Multiscale Chemo Mechanical Mechanics Of High Capacity Anode Materials In Lithium Ion Nano Batteries
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Multiscale Chemo Mechanical Mechanics Of High Capacity Anode Materials In Lithium Ion Nano Batteries
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Author : Hui Yang
language : en
Publisher:
Release Date : 2014
Multiscale Chemo Mechanical Mechanics Of High Capacity Anode Materials In Lithium Ion Nano Batteries written by Hui Yang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
Rechargeable lithium-ion batteries (LIBs), which are the most prevailing and promising electrochemical energy storage and conversion devices due to their high energy density and design flexibility, are widely used in portable electronics and electric vehicles. Currently commercialized LIBs adopt graphite as anode for its long cycle life, abundant material supply, and relatively low cost. However, graphite suffers low specific charge capacity (372 mAhg-1), which is obviously insufficient for powering new generation electronic devices. Thus, considerable efforts are being undertaking to develop alternative anode materials with low cost, high capacity, and long cycle life. A variety of high capacity anode materials have been identified, and silicon (Si) stands as the leading candidate and has attracted much attention for its highest theoretical capacity (4200 mAhg-1). Nevertheless, inherent to the high-capacity electrodes, lithium (Li) insertion-extraction cycling induces huge volumetric expansion and stress inside the electrodes, leading to fracture, pulverization, electrical disconnectivity, and ultimately huge capacity loss. Therefore, a fundamental understanding of the degradation mechanisms in the high-capacity anodes during lithiation-delithiation cycling is crucial for the rational design of next-generation failure-resistant electrodes.In this thesis, a finite-strain chemo-mechanical model is formulated to study the lithiation-induced phase transformation, morphological evolution, stress generation and fracture in high capacity anode materials such as Si and germanium (Ge). The model couples Li reaction-diffusion with large elasto-plastic deformation in a bidirectional manner: insertion of the Li into electrode generates localized stress, which in turn mediates electrochemical insertion rates. Several key features observed from recent transmission electron microscopy (TEM) studies are incorporated into the modeling framework, including the sharp interface between the lithiated amorphous shell and unlithiated crystalline core, crystallographic orientation-dependent electrochemical reaction rate, and large-strain plasticity. The simulation results demonstrate that the model faithfully predicts the anisotropic swelling of lithiated crystalline silicon nanowires (c-SiNWs) observed from previous experimental studies. Stress analysis reveals that the SiNWs are prone to surface fracture at the angular sites where two adjacent facets intersect, consistent with previous experimental observations. In addition, Li insertion can induce high hydrostatic pressure at and closely behind the reaction front, which can lead to the lithiation retardation observed by TEM studies.For a comparative study, the highly reversible expansion and contraction of crystalline germanium nanoparticles (c-GeNPs) under lithiation-delithiation cycling are reported. During multiple cycles to the full capacity, the GeNPs remain robust without any visible cracking despite ~260% volume changes, in contrast to the size dependent fracture of crystalline silicon nanoparticles (c-SiNPs) upon the first lithiation. The comparative study of c-SiNPs, c-GeNPs, and amorphous SiNPs (a-SiNPs) through in-situ TEM and chemo-mechanical modeling suggest that the tough behavior of c-GeNPs and a-SiNPs can be attributed to the weak lithiation anisotropy at the reaction front. In the absence of lithiation anisotropy, the c-GeNPs and a-SiNPs experience uniform hoop tension in the surface layer without the localized high stress and therefore remain robust throughout multicycling. In addition, the two-step lithiation in a-SiNPs can further alleviate the abruptness of the interface and hence the incompatible stress at the interface, leading to an even tougher behavior of a-SiNPs. Therefore, eliminating the lithiation anisotropy presents a novel pathway to mitigate the mechanical degradation in high-capacity electrode materials. In addition to the study of the retardation effect caused by lithiation self-generated internal stress, the influence of the external bending on the lithiation kinetics and deformation morphologies in germanium nanowires (GeNWs) is also investigated. Contrary to the symmetric core-shell lithiation in free-standing GeNWs, bending a GeNW during lithiation breaks the lithiation symmetry, speeding up lithaition at the tensile side while slowing down at the compressive side of the GeNWs. The chemo-mechanical modeling further corroborates the experimental observations and suggests the stress dependence of both Li diffusion and interfacial reaction rate during lithiation. The finding that external load can mediate lithiation kinetics opens new pathways to improve the performance of electrode materials by tailoring lithiation rate via strain engineering. Furthermore, in the light of bending-induced symmetry breaking of lithiation, the mechanically controlled flux of the secondary species (i.e., Li) features a novel energy harvesting mechanism through mechanical stress.Besides the continuum level chemo-mechanical modelings, molecular dynamics simulations with the ReaxFF reactive force field are also conducted to investigate the fracture mechanisms of lithiated graphene. The simulation results reveal that Li diffusion toward the crack tip is both energetically and kinetically favored owing to the crack-tip stress gradient. The stress-driven Li diffusion results in Li aggregation around the crack tip, chemically weakening the crack-tip bond and at the same time causing stress relaxation. As a dominant factor in lithiated graphene, the chemical weakening effect manifests a self-weakening mechanism that causes the fracture of the graphene. Moreover, lithiation-induced fracture mechanisms of defective single-walled carbon nanotubes (SWCNTs) are elucidated by molecular dynamics simulations. The variation of defect size and Li concentration sets two distinct fracture modes of the SWCNTs upon uniaxial stretch: abrupt and retarded fracture. Abrupt fracture either involves spontaneous Li weakening of the propagating crack tip or is absent of Li participation, while retarded fracture features a "wait-and-go" crack extension process in which the crack tip periodically arrests and waits to be weakened by diffusing Li before extension resumes. The failure analysis of the defective CNTs upon lithiation, together with the cracked graphene, provides fundamental guidance to the lifetime extension of high capacity anode materials.
Multiscale Materials Modeling For Nanomechanics
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Author : Christopher R. Weinberger
language : en
Publisher: Springer
Release Date : 2016-08-30
Multiscale Materials Modeling For Nanomechanics written by Christopher R. Weinberger and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-08-30 with Technology & Engineering categories.
This book presents a unique combination of chapters that together provide a practical introduction to multiscale modeling applied to nanoscale materials mechanics. The goal of this book is to present a balanced treatment of both the theory of the methodology, as well as some practical aspects of conducting the simulations and models. The first half of the book covers some fundamental modeling and simulation techniques ranging from ab-inito methods to the continuum scale. Included in this set of methods are several different concurrent multiscale methods for bridging time and length scales applicable to mechanics at the nanoscale regime. The second half of the book presents a range of case studies from a varied selection of research groups focusing either on a the application of multiscale modeling to a specific nanomaterial, or novel analysis techniques aimed at exploring nanomechanics. Readers are also directed to helpful sites and other resources throughout the book where the simulation codes and methodologies discussed herein can be accessed. Emphasis on the practicality of the detailed techniques is especially felt in the latter half of the book, which is dedicated to specific examples to study nanomechanics and multiscale materials behavior. An instructive avenue for learning how to effectively apply these simulation tools to solve nanomechanics problems is to study previous endeavors. Therefore, each chapter is written by a unique team of experts who have used multiscale materials modeling to solve a practical nanomechanics problem. These chapters provide an extensive picture of the multiscale materials landscape from problem statement through the final results and outlook, providing readers with a roadmap for incorporating these techniques into their own research.
Advances In Applied Mechanics
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Author :
language : en
Publisher: Academic Press
Release Date : 2016-10-20
Advances In Applied Mechanics written by and has been published by Academic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-10-20 with Science categories.
Advances in Applied Mechanics draws together recent, significant advances in various topics in applied mechanics. Published since 1948, the book aims to provide authoritative review articles on topics in the mechanical sciences. While the book is ideal for scientists and engineers working in various branches of mechanics, it is also beneficial to professionals who use the results of investigations in mechanics in various applications, such as aerospace, chemical, civil, environmental, mechanical, and nuclear engineering. - Includes contributions from world-leading experts that are acquired by invitation only - Beneficial to scientists, engineers, and professionals who use the results of investigations in mechanics in various applications, such as aerospace, chemical, civil, environmental, mechanical, and nuclear engineering - Covers not only traditional topics, but also important emerging fields
Nano Chemo Mechanics Of Advanced Materials For Hydrogen Storage And Lithium Battery Applications
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Author : Shan Huang
language : en
Publisher:
Release Date : 2011
Nano Chemo Mechanics Of Advanced Materials For Hydrogen Storage And Lithium Battery Applications written by Shan Huang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with Lithium cells categories.
Chemo-mechanics studies the material behavior and phenomena at the interface of mechanics and chemistry. Material failures due to coupled chemo-mechanical effects are serious roadblocks in the development of renewable energy technologies. Among the sources of renewable energies for the mass market, hydrogen and lithium-ion battery are promising candidates due to their high efficiency and easiness of conversion into other types of energy. However, hydrogen will degrade material mechanical properties and lithium insertion can cause electrode failures in battery owing to their high mobilities and strong chemo-mechanical coupling effects. These problems seriously prevent the large-scale applications of these renewable energy sources. In this thesis, the atomistic and continuum modeling are performed to study the chemical-mechanical failures. The objective is to understand the hydrogen embrittlement of grain boundary engineered metals and the lithium insertion-induced fracture in alloy electrodes for lithium-ion batteries. : Hydrogen in metallic containment systems such as high-pressure vessels and pipelines causes the degradation of their mechanical properties that can result in sudden catastrophic fracture. A wide range of hydrogen embrittlement phenomena was attributed to the loss of cohesion of interfaces (between grains, inclusion and matrix, or phases) due to interstitially dissolved hydrogen. Our modeling and simulation of hydrogen embrittlement will address the question of why susceptibility to hydrogen embrittlement in metallic materials can be markedly reduced by grain boundary engineering. Implications of our results for efficient hydrogen storage and transport at high pressures are discussed.
Simulation Of Amorphous Silicon Anode In Lithium Ion Batteries
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Author : Miao Wang
language : en
Publisher:
Release Date : 2017
Simulation Of Amorphous Silicon Anode In Lithium Ion Batteries written by Miao Wang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with Electronic dissertations categories.
Multiscale Modeling Of Lithium Metal Anode For Next Generation Battery Design
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Author : Zhe Liu
language : en
Publisher:
Release Date : 2019
Multiscale Modeling Of Lithium Metal Anode For Next Generation Battery Design written by Zhe Liu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
Achieving smooth Li-plating without dendrite growth remains to be a grand challenge for developing the next-generation batteries based on Li metal anode. One of the main reasons is our inability to directly model and predict the atomistic and mesoscale mechanisms underlying the complex electroplating process involving concurrent ionic transport, redox reaction, and development of morphological instability. This dissertation presents a phase-field-based multiscale modeling framework to fundamentally understand the dendrite growth mechanism, theoretically interpret the experimental phenomena, and guide the Li metal battery design.The stability and functionality of the solid electrolyte interphase (SEI), i.e. the passivation layer between anode and electrolyte, play critical roles in maintaining a decent battery cycle life as well as calendar life. This becomes even more critical for Li metal anode, which is subjected to large volumetric and interfacial variations during Li plating and stripping. However, there is currently a lack of comprehensive understanding of Li metal/SEI interfaces and their electrochemical and mechanical properties, as well as the SEI growth mechanism at Li metal anode. In this thesis, we employed combined atomistic calculations and experimental techniques to study SEI. Using density function theory (DFT) calculations, we evaluated the interfacial energetics, density of states (DOS), and electrostatic potential profiles of two interfaces, LiF/Li and Li2CO3/Li, at Li metal anode. The calculation results suggest higher interface mechanical stability at the Li2CO3/Li interface but better electron tunneling leakage resistance at the LiF/Li interface. Experimentally, we employed an isotope-assisted time-of-flight secondary ion mass spectrometry (TOF SIMS) method to reveal a bottom-up formation mechanism of SEI growth. It is found that the topmost SEI near the electrolyte formed first and the SEI near the electrode formed later during the initial formation cycle. This growth mechanism was then correlated to the electrolyte one-electron and two-electron reduction reaction dynamics, which in turn explains the formation of two-layered organic-inorganic SEI composite structure. These results provide physical interpretation for the mesoscale phenomena and thus valuable insights for advanced electrode protective coating design.Continuum models have been widely used in attempts to understand and solve the Li dendrite growth problem at mesoscale. However, the limited availability and the accuracy of input physical parameters often limit the predictive power of existing continuum simulations. We hereby developed a multiscale model for a metal electrodeposition process based on the phase-field method and transition state theory by connecting the atomic level charge-transfer physics to the mesoscale morphological evolution. With this model, we discovered that the difference in cation de-solvation-induced exchange current is mainly responsible for the dramatic difference in dendritic Li-plating and smooth Mg-plating. This study not only reveals the physical origin of Li dendrite growth, but also provides a strategy to design dendrite-free Li-ion battery anodes guided by this multiscale model integrating the phase-field method and atomistic calculations.All-solid-state battery is a promising solution to suppress Li dendrite growth. However, recent experimental observation of mechanically-hard ceramic solid electrolytes such as LLZO indicates intergranular dendrite penetration. To understand the Li plating behavior in solid electrolytes, we further extended the multiscale phase-field model of Li dendrite growth by incorporating multiphase solid mechanics and explicit dendrite nucleation. This model helps elucidate the mechanism of major failure modes in a wide range of existing solid electrolyte systems, such as dendrite penetration, intergranular growth and isolated nucleation.
High Capacity Anode Materials For Lithium Ion Batteries
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Author : C Wang
language : en
Publisher:
Release Date : 2015
High Capacity Anode Materials For Lithium Ion Batteries written by C Wang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Inward Lithium Ion Breathing Of Hierarchically Porous Silicon Anodes
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Author :
language : en
Publisher:
Release Date : 2015
Inward Lithium Ion Breathing Of Hierarchically Porous Silicon Anodes written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Silicon has been identified as one of the most promising candidates as anode for high performance lithium-ion batteries. The key challenge for Si anodes is the large volume change induced chemomechanical fracture and subsequent rapid capacity fading upon cyclic charge and discharge. Improving capacity retention thus critically relies on smart accommodation of the volume changes through nanoscale structural design. In this work, we report a novel fabrication method for hierarchically porous Si nanospheres (hp-SiNSs), which consist of a porous shell and a hollow core. Upon charge/discharge cycling, the hp-SiNSs accommodate the volume change through reversible inward expansion/contraction with negligible particle-level outward expansion. Our mechanics analysis revealed that such a unique volume-change accommodation mechanism is enabled by the much stiffer modulus of the lithiated layer than the unlithiated porous layer and the low flow stress of the porous structure. Such inward expansion shields the hp-SiNSs from fracture, opposite to the outward expansion in solid Si during lithiation. Lithium ion battery assembled with this new nanoporous material exhibits high capacity, high power, long cycle life and high coulombic efficiency, which is superior to the current commercial Si-based anode materials. We find the low cost synthesis approach reported here provides a new avenue for the rational design of hierarchically porous structures with unique materials properties.
Silicon Anode Systems For Lithium Ion Batteries
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Author : Prashant N. Kumta
language : en
Publisher: Elsevier
Release Date : 2021-09-10
Silicon Anode Systems For Lithium Ion Batteries written by Prashant N. Kumta and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-09-10 with Technology & Engineering categories.
Silicon Anode Systems for Lithium-Ion Batteries is an introduction to silicon anodes as an alternative to traditional graphite-based anodes. The book provides a comprehensive overview including abundance, system voltage, and capacity. It provides key insights into the basic challenges faced by the materials system such as new configurations and concepts for overcoming the expansion and contraction related problems. This book has been written for the practitioner, researcher or developer of commercial technologies. - Provides a thorough explanation of the advantages, challenge, materials science, and commercial prospects of silicon and related anode materials for lithium-ion batteries - Provides insights into practical issues including processing and performance of advanced Si-based materials in battery-relevant materials systems - Discusses suppressants in electrolytes to minimize adverse effects of solid electrolyte interphase (SEI) formation and safety limitations associated with this technology
Mechanics Based Investigation Into The Structural Integrity And Optimization Of Core Shell Nanostructured Electrode Materials For Lithium Ion Batteries
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Author : Weiqun Li
language : en
Publisher:
Release Date : 2017
Mechanics Based Investigation Into The Structural Integrity And Optimization Of Core Shell Nanostructured Electrode Materials For Lithium Ion Batteries written by Weiqun Li and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with Energy storage categories.
To further improve the stability and capacity of the Si-based anode materials, the yolk-shell carbon-coated Si nanoparticles, which contain a void space between the yolk and shell, were studied through in situ lithiation and theoretical modeling, as discussed in Chapter 6. The geometrical dimension-dependent fracture of the nanoparticles was revealed from the experimental studies. A mechanics-based theoretical model was proposed to calculate the stress states in the carbon shell upon full lithiation. A design guideline was provided to maintain the structural integrity and maximize the capacity by optimizing the geometrical dimensions of the yolk-shell carbon-coated Si nanoparticles. Apart from voiding the fracture, interfacial stability between electrodes and cooper (Cu) current collector is also important for improving the performance of the Si-based electrode materials. In Chapter 7, the Si-coated Cu nanowires were synthesized though hydrothermal method and magnetron sputtering technique. The lithium nanostructures formed on the surface of Si shell during delithiation. The bulk lithium nanostructures reacted with the delithiated Si shell to form LixSi, inducing the fracture of the Si shell. However, the Si shell adhered well with the Cu core, indicating a stable cycling performance. These results showed the potential application of the Si-coated Cu nanowire structured anode materials for lithium ion batteries. Through the comprehensive studies of the core-shell nanostructured electrode materials, the lithiation/delithiation and fracture mechanisms of the high-capacity core-shell nanostructured electrode materials were analyzed. The experimental and theoretical approaches should be beneficial for the study of other electrode materials. The optimal design guidelines proposed in this thesis should be of great value for the design of the core-shell structured electrode materials with supreme structural integrity and high capacity for lithium ion batteries.