A New Three-Dimensional Microstructure-Resolved Model to Assess Mechanical Stress in Solid State Battery Electrodes

In all-solid-state batteries (ASSBs), the mechanical stress generated during electrode (de)lithiation plays a critical role in determining the cell longevity because of the induced degradation mechanisms. This stress originates from local volume fluctuations in the active electrode materials, which are intrinsically coupled to spatial variations in lithium-ion concentration during electrochemical cycling. The local volume change of certain active materials, such as nickel-rich LiNixMnyCozO2, significantly varies with the lithium content, which should be considered in the stress calculations in the ASSB modeling studies. In this work, we present a novel ASSB model that considers electrochemistry and solid mechanics in a one way coupled manner. The model spatially resolves the three-dimensional microstructure of an ASSB half-cell generated from wet manufacturing process simulations and is based on linear continuum mechanics. The coupling of electrochemistry and solid mechanics is incorporated via lithiation-dependent volumetric changes of the active materials and the microstructural changes due to deformed geometries affecting the particles percolation paths. Furthermore, we show that the overall volume change of the half-cell is dependent on the C-rate and on the applied stack pressure. Finally, our findings demonstrate that solid-mechanical effects and their interplay with electrochemical phenomena significantly impact the evolution of interfacial surface area and the total pore volume. These factors are crucial for ensuring accurate computational predictions, underscoring the necessity of incorporating such interactions in battery modeling approaches.