Tesis sobre el tema "Lithium deposition"

Current batteries for soldier systems rely on many different standard power source sizes, shapes and weights. The integration of power sources into space-limited platforms and to fit to a soldier correctly is difficult. Conventional layer by layer manufacturing approaches are still relied on for battery production. 3D battery systems offer the potential to produce batteries that are bespoke to equipment size and shape whilst maintaining the advantages of the thin film battery manufacturing techniques. There are several techniques available to produce these 3D battery systems and this thesis will look at the application of on one such technique, electrophoretic deposition to lithium iron phosphate (LFP) battery positive electrode materials. Electrophoretic deposition is a technique where an electric field is used to deposit particles from a colloidal suspension onto a conducting surface. This thesis will present the development of the electrophoresis technique for flat plate samples of the LFP through deposition from a suspension of LFP particles in iso propyl alcohol with a metal salt. The results of studies using cyclic voltammetry and impedance spectroscopy will then be presented and discussed in relation to deposition parameters and to gain a greater understanding of the resistances present between the LFP particles in the binder and carbon additive-free electrodes.

Intercalation of lithium into Ag-CNTs sample is reported here. We have used a nano- porous silver foam as a frame for deposition of the CNTs inside the pores by electrophoresis deposition (EPD) technique. By using chronopotentiometry method, we have noticed that the Li storage capacity of the prepared Ag-CNTs electrode was im- proved noticeably in comparison with literature. In addition, a very good functional stability for the prepared electrode has been tested during subsequent cycles of charge / discharge (C&D) procedures. By scanning the cycle's regulated current from 0.2 up to 1.0 mA , it was shown that in the range of 0.4 - 0.6 mA the Li storage capacity and reversibility of the C&D cycles became optimum, as well. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20610

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2020
Cataloged from the PDF of thesis.
Includes bibliographical references (pages 104-107).
Solid-state Li metal batteries require accommodation of electrochemically generated mechanical pressure inside Li metal. In this thesis it shows, through in situ transmission electron microscopy experiment of Li and Na deposition/stripping in mixed ionic-electronic conductor (MIEC) hollow tubules, an intriguing result that (a) Li metal can flow and retract inside 3D MIEC channels as a single crystal, (b) Coble creep dominates via interfacial diffusion along the MIEC/metal phase boundary, (c) this MIEC electrochemical tubular matrix can effectively relieve stress, maintain electronic and ionic contact, eliminate solid-electrolyte interphase (SEI) debris, reduce the possibility of "dead lithium", and allow the reversible deposition/stripping of Li metal across a distance of many microns, for 100 cycles. This thesis proposes quantitative design rules for MIEC electrochemical cell and shows that interfacial diffusion greatly liberates MIEC material choices when using ~100 nm wide and 10-100[mu]m deep channels. A centimeter-scale, ~10¹⁰ MIEC cylinders/solid electrolyte/LiFePO₄ full cell shows high capacity of ~ 164 mAh/g(LiFePO₄ and almost no degradation for over 50 cycles, starting with 1x excess Li.
by Ziqiang Wang.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering

Recent advances in the electric & hybrid electric vehicles and rapid developments in the electronic devices have increased the demand for high power and high energy density lithium ion batteries. Graphite (theoretical specific capacity: 372 mAh/g) used in commercial anodes cannot meet these demands. Amorphous SnO2 anodes (theoretical specific capacity: 781 mAh/g) have been proposed as alternative anode materials. But these materials have poor conductivity, undergo a large volume change during charging and discharging, large irreversible capacity loss leading to poor cycle performances. To solve the issues related to SnO2 anodes, we propose to synthesize porous SnO2 composites using electrostatic spray deposition technique. First, porous SnO2/CNT composites were fabricated and the effects of the deposition temperature (200,250, 300 oC) & CNT content (10, 20, 30, 40 wt %) on the electrochemical performance of the anodes were studied. Compared to pure SnO2 and pure CNT, the composite materials as anodes showed better discharge capacity and cyclability. 30 wt% CNT content and 250 oC deposition temperature were found to be the optimal conditions with regard to energy capacity whereas the sample with 20% CNT deposited at 250 oC exhibited good capacity retention. This can be ascribed to the porous nature of the anodes and the improvement in the conductivity by the addition of CNT. Electrochemical impedance spectroscopy studies were carried out to study in detail the change in the surface film resistance with cycling. By fitting EIS data to an equivalent circuit model, the values of the circuit components, which represent surface film resistance, were obtained. The higher the CNT content in the composite, lower the change in surface film resistance at certain voltage upon cycling. The surface resistance increased with the depth of discharge and decreased slightly at fully lithiated state. Graphene was also added to improve the performance of pure SnO2 anodes. The composites heated at 280 oC showed better energy capacity and energy density. The specific capacities of as deposited and post heat-treated samples were 534 and 737 mAh/g after 70 cycles. At the 70th cycle, the energy density of the composites at 195 °C and 280 °C were 1240 and 1760 Wh/kg, respectively, which are much higher than the commercially used graphite electrodes (37.2-74.4 Wh/kg). Both SnO2/CNTand SnO2/grapheme based composites with improved energy densities and capacities than pure SnO2 can make a significant impact on the development of new batteries for electric vehicles and portable electronics applications.

Thesis (Ph.D.)--Tufts University, 1996.
Adviser: Terry E. Haas. Submitted to the Dept. of Chemistry. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis advisor: Dunwei Wang
When their electrodes are made of nanomaterials or materials with nanoscale features, devices for energy conversion and energy storage often exhibit new and improved properties. One of the main challenges in material science, however, is to synthesize these nanomaterials with designed functionality in a predictable way. This thesis presents our successes in synthesizing TiSi₂ nanostructures with various complexities using a chemical vapor deposition (CVD) method. Attention has been given to understanding the chemistry guiding the growth. The governing factor was found to be the surface energy differences between various crystal planes of orthorhombic TiSi₂ (C54 and C49). This understanding has allowed us to control the growth morphologies and to obtain one-dimensional (1D) nanowires, two-dimensional (2D) nanonets and three-dimensional (3D) complexes with rational designs by tuning the chemical reactions between precursors. Among all these morphologies, the 2D nanonet, which is micrometers wide and long but only approximately 15 nm thick, has attracted great interest because it is connected by simple nanostructures with single-crystalline junctions. It offers better mechanical strength and superior charge transport while preserving unique properties associated with the small-dimension nanostructure, which opens up the opportunity to use it for various energy related applications. In this thesis we focus on its applications in lithium ion batteries. With a unique heteronanostructure consisting of 2D TiSi₂ nanonets and active material coating, we demonstrate the performances of both anode and cathode of lithium ion batteries can be highly improved. For anode, Si nanoparticles are deposited as the coating and at a charge/discharge rate of 8400 mA/g, we measure specific capacities >1000 mAh/g with only an average of 0.1% decay per cycle over 100 cycles. For cathode, V₂O₅ is employed as an example. The TiSi₂/V₂O₅ nanostructures exhibit a specific capacityof 350 mAh/g, a power rate up to 14.5 kW/kg, and 78.7% capacity retention after 9800 cycles. In addition, TiSi₂ nanonet itself is found to be a good anode material due to the special layer-structure of C49 crystals
Thesis (PhD) — Boston College, 2012
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

La réaction de dépôt de lithium est un phénomène local et indésirable au sein des batteries Li-ion. Elle est largement décrite dans la littérature comme l'un des principaux phénomènes limitants de la charge rapide des cellules Li-ion. Le contrôle de cette réaction en temps réel est donc un facteur clé pour parvenir à la charge "au plus juste" d'un batterie Li-ion. Cela est classiquement étudié par des modèles physiques complexes et à l'aide des techniques expérimentales nécessitant des analyses invasives de la batterie. Dans le cadre de l'étude de cette thèse, il a été mis en place une méthodologie, incluant une modélisation simplifiée ainsi que des caractérisations expérimentales non invasives des cellules Li-ion, pour estimer l'ensemble des courants de recharge proche de la limite de la réaction de dépôt de lithium. Des études expérimentales ont été menées sur une cellule graphite/LFP pour valider ce courant et cela a donné lieu à un protocole de recharge où le courant évolue avec l'état de charge et la température de la cellule. Il a été observé que ces courants permettent de charger ultra rapidement la cellule sans que la réaction de dépôt de lithium métal ne soit déclenchée. Pour une charge à 0°, la cellule a été chargée en 11 minutes entre 10% et 87% d'état de charge. Il a été validé que les courants estimés sont proches, à moins de 10%, de la limite « réelle » de déclenchement de la réaction de dépôt de lithium. Enfin, en comparant les cyclages avec ces courants limites estimés et la charge à 1C, aucun vieillissement additionnel n'a été observé après plus de 100 cycles à 0°
Lithium deposition reaction is a local and undesirable phenomenon within Li-ion batteries. It is widely describe in the literature as one of the major limiting phenomena of rapid Li-ion cell loading. The control ofthis reactio in real time therefore seems to be a key factor for an optmal fast charging. This is classically studied by ve complex physical models and using experimental techniques requiring invasive tests on battery. As part of th study ofthis thesis, a methodology has been established, including a simplified modelling as well as non-invasiv experimental characterizations of Li-ion, to estimate all charging currents close to the limit of the lithiu deposition reaction. Experimental studies have been conducted on a graphite/LFP cell to validate these current and this resulted in a charging protocol where the current evolves With the load state and temperature of the cel It has been observed that these currents allow the cell to be charged ultra quickly without triggering the lithiu metal deposition reaction. For a charge at 0°, the cell has been recharged in 11 minutes between 10% and 87% of the state of charge. It has been validated that the estimated currents are close to, less than 10%, the « real » lim for triggering the lithium deposition reaction. Finally, by comparing cycling With these estimated limit curren and the charge at IC, no additional aging has been observed after more than 100 cycles at 0°

The direct epitaxial growth of multilayer BN by atomic layer deposition is of critical significance forfo two-dimensional device applications. X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) demonstrate layer-by-layer BN epitaxy on two different substrates. One substrate was a monolayer of RuO2(110) formed on a Ru(0001) substrate, the other was an atomically clean Ni(111) single crystal. Growth was accomplished atomic layer deposition (ALD) cycles of BCl3/NH3 at 600 K substrate temperature and subsequent annealing in ultrahigh vacuum (UHV). This yielded stoichiometric BN layers, and an average BN film thickness linearly proportional to the number of BCl3/NH3 cycles. The BN(0001)/RuO2(110) interface had negligible charge transfer or band bending as indicated by XPS and LEED data indicate a 30° rotation between the coincident BN and oxide lattices. The atomic layer epitaxy of BN on an oxide surface suggests new routes to the direct growth and integration of graphene and BN with industrially important substrates, including Si(100). XPS and LEED indicated epitaxial deposition of h-BN(0001) on the Ni(111) single crystal by ALD, and subsequent epitaxially aligned graphene was deposited by chemical vapor deposition (CVD) of ethylene at 1000 K. Direct multilayer, in situ growth of h-BN on magnetic substrates such as Ni is important for spintronic device applications. Solid-state electrolytes (SSEs) are of significant interest for their promise as lithium-ion conducting materials but are prone to degradation due to lithium carbonate formation on the surface upon exposure to atmosphere, adversely impacting Li ion conduction. In situ XPS monitored changes in the composition of the SSE Li garnet (Li6.5La3Zr1.5Ta0.5O12, LLZTaO) upon annealing in UHV and upon Ar+ ion sputtering. Trends in core level spectra demonstrate that binding energy (BE) calibration of the Li 1s at 56.4 eV, yields a more consistent interpretation of results than the more commonly used standard of the adventitious C 1s at 284.8 eV. Annealing one ambient-exposed sample to >1000 K in UHV effectively reduced surface carbonate and oxygen, leaving significant amounts of carbon in lower oxidation states. A second ambient-exposed sample was subjected to 3 keV Ar+ ion sputtering at 500 K in UHV, which eliminated all surface carbon, and reduced the O 1s intensity and BE. These methods present alternative approaches to lithium carbonate removal than heating or polishing in inert atmospheres and are compatible with fundamental surface science studies. In particular, the data show that sputtering at mildly elevated temperatures yields facile elimination of carbonate and other forms of surface carbon. This is in contrast to annealing in either UHV or in noble gas environments, which result in carbonate reduction, but with significant remnant coverages of other forms of carbon.

The deposition of boron oxide (B₂O₃) films on silicon substrates is of significant interest in microelectronics for ultrashallow doping applications. However, thickness control and conformality of such films has been an issue in high aspect ratio 3D structures which have long replaced traditional planar transistor architectures. B₂O₃ films are also unstable in atmosphere, requiring a suitable capping barrier for passivation. The growth of continuous, stoichiometric B₂O₃ and boron nitride (BN) films has been demonstrated in this dissertation using Atomic Layer Deposition (ALD) and enhanced ALD methods for doping and capping applications. Low temperature ALD of B₂O₃ was achieved using BCl₃/H₂O precursors at 300 K. In situ x-ray photoelectron spectroscopy (XPS) was used to assess the purity and stoichiometry of deposited films with a high reported growth rate of ~2.5 Å/cycle. Free-radical assisted ALD of B₂O₃ was also demonstrated using non-corrosive trimethyl borate (TMB) precursor, in conjunction with mixed O₂/O-radical effluent, at 300 K. The influence of O₂/O flux on TMB-saturated Si surface was investigated using in situ XPS, residual gas analysis mass spectrometer (RGA-MS) and ab initio molecular dynamics simulations (AIMD). Both low and high flux regimes were studied in order to understand the trade-off between ligand removal and B₂O₃ growth rate. Optimization of precursor flux was discovered to be imperative in plasma and radical-assisted ALD processes. BN was investigated as a novel capping barrier for B₂O₃ and B-Si-oxide films. A BN capping layer, deposited using BCl₃/NH₃ ALD at 600 K, demonstrated excellent stoichiometry and consistent growth rate (1.4 Å/cycle) on both films. Approximately 13 Å of BN was sufficient to protect ~13 Å of B₂O₃ and ~5 Å of B-Si-oxide from atmospheric moisture and prevent volatile boric acid formation. BN/B₂O₃/Si heterostructures are also stable at high temperatures (>1000 K) commonly used for dopant drive-in and activation. BN shows great promise in preventing upward boron diffusion which causes a loss in the dopant dose concentration in Si. The capping effects of BN were extended to electrochemical battery applications. ALD of BN was achieved on solid Li-garnet electrolytes using halide-free tris(dimethylamino)borane precursor, in conjunction with NH₃ at 723 K. Approximately 3 nm of BN cap successfully inhibited Li₂CO₃ formation, which is detrimental to Li-based electrolytes. BN capped Li-garnets demonstrated ambient stability for at least 2 months of storage in air as determined by XPS. BN also played a crucial role in stabilizing Li anode/electrolyte interface, which drastically reduced interfacial resistance to 18 Ω.cm², improved critical current density and demonstrated excellent capacitance retention of 98% over 100 cycles. This work established that ALD is key to achieving conformal growth of BN as a requirement for Li dendrite suppression, which in turn influences battery life and performance.

With the ever-advancing technology, there is an incessant need for reliable electrochemical energy storage (EES) components that can provide desired energy and power. At the forefront of EES systems are electrochemical capacitors (ECs), also known as supercapacitors that typically have higher power and superior cycle longevity but lower energy densities than their battery counterparts. One of the routes to achieve higher energy density for ECs is using the hybrid EC configuration, which typically utilizes a redox electrode coupled with a counter double-layer type electrode. In this dissertation, both scale-up (coin-cell type) as well as scale-down (on-chip miniaturized) hybrid ECs were designed, constructed and evaluated. The first part of the dissertation comprised material identification, syntheses, and electrochemical analyses. Lithium titanate-anatase titanium oxide (Li4Ti5O12-TiO2) composites were synthesized via electrostatic spray deposition (ESD) and characterized in both half-cell and full-cell assembly against lithium and nanostructured carbon based counter electrodes, respectively. The second redox type material studied for hybrid electrochemical capacitors was ESD derived manganese oxide (MnOx). The MnOx electrodes exhibited a high gravimetric capacitance of 225F g-1 in aqueous media. Further improvement in the rate handling of the MnOx electrodes was achieved by using CNT additives. The MnOx-CNT composites were tested in full-cell assembly against activated carbon counter electrodes and tested for different anode and cathode mass ratios in order to achieve the best energy-power tradeoff, which was the second major goal of the dissertation. The optimized hybrid capacitor was able to deliver a high specific energy density of 30.3 Wh kg-1 and a maximal power density of 4kW kg-1. The last part of the dissertation focused on a scale-down miniaturized hybrid microsupercapacitor; an interdigitated electrode design was adopted in order to shorten the ion-transport pathway, and MnOx and reduced graphene oxide (rGO) were chosen as the redox and double layer components, respectively. The hybrid microsupercapacitor was able to deliver a high stack energy density of 1.02 mWh cm-3 and a maximal stack power density of 3.44 W cm-3, both of which are comparable with thin-film batteries and commercial supercapacitor in terms of volumetric energy and power densities.

Le polymère poreux (PM) associe les avantages double des matériaux poreux et des polymères, ayant la structure unique de pore, la porosité supérieure et la densité inférieure, ce qui possède une valeur d’application importante dans les domaines de l'adsorption, le soutien de catalyseur, le séparateur de batterie, la filtration, etc. Actuellement, il existe plusieurs façons de préparer le PM, comme la méthode de gabarit, la méthode de séparation de phase, la méthode d'imagerie respiratoire, etc. Chacune des méthodes ci-dessus existe ses propres avantages, mais la préparation à grande échelle de PM à structure de pore contrôlable et aux fonctions spécifiques est toujours un objectif à long terme sur le domaine et l'un des principaux objectifs de ce mémoire. La co-extrusion de microcouche est une méthode pour produire de façon efficace et successive des polymères avec des structures de couches alternées, ayant les avantages de haute efficacité et faible coût. Par conséquent, sur les exigences structurelles de PM de l’application spécifique, ce mémoire a conçu le PM avec une structure spécifique et une co-extrusion de microcouche de manière créative combinée avec la méthode traditionnelle de préparation de PM (méthode de gabarit, méthode de séparation de phase), en combinant les avantages des deux méthodes, les PM avec une structure de pore idéale peuvent être préparés en grande quantité et l’on peut également explorer son application dans les séparateurs de batteries au lithium-ion et l'adsorption d'hydrocarbures aromatiques polycycliques.Le plus important, dans la deuxième partie de cet essai, se trouve que la simulation micro-numérique est utilisée pour étudier le transport et le dépôt de particules dans des milieux poreux pour explorer le mécanisme des matériaux poreux dans les domaines de l'adsorption et du séparateur de batterie. Le code de 3D-PTPO (un modèle tridimensionnel de suivi des particules combinant Python® et OpenFOAM®) est utilisé pour étudier le transport et le dépôt de particules colloïdales dans des milieux poreux, l’on adopte trois modèles (colonne, venturi et tube conique) pour représenter différentes formes de matériaux poreux. Les particules sont considérées comme des points matériaux pendant le transport, le volume des particules sera reconstitué et déposé comme partie de la surface du matériau poreux pendant le dépôt, la caractéristique principale de ce code est de considérer l'influence du volume des particules déposées sur la structure des pores, les lignes d'écoulement et le processus du dépôt des autres particules. Les simulations numériques sont d'abord conduites dans des capillaires simples, le travail de chercheurs de Lopez et d’autres est réexaminé en établissant un modèle géométrique tridimensionnel plus réaliste et il explore les mécanismes cachés derrière les règles de transmission et de dépôt. Par la suite, des simulations numériques sont effectuées dans des capillaires convergents-divergents pour étudier la structure des pores et l'effet de nombre Peclet sur le dépôt de particules. Enfin, l’on étudie l’effet double de l'hétérogénéité de surface et de l'hydrodynamique sur le comportement de dépôt de particules
Due to the combination of the advantages of porous media and polymer materials, polymeric porous media possess the properties of controllable porous structure, easily modifiable surface properties, good chemical stability, etc., which make them applicable in a wide range of industrial fields, including adsorption, battery separator, catalyst carrier, filter, energy storage, etc. Although there exist various preparation methods, such as template technique, emulsion method, phase separation method, foaming process, electrospinning, top-down lithographic techniques, breath figure method, etc., the large-scale preparation of polymeric porous media with controllable pore structures and specified functions is still a long-term goal in this field, which is one of the core objectives of this thesis. Therefore, in the first part of the thesis, polymeric porous media are firstly designed based on the specific application requirements. Then the designed polymeric porous media are prepared by the combination of multilayer coextrusion and traditional preparation methods (template technique, phase separation method). This combined preparation method has integrated the advantages of the multilayer coextrusion (continuous process, economic pathway for large-scale fabrication, flexibility of the polymer species, and tunable layer structures) and the template/phase separation method (simple preparation process and tunable pore structure). Afterwards, the applications of the polymeric porous media in polycyclic aromatic hydrocarbons adsorption and lithium-ion battery separator have been investigated.More importantly, in the second part of the thesis, numerical simulations of particle transport and deposition in porous media are carried out to explore the mechanisms that form the theoretical basis for the above applications (adsorption, separation, etc.). Transport and deposition of colloidal particles in porous media are of vital important in other applications such as aquifer remediation, fouling of surfaces, and therapeutic drug delivery. Therefore, it is quite worthy to have a thorough understanding of these processes as well as the dominant mechanisms involved. In this part, the microscale simulations of colloidal particle transport and deposition in porous media are achieved by a novel colloidal particle tracking model, called 3D-PTPO (Three-Dimensional Particle Tracking model by Python® and OpenFOAM®) code. The particles are considered as a mass point during transport in the flow and their volume is reconstructed when they are deposited. The main feature of the code is to take into account the modification of the pore structure and thus the flow streamlines due to deposit. Numerical simulations were firstly carried out in a capillary tube considered as an element of an idealized porous medium composed of capillaries of circular cross sections to revisit the work of Lopez and co-authors by considering a more realistic 3D geometry and also to get the most relevant quantities by capturing the physics underlying the process. Then microscale simulation is approached by representing the elementary pore structure as a capillary tube with converging/diverging geometries (tapered pipe and venturi tube) to explore the influence of the pore geometry and the particle Péclet number (Pe) on particle deposition. Finally, the coupled effects of surface chemical heterogeneity and hydrodynamics on particle deposition in porous media were investigated in a three-dimensional capillary with periodically repeating chemically heterogeneous surfaces

Axial offset anomaly (AOA) in pressurized water reactors (PWR) refers to deviation of the measured neutron flux in the top half of the core from the predicted values. Among other difficulties, AOA reduces the shutdown margin, and may force the plant to reduce power output. AOA is believed to be caused by three related phenomena occurring in the core while operating at full power: sub-cooled nucleate boiling concentrated mainly in the upper half of the core, corrosion product deposition on the cladding surface (crud), and the deposition of boron within the porous crud layer in regions of vigorous sub-cooled boiling. This study replicates the conditions within the PWR primary coolant; specifically, the temperature, pressure, peak surface heat flux, coolant velocity and water chemistry are simulated in order to produce prototypical crud on an electrically heated Zircaloy-4 test element. At the conclusion of each test run, the heated Zircaloy-4 test element is rapidly isolated from the coolant in order to trap any soluble boron species that may be present in the crud layer. The results of this investigation indicate that prototypical crud with significant boron deposition can be produced. The deposited boron compound has been determined to be lithium tetraborate (Li2B4O7). Comparative experiments have been run to determine the effect of coolant pH, concentration and type of additives, and duration of exposure on the thickness of the crud deposit. The data obtained in this investigation can be used to validate mechanistic models for crud deposition and AOA in pressurized water reactors.

Dans la perspective du développement de vitrages électrochromes « en milieu protonique », des films minces électrochromes à coloration anodique, à base d’oxyde de nickel, ont été synthétisés et caractérisés. Afin d’améliorer la durabilité des films minces à base de NiO, trois approches ont été envisagées. (i)Des films d’oxyde de nickel et d’oxyde mixte nickel/lithium, déposés par PLD (Pulsed Laser Deposition). Nous avons étudié l’influence du lithium sur les propriétés physico-chimiques (‘amorphisation..), et les caractéristiques électrochromes (électrochimique-optique) en milieu aqueux KOH 1M. (ii) Des films composites, préparés par voie chimique (solution), constitués d’une phase amorphe (en diffraction des Rayons X), de composition Ti1-xZnxO2-x?x, englobant des cristallites de NiO de ~ 5 nm de diamètre. Les courbes voltampérométriques révèlent que seule la phase NiO est électrochimiquement active, mais la phase amorphe, grâce aux lacunes anioniques neutres, ?x, renforce la tenue mécanique des films déposés sur les substrats FTO/verre. Il s’ensuit que ces films composites sont plus stables au cyclage, en milieu aqueux KOH 1M, que leurs homologues TiO2/NiO. (iii) Des films minces d’oxyde de nickel dopés par du carbone, préparés par une voie sol-gel originale, présentant une remarquable tenue en cyclage (> 25000 cycles en milieu aqueux KOH 1M), jamais observée jusqu’ici pour NiO
Aiming at enhancing the electrochromic properties of NiO thin films, deposited on FTO substrates, we have employed three different approaches. They deal with: 1) lithium doping of NiO, the corresponding thin film-deposition method is PLD (Pulsed Laser Deposition); 2) NiO nanoparticles embedded into zinc doped amorphous titanium oxide matrix, a solution method is used to deposit the corresponding thin films ; 3) Carbon-doped NiO thin films deposited using, a specific sol-gel method. Owing to lithium doping of NiO, we could induce film amorphization, thereby enhancing the film electrochemical-capacity. Most importantly, the adhesion between the film and the FTO substrate was improved leading to enhanced electrochemical cyclability in aqueous KOH electrolyte. We could enhance the electrochromic performances of TiO2/NiO composite thin films by doping TiO2 with Zn2+, forming to a new composite thin film Ti1-xZnxO2-x?x-NiO. Finally we have successfully stabilized the electrochromic properties (durability and optical property) of NiO thin films in aqueous KOH electrolyte, owing to the development of a specific sol-gel method leading to carbon-doped NiO nanoparticles. For the first time 25000 cycles were successfully achieved without significant decrease of the electrochromic performances

Im Hinblick auf das immense Potential von Diamant als Material für die Mikroelektronik wurden im Rahmen dieser Arbeit undotierte und dotierte Diamantfilme mittels chemischer Gasphasenabscheidung auf Silizium präpariert und anschließend auf ihre elektronischen Eigenschaften hin untersucht. Für Letzteres wurde hauptsächlich die Elektronen-Energieverlustspektroskopie in Transmission verwendet. In situ Gasphasendotierung oder Ionenimplantation wurde zur Dotierung der Filme mit Bor, Lithium oder Phosphor eingesetzt. Bei der Ionenimplantation wurde aufgrund der Erzeugung von Strahlenschäden generell eine Erhöhung des sp2-Anteils beobachtet: Letzterer konnte jedoch im Falle der Bordotierung durch eine, den Implantationsprozeß folgende, Hochtemperaturtemperung wieder deutlich vermindert werden. Für die in situ Dotierung mit Bor wurde eine Verringerung des sp2-Gehaltes mit steigender Dotierkonzentration gefunden. Für den Film mit der höchsten Borkonzentration konnte auch die B1s Absorptionskante untersucht werden. Sie gibt Hinweise auf den überwiegenden Einbau der Boratome in einer tetragonalen Orientierung. Das hiermit verbundene Vorhandensein von Akzeptoren führt zu elektronischen Anregungen im Energiebereich der Bandlücke, welche mittels Infrarotspektroskopie und EELS nachgewiesen werden konnten. Aus den EELS Messungen lassen sich Akzeptorkonzentrationen berechnen, welche wiederum den hohen Anteil an tetraedrisch eingebauten Boratomen bestätigen. Desweiteren untersucht wurden, als interessante Materialklasse mit weitreichendem technologischem Potential, undotierte und stickstoffdotierte, diamantartige amorphe Kohlenstoffilme und hierbei insbesondere die Abhängigkeit der elektronischen und optischen Eigenschaften von der Ionenenergie und dem Stickstoffpartialdruck während der Filmpräparation. Die Plasmonenergien, Massendichten, sp3-Anteile und die optischen Bandlücken der Filme wurden quantitativ bestimmt, wobei das jeweilige Maximum bei einer Ionenenergie von 100 eV gefunden wurde. Alle eben genannten Größen verringern sich kontinuierlich mit zunehmendem Stickstoffanteil. Eine Kramers-Kronig Analyse der Verlustspektren gibt Zugriff auf den Real- und Imaginärteil der dielektrischen Funktion und damit auf das Spektrum der Einteilchenanregungen. Die Hybridisierung der Kohlenstoff- und der Stickstoffatome wurde detailliert aus den jeweiligen 1s Absorptionskanten bestimmt. Weiterhin wurde Diamant als Modellsystem eines Festkörpers mit rein kovalenten Bindungen untersucht, insbesondere die Verlustfunktion von Diamant entlang mehrerer Hochsymmetriekristallrichtungen über einen großen Energie- und Impulsbereich. Aus den EELS Messungen erschließt sich unmittelbar die stark anisotrope Plasmonendispersion von Diamant. Aus dem Vergleich der experimentellen Spektren mit ab initio LDA Rechnungen, die sowohl Kristallokalfeldeffekte als auch Austausch- und Korrelationseffekte beinhalten, lassen sich direkt Rückschlüsse auf den Einfluß der verschiedenen Effekte ziehen. Schon im optischen Limit, aber umso mehr mit steigendem Impulsübertrag q, wird eine Überlagerung der kollektiven Plasmonanregung mit Einteilchenanregungen im Energiebereich des Plasmons beobachtet, woraus eine Kopplung zwischen beiden Arten von Anregungen resultiert. Abgesehen vom deutlichen Einfluß der Bandstruktur auf die Plasmonendispersion läßt die überaus inhomogene Elektronenverteilung von Diamant auf nicht zuvernachlässigende Kristallokalfeldeffekte schließen. Der Vergleich zwischen experimentellen und berechneten Spektren zeigt deutlich, wie die Kristallokalfeldeffekte in der Tat mit steigendem Impulsübertrag an Gewicht zunehmen und die Struktur der Verlustfunktion mitbestimmen
In the context of the immense potential of diamond as a material for use in the microelectronics industry, in this thesis pristine and doped diamond films have been deposited on silicon using chemical vapour deposition. Subsequently their electronic properties have been investigated using mainly electron energy-loss spectroscopy. Doping of the films with boron, lithium or phosphorous was carried out either via in-situ gas phase doping during film growth or using ion implantation. Upon ion implantation an increase of the carbon content with sp2 hybridisation has generally been found due to ion beam induced damage. In the case of boron doping it was possible to significantly reduce this sp2-contribution using a high temperature anneal. For the in-situ doping with boron, upon increasing doping concentration a decrease of the sp2-contribution was found. For the sample with the highest boron content the boron 1s absorption edge could also be investigated, providing evidence for the preferential incorporation of the boron atoms into tetrahedrally co-ordinated sites. This boron incorporation leads to the existence of electronic excitations in the energy range of the band gap, which could be observed using both infrared and electron energy-loss spectroscopy. From the electron energy-loss measurements it was possible to calculate acceptor concentrations which were consistent with the large amount of tetrahedrally co-ordinated boron atoms. A second theme in this thesis involved the study of pristine and nitrogen doped diamond-like amorphous carbon films, which are an interesting material class with far-reaching technological potential. Here the focus of the research concerned the dependency of the electronic and optical properties of the films upon the ion energy and the nitrogen partial pressure applied during the film preparation. The plasmon energies, mass densities, sp3 contribution and the optical band gaps of the samples were determined quantitatively, whereby the maximum in all these quantities was found to occur for ion energies of 100 eV. Furthermore, all of these characteristics were found to decrease continually with increasing nitrogen content. A Kramers-Kronig analysis of the loss spectra enabled the derivation of the real and imaginary parts of the dielectric function and with this of the complete spectrum of single particle excitations. The hybridization between the carbon and nitrogen atoms was also studied in detail from the analysis of the respective 1s absorption edges. Furthermore this thesis deals with the investigation of diamond as a model system for solids with pure covalent bonds. In particular, the loss function of diamond was measured along different high symmetry directions over a wide range of energy and momentum. Firstly, the EELS measurements showed directly the strongly anisotropic nature of the plasmon dispersion in diamond. Secondly, by the comparison of the experimental spectra with ab initio LDA-based calculations that include crystal local field effects as well as exchange and correlation contributions, conclusions can be drawn as to the influence of these quantities. In the optical limit, but even more so with increasing momentum transfer q, a superposition of the collective plasmon excitation and the single particle excitations in the energy range of the plasmon is observed. This energetic proximity results in a coupling between both types of excitations. Apart from the distinct influence of the bandstructure on the plasmon dispersion, the considerably inhomogeneous electron distribution of diamond would lead one to expect significant crystal local field effects in this system. The comparison between the experimental and the calculated spectra shows explicitly that the crystal local field effects increase with increasing momentum transfer and play an important role in defining the structure of the loss function

Afin d'approfondir la compréhension des mécanismes de vieillissement des batteries Li-ion, des analyses post-mortem ont été effectuées sur des cellules commerciales Li-ion C/NMC. Ces autopsies ont révélé des dégradations inattendues qui remettent en question les connaissances actuelles sur les mécanismes de vieillissement de ces cellules. Ainsi, il semble que la réaction parasite des dépôts de Li métallique sur l'électrode en graphite, actuellement associée dans la littérature à des charges à basses températures et / ou à courants élevés, aurait diverses origines selon la chimie et les conditions d'utilisation de la batterie. Dans ce travail de thèse, des dépôts locaux de Li métallique ont été observés sur des cellules vieillies en calendaire à haute température. Paradoxalement, dans des conditions de cyclage à basse température, ce dépôt de Li métallique a résulté de la perte de porosité au niveau de l’électrode négative. Par ailleurs, un modèle de vieillissement semi-empirique, prenant compte les pertes en cyclage ainsi que celles causées par la croissance de la SEI et la polymérisation du biphényl, est proposé. Pour finir, une méthode d'identification des modes de dégradation grâce à des mesures de capacité incrémentale a été entreprise, sur la base du décalage des potentiels de chacune des électrodes
In order to deepen the understanding of the aging mechanisms of Li-ion batteries, post-mortem investigations were performed on C/NMC Li-ion commercial cells. These autopsies revealed unexpected degradations that question current knowledge about the aging mechanisms of these cells. Thus, it appears that the parasitic reaction of Li metal depositions on the graphite electrode, nowadays associated in the literature with charging at low temperature and / or high C-rates, would have various origins depending on the chemistry and conditions of use of the battery. In this thesis work, local Li deposits were observed on cells aged in calendar at high temperatures, due to the apparition of dry areas. Paradoxically, under low temperature cycling conditions, this Li resulted from anode porosity hindrance. Besides, a semi-empirical aging model, taking into account cycling losses as well as those caused by the SEI growth and the biphenyl polymerization, is proposed. Finally, a method of identifying degradation modes using incremental capacity measurements has been undertaken, based on the potential shifts of each of the electrodes

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.

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)

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)

碩士
國立中興大學
材料科學與工程學系所
100
In order to get anode materials of high capacity, high potential and fast charge and discharge rate, coating high conductivity metals in mesophase carbon micro bead (MCMB) is an efficient way. In this study, the electrochemical deposition of nickel on MCMB, has been successfully carried out to enhance the performance of anode material in lithium ion battery. The electrochemical reaction through was analyzed by polarization curves. Ni/MCMB powders showed the Ni/C structures by TEM, XRD and SEM/EDS analysis. The deposition conditions in 0.3 M and 0.5 M NiCl2 solutions at 14V and 0.7A showed the more uniform dispersion and the finer particles. Coin cells composed of such Ni coated carbon powders revealed 71~135% more coating than the uncoated carbon powders at 1C rate, resulting from the interfacial resistance of Ni/MCMB 65~85% lower than MCMB.

碩士
中興大學
材料工程學系所
95
In this study, Sn and Sn/Li2O film has been successfully deposited on the stainless steel substrate in SnCl2 and SnCl2、LiNO3 mixed solutions by electrochemical method. The microstructure, morphology, and compositions of the materials were investigated by XRD, SEM/EDS, and ESCA. In addition, the electrochemical properties were investigated by CV analysis and charge/discharge cycle tests. Charge/discharge cycle tests demonstrated that Sn/Li2O film showed better cycle performance than pure Sn at the voltage range was 0.02 to 0.9 V and current density of 800 μA/cm2. The capacity of Sn/Li2O film by electrochemical method was still found 660 mAh/g after 50 cycle, and much higher than the capacity of the commercial graphite electrodes (372 mAh/g).

碩士
國立中興大學
材料科學與工程學系
96
The preparation of TiO2 thin film on platinum was carried out for anodes in thin film lithium batteries. In order to optimize the best electrochemical performance, the specimens were deposited for 5, 10 and 20 min and further annealed at 350 and 500℃. The surface morphology of film deposited for 5 minutes was more uniform than the others. The TiO2 coating film consists of nano-sized particles observed by EF-SEM were 10-20 nm, consistent with XRD analyses. Cyclic voltammetry (CV) measurements show oxidation and reduction peaks at 2.20 and 1.61 V, respectively. The discharge and charge plateus were found at 1.75 and 1.98 V vs. Li+/Li by charge/discharge tests. When increasing current density, the specific capacity was dramatically decreased. It was suggested that the diffusion flux of Li+ insertion/extraction into/from TiO2 controlled the reaction rate at higher current density. Finally, the capacity was proportional to the diffusion length. Although the capacity of various prepared films in thickness were approaching one another after 50 cycles due to diffusion along crack surfaces, the more uniform EDT350-1T specimen in the thickness of 0.3 μm was better than the others when it was applied in thin film lithium ion batteries.

Tin dioxide (SnO2) is considered one of the most promising anode materials for Lithium ion batteries (LIBs), due to its large theoretical capacity and natural abundance. However, its low electronic/ionic conductivities, large volume change during lithiation/delithiation and agglomeration prevent it from further commercial applications. In this thesis, we investigate modified SnO2 as a high energy density anode material for LIBs. Specifically two approaches are presented to improve battery performances. Firstly, SnO2 electrochemical performances were improved by surface modification using Atomic Layer Deposition (ALD). Ultrathin Al2O3 or HfO2 were coated on SnO2 electrodes. It was found that electrochemical performances had been enhanced after ALD deposition. In a second approach, we implemented a layer-by-layer (LBL) assembled graphene/carbon-coated hollow SnO2 spheres as anode material for LIBs. Our results indicated that the LBL assembled electrodes had high reversible lithium storage capacities even at high current densities. These superior electrochemical performances are attributed to the enhanced electronic conductivity and effective lithium diffusion, because of the interconnected graphene/carbon networks among nanoparticles of the hollow SnO2 spheres.

碩士
國立中興大學
材料科學與工程學系所
98
In this study, the preparation of LiV3O8 thin film on stainless steel substrate was carried out in VOSO4 and LiNO3 mixed solution by using cathodic electrochemical synthesis for cathodes in thin film lithium batteries. Through cathodic polarization tests, five major regions were verified: (I) Reduction of the passivation (~0.23 to -0.02V); (II) VO2++ 2H+ +e−→V3++ H2O; V3++ e− →V2+ (-0.02 to -0.38V); (III) O2 +4H+ +2e−→2H2O (-0.38 to -0.56V); (IV) LixVO(H2O)2+x2+ + (2+x)e−→ LixVO(OH)2+x + (1+x/2)H2↑ (-0.56 to -1.07V); (V) 2H2O+2e−→ 2OH−+H2 (-1.07 to -2V). The coated specimens prepared at region IV were characterized by inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric differential thermal analysis (TG-DTA), field emission scanning electron microscopy (FE-SEM), cyclic voltammetry (CV), and charge/discharge tests. It was found that the as-deposited film was amorphous, dehydrated into Li2O and VO(OH)2 around 111.3℃, further condensed and oxidized into Li0.3V2O5 and Li2O approximate 273.4℃, and finally transformed into LiV3O8 monoclinic structure with the presence of the residual Li2O at 400℃. 　　Cyclic voltammetry (CV) measurements revealed the oxidation peaks at 2.43V, 2.71V, and 2.88V, and the reduction peaks at 2.24 V, 2.52V, and 2.77 V (vs. Li/Li+). Charge/discharge cycle tests demonstrated that LiV3O8 annealed at 400℃ revealed better cycle performance than that at 300℃. Annealing at 400℃possessed the excellent discharge capacity of 293.6 mAh/g after 50 cycles.

碩士
國立成功大學
材料科學及工程學系
102
Since titanium ions show multi-valent states, the conductivity of lithium titanate may highly depend upon the addition of aliovalent dopant or surrounding atmosphere. To improve the electrical conductivity, introduce the Ti3+ through being calcined in reducing atmosphere. To improve the behavior of lithium ion diffusion, lattice expansed through the ionic radius of Nb5+ or Ti3+. The electrical conductivity of Li4Ti5O12 under reducing synthesis was improved by two orders of magnitude.The capacity and rate capability would be improved when exposed at low oxygen partial pressure. Li4Ti5O12 thin films were deposited on a Pt/ Ti/SiO2/Si(100) substrate via radio frequency (rf) sputter in a mixture of oxygen and argon gases. The crystallinity of Li4Ti5O12 phase increased with the annealing temperature increasing from 500°C to 700°C. The variation was attributed to some Li escaped from thin films. The capacity of Li4Ti5O12 thin film was higher than the theoretical capacity (175 mAhg-1). It might attribute to amorphous TiO2 in the Li4Ti5O12 thin films. Li ions may be expected to react with H2O to Li2O, which decreased the capacity.

碩士
國立中興大學
材料科學與工程學系所
102
The light, thin, short and small devices with environmental protection and safety should be demanded for 3C products in the 21st century. The thin film lithium batteries will play an important role on developing low-cost and high voltage applications. In this study, we try to find a novel process for preparing LiCoxMn2-xO4 coating on stainless steel by electrochemical synthesis in 0.1 M LiNO3 and 0.01 M Mn(NO3)2 mixture and then in 0.1 M LiNO3, 0.01 M Co(NO3)2 mixture aqueous solutions, respectively, and subsequent annealing. The coated specimen were characterized by XRD, TG-DTA, FE-SEM, cyclic voltammetry (CV) tests. The as-coating is composed of hydroxides of Li+, Mn2+ and Co2+ transformed into LiCoxMn2-XO4 after annealed at 300 ~ 500℃ for 3 h, but gradually decomposed into Li2O, Co3O4 and Mn2O3 at 550℃, also accompanied with the variation of surface morphology. The oxidation peaks at 2.8, 3.72 and 4.31 V (vs. Sn/Li2O anode) and reduction peaks at 2.66, 3.93 and 4.2 V (vs. Sn/Li2O anode) result from the overall cell reaction for the Li extraction/insertion reaction from/in the LiCoxMn2-xO4 with spinel structure. The peak current density of coated specimen annealed at 500℃ for 3 h is the highest around 4.2 V due to the higher crystallinity. However, the peak around 4.2 and 3.9 V for specimen annealed at 550℃almost disappear, due to the decomposition. Therefore, the annealing temperature at 500℃ is suggested for the processing.

碩士
國立高雄應用科技大學
化學工程與材料工程系
98
In this research, the nanostructured nickel oxide electrodes were deposited onto the stainless steel (SS) substrate by anodic deposition for lithium-ion battery application. In order to improve the electrochemical performance of the nickel oxide electrode, monodispersed polystyrene (PS) spheres were used as a template in anodic deposition of nickel oxide. The PS template was fabricated by electrophoretic deposition (EPD). After removal of PS, the electrode was annealed at 400oC for 1 h to form macroporous NiO electrode (cubic NiO, deduced from X-ray diffraction). The electrochemical properties of the macroporous NiO electrode toward lithium were investigated. Surface morphology of the deposited NiO electrodes is platelet-like structure observed from SEM (scanning electron microscope). The pores in the electrode deposited at a high current density of 0.25 mA cm-2 are smaller than that of deposited at a lower current density of 0.05 mA cm-2. However, the surface morphology of nickel oxide electrode can be severely modified after charge and discharge cycling. The porous structure of the electrode deposited at 0.25 mA cm-2 remains unchanged, while that of deposited at 0.05 mA cm-2 is attenuated significantly. Galvanostatic charge/discharge curve of nickel oxide films (1 C current) indicates that the reversible capacity of electrodes deposited at 0.05 and 0.25 mA cm−2 are 1221 and 1294 mAh g-1, respectively. At a higher current charge/discharge (15 C), the reversible capacities of electrodes deposited at 0.05 and 0.25 mA cm-2 are 383 and 487 mAh g-1, respectively. Moreover, the nickel oxide electrode with macropores deposited at a current density of 0.25 mA cm−2 exhibits excellent electrochemical behavior toward lithium, especially during high-rate charging and discharging circumstances. The reversible capacity of electrode is increased by 15.6 % at 1 C rate, and 87 % at 15 C rate compared with the bare nickel oxide electrode (without open macropores). Therefore, we can conclude that a porous film structure with macropores is beneficial to the electrolyte transport, leading to an increase in effective specific surface areas for electrochemical reaction. As a result, the electrochemical performance of the nickel oxide electrode with open macropores is better than that of the bare nickel oxide electrode. Keywords: Anodic deposition; Nickel oxide; Lithium-ion batteries; Template; Macroporous structure.

Al based alloy powders (Al₈₅Ni₅Y₆Co₂Fe₂) are produced by spray atomization method. High energy ball milling is done to modify the surface topology and particle size for better electrochemical performance. X ray diffraction (XRD), differential scanning calorimeter (DSC), scanning electron microscope (SEM) and transmission electron microscope (TEM) were conducted to characterize the microstructure of the alloys after ball milling. It is found that 5 hours ball milling gives the minimum crystallization and structure change. Thin film sample is also deposited on stainless steel substrate by pulsed laser deposition (PLD) method for electrochemical test. The capacity and reversibility for different samples are compared and discussed. A capacity of 200mAh/g is obtained for the battery with thin film sample as anode and a capacity of 140mAh/g is obtained for that with electrode from powder sample. Both of the batteries give up to 94% capacity retention after 20 cycles.
Singapore-MIT Alliance (SMA)

In the last few years, with the advance of electrical vehicles and number of devices needing safe batteries especially in the medical field, a more efficient way to store energy is necessary. Despite the fact that conventional lithium batteries present high conductivity values, they do not exhibit enough charging/discharging speed and also include dangerous components to health. To overcome those challenges, thin film solid state batteries are considered a promising candidate. However, this all-solid-state battery concept exhibits too low energy density, pushing the technology towards 3D structures and developing 3D all-solid-state lithium-ion batteries (ASSBs). This thesis describes the development of a pinhole-free solid-state lithium-ion electrolyte through spatial, to pave the way for cost effective and scalable 3D ASSBs. The produced films are thoroughly characterized to find the relation between deposition parameters and film quality in terms of thickness, reproducibility, uniformity, composition and conductivity. The obtained LiPON, being deposited with the fast spatial ALD process, offers ionic conductivity of 1.55 (± 0.14) x 10-7 S/cm and electronic conductivity of 1.86 x 10-13 S/cm, being a promising solid electrolyte layer for next generation lithium-ion batteries.

碩士
國立清華大學
材料科學工程學系
104
The main objective of this dissertation is to improve the electrochemical performances of ZnCo2O4 (ZCO) Li-ion anode material by nitrogen-doping and carbon deposition. As for nitrogen doping, two rapid methods, including hydrothermal to treat powder and atmospheric pressure plasma jet (APPJ) to modify the electrode, were used to dope nitrogen in the ZCO anode material. Via hydrothermal method, nitrogen was doped in the ZCO spinel lattice, while APPJ mainly activated and modified the electrode surface binding with the dangling bond. N-doped compounds were formed on the electrodes by hydrothermal and APP methods. The uniformity, chemical composition, and diffraction patterns were examined by electron probe microanalyzer (EPMA), X-ray photoelectron spectroscopy (XPS) and X-ray diffractometer (XRD). Nitrogen doping effectively improved electrochemical performance in cycling retention and the capacity at a current density of 1C. This study provides a rapid and inexpensive nitrogen doping processes to efficiently promote the electrochemical performance in ZCO anode. In addition, a special set-up of atmospheric pressure plasma jet generator was applied to deposit carbon on the electrode. Significant amounts of C(I) and C2 clusters were discovered using optical emission spectroscopy. After adding N2, the CN species appeared in the plasma, owing to C and N2 reaction during the plasma generation. The results from the field emission scanning electron microscope (FESEM) and X-ray photoelectron microscopy (XPS) reveal the change in surface morphology and chemical bonding by plasma treatment. After 20 times of Ar+N2 plasma treatment, a significant increment in cycling stability under 1000 mA/g was evident.

碩士
國立臺灣科技大學
材料科學與工程系
106
Recently, the study of two-dimensional (2D) nanostructure has been developed rapidly due to it exhibits many unique physical and chemical properties when compared to their bulk counterparts. In this work, the first-ever study of nickel monoselenide (NiSe) materials used the chemical vapor deposition (CVD) method to synthesize the hexagonal nanoflake-based of NiSe with lateral size of 12 μm on the SiO2/Si substrate. The electrical properties measured that the resistivity of parallel and vertical the nanoflake were resulted in 2.79 x10 -5(Ω·m) and 4.38 x10 2 (Ω·m), respectively. As a result, a large resistivity anisotropy ratio about 1.4 x 10 7 was revealed. Moreover, the NiSe nanoflakes were also taken as anodes for lithium-ion batteries (LIBs) and sodium-ion batteries (NIBs), the initial discharge capacities of the NiSe nanoflakes with current density of 100 mA g−1 for LIBs and NIBs are 522.2 and 343.8 mAh g−1, respectively. During the cycle performance measurements for LIBs, the discharge capacity retained at 346.3 mAh g-1 on the 50th cycle which exhibits NiSe nanoflake is a promising candidate for anode material of LIBs and NIBs.

碩士
國立成功大學
材料科學及工程學系
102
InN nanowires with random orientations are grown densely on Au/In-coated Si (111) and stainless steel substrates by a modified thermal chemical vapor deposition method. Scanning electron microscopy images show that the as-grown nanowires are characterized by either parallel or sawtooth sides. High resolution transmission electron microscopy images and selected area electron diffraction patterns reveal that both types of nanowires contain Au catalytic particles on tops and the growth direction is along the [0001] and [101 ̅0] axis for sawtooth and parallel-sided nanowires, respectively. Through e-beam lithography, resistivity of single nanowires taken by four-point probe method all falls on the order of 10-4 Ω•cm, demonstrating to own great conductivity. For the application in lithium ion battery, coin cells are assembled using the InN nanowires grown on stainless substrate as negative electrodes and cycle performance testing is performed. The capacity could reach 886 mAh/g, which is more than two times of the commercial carbon materials. InN nanowires are testified to be promising in battery applications.

碩士
國立臺灣科技大學
化學工程系
105
Lithium-rich cathode materials are drawing high attention recently as next generation cathode materials for Li-ion battery due to its high operating voltage and high capacity ~270 mAhg-1. However, its poor electronic conductivity, rapid voltage fading during cycles and interphase instability still hinder its practical applications. This study consists of two parts: first, to deposit carbon on Li rich powders by chemical vapor deposition (CVD) with dilute ethylene and argon for enhancing electronic conductivity of powder. Second, to form a carbonaceous layer (Artificial SEI layer) covering Li-rich particles by CVD with a mixture of gases of dilute hydrogen, carbon dioxide and argon with the aim of enriching high stability and interface stability. The effects of the combination and applied sequence of two aforementioned approaches on the properties and electrochemical performance of cathode powders are also studied and compared against the individually treated and pristine materials. In the results and discussion part, the modified powders are examined by bulk/surface structure and surface composition separately. Finally, it is summarized by enhanced electrochemical properties without impairing bulk structure. The most potential modified sample, C1S4, was coated by CVD carbon deposition first, followed by the coverage of 3 nm carbonaceous layer and Li2CO3 growth on the Li-rich powder surface. It is also to note that a spinel-like structure was also formed in the depth of 5 nm. Overall, the C1S4 modified sample delivered a discharging capacity as high as 80 mAhg-1 at 3C and high retention of 85.7% after 110 cycling test, which surpassed the pristine powder, 5.4% higher. This research sheds light on carbon coating and carbonaceous layer covering as an artificial SEI layer onto Li-rich cathode material with novel combination of reducing gases via CVD. The improved material performance and the process features make this proposed surface modification method suitable for production in near future. Keywords: Lithium-rich, cathode material, surface modification, carbon coating, solid electrolyte interphase, interphase stability, electronic conductivity.

碩士
國立清華大學
材料科學工程學系
104
The increasing demand for advanced electronic devices and energy storage have stimulated significant interests in lithium ion battery development. Li based batteries are one of the most promising energy storage systems which as they are light-weight and energy-delivery efficient. Compared to the common graphite-anode system, Si is known to have highest theoretical specific capacitance making Si the most promising candidate for the next-generation anode materials for lithium batteries. However, large volume expansion and serious material pulverization after cycling lead to poor life times, and is the main stumbling block toward their commercialization. In this research, glancing angle deposition (GLAD) technique is utilized to deposit uniform and aligned helix Si nanostructures. By varying the rotation angle during GLAD, various helix Si nanostructures with differing porosities were deposited. With increasing numbers of rotation (3 to 48) the double layer capacitance, related to the surface area, increased to from 0.112 to 0.208 F/cm3. Additionally, the areal spacing also increases and results in occupation of Si nanostructure decreased from 77.5% to 73.77%. As a result, 48 cycle helix Si anode shows the best electrochemical performance with a volumetric specific capacity 846.55 mAh/cm3. Following a 100 cycle test, the anode is able to maintain 70% of its original volumetric specific capacity. However, the low conductivity of intrinsic silicon makes charge transfer of the electrons slow and also gives rise to incomplete alloying reactions with Li ions. To overcome this we annealed our anode with the aim of forming copper silicide, utilising the underlying copper substrate as a source. In doing so, the volumetric specific capacity was increased to 1706.68 mAh/cm3, using a 100 cycle test at charge/discharge rates as high as 0.25 C. Throughout this work detailed analysis was carried out, including X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), I-V characteristics (I-V) Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV), providing an understanding of our results and possibilities for future work. Furthermore, we believe that the adequate porosity and lower conductivity helps to minimize the enormous stress within the film structure by proving enough space for volume expansion, leading to a longer life time and better charge transfer and electrochemical performance.

In this thesis, the results pertaining to various investigations carried out on Triglycine sulphate (TGS) single crystals, polyvinylidene fluoride (PVDF) films, lithium tantalate (LT)/PVDF nanocomposites and LT thin films are presented with emphasis on the characteristics that are crucial for their use in pyroelectric sensors. TGS single crystals (size 68 x 45 x 42 mm3), which have high pyroelectric coefficients, were grown by slow cooling method using newly designed platform technique based crystal growth work stations. The problem of slow growth rate along c-direction was overcome by placing (010) oriented seeds on the platform. The grown TGS crystals were used for the fabrication of the laser energy meter and temperature sensor. One drawback of TGS is its low Curie temperature (490C). As a consequence when the operating temperature approaches the Curie temperature, the crystals start depolarizing owing to the movement of domains. As a result the linearity of the devices gets affected and restricts the use of TGS. Therefore pyroelectric materials possessing higher Curie temperatures and larger pyroelectric coefficients than that of TGS are desirable. LT in single crystalline form having Curie temperature of ≈6000C has already been in use for pyroelectric device applications. However, growing stoichiometric LT single crystal is very difficult. On the other hand PVDF polymer films (Tc≈1800C) have low pyrolectric coefficients and difficult to pole electrically. Therefore efforts were made to prepare LT/PVDF nanocrystal composites to increase the pyroelectric coefficient of PVDF and to reduce the poling field. Nanoparticles of LT were prepared using sol-gel route. Spherical nanoparticles of size 20-40nm were prepared from sol by adding oleic acid to it. These nanoparticles were characterized using XRD, TEM, DSC and Raman spectroscopy. PVDF films with large percentage of β-phase (ferroelectric phase) were fabricated from solutions prepared using dimethylsulphoxide (DMSO) solvent. PVDF films (30µm thick), embedded with 20-40nm sized nanocrystallites of LT were fabricated to utilize them for pyroelectric sensor applications. The ferroelectric and pyrolectric properties of nano composite films were studied for sensor applications point of view. As a replacement for the single crystals of LT in pyroelectric sensors, investigations were carried out on oriented LT thin films. The studies on LT thin films yielded promising results which could be exploited for pyroelectric sensor applications.

White light emitting diodes (LED) have drawn increasing attention due to their low energy consumption, high efficiency and potential to become primary lighting source by replacing conventional light sources. White light emission is usually generated either by coating yellow phosphor on a blue-LED or blending red, green and blue phosphor in an appropriate ratio. Maintaining appropriate proportions of individual components in the blend is difficult and the major demerit of such system is the overall self-absorption, which changes the solution concentration. This results in uncontrolled changes in the whiteness of the emitted light. Zinc Oxide (ZnO), a wide bandgap semiconductor with a large exciton binding energy at room temperature has been recognized as a promising material for ultraviolet LEDs and laser diodes. Tuning of structural, optical and electrical properties of ZnO thin films by different dopants (Lithium, Indium and Gallium) is dealt in this thesis. The achievement of white light emission from a semiconducting material without using phosphors offers an inexpensive fabrication technology, good luminescence, low turn-on voltage and high efficiency. The present work is organized chapter wise, which has 8 chapters including the summary and future work. Chapter 1: Gives a brief discussion on the overview of ZnO as an optoelectronic material, crystal structure of semiconductor ZnO, the effect of doping, optical properties and its possible applications in optoelectronic devices. Chapter 2: Deals with various deposition techniques used in the present study, includes pulsed laser deposition and thermal evaporation. The experimental set up details and the deposition procedures are described in detail. A brief note on the structural characterization equipments, namely X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and the optical characterization techniques namely Raman spectroscopy, transmission spectroscopy and photoluminescence (PL) spectroscopy is presented. The electrical properties of the films were studied by current- voltage, capacitance - voltage and Hall Effect measurements and the experimental details are discussed. Chapter 3: High quality ZnO/Si heterojunctions fabricated by growing ZnO thin films on p-type Si (100) substrate by pulsed laser deposition without using buffer layers are discussed in this chapter. The crystallinity of the heterojunction was analyzed by high resolution X-ray diffraction and atomic force microscopy. The optical quality of the film was analyzed by room temperature (RT) photoluminescence measurements. The high intense band to band emission confirmed the high quality of the ZnO thin films on Si. The electrical properties of the junction were studied by temperature dependent resistivity, current- voltage measurements and RT capacitance-voltage (C-V) analysis. ZnO thin film showed the lowest resistivity of 6.4x10-3 Ω.cm, mobility of 7 cm2/V.sec and charge carrier concentration of 1.58x1019cm-3 at RT. The charge carrier concentration and the barrier height (BH) were calculated to be 9.7x1019cm-3 and 0.6 eV respectively from the C-V plot. The BH and ideality factor, calculated by using the thermionic emission (TE) model were found to be highly temperature dependent. We observed a much lower value in Richardson constant, 5.19x10-7 A/cm2K2 than the theoretical value (32 A/cm2K2) for ZnO. This analysis revealed the existence of a Gaussian distribution (GD) with a standard deviation of σ2=0.035 V. By implementing GD to the TE, the values of BH and Richardson constant were obtained as 1.3 eV and 39.97 A/cm2K2 respectively from the modified Richardson plot. The obtained Richardson constant value is close to the theoretical value for n-ZnO. These high quality heterojunctions can be used for solar cell applications. Chapter 4: This chapter describes the structural and optical properties of Li doped ZnO thin films and the properties of ZnO/Li doped ZnO multilayered thin film structures. Thin films of ZnO, Li doped ZnO (ZLO) and multilayer of ZnO and ZLO (ZnO/ZLO) were grown on silicon and Corning glass substrates by pulsed laser deposition technique. Single phase formation and the crystalline qualities of the films were analyzed by X-ray diffraction and Li composition in the film was investigated to be 15 Wt % by X-ray photoelectron spectroscopy. Raman spectrum reveals the hexagonal wurtzite structure of ZnO, ZLO and ZnO/ZLO multilayer, confirms the single phase formation. Films grown on Corning glass show more than 80 % transmittance in the visible region and the optical band gaps were calculated to be 3.245, 3.26 and 3.22 eV for ZnO, ZLO and ZnO/ZLO respectively. An efficient blue emission was observed in all films that were grown on silicon (100) substrate by photoluminescence (PL). PL measurements at different temperatures reveal that the PL emission intensity of ZnO/ZLO multilayer was weakly dependent on temperature as compared to the single layers of ZnO and ZLO and the wavelength of emission was independent of temperature. Our results indicate that ZnO/ZLO multilayer can be used for the fabrication of blue light emitting diodes. Chapter 5: This chapter is divided in to two parts. The fabrication and characterization of In doped ZnO thin films grown on Corning glass substrate is discussed in the first section. Zinc Oxide (ZnO) and indium doped ZnO (IZO) thin films with different indium compositions were grown by pulsed laser deposition technique. The effect of indium concentration on the structural, morphological, optical and electrical properties of the film was studied. The films were oriented along the c-direction with wurtzite structure and are highly transparent with an average transmittance of more than 80 % in the visible wavelength region. The energy band gap was found to be decreasing with increasing indium concentration. High transparency makes the films useful as optical windows while the high band gap values support the idea that the film could be a good candidate for optoelectronic devices. The value of resistivity observed to be decreasing initially with doping concentration and subsequently increasing. The XPS and Raman spectrum confirm the presence of indium in indium doped ZnO thin films. The photoluminescence spectrum showed a tunable red light emission with different In concentrations. Undoped and In doped ZnO (IZO) thin films were grown on Pt coated silicon substrates (Pt/Si) to fabricate Pt/ZnO:Inx Schottky contacts (SC) is discussed in the second section. The SCs were investigated by conventional two probe current-voltage (I-V) measurement and by the I-V spectroscopy of conductive atomic force microscopy (C-AFM). X-ray diffraction technique was used to examine the thin film quality. Changes in various parameters like Schottky barrier height (SBH) and ideality factor (IF) as a function of temperature were presented. The estimated BH was found to be increasing and the IF was found to be decreasing with increase in temperature. The variation of SBH and IF with temperature has been explained by considering the lateral inhomogeneities in nanometer scale lengths at metal–semiconductor (MS) interface. The inhomogeneities of SBH in nanometer scale length were confirmed by C-AFM. The SBH and IF estimated from I-V spectroscopy of C-AFM showed large deviation from the conventional two probe I-V measurements. IZO thin films showed a decrease in SBH, lower turn on voltage and an enhancement in forward current with increase in In concentration. Chapter 6: In this chapter the properties of Ga doped ZnO thin films with different Ga concentrations along with undoped ZnO as a reference is discussed. Undoped and Ga doped ZnO thin films with different Ga concentrations were grown on Corning glass substrates by PLD. The structural, optical and electrical properties of Ga doped ZnO thin films are discussed. The XRD, XPS and Raman spectrum reveal the phase formation and successful doping of Ga on ZnO. All the films show good transmittance in the visible region and the photoluminescence of Ga doped ZnO showed a stable emission in the blue- green region. The resistivity of Ga doped ZnO thin films was found to be first decreasing and then increasing with increase in Ga concentrations. Chapter 7: The effect of co-doping to ZnO on the structural, optical and electrical properties was described in this chapter. Ga and In co-doped ZnO (GIZO) thin films together with ZnO, In doped ZnO (IZO), Ga doped ZnO (GZO), IZO/GZO multilayer for comparison, were grown on Corning glass and boron doped Si substrates by PLD. GIZO showed better structural, optical and electrical properties compared with other thin films. The Photoluminescence spectra of GIZO showed a strong white light emission and the current-voltage characteristics showed relatively lower turn on voltage and larger forward current. The CIE co-ordinates for GIZO were observed to be (0.31, 0.33) with a CCT of 6650 K, indicating a cool white light and established a possibility of white light emitting diodes. Finally the chapter 8 presents the summary derived out of the work and a few suggestions on future work.

The magnificent development of on-board solutions for electronics has resulted in the race towards scaling down of autonomous micro-power sources. In order to maintain the reliability of miniaturized devices and to reduce the power dissipation in high density memories like CMOS RAM, localized power for such systems is highly desirable. Therefore these micro-power sources need to be integrated in to the electronic chip level, which paved the way for the research and development of rechargeable thin film batteries (TFB). A Thin film battery is defined as a solid-state electrochemical source fabricated on the same scale as and using the same type of processing techniques used in microelectronics. Various aspects of deposition and characterization of LiCoO2/LiPON/Sn thin film battery are investigated in this thesis. Prior to the fabrication of thin film battery, individual thin film layers of cathode-LiCoO2, electrolyte-LiPON and anode-Sn were optimized separately for their best electrochemical performance. Studies performed on cathode layer include theoretical and experimental aspects of deposition of electrochemically active LiCoO2 thin films. Mathematical simulation and experimental validation of process kinetics involved in sputtering of a LiCoO2 compound target have been performed to analyze the effect of process kinetics on film stoichiometry. Studies on the conditioning of a new LiCoO2 sputtering target for various durations of pre-sputtering time were performed with the help of real time monitoring of glow discharge plasma by OES and also by analysing surface composition, and morphology of the deposited films. Films deposited from a conditioned target, under suitable deposition conditions were electrochemically tested for CV and charge/discharge, which showed an initial discharge capacity of 64 µAh/cm2/µm. Studies done on the deposition and characterization of solid electrolyte layer-LiPON have shown that, sputtering from powder target can be useful for certain compounds like Li3PO4 in which breaking of ceramic target and loss of material are severe problems. An ionic conductivity of 1.1 x10-6 S/cm was obtained for an Nt/Nd ratio of 1.42 for a RF power density of 3 W/cm2 and N2 flow of 30 sccm. Also the reasons for reduction in ionic conductivity of LiPON thin films on exposure to air have been analyzed by means of change in surface morphology and surface chemistry. Ionic conductivity of 2.8 x10-6 S/cm for the freshly deposited film has dropped down to 9.9 x10-10 S/cm due to the reaction with moisture, oxygen and carbon content of exposed air. Interest towards a Li-free thin film battery has prompted to choose Sn as the anode layer due to its relatively good electrochemical capacity compared with other metallic thin films and ease of processing. By controlling the rate of deposition of Sn, thin films of different surface morphology, roughness and crystallinity can be obtained with different electrochemical performance. The reasons for excessive volume changes during lithiation/delithiation of a porous Sn thin film have been analyzed with the aid of physicochemical characterization techniques. The results suggest that the films become progressively pulverized resulting in increased roughness with an increase in lithiation. Electrochemical impedance data suggest that the kinetics of charging becomes sluggish with an increase in the quantity of Li in Sn-Li alloy. Thin film batteries with configuraion LiCoO2/LiPON/Sn were fabricated by sequential sputter deposition on to Pt/Si substartes. Pt/Cu strips were used as the current collector leads with a polymer packaging. Electrochemical charge/discharge studies revealed discharge capacities in the range 6-15 µAh/cm2/µm with hundreds of repeated cycles. TFB with a higher capacity of 35 µAh/cm2/µm suffered capacity fade out after 7 cycles, for which reasons were analyzed. The surface and cross-sectional micrographs of cycled TFB showed formation of bubble like features on anode layer reducing integrity of electrolyte-anode interface. The irreversible Li insertion along with apparent surface morphology changes are most likely the main reasons for the capacity fade of the LiCoO2/LiPON/Sn TFB.

abstract: A distinct characteristic of ferroelectric materials is the existence of a reversible spontaneous polarization with the application of an electric field. The relevant properties ferroelectric lithium niobate surfaces include a low density of defects and external screening of the bound polarization charge. These properties result in unique surface electric field distribution with a strong electric field in the vicinity of domain boundaries, while away from the boundaries, the field decreases rapidly. In this work, ferroelectric lithium niobate (LN) is used as a template to direct the assembly of metallic nanostructures via photo-induced reduction and a substrate for deposition of ZnO semiconducting thin films via plasma enhanced atomic layer deposition (PE-ALD). To understand the mechanism the photo-induced deposition process the following effects were considered: the illumination photon energy and intensity, the polarization screening mechanism of the lithium niobate template and the chemical concentration. Depending on the UV wavelength, variation of Ag deposition rate and boundary nanowire formation are observed and attributed to the unique surface electric field distribution of the polarity patterned template and the penetration depth of UV light. Oxygen implantation is employed to transition the surface from external screening to internal screening, which results in depressed boundary nanowire formation. The ratio of the photon flux and Ag ion flux to the surface determine the deposition pattern. Domain boundary deposition is enhanced with a high photon/Ag ion flux ratio while domain boundary deposition is depressed with a low photon/Ag ion flux ratio. These results also support the photo-induced deposition model where the process is limited by carrier generation, and the cation reduction occurs at the surface. These findings will provide a foundational understanding to employ ferroelectric templates for assembly and patterning of inorganic, organic, biological, and integrated structures. ZnO films deposited on positive and negative domain surfaces of LN demonstrate different I-V curve behavior at different temperatures. At room temperature, ZnO deposited on positive domains exhibits almost two orders of magnitude greater conductance than on negative domains. The conductance of ZnO on positive domains decreases with increasing temperature while the conductance of ZnO on negative domains increases with increasing temperature. The observations are interpreted in terms of the downward or upward band bending at the ZnO/LN interface which is induced by the ferroelectric polarization charge. Possible application of this effect in non-volatile memory devices is proposed for future work.
Dissertation/Thesis
Ph.D. Physics 2011