Lithiation behavior of silicon-rich oxide (SiO1/3): A first-principles study

Chia Yun Chou, Gyeong S. Hwang

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Abstract

Silicon suboxides (SiOx, x < 2) have been recognized as a promising anode material for high-performance Li-ion batteries (LIBs), especially when the O content is relatively low. To better understand the lithiation behavior in partially oxidized silicon at the atomistic level, we perform density functional theory calculations to examine the structural evolution, bonding mechanism, mechanical property, and voltage profile of lithiated a-SiO1/3. With lithiation, the a-SiO1/3 host matrix gradually disintegrates as Li atoms are accommodated by both Si and O atoms. Interestingly, we find that the Si-Li coordination number (CN) monotonically increases up to CNSi-Li ≈ 10 in a-Li 4SiO1/3, whereas CNO-Li tends to saturate far before full lithiation at CNO-Li ≈ 6; the formation mechanism of such intriguing Li6O complexes with Oh symmetry is investigated via detailed electronic structure analyses. Li incorporation in the a-SiO1/3 matrix is predicted to be highly favorable with a capacity comparable to that of fully lithiated Si (Li:Si ratio ≈ 4); additionally, the approximated lithiation voltage between 0.2 and 0.8 V is also well within the desirable range for LIB anode applications. Our study highlights the importance of controlling the Si:O ratio as well as O spatial distribution in order to tailor the desired lithiation properties; such a realization may benefit the rational design and development of high-performance silicon suboxide based anodes via fine-tuning of the oxidation conditions.

Original languageEnglish
Pages (from-to)3435-3440
Number of pages6
JournalChemistry of Materials
Volume25
Issue number17
DOIs
StatePublished - 10 Sep 2013

Keywords

  • density functional theory
  • LiO polycation
  • LIB anode
  • lithiation
  • silicon suboxide

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