title: Evaluating the solid electrolyte interphase formed on silicon electrodes: a comparison of ex situ X-ray photoelectron spectroscopy and in situ neutron reflectometry.
abstract: This work details the in situ characterization of the interface between a silicon electrode and an electrolyte using a linear fluorinated solvent molecule, 0.1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in deuterated dimethyl perfluoroglutarate (d6-PF5M2) (1.87 × 10(-2) mS cm(-1)). The solid electrolyte interphase (SEI) composition and thickness determined via in situ neutron reflectometry (NR) and ex situ X-ray photoelectron spectroscopy (XPS) were compared. The data show that SEI expansion and contraction (breathing) during electrochemical cycling were observed via both techniques; however, ex situ XPS suggests that the SEI thickness increases during Si lithiation and decreases during delithiation, while in situ NR suggests the opposite. The most likely cause of this discrepancy is the selective removal of SEI components (top 20 nm of the SEI) during the electrode rinse process, which is required to remove the electrolyte residue prior to ex situ analysis, demonstrating the necessity of performing SEI characterization in situ.
authors.affiliation: Department of Chemistry, Missouri University of Science and Technology, 400 W. 11th St., Rolla, MO 65409, USA. fears1@llnl.gov.
authors.forename: T M
authors.initials: TM
authors.lastname: Fears
authors.affiliation: Neutron Data Analysis and Visualization Division, Oak Ridge National Laboratory, 1 Bethel Valley Rd., Oak Ridge, TN 37831, USA. doucetm@ornl.gov.
authors.forename: M
authors.initials: M
authors.lastname: Doucet
authors.affiliation: Chemical and Engineering Materials Division, Oak Ridge National Laboratory, 1 Bethel Valley Rd., Oak Ridge, TN 37831, USA. browningjf@ornl.gov.
authors.forename: J F
authors.initials: JF
authors.lastname: Browning
authors.affiliation: Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
authors.forename: J K S
authors.initials: JK
authors.lastname: Baldwin
authors.affiliation: Department of Chemistry, Missouri University of Science and Technology, 400 W. 11th St., Rolla, MO 65409, USA. fears1@llnl.gov.
authors.forename: J G
authors.initials: JG
authors.lastname: Winiarz
authors.affiliation: University of Missouri Research Reactor, University of Missouri, 1513 Research Park Dr., Columbia, MO 65211, USA.
authors.forename: H
authors.initials: H
authors.lastname: Kaiser
authors.affiliation: Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA.
authors.forename: H
authors.initials: H
authors.lastname: Taub
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, 1 Bethel Valley Rd., Oak Ridge, TN 37831, USA. veithgm@ornl.gov.
authors.forename: R L
authors.initials: RL
authors.lastname: Sacci
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, 1 Bethel Valley Rd., Oak Ridge, TN 37831, USA. veithgm@ornl.gov.
authors.forename: G M
authors.initials: GM
authors.lastname: Veith