3D simulation of sodium-iodine secondary batteries for stationary energy applications


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High-temperature liquid sodium batteries (e.g. sodium-sulfur) are a well-established technology for large-scale grid storage. Combining the molten sodium anode with an aqueous iodine cathode overcomes the problems of thermal loses and sealing by reducing the operating temperature to about 100°C.
This leads to higher cost efficiency, energy density and a simplified cell design. Due to their sustainability and high efficiency, which is comparable to Li-Ion –batteries, mid-temperature sodium-iodine batteries are a promising candidate for small and medium scale stationary energy storage applications [1]. They have the ability to meet the growing demand of short-term energy storage caused by the integration of renewable energy sources into the power grid.
Although sodium-iodine batteries are theoretically described in literature, the detailed processes inside the battery are not well understood [2]. Quantities like initial species concentrations, C-rate, cell design and cathode geometry have large impacts on the overall battery performance. As experimental studies are limited to macroscopic quantities like electronic current and potential a fully resolved 3D Simulation model is set up to gain insight into microstructural processes inside the battery [3].
The presented spatial resolved three-dimensional model takes mass transport, heterogeneous and homogeneous reactions as well as the electrochemical processes into account. A deeper understanding of these processes is inevitable for enhancing the battery performance by choosing the optimal above-mentioned quantities. In this contribution the capability of the model on predicting cell performance is shown. It highlights key findings of our latest research [3]. The focus is on the correlation between the molar species distribution in the catholyte and the extent of the cathode compartment regarding the battery operating limits.

[1] M. Holzapfel, D. Wilde, C. Hupbauer, K. Ahlbrecht, T. Berger, Electrochimica Acta 237 (2017) 12–21. https://doi.org/10.1016/j.electacta.2017.03.152.
[2] H. Zhu, R.J. Kee, Electrochimica Acta 219 (2016) 70–81. https://doi.org/10.1016/j.electacta.2016.09.104.
[3] F. Gerbig, S. Cernak, and H. Nirschl, “3D Simulation of Cell Design Influences on Sodium–Iodine Battery Performance,” Energy Technol., p. 2000857, 2021, doi: 10.1002/ente.20200085759.

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