/2011.
CRUP AI TC-09_14 and KNMF 2014-011-003169.

Solid state thin film lithium microbatteries fabricated by pulsed-laser deposition (PLD) are suggested. During deposition the following process parameters must be considered, which are laser energy and fluence, laser pulse duration, laser pulse frequency, target composition, background gasses, substrate temperature, target-substrate distance and orientation. The effects of the variations of the process parameters can be obtained by measuring stoichiometry, thickness, phases and structure (grain size and texture), and stress of the deposited films. Electrochemical measurements will be conducted to test the microbattery properties through open-circuit voltage, charge-discharge cycling, cyclic voltammetry, and impedance analysis.
Singapore-MIT Alliance (SMA)

Thin film lithium microbatteries were investigated in this project in which LiCoO₂ cathodes about 200 to 500 nm were fabricated by pulsed-laser deposition (PLD) at different processing parameters such as laser energy and fluence, substrate temperature, background gas pressure, and target-substrate distance. Structure, microstructure and composition of as-deposited LiCoO₂ films were determined by XRD, SEM and XPS. Optimal deposition parameters were identified. Relaxation of open-circuit voltage of as-prepared cells and charge-discharge cycling were conducted to characterize the electrochemical properties of microbatteries made of these LiCoO₂ films.
Singapore-MIT Alliance (SMA)

The incorporation of a thin film of LiNbO$\sb3$ in a conventional MOS (metal-oxide-semiconductor) structure gives the possibility of two fundamentally different types of computer memory architectures. One, based on ferroelectric switching, involves the reorganization of charge in the transistor channel to compensate for the change in surface polarization. Another, based on the bulk photovoltaic effect, creates a change in the threshold of the transistor when exposed to incident light. With the use of a molybdenum liftoff process, such ferroelectric transistors have been realized. The properties of these transistors have been measured before and after exposure to laser illumination, and before and after the application of voltage pulses.

碩士
國立成功大學
光電科學與工程研究所
95
The effects of thin lithium fluoride (LiF) insulating layer in pentacene-based organic thin film transistors (OTFT) are studied. The LiF thin film has been used improve the efficiency of the carrier injection. The pentacene-based OTFT with inserted LiF thin layer on different positions was fabricated. The performance of drain current is obviously enhanced while LiF is inserted between gate electrode and dielectric layer in OTFTs. Here, we carry out the structure on the plastic substrate, and the maximum saturation current increases from 7.5µA to 22µA. Furthermore, highly transparent OTFTs based on pentacene have been demonstrated. The average transmittance is as high as 71.2% in the visible region. Highly transparent OTFTs have the advantage to easily integrate with OLED in display system. By inserting thin LiF film, enhancing the drain current were obtained. The optimum thickness of LiF film (1 nm) to achieve the maximum saturation current is investigated. The maximum saturation current increases from 1.1µA to 2.58µA while we insert 1nm LiF film between ITO (Source/Drain) and pentacene. Additionally, we use conducting polymer, polyaniline (PANI), as active layer in the device. The CSA is used to improve electrical conductivity of polyaniline and its solubility. By doping-dedoping, we control of the electrical conductivity from semiconductor to insulator to attain the transistor characteristics.

碩士
國立臺灣師範大學
物理學系
105
All solid-state lithium-ion battery compared to the traditional lithium-ion battery with high energy density, more safety and more easily to processing. That was placed highly anticipated to replace the traditional lithium-ion battery. With the development of all solid-state lithium-ion battery more mature, some of its problems are also mushroomed to be excavated. If these problems can be improved to further enhance the performance of all solid-state lithium-ion battery. It is bound to commercialization to replace the traditional liquid lithium-ion battery target can go further. This study focuses on improving the efficiency of all-solid-state lithium-ion thin-film batteries. Improve the yield of the process steps. Its structure to mica tablets for the substrate. On the substrate using RF magnetron sputtering technology to deposit platinum as a current collector. Lithium cobalt oxide as a cathode material The same use of RF magnetron sputtering technology deposition of lithium cobalt oxide film as the battery cathode. Deposition of Lithium Phosphorus Oxides on Thin Films by RF Magnetron Sputtering as Solid Electrolytes. After the solid electrolyte was formed, the lithium metal was deposited on the electrolyte by thermal evaporation as an anode. That is, the completion of all solid-state lithium-ion battery assembly In this study, it was found that the thermal annealing of the semifinished product of lithium-phosphorous nitrogen oxide sputtering can greatly improve the stability of the subsequent lithium metal vapor deposition process. Increase its yield from 25% to 83%. The surface and profile of lithium-phosphorus oxynitride after thermal annealing were observed by scanning electron microscopy. The coordination structure of the samples was observed by x - ray photoelectron spectroscopy. The measurement of ionic conductivity was measured with an AC impedance meter. The elemental composition was determined by Energy-dispersive X-ray spectroscopy. Finally, charge and discharge test with a charge and discharge instrument. According to the above comprehensive observation found that lithium-phosphorus oxynitride 50°C thermal annealing for 60 min ion conductivity can reach 1.1x10-6 S/cm and the cycle charge and discharge test after the second round of the Cullen efficiency of 95% or more. This study also utilizes the concept of artificial solid electrolyte interfacial thin films. Lithium iodide was deposited on the lithium-phosphorus oxynitride electrolyte with lithium metal anode as an artificial solid electrolyte. And the above test, a comprehensive observation found that the deposition of 5 nm lithium iodide in the lithium-phosphorus oxynitride and lithium metal interface can make the first circle of Coulomb efficiency from 72% to 82%. And the combination of the above two experiments in the lithium phosphorous oxide produced after the completion of thermal annealing and evaporation of 5 nm lithium iodide can fully enhance its battery Coulomb efficiency. So that the first Coulomb efficiency from 72% to 80% and the second lap after the average efficiency of the Coulomb from 85% to 95%.The success of a comprehensive upgrade of the battery Coulomb efficiency.

碩士
國立臺南大學
機電系統工程研究所碩士班
107
Technology brings convenience and progress to humans, and sensors are one of the indispensable roles. Through the recent development of Industry 4.0 in various industries, it has been found that different types of sensors are widely used and developed. Therefore, this research aims to develop a flexible and lead-free lithium niobate film pressure sensor. The pressure sensor is prepared by using a Sol-Gel Method to prepare a lithium niobate (LiNbO3) solution, and spin-coating the lithium niobate solution uniformly on the aluminum substrate. It is deposited to form a lithium niobate film. In this study, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to observe the crystal phase, material properties and surface morphology of the film. It was confirmed that lithium niobate was deposited on the substrate. At the same time, the piezoelectric effect of the lithium niobate film was tested using a dynamic measurement platform and a drop test. It can be known from the research results that the lithium niobate solution prepared by the process parameters at a concentration of 0.4 mol and the deposition of three layers of lithium niobate film on the substrate at an annealing temperature of 550 ° C have the best response voltage.

The spontaneous polarization of thin film LiNbO$\sb3$ has been shown to be reversible with the application of an electric field at room temperature. This electric field is applied across the sample in the form of a voltage pulse, and polarization reversal is detected either as a photocurrent reversal, or as a current transient whose integrated area is proportional to the spontaneous polarization. For 80 mil$\sp2$ size areas of thickness.3 $\mu$m, the fastest switching speed was 500 ns. The samples consisted of a silicon substrate, a thin film of LiNbO$\sb3$ and a metal contact to form an MFS (metalferroelectric-semiconductor) structure. The LiNbO$\sb3$ film was formed by rf sputtering LiNbO$\sb3$ onto heated $\langle111\rangle$ silicon substrates.

Ferroelectric thin films of lithium niobate have been epitaxially grown on a variety of silicon and gallium arsenide substrates by reactive r.f. sputtering. The deposition process was optimized by independently varying the substrate temperature, oxygen-argon ratio, target mixture, substrate type, and deposition times. The results of these tests are presented. The lithium niobate thin films were structurally analyzed using Bragg x-ray diffraction (XRD) and scanning electron microscopic (SEM) techniques to determine their orientation, grain size, and domain structure. Electrical characterization included C-V measurements utilized to calculate the permittivity, I-V to obtain the resistivity, and photocurrent measurements to verify the existence of a bulk photovoltaic and pyroelectric effect in the thin films. In addition, preliminary results on prefabricated devices are presented as well as a review of the pertinent effects and potential device applications based on thin films of lithium niobate.

Highly oriented polycrystalline thin films of lithium niobate on (012), (100), and (110) sapphire single crystal substrates, (111) silicon and SiO$\sb2$/(100)Si wafers were grown by magnetron rf sputtering and metallo-organic decomposition techniques. A novel technique of photo-induced metallo-organic decomposition (PIMOD) is proposed and implemented to eliminate inter-diffusion and cracking which are commonly observed in MOD-derived films. Results of XRD, TEM, and ion beam spectrometry confirm that highly oriented, polycrystalline, stoichiometric lithium niobate thin films have been successfully grown on a variety of substrates. Prism coupling has been used to excite the guided modes in the optical thin film waveguides. The optical and electrooptic properties, including the refractive index, propagation losses, and electrooptic coefficient, were investigated. Finally, an electrooptic phase modulator was implemented.

碩士
國立臺灣師範大學
物理學系
103
In our life, there are more and more portable electronic devices and wearable electronic devices when the technology is improving all the time. Therefore, the requirement of batteries is more important now. Because all-solid-state thin film battery feature with good safety and high energy density, it is much potential for the development of future work. In our experiment, we try to make all-solid-state thin film batteries. We use ruby mica scratchfree to be the substrate. First, we deposit platinum by direct current sputtering as a current collector. Then, we deposit lithium cobalt oxide (LiCoO2) cathode material and lithium phosphorus oxynitride (LiPON) solid electrolyte on the platinum current collector by radio frequency sputtering. Finally we fabricate the lithium metal and aromatic polyurea to be the anode material and encapsulation by thermal evaporation. We use the furnace and rapid thermal annealing (RTA) to heat the cathode material, and control the heating rate of machine. We use x-ray diffraction to analyze the crystalline structure. Scanning electron microscope is used to observe the surface morphology, and capacity test is able to decide the chemical properties of cathode material. In the part of solid electrolyte, we use hot plate to heat the LiPON film in different temperature. And we measure the electrochemical impedance spectroscopy to calculate the ion conductivity. Using the rapid thermal annealing (RTA) at the rate of 260oC/min is a good way to heat the LiCoO2 film. And we use hot plate at the 200oC to do the heat treatment of LiPON film. Finally, we use the thermal evaporation to evaporate the lithium metal. The complete all-solid-state thin film battery can do the cycle test and light the LED.

碩士
國立臺灣科技大學
材料科技研究所
92
The main objective of the present study is to investigate the LiMn2O4 cathode films deposited on the silicon substrate and Aluminum foil by means of RF-sputtering. The structural and surface morphology of the deposited films at various annealing temperatures were analyzed by employing XRD and SEM techniques. The LiMn2O4 cathode films were tested their charge - discharge characteristics and analyzed. The LiMn2O4 films were also deposited on plastic Kapton substrate to fabricate a flexible Li-ion micro-battery. The LiMn2O4 films were deposited on Si and Al foil by changing the deposition conditions such as working pressure, sputtering power, substrate temperature in order to obtain high quality and homogeneous films. The structural and surface morphology of the deposited films were analyzed by means of X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). It was found that the best deposition conditions to yield high quality films, from the film properties, at room temperature are: working pressure is 1.2×10-2 torr, sputtering power is 70 W and deposition time is 15 hrs. The crystallinity of the LiMn2O4 film was found for an annealing temperature at 700 0C. The cycle test was performed and it was found that the specific capacity of the film increases with the increase of the annealing temperature. It suggests that the crystallinity of the film increases with an increase in annealing temperature. In order to bring down the annealing temperature to lower than that of kapton melting temperature, we have deposited an oxide layer of ITO or SnO2, between the contacts and active material. It was found that the diffraction peak (111) would appear even without heat treatment. The diffraction peaks (111), (311), (400) are obvious, when the film was annealed at 200 0C. This means that the crystallized LiMn2O4 cathode films can be produced at lower temperature. Our interest is to deposit LiMn2O4 film on a plastic Kapton substrate to make a Li-ion micro-battery more flexible. In this direction, we have designed and fabricated variety of geometry of cells using the Kapton substrate. However, the charge and discharge characteristics of the tested cells are not as good as films deposited on Al foil. In order to fabricate a flexible Li-ion micro-battery, we need to improve our design to avoid moisture or air leak and reduce the internal impedance of the battery.

abstract: Lithium metal is a promising anode for the next generation lithium batteries owing to its high capacity (3860 mAh g-1) and the lowest negative reduction potential (-3.04 V). Commercial produced lithium anodes have a native rough surface which deteriorates the cycling performance of the battery. Here, an attempt has been made to deposit lithium on copper from an electrolytic cell consisting of simple electrolyte of pyridine and lithium chloride at room temperature. Water is known to react aggressively with the lithium metal, however in the electrochemical plating process, it has a significant beneficial effect in catalyzing the electrochemical reactions. The effect of trace amounts of water was investigated in air as well as in controlled atmosphere of argon, nitrogen, breathing grade dry air and ultra-zero dry air. The electrochemical products examined by Fourier transform infrared spectroscopy revealed the deposition might require the reduction of pyridine to facilitate the reduction of the lithium salt. Purity of the lithium film was determined by inductively coupled plasma mass spectrometry.
Dissertation/Thesis
Masters Thesis Materials Science and Engineering 2019

Lithium ion batteries have been regarded as one of the most promising and intriguing energy storage devices in modern society since 1990s. A lithium ion battery contains three main components, cathode, anode, and electrolyte, and the performance of battery depends on each component and the compatibility between them. Electrolyte acts as a lithium ions conduction medium and two electrodes contribute mainly to the electrochemical performance. Generally, cathode is the limiting factor in terms of capacity and cell potential, which attracts significant research interests in this field.Different from conventional slurry thick film cathodes with additional electrochemically inactive additives, binder-free thin film cathode has become a promising candidate for advanced high-performance lithium ion batteries towards applications such as all-solid-state battery, portable electronics, and microelectronics. However, these electrodes generally require modifications to improve the performance due to intrinsically slow kinetics of cathode materials.

In this thesis work, pulsed laser deposition has been applied to design thin film cathode electrodes with advanced nanostructures and improved electrochemical performance. Both single-phase nanostructure designs and multi-phase nanocomposite designs are explored. In terms of materials, the thesis focuses on manganese based layered oxides because of their high electrochemical performance. In Chapter 3 of the nanocomposite cathode work, well dispersed Au nanoparticles were introduced into highly textured LiNi_0.5Mn_0.3Co_0.2O₂ (NMC532) matrix to act as localized current collectors and decrease the charge transfer resistance. To further develop this design, in Chapter 4, tilted Au pillars were incorporated into Li₂MnO₃ with more effective conductive Au distribution using simple one-step oblique angle pulsed laser deposition. In Chapter 5, the same methodology was also applied to grow 3D Li₂MnO₃ with tilted and isolated columnar morphology, which largely increase the lithium ion intercalation and the resulted rate capability. Finally, in Chapter 6, direct cathode integration of NMC532 was attempted on glass substrates for potential industrial applications.

碩士
國立雲林科技大學
工業化學與災害防治研究所
94
In our study, cathodic lithium manganese oxide film with spinel structure was deposited by radio frequency magnetron sputtering. The sputtering energy and the annealing temperature can control the size of grain clustering effectively. Thus, sputtering energy can affect the growth and rearrangement of grain particle, and the annealing temperature can improve the characteristics of crystallization of the thin film. The effects of the sputtering power, sputtering pressure, and the annealing temperature on the structure and the characteristics of LiMn2O4 thin films were studied. The structure and surface morphology of the thin films were investigated by using X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FE-SEM), Atomic Force Microscope (AFM), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The XRD pattern indicated that the strength of the LiMn2O4 thin film crystalline increased with increasing of the sputtering power and pressure. When the annealing temperature was increased from 600℃ to 800℃ gradually, it improved the strength of crystalline and grain size. Form the result of charge-discharge tests, LiMn2O4 spinel films prepared at 50 mTorr and at annealing temperature of 750℃ had favorable nanoparticles with structural stability and better charge-discharge properties.

碩士
國立成功大學
電機工程學系碩博士班
95
Organic thin film transistors based on conjugated polymer such as poly-diallyldimethylammonium chloride (PDDA) / Poly-diphenylamine (PDPA) and small molecule such as pentacene. Poly(4-vinylphenol) are investigated as a dielectric material instead of SiO2. ITO glass as gate electrodes due to its conductivity as well as transparent properties is applied to the transistor fabrication. 　　Until now, the performance of pentacene-based organic thin film transistors is the most widely studied. A lithium fluoride (LiF) thin film has been used in organic light emitting diodes to improve the efficiency of the carrier injection. Here, we deposit an ultra-thin LiF film between gate electrode and dielectric layer in pentacene-based OTFTs. The on/off current ratio (up to 106) is obviously improved as thickness of the LiF film is approximately 5.0 nm. The mechanisms are also studied. By removing the active layer from pentacene-based OTFTs to fabricate capacitors, the capacitance trend is similar to the drain current at on-state and off-state regions as well as on/off current ratio. 　　In the second part, anions of PDDA can be doped into PDPA through applying a negative bias in order to modulate the conductivity of PDPA. As a result of this mechanism, the PDPA/PDDA bilayer is employed as an active semiconductor layer to demonstrate conjugated polymer OTFTs.

博士
國立清華大學
化學工程學系
85
This work examines the formation of passive film on the carbon electrode of lithium batteries. According to those results, with a single solvent of EC (ethylene carbonate), the structure of the passive film was found to be (CH2OCOOLi)2 on the carbon electrode''s surface. In the DEC (diethyl carbonate) or DMC(dimethyl carbonate) system, C2H5OCOOLi and Li2 CO3 were formed on the carbon electrode''s surface. According to mass spectra, CO2 gas is the main product when EC is decomposed. In addition , DEC is decomposed into CO and C2H6 and DMC into CO and CH4 as well. Those results suggest the composition ofpassive film depends on the solvent''s property. In a binary solvent system which contains EC, the passive film still contains chiefly (CH2OCOOLi)2, which is identical to a single EC solventsystem. This work examines the interface between carbon electrode and organic electrolyte of lithium ion battery by AC impedance technology. A five RC circuits model was adopted to investigate the interfacial property. It was found in EC or DMC electrolyte system, the total interfacial resistance and the passive film'' s thickness increase with a decreasing intercalation potential. However, in DEC system, the total interfacial resistance and the passive film''s thickness decrease as intercalation proceeds. The porous layer of the passive film obviously affects the total interfacial resistance in a single which organic electrolyte. Furthermore, the total interfacial resistance and the passive film''s thickness remain constant after the initial intercalation. This finding suggests that the passive film''s property is steady in a single electrolyte system. In the binary electrolyte system such as EC/DEC or EC/ DMC system, the effects of porous parts on the total interfacial resistance are slight. However, the total interfacial resistance and the passive film''s thickness are smaller than that in a single electrolytesystem. In addition, the variation of the total interfacial resistance and the passive film''s thickness in EC/DEC (or EC/DMC) electrolyte are similar to DEC (or DMC) electrolyte during intercalation progress, respectively.

博士
逢甲大學
材料科學與工程學系
104
High power density and high energy density are the characteristics of lithium-ion batteries, which have become the mainstream power sources of consumer electronics in recent years. In order to satisfy the energy demand for the development of electric products, improving the performance of energy storage materials is a critical issue. Thin film electrode is a useful platform for research in energy storage materials free of binders and conducting additives. In this study, the lithium transition metal oxides, including lithium nickel manganese oxide and lithium iron phosphate thin film electrodes for energy storage devices were investigated and discussed. LiNi0.5Mn1.5O4 (LNMO) thin films have been deposited on stainless steel substrates using radio frequency (f = 13.56 MHz) magnetron sputtering, followed by thermal annealing in ambient atmosphere. Various negative biases were applied on the substrates during deposition. The structural evolution of LNMO thin films under different negative biases has been investigated and characterized by X-ray diffraction. All of the deposited films exhibit a crystalline spinel structure with a space group of Fd-3m, which is so-called disordered phase. The results also indicate that particle size decreases with increasing negative bias. The electrochemical properties of the LNMO thin films as cathode materials for lithium ion batteries were investigated. Two distinctive voltage plateaus at ~4.7 V and at ~4.0 V (vs. Li+/Li) can be observed in the discharge curves, corresponding to the reactions of the disordered phase. The capacity of LNMO thin film electrodes under suitable negative bias can be optimized. Experimental realization of nitrogen doping into LiFePO4 films has been carried out by reactive sputtering on graphite substrates without any carbon additive. LiFePOxNy films were deposited under various N2/(Ar/H2) flow ratios followed by thermal annealing under Ar/H2 gas mixture. The amounts of nitrogen doping increased with the N2/(Ar/H2) flow ratios. Enhanced Li-N signals were recorded by Fourier transform infrared spectroscopy, where Nitrogen substitutes for Oxygen at LiO6 octahedral structure in LiFePO4. The binding energy bands of the double and triple coordinated N-P bonds were found and both N-P bonds increase with nitrogen doping as characterized by X-ray photoelectron spectroscopy (XPS). With nitrogen doping, Fe2+ remained unchanged, whereas Fe-O defects in FeO8 octahedron increased. Nitrogen doping has effectively elevated the conductivity of the films to the order of 104 S/cm, and also reduced the electrochemical impedance. The charge-discharge tests show that capacity of 140 mAh/g at 0.2 C can be obtained with appropriate nitrogen doping. Even at a current rate of 10 C, the optimized LiFePOxNy film can delivers a capacity of 100 mAh/g. The LiFePOxNy films were charged-discharged for 100 cycles at 1C, and 97 % of capacity retention can be achieved for most films. As for the high power applications, such as power tools and electric vehicles, high conductivity LiFePOxNy thin films were further studied as electrode materials for pseudocapacitors. LiFePOxNy thin films were sputter-deposited on micron carbon fibers (MCFs) under a gas mixture of N2/Ar/H2 as electrode materials in pseudocapacitors. The MCFs were fabricated by thermal chemical vapor deposition on stainless steel substrates as current collectors. Various amounts of N2 were introduced by controlling the flow ratios of N2 to Ar/H2. The LiFePOxNy thin films coated on the surfaces of MCFs were observed by field emission scanning electron microscopy. The electrochemical properties of the LiFePOxNy thin films were characterized using cyclic voltammetry and charge-discharge processes. The LiFePOxNy thin-film electrode deposited under the optimal N2 contents exhibited a high specific capacitance of 722 F/g at 1 A/g. Even at a current of 20 A/g, the electrode delivered a capacitance of 298 F/g. The pseudocapacitors using LiFePOxNy thin film electrodes showed no significant capacitance fading after 1000 cycles at 1 A/g. The results indicated that nitrogen doping improved the electrochemical performances of LiFePO4, demonstrating the potential of LiFePOxNy as an active material in pseudocapacitors.

碩士
逢甲大學
材料科學與工程學系
107
More and more researches on solid-state electrolytes for lithium-ion batteries have been conducted in recent years. Advantages of using solid electrolytes: (1) no leakage problems (2) wide range of sizes (3) high energy density (4) solid electrolytes are inorganic electrolytes, high safety and environmentally friendly (5) package without traditional batteries The case of the volume (Dead Volume). The solid electrolyte many advantages but still not commercialized there are two main reasons: the low ionic conductivity of the solid electrolyte and the high interfacial resistance between the electrodes and solid electrolytes. In this study, LiPON film was prepared by RF magnetron sputtering, and the film thickness was reduced to reduce the internal impedance. In addition, selection of the liquid electrolyte is a solvent which EC, EMC, solutes are LiPF6, was added Polyimide (PI) in the liquid electrolyte with different mixing ratios of the gel buffer layer, EIS analysis was performed with Blocking Electrode structure S.S/LiPON/buffer/S.S. The solid-state thin film lithium ion batteries are used LiCoO2 cathode, TiO2 anode structures such as: LiCoO2/LiPON / buffer/TiO2.The performances solid-state thin film lithium ion batteries have a good reversibility over 50 charge-discharge cycles between 3.5 V and 1 V.

碩士
國立中興大學
材料科學與工程學系所
98
Using copper (Cu) substitute for replacing conventional metallic Li, thin-film lithium-ion batteries LiMn2O4/LiClO4/Cu were prepared of. They were further characterized by X-ray diffraction (XRD), FE-SEM, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and charge-discharge cyclic tests. The LiMn2O4 film surface morphology was uniform by FESEM observations. XPS analysis showed that lithium content on the copper foil the first cycle charging was 8.3%. The CV measurement showed oxidation peaks at 2.59, 2.85, 3.34 and 3.60 V, and reduction peaks at 3.15, 2.15 and 1.21 V. The first discharge capacity was 40mAh/g and degraded to 17mAh/g at 20th cycle at current density 10μA/cm2. Compared with Li metal anode, Cu was oxidized into CuO by LiClO4 strong oxidizer (Cu+ClO4→CuO+ClO3 ). During the charging, the reduction of Li+ was partially replaced by the reduction of Cu (CuO+2Li++2e-→Cu+Li2O ), therefore, resulting in the loss of capacity. Selecting a metal anode which will not be oxidized by the electrolyte could improve the reversible capacity.

碩士
國立清華大學
奈米工程與微系統研究所
104
This work implements single crystal X-cut thin film Lithium Niobate (LN) in order to achieve a high electromechanical coupling coefficient kt^2.of the shear horizontal acoustic plate wave (SH-APM) resonators. The design of the device is carried out by the Finite Element Method (FEM) that can simulate the frequency of the SH0 mode resonators and their mode shape, and we use their frequency response to calculate the coupling coefficient that would be compared with the theoretical analysis and numerical result of prior arts; then we can confirm the validation of our simulation approach. In literature, the resonator possesses a high coupling coefficient at SH0 mode using the X-cut Lithium Niobate, which becomes our target in this work. In the fabrication process, we obtain off-the-shelf single crystal X-cut Lithium Niobate dies and we are using surface micromachining technology to fabricate the resonators. We design two fabrication process flows using the limited academic process resources and test the feasibility of the fabrication process. This process is roughly divided into three parts; the first part is photolithography, primarily responsible for defining the electrodes and etching holes; the present process for fabrication uses two masks. The second part is Lithium Niobate etching process. The third part is to etch the silicon dioxide; thus we use the wet HF to release the thin film structure. This study successfully demonstrated measurement results of the piezoelectric resonator with quality factor of 60, the electromechanical coupling coefficient of 15.8%, and motional impedance of 28.5 kΩ, respectively.

Thin films of lithium niobate on various oriented sapphire substrates were fabricated by the rf sputtering method. Polarized He-Ne laser light with a wavelength of 6328 A was successfully coupled into the optical waveguides by a rutile prism coupler. A description of the prism coupler used for this research is given. The guided modes excited by the prism coupler were observed and used to examine the optical properties of the waveguide. The refractive indices and thicknesses of various samples were calculated and tabulated. The birefringence observed in the films and x-ray diffraction studies have confirmed the polycrystalline nature of the films. The attenuation of the light propagating in various (zeroth- to second-order) waveguide modes was determined to be in the range of 1.1 to 1.3 $\pm$ 0.1 dB/cm.