実験報告書様式（一般利用課題・成果公開利用）

MLF Experimental Report

提出日 Date of Report
2014, 10/10

課題番号 Project No.

装置責任者 Name of responsible person

2012A0108

Norifumi Yamada

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）In situ neutron reflectometry analysis of electrode / electrolyte

BL16interface for lithium batteries

実施日 Date of Experiment

実験責任者名 Name of principal investigator2012/10/26-29

Ryoji Kanno
所属 Affiliation
Tokyo institute of technology
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.

Epitaxial Li4Ti5O12 (111) thin films were synthesized on SrTiO3 (111) substrate by a pulsed laser
deposition (PLD) method using a KrF excimer laser (248 nm) and Li5.2TiO12 target. Crystal
orientation, thickness, density and roughness were evaluated by X-ray diffraction and reflectivity
measurements. On the top of the Li4Ti5O12 epitaxial film, a solid electrolyte of Li3PO4 was
deposited by the PLD method. Thicknesses of the Li4Ti5O12 epitaxial film and Li3PO4 layer wereabout 24 and 5 nm, respectively. Structures of the Li3PO4/Li4Ti5O12 and Li4Ti5O12 film electrodes
were investigated by neutron reflectometry analysis.

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.

An in situ spectro-electrochemical cell was used for the neutron reflectivity measurements.
Deuterated propylene carbonate (PC), which contains 1M LiPF6 and lithium metal were used as
the electrolyte and the counter electrode, respectively. De-intercalation and intercalation wereperformed by the potentiostatic method with a potentiostat/galvanostat (Ivium Tech., Compactstat).
Structural changes were observed by the potentiostatic method during electrochemical(de)intercalation. Reflectivity spectra of the thin film electrodes were measured as a function of
the momentum transfer, Qz = (4πsinθ)/λ, in the Qz range of 0.01 to 0.14 Å−1. The Parratt32
program that uses Parratt’s method was used for reflectivity data analysis. Figure 1 (a) shows
neutron reflectivity spectrum of the Li3PO4/Li4Ti5O12 and Li4Ti5O12 epitaxial films on SrTiO3 (111)at as-deposited state.

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

Three-layer and two-layer models of Li3PO4/Li4Ti5O12/SrTiO3 and Li4Ti5O12/SrTiO3 provided
best fitting of the reflectivity spectra. Figure 1 (b) illustrates the scattering length density (SLD)
profiles from the analysis results for both film electrodes. The Li3PO4 film stacking increased theSLD of the Li4Ti5O12 region. The scattering length density  was 2.42 x 10-6 Å-2, which is related
to the film density d with the following equation.

where M is the molecular weight, b overall scattering length in the unit cell, and NA the Avogadro’s
number. Therefore, the Li3PO4 stacking changed the density of the Li4Ti5O12. As natural
lithium has a negative coherent scattering length ( 1.9 fm for 7Li:6Li = 92.5:7.5), the increase in
the SLD indicates a lithium deficient phase formation, which could be described as Li4-xTi5O12.
Structural information at the as-deposited states is an important indicator for further structuralanalysis. Based on the obtained results, in situ structural analysis during the charge-discharge
process will be demonstrated.

Figure 1 Neutron reflectometry spectra with fitting curves (a) and the SLD profiles calculatedusing analysis results (b) for the Li3PO4/Li4Ti5O12 and Li4Ti5O12 thin film electrodes.

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