Mechanistic Insights into Electrochemical-Mechanical Coupled Damage of Si-Based Composite Anodes in All-Solid-State Batteries

Abstract

Silicon (Si)-based all-solid-state batteries (ASSBs) are regarded as a highly promising next-generation energy storage technology due to their superior energy density and enhanced safety. However, the significant volume change of Si anodes during Li insertion/extraction leads to possible mechanical damage, severely degrading the cyclability and hindering the commercial application of ASSBs. The underlying damage mechanism of Si-based composite anodes remains unclear. In this study, an electro-chemo-mechanical coupled phase-field model is developed to quantitatively investigate the damage evolution behavior of Si-based composite anodes during charging. It's revealed that the volume expansion of Si particles squeezes the solid electrolytes (SEs) to generate highly concentrated strain and GPa-level stress at the interface, driving the structural damage initiation and propagation. The damaged area occupies over 21% of the SE region by charging end, heavily impeding ion transport pathways and degrading interfacial stability. Increasing the fracture toughness of the SEs effectively delays the damage development, and different SE materials exhibit a trade-off between conductivity and mechanical properties. Furthermore, adopting the decreasing size-gradient distribution of Si particles effectively relieves stress concentration and reduces damage extent. Results elucidate the damage mechanism of Si composite anodes from an electro-chemo-mechanical coupling perspective and provide theoretical guidance for the mechanism-driven design of high-stability Si-based ASSBs.