Fracture Toughness of LixSi Alloys in Lithium Ion Battery

Abstract

Fundamental understanding of the fracture toughness of the LixSi alloys is crucial for designing of Si based high-capacity and failure-resistant electrodes. In this study, molecular dynamics simulation informed continuum chemo-mechanical modelings with conservation integrals were conducted to derive fracture toughness of LixSi alloys. Our modeling results show reasonable agreement with available experimental data, revealing that the fracture toughness of LixSi alloys with low lithium concentration does not vary significantly with lithium concentration. In addition, we demonstrated that, if lithium redistribution caused by the stress gradient around crack tip needs to be considered, an appropriate chemo-mechanical path-independent J-integral should be used as the classic Rice's J-integral is path-dependent. The obtained fracture toughness of the LixSi alloys here provides guidance for the rational design of Si based electrodes, and the presented approach also sheds light for the evaluation of the fracture toughness of other energy materials at different charging/discharging levels.