Physikalisch-elektrochemische Simulation von Lithium-Ionen-Batterien : Implementierung, Parametrierung und Anwendung

• Physico-electrochemical simulation of lithium-ion batteries : implementation, parametrization and application

Schmalstieg, Johannes; Sauer, Dirk Uwe (Thesis advisor); Simon, Ulrich (Thesis advisor)

Aachen : ISEA (2017)
Book, Dissertation / PhD Thesis

In: Aachener Beiträge des ISEA 96
Page(s)/Article-Nr.: viii, 168 Seiten : Illustrationen, Diagramme

Dissertation, RWTH Aachen University, 2017

Abstract

The increasing use of lithium-ion batteries as well as the high requirements, e.g. for fast charging of electric car, require a more detailed understanding of the cell system. For use under extreme conditions such as high charging currents, which can lead to strong aging due to lithium plating, an exact knowledge of the battery's internal state variables is necessary in order to be able to protect them with optimized battery diagnostics. The use of fundamental-based physico-electrochemical simulation models can help to provide the necessary understanding for these applications, as well as to reduce the otherwise required test effort for cell characterization. They allow to look at the processes taking place internally and thus the identification of the internal state variables which are decisive for the operation of the cell. This work starts with the description of the enhancements and implementation of a physico-electrochemical battery model, which greatly increases the flexibility and extensibility to new effects. Instead of the usual simulation of a cell as a 1D cross section, the extension to 2D and 3D structures makes it possible to reproduce inhomogeneities. It allows the free variation and combination of different material properties. In addition, double-layer capacitances were implemented in the electrical model, which allows the simulation of impedance spectra.In order to simulate a battery, the material parameters of the components used in the cell are required. The procedure for parameterizing these material data is described by means of a prismatic high-performance cell. This includes investigations of the electrolyte as well as the active materials, which are examined directly or electrochemically by use in laboratory cells. In addition, an analysis of the thermal properties is carried out since the self-heating of the cell and its effects on the cell performance cannot be neglected here. The quality of the determined data set is demonstrated by a validation based on discharge and charging curves, pulse tests, impedance spectra and a realistic driving profile, all at different temperatures. The parameterized model is used to perform exemplary simulations. In a model-based cell analysis, the effects of a particle size distribution are considered under various aspects. The components occurring in impedance spectra are assigned to the respective processes and properties. Furthermore, three effects which have occurred in aging tests are examined and the theories which have been developed are simulated. Thus, from the implementation of the model to the acquisition of the necessary material parameters up to the exemplary application, the possibilities of physico-electrochemical battery modelling are presented and their applicability and usefulness are demonstrated.