A theoretical study of lithium absorption in amorphous and crystalline silicon

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Abstract
Lithium absorption in silicon is studied at the DFT level. By means of the developed method of modeling the structure of amorphous silicon, including with impurities, it is shown that with an increase in the lithium concentration intermediate amorphous Li x Si y phases, up to the crystalline Li15Si4 phase, form in crystalline silicon. An increase in the silicon cell volume, as it is filled with lithium, is calculated. A nonlinear dependence of silicon voltage on lithium intercalation is found. The lithium diffusion coefficient in crystalline silicon at a low lithium concentration is calculated and it is demonstrated for amorphous silicon that lithium diffusion is substantially accelerated by the lattice deformation inherent in amorphous silicon. The calculated values can be used in the production of high-capacity lithium ion batteries with a silicon anode.

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