Multiscale modeling and numerical simulations of Lithium ion battery electrodes using real microstructures

• Applicants: Professor Dr. Thomas Carraro; Professorin Dr.-Ing. Ellen Ivers-Tiffée
• Subject Area: Synthesis and Properties of Functional Materials ; Mathematics
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 252382019

The long-term objective of this project is to establish an interdisciplinary method that allows the model-driven optimization of porous electrodes. As a special case we consider electrodes for Lithium-ion batteries (LIB), which are of increasing technological interest for existing renewable energy strategies. A state of the art Lithium-ion cell consists of two porous electrodes (anode and cathode) performing the tasks of storing the Lithium within the crystal structure and of providing it to the liquid electrolyte which fills the porosity and serves as an ionic connection between the two electrodes. The electronic connection is provided by the electrodes and the metallic current collectors, which serve as the terminals to an external circuit. Combining precise 3D reconstructions and detailed modeling of the electrodes, the rate limiting processes can be identified and improved microstructure can be obtained.To reach this goal one essential prerequisite is the quantitative characterization of the electrode microstructure and the determination of its influence on the electrochemical mechanisms. The precise quantification of microstructural parameters is required to perform model based simulations that can be used for electrodes optimization. In particular, the characterization with respect to the following processes and related parameters is essential: (a1) electrochemical reaction (reduction and oxidation) and (a2) surface to volume ratio and volume fractions; (b1) transport in percolating systems for ionic and electronic species and (b2) effective transport parameters (tortuosity); (c1) storing the lithium in the crystal structure of the active material and (c2) distribution and dimension of the active particles.The main limits of the state-of-the-art methods affect all these aspects, since they use simplified models, do not reach the needed resolution of all material phases, and do not use numerical methods that allow the needed multi-scale accuracy. In particular, a more precise quantitative method is needed: (a3) to obtain the required approximation of the active surface, (b3) to define whether effective parameters can be used and with which precision they need to be determined, (c3) to achieve the necessary approximation at the microscopic level. In this project we will perform the derivation, implementation and verification of a multi-scale transient model for LIB electrodes, which will be based on a method of partial model reduction that needs the contribution of the Intitut für Werkstoffe der Elektrotechnik (IWE) and Institut für Angewandte Mathematik (IAM). IWE will focus on reliable and original methods for the electrode reconstruction, the modeling and quantification of model and microstructure parameters. IAM will focus on mathematical methods for the model reduction and numerical solution using high performance computing techniques and novel error estimation approaches.

• DFG Programme: Research Grants