Microstructure-Resolved Battery Simulation Using the Lattice Boltzmann Method

Kurzfassung

Lithium-ion batteries (LIB) and post-lithium-ion technologies such as metal-sulfur batteries (MSB) are promising for energy storage in mobile applications and e-mobility. While LIB are technically matured and currently lead in trade-offs considering cost and performance, the upcoming post-lithium-ion technologies show great potential with respect to higher energy densities at reduced costs. Beside the different technological readiness of LIB and MSB, the great difference is where current research activities for each technology are focused on. For MSB the investigations focus on more fundamental questions regarding chemical and electrochemical processes as well as degradation phenomena during battery operation. LIB technology is more mature and a significant part of the research already focuses on the optimization of the manufacturing process. However, improving both requires a detailed understanding of pore-scale phenomena in the battery microstructures and how these affect the cell level. Therefore, in our research, we developed a mesoscopic computational approach based on the lattice Boltzmann method (LBM) which can be used to study multi-physics issues in realistic and highly resolved battery microstructures. Using this method, for LIB the manufacturing step of electrolyte filling under the influence of structural and physico-chemical properties and their effect on electrolyte and gas distributions at the end of the filling was studied. In contrast, for MSB the new model was applied to study multi-species transport phenomena such as the polysulfide shuttle as well as chemical and electrochemical reactions including dissolution and precipitation. The results aid in both optimization and design of, e.g., battery microstructures to improve the filling process, cyclability and battery operation. It is also shown how residual gas from the filling, but also pore clogging by precipitates can adversely affect the battery performance. In this context, temporal varying diffusion pathways, reduced effective transport properties and passivated reaction surfaces are discussed and it is shown how they lead to capacity losses in both LIB and MSB. The present work shows the applicability of the LBM model for battery research. The model reproduces two-phase flow and complex diffusion and reaction dynamics. It can be used to study phenomena in LIB and MSB microstructures on the pore scale. Thus, the methodology proposed here is helpful for designing electrodes, electrolytes, and processes. It is universal and can be generally applied to other battery components or energy storage devices, too. This work has been funded by European Union’s Horizon 2020 research and innovation programme within the research project DEFACTO under grant agreement Nº875247. The simulations were carried out on the Hawk at the High Performance Computing Center Stuttgart (HLRS) under the grant LaBoRESys, and on JUSTUS 2 at the University Ulm under the grant INST 40/467-1 FUGG.