Quantitative in situ fracture testing of tin oxide nanowires for lithium ion battery applications

Highlights: • Lithiation can reduce the fracture strength and Young's modulus of SnO₂ nanowires. • Lithiation can lead to obvious plastic deformation with structural transition. • A model was established for predicting the mechanical behaviors of SnO₂ nanowires. SnO₂ is considered as a promising anode material in lithium-ion batteries (LIBs). However, limited work has been focused on tensile mechanical properties and fracture mechanisms of lithiated and delithiated SnO₂-based nanomaterials, which is of critical importance for the reliability of LIBs. In this study, in-situ tensile test performed in scanning electron microscope is employed to quantitatively study the tensile fracture of these electrochemically modified SnO₂ nanowires (NWs). It is found that the lithiation-delithiation processes can cause a phase transition from crystalline to composite structure, leading to an obvious increase in fracture strain accompanied by plastic deformation, as compared to pristine SnO₂ NWs. Meanwhile, the fracture strength and Young's modulus of SnO₂ NWs were dramatically reduced. Interestingly, mechanical properties of delithiated SnO₂ NWs are generally higher than those of lithiated ones. A finite element model was established based on a linear elastic-to-plastic hardening law to predict the tensile mechanical behaviors of lithiated and delithiated SnO₂ NWs. The fitting results are in good agreement with experimental data. This work provides a basic understanding of mechanical characteristics of SnO₂-based nanomaterials for LIBs applications.