With increasing interest in energy storage and conversion devices for automobile applications, the necessity to understand and predict life behavior of rechargeable batteries, PEM fuel cells and super capacitors is paramount. These electrochemical devices are most beneficial when used in hybrid configurations rather than as individual components because no single device can meet both range and power requirements to effectively replace internal combustion engines for automobile applications. A system model helps us to understand the interactions between components and enables us to determine the response of the system as a whole. However, system models that are available predict just the performance and neglect degradation. In the first part of the thesis, a framework is provided to account for the durability phenomena that are prevalent in fuel cells and batteries in a hybrid system. Toward this end, the methodology for development of surrogate models is provided, and Pt catalyst dissolution in PEMFCs is used as an example to demonstrate the approach. Surrogate models are more easily integrated into higher level system models than the detailed physics-based models. As an illustration, the effects of changes in control strategies and power management approaches in mitigating platinum instability in fuel cells are reported. A system model that includes a fuel cell stack, a storage battery, power-sharing algorithm, and dc/dc converter has been developed; and preliminary results have been presented. These results show that platinum stability can be improved with only a small impact on system efficiency. Thus, this research will elucidate the importance of degradation issues in system design and optimization as opposed to just initial performance metrics. In the second part of the thesis, modeling of silicon negative electrodes for lithium ion batteries is done at both particle level and cell level. The dependence of the open-circuit potential curve on the state of charge in lithium insertion electrodes is usually measured at equilibrium conditions. Firstly, for modeling of lithium-silicon electrodes at room temperature, the use of a pseudo-thermodynamic potential vs. composition curve based on metastable amorphous phase transitions with path dependence is proposed. Volume changes during lithium insertion/de-insertion in single silicon electrode particle under potentiodynamic control are modeled and compared with experimental data to provide justification for the same. This work stresses the need for experiments for accurate determination of transfer coefficients and the exchange current density before reasoning kinetic hysteresis for the potential gap in Li-Si system. The silicon electrode particle model enables one to analyze the influence of diffusion in the solid phase, particle size, and kinetic parameters without interference from other components in a practical porous electrode. Concentration profiles within the silicon electrode particle under galvanostatic control are investigated. Sluggish kinetics is established from cyclic voltammograms at different scan rates. Need for accurate determination of exchange current density for lithium insertion in silicon nanoparticles is discussed. This model and knowledge thereof can be used in cell-sandwich model for the design of practical lithium ion cells with composite silicon negative electrodes. Secondly, galvanostatic charge and discharge of a silicon composite electrode/separator/ lithium foil is modeled using porous electrode theory and concentrated solution theory. Porosity changes arising due to large volume changes in the silicon electrode with lithium insertion and de-insertion are included and analyzed. The concept of reservoir is introduced for lithium ion cells to accommodate the displaced electrolyte. Influence of initial porosity and thickness of the electrode on utilization at different rates is quantitatively discussed. Knowledge from these studies will guide design of better silicon negative electrodes to be used in dual lithium insertion cells for practical applications.

Natural graphite from cheap and abundant natural sources is an attractive anode material for lithium ion batteries. We report on modifications of such a common natural graphite, whose electrochemical performance is very poor, with solutions of (NH4)2S2O8, concentrated nitric acid, and green chemical solutions such of e.g. hydrogen peroxide and ceric sulfate. These treatments resulted in markedly im-proved electrochemical performance (reversible capacity, coulombic efficiency in the first cycle and cycling behavior). This is attributed to the effective removal of active defects, formation of a new dense surface film consisting of oxides, improvement of the graphite stability, and introduction of more nanochannels/micropores. These changes inhibit the decomposition of electrolyte solution, pre-vent the movement of graphene planes along a-axis direction, and provide more passage and storage sites for lithium. The methods are mild, and the uniformity of the product can be well controlled. Pilot experiments show promising results for their application in industry.

The use of Lithium-ion batteries in the automotive industry has increased tremendously in the last few years. The anticipated increase in demand of lithium to power electric and hybrid cars has prompted researchers to examine the long term sustainability lithium as a transportation resource. To provide a better understanding of future availability, this thesis presents a systems framework for the key processes and materials and energy flows involved in the electric vehicle lithium-ion battery life cycle, on a global scale. This framework tracks the flow of lithium and energy inputs and outputs from extraction, to production, to on road use, and all the way to end of life recycling and disposal. This process flow model is the first step in developing a life cycle analysis model for lithium that will eventually help policymakers assess the future role of lithium battery recycling, and at what point in time establishing a recycling infrastructure becomes imminent.

Lithium-ion batteries are most commonly employed as power sources for portable electronic devices. Limited capacity, high cost, and safety problems associated with the commercially used graphite anode materials are hampering the use of lithium-ion batteries in larger-scale applications such as the electric vehicle. Nanocomposite alloys have shown promise as new anode materials because of their better safety due to higher operating potential, increased energy density, low cost, and straightforward synthesis as compared to graphite. The purpose of this dissertation is to investigate and understand the electrochemical properties of several types of nanocomposite alloys and to assess their viability as replacement anode materials for lithium-ion batteries. Tin and antimony are two elements that are active toward lithium. Accordingly, this dissertation is focused on tin-based and antimony-based nanocomposite alloy materials. Tin and antimony each have larger theoretical capacities than commercially available anodes, but the capacity fades dramatically in the first few cycles when metallic tin or antimony is used as the anode in a lithium-ion battery. This capacity fade is largely due to the agglomeration of particles in the anode material and the formation of a barrier layer between the surface of the anode and the electrolyte. In order to suppress agglomeration, the active anode material can be constrained by an inactive matrix of material that makes up the nanocomposite. By controlling the surface of the particles in the nanocomposite via methods such as the addition of additives to the electrolyte, the detrimental effects of the solid-electrolyte interphase layer (SEI) can be minimized, and the capacity of the material can be maintained. Moreover, the nanocomposite alloys described in this dissertation can be used above the voltage where lithium plating occurs, thereby enhancing the safety of lithium-ion batteries. The alloy anodes in this study are synthesized by high-energy mechanical milling and furnace heating. The materials are characterized by X-ray diffraction, scanning and transmission electron microscopies, and X-ray photoelectron spectroscopy. Electrochemical performances are assessed at various temperatures, potential ranges, and charge rates. The lithiation/delithiation reaction mechanisms for these nanocomposite materials are explored with ex-situ X-ray diffraction. Specifically, three different nanocomposite alloy anode materials have been developed: Mo3Sb7-C, Cu2Sb-Al2O3-C, and Cu6Sn5-TiC-C. Mo3Sb7-C has high gravimetric capacity and involves a reaction mechanism whereby crystalline Mo3Sb7 disappears and is reformed during each cycle. Cu2Sb-Al2O3-C with small particles (2 - 10 nm) of Cu2Sb dispersed in the Al2O3-C matrix is made by a single-step ball milling process. It exhibits long cycle life (+ 500 cycles), and the reversibility of the reaction of Cu2Sb-Al2O3-C with lithium is improved when longer milling times are used for synthesis. The reaction mechanism for Cu2Sb-Al2O3-C appears to be dependent upon the size of the crystalline Cu2Sb particles. The coulombic efficiency of Cu2Sb-Al2O3-C is improved through the addition of 2 % vinylethylene carbonate to the electrolyte. With a high tap density of 2.2 g/cm3, Cu6Sn5-TiC-C exhibits high volumetric capacity. The reversibility of the reaction of Cu6Sn5-TiC-C with lithium is improved when the material is cycled above 0.2 V vs. Li/Li+. / text

Lithium-ion batteries play a crucial role in portable electronics, but require further innovation for electric vehicle and grid storage applications. To meet this demand, significant emphasis has been placed on developing safe, inexpensive, high energy density cathode materials. LiFePO₄ is a candidate cathode material for electric vehicle and grid storage applications. Vanadium-doped LiFePO₄ cathodes of the form [chemical formula] (0 ≤ x ≤ 0.25) were synthesized here by a facile, low-temperature microwave-assisted solvothermal (MW-ST) method. Such an approach offers manufacturing-energy and cost savings compared to conventional synthesis. Additionally, although [chemical formula] has been synthesized previously by conventional methods, it is shown here that the MW-ST method allows much higher doping levels than can be achieved at conventional temperatures, indicating that metastable phases can be isolated through the low-temperature microwave-assisted synthesis. LiFePO₄ suffers from poor ionic conductivity, but this limitation can be minimized by microwave-assisted synthesis through a tuning of the particle size, allowing for decreased Li⁺ diffusion paths. LiVOPO₄ is another polyanion material with higher energy density than LiFePO₄, but similar ionic conductivity limitations. It has not been previously synthesized by MW-ST. Thus, a MW-ST method was developed here to prepare LiVOPO₄. By varying reaction conditions, three polymorphic modifications of LiVOPO₄ were accessed and the electrochemical performance was optimized. LiVOPO₄ can be further discharged to Li₂VOPO₄, which has been suggested in the literature, but the structural transformation that accompanies this process has not been detailed. To this end, the delithiation process was studied by ex situ XRD measurements to better understand how the second lithium is accommodated. Finally, MW-ST has also been exploited to grow thin films of anatase TiO₂ phase on indium tin oxide (ITO)-coated glass substrates. The microwave field is selectively absorbed by the conductive ITO layer on the glass substrates, leading to ohmic heating. The resulting heated ITO layer acts as a favorable site for nucleation and growth. TiO₂ thin films have widespread applications in the energy and electronics sectors. Such selective microwave-assisted ohmic heating of solid materials within a growth solution represents a promising new avenue for microwave synthesis, which has been minimally explored in the literature. / text

Lithium-ion batteries are being intensely pursued as energy storage devices because they provide higher energy and power densities compared to other battery systems such as lead-acid and nickel-metal hydride batteries. This dissertation (i) explores the use of a low-temperature microwave-assisted synthesis process to obtain aliovalently-doped lithium transition-metal phosphates and lower-valent vanadium oxide spinels, some of which are difficult to obtain by conventional high-temperature processes, and (ii) presents an investigation of the electrochemical properties of the aliovantly-doped phosphate cathodes and doped lithium manganese oxide and oxyfluoride spinel cathodes in lithium-ion batteries. Following the introduction and general experimental procedures, respectively, in Chapters 1 and 2, Chapter 3 first focuses on understanding of how the inductive effect and structural features in lithium transition-metal borate, silicate, and phosphate cathodes affect the M²⁺ʹ³⁺redox energies. It is found that the magnitude of the voltages delivered by the polyanion cathodes can be predicted based simply on the coordination of the transition-metal ion. Furthermore, the differences in the voltages delivered by the phosphates and pyrophosphates are explained by considering the resonance structures and their contribution to the covalency of the polyanion. Chapter 4 presents a low-temperature microwave-assisted solvothermal process to substitute 20 atom % V³⁺ for Mn²⁺ in LiMnPO₄. It is shown that the solubility of vanadium in LiMnPO₄ decreases upon heating the doped samples to ≥ 575 °C, demonstrating the importance of employing a low-temperature process to achieve aliovalent doping in LiMnPO₄. It is further demonstrated that by increasing the vanadium content in the material, the discharge capacity in the first cycle could be increased without any additional carbon coating. Subsequent X-ray absorption spectroscopy data reveal that the better performance is facilitated by enhanced Mn-O hybridization upon incorporating vanadium into the lattice. Chapter 5 explores the influence of various factors, such as the oxidation state of Mn, electronegativity of the dopant cation Mn+, and the dissociation energy of M-O bond, on the electrochemical properties of cation-doped oxide and oxyfluoride spinel cathodes. As an extension, Chapter 6 presents the effect of processing conditions on the surface concentration of the dopant cation Mn+. Chapter 7 presents an extension of the low-temperature microwave-assisted synthesis process to obtain AV₂O₄ (Mg, Fe, Mn, and Co) spinel oxides. The method is remarkably effective in reducing the synthesis time and energy use due to the efficiency of dielectric heating compared to conventional heating. The ability to access V³⁺ is facilitated by the relative positions of the energy levels of the cations in solution, which is lower than that in the solid, and the use of a strong reducing solvent like TEG. Finally, Chapter 8 provides a summary of the salient findings in this dissertation. / text

For the broad commercial success of electric vehicles (EVs), it is essential to deeply understand how batteries behave in this challenging application. This thesis has therefore been focused on studying automotive lithium-ion batteries in respect of their performance under EV operation. Particularly, the  need  for  simple  methods  estimating  the  state-of-health  (SOH)  of batteries during EV operation has been addressed in order to ensure safe, reliable, and cost-effective EV operation. Within  the  scope  of  this  thesis,  a  method  has  been  developed  that  can estimate the SOH indicators capacity and internal resistance. The method is solely based on signals that are available on-board during ordinary EV operation  such  as  the  measured  current,  voltage,  temperature,  and  the battery  management  system’s  state-of-charge  estimate.  The  approach  is based on data-driven battery models (support vector machines (SVM) or system  identification)  and  virtual  tests  in  correspondence  to  standard performance  tests  as  established  in  laboratory  testing  for  capacity  and resistance determination. The proposed method has been demonstrated for battery data collected in field tests and has also been verified in laboratory. After a first proof-of-concept of the method idea with battery pack data from a plug-in hybrid electric vehicle (PHEV) field test, the method was improved with the help of a laboratory study where battery electric vehicle (BEV) operation of a battery  cell  was  emulated  under  controlled  conditions  providing  a thorough validation possibility. Precise partial capacity and instantaneous resistance  estimations  could  be  derived  and  an  accurate  diffusion resistance estimation was achieved by including a current history variable in the SVM-based model. The dynamic system identification battery model gave precise total resistance estimates as well. The SOH estimation method was also applied to a data set from emulated hybrid electric vehicle (HEV) operation of a battery cell on board a heavy-duty vehicle, where on-board standard  test  validation  revealed  accurate  dynamic  voltage  estimation performance of the applied model even during high-current situations. In order to exhibit the method’s intended implementation, up-to-date SOH indicators have been estimated from driving data during a one-year time period. / <p>QC 20150914</p>

M. Tech. Electrical Engineering. / Hydrogen is in the middle of many discussions as being a good alternative to petrol for the struggle against pollution and global warming. The fact that hydrogen can be found in infinite quantities such as in water or in space makes it a renewable energy. It is the object of much research works in order to be used in replacement of fossil energy such as in hybrid vehicles. However, the main shed of hydrogen is the difficulties to store it. Indeed, being the first element of the periodic table, it is the lightest, spreads a lot and can burn easily. The aim of this project is to achieve the wiring diagram of an electrical bicycle. The use of a hydrogen fuel cell allows feeding the electrical motor of the vehicle. However, due to a matter of low response time of the fuel cell, lithium-ion batteries are also used. Indeed, at the start state for instance, the fuel cell needs some time to warm and reach the nominal temperature of functioning. Lithium-ion batteries allow feeding the electrical motor during the warm up time but also to respond to peak of load. Hybrid motorization represents the future of car industry and tends to be used as a replacement of petrol engine partly responsible of greenhouse gases emissions. Some of those vehicles are already put in place in some big cities all over the world and allow moving rapidly without polluting. This project concerns a hybrid system for an electrical bicycle but the idea is to extend to bigger kind of vehicles.

This thesis explores mechanical behavior of microelectronic devices and lithium-ion batteries. We first examine electromigration-induced void formation in solder bumps by constructing a theory that couples electromigration and creep. The theory can predict the critical current density below which voids do not form. Due to the effects of creep, this quantity is found to be independent of the solder size and decrease exponentially with increasing temperature, different from existing theories. / Engineering and Applied Sciences

Utilization of amorphous metallic alloy has received much attention for use in numerous microelectronic and electrochemical devices since they provide unique electrical, thermal conductivity, and magnetic properties. To develop these functional properties, it is essential to understand the amorphous structure and the property relationships. First principles calculations provide insight into the structure, thermodynamic stability, electronic and magnetic properties of amorphous alloys. For Ru- and Co-based alloys, the thermodynamic stability was examined by calculating the mixing energy along with those of crystalline counterparts. The amorphous RuP, CoP, RuB, and CoB alloys, become energetically more favorable than their crystalline counterparts at moderate P(B) content. The atomistic structures have well-defined local structures depending on the atomic size ratio and electronic interactions between constituent elements. Their local ordering is attributed to strong p-d hybridization, which contributes to stabilizing the Ru(Co)-P(B) alloys. Surface segregation of P(B) and interfacial adhesion with copper were also studied. Li-X (X: Si, Ge, and Sn) were examined when 1 or 2 Li atoms are inserted into the interstitial sites. Li insertion in the tetrahedral site, which is the most preferable site in the diamond matrix, causes outward displacement and charge localization around the X neighbors, thereby weakening of the covalent bonds leading to destabilization of the host matrix. We present the energetics, structure, electronic and mechanical properties of crystalline and amorphous Li-X (X: Si, Ge, Sn, and Si+Sn) alloys. Our calculations show that the incorporation of Li leads to disintegration of the tetrahedrally-bonded X network into small clusters of various shapes. Electronic structure analysis highlights that the charge transfer leads to weakening or breaking of X bonds with the growing splitting between s and p states, and consequently the Li-X alloys softens with increasing Li content. / text