Evaluation of the ionic conductivity of cation electrolytes by Kinetic Monte Carlo simulations
Computer-Aided Design of Materials and Simulation of Materials Behaviour from Atomic to Microscopic Scale
Physical Chemistry of Solids and Surfaces, Material Characterisation
Final Report Abstract
Batteries and fuel cells enable the efficient conversion and storage of electrical energy and are therefore a central component of a successful energy transition. For solid oxide fuel cells and solid-state batteries, the ceramic electrolytes used play a decisive role. The introduction of new electrochemical cells with enhanced performance and reduced costs is thus not feasible without the use of optimized ion conductors. In the past, a wide range of materials has been investigated regarding their suitability as solid electrolytes. However, comprehensive experimental characterization of these materials is limited by the time and cost involved on the one hand, and the vast number of possible structures and compositions on the other. At the atomic level, the properties of solids can be described using density functional theory (DFT). The number of such calculations has increased significantly in recent years due to growing computational capacities. The resulting parameters can be used in kinetic Monte Carlo simulations to determine ionic conductivity. This allows the energies and processes at the microscopic level to be linked to macroscopic ion transport. The aim of this project was to simulate the cationic conductivity of selected solid electrolytes using density functional theory and kinetic Monte Carlo methods. Based on structures and energy parameters from the literature, simulations were carried out to determine the conductivity. Initially, promising cation conductors (for H⁺, Li⁺, and Na⁺) were identified and relevant energy parameters collected. From the literature review, two structure types were selected for further investigation: perovskites for H⁺ conduction and NASICON materials for Li⁺ and Na⁺ conduction. Based on extracted energy models, kinetic Monte Carlo simulations were performed as a function of composition and temperature. The results were compared with experimental findings and molecular dynamics simulations. In summary, it can be stated that the Monte Carlo simulations show good agreement with experimental data in terms of the observed trends. On the other hand, it should be noted that published energy parameters for a given material can vary significantly depending on the source, and experimental conductivity data also exhibit a wide range. This complicates both the consistent selection of energy parameters from the literature and the comparison with experimental results.
Publications
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A review of proton migration and interaction energies in doped barium zirconate. Solid State Ionics, 397, 116231.
Winterhoff, Giulia & Neitzel-Grieshammer, Steffen
