Author: Mohammed Fouad Hasan
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Li-ion batteries, owing to their unique characteristics with high power and energy density, are broadly considered a leading candidate for vehicle electrification. A pivotal performance drawback of the Li-ion batteries manifests in the lengthy charging time and the limited cycle life. Fast charging is one of the most desired characteristics for the emerging vehicle technologies, which is at a nascent stage and not well understood. Moreover, cycle life is a vital component of battery integration and market penetration. The objectives of this work include: (1) investigating the fast charging induced performance limitations with emphasis on temperature extremes; and (2) studying the implications of combined chemical and mechanical degradation modes on the battery cycle life. In this work, a coupled electrochemical-thermal model is utilized to study the internal behavior and thermal interactions during fast charging process. Additionally, the cycle life predictions are realized by developing a capacity fade model consisting of a coupled chemical (irreversible solid electrolyte interface formation) and mechanical (intercalation induced damage) degradation formalism with thermal effect. Primary results with conventional protocol at high rate (3C) show that at moderate and high operating temperatures the main performance limitations of fast charging originate from lithium ion transport in the electrolyte and ohmic resistance. However, charge transfer resistance is found to be the limiting mechanism for the conventional 1C charging rate at low temperatures. Furthermore, it was found that the concentration build-up at anode surface can be effectively manipulated by using an appropriate charging protocol such as pulse charging and boostcharging. However, it was concluded that at low temperatures, a successful charging protocol is achieved by utilizing the principle of thermal excitement. For battery cycle life, results show that mechanical degradation is the predominant mechanism for capacity fade at low temperatures and high rates. However, the temperature as a stress factor is the principle capacity fade source at high operating temperatures where mechanical degradation is not prominent. The importance of cooling condition, particle size and the exchange current density on life cycle have been emphasized. Finally, a degradation phase map that shows the significance of active particle size and stress factors (temperature and current rate) on the capacity fade is presented. It is concluded that the particle size showed a trade-off in the capacity fade results at different temperatures. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/152626
Author: Claudio V. Di Leo
Publisher:
ISBN:
Category :
Languages : en
Pages : 250
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Book Description
Mechanical deformation plays a crucial role both in the normal operation of a Lithium-Ion battery, as well as in its degradation and ultimate failure. This thesis addresses the theoretical formulation, numerical implementation, and application of fully-coupled deformation-diffusion theories aimed at two different classes of electrode materials: (i) phase-separating electrodes, and (ii) amorphous Silicon electrodes, which are elaborated on next. Central to the study of phase-separating electrodes is the coupling between mechanical deformation and the Cahn-Hilliard phase-field theory. We have formulated a thermodynamically consistent theory which couples Cahn-Hilliard species diffusion with large elastic deformations of a body. Through a split-method, we have numerically implemented our theory, and using our implementation we first studied the diffusion-only problem of spinodal decomposition in the absence of mechanical deformation. Second, we studied the chemomechanically- coupled problem of lithiation of isotropic spheroidal phase-separating electrode particles. We showed that the coupling of mechanical deformation with diffusion is crucial in determining the lithiation morphology, and hence the Li distribution, within these particles. Amorphous silicon (a-Si), when fully lithiated, has a theoretical capacity ~~ 10 times larger than current-generation graphite anodes. However, the intercalation of such a large amount of Li into a-Si induces very large elastic-plastic deformations. We have formulated and numerically implemented a fully-coupled deformation-diffusion theory, which accounts for transient diffusion of lithium and accompanying large elastic-plastic deformations. We have calibrated our theory, and applied it to modeling galvanostatic charging of hollow a- Si nanotubes whose exterior walls have been oxidized to prevent outward expansion. Our predictions of the voltage vs. state-of-charge (SOC) behavior at various charging rates (Crate) are in good agreement with experiments from the literature. Through simulation, we studied how plastic deformation affects the performance of a-Si-based anodes by reducing stress, thus enabling higher realizable capacities, and introducing dissipation. Finally, in order to design a-Si-based anodes aimed at mitigating failure of the solid electrolyte interphase (SEI), we have formulated and studied a continuum theory for the growth of an SEI layer - a theory which accounts for the generation of growth stresses.
Author: Blaise Bourdin
Publisher: Springer Science & Business Media
ISBN: 1402063954
Category : Technology & Engineering
Languages : en
Pages : 173
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Book Description
Presenting original results from both theoretical and numerical viewpoints, this text offers a detailed discussion of the variational approach to brittle fracture. This approach views crack growth as the result of a competition between bulk and surface energy, treating crack evolution from its initiation all the way to the failure of a sample. The authors model crack initiation, crack path, and crack extension for arbitrary geometries and loads.
Author: Yifan Gao
Publisher:
ISBN:
Category : Electrodes
Languages : en
Pages :
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Book Description
Lithium alloys with metallic or semi-metallic elements are attractive candidate materials for the next-generation rechargeable Li-ion battery anodes, thanks to their large specific and volumetric capacities. The key challenge, however, has been the large volume changes, and the associated stress buildup and failure during cycling. The chemo-mechanics of alloy-based electrode materials entail interactions among diffusion, chemical reactions, plastic flow, and material property evolutions. In this study, a continuum theory of two-way coupling between diffusion and deformation is formulated and numerically implemented. Analyses based on this framework reveal three major conclusions. First, the stress-to-diffusion coupling in Li/Si is much stronger than what has been known in other electrode materials. Practically, since the beneficial effect of stress-enhanced diffusion is more pronounced at intermediate or higher concentrations, lower charging rates should be used during the initial stages of charging. Second, when plastic deformation and lithiation-induced softening take place, the effect of stress-enhanced diffusion is neutralized. Because the mechanical driving forces tend to retard diffusion when constraints are strong, even in terms of operational charging rate alone, Li/Si nano-particles are superior to Li/Si thin films or bulk materials. Third, the diffusion of the host atoms can lead to significant stress relaxation even when the stress levels are below the yield threshold of the material, a beneficial effect that can be leveraged to reduce stresses because the host diffusivity in Li/Si can be non-negligible at higher Li concentrations. A theory of coupled chemo-mechanical fracture driving forces is formulated in order to capture the effect of deformation-diffusion coupling and lithiation-induced softening on fracture. It is shown that under tensile loading, Li accumulates in front of crack tips, leading to an anti-shielding effect on the energy release rate. For a pre-cracked Li/Si thin-film electrode, it is found that the driving force for fracture is significantly lower when the electrode is operated at higher Li concentrations -- a result of more effective stress relaxation via global yielding. The results indicate that operation at higher concentrations is an effective means to minimize failure of thin-film Li/Si alloy electrodes.
Author: Keith Oldham
Publisher: Elsevier
ISBN: 0323139639
Category : Science
Languages : en
Pages : 497
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Book Description
"Fundamentals of Electrochemical Science is a valuable contribution and I support the publication....I am looking forward to seeing this book on the shelves, and once published, I will not hesitate to recommend itto my students." --ANDRZEJ WIECKOWSKI, University of Illinois at Urbana-Champaign Deals comprehensively with the basic science of electrochemistry Treats electrochemistry as a discipline in its own right and not as a branch of physical or analytical chemistry Provides a thorough and quantitative description of electrochemical fundamentals
Author: David Linden
Publisher: McGraw-Hill Professional
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 1516
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Book Description
BETTER BATTERIES Smaller, lighter, more powerful, and longer-lasting: the better battery is a much-sought commodity in the increasingly portable, ever-more-wireless world of electronics. Powering laptops, handhelds, cell phones, pagers, watches, medical devices, and many other modern necessitites, batteries are crucial to today's cutting-edge technologies. BEST CHOICE FOR BATTERY DESIGN AND EVALUATION This definitive guide from top international experts provides the best technical guidance you can find on designing winning products and selecting the most appropriate batteries for particular applications. HANDBOOK OF BATTERIES covers the field from the tiniest batteries yet devised for life-critical applications to the large batteries required for electric and hybrid electric vehicles. EXPERT INFORMATION Edited by battery experts David Linden, battery consultant and editor of the first two editions, and Dr. Thomas Reddy, a pioneer in the lithium battery field, HANDBOOK OF BATTERIES updates you on current methods, helps you solve problems, and makes comparisons easier. Essential for professionals, valuable to hobbyists, and preferred as a consumer guide for battery purchasers, this the THE source for battery information. The only comprehensive reference in the field, HANDBOOK OF BATTERIES has more authoritative information than any other source: * Authored by a team of leading battery technology experts from around the globe * Covers the characteristics, properties, and performance of every major battery type * Entirely revised, including new information on Lithium Ion and Large Nickel Metal Hydride batteries, and portable fuel cells. This one-of-a-kind HANDBOOK helps you: * Apply leading-edge technologies, materials, and methods in new designs and products * Predict battery performance under any conditions * Have all the needed data and equations at your fingertips
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
In this paper, a one-dimensional computational framework is developed that can solve for the evolution of voltage and current in a lithium-ion battery electrode under different operating conditions. A reduced order model is specifically constructed to predict the growth of mechanical degradation within the active particles of the carbon anode as a function of particle size and C-rate. Using an effective diffusivity relation, the impact of microcracks on the diffusivity of the active particles has been captured. Reduction in capacity due to formation of microcracks within the negative electrode under different operating conditions (constant current discharge and constant current constant voltage charge) has been investigated. At the beginning of constant current discharge, mechanical damage to electrode particles predominantly occurs near the separator. As the reaction front shifts, mechanical damage spreads across the thickness of the negative electrode and becomes relatively uniform under multiple discharge/charge cycles. Mechanical degradation under different drive cycle conditions has been explored. It is observed that electrodes with larger particle sizes are prone to capacity fade due to microcrack formation. Finally, under drive cycle conditions, small particles close to the separator and large particles close to the current collector can help in reducing the capacity fade due to mechanical degradation.
Author: John Newman
Publisher: John Wiley & Sons
ISBN: 0471478423
Category : Science
Languages : en
Pages : 671
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Book Description
The new edition of the cornerstone text on electrochemistry Spans all the areas of electrochemistry, from the basicsof thermodynamics and electrode kinetics to transport phenomena inelectrolytes, metals, and semiconductors. Newly updated andexpanded, the Third Edition covers important new treatments, ideas,and technologies while also increasing the book's accessibility forreaders in related fields. Rigorous and complete presentation of the fundamentalconcepts In-depth examples applying the concepts to real-life designproblems Homework problems ranging from the reinforcing to the highlythought-provoking Extensive bibliography giving both the historical developmentof the field and references for the practicing electrochemist.
Author: J.C. Simo
Publisher: Springer Science & Business Media
ISBN: 0387227636
Category : Computers
Languages : en
Pages : 405
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Book Description
A description of the theoretical foundations of inelasticity, its numerical formulation and implementation, constituting a representative sample of state-of-the-art methodology currently used in inelastic calculations. Among the numerous topics covered are small deformation plasticity and viscoplasticity, convex optimisation theory, integration algorithms for the constitutive equation of plasticity and viscoplasticity, the variational setting of boundary value problems and discretization by finite element methods. Also addressed are the generalisation of the theory to non-smooth yield surface, mathematical numerical analysis issues of general return mapping algorithms, the generalisation to finite-strain inelasticity theory, objective integration algorithms for rate constitutive equations, the theory of hyperelastic-based plasticity models and small and large deformation viscoelasticity. Of great interest to researchers and graduate students in various branches of engineering, especially civil, aeronautical and mechanical, and applied mathematics.
Author: Jean Lemaitre
Publisher: Springer Science & Business Media
ISBN: 3662027615
Category : Science
Languages : en
Pages : 225
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Book Description
A new branch of science usually develops thus. Somebody publishes the basic ideas. Hesitatingly at first, then little by little, other original contributions appear, until a certain threshold is reached. Then, overview articles are printed, conferences are held, and a first mention is made in textbooks, until specialized monographs are written. Continuum darnage mechanics has reached that status now. To analyze or, if possible, to predict the failure of machine parts or other structures is one of the main goals of engineering science. Consequently fracture mechanics became one of its leading branches. It was based on the analysis of existing cracks. However, especially under conditions of cyclic loading, this might be too late to prevent a disaster. Therefore, the question regarding the precursory state, that is, the evolution of intemal darnage before macrocracks become visible, was then posed. One of the successful approaches to the problern was Weibull's theory which examined, in a statistical manner, the "weakest link" in the material volume under consideration. Unfortunately it proved too difficult mathematically to be applied to complicated parts or structures. Therefore it was highly appreciated by the scientific of material community when L. M. Kachanov published in 1958 a simple model darnage which subsequently could be extended to brittle elastic, plastic or viscous materials under all conditions of uniaxial or multiaxial, simple or cyclic loadings, so that it may be considered nearly universal.
