S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Chemical and Biological Engineering (화학생물공학부) Journal Papers (저널논문_화학생물공학부)
Anisotropic Volume Expansion of Crystalline Silicon during Electrochemical Lithium Insertion: An Atomic Level Rationale
- Jung, Sung Chul; Choi, Jang Wook; Han, Young-Kyu
- Issue Date
- Nano Letters, Vol.12 No.10, pp.5342-5347
- Lithium-ion battery; silicon anode; anisotropic volume expansion; density functional calculation; interfacial energy; molecular dynamics
- The volume expansion of silicon is the most important feature for electrochemical operations of high capacity Si anodes in lithium ion batteries. Recently, the unexpected anisotropic volume expansion of Si during lithiation has been experimentally observed, but its atomic-level origin is still unclear. By employing first-principles molecular dynamics simulations, herein, we report that the interfacial energy at the phase boundary of amorphous LixSi/crystalline Si plays a very critical role in lithium diffusion and thus volume expansion. While the interface formation turns out to be favorable at x = 3.4 for all of the (100), (110), and (111) orientations, the interfacial energy for the (110) interface is the smallest, which is indeed linked to the preferential volume expansion along the (110) direction because the preferred (110) interface would promote lithiation behind the interface. Utilizing the structural characteristic of the Si(110) surface, local Li density at the (110) interface is especially high reaching Li5.5Si. Our atomic-level calculations enlighten the importance of the interfacial energy in the volume expansion of Si and offer an explanation for the previously unsolved perspective.
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