Optimizing the Composite Cathode Microstructure in All‐Solid‐State Batteries by Structure‐Resolved Simulations

Abstract

All‐solid‐state batteries are considered as an enabler for applications requiring high energy and power density. However, they still fall short of their theoretical potential due to various limitations. One issue is poor charge transport kinetics resulting from both material inherit limitations and non‐optimized design. Therefore, a better understanding of the relevant properties of the cathode microstructure is necessary to improve cell performance. In this article, we identify optimization potentials of the composite cathode by structure‐resolved electrochemical 3D‐simulations. In our simulation study, we investigate the influence of cathode active material fraction, density, particle size, and active material properties on cell performance. Special focus is set on the impact of grain boundaries on the cathode design. Based on our simulation results, we can predict target values for cell manufacturing and reveal promising optimization strategies for an improved cathode design.

Influence of Electrode Structuring Techniques on the Performance of All‐Solid‐State Batteries

“…Reducing the CAM fraction to 60 vol % (L 60 ) significantly enhances the effective ionic conductivity at still a substantial CAM fraction. [15,19] To assess the potential of the two-layer design in enhancing cell performance, we adjust the thickness of each layer, denoted by d L60 and d L70 , respectively, while maintaining a constant overall cathode thickness.…”

“…An effective way for reducing tortuosity in the SE is to increase SE fractions in the cathode. [15,19,22] However, this comes at the cost of diminished CAM fractions, resulting in a reduced energy density. Moreover, cathode void volume must be minimized, as voids lead to limitations of ionic transport, especially at elevated CAM fractions.…”

“…[13,27,28] However, a high ratio between CAM and SE particle size can lead to transport limitations due to a higher number of grain boundaries in the SE and longer diffusion pathways in the CAM. [19,20,29,30] These considerations impose inherent trade-offs, limiting the potential of structural optimization of homogeneous composite cathodes for improved cell performance. However, electrode structuring techniques can address some constraints in homogeneous cathodes.…”

“…In a recent study, we employed 3D continuum simulations to examine the effect of cathode composition, particle size, and cathode density on the electrochemical cell performance of homogeneous ASSB composite cathodes. [19] Building on this, the current work applies the same structureresolved simulation approach to investigate the benefits of cathode structuring on cell performance. We investigate a perforated and two-layer cathode concept, which can potentially mitigate ionic transport limitations in high-energy electrodes.…”

“…Recently, experimental and simulation studies have focused on optimizing composite cathode microstructure for improved cell performance. [15][16][17][18][19][20][21][22][23][24][25] Ionic conductivity in the cathode can be increased by reducing effective tortuosity in the SE phase. An effective way for reducing tortuosity in the SE is to increase SE fractions in the cathode.…”