Atomistic observation of the lithiation and delithiation behaviors of silicon nanowires using reactive molecular dynamics simulations
- Atomistic observation of the lithiation and delithiation behaviors of silicon nanowires using reactive molecular dynamics simulations
- Silicon nanowire; Lithiation; Delithiation; Reactive force field; Molecular dynamics simulation
- Issue Date
- 대한화학회 추계총회
- For the practical use of silicon nanowires (Si NWs) as anodes for Li-ion batteries, understanding their lithiation and delithiation mechanisms at the atomic level is of critical importance. We discuss the mechanisms for the lithiation and delithiation of Si NWs determined using a large-scale molecular dynamics (MD) simulation with a reactive force field (ReaxFF). The ReaxFF is developed using results from first-principles calculations for various crystals and molecules. During the lithiation process, Li atoms penetrate into the lattices of the crystalline Si (c-Si) NWs preferentially along the <110> or <112> direction, and then the c-Si changes into amorphous LixSi (a-LixSi) phases due to the simultaneous breaking of Si-Si bonds as a result of the tensile stresses between Si atoms. Before the complete amorphization of the Si NWs, we observe the formation of silicene-like structures in the NWs that are eventually broken into low-coordinated components, such as dumbbells and isolated atoms. Additionally, during delithiation of LixSi NWs, we observe the formation of a small amount of c-Si nuclei in the a-LixSi matrix below a composition of Li1.4Si ~ Li1.5Si, and we demonstrate that the two-phase structure can be thermodynamically more favorable than the single-phase a-LixSi.
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