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

该项目的长期目标是建立一种跨学科的方法，允许模型驱动的多孔电极的优化。作为一个特殊情况，我们考虑用于锂离子电池（LIB）的电极，这对现有的可再生能源战略越来越有技术意义。现有技术的锂离子电池由两个多孔电极（阳极和阴极）组成，执行将锂储存在晶体结构内并将其提供给填充孔隙并用作两个电极之间的离子连接的液体电解质的任务。电子连接由电极和金属集电器提供，其用作到外部电路的端子。结合精确的3D重建和电极的详细建模，可以识别速率限制过程，并可以获得改进的微观结构。为了实现这一目标，一个基本的先决条件是电极微观结构的定量表征和确定其对电化学机制的影响。微结构参数的精确量化是执行基于模型的模拟所必需的，该模拟可用于电极优化。特别地，关于以下过程和相关参数的表征是必不可少的：（a）表面积与体积比和体积分数;（b 1）离子和电子物质在蒸发系统中的传输;（b 2）有效传输参数（迂曲度）;（c1）将锂储存在活性材料的晶体结构中，以及（c2）活性颗粒的分布和尺寸。现有技术方法的主要限制影响所有这些方面，因为它们使用简化的模型，不能达到所有物质相的所需分辨率，并且不使用允许所需多尺度精度的数值方法。特别是，需要一种更精确的定量方法：（a3）获得所需的近似活性表面，（b3）定义是否可以使用有效的参数，以及它们需要确定的精度，（c3）在微观水平上实现必要的近似。在这个项目中，我们将执行一个多尺度的瞬态模型的推导，实施和验证的锂离子电池电极，这将是基于一种方法的部分模型减少，需要的贡献的Intitut für Werkstoffe der Elektrotechnik（IWE）和Institut für Angewandte Mathematik（IAM）。IWE将专注于可靠和原始的方法，用于电极重建，模型和微观结构参数的建模和量化。IAM将专注于数学方法的模型减少和数值解使用高性能计算技术和新的误差估计方法。

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.