Multi-failure mode characterization and low-cycle fatigue assessment of Si C core–shell particles in the lithium-ion battery

Abstract

Si C composites are considered potential anode materials due to better cycling stability, compared to pure silicon. However, severe volume expansion of Si during cycling results in various failure forms of Si C particles, exposing the Si core to the electrolyte, generating Solid-Electrolyte Interface (SEI) films, and consuming lithium-ions in the electrolyte solution. In this paper, a coupled mechanical-chemical model is developed to analyze different failure modes of the particle during the charge and discharge cycle. Besides, the Direct Steady Cyclic Analysis (DSCA) under the Linear Matching Method (LMM) framework is utilized to evaluate the fatigue damage at the critical location of the particle. With the C shell thickness increased, the particle is more prone to debonding failure between the Si core and C shell, while a thicker C shell can mitigate the volume expansion of the Si core and alleviate fatigue damage in the C shell. This study also establishes a threshold size to identify the significant acceleration of low-cycle fatigue damage, which provides theoretical guidance for particle design.