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
2010/8/6

課題番号 Project No.

装置責任者 Name of responsible person

2009B0016

石垣 徹

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Structural analyses of new LiCoO2 for lithium-ion batteries

iMATERIA/BL20

実験責任者名 Name of principal investigator

実施日 Date of Experiment

駒場慎一

2010/5/14～2010/5/15

所属 Affiliation
東京理科大学
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.
Li0.9CoO2
Li0.5CoO2
Li0.37Na0.31CoO2

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.

Layered LiCoO2 is used as positive electrode materials for commercial lithium-ion batteries.

Two different

polymorphs of LiCoO2, thermodynamically stable O3-type and meta-stable O2-type LiCoO2, are known so far.
Very recently we have found that possible new polymorph of LiCoO2, which has been prepared from OP4-type
LixNayCoO2（x < 0.5, y < 0.5）.

For OP4-type LixNayCoO2, sodium and lithium ions occupy prismatic sites andoctahedral sites, respectively, which are stacked alternately along c-axis.

In this research proposal, we haveexamined the ion-exchanged product of OP4-type LixNayCoO2, and its reaction mechanism has been studied by
ToF neutron diffraction method.

When the sodium ions are exchange by the lithium ions, we found that

CoO2-Li-CoO2 slabs glide by (2/3, 1/3, 0) because of the difference in the ionic radii and / or distance in theinter-slabs (Figure 1).

Detailed structural analysis reveals that this phase can be classified as O4-type LiCoO2,

which is new polymorph of LiCoO2.

It is noted that profiles of all diffraction lines are broadened, except(00l)hex. and (110)hex. lines, suggesting that stacking fault exists for O4-type LiCoO2.

To examine the reaction

mechanism of O4-type LiCoO2, Li0.5CoO2 has been prepared by the electrochemical extraction of the lithiumions and examined by the neutron diffraction.
12. 実験方法及び結果（つづき） Experimental method and results (continued)
Figure 2 compares neutron diffraction patters of O4-LiCoO2 and Li0.5CoO2.

Lithium ions were extracted in

the electrochemical cells, in which the composite electrodes consisting of LiCoO2, acetylene black, and PVdF as
binder were utilized.

Lithium metal was used as a negative electrode, and 1 mol dm-3 LiPF6 dissolved in EC：

DMC = 1：1 was used as electrolyte solution. After the lithium extraction process, two new diffraction linesappear beside the (110)hex. diffraction line.

In order to explain the experimental observation, possible models,

which have different stacking sequences, were tested. Figure 3 shows simulated neutron diffraction patterns of
O4 and OT#4-type models.
sites.

For the OT#4-type model, half of lithium ions are located at distorted tetrahedral

This is achieved by the gliding of the plane with (1/3, 1/6, 0) as shown in Figure 4 if no stacking fault isassumed.
Since the OT#4 model generates the additional diffraction lines, which are consistent with the observed
diffraction patterns, we conclude that O4-type LiCoO2 changes to the OT#4-type by the lithium extraction.
addition, this phase transition reversibly occurs.

InO4-type LiCoO2 was confirmed after the discharging process(lithium insertion to the lattice).

(013)hex.

35000

30000

25000

20000

35000

15000

30000

Intensity / A.U.

25000

20000

15000

TOF / μs
ToF Neutron diffraction patterns

Figure 2.

of O4-Li0.9CoO2and Li0.5CoO2.

OP4-Li0.37Na0.31CoO2 and O4-Li0.9CoO2.

OT#4-typeO4-type(110)hex.

(013)hex.

Face(015)hex.

(004)hex.

(114)hex.

hex.

ToF Neutron diffraction patterns of

O4: a=2.82Å, c=18.90Å
OT#4: a=2.80Å, c=19.44Å

a = 2.8116 Å(013)hex. (015) c = 18.9557(1) Å

TOF / μs

Figure 1.

a = 2.8085 Åc = 19.46299(3) Å

Li0.9CoO2

O4-Li0.9CoO2(015)hex.

(110)hex.

Li0.5CoO2

Intensity / A.U.

Intensity / A.U.

(110)hex.

OP4-Li0.37Na0.31CoO2

Edge
Edge

(a)

O4構造

Edge
Edge

Edge
FaceEdge(0111)hex.
(113)hex.

(b)

Edge
Edge

bOT#4構造a●●●10EdgeEdge

203040506070●
●

●

●

●

●
●(1/3,1/6,0)●● ● ● ● ●● ● ● ● ●●●●2θ/ deg.(λ=1.54Å)

Figure 3. Simulated neutron diffraction patterns

Figure 4. Proposed model of the phase transition#from O4-LiCoO2 to OT#4-LizCoO2.

of (a) O4-LiCoO2 and (b) OT 4-LiCoO2.

2