Phase-field analysis of the effects of particle size, diffusivities, and mechanical properties on the cracking of silicon nanoparticle

In this study, a multiphysics model that reproduces the cracking of Si nanoparticle for a battery application was demonstrated. Two types of cracks appear on Si nanoparticle during lithiation. An essential condition for surface crack (SC) nucleation and propagation is a fast charging rate to form a high concentration gradient of lithium ions near the surface. A slower charging rate induces internal cracks (ICs) radiating from the center of the particle. The critical charging rates, at which SC or IC occurs, decrease rapidly with increasing particle radius. This indicates the difficulty of cracking of small nanoparticles, which is in a good agreement with the previous experimental results. Multiple cracks can appear in the particle, especially when the diffusivity is high. These cracks can be combined during the charging process, leading to the fracture or isolation of the particles. Additionally, two different peak stresses and Young's moduli from the literature were used considering their effects on the cracking of Si nanoparticle films. We believe our results provide a guideline for the fabrication and operation of Si nanoparticle-based anodes for lithium ion batteries.