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。 ）提出日 Date of Report

MLF Experimental Report

2013/4/4

課題番号 Project No.

装置責任者 Name of responsible person

2012B0029

Toru Ishigaki

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Composition dependence of crystal structure of vacuum-reduced

iMATERIA/BL20

Li2MnO3-Li(Mn,Co,Ni)O2

実施日 Date of Experiment

systeminelectrochemicalcharge/discharge process

2012/11/28~30

実験責任者名 Name of principal investigator

2013/01/16~18

Yasushi Idemoto
所属 Affiliation
Tokyo University of Science
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.
Compositions: zLi2MnO3-(1-z)Li(Mn1/3Co1/3Ni1/3)O2 (reduced; charged, discharged)
zLi2MnO3-(1-z)Li(Mn5/12Co1/6Ni5/12)O2 (reduced;charged, discharged)

Physical form: Powder or film

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.

Experimental method
Lithium-rich layered cathode active materials were synthesized by a coprecipitation method. In thisprocess, the final heating was carried out at 950 oC in air regardless of the metal composition. As for thesynthesized samples, a heat-treatment under vacuum condition (P=10-4 Pa) at 800 oC was carried out. Phases ofthe obtained samples were identified by powder X-ray diffraction measurements, and their metal compositionsand the metal valences were evaluated by the inductively coupled plasma emission and redox titration analyses.
In order to clarify the composition dependence of the vacuum-reducing effects on the crystal structures atelectrochemically charged and discharged states, cathodes after charge-discharge cycling were prepared.
As for these cathodes, neutron diffraction patterns were measured by iMATERIA installed at J-PARC.
Each cathode(10mg) was loaded in a vanadium can, and then mounted in a sample holder. The measurements
were carried out at room temperature with a SF mode. Crystal structures of the samples were refined by theRietveld technique using a Z-Rietveld program.
1

2. 実験方法及び結果（つづき） Experimental method and results (continued)
Results
Fig. 1 shows Rietveld refinement pattern of vacuum-reduced 0.5Li2MnO3-0.5LiMn5/12Co1/6Ni5/12O 2 after
an initial charging process (BS bank). In these analyses, the transition-metal occupancies were refined so that thecompositions were equal to the analytical values estimated by ICP. The result given in Fig. 1 indicated that thesample kept a Li2MnO3-type structure (S. G.: C2/m) even after electrochemical tests. In addition, it was foundthat a c-axis length became longer and the others became shorter by the charging process in the reduced samples.
Such a tendency was also observed in the samples without the reducing treatment.
Table 1 lists distortion parameters of metal-O6 octahedra and the bond valence sums (B. V. S.) ofvacuum-reduced 0.5Li2MnO3-0.5LiMn5/12Co1/6Ni 5/12O2 after the initial charging. This table also presents thedistortion values of the pristine sample, i. e., the sample without the reducing treatment. In the reduced sample,
thedistortions

weresmaller

thanthepristinespecimen.

Since

acycleperformanceof0.5Li2MnO3-0.5LiMn5/12Co1/6Ni5/12O2 cathode was improved by the vacuum-reducing heat-treatment, the lower
distortions at the charged state can be considered as an important factor to enhance the cathode performance.

-3

Normalized Intensity

30x1020100-10

0.5

1.0

1.5

2.0

2.5

d-spacing / ÅFig. 1 Neutron diffraction pattern of vacuum-reduced 0.5Li2MnO3-0.5LiMn5/12Co1/6Ni5/12O2(cathode:10mg) after
an initial charging process. Plus marks show observed neutron diffraction intensities, and a solid blue line
represents calculated intensities. Vertical marks below them indicate positions of allowed Bragg refractions. A
curve at the bottom is a difference between the observed and calculated intensities in the same scale.
Table 1 Quadratic elongations, , bond angle variances, 2, of metal-O6 octahedra and B. V. S. in thetransition-metal layer of 0.5Li2MnO3-0.5LiMn5/12Co1/6Ni5/12O2 after an initial charging.
SamplePristine
Vacuumreduction

4g-O62b-O622

2σ (deg. )B. V. S.

λσ (deg.2)

B. V. S.

1.012

37.68

3.764

1.019

59.93

2.142

1.011

34.19

4.051

1.019

57.86

1.7722