Interactions between Lithium, an Ionic Liquid, and Si(111) Surfaces Studied by X-ray Photoelectron Spectroscopy

Zhen Liu; Guozhu Li; Andriy Borodin; Xiaoxu Liu; Yao Li; Frank Endres

doi:10.1021/acs.jpclett.8b01871

Interactions between Lithium, an Ionic Liquid, and Si(111) Surfaces Studied by X-ray Photoelectron Spectroscopy

J Phys Chem Lett. 2018 Aug 16;9(16):4673-4678. doi: 10.1021/acs.jpclett.8b01871. Epub 2018 Aug 3.

Authors

Zhen Liu¹, Guozhu Li¹, Andriy Borodin¹, Xiaoxu Liu², Yao Li³, Frank Endres¹

Affiliations

¹ Institute of Electrochemistry , Clausthal University of Technology , Arnold-Sommerfeld-Strasse 6 , 38678 Clausthal-Zellerfeld , Germany.
² School of Chemistry and Chemical Engineering , Harbin Institute of Technology , Harbin , China.
³ Center for Composite Materials and Structure , Harbin Institute of Technology , Harbin , China.

PMID: 30067038
DOI: 10.1021/acs.jpclett.8b01871

Abstract

Investigations of the solid-electrolyte interphase formation on a silicon anode are of great interest for future lithium-ion batteries. We have studied the interactions of the ionic liquid 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide ([OMIm]Tf₂N) and of lithium with Si(111) surfaces on a molecular level by X-ray photoelectron spectroscopy. The interaction of Li with [OMIm]Tf₂N on Si(111) results in the decomposition of both the cation and the anion and the intercalation of lithium. Lithium atoms donate the electrons to the [OMIm]⁺ cation, forming Li⁺, and at the same time the alkyl group is detached from the cation. Excessive Li could decompose the imidazolium ring, resulting in C _xH _y and LiC _xH _yN _z species and interact with the Tf₂N^- anions, forming LiF, Li _xO, F₃C-O₂S-N^-Li⁺, and F₃C-O₂S^-Li⁺ species. The formation of a stable Si/IL interface and of Si/Li surface alloys was proved to be an effective strategy in stabilizing Li for next-generation Li-ion batteries.