Role of Plasticity in Mechanical Failure of Solid Electrolyte Interphases on Nanostructured Silicon Electrode: Insight from Continuum Level Modeling

Understanding the failure mechanisms of solid electrolyte interphases (SEI) is important for silicon electrodes because their volume expands substantially during lithiation. This work discusses material point method simulations of SEI failure during lithiation of silicon nanopillars. We demonstrate that considering SEI films as brittle, elastic materials does not allow fracture that would be consistent with experimental observations. However, constitutive models that include plastic deformation and result in ductile fracture are in very good agreement with trends observed in experiments. The insight gained from these results allows suggestion of possible strategies for design of SEI with improved failure resistance under lithiation-induced electrode expansion, where modification of the SEI leading to increased Young's modulus and/or strain hardening without compromising the underlying ductility of the material presents a desirable outcome for chemical and/or processing modifications designed to modify SEI response.