実験報告書様式（一般利用課題・成果公開利用）（ ※本報告書は英語で記述してください。ただし、産業利用課題として採択されている方は日本語で記述していただいても結構です。 ）MLF	 Experimental Report

提出日 Date of Report

January 9, 2015

課題番号 Project No.

装置責任者 Name of responsible person

2014A0212

Toshiya OTOMO

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Visualization of conduction pathways of lithium ions in NOVA / BL 21
実施日 Date of Experiment
Li2S-GeS2 and Li2S-SiS2 glasses
実験責任者名 Name of principal investigator
November 10-12, 2014
Kazuhiro MORI
所属 Affiliation

Research Reactor Institute, Kyoto University
試料、実験方法、利用の結果得られた主なデータ、考察、結論等を、記述して下さい。（適宜、図表添付のこと）
Please report your samples, experimental method and results, discussion and conclusions. Please add figures andtables for better explanation.
1. 試料 Name of sample(s) and chemical formula, or compositions including physical form.

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(Li2S)40(GeS2)60 glass(Li2S)50(GeS2)50 glass(Li2S)60(GeS2)40 glass(Li2S)40(SiS2)60 glass(Li2S)50(SiS2)50 glass(Li2S)60(SiS2)40 glass

2. 実験方法及び結果 （実験がうまくいかなかった場合、その理由を記述してください。）
Experimental method and results.

If you failed to conduct experiment as planned, please describe reasons.

Li2S−GeS2 and Li2S−SiS2 glasses have attracted much attention as a solid electrolyte inall-solid-state lithium-ion batteries because of their high ionic conductivities at room temperature(10−4 S/cm). In order to understand the conduction mechanism for Li ions in Li2S−GeS2 andLi2S−SiS2 glasses, detailed information on the atomic structure is required. In this work, we
synthesized (7Li2S)x(GeS2)100−x and (7Li2S)x(SiS2)100−x glasses by mechanical alloying (MA) andperformed time-of-flight neutron diffraction (TOF-ND) measurements. Use of the lithium isotope,
7Li, allowed the precise determination of the positions of Li ions in the neutron diffraction analysis
because the absorption cross section, σa, of the 7Li nuclei (0.045 b) is considerably lower than thatof naturally occurring Li nuclei (70.5 b). Reverse Monte Carlo (RMC) modeling has been
conducted to clarify the local structures of the (7Li2S)x(GeS2)100−x and (7Li2S)x(SiS2)100−x glasses,
particularly the atomic positions of the Li ions.

12. 実験方法及び結果（つづき） Experimental method and results (continued)

The (7Li2S)x(GeS2)100−x glasses (x = 40, 50, and 60) and (7Li2S)x(SiS2)100−x (x = 40, 50, and 60)
glasses were synthesized by MA. The electrical conductivities at room temperature, σRT, were
measured using four-probe ac impedance; it was confirmed that σRT increases with increasing Licontent. The TOF-ND analyses were performed using the total scattering spectrometer NOVA at
the BL21 beam line of the Materials and Life Science Experimental Facility (MLF), Japan Proton
Accelerator Research Complex (J-PARC) [1]. The samples were placed in a cylindrical vanadium
holder (6 mm in diameter) under a high-purity argon gas atmosphere. The TOF-ND data werecollected in the Q range of 0.76–23 Å−1 using a 90° detector bank at RT, where Q is the magnitudeof the scattering vector. To obtain the structure factor, S(Q), appropriate corrections related tomultiple scattering, absorption, and incoherent scattering were applied to the TOF-ND data.
We succeeded to collect TOF-ND data for the (7Li2S)x(GeS2)100−x glasses (x = 40, 50, and 60)
and (7Li2S)x(SiS2)100−x (x = 40, 50, and 60) using the NOVA, and then derived the observed S(Q)by the appropriate corrections. For the (7Li2S)x(GeS2)100−x glasses, the radial distribution function(RDF) analysis was performed and the coordination number of S atoms around a Ge atom, NGe–S,
was estimated to be 4 (i.e., GeS4 tetrahedron) regardless of Li content. In the RMC modeling using
the computer program RMC++ [2], excellent fit between the observed and the calculated S(Q) wasobtained for each sample (see Fig. 1). The local structure of the (7Li2S)60(GeS2)40 glass is
illustrated in Fig. 2, which shows a three-dimensional network of corner-sharing GeS4 tetrahedra
together with Li ions. The structural investigations for the (7Li2S)x(SiS2)100−x (x = 40, 50, and 60)
glasses and the visualization of conduction pathways of Li ions in glasses are now in progress [3].
References[1] T. Otomo et al.: KENS REPORT XVIII 2011, KEK Progress Report (2012) 27.
[2] O. Gereben et al.: J. Opt. Adv. Mater. 9 (2007) 3021.
[3] K. Mori et al.: Chem. Phys. Lett. 584 (2013) 113.

Fig. 1. RMC modeling of (7Li2S)60(GeS2)40
glass using TOF-ND and synchrotron X-ray
diffraction (SXRD) data at room temperature.

Fig. 2. The local structure of (7Li2S)60(GeS2)40
glass obtained from the RMC modeling. The grayline indicates the cubic RMC unit with 4.5-nm-longedge.

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