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

課題番号 Project No.

装置責任者 Name of responsible person

2014A0291

Prof. Yasuhiro Miyake

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Observation of the inside of a lithium-ion battery by muonic x-ray

D2

実験責任者名 Name of principal investigator

実施日 Date of Experiment

Izumi Umegaki

2014/5/6-2014/5/9

所属 Affiliation
Toyota Central Research & Development Labs., Inc.
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.
Components of lithium-ion battery;
Li(Ni0.85Co0.15)O2, as a cathode material
Graphite, as an anode material
Al sheets
Cu sheets
Polymer separator

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.

This experiment is an ambitious challenge to apply an elemental analysis technique with muonic
x-ray to a non-destructive compositional analysis for light elements, such as, Li, C, F, and O in
multi-layers samples like commercial batteries. We have initiated to measure a depth profile of several
elements in the cathode and anode sheets of a Li-ion battery with this technique.
【Method】
Negative mions （-）are implanted into samples and the implanted - is trapped by a nearby
element, resulting in the formation of a muonic shell structure like an electronic shell structure. Then,the trapped - transits from a higher energy level to a lower one with emitted x-ray, whose energy
corresponds to the difference in the energy between the levels. Such x-ray is usually called as amuonic x-ray. The transition occurs several times until the - reaches down to the lowest energy
level, i.e. the K-shell. Note that the muonic x-ray is easily detected by a Ge semiconductor detector,
because the energy of the muonic x-ray is about 200 times larger than that of the x-ray fluorescence.
In order to restrain the decrease of the intensity 1of x-ray, we used a sample chamber evacuatedwith turbomolecular pump during our experiments. Six Ge detectors wereset very close to windows of the sample chamber so that large solid angle can be covered. The penetration

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

In order to suppress the decrease in the intensity of the muonic x-ray, the sample was set in theAl chamber, which is evacuated with a turbo-molecular pump during the experiment. Since the Alchamber equips six windows, we used six Ge detectors. Each Ge detector was arranged close toeach window to cover a large solid angle. The range of the - in the sample was adjusted by changing
the implantation momentum (p) of -.
【Experimental results】
At first, we prepared a LiF crystal, which is sandwichedby two Al foils. As seen in Fig.1, we have successfully observeda Li-Ksignal at 18.70 keV, which has been never detectedby an x-ray fluorescent analysis. This is, to our knowledge,
the first report to detect the Li-Ksignal.
Then, we measured the multi-layer sample consistingof an anode sheet, separator, a cathode sheet, and Al foils.
Figure 2 shows an energy profile of the muonic x-ray mainly
from the cathode. Since the cathode contains 5wt% carbon
as a conductive additive, the profile includes the signals not

Figure 1 : Energy profile obtained

only from Li and Al but also C. Such C is found to inducefor LiF crystal.

difficulty to detect the Li signal, because the C-L signal also
locates at 18.83 keV, which is higher only by 130 meVThan the energy of the Li-KThe energy resolution of thepresent Ge semiconductor detector is 400 meV and too large
to separate into two signals. In order to obtain information on
the distribution of Li in the cathode and other components, weplan to use the detector with a higher energy resolution, suchas a SDD or CdTe detector.
It is also found that the depth distribution of the implanted
- becomes broader with increasing p. When we usep=15.7(21.2)MeV/c, - stops the region from the surface
with 120±20 (300±60)m depth. Furthermore, since thedeviation of the selected pis not zero but ±5%, such

Figure 2 : Energy profile for thecathode,which

consists

cathodematerials

andofAlcurrent collector.

distribution of p further extends the depth distribution of -. In order to analyze the composition
as a function of depth, it is highly desirable to obtain “monochromatic negative muon beam”.

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