Fracture Analysis of Polycrystalline NCM Electrode Particles under External Pressure with Varying Pressurized Coverage

Nickel-rich cathode materials (LiNi_1−x−yCo_xMn_yO₂, NCM) are regarded as one of the most promising cathode candidates for solid-state batteries (SSBs) due to their high energy density and low cost. However, during electrochemical cycling, continuous lithium-ion insertion/extraction generates diffusion-induced stress (DIS) that fractures particles and accelerates capacity fade. Furthermore, NCM particles are subjected to external pressure during manufacturing, and inherent process non-uniformities result in varying pressurized coverage (defined as the ratio of covered area of active materials with solid-state electrolytes), which significantly influence particle cracking behavior. Based on chemo-mechanical coupling models, extensive work have investigated particle cracking behavior during charge-discharge processes. While limited research addressing crack evolution under concurrent electrochemical loading and external pressure. Thus, we developed a chemo-mechanical coupling model with globally embedded cohesive elements within polycrystalline NCM (PC-NCM) particles to simulate fracture behavior during single charge-discharge cycles. The effects of external pressure, charge/discharge C-rate and pressurized coverage are evaluated. Simulations demonstrate that external pressure significantly mitigates particle cracking. Notably, this crack-suppression effect intensifies with reduced pressurized coverage. This work provides critical insights into fracture mechanisms of NCM cathodes materials, offering fundamental guidance for electrode design optimization.