Phase-Field Computational Framework for Addressing Challenges in Solid-State Batteries

All-solid-state batteries are attracting increasing interest due to their higher promised energy densities without the use of flammable liquid electrolytes. Two main challenges for solid-state batteries are contact loss and interphase formation; these play a central role in the quality of the solid-electrolyte–electrode interfaces. Here, we present a modular phase-field modeling framework that is generally applicable to solid-state batteries with different electrodes and corresponding microstructures. The model is based on multiphase porous electrode theory, where Li-ion diffusion in solid electrolytes and electrode materials is integrated through a regular solution free energy functional. Modules for contact loss and diffusive interlayers, able to capture solid-solid and solid-liquid interfaces such as solid-electrolyte interphase formation and coatings, are also implemented, providing numerous modeling options for a comprehensive understanding of electrochemical systems. A thorough comparison between the solid-state and conventional liquid-electrolyte models for phase-separating electrodes reveals the optimal conditions and bottlenecks of solid-state diffusion and failure mechanisms. The predictions underline contact loss and interphase formation as the crucial mesoscopic morphological characteristics of solid-state systems, setting the basis for in-depth understanding and optimized performance in all-solid-state batteries.