Fracture toughness of LixSi alloys in lithium ion battery

Abstract eng:
A fundamental understanding of the fracture toughness of the LixSi alloys is crucial for the rational design of Si based high-capacity and failure-resistant electrodes. In this study, a chemo-mechanical model, which involves the bi-directional strong coupling between lithiation kinetics and stress, is adopted to demonstrate that the classic Rice's J—integral becomes path-dependent when both chemical and mechanical driving forces are present concurrently. However, our newly proposed electro-chemo-mechanical J-integral is shown to be path-independent under such combined multiple driving forces when the electrodes undergo large lithiation-induced elasto-plastic deformation. Based on the algorithm of the path-independent electro-chemo-mechanical J—integral, molecular dynamics (MD) simulations are conduced to investigate the fracture toughness of LixSi alloys. Good agreement is achieved between the obtained results and the limited published data derived from the experimental measurements. According to the calculated fracture toughness, the critical sizes of different Si anode nanostructures are finally discussed.

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