Anisotropic fracture-diffusion modeling of void-crack interaction and parallel crack patterns in single-crystal cathode particles

This is the authors' abstract. We don't add key points for this paper.

Intragranular cracks and voids are recognized as key defects limiting the structural stability of anisotropic single-crystal cathode particles. The observed distinct crack pattern, featuring parallel non-coplanar cracks and disconnected coplanar cracks, is closely related to the anisotropic material properties and the interaction between different types of defects, which remains insufficiently understood. Hence, this study develops an anisotropic diffusion-stress-fracture phase-field model to systematically investigate void-crack interaction mechanisms in single-crystal particles containing multiple voids. We find that when the propagation of the primary crack is confined to a specific crystallographic plane, secondary cracks may nucleate at the void edge on other crystallographic planes due to void-crack stress interactions. We reveal three distinct void-crack interaction modes, i.e., fully activated mode (the secondary crack is activated by the primary crack and propagates dominantly), partially activated mode (the secondary crack is activated by the primary crack but propagates minimally before arresting), and inactivated mode (the secondary crack is not activated). The fundamental difference among these modes lies in the competition between the driving forces of the primary and secondary cracks. Based on this understanding, we have successfully reproduced the formation process of the parallel-crack and disconnected-crack patterns observed in the experiments, confirming the critical role of void-crack interactions in particle degradation. Further, we demonstrate that fracture anisotropy acts as the key factor in distinctive phenomenon of parallel crack propagation. This finding provides new insight beyond the conventional “void-induced crack deflection” scenario predicted by isotropic models, thereby advancing the understanding of void-crack interaction mechanisms.