Lithiation of silica through partial reduction

CM Ban and BB Kappes and Q Xu and C Engtrakul and CV Ciobanu and AC Dillon and YF Zhao, APPLIED PHYSICS LETTERS, 100, 243905 (2012).

DOI: 10.1063/1.4729743

We demonstrate the reversible lithiation of SiO2 up to 2/3 Li per Si, and propose a mechanism for it based on molecular dynamics and density functional theory simulations. Our calculations show that neither interstitial Li (no reduction), nor the formation of Li2O clusters and Si-Si bonds (full reduction) are energetically favorable. Rather, two Li effectively break a Si-O bond and become stabilized by oxygen, thus partially reducing the SiO2 anode: this leads to increased anode capacity when the reduction occurs at the Si/SiO2 interface. The resulting LixSiO2 (x < 2/3) compounds have band-gaps in the range of 2.0-3.4 eV. (C) 2012 American Institute of Physics.

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