3D Simulation of Cell Design Influences on Sodium–Iodine Battery Performance

Abstract

This publication deals with the spatially resolved simulation of a sodium–iodine secondary battery. The anode compartment consists of molten sodium and the cathode compartment contains a high‐conductivity metal disc as electrode and an aqueous catholyte. The latter comprises iodide, triiodide, dissolved iodine, and sodium ions. A finite volume approach is proposed to model the transport processes and electrochemical reactions focusing on the positive half‐cell. The study investigates the influences of cathode length, C‐rate, electric conductivity, and molar concentrations on cell performance. It considers solubility limits and predicts diffusion limitation as the major constraint for the operating window. The presented investigations are confined to a simple cathode geometry. However, the results demonstrate the capability of the model to design sodium–iodine half‐cells.

Simulating the Impact of Glassy Carbon Foam Electrodes on the Performance of Sodium Iodine Batteries

“…Comparison between simple and three-dimensional foam cathode design.-Former studies used a two-dimensional cathode design to investigate various influences on the overall battery performance of the sodium iodine battery. 5 A vertically placed, round-shaped titanium disc served as cathode structure. Despite its simplicity, the main shortcoming of this design is that the electrode surface is constrained to a small area in the cathode compartment.…”

“…4 Previous work extends their one-dimensional model to three dimensions with the necessary additions. 5 The present study fully resolves the positive electrode with a three-dimensional simulation because there, the chemistry and thermodynamic constraints are the most complex and the geometry has a decisive influence on the overall battery performance. The negative half cell solely contains of molten sodium which does not influence the cell voltage and battery performance much because of its high conductivity.…”

“…The numerical solver is an adaption from a previously developed lithium-ion battery solver 21,22 to describe the sodium iodine battery. 5 Figure 1 illustrates the sodium iodine battery working principle. The chemical reaction directions are shown for the discharging process.…”

“…3,4 Numerical investigations have indicated transport limitation as the major restriction for the overall battery performance. 5 To overcome these limitations, an improved cathode electrode structure needs to provide a large surface area for the surface reactions inside the battery maintaining a high porosity to achieve sufficient energy capacities and resource efficiency of the battery system. Three-dimensional electrodes are commonly used to surmount transport limitations in two-dimensional electrodes in electrochemical processes.…”

Redox catalysis-promoted fast iodine kinetics for polyiodide-free Na–I2 electrochemistry

“…[1][2][3][4] Due to the earth abundance of the elements and their two-electron redox reactions, rechargeable Na-I 2 batteries, which are cost-effective and have high energy density, have been gaining increasing attention. [5][6][7][8][9] However, the formation of soluble intermediates, particularly NaI 3 , is still inevitable during the iodine sodiation/desodiation reaction: I 2 4 NaI 3 4 NaI, leading to the incorrigible polyiodide redox shuttling in the iodine cathode. 5,6,[10][11][12] Meanwhile, the sluggish redox kinetics of polyiodide translate to the non-reusability of nearly 33% of the I À species, as well as a limited rate capability and inferior life cycle.…”