Microstructure impact on chemo-mechanical fracture of polycrystalline lithium-ion battery cathode materials.

Anisotropic volume change of layered oxide cathode active material such as Ni-rich nickel–manganese–cobalt-oxide (NMC) during cycling significantly contributes to mechanical degradation, emerging as a primary factor leading to instability issues in these high-capacity cathode active materials for lithium-ion batteries. Despite their commendable energy density, these challenges hinder the broader application of NMC, underscoring the need for rational analysis and innovative solutions to address the associated mechanical instability. In this contribution, we utilize a chemo-mechanically coupled cohesive fracture model, complemented by its 3D finite element implementation, to simulate and analyze the performance and cracking behavior of polycrystalline high-Ni nickel–manganese–cobalt cathode active materials. Thereby the two-way coupling between mechanics and diffusion is regarded both in the bulk and at grain boundary. In particular, novel algorithms are introduced to model the electrolyte penetration along the inter-granular cracks, capturing its intricate impact on particle performance. Utilizing simulations on synthetic and reconstructed microstructure samples derived from experimental images, extensive parameter studies were conducted. These investigations unveiled the intricate influence of various microstructure aspects, encompassing grain morphology, grain/particle sizes, and texture. The findings indicate that secondary active material particles exhibiting smaller grains and radially elongated primary particles, coupled with radially oriented high-diffusivity planes, demonstrate enhanced resistance to inter-granular mechanical damage. • An anisotropic chemo-mechanically coupled model with fracture is developed in 3D. • A novel algorithm is introduced to model electrolyte penetration into the cracks. • Microstructure impact on cracking of polycrystalline cathode material is studied. • Grain size and grain morphology have a significant impact on damage mitigation. [ABSTRACT FROM AUTHOR]