Modeling transport properties and electrochemical performance of hierarchically structured lithium-ion battery cathodes using resistor networks and mathematical half-cell models

Modeling transport properties and electrochemical performance of hierarchically structured lithium-ion battery cathodes using resistor networks and mathematical half-cell models
Author: Birkholz, Oleg
Publisher: KIT Scientific Publishing
Total Pages: 246
Release: 2022-10-05
Genre: Science
ISBN: 373151172X

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Hierarchically structured active materials in electrodes of lithium-ion cells are promising candidates for increasing gravimetric energy density and improving rate capability of the system. To investigate the influence of cathode structures on the performance of the whole cell, efficient tools for calculating effective transport properties of granular systems are developed and their influence on the electrochemical performance is investigated in specially adapted cell models.

Dynamic Model-based Analysis of Oxygen Reduction Reaction in Gas Diffusion Electrodes

Dynamic Model-based Analysis of Oxygen Reduction Reaction in Gas Diffusion Electrodes
Author: Röhe, Maximilian
Publisher: KIT Scientific Publishing
Total Pages: 178
Release: 2024-01-09
Genre:
ISBN: 3731512343

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In this work, the first simulation model of oxygen depolarized cathodes (ODC), which are silver catalyst-based gas diffusion electrodes, is presented that considers the phase equilibrium of the gas-liquid interface and structure-related inhomogeneities in electrolyte distribution. By means of the model it has been identified that mass transport of water and ions in the liquid phase is a crucial factor for electrode performance and how it is influenced by the electrode structure.

Multiscale Modeling of Curing and Crack Propagation in Fiber-Reinforced Thermosets

Multiscale Modeling of Curing and Crack Propagation in Fiber-Reinforced Thermosets
Author: Schöller, Lukas
Publisher: KIT Scientific Publishing
Total Pages: 230
Release: 2024-03-15
Genre:
ISBN: 3731513404

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During the production of fiber-reinforced thermosets, the resin material undergoes a reaction that can lead to damage. A two-stage polymerization reaction is modeled using molecular dynamics and evaluations of the system including a fiber surface are performed. In addition, a phase-field model for crack propagation in heterogeneous systems is derived. This model is able to predict crack growth where established models fail. Finally, the model is used to predict crack formation during curing.

Application of Data Mining and Machine Learning Methods to Industrial Heat Treatment Processes for Hardness Prediction

Application of Data Mining and Machine Learning Methods to Industrial Heat Treatment Processes for Hardness Prediction
Author: Lingelbach, Yannick
Publisher: KIT Scientific Publishing
Total Pages: 278
Release: 2024-07-24
Genre:
ISBN: 3731513528

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This work presents a data mining framework applied to industrial heattreatment (bainitization and case hardening) aiming to optimize processes and reduce costs. The framework analyses factors such as material, production line, and quality assessment for preprocessing, feature extraction, and drift corrections. Machine learning is employed to devise robust prediction strategies for hardness. Its implementation in an industry pilot demonstrates the economic benefits of the framework. - This work presents a data mining framework applied to industrial heattreatment (bainitization and case hardening) aiming to optimize processes and reduce costs. The framework analyses factors such as material, production line, and quality assessment for preprocessing, feature extraction, and drift corrections. Machine learning is employed to devise robust prediction strategies for hardness. Its implementation in an industry pilot demonstrates the economic benefits of the framework.

Development of NbN based Kinetic Inductance Detectors on sapphire and diamond substrates for fusion plasma polarimetric diagnostics

Development of NbN based Kinetic Inductance Detectors on sapphire and diamond substrates for fusion plasma polarimetric diagnostics
Author: Mazzocchi, Francesco
Publisher: KIT Scientific Publishing
Total Pages: 212
Release: 2022-07-01
Genre: Technology & Engineering
ISBN: 3731511819

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This work aimed at designing, studying and producing the first prototypes of KIDs tailored for fusion plasma polarimetric diagnostics. Diamond was considered for the first time as substrate material for low-temperature superconducting detectors given its unmatched optical, radiation hardness and thermal qualities, properties necessary for working environments potentially saturated with radiation. This work represents a first step toward the optimization and final application of this technology.

Physically based Impedance Modelling of Lithium-Ion Cells

Physically based Impedance Modelling of Lithium-Ion Cells
Author: Illig, Joerg
Publisher: KIT Scientific Publishing
Total Pages: 231
Release: 2014-09-19
Genre: Technology & Engineering
ISBN: 3731502461

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In this book, a new procedure to analyze lithium-ion cells is introduced. The cells are disassembled to analyze their components in experimental cell housings. Then, Electrochemical Impedance Spectroscopy, time domain measurements and the Distribution function of Relaxation Times are applied to obtain a deep understanding of the relevant loss processes. This procedure yields a notable surplus of information about the electrode contributions to the overall internal resistance of the cell.

Modeling of Electronic and Ionic Transport Resistances Within Lithium-ion Battery Cathodes

Modeling of Electronic and Ionic Transport Resistances Within Lithium-ion Battery Cathodes
Author: David Eugene Stephenson
Publisher:
Total Pages: 29131
Release: 2008
Genre: Electronic dissertations
ISBN:

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In this work, a mathematical model is reported and validated, which describes the performance of porous electrodes under low and high rates of discharge. This porous battery model can be used to provide researchers a better physical understanding relative to prior models of how cell morphology and materials affect performance due to improved accounting of how effective resistance change with morphology and materials. The increased understanding of cell resistances will enable improved design of cells for high-power applications, such as hybrid and plug-in-hybrid electric vehicles. It was found electronic and liquid-phase ionic transport resistances are strongly coupled to particle conductivity, size, and distribution of particle sizes. The accuracy of determining effective resistances was increased by accounting for how particle's size, volume fraction, and electronic conductivity affect electronic resistances and by more accurately determining how cell morphology influences effective liquid-phase transport resistances. These model additions are used to better understand the cause for decreased utilization of active materials for relatively highly loaded lithium-ion cathodes at high discharge rates. Lithium cobalt and ruthenium oxides were tested and modeled individually and together in mixed-oxide cathodes to understand how the superior material properties relative to each other can work together to reduce cell resistances while maximizing energy storage. It was found for lithium cobalt oxide, a material with low electronic conductivity, its low rate (1C) performance is dominated by local electronic resistances between particles. At high rates (5C or higher) diffusional resistance in the liquid electrolyte had the greatest influence on cell performance. It was found in the mixed-oxide system that the performance of lithium cobalt oxide was improved by decreasing its local electronic losses due to the addition of lithium ruthenium oxide, a highly conductive active material, which improved the number of electron pathways to lithium cobalt oxide thereby decreasing local electronic losses.

Theoretical Insights into the Electrochemical Properties of Ionic Liquid Electrolytes in Lithium-Ion Batteries

Theoretical Insights into the Electrochemical Properties of Ionic Liquid Electrolytes in Lithium-Ion Batteries
Author: Leila Maftoon-Azad
Publisher: CRC Press
Total Pages: 75
Release: 2024-09-17
Genre: Technology & Engineering
ISBN: 1040157610

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This book provides a concise overview of the use of ionic liquids as electrolytes in lithium-ion batteries (LIBs) from a theoretical and computational perspective. It focuses on computational studies to understand the behavior of lithium ions in different ionic liquids and to optimize the performance of ionic liquid-based electrolytes. The main features of the book are as follows: • Provides a thorough understanding of the theoretical and computational aspects of using ionic liquids as electrolytes in LIBs, including the evaluation and reproducibility of the theoretical paths. • Covers various computational methods such as density functional theory, molecular dynamics, and quantum mechanics that have been used to study the behavior of lithium ions in different solvents and to optimize the performance of ionic liquid-based electrolytes. • Discusses recent advances such as new computational methods for predicting the properties of ionic liquid-based electrolytes, new strategies for improving the stability and conductivity of these electrolytes, and new approaches for understanding the kinetics and thermodynamics of redox reactions with ionic liquids. • Suggests how theoretical insights can be translated into practical applications for improving performance and safety. This monograph will be of interest to engineers working on LIB optimization.

Electrochemical-thermal Modeling of Lithium-ion Batteries

Electrochemical-thermal Modeling of Lithium-ion Batteries
Author: Mehrdad Mastali Majdabadi Kohneh
Publisher:
Total Pages: 202
Release: 2016
Genre: Electric automobiles
ISBN:

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Incorporating lithium-ion (Li-ion) batteries as an energy storage system in electric devices including electric vehicles brings about new challenges. In fact, the design of Li-ion batteries has to be optimized depending on each application specifications to improve the performance and safety of battery operation under each application and at the same time prevent the batteries from quick degradation. As a result, accurate models capable of predicting the behavior of Li-ion batteries under various operating conditions are necessary. Therefore, the main objective of this research is to develop a battery model that includes thermal heating and is suitable for large-sized prismatic cells used in electric vehicles. This works starts with developing a dual-extended Kalman filter based on an equivalent circuit model for the battery. The dual-extended Kalman filter simultaneously estimates the dynamic internal resistance and state of the charge of the battery. However, the estimated parameters are only the fitted values to the experimental data and may be non-physical. In addition, this filter is only valid for the operating conditions that it is validated against via experimental data. To overcome these issues, physics-based electrochemical models for Li-ion batteries are subsequently considered. One drawback of physics-based models is their high computational cost. In this work, two simplified one-dimensional physics-based models capable of predicting the output voltage of coin cells with less than 2.5% maximum error compared to the full-order model are developed. These models reduce the simulation computational time more than one order of magnitude. In addition to computational time, the accuracy of the physico-chemical model parameter estimates is a concern for physics-based models. Therefore, commercial LiFePO4 (LFP) and graphite electrodes are precisely modelled and characterized by fitting experimental data at different charge/discharge rates (C/5 to 5C). The temperature dependency of the kinetic and transport properties of LFP and graphite electrodes is also estimated by fitting experimental data at various temperatures (10 °C, 23 °C, 35 °C, and 45 °C). Since the spatial current and temperature variations in the large-sized prismatic cells are significant, one-dimensional models cannot be used for the modeling of these prismatic cells. In this work, a resistor network methodology is utilized to combine the one-dimensional models into a three-dimensional multi-layer model. The developed model is verified by comparing the simulated temperatures at the surface of the prismatic cell (consist of LFP as the positive and graphite as the negative electrode) to experimental data at different charge/discharge rates (1C, 2C, 3C, and 5C). Using the developed model the effect of tab size and location, and the current collector thickness, on the electrochemical characteristics of large-sized batteries is evaluated. It is shown that transferring tabs from the edges and the same side (common commercial design) to the center and opposite sides of the cell, and extending them as much as possible in width, lowers the non-uniformity variation in electrochemical current generation.