Modeling Of Adhesion Mechanisms Of Graphite Based Anodes For Lithium Ion Batteries67z
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Modeling Of Adhesion Mechanisms Of Graphite Based Anodes For Lithium Ion Batteries67z
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Author : Nicolas Billot
language : en
Publisher: utzverlag GmbH
Release Date : 2022-08-16
Modeling Of Adhesion Mechanisms Of Graphite Based Anodes For Lithium Ion Batteries67z written by Nicolas Billot and has been published by utzverlag GmbH this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022-08-16 with Technology & Engineering categories.
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
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 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.