Optimised Electrodes for Solid-State Batteries

Using transport simulations, researchers of a collaboration between Helmholtz Institute Münster, the University of Münster and the International Graduate School BACCARA are now able to predict the transport properties of all-solid-state battery electrodes.

12 March 2024 – Solid-state battery electrodes are often composite materials of solid ion-conductors and active electrode materials. The effective transport of charge carriers and heat are key factors that determine the overall performance and safety of the battery. Researchers from Helmholtz Institute Münster (HI MS; IMD-4) at Forschungszentrum Jülich, in collaboration with the University of Münster and BACCARA International Research School, are now presenting a resistor network model that successfully describes the transport phenomena in composite materials for solid-state batteries.

Resistance Network Model Presented

The phase space for optimising the composition of solid electrolyte, active material and additive is relatively large and therefore difficult to capture experimentally. A team led by Prof. Dr Wolfgang Zeier, who works at Helmholtz Institute Münster, the University of Münster and the BACCARA research school, is now presenting a resistor network model that successfully describes the transport phenomena in solid-state battery electrodes.

“In the simplest case, electrode composites consist of only two components – a solid ionic conductor and the active material. The mixing ratio of these components and the microstructure of the mixture, significantly influence the transport properties of the solid electrode,” explains Lukas Ketter, who is doing his doctorate at BACCARA.

Both the influence of the microstructure and that of the mixing ratio on the transport properties can now be simulated. The simulation results can then be compared with experimentally determined conductivities and provide helpful support in data interpretation.

Easy Access

Transport properties always change when the composition or microstructure of a mixture is varied. It is very cost and time intensive to determine these properties experimentally for each variation. The new model enables simulations that make simple predictions about the transport properties, which can support data interpretation and optimise electrodes. The model stands out from previous approaches due to its simple structure and easy accessibility. Only a few parameters are needed as input and the code is freely accessible under an open source licence.

Knowledge of Heat Transport Is Crucial

High electron and ionic conductivities in solid-state electrodes are crucial for the battery performance. After all, the charge carriers are needed for the electrode reaction. If the charge transport is particularly slow, in addition to the high internal resistance of the electrode, inhomogeneous charging and discharging reactions can occur, which deteriorates performance.

At elevated temperatures, degradation reactions in electrode composites are also accelerated. At very high temperatures, these degradation reactions can be particularly severe and can cause a short circuit. Since batteries heat up during charging and discharging due to Joule heating or for high-power applications, such as electric vehicles, a thermal management is always developed. To optimise this, knowledge of the heat transport of the materials is crucial.

Project SAFE

The work is part of the SAFE project (“Thermische Sicherheitsanalytik von sulfidischen Festkörperbatterien”, English “‘Thermal Safety Analysis of Sulfide Solid-State Batteries”), which is embedded in the FestBatt2 competence cluster for solid-state batteries. The project offers scientists the opportunity to network across different working groups in Germany and thus advance the improvement of solid-state batteries.

Study Published in the Journal Nature Communications

The researchers Lukas Ketter, International Research School BACCARA and Institute for Inorganic and Analytical Chemistry at the University of Münster, Niklas Greb, University of Münster, Dr. Tim Bernges, University of Münster and Prof. Dr Wolfgang Zeier, BACCARA, University of Münster and Helmholtz Institute Münster (HI MS; IMD-4) at Forschungszentrum Jülich, as an open access article in the journal Nature Communications.