Electron Transport and Electrolyte Reduction in the Solid-Electrolyte Interphase of Rechargeable Lithium Ion Batteries with Silicon Anodes
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2016 American Chemical Society. Understanding the molecular processes that lead to the formation, structure, and transport properties of the solid electrolyte interphase (SEI) found in lithium ion batteries with silicon anodes is of paramount importance for the development of lithium ion batteries (LiB) capable of performing under the extreme exigencies of our present energy needs that are solved presently with nonrenewable energies. We use a combined density functional theory (DFT) and Green's function approach (DFT-GF) to study the electron transport characteristics in selected finite models of materials formed at the SEI located between the silicon surface of the anode of Li-ion batteries and the electrolyte solvent. The SEI products examined are lithium carbonate (LiCO3) silicon oxide (SiO2) and lithium disilicate (Li2Si2O5). Results show that the leakage of electrons from the Si anode to the solvent is greatly reduced (up to 4 orders of magnitude) with the addition and growth of the SEI components as compared with the solvent-anode sample where no SEI is present. Moreover, we find that at a charging voltage of 2 V, the electron leakage current decays exponentially with the length, decaying up to 3 orders of magnitude at about 30 in Li2CO3, 2 orders of magnitude at about 16 in SiO2, and up to 3 orders of magnitude at about 47 in Li2Si2O5. Additionally, the HOMO-LUMO gap shortens as the SEI layer thickness increases. An estimate of the change in current associated with energy changes using the Heisenberg uncertainty principle yields currents in the range of 10-4 A. Electron transport results provide particular details on the SEI layer formation and growth. A 100% Si cluster yields the largest resistance to electron transport, when compared to the lithiated electrodes modeled by Li13Si4 and LiSi clusters. We also find that Li2CO3 is electrically more insulating than LiF and Li2O. We also find a high electron transfer at the initial stages of SEI formation and then significantly lower transfer yielding a progressively smaller growth of the SEI.
The Journal of Physical Chemistry C
author list (cited authors)
Benitez, L., & Seminario, J. M.
complete list of authors
Benitez, Laura||Seminario, Jorge M