Molecular dynamic investigation of the structure and stress in crystalline and amorphous silicon during lithiation
S Chen and AJ Du and C Yan, COMPUTATIONAL MATERIALS SCIENCE, 183, 109811 (2020).
Silicon (Si) is a promising anode material for lithium-ion batteries with a high specific capacity, but the severe volume expansion and mechanical stress generated during electrochemical cycling hinders its practical application. Considering the coupled effect between electrochemical reaction and mechanical stress, the structure and stress evolution in lithiated crystalline and amorphous Si was investigated using molecular dynamics simulation. The results show that the lithiation in both crystalline and amorphous Si is featured by the shift of the phase boundary. Lithiation is favoured along < 1 1 0 > crystallographic orientation in crystalline Si due to the atomic channels along this direction. The lithiation induced compressive stress is accumulated at the Si-Li phase boundary of crystalline Si and reaches -6 GPa, which slows down the lithiation process. On the other hand, the stress in amorphous Si can be mitigated through deformation at the phase boundary, and the lithiation speed is higher than that in crystalline Si. The lithiation in crystalline Si is related to a peeling-off mechanism, and Si clusters form and disintegrate during lithiation. More Si clusters are generated during the lithiation in crystalline Si than in amorphous Si.
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