Blázquez, J. Alberto

Danner, Timo

Drews, Janina

Fichtner, Maximilian

Latz, Arnulf

Maça, Rudi Ruben

Wang, Liping

Wiedemann, Johannes

Zhao-Karger, Zhirong

Institute of Transport Research:Publications

Continuum Modelling as Tool for Optimizing the Cell Design of Magnesium Batteries  Janina Drews1,2, Rudi Ruben Maça Alaluf,3 Liping Wang,2,4 Johannes Wiedemann,1,2 J. Alberto Blázquez,3 Zhirong Zhao-Karger,2,4 Maximilian Fichtner,2,4 Timo Danner,1,2 and Arnulf Latz1,2,5  1German Aerospace Center (DLR), Institute of Engineering Thermodynamics, Stuttgart, Germany 2Helmholtz Institute Ulm for Electrochemical Energy Storage (HIU), Ulm, Germany 3CIDETEC Energy Storage, Basque Research and Technology Alliance (BRTA), Donostia-San Sebastián (Spain) 4Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, Eggenstein-Leopoldshafen, Germany 5University of Ulm, Institute of Electrochemistry, Ulm, Germany Helmholtzstraße 11, 89081 Ulm, Germany janina.drews@dlr.de   Regarding energy density, safety, cost, and sustainability rechargeable magnesium batteries are a very promising next-generation energy storage technology. However, for a successful commercialization of magnesium batteries there are still some challenges to overcome, which are mainly caused by the high charge density of the bivalent cation and the consequential strong coulomb interactions with anions and solvent molecules. For this reason, magnesium salts are prone to form ion pairs and bigger clusters – especially at high concentrations, which may adversely affect the transport in the electrolyte and the electrochemical reaction at the electrode.[1] Moreover, energetic barriers for desolvation and solid-state diffusion of the double-charged magnesium ion are usually very high, which can have a crucial impact on the battery performance. Former can significantly hinder the electron-transfer reaction,[2] whereas latter makes the choice of suitable cathode materials very challenging.  Consequently, a good understanding of the limiting processes in rechargeable magnesium batteries is key to develop novel high-capacity / high-voltage cathode materials. For instance, it is well-known that the morphology of an intercalation material can strongly influence the battery performance and smaller particles as well as thinner electrodes are common strategies for avoiding adverse effects of transport limitations. However, high mass loadings as well as suitable separators are still essential bottlenecks for commercialization of magnesium-ion batteries. Up to date Chevrel phase (CP) Mo6S8 is considered as benchmark intercalation cathode and Mg[B(hfip)4]2 / DME is seen as most promising chloride-free magnesium electrolyte.[3,4]  In our contribution we carefully study this model system of a magnesium-ion battery to get a better understanding of how to overcome undesired limitations for instance by adjusting the battery design. Therefore, we present a newly-developed continuum model, which is able to describe the complex intercalation process of magnesium cations into a CP cathode. The model considers not only the different thermodynamics and kinetics of the two intercalation sites of Mo6S8 and their interplay but also the impact of the desolvation on the electrochemical reactions and possible ion agglomeration. The parameterization and validation of the model is based on DFT calculations and experimental data. Different kind of (transport) limitations and their impact on the battery performance are studied in detail. All in all, the combination of different modelling techniques with experimental measurements provides important insights into the operation of magnesium ion batteries and enables an optimization of the cell design.  Acknowledgements This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 824066 (E-MAGIC). Furthermore, this work contributes to the research performed at CELEST (Center for Electrochemical Energy Storage Ulm-Karlsruhe) and was funded by the German Research Foundation (DFG) under Project ID 390874152 (POLiS Cluster of Excellence). The simulations were carried out at JUSTUS 2 cluster supported by the state of Baden-Württemberg through bwHPC and the German Research Foundation (DFG) through grant No INST 40/575-1 FUGG.   References 1. J. Drews, T. Danner, P. Jankowski et al., ChemSusChem, 3 (2020), 3599-3604. 2. J. Drews, P. Jankowski, J. Häcker et al., ChemSusChem, 14 (2021), 4820-4835. 3. D. Aurbach, Z. Lu, A. Schlechter et al., Nature, 407 (2000), 724-727. 4. Z. Zhao-Karger, R. Liu, W. Dai et al., ACS Energy Lett. 3 (2018), 2005-2013. 

Continuum Modelling as Tool for Optimizing the Cell Design of

Magnesium Batteries

https://elib.dlr.de/191765/1/MagBattIV_Abstract_EMAGIC_DLR-CEC_JaninaDrews.pdf

Continuum Modelling as Tool for Optimizing the Cell Design of Magnesium Batteries

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