実験報告書様式（一般利用課題・成果公開利用）

MLF	 Experimental Report
課題番号 Project No. 2010A0041

提出日 Date of Report
December 20, 2010
装置責任者 Name of responsible person
Yasuhiro Miyake

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Lithium diffusion in LiFePO4 and related materials

D1

実験責任者名 Name of principal investigator

実施日 Date of Experiment

Jun Sugiyama

December 16, 2010 ‒ December 18, 2010

所属 Affiliation
Toyota Central Research and Development Laboratories, 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.

A powder sample of lithium nickel phosphate, LiNiPO4, was synthesized at Tokyo Institute ofTechnology by a solid state reaction technique. The powder was, then, pressed into a disc with 27mm diameter and 1 mm thickness, and finally the disc was packed in an Au-sealed titanium cell.

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.

The phospho-olivines have numerous advantages over the layered rock salt oxides (e.g. LiCoO2and LiNiO2) that are currently used in commercial batteries. Besides its high capacity (ca. 170
mAh/g), LiMPO4 cathode material shows high stability during lithium extraction/insertion anddoes not deteriorate when used at moderately high temperatures [1]. According to µSR
measurements at low temperatures in TRIUMF to elucidate the magnetic nature of LiMPO4 with
M=Mn, Fe, Co, Ni, all the four olivines were found to enter into a static AF ordered state below
around 50 K. Furthermore, even in the paramagnetic state, the ZF-spectrum for the M=Mn, Fe, andCo olivens exhibits a fast relaxing behavior due to fluctuating magnetic moments of the M ions,although the ZF-spectrum for LiNiPO4 shows a Kubo-Toyabe behavior due to nuclear magneticfields.
We have, therefore, measured wTF-, ZF- and LF-spectra for LiNiPO4 in the temperature range
between 50 and 500 K in order to know a diffusive behavior at high temperatures. The obtainedspectrum was fitted using a combination of a dynamic Gaussian Kubo-Toyabe signal and an offset
background signal; A0P(t)=AKTGKT(Δ, ν, t, HLF) +ABG. Here, we used a global fitting technique tofit all the spectra using common parameters, i.e., two asymmetries, AKT and ABG. Such fit provided
AKT =0.1629±0.0007 and ABG= 0.0331±0.0007.
1

2. 実 験 方 法 及 び 結 果 （ つ づ き ） Experimental
method and results (continued)

Figure 1 shows the T variation of ZF- andLF-spectra for LiNiPO4 at 100 K, 275 K, and450 K. The applied LF was 5 Oe. At 100 K,
the ZF spectrum shows a minimum around 9µs, indicating the presence of a small random
nuclear field (Hintn). Moreover, the applied LF
clearly decouples the effect of Hintn. Since thewhole signal from the sample is well fitted bya dynamic Kubo-Toyabe function, the originof the muon-spin depolarization is assigned asa nuclear magnetic field caused by Li and P.
The ZF-spectrum at 275 K, on the otherhand, relaxes monotonically until at least 18µs. Additionally, the effect of LF is verysmall. This suggests the increase influctuation of Hintn. However, at 450 K, theZF-spectrum exhibits a minimum again
around 17 µs and the LF-spectrum shows adecoupling behavior, meaning a static natureof Hintn.
Figure 2 shows the T dependences of Δ and νfor LiNiPO4. As T increases from 50 K, Δ isalmost T-independent up to 200 K, anddecreases linearly until 300 K, and thenincreases slowly with T. The ν(T) curveshows a sharp maximum around 290 K. ν ismost likely to increase with T above 350 K.
This behavior is unlikely explained by Li
diffusion, which would start to occur above
200 K. In order to clarify the change in muonsites with T, it is preferable to investigate asmall structural variation below 300 K,
although LiNiPO4 is reported to keep its
orthorhombic symmetry down to the lowest T
measured [2].

Fig. 1 T variation of the ZF- and LF-spectra for
LiNiPO4 at (a) 100 K, (b) 275 K, and (c) 450 K.

Fig. 2 T dependences of Δ (black square) andν (red circle) for LiNiPO4.

[1] C. M. Julien et al., Ionics 12, 21 (2006),
and references cited therein.
[2] T. B. S. Jensen et al., Phys. Rev. B 79, 092412 (2009).
2