Impact of grain orientation architecture and boundary properties on chemo-mechanical cracking in NMC811 particles

Performance and lifetime of lithium-ion batteries are severely limited by fracture evolution in polycrystalline NMC811 particles. Yet, the roles of grain misorientation and microstructural architecture in governing both damage evolution and electrochemical response remain poorly quantified. We develop a stress-based, fully coupled phase-field framework that links lithium transport, mechanical equilibrium, damage evolution with fabrication-induced heterogeneity captured by a Weibull distribution of local strengths along grain boundaries. Simulations spanning grain size, C-rate, grain-to-boundary strength ratio, and orientation architecture reproduce experimentally observed intergranular and intragranular crack morphologies and reveal clear trends: higher misorientation elevates boundary tractions, accelerates failure, and promotes faster open-circuit voltage (OCV) evolution; and higher C-rates drive mixed fracture, with the dominant mode governed by the grain-to-boundary strength ratio. Orientation architecture is also decisive: a radial texture with low-misorientation shells and high-misorientation cores suppresses surface crack nucleation, confines damage to the interior, preserves electrochemical connectivity, and results in more gradual OCV evolution, whereas random placement of highly misoriented grains produces more pervasive cracking and shorter charging/discharging duration. These results provide compact guidelines for mitigating particle fracture and controlling electrochemical behavior through grain misorientation engineering, boundary strengthening, and co-optimization of grain size and operating conditions.