Reactive flow in silicon electrodes assisted by the insertion of lithium.
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In the search for high-energy density materials for Li-ion batteries, silicon has emerged as a promising candidate for anodes due to its ability to absorb a large number of Li atoms. Lithiation of Si leads to large deformation and concurrent changes in its mechanical properties, from a brittle material in its pure form to a material that can sustain large inelastic deformation in the lithiated form. These remarkable changes in behavior pose a challenge to theoretical treatment of the material properties. Here, we provide a detailed picture of the origin of changes in the mechanical properties, based on first-principles calculations of the atomic-scale structural and electronic properties in a model amorphous silicon (a-Si) structure. We regard the reactive flow of lithiated silicon as a nonequilibrium process consisting of concurrent Li insertion driven by unbalanced chemical potential and flow driven by deviatoric stress. The reaction enables the material to flow at a lower level of stress. Our theoretical model is in excellent quantitative agreement with experimental measurements of lithiation-induced stress on a Si thin film.
author list (cited authors)
Zhao, K., Tritsaris, G. A., Pharr, M., Wang, W. L., Okeke, O., Suo, Z., Vlassak, J. J., & Kaxiras, E.
complete list of authors
Zhao, Kejie||Tritsaris, Georgios A||Pharr, Matt||Wang, Wei L||Okeke, Onyekwelu||Suo, Zhigang||Vlassak, Joost J||Kaxiras, Efthimios