Microstructure design and multiphysics optimization of composite cathodes for high-energy solid-state lithium-ion batteries

Solid-state lithium-ion batteries (SSLBs) offer high energy density and enhanced safety; however, their performance and reliability remain constrained by coupled stress localization and thermal accumulation. Here, a physics-based three-dimensional heterogeneous particle model is developed, with microstructures constructed using a simulated annealing (SA) algorithm that minimizes a multi-objective energy function incorporating particle overlap, boundary constraints, and porosity. The optimization is constrained by experimentally derived material descriptors, thereby preserving intrinsic microstructural heterogeneity. The resulting microstructures are embedded into an enhanced pseudo-two-dimensional framework for electrochemical-mechanical-thermal (EMT) coupling with explicit microstructural resolution. For cell-level calibration, a 0.1 mA galvanostatic discharge profile was measured using an NMC811/LLZO/Li coin cell. The globally calibrated random-arrangement (RA) response reproduces the measured voltage trajectory with a Pearson correlation coefficient of 0.99998 and an RMSE of 1.1 mV over normalized discharged capacity from 0.02 to 0.98. The RA prediction of 86.10% also agrees with the retained experimental 1C/0.5C capacity retention of 86.57%. Without architecture-specific refitting, the predicted retention increases to 88.43% for the optimized arrangement and 91.62% for the compacted optimized arrangement. The compacted architecture also delivers a higher discharge-voltage plateau and increased volumetric energy density while maintaining limited stress and temperature rise. These results establish a physics-informed route for microstructure design that couples cell-level electrochemical calibration with prospective architecture optimization.